LAKE JESUP NUTRIENT REDUCTION FACILITY SOLDIERS CREEK RSF AT COUNTY ROAD 427. SJRWMD ERP Submittal Supporting Documentation April 2013

Transcription

1 LAKE JESUP NUTRIENT REDUCTION FACILITY SOLDIERS CREEK RSF AT COUNTY ROAD 427 SJRWMD ERP Submittal Supporting Documentation April 2013 Prepared For: Seminole County, Florida Prepared By: Pegasus Engineering, LLC Greg A. Teague, P.E., CFM 301 West State Road 434, Suite 309 Winter Springs, FL Phone: Environmental Research and Design, Inc. Harvey H. Harper, III, Ph.D., P.E Trentwood Blvd., Suite 102 Belle Isle (Orlando), FL Phone:

2 TABLE OF CONTENTS Section/Description LIST OF FIGURES LIST OF TABLES Page LF-1 LT-1 1. INTRODUCTION Background Conceptual Treatment System Overview Work Efforts Conducted by ERD FIELD AND LABORATORY ACTIVITIES Field Monitoring Monitoring Site Discharge Measurements Surface Water Monitoring Laboratory Activities Jar Testing Laboratory Methods RESULTS Field Measurements Discharge Physical-Chemical Parameters Laboratory Analyses Raw Water Characteristics Laboratory Jar Testing General Jar Test Characteristics Jar Test Results Removal Efficiencies Floc Production 3-25 TOC-1

3 TABLE OF CONTENTS -- CONTINUED Section/Description Page 4. EVALUATION OF NONPOINT SOURCE LOADINGS IN THE SOLDIERS CREEK DRAINAGE BASIN Characteristics of the Soldiers Creek Basin General Characteristics Land Use Soil Types Stormwater Management Sewage Disposal Hydrologic Characteristics NPSLM Model Organization General Input Data Rainfall Frequency Distribution Stormwater Management Conveyance Attenuation Stormwater Characteristics Groundwater Seepage Runoff Volume Calculation Module Runoff Volume Attenuation Module Pollutant Load Generation Nonpoint Source Loading Estimates Runoff Loadings Baseflow Loadings Combined Loadings CONCEPTUAL TREATMENT SYSTEM DESIGN AND CHARACTERISTICS Conceptual System Design Evaluation of Treatable Discharge Phosphorus Load Reductions Anticipated Chemical Use Annual Floc Production and Disposal Operation and Maintenance Weekly Maintenance Quarterly Maintenance Impacts of Pond Modifications on Existing Treatment Efficiency 5-10 TOC-2

4 TABLE OF CONTENTS -- CONTINUED Appendices A. Results of Laboratory Jar Tests on Soldiers Creek Samples Collected from January- March 2013 B. General Characteristics of Delineated Sub-basin Areas in the Soldiers Creek Basin C. NPSLM Model Summary Sheets for the Soldiers Creek Basin TOC-3

5 LIST OF FIGURES Description Page 1-1 Location Map for Lake Jesup Lake Jesup Watershed and Sub-basin Areas Overview of Drainage Patterns in the Soldiers Creek Sub-basin Area Schematic of Proposed Stormwater Treatment System Location of the Soldiers Creek Monitoring Site Photograph of the Soldiers Creek Monitoring Site Typical Flow Monitoring Activities Laboratory Jar Test Apparatus Comparison of Measured Discharge Rates at the Soldiers Creek Monitoring Site Variability in Flow Characteristics at the Soldiers Creek Site During the Field Monitoring Program Comparative Locations of the Proposed Treatment System Site and the USGS Gauging Station Along Soldiers Creek Comparison of Measured Soldiers Creek Discharge Rates at the Project Site and USGS Gauging Station Over the Period from July-October Relationship Between Field Measured Discharge Rates at the Proposed Project Site with Mean Daily Discharges at the USGS Gauging Site Summary of Rainfall and Discharge in Soldiers Creek During the Field Monitoring Program from August-October Trends in Field Measured Values of ph, Conductivity, Dissolved Oxygen, and Turbidity in Soldiers Creek from July-October Summary of Measured Concentrations of ph, Alkalinity, Conductivity, Turbidity, Color, and Dissolved Aluminum in Soldiers Creek Samples During the Periods of July-October 2010 and January-March LF-1

6 LIST OF FIGURES CONTINUED Description Page 3-9 Summary of Measured Concentrations of Nitrogen Species in Soldiers Creek Samples During the Periods of July-October 2010 and January-March Summary of Measured Concentrations of Phosphorus Species in Soldiers Creek Samples During the Periods of July-October 2010 and January-March Temporal Variability in Nitrogen Species in Soldiers Creek Samples During the Periods of July-October 2010 and January-March Temporal Variability in Phosphorus Species in Soldiers Creek Samples from July-October 2010 and January-March Changes in ph, Alkalinity, Conductivity, and Turbidity in PACl Treated Samples Collected from Soldiers Creek Changes in Turbidity and TSS in PACl Treated Samples Collected from Soldiers Creek Changes in Nitrogen Species in PACl Treated Samples Collected from Soldiers Creek Changes in Phosphorus Species in PACl Treated Samples Collected from Soldiers Creek Overview of the Soldiers Creek Basin Sub-basin ID Numbers and Significant Conveyance Pathways for Soldiers Creek Land Use in the Soldiers Creek Basin Hydrologic Soil Groups in the Soldiers Creek Drainage Basin Overview of Drainage Basin Areas Treated by Stormwater Management Systems in the Soldiers Creek Drainage Basin Locations of Septic Tank Systems in the Soldiers Creek Drainage Basin Flow Diagram of the NPSLM Model Nodal Diagram for Hydrologic Discharges in the Soldiers Creek Basin Nodal Diagram for Phosphorus Discharges in the Soldiers Creek Basin 4-25 LF-2

7 LIST OF FIGURES CONTINUED Description Page 5-1 Proposed Conceptual Design for the Soldiers Creek Treatment System Probability Distributions for Discharge Measurements in Soldiers Creek from Cross-sectional Schematic of the Proposed Floc Collection Trough 5-7 LF-3

8 LIST OF TABLES Description Page 1-1 Estimated Annual Surface Runoff into Lake Jesup from Estimated Annual Total Phosphorus Loading into Lake Jesup from Analytical Methods and Detection Limits for Laboratory Analyses Conducted on Jar Test Samples Field Measured Discharge Rates in Soldiers Creek from July-October Physical-Chemical Field Measurements Collected in Soldiers Creek from July- October Characteristics of Soldiers Creek Samples Collected from July-October 2010 And from January-March Characteristics of Laboratory Jar Tests Conducted on Soldiers Creek Samples Collected from January-March Mean Characteristics of Jar Tests Conducted on Soldiers Creek Samples from January-March Mean Removal Efficiencies for Jar Tests Conducted on Soldiers Creek Samples from January-March Calculated Floc Generation Rates for PACl Treated Soldiers Creek Water General Land Use Categories and Corresponding Level III Classifications Land Use in the Soldiers Creek Drainage Basin Characteristics of SCS Hydrologic Soil Group Classifications Hydrologic Soil Groups in the Soldiers Creek Drainage Basin Hydrologic Characteristics of Identified Land Use Types in the Soldiers Creek Drainage Basin Rainfall Frequency Distribution for the Soldiers Creek Model 4-15 LT-1

9 LIST OF TABLES CONTINUED Description Page 4-7 Assumed Annual Factors for Typical Stormwater Management Systems Assumed Conveyance System Losses for the Soldiers Creek Drainage Basin Typical Stormwater Runoff Concentrations for Various Land Uses Typical Seepage Characteristics for Waterbodies in Florida Summary of Runoff Volumes and Annual C Value for Runoff Inputs to the Proposed Treatment Pond Summary of Hydrologic Measurements at the Soldiers Creek USGS Gauging Station (No ) Estimated Hydrologic Mass Loadings in Baseflow from the Soldiers Creek Sub-basin Areas Summary of Runoff and Baseflow Discharges from the Soldiers Creek and Southern Sub-basin Areas to the Proposed Treatment Site Summary of Annual Mass Loadings of Total Phosphorus from Runoff and Baseflow at the Proposed Treatment System Site Relationships Between Treated Discharge Rates and Annual Treated Volumes for Soldiers Creek Calculated Annual Phosphorus Load Reductions by the Soldiers Creek Treatment System Summary of Anticipated Chemical Use for the Proposed Soldiers Creek Treatment System Summary of Anticipated Floc Production for the Proposed Soldiers Creek Treatment System Weekly Treatment System Checklist Comparison of Pond Characteristics Under Existing and Proposed Conditions Comparison of Calculated Pond Removal Efficiencies Under Existing and Proposed Conditions Comparison of Pond Mass Removals Under Existing and Proposed Conditions 5-12 LT-2

10 SECTION 1 INTRODUCTION This document provides a summary of field and laboratory monitoring and engineering analyses conducted by Environmental Research & Design, Inc. (ERD) and Pegasus Engineering (Pegasus) for Seminole County (County) in support of the proposed alum treatment system to provide load reductions for discharges through Soldiers Creek into Lake Jesup. 1.1 Background Lake Jesup is a 10,660-acre shallow, hypereutrophic lake located in northern-central Seminole County. A general location map for Lake Jesup is given on Figure 1-1. The lake is currently included on the Verified List, developed by the Florida Department of Environmental Protection (FDEP), as impaired for nutrients and unionized ammonia. Lake Jesup (WBID 2981) is also a priority waterbody as part of the State of Florida s Surface Water Improvement and Management (SWIM) Program. Lake Jesup is hydraulically connected to the St. Johns River at the northern end by a narrow outlet channel near the SR 46 bridge and causeway. The SR 417 bridge, completed in 1993, crosses the lake near the western end. A small island, commonly referred to as Bird Island, is located near the center of the lake. Lake Jesup is an extremely shallow waterbody with a mean depth ranging from approximately 3-4 ft, depending upon water elevation. The average water stage in Lake Jesup is approximately ft (NGVD). In general, net water movement occurs from Lake Jesup into the St. Johns River, although flow reversal occurs periodically during periods of differential rainfall in adjacent sub-basin areas. The mean hydraulic residence time for Lake Jesup has been estimated from days, depending upon the source. The drainage basin for Lake Jesup covers an area of approximately 87,331 acres. An overview of the Lake Jesup watershed and sub-basin areas is given on Figure 1-2. The vast majority of the watershed is located within Seminole County, with a small portion of the southwest end extending into Orange County. The watershed area encompasses 11 separate municipalities, including Sanford, Lake Mary, Oviedo, Winter Springs, Longwood, Casselberry, Altamonte Springs, Maitland, Winter Park, Eatonville, and Orlando. Large portions of the watershed are highly urbanized, consisting of a combination of residential, commercial, and transportation land uses. 1-1

11 1-2 Figure 1-1. Location Map for Lake Jesup.

12 SR 1-3 SR 46 µ CR 4220 Lake Jesup SR 434 SR 419 SR 400 SR 15 SR 414 SR 436 Seminole Co. SR 423 SR 426 Orange Co. SR 417 SR 50 Legend Roads SR 500 SR 408 STREAM County Boundaries Lakes Drainage Basins GEE CREEK HOWELL CREEK LAKE JESUP CR 423 SOLDIER CREEK 527 Miles Figure 1-2. Lake Jesup Watershed and Sub-basin Areas. (SOURCE: Final FDEP TMDL Report, 2006)

13 1-4 As indicated on Figure 1-2, there are a number of tributaries, canals, and small streams which discharge loadings to Lake Jesup. The most significant of these tributaries, in terms of both surface area and annual inflow volume, are Howell Creek, Gee Creek, and Soldiers Creek. A summary of estimated annual surface runoff into Lake Jesup over the period from is given in Table 1-1, based upon information provided in the FDEP Final TMDL Report (2006). Estimates are provided for the Gee Creek Basin, Howell Creek Basin, Soldiers Creek Basin, and Little Lake Howell Basin. All of the remaining inflows are grouped together into a single basin referred to as Lake Jesup sub-basin. Over the period from , approximately 45% of the annual surface runoff originated from the Lake Jesup sub-basin areas, with 34% originating within the Howell Creek basin, 11% in the Soldiers Creek basin, and 8% in the Gee Creek basin. TABLE 1-1 ESTIMATED ANNUAL SURFACE RUNOFF INTO LAKE JESUP FROM (Source: FDEP Final TMDL Report, 2006) SUB-BASIN YEAR (ac-ft/yr) MEAN PERCENT (%) Gee Creek 5,153 7,473 4,937 5,472 3,789 2,821 5,716 8,052 5,426 8 Howell Creek 22,602 32,478 21,530 23,812 16,570 12,376 24,945 34,912 23, Lake Jesup 30,898 42,140 29,089 31,293 22,753 15,514 32,897 46,061 31, Little Lake Howell 1,895 2,697 1,798 1,983 1,391 1,027 2,077 2,899 1,971 3 Soldiers Creek 7,390 10,467 7,044 7,709 5,447 3,879 8,063 11,370 7, Total 67,938 95,254 64,396 70,269 49,950 35,616 73, ,293 70, % A summary of estimated annual total phosphorus loadings into Lake Jesup over the period , based upon information provided in the FDEP Final TMDL Report (2006), is given on Table 1-2. During the period included in this analysis, approximately 37% of the annual total phosphorus loadings originated within the Lake Jesup sub-basin, with 41% originating from Howell Creek, 10% from Soldiers Creek, and 9% from Gee Creek. During the evaluation period, the annual average total phosphorus discharged into the lake from surface runoff was approximately 14.0 tons per year (12,698 kg/yr), with an average of 1.5 tons per year (1,361 kg/yr) originating in the Soldiers Creek basin.

14 1-5 TABLE 1-2 ESTIMATED ANNUAL TOTAL PHOSPHORUS LOADING INTO LAKE JESUP FROM (Source: FDEP Final TMDL Report, 2006) SUB-BASIN YEAR (tons/year) MEAN PERCENT (%) Gee Creek Howell Creek Lake Jesup Little Lake Howell Soldiers Creek Total % 1.2 Conceptual Treatment System Overview The Soldiers Creek drainage basin discharges into the western end of Lake Jesup. An overview of significant drainage patterns in urbanized portions of the Soldiers Creek sub-basin area is given on Figure 1-3. Water movement within the Soldiers Creek sub-basin is complex, with primary conveyance mechanisms consisting of lakes, ponds, wetlands, and open ditches. Drainage from eastern and western portions of the basin converge into a channelized portion of Soldiers Creek which runs in an approximate north-south direction. After discharging under CR 427, runoff from the urbanized portions of the drainage basin migrate approximately 2.25 miles through a hardwood wetland system, with both overland and channelized flow patterns, prior to discharging into Lake Jesup. The proposed alum treatment system for Soldiers Creek is located immediately north of CR 427, adjacent to the channelized portion of Soldiers Creek. The treatment system will be incorporated into an existing County wet detention pond located near the intersection of CR 427 and Country Club Road. This pond facility was originally constructed to provide treatment for runoff generated from the CR 427 right-of-way. A conceptual schematic of the proposed alum treatment system for Soldiers Creek is given on Figure 1-4. The channelized portion of Soldiers Creek which runs along the western side of the County pond provides drainage for approximately 5692 acres of urbanized areas located within the Soldiers Creek watershed prior to discharging into the wetland system on the south side of CR 427. The proposed treatment project will divert discharges from Soldiers Creek into the existing wet detention pond using a low-head diversion weir constructed in Soldiers Creek just north of CR 427. The incoming flow rate will be measured, and alum will be added on a flow-proportioned basis into the incoming tributary flow. The system will be capable of providing treatment for inflows up to 50 cfs. Pumps and controls for operation of the alum treatment system will be located in a small building on the north side of the pond. Floc generated from the alum treatment process will be collected in a trough structure inside the pond and pumped on a daily basis into a series of 5 on-site storage tanks. The storage tanks will be emptied on a periodic basis and the floc transported to the Seminole County Yankee Lake water treatment facility for disposal.

15 1-6 Lake Mary Blvd. Pond Site Lake Jesup Figure 1-3. Overview of Drainage Patterns in the Soldiers Creek Sub-basin Area. 4 x 6 CBC Water Intake ph Monitor Alum Addition Floc Storage Tanks Control Building Floc Removal Piping New Outfall Structure Access Roadway Floc Collection Trough Figure 1-4. Schematic of Proposed Stormwater Treatment System. Maintenance Ramp Diversion Weir

16 1-7 The proposed alum treatment system is a private partnership between Seminole County and the Florida Department of Transportation (FDOT). The site is currently owned by the County, but the parcel that encompasses Soldiers Creek north of CR 427 is privately owned. The County intends to acquire an easement along Soldiers Creek in the vicinity of the proposed pond inflow. This project has the potential to provide substantial reductions in phosphorus loadings discharging from the urbanized portions of the Soldiers Creek drainage basin. FDOT will use the system to compensate for additional nutrient loadings generated from the proposed widening of US north of the treatment pond (between Shepherd Road and Lake Mary Blvd.) in areas where traditional treatment is not feasible. 1.3 Work Efforts Conducted by ERD Field monitoring was conducted by Environmental Research & Design, Inc. (ERD) over the period from July-October 2010 and from January-March 2013 to evaluate hydrologic and water quality characteristics of discharges from Soldiers Creek to Lake Jesup. Monitoring was conducted during 26 weekly events which included both wet and dry season conditions. During each monitoring event, a composite water sample was collected for laboratory evaluations. Laboratory jar tests were conducted on 8 of the 16 tributary samples collected from July-October 2010 and 10 of the tributary samples collected from January-March 2013, using a wide range of aluminum doses, to evaluate the effectiveness of aluminum-based coagulants for treatment of tributary inflows. The results of the laboratory jar tests were used to evaluate the anticipated removal effectiveness and floc settling characteristics for the proposed Soldiers Creek system. This report has been divided into five separate sections for presentation of the work efforts performed by ERD and Pegasus. Section 1 contains an introduction to the report, background information on Lake Jesup and tributary loadings, an introduction to the proposed treatment system, and a general overview of the work efforts performed. A discussion of field and laboratory activities is given in Section 2. Section 3 contains a discussion of the results of the field and laboratory activities. An analysis of nutrient loadings generated in Soldiers Creek is given in Section 4, and a discussion of the proposed treatment system site is given in Section 5. Appendices are also attached which contain technical data and analyses used to support the information contained within the report.

17 SECTION 2 FIELD AND LABORATORY ACTIVITIES Field monitoring and laboratory analyses were conducted by ERD from July-October 2010 and from January-March 2013 to evaluate the feasibility of using an aluminum-based coagulant to reduce tributary loadings of total phosphorus discharging from Soldiers Creek into Lake Jesup. During the period from July-October 2010, field monitoring was conducted in Soldiers Creek adjacent to the proposed treatment site on a weekly basis for 16 weeks which included both wet and dry season conditions. Field monitoring included measurement of discharge rates in Soldiers Creek, as well as collection of field parameters and surface water samples. Laboratory jar testing was conducted to evaluate the effectiveness of alum for reducing total phosphorus concentrations. During the period from January-March 2013, field monitoring included only collection of Soldiers Creek samples on a weekly basis for laboratory jar testing using an alternative aluminum-based coagulant. A discussion of field and laboratory activities conducted during this project is given in the following sections Monitoring Site 2.1 Field Monitoring The monitoring site used for this project is located on the north side of CR 427 adjacent to the proposed treatment site. A photograph of Soldiers Creek upstream from CR 427 is given on Figure 2-1. Soldiers Creek discharges under CR 427 through two 6-ft x 11-ft CBCs and two 66-inch RCPs. Water levels in the area upstream from CR 427 are typically shallow due to the wide cross-section of the creek. Flow measurements were conducted approximately 200 ft upstream from CR 427 in a well defined channelized portion of Soldiers Creek to facilitate discharge measurements. A photograph of the discharge monitoring site is given on Figure Discharge Measurements Field monitoring of discharge rates was conducted by ERD personnel at the Soldiers Creek monitoring site during each of the monitoring events conducted from July-October Flow monitoring was conducted using the velocity/cross-sectional area method. Velocity measurements were performed at known distances across each channel cross-section using a Sontek Acoustic Doppler Velocity (ADV) meter with a resolution of 0.01 ft/sec (fps). The spacing between the velocity measurements was determined in the field such that not more than 10% of the total flow is represented by any one vertical cross-section. The depth at each section was also simultaneously measured using a graduated rod. A graduated tape was stretched across each channel so that reference locations could be determined for each simultaneous measurement of velocity and water depth. 2-1

18 2-2 6 x 11 CBC 66 RCP Flow Figure 2-1. Location of the Soldiers Creek Monitoring Site. Flow Monitoring Transect Figure 2-2. Photograph of the Soldiers Creek Monitoring Site.

19 2-3 If the water depth was less than 2.5 ft at a measurement point, the velocity was measured at 60% of the total water depth. If the water column depth exceeded 2.5 ft at a measurement point, velocity measurements were performed at 20% and 80% of the total water depth, with the mean section velocity determined by taking the average of the two measurements. The velocities were then integrated over each of the cross-sectional areas to determine the total discharge through the section on each monitoring date. A photograph of typical discharge monitoring is given in Figure 2-3. Figure 2-3. Typical Flow Monitoring Activities Surface Water Monitoring Monitoring activities at the surface water monitoring site conducted during 2010 included collection of physical-chemical field measurements and water samples for laboratory testing. Field measurements of temperature, ph, conductivity, dissolved oxygen, and oxidation-reduction potential (ORP) were conducted approximately mid-way within the water column at the monitoring site during each of the 16 monitoring events. Surface water samples were collected during each of the 16 monitoring events during 2010 for chemical characterization in the ERD Laboratory. Bulk water samples were also collected during 8 of the 16 monitoring events for laboratory jar testing with alum. Bulk water samples were collected in a pre-cleaned 20-liter polyethylene container and returned in ice to the ERD Laboratory. Monitoring conducted during 2013 included only collection of bulk water samples for laboratory jar testing. Bulk water samples were collected on 10 occasions from January-March 2013.

20 Laboratory Activities Jar Testing Laboratory jar tests were conducted using alum and alternative aluminum-based coagulants on the bulk tributary water samples collected during the field monitoring program. The objective of the jar tests is to evaluate the water quality response of coagulation at various doses on Soldiers Creek water collected during a wide range of flow conditions. The laboratory jar tests were conducted using a Phipps and Bird jar test apparatus. A photograph of the jar test apparatus is given on Figure 2-4. Figure 2-4. Laboratory Jar Test Apparatus. The 2010 series of jar tests were conducted using alum on bulk water samples at five separate doses, including 5, 7.5, 10, 12.5, and 15 mg Al/liter, to evaluate a wide range of potential application doses. Laboratory jar tests conducted on samples collected during 2010 resulted in equilibrium ph values less than 6.0 in many of the jar tests due to the initial low to moderate alkalinity and sub-neutral raw ph observed in Soldiers Creek samples. Laboratory jar testing at that time indicated that a supplemental buffering compound, such as sodium aluminate, would be necessary to maintain ph levels of the treated water above a value of 6.0, resulting in a 2-chemical injection system which substantially complicates the overall treatment process.

21 2-5 However, a number of new aluminum-based coagulants have become commonly available in recent years which reduce ph impacts resulting from addition of aluminum-based coagulants. A series of laboratory jar tests were conducted by ERD on Soldiers Creek water using 10 new aluminum-based coagulants which have recently become available. Excellent phosphorus removal efficiencies without significant ph reduction were obtained using a polyaluminum chloride (PACl) product, referred to as P-Floc, B , which is manufactured by Thatcher Chemical Corporation. This product is an aluminum chloride coagulant which has been partially pre-polymerized to reduce the production of hydronium ions during the coagulation process and minimize ph impacts. The B product is 5.3% Al by weight and has a basisity of 20%. This PACl product was used in all jar tests conducted during Jar testing conducted on Soldiers Creek water with the PACl product resulted in acceptable ph levels in each of the 10 jar test experiments conducted during Therefore, this polyaluminum chloride blend was selected for use with the Soldiers Creek system which eliminates the need for a 2-chemical addition system. All future references in this document to the laboratory jar testing and chemical doses using PACl refer to the B poly-aluminum chloride product. To begin each jar test, each of the test beakers was filled with 2 liters of tributary water. The paddle wheels were then activated and allowed to rotate at a constant speed of 60 rpm. The desired coagulant dose was then added to each container, and mixing was continued for a period of 60 seconds. At the end of the mixing period, the paddle wheels were stopped, removed from the beakers, and the resulting mixture allowed to settle. Measurements of ph were conducted initially in the raw sample and in each of the treated samples approximately 1 minute after addition of the selected coagulant dose and 24 hours after addition of the coagulant to document changes in ph after coagulant addition. The treated samples were then allowed to settle for a period of 24 hours, simulating settling processes which would occur within the water column of the floc collection trough. During the settling process, visual observations were recorded of floc settling rates for each coagulant dose, along with the time required for complete settling of the floc if it occurred prior to the end of the 24-hour period. This information is useful in designing and sizing the floc collection trough. At the end of the 24-hour settling period, the clear supernatant was decanted from each jar test container for subsequent laboratory analyses Laboratory Methods Each of the samples generated during the laboratory jar test procedures, including both raw and treated samples, was analyzed for a wide variety of chemical constituents, including general parameters, nutrients, and dissolved aluminum (2010 samples only). A summary of analytical methods and detection limits for analyses conducted by ERD on each of the generated jar test samples is given in Table 2-1. The ERD Laboratory is NELAC-certified (No. E ) for each of the parameters listed in Table 2-1.

22 2-6 General Parameters Nutrients TABLE 2-1 ANALYTICAL METHODS AND DETECTION LIMITS FOR LABORATORY ANALYSES CONDUCTED ON JAR TEST SAMPLES MEASUREMENT PARAMETER Hydrogen Ion (ph) Specific Conductivity Alkalinity Color Turbidity Ammonia-N (NH 3 -N) Nitrate + Nitrite (NO x -N) Total Nitrogen Orthophosphorus (SRP) Total Phosphorus METHOD SM-21 2, Sec H + B EPA-83 3, Sec SM-21, Sec B SM-21, Sec C SM-21, Sec B SM-21, Sec NH 3 G SM-21, Sec NO 3 F SM-21, Sec N C SM-21, Sec P F SM-21, Sec P B5 METHOD DETECTION LIMITS (MDLs) 1 N/A 0.1 mho/cm 0.5 mg/l 1 Pt-Co unit 0.3 NTU 5 g/l 5 g/l 10 g/l 1 g/l 1 g/l Metals Diss. Aluminum SM-21, Sec Al E 0.8 g/l NOTES: 1. MDLs are calculated based on the EPA method of determining detection limits 2. Standard Methods for the Examination of Water and Wastewater, 21 st Edition, Methods for Chemical Analysis of Water and Wastes, EPA 600/ , Revised March 1983

23 SECTION 3 RESULTS Field monitoring was conducted by ERD over the period from July-October 2010 and January-March 2013 to evaluate the characteristics of discharges through Soldiers Creek at the proposed treatment site. Field measurements of discharge rates and physical-chemical parameters were conducted during the 2010 monitoring events, and tributary samples were collected for laboratory characterization during both 2010 and Laboratory jar tests were also conducted to evaluate the effectiveness for removal of phosphorus from the tributary flows. The results of the field and laboratory testing are discussed in the following sections Discharge 3.1 Field Measurements A summary of field measured discharge rates at the Soldiers Creek site during the 2010 monitoring program is given in Table 3-1. In general, a relatively large degree of variability was observed in measured discharge rates between the 14 monitoring dates, with measured discharge rates ranging from cfs. A graphical summary of measured discharge rates at the Soldiers Creek monitoring site is given on Figure 3-1. Overall, the mean discharge rate measured in Soldiers Creek over the period from July-October 2010 was 5.85 cfs. TABLE 3-1 FIELD MEASURED DISCHARGE RATES IN SOLDIERS CREEK FROM JULY-OCTOBER 2010 DATE DISCHARGE (cfs) DATE DISCHARGE (cfs) 7/12/ /7/ /21/ /13/ /28/ /21/ /2/ /29/ /17/ /5/ /25/ /12/ /1/ /21/ Mean: 5.85 cfs 3-1

24 Discharge Rate (cfs) Jul-10 Aug-10 Sep-10 Oct-10 Nov-10 Figure 3-1. Comparison of Measured Discharge Rates at the Soldiers Creek Monitoring Site. Photographs of observed flow conditions during the 2010 field monitoring program are illustrated on Figure 3-2. Flow conditions during relatively high discharge rates (>10 cfs) are indicated on Figure 3-2a. Although flow conditions referenced in this figure are referred to as high flow conditions, water levels within the creek can become substantially higher, as indicated by the visible water stains on the discharge structure beneath CR 427. More moderate flow conditions (5-10 cfs) are indicated on Figure 3-2b, with discharge through the creek restricted to a relatively small portion of the available area. The photograph included as Figure 3-2c was taken during the final monitoring event on October 21, At this time, virtually the entire creek bottom was dry with the exception of a small shallow stream which generated a measured discharge rate of only 0.08 cfs. Estimates of typical discharge rates from Soldiers Creek in the vicinity of the proposed treatment system are needed to properly design the alum treatment process. Unfortunately, historical discharge data do not appear to be available at the proposed treatment system site other than the field measurements conducted by ERD as part of this project. However, USGS maintains a long-term gauging site (No ) in Soldiers Creek, approximately 1.25 miles downstream from the proposed project site. Daily discharge measurements at this site are available on a continuous basis from 1987 to the present. Unfortunately, these discharge data cannot be used directly as an estimate of discharges from Soldiers Creek at the proposed treatment site since a significant portion of the Soldiers Creek basin discharges into Soldiers Creek between the proposed pond site and the USGS gauging station. An overview of comparative locations of the proposed treatment site and the USGS gauging station along Soldiers Creek is given in Figure 3-3.

25 3-3 a. High Flow Conditions b. Moderate Flow Conditions c. Low Flow Conditions Figure 3-2. Variability in Flow Characteristics at the Soldiers Creek Site During the Field Monitoring Program. A graphical comparison of field measured discharge rates in Soldiers Creek at the proposed project site and mean daily discharge measurements at the USGS gauging station over the period from July-October 2010 is given on Figure 3-4. With the exception of one data point, all of the measured discharge rates at the project site are approximately equal to or less than the mean daily discharge rates measured at the USGS gauging station approximately 1.25 miles downstream.

26 3-4 Pond Site USGS Gauging Site (No ) Lake Jesup Figure 3-3. Comparative Locations of the Proposed Treatment System Site and the USGS Gauging Station Along Soldiers Creek. 50 USGS ERD 40 Discharge (cfs) Jun Jul Aug Sep Oct Nov Dec Figure 3-4. Comparison of Measured Soldiers Creek Discharge Rates at the Project Site and USGS Gauging Station Over the Period from July-October 2010.

27 3-5 A graphical relationship between field measured discharge rates at the proposed project site and mean daily discharges at the USGS gauging site is given on Figure 3-5. This evaluation excludes the elevated discharge measurement of 23.9 cfs measured in Soldiers Creek on August 25, The slope of the relationship indicated on Figure 3-5 is 0.90, suggesting that discharge rates at the project site are approximately 90% of the average daily discharge measurements recorded at the USGS gauging site and suggests that discharge rates at the USGS gauging station may be useful in estimating potential discharge rates likely to occur at the proposed project site. 16 ERD Discharge Measurements (cfs) slope = 0.90 r ² = USGS Average Daily Discharge Measurements (cfs) Figure 3-5. Relationship Between Field Measured Discharge Rates at the Proposed Project Site with Mean Daily Discharges at the USGS Gauging Site. A graphical summary of relationships between rainfall and discharge in Soldiers Creek during the field monitoring program from August-October 2010 is given on Figure 3-6. Rainfall data included on this figure reflect total daily rainfall measured at the NCDC meteorological station at the Sanford-Orlando Airport. Discharge data are provided for both the ERD field measurements as well as mean daily discharges at the USGS gauging station in Soldiers Creek. In general, discharge in Soldiers Creek appears to be well correlated with rainfall in the adjacent sub-basin areas. The data suggest that a lag of several days occurs between rainfall events and maximum discharge rates in Soldiers Creek.

28 USGS Discharge ERD Discharge Measurements Sanford Orlando Airport Rainfall Discharge (cfs) Daily Rainfall (inches) Aug-10 Sep-10 Oct-10 Nov-10 Figure 3-6. Summary of Rainfall and Discharge in Soldiers Creek During the Field Monitoring Program from August-October Physical-Chemical Parameters As mentioned previously, collection of physical-chemical field measurements was conducted during the 2010 monitoring events. A summary of physical-chemical field measurements collected in Soldiers Creek from July-October 2010 is given on Table 3-2. Measured parameters include temperature, ph, conductivity, TDS, dissolved oxygen, oxygen saturation percentage, and turbidity. Field measurements were collected at approximately middepth in the water column during each monitoring event. In general, water discharging through Soldiers Creek was approximately neutral in ph, with measured values ranging from and an overall mean of Measured conductivity values within the creek were low to moderate in value, ranging from mho/cm, with an overall mean of 205 mho/cm. Measured TDS concentrations mimic the pattern exhibited by conductivity, with measured values ranging from mg/l. Relatively good dissolved oxygen concentrations were measured in Soldiers Creek during the majority of the events. Dissolved oxygen measurements less than the minimum Class III criterion of 5.0 mg/l were observed during only 2 of the 16 monitoring events. Water within Soldiers Creek maintained dissolved oxygen saturation levels ranging from approximately 64-97%.

29 3-7 DATE TABLE 3-2 PHYSICAL-CHEMICAL FIELD MEASUREMENTS COLLECTED IN SOLDIERS CREEK FROM JULY-OCTOBER 2010 TIME TEMP ( o C) ph (s.u.) SPECIFIC CONDUCTIVITY ( mho/cm) TDS (mg/l) DO (mg/l) DO % SAT. (%) TURBIDITY (NTU) 7/12/ : /21/ : /28/2010 8: /2/ : /10/ : /17/ : /25/ : /1/ : /7/ : /13/ : /21/ : /29/ : /5/ : /12/ : /21/ : Mean: Minimum: Maximum: Measured turbidity levels in Soldiers Creek were relatively low in value during the majority of the monitoring events. With the exception of only two measurements, the majority of measured turbidity values were approximately 3 NTU or less. A graphical summary of trends in field measured values of ph, conductivity, dissolved oxygen, and turbidity in Soldiers Creek from July-October 2010 is given on Figure 3-7. Field measured ph values appear to have an inverse relationship with the field measured discharge rates summarized in Figure 3-1, with increases in discharge rates correlated with lower ph values, and lower discharge rates associated with higher ph values. A similar pattern also appears to exist for conductivity and dissolved oxygen as well, with lower measured values observed for these parameters under high flow conditions and higher measurements observed under low flow conditions. Significant increases in turbidity appear to be limited primarily to discharge rates of approximately cfs or more.

30 3-8 ph Conductivity ph Conductivity (µmho/cm) Jul-10 Aug-10 Sep-10 Oct-10 Nov Jul-10 Aug-10 Sep-10 Oct-10 Nov-10 Dissolved Oxygen Turbidity Dissolved Oxygen (mg/l) Turbidity (NTU) Jul-10 Aug-10 Sep-10 Oct-10 Nov-10 0 Jul-10 Aug-10 Sep-10 Oct-10 Nov-10 Figure 3-7. Trends in Field Measured Values of ph, Conductivity, Dissolved Oxygen, and Turbidity in Soldiers Creek from July-October 2010.

31 Raw Water Characteristics 3.2 Laboratory Analyses A summary of chemical characteristics for each of the individual Soldiers Creek samples collected from July-October 2010 and from January-March 2013 is given on Table 3-3. A statistical summary is also provided which includes the minimum and maximum values measured for each parameter, as well as the geometric mean. The geometric mean value is used as a measurement of central tendency since environmental data commonly exhibit a geometric distribution. In general, water collected from Soldiers Creek was moderately to well buffered, with measured alkalinity values ranging from mg/l. The geometric mean value of 63.1 mg/l suggests a moderately buffered water. Measured concentrations of both ammonia and NO x were low in value in samples collected at the monitoring site during each of the two monitoring periods. The geometric mean values of 48 g/l and 94 g/l for ammonia and NO x, respectively, reflect extremely low values for these parameters. The dominant nitrogen species in Soldiers Creek appears to be dissolved organic nitrogen which is consistent with the relatively high color within the water. Dissolved organic nitrogen comprises approximately 50% or more of the total nitrogen measured, with particulate nitrogen comprising approximately 25% of the total nitrogen measured during most events. Measured total nitrogen concentrations in Soldiers Creek ranged from g/l, with an overall mean of 757 g/l. Total nitrogen concentrations in this range are slightly lower than nitrogen concentrations commonly observed in urban streams. Elevated levels of soluble reactive phosphorus (SRP) were observed in Soldiers Creek during a majority of the monitoring events. Measured SRP concentrations ranged from g/l, with a geometric mean value of 60 g/l, and SRP comprised approximately 60% or more of the total phosphorus measured during most events. Relatively low levels of dissolved organic phosphorus and particulate phosphorus were measured in the Soldiers Creek samples, with each contributing approximately 15% of the total phosphorus within the sample. Measured total phosphorus concentrations ranged from g/l, with an overall mean of 101 g/l. This value is typical of phosphorus concentrations commonly observed in urban tributaries. Water within Soldiers Creek was found to be highly colored, with measured color concentrations ranging from Pt-Co units. The mean color concentration of 183 Pt-Co units reflects a highly colored surface water. Measured concentrations of dissolved aluminum in Soldiers Creek ranged from g/l, with a geometric mean value of 157 g/l. A statistical summary of measured concentrations of ph, alkalinity, conductivity, turbidity, color, and dissolved aluminum in Soldiers Creek samples during the July-October 2010 and January-March 2013 monitoring periods is given on Figure 3-8 based upon the data summarized in Table 3-3. Listed values for ph, conductivity, and turbidity reflect laboratory measurements for these parameters even though the measurements were also determined in the field. The plots of color and dissolved aluminum are based on the 2010 data only since these parameters were not measured on the 2013 samples.

32 Minimum Value Maximum Value , Geometric Mean TABLE 3-3 CHARACTERISTICS OF SOLDIERS CREEK SAMPLES COLLECTED FROM JULY-OCTOBER 2010 AND FROM JANUARY-MARCH 2013 DATE ph (s.u.) Alk. (mg/l) Cond. ( mho/cm) NH 3 ( g/l) NO x ( g/l) Diss. Org. N ( g/l) Part. N ( g/l) PARAMETER Total N ( g/l) SRP ( g/l) Diss. Org. P ( g/l) Part. P ( g/l) Total P ( g/l) Turbidity (NTU) Color (Pt-Co) 7/12/ /21/ , /28/ , /2/ /10/ /17/ /25/ /1/ /7/ /13/ /21/ /29/ /5/ /12/ /22/ /7/ /14/ , /23/ , /31/ , /5/ /13/ /20/ /28/ /7/ /14/ Diss. Al ( g/l)

33 ph Alkalinity (mg/l) Conductivity (µmho/cm) Turbidity (NTU) Color (Co-Pt) 150 Dissolved Al (µg/l) Figure 3-8. Summary of Measured Concentrations of ph, Alkalinity, Conductivity, Turbidity, Color, and Dissolved Aluminum in Soldiers Creek Samples During the Periods of July-October 2010 and January-March The data for each parameter is presented in the form of Tukey box plots, also often called "box and whisker plots". The bottom line of the box portion of each plot represents the lower quartile, with 25% of the data points falling below this value. The upper line of the box represents the 75% upper quartile, with 25% of the data falling above this value. The blue horizontal line within the box represents the median value, with 50% of the data falling both above and below this value. The red horizontal line within the box represents the mean of the data points. The vertical lines, also known as "whiskers", represent the 10 and 90 percentiles for the data sets. Individual values which fall outside of the percentile range, sometimes referred to as outliers, are indicated as red dots. However, in general, a minimum of 7-10 data points is required for most data sets to generate enough statistical variability for the whiskers to show on the plots. Since the data sets for the tributary samples contain only five samples each, the box and whisker plots provided in this section do not contain the whiskers. The box and whisker plots summarized on Figure 3-8 indicate a relatively low degree of variability in chemical characteristics for samples collected in Soldiers Creek. This low degree of variability is beneficial in evaluating and designing a chemical treatment process for the creek.

34 3-12 A graphical summary of statistical variability in measured concentrations of nitrogen species in Soldiers Creek water is given on Figure 3-9. A relatively low degree of variability is apparent for measured concentrations of ammonia, NO x, and particulate nitrogen. A higher degree of variability is apparent in measured concentrations of dissolved organic nitrogen and total nitrogen. Dissolved organic nitrogen is clearly the dominant form of nitrogen present in Soldiers Creek water, followed by particulate nitrogen, NO x, and ammonia NH 3 (µg/l) NO x (µg/l) Dissolved Organic N (µg/l) Particulate N (µg/l) Total N (µg/l) Figure 3-9. Summary of Measured Concentrations of Nitrogen Species in Soldiers Creek Samples During the Periods of July-October 2010 and January-March A graphical summary of variability in measured concentrations of phosphorus species in samples collected from Soldiers Creek is given on Figure A relatively low degree of variability is also apparent for measured phosphorus species, particularly for dissolved organic phosphorus and particulate phosphorus. Dissolved SRP is clearly the dominant phosphorus species present in the Soldiers Creek samples.

35 SRP (µg/l) 100 Dissolved Organic P (µg/l) 100 Particulate P (µg/l) 100 Total P (µg/l) Figure Summary of Measured Concentrations of Phosphorus Species in Soldiers Creek Samples During the Periods of July-October 2010 and January-March A graphical summary of temporal variability in nitrogen species in Soldiers Creek samples from July-October 2010 and January-March 2013 is given in Figure Contributions from ammonia and NO x remained relatively constant throughout the monitoring program. The primary source of the variability in total nitrogen concentrations appears to be variability in dissolved organic nitrogen. A general inverse relationship appears to exist between measured nitrogen concentrations during 2010 and discharge rates in Soldiers Creek, as indicated on Figure 3-1. It appears that nitrogen concentrations are highest during periods of low discharge rates, with the lowest observed nitrogen concentrations during periods of elevated discharge rates, resulting primarily from reductions in dissolved organic nitrogen concentrations. The observed high concentrations of dissolved organic nitrogen concentrations under low flow conditions likely originate within wetland systems located throughout the Soldiers Creek basin. As flow rates increase, contributions from wetland areas become less significant, resulting in a decrease in dissolved organic nitrogen.

36 3-14 1,200 1,000 Nitrogen Species (µg/l) /12/10 7/21/10 7/28/10 8/2/10 8/10/10 8/17/10 8/25/10 9/1/10 9/7/10 9/13/10 9/21/10 9/29/10 10/5/10 10/12/10 10/22/10 1/7/13 1/14/13 1/23/13 1/31/13 2/5/13 2/13/13 2/20/13 2/28/13 3/7/13 3/14/13 NH3 NOx Diss. Organic N Part. N Figure Temporal Variability in Nitrogen Species in Soldiers Creek Samples from July- October 2010 and January-March A graphical summary of temporal variability in phosphorus species in Soldiers Creek samples from July-October 2010 and January-March 2013 is given on Figure SRP is clearly the dominant phosphorus species in Soldiers Creek. Variability in concentrations of particulate phosphorus and SRP appear to be the primary causes for the observed variability in total phosphorus concentrations. Based on the 2010 data, phosphorus concentrations in Soldiers Creek appear to be positively correlated with the measured discharge rates summarized on Figure 3-1, with increases in discharge rates generally corresponding to increases in phosphorus concentrations.

37 Phoshorus Species (µg/l) /12/10 7/21/10 7/28/10 8/2/10 8/10/10 8/17/10 8/25/10 9/1/10 9/7/10 9/13/10 9/21/10 9/29/10 10/5/10 10/12/10 10/22/10 1/7/13 1/14/13 1/23/13 1/31/13 2/5/13 2/13/13 2/20/13 2/28/13 3/7/13 3/14/13 SRP Diss. Organic P Part. P Figure Temporal Variability in Phosphorus Species in Soldiers Creek Samples from July- October 2010 and January-March Laboratory Jar Testing A discussion of the results of laboratory jar tests conducted using the poly-aluminum chloride (PACl) B product on Soldiers Creek samples collected from January-March 2013 is given in the following sections. The jar tests on the 2010 samples were conducted using a combination of alum and sodium aluminate and are not discussed in this document General Jar Test Characteristics A summary of general characteristics of laboratory jar tests conducted using PACl on Soldiers Creek samples collected during the field monitoring program is given on Table 3-4. Laboratory jar tests were conducted at six separate doses, including 2, 4, 6, 8, 10, and 12 mg Al/liter, using the PACl product B Information is provided on the collection date for the bulk water sample, the applied aluminum dose in mg Al/liter, ph measurements collected prior to and during the jar test procedure, and visual observations of floc formation and settling for each of the 6 evaluated coagulant doses and each of the 10 monitoring dates.

38 3-16 During each of the 10 jar tests using the PACl product, aluminum doses as high as mg Al/liter could be added without a ph depression to a value significantly below 6.0. After a settling period of 24 hours, each of the PACl treated samples exhibited equilibrium ph values well in excess of 6.0. Therefore, the selected PACl product can be safely added at aluminum doses up to 12 mg Al/liter without concern over ph impacts to the treated water. Measured ph values are provided on Table 3-4 for each coagulant dose at times of one minute and 24 hours following coagulant addition. Mean values for ph measurements during the 10 jar test experiments are provided at the bottom of the table. On an average basis, equilibrium ph values in the treated samples exceeded a ph value of 6.0 in all of the jar test samples as measured approximately 24 hours following alum addition. Visual observations of floc characteristics are also provided in Table 3-4. Visual characteristics of floc formation and settling for a given coagulant dose are virtually identical for each of the 10 jar test samples, suggesting a consistency in the coagulation process during the field testing program. After a 24-hour settling period, Soldiers Creek samples treated at coagulant doses of 2, 4, and 6 mg Al/liter were still cloudy and contained a very fine milkish floc which was resistant to settling. This condition was improved at a coagulant dose of 8 mg Al/liter, although a cloudy appearance was still present within the treated samples. However, coagulant doses of 10 and 12 mg Al/liter created a large floc which settled rapidly, with a clear water column after approximately one hour of settling. Based upon floc settling characteristics, the minimum recommended coagulant dose for treatment of water in Soldiers Creek appears to be approximately 10 mg Al/liter in order to generate a settleable floc particle Jar Test Results A complete listing of the results of jar tests conducted on Soldiers Creek samples collected from January-March 2013 is given in Appendix A. Laboratory analyses are provided for general parameters and nutrients in raw and PACl treated samples for each of the 10 jar tests. A graphical comparison of changes in ph, alkalinity, conductivity, and turbidity in PACl treated samples collected from Soldiers Creek is given in Figure In general, addition of PACl to Soldiers Creek water resulted in a slight increase in ph at doses of 2 and 4 mg Al/liter with slight decreases in ph with increasing coagulant dose at higher doses. Increases in PACl dose also resulted in decreases in measured alkalinity within the treated samples. The observed decreases in alkalinity appear to level off at coagulant doses of 10 mg Al/liter and higher. The addition of PACl resulted in slight increases in measured conductivity with each increasing coagulant dose due to the addition of chloride ions in the solution.

39 3-17 TABLE 3-4 CHARACTERISTICS OF LABORATORY JAR TESTS CONDUCTED ON SOLDIERS CREEK SAMPLES COLLECTED FROM JANUARY-MARCH 2013 COLLECTION DATE 1/7/13 1/14/13 1/23/13 1/31/13 2/5/13 2/13/13 2/20/13 COAGULANT DOSE (mg Al/liter) 2 MEASURED ph (s.u.) Raw 1 min. 24 hours FLOC FORMATION AND SETTLING OBSERVATIONS No change in appearance Water cloudy, no floc on bottom Water cloudy, no floc on bottom Water cloudy, thin floc layer on bottom Water clear, floc layer on bottom Water clear, floc layer on bottom No change in appearance Water cloudy, no floc on bottom Water cloudy, no floc on bottom Water cloudy, thin floc layer on bottom Water clear, floc layer on bottom Water clear, floc layer on bottom No change in appearance Water cloudy, no floc on bottom Water cloudy, no floc on bottom Water cloudy, thin floc layer on bottom Water clear, floc layer on bottom Water clear, floc layer on bottom No change in appearance Water cloudy, no floc on bottom Water cloudy, no floc on bottom Water cloudy, thin floc layer on bottom Water clear, floc layer on bottom Water clear, floc layer on bottom No change in appearance Water cloudy, no floc on bottom Water cloudy, no floc on bottom Water cloudy, thin floc layer on bottom Water clear, floc layer on bottom Water clear, floc layer on bottom No change in appearance Water cloudy, no floc on bottom Water cloudy, no floc on bottom Water cloudy, thin floc layer on bottom Water clear, floc layer on bottom Water clear, floc layer on bottom No change in appearance Water cloudy, no floc on bottom Water cloudy, no floc on bottom Water cloudy, thin floc layer on bottom Water clear, floc layer on bottom Water clear, floc layer on bottom

40 3-18 TABLE CONTINUED CHARACTERISTICS OF LABORATORY JAR TESTS CONDUCTED ON SOLDIERS CREEK SAMPLES COLLECTED FROM JANUARY-MARCH 2013 COLLECTION DATE 2/28/13 3/7/13 3/14/13 Mean Values COAGULANT DOSE (mg Al/liter) 2 MEASURED ph (s.u.) Raw 1 min. 24 hours FLOC FORMATION AND SETTLING OBSERVATIONS No change in appearance Water cloudy, no floc on bottom Water cloudy, no floc on bottom Water cloudy, thin floc layer on bottom Water clear, floc layer on bottom Water clear, floc layer on bottom No change in appearance Water cloudy, no floc on bottom Water cloudy, no floc on bottom Water cloudy, thin floc layer on bottom Water clear, floc layer on bottom Water clear, floc layer on bottom No change in appearance Water cloudy, no floc on bottom Water cloudy, no floc on bottom Water cloudy, thin floc layer on bottom Water clear, floc layer on bottom Water clear, floc layer on bottom No change in appearance Water cloudy, no floc on bottom Water cloudy, no floc on bottom Water cloudy, thin floc layer on bottom Water clear, floc layer on bottom Water clear, floc layer on bottom A graphical comparison of changes in turbidity and TSS in PACl treated samples collected from Soldiers Creek is given in Figure PACl treatment resulted in increases in measured turbidity values at PACl doses of 2, 4, 6, and 8 mg Al/liter due to the formation of a fine microscopic floc which was resistant to settling. These types of floc particles are common as a result of coagulation of colored waters at low aluminum doses. However, PACl doses of 10 mg Al/liter and higher resulted in turbidity values less than the measured concentrations in the raw sample. A similar pattern was also observed for TSS, with TSS increases at lower doses and TSS removal at higher doses.

41 3-19 ph Alkalinity ph Outlier 90 th Percentile 75 th Percentile Median Mean 25 th Percentile Alkalinity (mg/l) th Percentile 0 Raw 2.0 mg/l 4.0 mg/l 6.0 mg/l 8.0 mg/l 10.0 mg/l 12.0 mg/l Raw 2.0 mg/l 4.0 mg/l 6.0 mg/l 8.0 mg/l 10.0 mg/l 12.0 mg/l Conductivity Conductivity (µmho/cm) Raw 2.0 mg/l 4.0 mg/l 6.0 mg/l 8.0 mg/l 10.0 mg/l 12.0 mg/l Figure Changes in ph, Alkalinity, and Conductivity in PACl Treated Samples Collected from Soldiers Creek.

42 3-20 Turbidity TSS Turbidity (NTU) Outlier 90 th Percentile 75 th Percentile Median Mean 25 th Percentile 10 th Percentile TSS (mg/l) Raw 2.0 mg/l 4.0 mg/l 6.0 mg/l 8.0 mg/l 10.0 mg/l 12.0 mg/l Raw 2.0 mg/l 4.0 mg/l 6.0 mg/l 8.0 mg/l 10.0 mg/l 12.0 mg/l Figure Changes in Turbidity and TSS in PACl Treated Samples Collected from Soldiers Creek. A graphical comparison of changes in nitrogen species in PACl treated samples collected from Soldiers Creek is given on Figure The addition of PACl had little impact on measured concentrations of either ammonia or NO x. Doses of 2 and 4 mg Al/liter appears to have little impact on measured concentrations of either particulate nitrogen or total nitrogen. This behavior is closely linked to the formation of the microfloc which was resistant to settling and kept adsorbed nitrogen species in suspension, and therefore, included in the laboratory analyses. However, significant decreases in both particulate nitrogen and total nitrogen were observed at aluminum doses of 6 mg Al/liter and higher. A graphical comparison of changes in phosphorus species in PACl treated samples collected from Soldiers Creek is given on Figure PACl addition resulted in a rapid decrease in SRP concentrations, with virtually complete removal of SRP achieved at doses of 8 mg Al/liter and higher. Decreases in dissolved organic phosphorus were also observed with increasing alum dose. Similar to the trend exhibited by turbidity, particulate phosphorus appears to increase at PACl doses of 2 and 4 mg Al/liter due to the formation of the microfloc and phosphorus adsorbed onto the floc particles. However, excellent particulate phosphorus removals appear to be achieved at doses of 8 mg Al/liter or higher. A steady decrease in total phosphorus concentrations were observed with increasing PACl doses in excess of 2 mg Al/liter. Excellent removal efficiencies for total phosphorus were observed at a dose of 10 mg Al/liter, with only small additional removals achieved at higher PACl doses.

43 3-21 Ammonia NO X Outlier 90 th Percentile 75 th Percentile Median Mean 25 th Percentile 10 th Percentile NH 3 (µg/l) NO x (µg/l) Raw 2.0 mg/l 4.0 mg/l 6.0 mg/l 8.0 mg/l 10.0 mg/l 12.0 mg/l Raw 2.0 mg/l 4.0 mg/l 6.0 mg/l 8.0 mg/l 10.0 mg/l 12.0 mg/l Particulate N Total N Particulate N (µg/l) Total N (µg/l) Raw 2.0 mg/l 4.0 mg/l 6.0 mg/l 8.0 mg/l 10.0 mg/l 12.0 mg/l Raw 2.0 mg/l 4.0 mg/l 6.0 mg/l 8.0 mg/l 10.0 mg/l 12.0 mg/l 200 Figure Changes in Nitrogen Species in PACl Treated Samples Collected from Soldiers Creek.

44 3-22 SRP Dissolved Organic P SRP Conc. (µg/l) Outlier 90 th Percentile 75 th Percentile Median Mean 25 th Percentile 10 th Percentile Dissolved Organic P Conc. (µg/l) Raw 2.0 mg/l 4.0 mg/l 6.0 mg/l 8.0 mg/l 10.0 mg/l 12.0 mg/l Raw 2.0 mg/l 4.0 mg/l 6.0 mg/l 8.0 mg/l 10.0 mg/l 12.0 mg/l Particulate P Total P Particulate P Conc. (µg/l) Raw 2.0 mg/l 4.0 mg/l 6.0 mg/l 8.0 mg/l 10.0 mg/l 12.0 mg/l Raw 2.0 mg/l 4.0 mg/l 6.0 mg/l 8.0 mg/l 10.0 mg/l 12.0 mg/l Total P Conc. (µg/l) Figure Changes in Phosphorus Species in PACl Treated Samples Collected from Soldiers Creek.

45 3-23 A summary of mean characteristics of jar tests conducted on Soldiers Creek samples using PACl from January-March 2013 is given on Table 3-5. The values summarized in this table reflect the mean values for each of the 10 jar test samples. The equilibrium total phosphorus concentration achieved during the jar tests at a dose of 10 mg Al/liter was 5 g/l. Relatively small additional improvements in total phosphorus concentrations were achieved at higher PACl doses. TABLE 3-5 MEAN CHARACTERISTICS OF JAR TESTS CONDUCTED ON SOLDIERS CREEK SAMPLES USING PACl FROM JANUARY-MARCH 2013 PARAMETER UNITS COAGULANT DOSE (mg Al/liter) Raw ph s.u Alkalinity mg/l Conductivity mho/cm NH 3 g/l NO x g/l Diss. Organic N g/l Particulate N g/l Total N g/l SRP g/l Diss. Organic P g/l Particulate P g/l Total P g/l Turbidity NTU TSS mg/l Based upon the results summarized in Table 3-5, and in Figures 3-13 through 3-15, a coagulant dose of approximately 10 mg Al/liter appears to be the optimum dose for treatment of Soldiers Creek water. The floc generated at this dose exhibited excellent settling characteristics with virtually complete removal from the water column in approximately 1-2 hours, and only small additional improvements in total phosphorus removal were achieved at higher doses.

46 Removal Efficiencies A summary of mean removal efficiencies for total nitrogen, phosphorus species, and turbidity in the PACl treated samples collected from Soldiers Creek is given in Table 3-6. The values summarized in this table reflect the mean removal efficiencies for the 10 jar tests conducted from January-March TABLE 3-6 MEAN REMOVAL EFFICIENCIES FOR JAR TESTS CONDUCTED ON SOLDIERS CREEK SAMPLES FROM JANUARY-MARCH 2013 DOSE (mg Al/liter) Total N SRP PARAMETER (%) Diss. Organic P Particulate P Total P Turbidity With the exception of SRP, relatively poor removal efficiencies were achieved for each of the listed parameters at PACl doses less than 5 mg Al/liter. A significant increase in concentration was observed for particulate phosphorus and turbidity at these doses due to the formation of a small microfloc which was resistant to settling. Removal efficiencies generally improved for all measured parameters at doses of 6-8 mg Al/liter. However, increases in measured concentrations were still observed for turbidity due to the microfloc formation. Good removal efficiencies were achieved for all of the listed parameters at PACl doses of 10 mg Al//liter and higher. At this dose, a removal efficiency of 43% was achieved for total nitrogen, with a removal of 97% for SRP, 87% for dissolved organic phosphorus, 88% for particulate phosphorus, and 93% for total phosphorus. A slight additional improvement in removal efficiencies was observed at a dose of 12 mg Al/liter. However, the additional small removal efficiencies do not appear to justify the significant additional chemical cost at this higher dose. Therefore, a PACl dose of 10 mg Al/liter appears to be the optimum dose for treatment of water discharging through Soldiers Creek.

47 Floc Production Estimated floc production rates were evaluated for PACl treated Soldiers Creek water at each of the 6 evaluated aluminum doses. Floc generated during each of the laboratory jar tests were combined together by dose and allowed to settle for a period of approximately 30 days. The total floc volume at the end of the settling period was measured and divided by the total sample volume treated during the laboratory jar testing which generated the measured floc volume. A tabular summary of floc generation rates for PACl treated Soldiers Creek water is given in Table 3-7. Coagulation at aluminum doses of 2 and 4 mg Al/liter generated relatively little floc due to the formation of microfloc particles. A similar pattern was also observed at doses of 6 and 8 mg Al/liter, although a larger percentage of generated floc settled at this dose compared with the 5 mg Al/liter dose. Beginning at doses of 10 mg Al/liter and higher, complete floc settling was observed, and the floc generation rates listed for these doses reflect the entire generated floc volume. At the recommended optimum dose of 10 mg Al/liter, the anticipated floc generation (after a settling period of approximately 30 days) will be approximately 0.43% of the treated water volume. DOSE (mg Al/liter) TABLE 3-7 CALCULATED FLOC GENERATION RATES FOR PACl TREATED SOLDIERS CREEK WATER TOTAL FLOC VOLUME 1 (ml) TREATED WATER VOLUME (ml) FLOC GENERATION RATE (% of Treated Volume) , , , , , , After 30 days of settling

48 SECTION 4 EVALUATION OF NONPOINT SOURCE LOADINGS IN THE SOLDIERS CREEK DRAINAGE BASIN A hydrologic and pollutant loading model was developed for portions of the Soldiers Creek drainage basin which discharge to the point of treatment for the proposed alum tributary treatment system. This analysis is conducted to verify that significant loadings are present at the proposed point of treatment to justify construction and operation of the proposed treatment system, as well as quantify the anticipated pollutant load reductions which will be achieved by the alum system. Hydrologic and pollutant loading estimates were generated using the ERD Non-Point Source Loading Model (NPSLM) which is a GIS-linked spreadsheet model. A general discussion of the Soldiers Creek drainage basin is provided in the following sections, along with estimates of annual hydrologic and pollutant loadings and anticipated load reductions achieved by the proposed system. Characterization information and data for the Soldiers Creek drainage basin were generated by Pegasus Engineering (Pegasus) and provided to ERD for use in estimating pollutant loadings. A discussion of work efforts conducted by Pegasus and ERD is given in the following sections. In this section, the term Soldiers Creek drainage basin refers to the portion of the overall Soldiers Creek drainage basin which is located upstream from the proposed treatment system site General Characteristics 4.1 Characteristics of the Soldiers Creek Basin An overall delineation of sub-basin areas discharging to Soldiers Creek upstream of the proposed treatment system was conducted by Pegasus. This delineation was based upon a review of previous basin delineations, one-foot Lidar contour data, and general familiarity of the Soldiers Creek basin by Pegasus based upon extensive previous work conducted within the basin. An overall schematic of the Soldiers Creek drainage basin upstream from the proposed treatment site is given on Figure 4-1 based upon information provided by Pegasus. The drainage basin contains a number of natural lakes and stormwater management systems, along with numerous conveyance channels which collect and convey runoff within the basin to the ultimate point of discharge at the proposed treatment site. Drainage generated in northern portions of the basin migrates in a southeasterly direction, with runoff from southern portions of the drainage basin migrating in a general northern and northwestern direction. These flows converge in the eastern and northeastern portions of the basin and discharge from the southeast lobe of the basin at the location of the proposed treatment system site. 4-1

49 4-2 µ Greenwood Lake Myrtle Lake Geoffrey Lake Ruth Lake Searcy Lake Mud Lake Legend Sub-Basin Boundaries Closed Sub-Basins 3,0001, ,000 6,000 9,000 Feet Lakes and Streams Roads Figure 4-1. Overview of the Soldiers Creek Basin.

50 4-3 The total area of the Soldiers Creek basin which potentially discharges to the proposed treatment site, excluding the pond itself, is approximately 6,608 acres. However, approximately acres of the drainage basin are thought to reflect closed sub-basins which appear to retain virtually all generated runoff except during extreme storm events. For purposes of this analysis, these areas (highlighted in pink in Figure 4-1) are not included in estimates of hydrologic and nutrient loadings discharging at the treatment site. Therefore, the total contributing sub-basin area discharging to the point of treatment is assumed to be acres. Of this amount, acres are tributary to Soldiers Creek and will be treated at the northern inflow treatment site. Each of the sub-basin areas outlined on Figure 4-1 discharge to a single waterbody or conveyance channel within the overall Soldiers Creek basin area. These sub-basin areas were further delineated by Pegasus to assist in estimation of pollutant loadings and removal processes. An overview of sub-basin delineations and associated ID numbers, along with significant conveyance pathways, is given on Figure 4-2. The delineations indicated on this figure are used to model hydrologic and pollutant loadings generated throughout the area Land Use Land use information for the Soldiers Creek drainage basin was obtained by ERD from the St. Johns River Water Management District (SJRWMD) GIS database which is based upon a 2004 aerial survey. The information obtained from SJRWMD was reviewed by ERD and compared with 2008 aerial photographs to identify changes in land use characteristics between the 2004 survey and current conditions. Modifications were made by ERD to the land use data set, as necessary, to reflect existing conditions within the basin. The land use data were obtained from SJRWMD in the form of Level III FLUCCS (Florida Land Use, Cover, and Forms Classification System) codes which reflect a very detailed breakdown of land use characteristics. Although valuable for planning purposes, the detail generated by a Level III classification scheme is beyond the level for which nonpoint source characterization data are typically available. In general, prior research in the State of Florida has been performed on a limited number of general land use categories, such as low-density residential, medium-density residential, high-density residential, low-intensity commercial, highintensity commercial, industrial, highway/transportation, agriculture/pasture, agriculture/citrus, agriculture/row crops, general agriculture, open space/rangeland, mining/extractive, wetlands, and open water/lakes. Since the primary objective of this project is to develop estimates of nonpoint loadings from Soldiers Creek, it is most useful to group the detailed Level III land use categories together into general categories for which loading rate information is available. Each of the Level III land use classifications was assigned to a general land use category based upon anticipated similarities in runoff characteristics between land areas represented by the different FLUCCS codes and the general land use categories for which loading rate data are currently available. A summary of land use categories and corresponding Level III classifications assigned to each general land use category is given in Table 4-1. The 11 general groupings summarized in Table 4-1 are used for evaluation of loadings from the Soldiers Creek sub-basins.

51 µ LMB-004 LMB-002 LMB-006 LMB-005 LMB-009 LMB-007 LMB-001 LMB-003 LMB-008 LMB-010 LLM-013 NP-001 GL-003 GL-004 GL-005 GL-028 GL-007 LLM-001 GL-006 GL-030 GL-008 GL-031 GL-029 GL-009 GL-034 GL-010 GL-035 GL-036 LLM-014 GL-011 Greenwood Lake GL-033 GL-032 GL-038 GL-039 LLM-002 GL-040 LLM-015 GL-012 GL-014 GL-037 LLM-003 GL-013 GL-016 GL-015 GL-017 GL-041 LLM-004 LLM-005 LLM-016 RRB-001 CCR-001 LM-002 LM-003 Myrtle Lake LM-001 LM-006 LM-005 LM-010 LM-007 LM-011 GL-001 GL-002 LM-004 LM-013 LM-014 GL-020 GL-021 GL-024 GL-023 GL-026 GL-018 GL-027 GL-049 GL-022 GL-025 GL-019 GL-042 GL-044 GL-043 GL-045 GL-046 LLM-009 GL-047 LLM-010 GL-048 LLM-008 LLM-007 LLM-019 LLM-011 LLM-006 Geoffrey Lake RRB-007 LLM-017 LLM-018 RRB-002 RRB-003 RRB-004 RRB-005 RRB-010 RRB-009 RRB-012 RRB-008 RRB-011 RRB-006 CCR-003 CCR-007 RRB-013 CCR-002 CCR-004 CCR-005 CCR-006 LM-008 LM-012 LM-009 LM-015 LLM-012 LM-016 LT-001 ML-001 LM-017 LM-018 WL-003 BMR-003 WL-004 WL-002 WL-005 BMR-002 BMR-004 WL-008 WL-006 WL-007 BMR-001 WL-001 WL-009 EL-008 EL-013 Searcy Lake Mud Lake EL-009 LS-001 EL-001 EL-012 EL-011 EL-010 LS-002 LS-009 EL-006 LS-004 EL-003 EL-005 LS-003 LS-008 EL-007 LS-005 EL-002 EL -004 LS-007 LS-006 BMR-006 BMR-005 Ruth Lake NL-001 Legend Closed Sub-Basins Basin Boundaries Sub Basins Lakes Stream Pipe Channel Wetlands Stormwater Ponds Dry Pond Wet Pond 3,000 1, ,000 6,000 9,000 Feet Figure 4-2. Sub-basin ID Numbers and Significant Conveyance Pathways for Soldiers Creek. (SOURCE: Pegasus Engineering, LLC - July 2010) 4-4

52 4-5 GENERAL LAND USE CATEGORY TABLE 4-1 GENERAL LAND USE CATEGORIES AND CORRESPONDING LEVEL III CLASSIFICATIONS FLUCCS CODE DESCRIPTION FLUCCS CODE Agriculture Cropland and Pasture 210 Commercial Commercial and Services Communications Utilities Industrial Industrial 150 Transportation Transportation 810 Low-Density Residential Residential Low-Density < 2 Dwelling Units/Acre 110 Medium-Density Residential Residential Medium-Density 2->5 Dwelling Units/Acre 120 High-Density Residential Residential High-Density 130 Institutional Institutional 170 Recreational Recreational 180 Open Disturbed Land Hardwood Conifer Mixed Mixed Rangeland Open Land Other Open Lands (Rural) Pine Flatwoods Shrub and Brushland Upland and Coniferous Forest Wetland Bay Swamps Cypress Emergent Aquatic Vegetation Freshwater Marshes Mangrove Swamps Saltwater Marshes Stream and Lake Swamps (Bottomland) Wet Prairies Wetland Coniferous Forests Wetland Forested Mixed A complete listing of land use characteristics for each of the delineated sub-basin areas on Figure 4-2 is given in Appendix B.1. A general overview of land use in the Soldiers Creek drainage basin is given on Figure 4-3, with a tabular summary of land use characteristics given on Table 4-2. The largest land use category within the Soldiers Creek drainage basin is singlefamily residential which comprises approximately 35.7% of the total area. Approximately 17.8% of the basin area is covered by wetlands, with 10.2% of the basin area in commercial activities. All of the remaining listed land use categories occupy 9% or less of the total basin area. Overall, residential land use occupies approximately 51.3% of the Soldiers Creek basin area.

53 4-6 µ Legend Closed Sub-Basins Basin Boundaries Agriculture Commercial Industrial Institutional Open Recreational Low Density Single Family High Density Transportation Water Wetlands 3,000 1, ,000 6,000 9,000 Feet Figure 4-3. Land Use in the Soldiers Creek Basin (SOURCE: SJRWMD) Soil Types Information on soil types within the Soldiers Creek drainage basin was obtained by ERD from the SJRWMD GIS database. These data are presented in the form of Hydrologic Soil Groups (HSG) which classifies the different soil group types with respect to runoff producing characteristics. A summary of the characteristics of each hydrologic soil group is given in Table 4-3. The chief consideration in each of the soil group types is the inherent capacity of bare soil to permit infiltration. A summary of the hydrologic soil groups in the Soldiers Creek drainage basin is given in Table 4-4.

54 4-7 LAND USE CATEGORY TABLE 4-2 LAND USE IN THE SOLDIERS CREEK DRAINAGE BASIN SOLDIERS CREEK INFLOW Percent Area of Total (acres) (%) SOUTHERN INFLOW 1 Area (acres) Percent of Total (%) Area (acres) OVERALL Percent of Total (%) Low-Density Residential Single-Family Residential Multi-Family Residential Commercial Institutional Industrial Transportation Agriculture Recreational Open Spaces Wetlands Open Water TOTAL: Sub-basins CCR-007 and RRB-013 TABLE 4-3 CHARACTERISTICS OF SCS HYDROLOGIC SOIL GROUP CLASSIFICATIONS SOIL GROUP DESCRIPTION RUNOFF POTENTIAL INFILTRATION RATE A Deep sandy soils very low high Shallow sandy soils a. High in natural state b. Low after development B/D C Sandy soil with high clay or organic content medium to high a. Low in natural state b. High after development D Clayey soils very high low to none W Wetland or hydric soils low

55 4-8 TABLE 4-4 HYDROLOGIC SOIL GROUPS IN THE SOLDIERS CREEK DRAINAGE BASIN HYDROLOGIC SOIL GROUP AREA (acres) PERCENT OF TOTAL (%) A C D W TOTAL: A graphical summary of hydrologic soil groups in the Soldiers Creek drainage basin is given on Figure 4-4. Upland portions of the drainage basin appear to have soils in Hydrologic Soil Group (HSG) A which consist of deep sandy soils with a low runoff potential and a high infiltration rate. Lower portions of the drainage basin, particularly in the vicinity of wetlands, appear to have soils in HSG D which consist of clayey or silty soils with a high runoff potential and a low infiltration rate. The soil characteristics illustrated on Figure 4-4 were used in development of hydrologic characteristics for the NPSLM model. A complete listing of soil characteristics for each of the identified sub-basin areas indicated on Figure 4-2 is given in Appendix B Stormwater Management The NPSLM model incorporates attenuation factors for removal of runoff volume and mass loadings as a result of treatment in stormwater management systems located within the drainage basin. A delineation of existing stormwater management systems within the Soldiers Creek drainage basin was conducted by Pegasus, based upon a review of high resolution aerial photography for the basin, and provided to ERD. For this analysis, stormwater management systems are sorted into two categories, dry ponds and wet ponds, which are the most popular stormwater management systems utilized within the State of Florida. If other types of stormwater management systems were identified within the study area, these systems are grouped into one of the two designated categories based upon similarities in anticipated pollutant removal efficiencies. It was not feasible to determine whether the dry ponds within the basin were constructed as dry retention or dry detention stormwater management systems. However, since most of the dry ponds are located in areas with highly permeable soils, this analysis assumes that the existing dry ponds function primarily as infiltration systems and are assigned attenuation factors appropriate for dry retention systems. An overview of drainage basin areas treated by stormwater management systems in the Soldiers Creek drainage basin, based on information provided by Pegasus, is given in Figure 4-5. Wet ponds appear to be the most common stormwater technique within the basin, most of which are associated with recent development. A substantially smaller number of developments utilize dry ponds for stormwater treatment, most of which are located in western portions of the basin.

56 4-9 µ Legend Closed Sub-Basins Basin Boundaries Hydrologic Soil Group A C D W 3,000 1, ,000 6,000 9,000 Feet Figure 4-4. Hydrologic Soil Groups in the Soldiers Creek Drainage Basin Sewage Disposal Disposal of sanitary sewage in the Soldiers Creek drainage basin is accomplished using a combination of central sewer systems and individual septic tanks. Locations of septic tank systems in the Soldiers Creek drainage basin are indicated on Figure 4-6. The information summarized on this figure was provided to ERD by Pegasus. Large concentrations of septic tank systems are apparent in the eastern and central-western portions of the drainage basin. Residential development in the northwestern and southwestern portions of the basin appears to have been constructed with sanitary sewer systems.

57 µ LMB-004 LMB-002 LMB-006 LMB-005 LMB-009 LMB-007 LMB-001 LMB-003 LMB-010 LMB-008 LLM-013 NP-001 GL-003 GL-004 GL-005 GL-028 GL-007 LLM-001 GL-006 GL-030 GL-008 GL-029 GL-031 GL-009 GL-034 GL-010 GL-035 GL-036 LLM-014 GL-011 GL-033 GL-032 GL-038 GL-039 LLM-002 GL-040 LLM-015 GL-012 GL-014 GL-037 LLM-003 GL-013 GL-016 GL-015 GL-017 GL-041 LLM-004 LLM-005 LLM-016 RRB-001 CCR-001 LM-002 LM-003 LM-001 LM-006 LM-005 LM-010 LM-007 LM-011 GL-001 GL-002 LM-004 LM-013 LM-014 GL-020 GL-021 GL-024 GL-023 GL-026 GL-018 GL-019 GL-049 GL-022 GL-025 GL-027 LLM-017 LLM-006 GL-042 GL-044 GL-043 GL-045 GL-046 GL-048 LLM-018 GL-047 LLM-008 LLM-007 LLM-019 LLM-009 RRB-007 LLM-010 LLM-011 RRB-002 RRB-003 RRB-004 RRB-005 RRB-010 RRB-006 RRB-009 RRB-012 RRB-008 RRB-011 CCR-003 CCR-007 RRB-013 CCR-002 CCR-004 CCR-005 CCR-006 LM-008 LM-012 LM-009 LM-015 LLM-012 Legend LM-016 LM-017 LM-018 WL-003 WL-004 WL-002 WL-005 BMR-003 BMR-006 BMR-005 Basin Boundaries Sub Basins Closed Sub-Basins LT-001 WL-006 WL-007 BMR-002 WL-008 BMR-001 WL-001 BMR Year Storm Treatment Lakes WL-009 EL-008 Pipe EL-013 Stream LS-002 LS-001 EL-009 EL-001 EL-012 EL-011 EL-010 NL-001 Channel Dry Pond ML-001 LS-009 EL -006 EL-005 LS-004 EL -003 LS-003 LS-008 LS-005 EL-002 EL -004 LS-007 LS-006 EL-007 Wet Pond Areas Treated by Wet & Dry Ponds Areas Treated by Dry Pond Areas Treated by Wet Ponds 3,000 1, ,000 6,000 9,000 Feet Figure 4-5. Overview of Drainage Basin Areas Treated by Stormwater Management Systems in the Soldiers Creek Drainage Basin. (SOURCE: Pegasus Engineering, LLC - July 2010) 4-10

58 4-11 Figure 4-6. Locations of Septic Tank Systems in the Soldiers Creek Drainage Basin. (SOURCE: Pegasus Engineering, LLC - July 2010)

59 Hydrologic Characteristics Hydrologic characteristics of the Soldiers Creek drainage basin were evaluated by Pegasus and provided to ERD for use in modeling runoff discharges from each of the identified sub-basin areas. Information provided by Pegasus included the impervious percentage associated with each land use FLUCCS code within the basin, along with an estimate of the directly connected impervious area (DCIA). Impervious percentage assumptions ranged from 0% for open land to 100% for lakes. Pervious area curve numbers were also provided for the identified hydrologic soil groups within Soldiers Creek basin. A complete listing of hydrologic data provided by Pegasus is given in Appendix B.3. A summary of information provided to ERD by Pegasus is given on Table 4-5. TABLE 4-5 HYDROLOGIC CHARACTERISTICS OF IDENTIFIED LAND USE TYPES IN THE SOLDIERS CREEK DRAINAGE BASIN PERVIOUS CURVE NUMBERS LAND USE % % FLUCCS DEFINITION IMP. DCIA HSG HSG HSG HSG HSG A B C D W Low-Density Residential (<2 DU/acre) Medium-Density Residential (2-5 DU/acre) High-Density Residential (>6 DU/acre) Commercial and Services Cemeteries Institutional Religious Medical and Health Care Governmental Parks Open Land Nurseries and Vineyards Horse Farms Upland Forests Lakes Reservoirs (Normally Dry) 530a Reservoirs (Normally Wet) 530b Wetland Forested Mixed Vegetated Non-Forested Wetlands Wet Prairies Roads and Highways Communications Electrical Power Facilities Electrical Power Transmission Lines Water Supply Plants Sewage Treatment

60 4-13 The information summarized in Table 4-5 was used by ERD to develop individual hydrologic characteristics for each land use category in each of the individual drainage sub-basin areas. This method of analysis includes variability in hydrologic characteristics for land use categories throughout the entire basin and was used as input into the NPSLM model to estimate hydrologic and pollutant loadings. 4.2 NPSLM Model Organization The NPSLM model is used to estimate hydrologic and nutrient loadings generated within the Soldiers Creek basin. A flow chart of NPSLM is presented in Figure 4-7. The model is organized into four computation modules: (1) runoff volume generation; (2) runoff volume attenuation; (3) pollutant load generation; and (4) pollutant load attenuation. The runoff volume generation module calculates the total annual runoff volume generated in each land use parcel for each sub-basin evaluated by the model. The runoff volume attenuation module applies attenuation factors to account for losses of runoff volume in stormwater and conveyance systems, if applicable. The pollutant load generation module calculates the generated loads for total nitrogen, total phosphorus, and total suspended solids (TSS). The pollutant load attenuation module applies attenuation factors to account for losses of pollutant loadings resulting from stormwater treatment and uptake or removal during migration through conveyance systems. The generated runoff volume is calculated incrementally using a frequency distribution of typical rainfall events over an average annual cycle and 11 land use categories subdivided into five hydrologic soil group categories (including the water category). The generated runoff volume is summarized by land use and sub-basin and passed to the runoff volume attenuation and the pollutant load modules. The pollutant loads are then passed to the pollutant attenuation module. The model incorporates losses of water volume and pollutant mass in stormwater treatment systems by multiplying attenuation factors, specific for each type of treatment system, times the generated runoff volumes and generated pollutant loads for each sub-basin and land use combination. The NPSLM Model contains an additional module that can be used to estimate reductions in runoff volume and pollutant loadings which may occur in significant conveyance systems used to transport the stormwater from the point of generation to the final receiving waterbody. Examples of conveyance systems which may provide additional removal of both runoff volume and pollutant loadings include canals or streams, significant wetland areas, or small lakes and ponds which are part of the overall drainage conveyance system. After evaluating the Soldiers Creek drainage basin, it appears that there is little significant conveyance attenuation since much of the larger conveyance systems consist of shallow earthen channels General Input Data Input data for the NPSLM Model is contained in a worksheet labeled Parameters. The Parameters worksheet is organized into a series of six tables that include information on rainfall frequency distribution, the types of stormwater management systems utilized for each basin, attenuation factors for estimation of the volume of stormwater runoff and mass of pollutant load retained in stormwater management systems, conveyance system attenuation factors for the volume of stormwater runoff and pollutant load attenuated by the primary conveyance systems for each watershed, typical stormwater runoff concentrations for each of the 11 land uses, and overall weighted basin attenuation from stormwater management systems.

61 4-14 Input from GIS Rainfall Frequency Distribution Hydrologic Parameters Runoff Volume Module Typical Land Use Pollutant Concentrations Pollutant Load Generation Stormwater Management System Efficiencies Runoff Volume Attenuation Module Stormwater Management Attenuation Factors Pollutant Load Attenuation Runoff Volume Attenuation Module Conveyance System Attenuation Factors Pollutant Load Attenuation Sub-Basin Loadings Summary Figure 4-7. Flow Diagram of the NPSLM Model.

62 Rainfall Frequency Distribution A summary of the rainfall frequency distribution used for estimation of annual runoff volumes is given in Table 4-6. The rainfall frequency distribution is based on typical historical rainfall events in the Sanford area which is assumed to reflect the distribution of rain events under average rainfall conditions. This rainfall frequency distribution is a statistical analysis of historical hourly rainfall data collected from the Sanford meteorological station over the period from which was obtained from the National Climatic Data Center (NCDC). For purposes of this analysis, a rainfall event is defined as any period of continuous rainfall separated by dry conditions of three or more hours. The rainfall distribution represented in Table 4-6 is based on an annual average rainfall of inches per year. TABLE 4-6 RAINFALL FREQUENCY DISTRIBUTION FOR THE SOLDIERS CREEK MODEL RAINFALL EVENT RANGE (inches) RAINFALL INTERVAL POINT (inches) NUMBER OF ANNUAL EVENTS IN RANGE > Stormwater Management Stormwater runoff volume and pollutant loading attenuation factors were generated for each type of stormwater management system. The stormwater management system attenuation factors range from 0 to 1.0, with 0 being no attenuation and 1.0 indicating full attenuation. A summary of assumed attenuation factors for runoff volume, total nitrogen, total phosphorus, and TSS in stormwater management systems in the Soldiers Creek drainage basin is given in Table 4-7. Values summarized in this table were obtained from the publication by Harper (1995) titled Pollutant Removal Efficiencies for Typical Stormwater Management Systems in Florida which summarizes existing research on the effectiveness of stormwater management systems used in the State of Florida. For purposes of this evaluation, the removal and attenuation factors summarized in Table 4-7 are assumed to reflect attenuation factors which occur for stormwater management systems in the Soldiers Creek drainage basin. Attenuation in stormwater management systems is calculated based on the developed area treated by various stormwater management systems within each basin and the attenuation capacity of each system type.

63 4-16 TABLE 4-7 ASSUMED ANNUAL ATTENUATION FACTORS FOR TYPICAL STORMWATER MANAGEMENT SYSTEMS SYSTEM TYPE VOLUME TOTAL N TOTAL P TSS Dry Pond Wet Pond Conveyance Attenuation A summary of assumed conveyance system attenuation factors used in the NPSLM model is given in Table 4-8. The conveyance system attenuation factors represent the fraction of runoff volume and pollutant load attenuated within significant conveyance systems. The conveyance system attenuation factors can range from 0 to 1.0, with 0 representing no attenuation and 1.0 indicating full attenuation. PARAMETER TABLE 4-8 ASSUMED CONVEYANCE SYSTEM LOSSES FOR THE SOLDIERS CREEK DRAINAGE BASIN VOLUME TOTAL N TOTAL P TSS Wetland Losses Lake Losses No significant volumetric losses are assumed for wetland systems or lakes which function primarily as conveyance mechanisms. The Soldiers Creek drainage basin system appears to generate a considerable amount of baseflow which suggests that it is more likely that volumetric inputs occur into wetlands and lakes rather than volumetric losses. This issue is addressed in a subsequent section. However, wetlands are assumed to result in a 25% load reduction for total nitrogen, with a 10% load reduction for total phosphorus and 60% for TSS. Lake systems are assumed to remove approximately 35% of the total nitrogen loading, with a 50% reduction for total phosphorus and 80% reduction for TSS. This information is used in the NPSLM model as an additional loss component.

64 Stormwater Characteristics The NPSLM model uses literature-based stormwater pollutant concentrations for the land use categories used in the model. All pollutant concentrations are in mg/l and are applied globally for all basins. Pollutant concentration information was obtained from literature-based values suggested by Harper and Baker (2007), as summarized in the report titled Evaluation of Stormwater Treatment in the State of Florida. A summary of runoff characterization data used for this project is given in Table 4-9. TABLE 4-9 TYPICAL STORMWATER RUNOFF CONCENTRATIONS FOR VARIOUS LAND USES 1 TYPICAL RUNOFF CONCENTRATION LAND USE CATEGORY (mg/l) Total N Total P TSS Low-Density Residential Medium-Density Residential High-Density Residential Institutional Commercial Industrial Transportation Agriculture Recreational Open Space Wetlands Water Harper, H.H. and Baker, D.M. (2007). Evaluation of Current Stormwater Design Criteria within the State of Florida. Final Report submitted to the Florida Department of Environmental Protection for Agreement SO Groundwater Seepage In addition to inputs from stormwater runoff, wet stormwater ponds and lakes can also receive significant volumetric and nutrient inputs from groundwater seepage. Groundwater seepage is defined as shallow groundwater which migrates horizontally from upland areas into receiving waterbodies. This shallow groundwater seepage reflects infiltrated rainfall which migrates through the ground in the surficial aquifer.

65 4-18 Extensive seepage characterization studies have been conducted by ERD in more than 35 lakes within the State of Florida. From these evaluations, the typical seepage inflow is equivalent to approximately 2.0 ft of water per year over the area of the surface waterbody. Seepage inputs have also been characterized by a mean total nitrogen concentration of approximately 3 mg/l and a mean total phosphorus concentration of approximately 0.25 mg/l. A summary of typical seepage characteristics is given in Table TABLE 4-10 TYPICAL SEEPAGE CHARACTERISTICS FOR WATERBODIES IN FLORIDA 1 VOLUME (ft/yr) TOTAL N (mg/l) TOTAL P (mg/l) TSS (mg/l) SOURCE: ERD The NPSLM model assumes that a volumetric seepage inflow equivalent to 2 ft over the surface area of each waterbody occurs each year in addition to inputs from stormwater runoff. This seepage inflow has the chemical characteristics estimated in Table This additional loading is added to each receiving waterbody which is combined with loadings from stormwater runoff and the combined loading is attenuated for both volume and nutrient loadings, as discussed in a subsequent section Runoff Volume Calculation Module Annual runoff volumes are calculated for each hydrologic soil group and land use combination using the rainfall frequency distribution data summarized in Table 4-6. Information on land use areas, percent impervious areas, percent of the impervious area that is DCIA, and a curve number for each pervious land use and hydrologic soil group combination is entered directly into the Runoff Volume Calculation worksheet for each contributing sub-basin area. The SCS curve number methodology is used to provide estimates of the runoff volumes generated within each delineated drainage sub-basin area for the typical rainfall events listed in Table 4-6. The SCS methodology utilizes the hydrologic characteristics of the drainage basin, including impervious area, directly connected impervious area, and soil curve numbers to estimate runoff volumes for modeled storm events. The runoff volume for each rainfall interval is calculated by adding the rainfall excess from the non-dcia portion of each land use-hydrologic soil group combination to the rainfall excess created from the DCIA portion of the same land use-hydrologic soil group. Rainfall excess from the non-dcia areas is calculated using the following set of equations:

66 4-19 ndcia CN = (CN * IMP) + 98 (IMP (100 - DCIA) - DCIA) Soil Storage, S = 1000 ( ndcia CN) - 10 Q ndcia i = 2 ( Pi - 0.2S ) ( Pi + 0.8S) where: CN = curve number for pervious area Imp = percent impervious area DCIA = percent directly connected impervious area ndcia CN = curve number for non-dcia area P i = rainfall event interval (in) Q ndciai = rainfall excess for non-dcia for rainfall event interval (in) For rainfall events where P i is less than 0.1, the rainfall excess (Q ndciai ) is assumed to be zero. For the DCIA portion, rainfall excess is calculated using the following equation: Q DCIA i = ( P i - 0.1) When P i is less than 0.1, Q DCIAi is equal to zero. The total volume for a rainfall event interval is calculated using the following equation: RO i = [ Q ndcia i x A x (100 - DCIA)+ Q DCIA i x A x DCIA] x 1 12 x x N

67 4-20 where: A = area for specific land use-hsg (ac) RO i = runoff volume for rainfall interval (ac-ft) N = number of annual runoff events in interval The sum of all the runoff volumes (RO i ) for each rainfall event interval is the total annual rainfall volume. The weighted basin "C" value is calculated using the following equation: Generated Volume (ac - ft/yr) Area x Total Annual Rainfall (inches) x 12 inches 1 ft The methodology outlined previously provides an estimate of the generated runoff volume for each sub-basin area. However, significant portions of the generated runoff volume may be attenuated during migration through stormwater management systems within each sub-basin area. If the stormwater management system provides dry retention treatment, a large portion of the runoff volume may be infiltrated into the ground and not reach the receiving water as a surface flow. If the stormwater system provides wet detention treatment, a portion of the generated runoff volume may be lost due to evaporation within the pond or infiltration through the pond bottom. The NPSLM model includes estimates of the types of stormwater management systems utilized within each sub-basin area and the amount of developed area treated by each stormwater management type, and the attenuated volume is subtracted from the generated volume within each sub-basin. The result is an estimate of the runoff volume which discharges from each contributing sub-basin area into the larger conveyance systems Runoff Volume Attenuation Module Attenuation in stormwater management systems is calculated based on the fraction of various stormwater management systems within each sub-basin and the attenuation capacity of each system type. The Soldiers Creek NPSLM model uses two typical stormwater management systems, dry pond and wet pond. The typical attenuation factors for these systems are shown in Table 4-7. The stormwater management system attenuation volume is obtained using the following relationship: Q r =[(F 1 * E 1 ) + (F 2 * E 2 ) + (F 3 * E 3 )] * Q g

68 4-21 where: Q r = Stormwater runoff volume retained in stormwater system (ac-ft/yr) Q g = Stormwater Runoff Volume generated by all developed land uses (ac-ft/yr) F 1 = Fraction of basin treated by stormwater management system type1 (decimal 0-1) F 2 = Fraction of basin treated by stormwater management system type 2 (decimal 0-1) F 3 = Fraction of basin treated by stormwater management system type 3 (decimal 0-1) E 1 = E 2 = E 3 = Stormwater runoff volume attenuation factor for stormwater management system type 1 (decimal 0-1) Stormwater runoff volume attenuation factor for stormwater management system type 2 (decimal 0-1) Stormwater runoff volume attenuation factor for stormwater management system type 3 (decimal 0-1) The difference between the generated runoff volume and the volume attenuated in the stormwater systems reflects the volume which is discharged to the conveyance system. The volume lost in the conveyance system is estimated by using individual conveyance attenuation factors for each basin with significant conveyance systems. The volumetric conveyance attenuation factors can range from 0 to 1, with 0 being no attenuation and a value of 1 indicating full attenuation of the generated runoff volume within a given sub-basin. The volume loss in the conveyance system is calculated by multiplying the volume discharged to the conveyance system by the conveyance attenuation factors (summarized in Table 4-8). The discharge from the basin to the receiving water is the difference between the volume discharged to the conveyance system and the volume lost in the conveyance system. However, no volumetric attenuation is assumed for wetlands or lakes used as conveyance mechanisms in the Soldiers Creek basin Pollutant Load Generation The Loading worksheet calculates the total generated pollutant load for each basin and attenuates the loads based on stormwater management systems and conveyance systems within the basin. Typical pollutant runoff concentrations for each of the land uses are used to calculate the generated total pollutant load for each basin. The generated pollutant loads are calculated using the generated stormwater volume for each land use and the typical stormwater pollutant concentrations summarized in Table 4-9 from Harper and Baker (2007). The generated pollutant loads are attenuated in a manner similar to the procedure used for attenuation of runoff volumes in the runoff volume attenuation sheet. The following equation is used to calculate the load retained in the stormwater system for each pollutant:

69 4-22 M r = [(F 1 * E 1 ) +(F 2 * E 2 ) + (F 3 * E 3 ) + (F 4 * E 4 )] * M g where: M r = M g = Pollutant load retained in stormwater system (kg/yr) Pollutant load generated by all developed land uses (kg/yr) F 1 = Fraction of developed basin area treated by stormwater management system type 1 (decimal 0-1) F 2 = Fraction of developed basin area treated by stormwater management system type 2 (decimal 0-1) F 3 = Fraction of developed basin area treated by stormwater management system type 3 (decimal 0-1) F 4 = Fraction of developed basin area treated by stormwater management system type 4 (decimal 0-1) E 1 = Removal efficiency for stormwater management system type 1(decimal 0-1) E 2 = Removal efficiency for stormwater management system type 2 (decimal 0-1) E 3 = Removal efficiency for stormwater management system type 3 (decimal 0-1) E 4 = Removal efficiency for stormwater management system type 4 (decimal 0-1) The difference between the total generated load and the load retained in the stormwater management system is referred to as the Load Entering Conveyance Systems. The load removed by the conveyance system is calculated for each sub-basin using the following equation: where: M c = (M g M r ) * R ci M c = Pollutant load retained in conveyance system (kg/yr) R ci = Conveyance system removal efficiency of Sub-basin i (decimal 0-1) The total load discharged to the proposed treatment system site is calculated as the difference between the load entering the conveyance system and the load removed by the conveyance system.

70 Nonpoint Source Loading Estimates The NPSLM Model was used to generate estimates of annual volumetric discharges and mass loadings of total nitrogen, total phosphorus, and TSS from identified sub-basin areas to Soldiers Creek at the point of the proposed treatment system. However, since phosphorus is the primary nutrient of concern in Lake Jesup, loadings are presented in this section for phosphorus only. Estimates of hydrologic and mass loadings generated in the Soldiers Creek basin are given in the following sections Runoff Loadings A complete listing of output summary sheets for the NPSLM model is given in Appendix C. These summary sheets contain individual volumetric and mass loading calculations for each of the identified sub-basin areas within the Soldiers Creek area. Information is provided on volumetric and mass loadings generated as a result of stormwater runoff, groundwater seepage into ponds and lakes, direct rainfall on ponds and lakes, inflow from interconnected drainage basins, evaporation losses, losses resulting from deep recharge, and conveyance system losses. The resulting values provide estimates of loadings discharging from each sub-basin as a result of these processes. A nodal diagram for hydrologic discharges in the Soldiers Creek basin (in terms of acft/yr) is given in Figure 4-8. This diagram summarizes water movement throughout the basin (in terms of ac-ft/yr) to the point of the proposed treatment system on Soldiers Creek. Based upon this analysis, the total hydrologic discharge from Soldiers Creek into the proposed treatment pond resulting from direct stormwater runoff is approximately 3,463 ac-ft/yr. An additional 66.4 ac-ft/yr discharge into the treatment pond through the southern inflow. A nodal diagram for phosphorus discharges (in terms of kg/yr) in the Soldiers Creek basin is given in Figure 4-9. This diagram provides a summary of phosphorus movement through the basin to the point of the proposed treatment system along Soldiers Creek. Based upon this analysis, the estimated runoff generated phosphorus loading from Soldiers Creek which reaches the point of the proposed treatment system is approximately 554 kg/yr. Using the modeled runoff volume of 3463 ac-ft/yr, this loading corresponds to a mean runoff total phosphorus concentration of 133 g/l at the proposed treatment site. An additional 3.8 kg total phosphorus/year is generated in the southern basin. Using the modeled runoff volume of 66.4 ac-ft/yr, this corresponds to a mean runoff total phosphorus concentration of 92 mg/l entering the treatment pond from the southern sub-basin areas. A summary of runoff volume and annual runoff coefficient (C value) calculations for the Soldiers Creek basin is given on Table Based upon the NPSLM modeling, the acre Soldiers Creek basin (excluding closed basin areas) generates approximately 3,463 ac-ft/yr. Based upon the assumed annual rainfall of in/yr, the corresponding C value for the Soldiers Creek drainage basin is This value suggests that approximately 14% of the annual rainfall becomes stormwater runoff which discharges from the sub-basin areas. The acre southern sub-basin generates 66.4 ac-ft/yr which corresponds to an annual C value of 0.210, suggesting that 21% of the annual rainfall in this basin becomes stormwater runoff.

71 4-24 LM LS-001 LM WL-007 EL-001 GL GL ,119 WL BMR-003 GL ,206 GL LLM-009 LLM ,042 1,619 GL-006 LLM LLM-018 LLM-014 CCR-004 1,288 1, RRB-006 3,463 2,114 RRB CCR-001 CCR Runoff Discharge to 50.7 Soldiers Creek (ac-ft/yr) RRB-013 Figure 4-8. Nodal Diagram for Hydrologic Discharges (ac-ft/yr) in the Soldiers Creek Basin.

72 4-25 LM LS-001 LM WL-007 EL-001 GL GL WL BMR-003 GL GL LLM-009 LLM GL LLM LLM-018 LLM-014 CCR RRB RRB CCR-001 CCR Runoff Discharge to 5.5 Soldiers Creek (kg/yr) RRB-013 Figure 4-9. Nodal Diagram for Phosphorus Discharges (kg/yr) in the Soldiers Creek Basin.

73 4-26 TABLE 4-11 SUMMARY OF RUNOFF VOLUMES AND ANNUAL C VALUES FOR RUNOFF INPUTS TO THE PROPOSED TREATMENT POND PARAMETER UNITS SOLDIERS SOUTHERN CREEK BASIN 1 BASIN AREA Basin Area acres Annual Runoff Volume ac-ft/yr Assumed Annual Rainfall 2 in/yr Annual C Value Does not include acres of closed basins 2. Mean rainfall at Sanford meteorological station from Baseflow Loadings In addition to runoff generated volumetric and mass loadings, a significant baseflow is also present in Soldiers Creek at the proposed treatment site. This baseflow results from infiltration of groundwater into the channelized conveyance systems and general drawdown of the infiltrated rainfall throughout the basin following rain events. A summary of hydrologic measurements in Soldiers Creek conducted at the USGS gauging station downstream from the proposed treatment site (see Figure 3-3) is given on Table Annual summaries are provided for the period from , which includes average annual discharge in both cfs and ac-ft, as well as annual rainfall. Over the period from , the average annual discharge at the USGS gauging station was 9,475 ac-ft/yr, based on a mean annual rainfall of inches. However, the rainfall measured during this period is somewhat higher than the long-term average rainfall of inches/year in the Sanford area. If the mean annual volume is adjusted for a lower mean annual rainfall of inches/year, the estimated annual discharge would be 8,675 ac-ft/yr at the USGS gauging station assuming a linear relationship between rainfall and stream discharge. Since it is assumed that discharge at the project site is approximately 90% of the measurements recorded at the USGS gauging site (see Section 3.1.1), then the annual discharge at the proposed treatment site is approximately 7,808 ac-ft/yr (8,675 ac-ft/yr x 0.9). If direct runoff inputs contribute 3,463 ac-ft/yr, the volume contributed by baseflow is approximately 4,345 ac-ft/yr (7,808 ac-ft/yr - 3,463 ac-ft/yr). Estimates of nutrient concentrations in baseflow at the proposed treatment site were obtained from the field monitoring data collected at the Soldiers Creek monitoring site by ERD over the period from July-October Measured concentrations of total nitrogen and total phosphorus in Soldiers Creek samples from July-October 2010 were previously summarized in Table 3-3. As indicated on Figure 3-6, baseflow conditions within Soldiers Creek appear to occur at a discharge rate of approximately 5 cfs or less. Therefore, the chemical characteristics of baseflow in Soldiers Creek were estimated as the average of total nitrogen and total phosphorus concentrations in samples collected during periods of discharge rates of approximately 5 cfs or less. This results in an estimated baseflow total nitrogen concentration of 779 g/l, with a baseflow total phosphorus concentration of 133 g/l.

74 4-27 TABLE 4-12 SUMMARY OF HYDROLOGIC MEASUREMENTS AT THE SOLDIERS CREEK USGS GAUGING STATION (No ) YEAR AVERAGE ANNUAL DISCHARGE (cfs) ANNUAL RAINFALL (inches) ANNUAL VOLUME (ac-ft) , , , , , , , , , , , , , , , , , , , ,891 MEAN: ,475 TABLE 4-13 ESTIMATED HYDROLOGIC AND MASS LOADINGS IN BASEFLOW FROM THE SOLDIERS CREEK SUB-BASIN AREAS PARAMETER UNITS VALUE Annual Volume ac-ft/yr 4,345 Total Phosphorus Concentration g/l 133 Total Phosphorus Loading kg/yr 713

75 4-28 A summary of estimated phosphorus concentrations and mass loadings in baseflow from the Soldiers Creek sub-basin areas is given in Table 4-13 based upon the assumed annual baseflow volume of 4,345 ac-ft/yr. Based on these assumptions, baseflow from Soldiers Creek contributes approximately 713 kg/yr of total phosphorus at the proposed treatment site. Baseflow loadings are not provided for the southern sub-basin areas since baseflow from these areas is assumed to be negligible Combined Loadings A summary of runoff and baseflow discharges from the Soldiers Creek and southern subbasin areas at the proposed treatment site is given in Table Of the total estimated annual discharge of 7,808 ac-ft/yr from the Soldiers Creek sub-basins, approximately 44% is contributed by direct stormwater runoff and 56% by baseflow. The combined discharges from runoff and baseflow correspond to an annual C value of approximately for the acre basin area. The southern sub-basin area contributes approximately 50.7 ac-ft/yr of direct runoff with a C value of Baseflow from this sub-basin is assumed to be negligible. TABLE 4-14 SUMMARY OF RUNOFF AND BASEFLOW DISCHARGES FROM THE SOLDIERS CREEK AND SOUTHERN SUB-BASIN AREAS TO THE PROPOSED TREATMENT SITE BASIN PARAMETER UNITS VALUE Soldiers Creek Basin Southern Sub-basins Runoff Baseflow Total Basin C Value Runoff Baseflow Total Basin C Value ac-ft-yr ac-ft-yr ac-ft/yr -- ac-ft-yr ac-ft-yr ac-ft/yr -- 3,463 4,345 7, A summary of annual mass loadings of total phosphorus from runoff and baseflow at the proposed treatment site is given in Table Approximately 1,267 kg/yr of total phosphorus discharges through Soldiers Creek at the proposed treatment site, with 44% contributed by runoff and 56% by baseflow. It appears that baseflow is a significant contributor of total phosphorus and treatment of baseflow should be emphasized for any proposed treatment system. The southern sub-basin areas contribute approximately 5.5 kg of total phosphorus to the treatment pond each year.

76 4-29 TABLE 4-15 SUMMARY OF ANNUAL MASS LOADINGS OF TOTAL PHOSPHORUS FROM RUNOFF AND BASEFLOW AT THE PROPOSED TREATMENT SYSTEM SITE BASIN PARAMETER UNITS VALUE Soldiers Creek Basin Runoff Baseflow kg/yr kg/yr 554 (44%) 713 (56%) Total kg/yr 1,267 Southern Sub-basins Runoff Baseflow kg/yr kg/yr 5.5 (100%) 0.00 (0%) Total kg/yr 5.5

77 SECTION 5 CONCEPTUAL TREATMENT SYSTEM DESIGN AND CHARACTERISTICS 5.1 Conceptual System Design A system design was developed for the proposed Soldiers Creek treatment system jointly by Pegasus Engineering and ERD. In general, Pegasus was responsible for the civil and structural engineering portions of the conceptual design, with ERD responsible for the chemical treatment system components and control building. An overview of the proposed system design is given on Figure 5-1. A weir structure is proposed in Soldiers Creek just upstream of CR 427 to allow diversion of water into the pond. The elevation of the weir will be set to allow a maximum inflow of 50 cfs into the treatment pond. A 4-ft x 6-ft box culvert will be constructed along the northern end of the pond to convey water from Soldiers Creek into the pond for chemical treatment. The discharge rate of the inflow will be measured using an acoustic Doppler flow meter and PACl will be added to the inflow on a flow-weighted basis. A submersible water carrier pump will be used to transport a mixture of water and PACl to the point of addition to the Creek water. The mixture of PACl and water will be injected into the incoming Soldiers Creek water under high pressure to provide mixing with the stormwater. The treated water will be discharged into a linear settling trough, constructed along the northern and eastern sides of the pond. The end of the trough will be open to the pond to allow the treated water to discharge into the pond. The floc will settle onto the bottom of the trough into a sump area which contains perforated underdrain pipes. Any floc which bypasses the trough will be collected in the pond. Floc will be removed from the sump area on a daily basis by sucking the floc through the perforated pipes. The collected floc will be pumped into a series of 5 interconnected 6800-gallon storage tanks. Floc removal from the tanks will occur on an asneeded basis, with the floc transported to the Seminole County Yankee Lake facility. The existing outfall control structure will be relocated to increase the distance between the inflow of treated water from the floc collection trough and the pond discharge and to provide the required water elevations for the various operational protocols. Chemical metering pumps, electronic control equipment, and an 8000-gallon chemical storage tank will be located inside an equipment building to be constructed on the north end of the pond. Conduit lines will extend from the proposed equipment building to the point of chemical addition, to convey PACl and control system electronics. Although the laboratory jar testing described in Section 3 indicates that ph control of the treated water will not be required, a ph monitor will be incorporated into the system as a safeguard. The ph of the water will be monitored at the pond outfall on a continuous basis, and if the ph of the outfall discharge drops below 6.0, chemical addition will be discontinued until the low ph condition is corrected. 5-1

78 5-2 Figure 5-1. Proposed Conceptual Design for the Soldiers Creek Treatment System.

79 Evaluation of Treatable Discharge A probability distribution for discharge measurements in Soldiers Creek from at the USGS monitoring site downstream from the proposed treatment site is given on Figure 5-2. The figure is a normal probability plot with discharge plotted on the X-axis using an arithmetic scale. The values listed on the Y-axis indicate the probability of a given discharge being equal to or less than the stated probability. The probability relationship is curvilinear, suggesting a log-normal or similar type of distribution Probability (%) Mean Interval Discharge (cfs) Figure 5-2. Probability Distributions for Discharge Measurements in Soldiers Creek from To minimize the cost-to-benefit ratio for chemical treatment systems, the maximum treated flow rate is often selected as the discharge rate and associated probability which is near the upper end of the vertical straight-line portion of the probability curve before the curvilinear portion of the relationship begins. Discharge rates associated with portions of the line above this value require treatment of an increasingly larger discharge rate for smaller increments of the annual discharge. Based upon the relationship summarized in Figure 5-2, this portion of the probability curve appears to occur at approximately 80-90% for Soldiers Creek.

80 5-4 A summary of relationships between treated discharge rates and annual treated volumes for Soldiers Creek, based on data collected at the USGS site, is given on Table 5-1. This analysis assumes that all water discharging through Soldiers Creek, up to and including the maximum treated flow rate, will be diverted into the pond for poly-aluminum chloride (PACl) treatment, with the remaining flow bypassing the system untreated. The relationships summarized in Table 5-1 were developed by simulating the historical discharge hydrographs over the period from for Soldiers Creek. All water up to the maximum treatable flow rate is assumed to be diverted into the treatment system, with the remaining discharge in excess of the maximum treatment rate allowed to bypass the system. The percentage of annual volume treated is calculated as the percentage of the total annual runoff volume which is diverted into the treatment system based upon each of the assumed maximum inflow rates. TABLE 5-1 RELATIONSHIPS BETWEEN TREATED DISCHARGE RATES AND ANNUAL TREATED VOLUMES FOR SOLDIERS CREEK MAXIMUM TREATED DISCHARGE (cfs) PERCENT OF ANNUAL VOLUME TREATED (%) Based upon the analysis summarized in Table 5-1, a maximum treated discharge rate of 50 cfs will provide treatment for approximately 85% of the annual runoff volume discharging through Soldiers Creek. However, the relationship summarized in Table 5-1 is based upon discharge measurements conducted at the USGS gauging station located downstream from the proposed Soldiers Creek treatment site. As discussed in Section 3, discharge measurements at the proposed treatment site are approximately 90% of the average daily discharge measurements recorded at the USGS gauging station. As a result, a discharge rate of 50 cfs at the USGS gauging site will correspond to a discharge rate of approximately 45 cfs at the proposed treatment site. Therefore, this analysis assumes that a maximum treated discharge of 45 cfs will provide treatment for approximately 85% of the annual volume discharged to Soldiers Creek upstream from the treatment site. Based upon the assumed annual combined volume from runoff and baseflow of 7,808 ac-ft/yr, a system designed to provide treatment for 85% of this volume will provide treatment for 6,637 ac-ft of water per year.

81 5-5 In addition to the inflows from Soldiers Creek, the existing pond system will continue to provide normal wet detention treatment for inflow from the acre sub-basin areas (including CR 427 and Church of the Nativity) which discharge into the southern portion of the pond. As indicated on Table 4-14, the southern sub-basins contribute approximately 50.7 acft/yr of runoff into the treatment pond. Since these flows are diverted directly into the pond with no potential for high level overflow or bypass, the entire 50.7 ac-ft/yr will continue to receive treatment in the pond, although no coagulant will be added. An analysis of the impacts of the proposed pond modifications on the ability of the pond to continue to provide treatment for the acre area is given in a subsequent section. 5.3 Phosphorus Load Reductions This analysis assumes that the treatment system will provide chemical treatment for all Soldiers Creek discharges, including both runoff and baseflow, up to the maximum inflow rate of 45 cfs. As discussed in Section 4.3, direct runoff contributes 3463 ac-ft/yr with an additional 4345 ac-ft/yr of baseflow. As currently designed, the system will be capable of providing PACl addition to the combined inflows from runoff and baseflow (6637 ac-ft/yr which is 85% of annual combined discharge of 7808 ac-ft/yr), with the associated combined phosphorus loading of 1077 kg phosphorus per year (85% of annual loading of 1267 kg phosphorus per year). A summary of calculated annual phosphorus load reductions by the Soldiers Creek treatment system is given on Table 5-2. This analysis assumes that the treatment system will provide treatment for discharges up to and including 45 cfs in Soldiers Creek which represents approximately 85% of the annual volume discharged through Soldiers Creek. Based upon laboratory jar testing summarized in Section 3.3, the anticipated removal efficiency for total phosphorus at the optimum aluminum dose of 10 mg Al/liter is 93%. However, since laboratory jar tests provide an optimum environment, the laboratory-obtained removal efficiencies are reduced slightly to 90% for total phosphorus for purposes of this analysis. Based upon these assumptions, the estimated annual load reduction for total phosphorus is approximately 970 kg/yr (2137 lb/yr) from Soldiers Creek. SUB-BASIN TABLE 5-2 CALCULATED ANNUAL PHOSPHORUS LOAD REDUCTIONS BY THE SOLDIERS CREEK TREATMENT SYSTEM ANNUAL PHOSPHORUS LOADING (kg/yr) PERCENT OF ANNUAL VOLUME TREATED (%) REMOVAL BY TREATMENT SYSTEM 1 (%) ANNUAL LOAD REDUCTION Soldiers Creek 1, ,137 kg/yr lb/yr TOTAL: 970 2, Assumed value; a removal of 93% was obtained for total phosphorus during laboratory jar testing

82 Anticipated Chemical Use A summary of anticipated chemical use for the proposed Soldiers Creek treatment system is given on Table 5-3. This analysis assumes that an average annual runoff volume of approximately 6637 ac-ft/yr will be treated by the system. Based upon the laboratory jar testing summarized in Section 3, the recommended optimum PACl dose was 10 mg Al/liter. This equates to an estimated annual PACl use of 339,830 gallons. TABLE 5-3 SUMMARY OF ANTICIPATED CHEMICAL USE FOR THE PROPOSED SOLDIERS CREEK TREATMENT SYSTEM PARAMETER UNITS VALUE Mean Annual Soldiers Creek Discharge at Treatment Site ac-ft/yr 7,808 Mean Annual Volume Treated ac-ft/yr 6,637 PACl Dose mg Al/liter 10 Annual PACl Volume gallons 339, Annual Floc Production and Disposal A summary of anticipated annual floc production for the proposed Soldiers Creek treatment system is given on Table 5-4. This analysis assumes an annual treated volume of 6637 ac-ft/yr. As indicated in Table 3-7, the estimated floc generation rate at the recommended optimum PACl dose of 10 mg Al/liter is 0.43% of the treated water volume. This value reflects the likely accumulation volume of floc within the proposed settling trough. Chemical treatment of the estimated annual volume will generate approximately 28.5 ac-ft/yr of wet floc which will be discharged into the floc collection trough. This is equivalent to approximately 1,243,163 ft 3 /yr or approximately 25,476 gallons/day. After drying, the floc undergoes a considerable volume reduction with the dried residual representing approximately 2% of the wet floc volume. Based upon this assumption, the estimated annual volume of dried floc for disposal will be approximately 24,863 ft 3. At this time, it is anticipated that floc disposal will occur by discharging the floc on a daily basis into a series of five interconnected 6800-gallon storage tanks with a combined volume of 34,000 gallons. Floc will be automatically removed from the collection trough on a daily basis and pumped into the storage tanks. The storage tanks will be emptied on an asneeded basis and the floc will be transported in a tanker truck to the Seminole County Yankee Lake water treatment plant for dewatering. Future plans may involve direct discharge of the collected floc into an adjacent Seminole County sanitary sewer lift station.

83 5-7 TABLE 5-4 SUMMARY OF ANTICIPATED ANNUAL FLOC PRODUCTION FOR THE PROPOSED SOLDIERS CREEK TREATMENT SYSTEM Floc Production in Pond Floc Production Dried PARAMETER UNITS VALUE Annual Volume Treated ac-ft/yr 6,637 a. Percent of Treated Volume % 0.43 b. Annual Volume ac-ft/yr ft 3 /yr gallons/day ,243,163 25,476 a. Percent of Wet Volume % 2 b. Annual Volume ft 3 24,863 A cross-sectional schematic of the proposed floc collection trough is given on Figure 5-3. The collection trough will be constructed using sheet pile sections, with the vertical sheet pile section adjacent to the open water portions of the pond, and the sloped section of the trough incorporated into the existing pond side bank. The floc collection trough is approximately 466 ft in length, with a cross-sectional area of 363 ft 2 at the proposed water surface elevation of 20.0 ft (NGVD) within the pond when operated under the chemical treatment plan. The corresponding water volume contained within the floc collection trough is 169,158 ft 3. CWL (elev. 20 ft) Pond Bottom Figure 5-3. Cross-sectional Schematic of the Proposed Floc Collection Trough.

84 5-8 As discussed previously, the proposed maximum inflow rate to the Soldiers Creek treatment system is 50 cfs. At this maximum inflow rate, the trough floc collection system will provide a mean detention time of approximately one hour (56 minutes). The laboratory jar tests conducted by ERD indicated that at an aluminum dose of 10 mg Al/liter, the PACl floc settled rapidly with virtually complete floc settling in minutes. Therefore, virtually all of the generated floc should be collected within the floc collection system even for the design inflow treatment event. Any floc which bypasses the trough collection system will settle into the sediments of the wet detention pond. 5.6 Operation and Maintenance Chemical stormwater treatment systems require periodic inspection, calibration, and maintenance to ensure continued proper operation of the system. Although previously constructed chemical treatment facilities have been extremely reliable, routine operation and maintenance is a necessary component of any mechanical system. Routine maintenance procedures will be required on a weekly basis, while more comprehensive technical reviews should be conducted on a quarterly basis. This combination of weekly and quarterly maintenance will ensure dependable functioning of the treatment system Weekly Maintenance Weekly maintenance procedures have been designed to be easily completed by the owner s designated trained technician, including those with little pre-existing experience with chemical feed systems. Training of selected personnel in operation and maintenance requirements will be conducted by the design engineer and the instrumentation specialists during the initial system start-up operations. Responsibilities of the trained technician are documented on the Weekly Treatment System Checklist summarized on Table 5-5, and includes the following: PLC Status Check (to confirm the operations of the Programmable Logic Controller system) Stormwater Meter Check (to confirm stormwater flow sensor signal operations) System Simulation (to confirm the calibration of the chemical pumping rates) ph System Check (to confirm ph sensor calibrations) Tank Volume Check Tank and Piping Leak Check General Housekeeping and Security Quarterly Maintenance A more detailed inspection of the chemical treatment system will be conducted on a quarterly basis. The quarterly maintenance service includes a comprehensive review of the instrumentation and piping components of the treatment system. This review is much more indepth than the weekly visits, and focuses on inspection, calibration, and preventative maintenance of the numerous electronic components.

85 5-9 TABLE 5-5 WEEKLY TREATMENT SYSTEM CHECKLIST NAME: DATE: TIME: 1. PLC STATUS CHECK CONTROL POWER light on? Yes No CHEMICAL FEED PUMP ON light on? Yes No Current Stormwater Flow: cfs Current Chemical Flow: gpm Total Treated Stormwater Flow: mcf 2. STORMWATER METER CHECK Sensor: Signal Gain # of Bars Totalizer Reading: Message on Display: 3. SYSTEM SIMULATION - Simulate Storm Flow using Storm Flow Meter At 50% flow, pump panel flow reads cfs At 100% flow, pump panel flow reads cfs 4. CHECK FOR ANY LEAKS IN TANK, PIPING, AND/OR PUMP (including rank room) Yes 5. CHECK WATER CARRIER PUMP FOR AUTO OPERATION Yes 6. CLEAN DEBRIS FROM WET WELL Yes 7. RECORD TANK VOLUME gallons 8. ph SYSTEM CHECK - Before Calibration Pond Reading: Meter Reading: Differential: 9. ph SYSTEM CHECK - After Calibration Pond Reading: Meter Reading: Differential: 10. DEPARTURE CHECKLIST Is system returned to AUTO mode? Yes No Do panels appear to be functional? Yes No Are pump and tank room floors swept/washed? Yes No Interior building lights turned off? Yes No Building doors locked? Yes No Fence gate locked? Yes No

86 Impacts of Pond Modifications on Existing Treatment Efficiency Under existing conditions, the Soldiers Creek wet detention pond is a permitted treatment facility for acres of highway, institutional, and residential land uses located south and west of the pond. During the pre-application meetings, the District requested an analysis of the impacts of the proposed diversion of Soldiers Creek water into the pond on the overall performance effectiveness of the system. This analysis must demonstrate that, at a minimum, the existing mass load reductions for total phosphorus and total nitrogen achieved within the pond would be maintained during periods when Soldiers Creek inflow is entering the pond. The worst case condition would occur when both the southern sub-basin areas as well as Soldiers Creek are discharging into the pond with no chemical treatment, substantially altering the pond detention time and anticipated mass load reductions. A comparison of pond characteristics under existing and proposed conditions is given on Table 5-6 based upon stage-storage relationships for the pond provided by Pegasus. Under existing conditions, the pond operates with a control water elevation of approximately 23.8 ft (NGVD) which corresponds to a permanent pool volume of ac-ft. As discussed in Section 4, the annual runoff inflow to the Soldiers Creek pond from the southern sub-basin areas is approximately 50.7 ac-ft/yr. This corresponds to a mean annual detention time of approximately 269 days within the pond. CONDITION TABLE 5-6 COMPARISON OF POND CHARACTERISTICS UNDER EXISTING AND PROPOSED CONDITIONS CONTROL WATER LEVEL (ft, NGVD) POND VOLUME (ac-ft) ANNUAL INFLOW VOLUME (ac-ft/yr) MEAN ANNUAL DETENTION TIME (days) Existing Proposed , Assumes operation as a wet detention facility 2. Operating conditions for chemical treatment Under proposed conditions, when the pond is operating in the chemical treatment mode, the water level will be controlled at an elevation of approximately 20.0 ft (NGVD) which, including the proposed pond regrading, corresponds to a permanent pool volume of ac-ft. Under these conditions, the pond will receive both the annual runoff inflow from the southern basins as well as the Soldiers Creek inflow. As discussed in Section 4, the anticipated annual inflow into the Soldiers Creek pond resulting from stormwater runoff and baseflow is approximately 6637 ac-ft/yr. When this volume is combined with the 50.7 ac-ft of runoff per year generated in the sub-basins, the total annual inflow to the pond will be approximately 6688 ac-ft/yr. This inflow volume corresponds to a mean annual detention time of approximately 1.9 days.

87 5-11 A comparison of calculated pond removal efficiencies under existing and proposed conditions is given on Table 5-7. Since the pond functions as a wet detention system, the removal efficiencies for nitrogen and phosphorus were calculated using the relationships developed by Harper and Baker (2007) which predict wet detention removal efficiencies as a function of detention time. Based upon these relationships and the calculated mean annual detention times (summarized in Table 5-7), the wet detention pond would be expected to have a removal efficiency of approximately 82% for total phosphorus and 43% for total nitrogen under existing conditions. Under the proposed conditions, which reduce the mean annual detention time to only 1.9 days, the calculated total phosphorus removal efficiency will be approximately 44%, with a 13% removal for total nitrogen. TABLE 5-7 COMPARISON OF CALCULATED POND REMOVAL EFFICIENCIES UNDER EXISTING AND PROPOSED CONDITIONS CONDITION MEAN ANNUAL DETENTION TIME (days) CALCULATED REMOVAL EFFICIENCY (%) 1 ASSUMED REMOVAL EFFICIENCY (%) 2 Total P Total N Total P Total N Existing Proposed Based on wet detention removal efficiency curves by Harper and Baker (2007) 2. Assumed wet detention removal efficiencies based on water quality characteristics However, the removal efficiency curve developed by Harper and Baker reflect removal efficiencies for raw stormwater runoff in wet detention ponds. Unfortunately, Soldiers Creek water (summarized on Table 3-3) exhibits lower concentrations and a substantially different distribution for the measured species of nitrogen and phosphorus. For example, approximately 50% of the measured concentrations of total nitrogen and total phosphorus in raw stormwater is contributed by particulate forms. Based upon the geometric mean values summarized at the bottom of Table 3-3, particulate phosphorus appears to represent approximately 20-30% of the total concentrations of both nitrogen and phosphorus. The relatively low observed concentrations of particulate species reflects attenuation of runoff generated particulate matter in upstream portions of the extensive Soldiers Creek drainage system. Since much of the initial mass removal of nitrogen and phosphorus which occurs in wet detention ponds is due to settling of particulate matter, a much lower removal efficiency would be anticipated within a wet detention pond which receives reduced levels of suspended solids. In addition, the inflow from Soldiers Creek is highly colored in comparison to stormwater runoff which generally exhibits little or no color. A number of color-generating compounds have been demonstrated to exhibit inhibitory effects on biological productivity in aquatic systems, which would reduce the ability of the biological community to remove dissolved forms of nitrogen and phosphorus.

88 5-12 Since it appears likely that the calculated removal efficiencies for the Soldiers Creek pond overestimate the actual pond effectiveness, a reduced level of removal efficiency is assumed for nitrogen and phosphorus as part of this analysis. Due to the conditions described previously, removal efficiencies for total phosphorus and total nitrogen under existing conditions are reduced to 50% and 25%, respectively. Under the proposed conditions, a removal efficiency of 25% is assumed for total phosphorus, with an assumed removal efficiency of 10% for total nitrogen. A comparison of pond mass removals under existing and proposed conditions is given on Table 5-8. The removal efficiencies are based upon the existing mass loadings to the wet detention pond under existing conditions and under proposed conditions based upon the NPSLM model summary sheets for the Soldiers Creek basin provided in Appendix C. Under existing conditions, the Soldiers Creek pond receives an input of approximately 5.5 kg/yr of total phosphorus and 84.2 kg/yr of total nitrogen which is generated in the southern sub-basin area. Using the assumed pond removal efficiencies summarized in Table 5-7, the Soldiers Creek wet detention pond removes approximately 2.8 kg/yr of total phosphorus and 21 kg/yr of total nitrogen from Soldiers Creek. TABLE 5-8 COMPARISON OF POND MASS REMOVALS UNDER EXISTING AND PROPOSED CONDITIONS CONDITION MASS LOADING (kg/yr) ASSUMED REMOVAL EFFICIENCY (%) MASS REMOVAL (kg/yr) Total P Total N Total P Total N Total P Total N Existing Proposed 1,077 2, Under the proposed conditions, mass inputs into the pond would increase substantially, compared with existing conditions. This analysis assumes that the pond is operating under worst case conditions which would occur when Soldiers Creek inflow is directed into the pond but no chemical addition occurs. Using the assumed reduced removal efficiencies summarized in Table 5-7, the wet detention pond would still remove large annual mass loadings of total phosphorus and total nitrogen due to the increased loadings to the pond. Therefore, the permitted mass load reductions for the southern and western sub-basins will be maintained even if the pond were to operate in the proposed treatment mode without any chemical addition. In fact, under the proposed conditions, a removal efficiency of <1% is required for total phosphorus and total nitrogen to achieve the mass load reductions which occur under existing conditions.

89 APPENDICES

90 APPENDIX A RESULTS OF LABORATORY JAR TESTS ON SOLDIERS CREEK SAMPLES COLLECTED FROM JANUARY-MARCH 2013

91 Soldiers Creek Jar Test Results Sample Description Date Collected ph Alkalinity Spec. Cond. NH 3 -N NO X -N Diss. Org. N Part. N Total N SRP Diss. Org. P Part. P Total P Turbidity TSS (s.u.) (mg/l) (µmho/cm) (µg/l) (µg/l) (µg/l) (µg/l) (µg/l) (µg/l) (µg/l) (µg/l) (µg/l) (NTU) (mg/l) Raw 1/7/ mg/l 1/8/ mg/l 1/8/ mg/l 1/8/ mg/l 1/8/ mg/l 1/8/ mg/l 1/8/ Raw 1/14/ , mg/l 1/16/ mg/l 1/16/ mg/l 1/16/ mg/l 1/16/ mg/l 1/16/ mg/l 1/16/ Raw 1/23/ , mg/l 1/25/ , mg/l 1/25/ mg/l 1/25/ mg/l 1/25/ mg/l 1/25/ mg/l 1/25/ Raw 1/31/ , mg/l 2/2/ mg/l 2/2/ mg/l 2/2/ mg/l 2/2/ mg/l 2/2/ mg/l 2/2/ Raw 2/5/ mg/l 2/7/ mg/l 2/7/ mg/l 2/7/ mg/l 2/7/ mg/l 2/7/ mg/l 2/7/

92 Soldiers Creek Jar Test Results Sample Description Date Collected ph Alkalinity Spec. Cond. NH 3 -N NO X -N Diss. Org. N Part. N Total N SRP Diss. Org. P Part. P Total P Turbidity TSS (s.u.) (mg/l) (µmho/cm) (µg/l) (µg/l) (µg/l) (µg/l) (µg/l) (µg/l) (µg/l) (µg/l) (µg/l) (NTU) (mg/l) Raw 2/13/ mg/l 2/15/ mg/l 2/15/ mg/l 2/15/ mg/l 2/15/ mg/l 2/15/ mg/l 2/15/ Raw 2/20/ mg/l 2/21/ mg/l 2/21/ mg/l 2/21/ mg/l 2/21/ mg/l 2/21/ mg/l 2/21/ Raw 2/28/ mg/l 2/28/ mg/l 2/28/ mg/l 2/28/ mg/l 2/28/ mg/l 2/28/ mg/l 2/28/ Raw 3/7/ mg/l 3/10/ mg/l 3/10/ mg/l 3/10/ mg/l 3/10/ mg/l 3/10/ mg/l 3/10/ Raw 3/14/ mg/l 3/15/ mg/l 3/15/ mg/l 3/15/ mg/l 3/15/ mg/l 3/15/ mg/l 3/15/

93 APPENDIX B GENERAL CHARACTERISTICS OF DELINEATED SUB-BASIN AREAS IN THE SOLDIERS CREEK BASIN B.1 Land Use Characteristics B.2 Soil Types B.3 Hydrologic Information (Provided by Pegasus)

94 B.1 Land Use Characteristics

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98 B.2 Soil Types

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103 B.3 Hydrologic Information (Provided by Pegasus)

104 Soldiers Creek Nutrient Reduction Facility ~ Feasibility Study Continuous Simulation Modeling for the Cranes Roost and North Lake Watersheds Summary of Areas and Runoff Curve Numbers TABLE NO. 6 Basin Name Total Basin Area (acres) Directly Connected Impervious Area Non-Directly Connected Impervious and Pervious Areas % DCIA DCIA (acres) Runoff CN Pervious (acres) % N-DCIA N-DCIA (acres) Runoff CN BMR % % BMR % % BMR % % BMR % % BMR % % BMR % % Sub-totals CCR % % CCR % % CCR % % CCR % % CCR % % CCR % % CCR % % Sub-totals EL % % EL % % EL % % 8.4% EL % % EL % % EL % % EL % % EL % % EL % % EL % % EL % % EL % % EL % % Sub-totals GL % % GL % % GL % % GL % % GL % % GL % % GL % % GL % % GL % % GL % % GL % % Summary, Page 1 of 5 Printed On: 10/21/2010

105 Soldiers Creek Nutrient Reduction Facility ~ Feasibility Study Continuous Simulation Modeling for the Cranes Roost and North Lake Watersheds Summary of Areas and Runoff Curve Numbers TABLE NO. 6 Basin Name Total Basin Area (acres) Directly Connected Impervious Area Non-Directly Connected Impervious and Pervious Areas % DCIA DCIA (acres) Runoff CN Pervious (acres) % N-DCIA N-DCIA (acres) Runoff CN GL % % GL % % GL % % GL % % GL % % GL % % GL % % GL % % GL % % GL % % GL % % GL % % GL % % GL % % GL % % GL % % GL % % GL % % GL % % GL % % 7.9% GL % % GL % % GL % % GL % % GL % % GL % % GL % % GL % % GL % % GL % % GL % % GL % % GL % % GL % % GL % % GL % % GL % % GL % % Sub-totals 1, LLM % % LLM % % LLM % % Summary, Page 2 of 5 Printed On: 10/21/2010

106 Soldiers Creek Nutrient Reduction Facility ~ Feasibility Study Continuous Simulation Modeling for the Cranes Roost and North Lake Watersheds Summary of Areas and Runoff Curve Numbers TABLE NO. 6 Basin Name Total Basin Area (acres) Directly Connected Impervious Area Non-Directly Connected Impervious and Pervious Areas % DCIA DCIA (acres) Runoff CN Pervious (acres) % N-DCIA N-DCIA (acres) Runoff CN LLM % % LLM % % LLM % % LLM % % LLM % % LLM % % LLM % % LLM % % LLM % % LLM % % LLM % % LLM % % LLM % % LLM % % LLM % % LLM % % Sub-totals 1, LM % % LM % % 7.1% LM % % LM % % LM % % LM % % LM % % LM % % LM % % LM % % LM % % LM % % LM % % LM % % LM % % LM % % LM % % LM % % Sub-totals LMB % % LMB % % LMB % % LMB % % LMB % % Summary, Page 3 of 5 Printed On: 10/21/2010

107 Soldiers Creek Nutrient Reduction Facility ~ Feasibility Study Continuous Simulation Modeling for the Cranes Roost and North Lake Watersheds Summary of Areas and Runoff Curve Numbers TABLE NO. 6 Basin Name Total Basin Area (acres) Directly Connected Impervious Area Non-Directly Connected Impervious and Pervious Areas % DCIA DCIA (acres) Runoff CN Pervious (acres) % N-DCIA N-DCIA (acres) Runoff CN LMB % % LMB % % LMB % % LMB % % LMB % % Sub-totals LS % % LS % % LS % % LS % % LS % % LS % % LS % % LS % % LS % % Sub-totals LT % % Sub-totals ML % % Sub-totals NL % % Sub-totals NP % % Sub-totals RRB % % RRB % % RRB % % RRB % % RRB % % RRB % % RRB % % RRB % % RRB % % RRB % % RRB % % RRB % % RRB % % Summary, Page 4 of 5 Printed On: 10/21/2010

108 Soldiers Creek Nutrient Reduction Facility ~ Feasibility Study Continuous Simulation Modeling for the Cranes Roost and North Lake Watersheds Summary of Areas and Runoff Curve Numbers TABLE NO. 6 Basin Name Total Basin Area (acres) Directly Connected Impervious Area Non-Directly Connected Impervious and Pervious Areas % DCIA DCIA (acres) Runoff CN Pervious (acres) % N-DCIA N-DCIA (acres) Runoff CN Sub-totals WL % % WL % % WL % % WL % % WL % % WL % % WL % % WL % % WL % % Sub-totals Totals 5, , , Summary, Page 5 of 5 Printed On: 10/21/2010

109 APPENDIX C NPSLM MODEL SUMMARY SHEETS FOR THE SOLDIERS CREEK BASIN

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