!!! Performance!Evaluation!Report!of!the!StormTreat! Stormwater!Control!Measure!!! Submitted!to!! StormTreat!Systems!INC.!!!

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1 PerformanceEvaluationReportoftheStormTreat StormwaterControlMeasure Submittedto StormTreatSystemsINC. JamesJ.Houle,CPSWQ ProgramManager, Phone:603"767"7091 TimothyA.Puls,EIT SiteFacilityManager Phone:603"862"4024 March2013 Preparedby ThomasP.Ballestero,PE,PhD Director, PrincipalInvestigator Phone:603"862"1405 RobertM.Roseen,PE.,PhD. FormerDirector,UNHSC

2 Final Performance Evaluation Report on the StormTreat Stormwater Control Measure March 2013 The University of New Hampshire Stormwater Center TableofContents 1.0 EXECUTIVE SUMMARY INTRODUCTION TEST FACILITY DESCRIPTION STS Configuration and Sizing Reference TSS Information INSTRUMENTATION AND MEASURING TECHNIQUES Flow Other Measurements Water Quality Analysis TEST PROCEDURES Rainfall Collection and Measurement Field Sampling Procedures DATA EVALUATION RESULTS Event Mean Concentrations (EMC), Removal Efficiencies (RE) and Statistics Additional Performance Evaluation Enterococci Additional Real-Time Water Quality Monitoring SUMMARY AND CONCLUSIONS 22 2

3 LISTOFFIGURES Figure1:SiteplanviewoftheUniversityofNewHampshirefieldresearchfacilitypriortoSTSinstallation. 6 Figure2:PlanviewofStormTreatSystemstreatmentdeviceatUNHSC.Influentandeffluentmonitoring/sampling locationsidentifiedaswellasmajorsystemcomponents. 7 Figure3:Planviewofflowdiversionstructure. 8 Figure4:Planviewofdetentionchamber.Flowdiversionstructureistotheleft. 8 Figure5:PlanviewofvalvechamberandStormTreatunits.Detentionchamberistotheleft. 9 Figure6:TotalSuspendedSolids(TSS)forvariedlandusesandattheUNHStormwaterCenter(UNHSC);(Source: NationalStormwaterQualityDatabase,2005,UNHSC,2007) 10 Figure7:MonitoredStormSummary.Totalinfluentandeffluentvolumesareplottedingallonsontheleftvertical axis.rainfalldepthsareplottedininchesontherightverticalaxis.datesforeachofthe20monitoredeventsare aligned. 13 Figure8:TotalSuspendedSolidsEventMeanConcentrationsatinfluentandeffluentlocationsandRemoval Efficienciesfor19stormevents. 16 Figure9:SuspendedSedimentConcentrationEventMeanConcentrationsatinfluentandeffluentlocationsand RemovalEfficienciesfor19stormevents. 16 Figure10:TotalPetroleumHydrocarbons"DieselRangeEventMeanConcentrationsatinfluentandeffluent locationsandremovalefficienciesfor3stormevents. 17 Figure11:TotalZincEventMeanConcentrationsatinfluentandeffluentlocationsandRemovalEfficienciesfor16 stormevents. 17 Figure12:NitrateEventMeanConcentrationsatinfluentandeffluentlocationsandRemovalEfficienciesfor11 stormevents. 18 Figure13:TotalKjeldahlNitrogenEventMeanConcentrationsatinfluentandeffluentlocationsandRemoval Efficienciesfor17stormevents. 18 Figure14:TotalNitrogenEventMeanConcentrationsatinfluentandeffluentlocationsandRemovalEfficienciesfor 17stormevents. 19 Figure15:TotalPhosphorusEventMeanConcentrationsatinfluentandeffluentlocationsandRemovalEfficiencies for20stormevents. 19 Figure16:EnterococciconcentrationsfrominfluentandeffluentsamplelocationsandRemovalEfficienciesfor7 stormevents. 20 LISTOFTABLES Table1:Laboratoryanalyticalmethodsanddetectionlimitsforeachanalyte...11 Table2:Rainfall"Runoffeventcharacteristicsfor20stormevents...14 Table3:Simplestatisticssummarizingeachoftheparametersoverthemonitoringperiod...15 Table4:SimplestatisticssummaryofEnterococciresultsovermonitoringperiod...20 Table5:Averageeffluentreal"timewaterqualityparametersforeachsampledstormevent

4 Final Performance Evaluation Report on the StormTreat Stormwater Control Measure March 2013 The University of New Hampshire Stormwater Center 1.0 EXECUTIVE SUMMARY University of New Hampshire Stormwater Center (UNHSC) has completed a sixteen month field verification study of StormTreat Systems stormwater control measure. Monitoring took place from April 2011 through July 2012 at the University of New Hampshire Stormwater Center s (UNHSC) main field facility in Durham, NH. The evaluated StormTreat system was designed by StormTreat Systems Inc. and DeLuca-Hoffman Associates Inc., in association with UNHSC. The treatment area includes direct rainfall over one acre of impervious pavement drained by a conventional catch basin and piping network. The system is designed to treat the water quality volume (WQV), a one-inch rainfall event over a 24 hour period. Rainfall runoff is designed to flow into a subsurface reservoir consisting of large diameter HPDE pipes. Runoff filters through the StormTreat system at an average rate of 2.0 gallons per minute (gpm) regulated by an outlet orifice control. Non-design stormwater runoff is diverted through an upstream flow splitter bypass resulting in the StormTreat system being hydraulically configured in what is termed an offline manner. The overall project objective was to evaluate performance with respect to influent and effluent water quantity and water quality. Water quantity was monitored at the influent, effluent, and bypass locations as well as local rainfall at 5-minute intervals throughout each sampled event. A contract laboratory analyzed water quality samples for the following parameters: sediment (TSS and SSC), petroleum hydrocarbons in the diesel range (TPH-D), metals (total zinc TZn), and nutrients (TP, ortho-p, TN, TKN, DIN NO3, NO2, NH3). Monitored real-time water quality parameters included dissolved oxygen, conductivity, temperature, and ph recorded at 5-minute intervals. Prior to initiation of the performance evaluation study an additional project study was conducted to verify the design flow rate and, if necessary, optimize the effluent flow rate to achieve greater treatment performance. The two installed STS tanks were set at different flow rates of 2 and 0.5 gallons per minute and grab samples were taken across 6 storm events. The results of the flow study validated that no statistically significant difference in treatment performance was evident with respect to TSS and TP. Therefore STS decided to move forward with testing the system set at an average effluent flow rate of 2gpm. 2.0 INTRODUCTION Under an agreement from StormTreat Systems Inc., field verification testing of a StormTreat Systems stormwater control measure (hereafter referred to as STS ) was conducted at the University of New Hampshire Stormwater Center, Durham NH. Testing consisted of determining the water quality performance for the following parameters: Total Suspended Sediment (TSS) Suspended Sediment Concentration (SSC) 4

5 Total Petroleum Hydrocarbons-Diesel Range (TPH-D) Total Zinc (TZn) Nitrogen as Nitrate (DIN) Total Kjeldahl Nitrogen (TKN) Total Nitrogen (TN) Total Phosphorus (TP) Enterococci Efficiency tests were conducted under normalized conditions at various ambient rainfall intensities, flow rates, and pollutant concentrations; all important variables reflective of natural field performance conditions. This report reflects analyses performed from April 2011 through July During this time period there were 20 monitored rainfall runoff events. While 20 storms were monitored in total not all analytes have datasets totaling 20 storms; this is due in part to detectable limits of the analytical methods used and the quality assurance protocols that govern post processing of the data. The STS treatment unit is one of 10 devices that are currently configured and tested in parallel. Performance testing of the STS treatment unit included monitoring of the influent (upstream of the detention structure) and effluent locations (downstream of the system). Monitoring locations are identified in Figure 2. All treatment strategies were uniformly sized to target a water quality volume (WQV), or a water quality flow (WQF). A WQV is a rainfall-runoff depth equivalent to 90% of the annual rainfall events, where a WQF is a unit peak discharged from the regional WQV. Under the parallel and uniformly sized configuration, a normalized performance evaluation is possible because different treatment strategies of the same scale receive runoff from events of the same duration, intensity, peak flow, volume, antecedent dry period, and pollutant loading. Primary funding for the fundamental UNHSC program has been provided by the Cooperative Institute for Coastal and Estuarine Environmental Technology (CICEET) and the National Oceanic and Atmospheric Administration (NOAA). The UNHSC is housed within the Environmental Research Group (ERG) at the University of New Hampshire (UNH) in Durham, New Hampshire. 3.0 TEST FACILITY DESCRIPTION The UNHSC studies stormwater-related water quality and quantity issues. The Stormwater Center s field facility is designed to evaluate and verify the performance of stormwater management devices and technologies in a parallel, event normalized setting. Ten different management systems, including the STS device, are currently undergoing side-by-side comparison testing under strictly monitored natural conditions (Figure 1). 5

6 Figure 1: Site plan view of the University of New Hampshire field research facility prior to STS installation. The research facility was designed to function as a field testing site for numerous, uniformly sized, isolated, parallel treatment systems. Rainfall-runoff is evenly divided at the head of the facility in a distribution box, designed with the floor slightly higher than the outlet invert elevations to allow for particulate scour into the pipe network. Effluent from all systems is piped into a central sampling gallery, where system sampling and flow monitoring occurs. The parallel configuration normalizes the treatment processes for event and watershed-loading variations such that system performances may be directly compared to each other. The testing facility is located on the perimeter of a 9-acre commuter parking lot at the University of New Hampshire in Durham. The parking lot is standard dense mix asphalt that was installed in 1996, and is used to near capacity throughout the academic year. The sub-catchment area is large enough to generate substantial runoff, which is gravity fed to the parallel treatment processes. The parking lot is curbed and entirely impervious. Activity is a combination of passenger vehicles and routine bus traffic. The runoff time of concentration for the conventional parking lot is 22 minutes, with slopes ranging from %. The area is subject to frequent plowing, salting, and sanding during the winter months. Literature reviews indicate that total suspended sediment concentrations are above or equal to national norms for commercial parking lot runoff (refer to Section 3.2 and Figure 6 of this report). The climatology of the area is characterized as a coastal, cool temperate forest. Average annual precipitation is 44 inches that is nearly uniformly distributed throughout the year, with average monthly precipitation of 3.7 inches ±0.5. The mean annual temperature is 48 F, with the average low in January at 15.8 F, and the average high in July at 82 F. 3.1 STS Configuration and Sizing The StormTreat system at UNHSC was designed to meet research objectives as well as space requirements at the Stormwater Center Field Facility. See Figure 2 for a plan view of the system design. The evaluated STS control measure was tested in an offline configuration allowing for flows up to the design flow to be routed through the treatment device. Flow that exceeds the 6

7 WQF and/or WQV is diverted around the device at the flow diversion structure. Untreated runoff first enters the flow diversion structure, which consists of a 4 foot diameter manhole with a 2 foot deep sump and an overflow weir, Figure 3. The crest of the overflow weir was set 0.5 feet below the top of the detention chamber to allow for freeboard within the system. Flows exit the diversion structure through a 12 inch diameter manifold that splits flow evenly into underground storage pipes. These pipes comprise the detention chamber consisting of four, 4 foot diameter HDPE pipes that are each 25 feet long, Figure 4. The total storage capacity in these pipes is 1,257 cubic feet (9,400 gallons) equal to one third of the WQV (3, 630 cubic feet or 27,152 gallons). Flow exits the detention chamber through another 12 inch diameter manifold bringing flow back into a single pipe and into the valve chamber, Figure 5. Heree pipe size is reduced from a 12 inch to a 4 inch pipe that leads to the STS unit. In Figure 5 there are two STS units of which only Unit #2 was evaluated during this study. The valve chamber has ball valves on each influent and effluent pipe for each STS unit giving the ability to direct flows as needed. Throughout the monitoring period flow was directed through Unit #2 and then back to the valve chamber at a rate regulated by an orifice control structure. Orifice sizing was designed to discharge at a rate of 2 gallons per minute when the STSS unit was half full. The effluent sampling location is also housed in the valve chamber. Monitoring locations for influent and effluent points are identified on Figure 2. Figure 2: Plan view of StormTreat Systems treatment device at UNHSC. Influent and effluent monitoring / sampling locations identifiedd as well as major system components. By the UNH Stormwater Center-March

8 Figure 3: Plan view of flow diversion structure. Figure 4: Plan view of detention chamber. Flow diversion structure is to the left. By the UNH Stormwater Center-March

9 Figure 5: Plan view of valve chamber and StormTreat units. Detention chamber is to the left. The STS was installed in September 2010 and allowed a two month startup period to flush out media and construction related influences. After the startup period, a four month preliminary flow study was conducted to evaluate system performance based on effluent flow rate. Performance evaluation of one STS tank set at a design flow rate of 2gpm commenced in April Reference TSS Information n Comparisons of TSS concentrations for varied land uses are presented in Figure 6. Urban highway pollutant concentrations tend to be twice the mean concentration measured for parking lots and residential uses. The data collected from the UNH facility iss within the national norm for commercial parking lots and is within the range of typical concentrations observed for a range of land usess (National Stormwater Quality Database, 2005; UNHSC 2007). By the UNH Stormwater Center-March

10 Figure 6: Total Suspended Solids (TSS) for varied land uses andd at the UNH Stormwater Center (UNHSC); (Source: National Stormwater Quality Database, , UNHSC, ) 4.0 INSTRUMENTATION AND MEASURING TECHNIQUES 4.1 Flow Influent flows were monitored using Teledyne ISCO 6712 Automated Samplers accompanied by Teledynee ISCO 750 Area Velocity probes. Effluent flow depths were measured using Teledyne ISCO 6712 Automated Samplers accompanied by Teledyne ISCO 730 Bubbler Flow Modules in combination with a 6 inch Thelmar compound weir with h laboratory developed rating curves to yield flows. 4.2 Other Measurements Temperature, ph, Specific Conductivity, and Dissolved Oxygen were collected by YSI 600XL multi-parameter sondes. These parameters are monitoredd real-time for the influent and effluent flows but are not included under this contract. Calibrations for all instrumentation are calibrated throughout the project period according to a quality assurance project plan maintained and operated by UNHSC. 1 Pitt, R. E., Maestre, A., and Center for Watershed Protection. (2005) "Thee National Stormwater Quality Database (NSQD, version 1.1) )." USEPA Office of Water, Washington, D.C. 2 UNHSC, Roseen, R., T. Ballestero, and Houle, J. (2007). "UNH Stormwater Center Annual Report.." University of New Hampshire, Cooperative Institute for Coastal and Estuarine Environmental Technology, Durham, NH. By the UNH Stormwater Center-March

11 4.3 Water Quality Analysis Samples were processed and analyzed by an EPA and National Environmental Laboratory Accreditation Conference (NELAC) certified laboratory using the standard methodologies outlined in Table 1. Table 1: Laboratory analytical methods and detection limits for each analyte. Analyte Analytical Method Sample Detection Limit (mg/l) Method Detection Limit (mg/l) a Total Suspended Solids SM 2540 D Variable, Suspended Sediment Concentration ASTM D-3977 Variable, Total Petroleum Hydrocarbons Diesel Range EPA 8015B Variable Zinc in water EPA Nitrate/Nitrite in water EPA 300.0A Total Kjeldahl Nitrogen ASTM A Total Nitrogen SM 4500NH Total Phosphorus EPA Enterococci EPA Variable 10 cfu a Method detection limit is different than sample detection limit which will often be higher as they are based on sample volume available for analyses. 5.0 TEST PROCEDURES 5.1 Rainfall Collection and Measurement Rainfall depth is monitored with an ISCO 674 Rain Gauge installed within 100 feet of the STS and connected to an ISCO 6712 Automated Sampler. The rain gauge is mounted inside a steel cylinder with an 8 inch diameter screened opening on top to collect rain yet keep out debris. Collected rain is funneled to a tipping bucket mechanism that is mounted on a center pivot. The tipping bucket has two identical chambers on each side of the center pivot. When 0.01 inch of rain is collected in one chamber the bucket tips, dumps out the water, and the other chamber begins to fill. Each time the bucket tips a magnet passes over an electrical switch sending a pulse to the ISCO 6712 which in turn records a rainfall depth of 0.01 inch. This process continues throughout the duration of the rainfall event. 5.2 Field Sampling Procedures Composite samples were taken from influent and effluent waters by automated samplers. Automatic samplers are programmed to sample 100 milliliter aliquots at flow weighted intervals into twenty-four 1 liter containers allowing for a maximum of 240 samplers per event. The sampling program is designed to ensure adequate coverage of the storm event and adjusted to accommodate seasonal fluctuations in rainfall patterns. Rejection criteria included minimum rainfall depth of 0.1 inches and 10 aliquots per sampling event. Influent time of concentration is approximately 22 minutes. Effluent time of concentrations vary for each storm and are 11

12 dependent on rainfall intensity, a higher initial intensity equates to a shorter time of concentration. All samples are stored in thermostatically controlled conditions at 39 F until processed. One Liter disposable LDPE sample bags are used to assure clean, non-contaminated sample containers. Full storm composites are generated using a United States Geological Survey (USGS) Dekaport Cone Sample Splitter. Composite samples are sealed and labeled with a unique, water proof, adhesive bar code that corresponds with a field identification code containing information relating to the stormwater treatment unit and date of sampling. Records are kept that correlate sample bar code with sample time, date, flow, and other real time water quality parameters. Detailed written and electronic records are kept identifying the date, time, and unique bar code and field identification numbers. This begins the chain-of-custody record that accompanies each sample to track handling and transportation throughout the sampling process. All analyses and procedures comply with the Technology Acceptance and Reciprocity Partnership (TARP), and the Technology Acceptance Protocol Ecology (TAPE) guidelines to the maximum extent possible. We operate under a detailed Quality Assurance Project Plan (QAPP) which is available on request. 6.0 DATA EVALUATION Data analyses cover a range of approaches including: evaluation of storm characteristics evaluation of event mean concentrations normalized performance efficiencies Storm characteristics such as total depth of rainfall, peak intensity, total storm volume, antecedent dry period, among others are collected for each storm event. Results for all storms sampled are presented in Table 2. Event mean concentrations (EMC s) are a parameter used to represent the flow-proportional average concentration of a given water quality parameter for a storm event. It is defined as the total constituent mass divided by the total runoff volume. When combined with flow measurement data, the EMC can be used to estimate the pollutant loading from a given storm. Most of the EMC data collected during this study were based upon direct measurement from flow-weighted composite samples. Due to the variability of precipitation events and resultant runoff conditions, the sample trigger conditions and flow-weighted sample pacing were variable and adjusted on a storm by storm basis according to the most up-to-date precipitation forecasts. EMCs are compared for each pollutant parameter using simple statistics. The data provides a basis to evaluate the primary study question; i.e., to discern whether the STS unit has served to produce observable (and perhaps statistically significant) improvement in water quality and reduction in peak flow. 12

13 The range of statistical analyses presented reveals a range of performance trends. Efficiency Ratio (ER) analysis was performed on the final dataset. For many performance datasets for stormwater treatment systems, the ER is a stable estimation of overall treatment performance as it minimizes the impact of low concentration values, or relatively clean storms with low influent EMCs. Whereas Removal Efficiencies (RE) reflect treatment unit performance on a storm by storm basis, ERs weight all storms equally and reflect overall influent and effluent averages across the entire data set. REs are presented as both an average and median of aggregate storm values. In general aggregate median RE values are more reliable in highly variable, nonnormally distributed datasets such as those experienced in stormwater treatment unit performance studies. A review of REs on a per event basis, ERs for the entire period of monitoring, and EMCs per event will reveal the measured performance variations attributable to season, flow, concentration, and other factors. 7.0 RESULTS Results presented below for the STS represent data collected over 15 months of monitoring conducted at the UNHSC field facility. The total influent and effluent storm volumes in gallons are plotted along with total rainfall depths in Figure 7. Table 2 displays rainfall event characteristics for the 20 monitored storm events including influent and effluent peak flow, antecedent dry period, and season. The data set reflects rainfall across all seasons and covers a wide range of rainfall characteristics. Storms ranged in size from low intensity to high intensity, small volume to large volume. Total Storm Volume and Rainfall Depth May-11 Aug-11 Nov-11 Feb-12 Jun , Total Volume (gal) 100,000 80,000 60,000 40,000 20, Precipitation (in) 0 May-11 Jun-11 Aug-11 Sep-11 Nov-11 Jan-12 Feb-12 Apr-12 Jun-12 Jul Rainfall Influent Effluent Figure 7: Monitored Storm Summary. Total influent and effluent volumes are plotted in gallons on the left vertical axis. Rainfall depths are plotted in inches on the right vertical axis. Dates for each of the 20 monitored events are aligned. 13

14 Table 2: Rainfall-Runoff event characteristics for 20 storm events. Date Rainfall Influent Effluent Bypass Storm Antecedent Peak Peak Total Total Total Duration Depth Peak Flow Dry Period Intensity Flow Volume Volume Volume (min) (in) (gpm) (days) (in/hr) (gpm) (gal) (gal) (gal) Season 5/18/ , ,257 8, Spring 6/11/2011 1, , ,316 7,729 1 Spring 6/18/ , , Spring 6/22/ , , Summer 7/13/ , , Summer 8/6/ , , Summer 8/15/2011 1, , ,114 12,831 5 Summer 8/21/ , , Summer 9/6/2011 1, , ,996 3,644 8 Summer 9/22/2011 1, , , Summer 9/29/2011 1, , ,453 4,286 4 Fall 11/10/ , ,876 7, Fall 11/30/ , , Fall 1/23/ , , Winter 1/26/2012 1, , ,235 4,895 3 Winter 4/22/2012 2, , ,628 28, Spring 5/15/ , , Spring 6/2/2012 1, , ,899 10, Spring 6/22/2012 1, , ,914 3,104 8 Summer 7/26/ , , Summer 7.1 Event Mean Concentrations (EMC), Removal Efficiencies (RE) and Statistics Influent and effluent EMC and RE values are presented in Figure 8 through Figure 15 for each storm for the eight pollutants across all monitored storm events. These time series plots show performance for individual storm events as well as seasonal and annual trends. When EMC results are below detection limit (BDL) a value of half the detection limit (DL) is used for statistical purposes. No consistently accepted methodology for representing BDL values in stormwater treatment system effluent currently exists especially with respect to systems that detain a large volume of runoff and exhibit a longer effluent hydrograph than influent waters. Where detection limits are low enough (< 1 mg/l for TSS) the conventional statistical approach of using 0.5 x DL (D.R. Helsel, and R.M. Hirsch, 2002) is adequate. This method provides a more conservative measure than simply inserting a value of zero for BDL results. Table 3 summarizes each parameter over the monitoring period using simple statistics to present performance outcomes. Statistics include: n = number of storms evaluated for each parameter mean = average EMC of all monitored events DL = detection limit ER = efficiency ratio which is the percent difference between the influent and effluent mean EMC values AVG RE = average removal efficiency of all monitored events Median RE = median removal efficiency of all monitored events SD = standard deviation of EMC values Cv = coefficient of variation which is the ratio of EMC SD to mean EMC. This gives the level of variability in the data set. The lower the Cv the more consistent the values in the data set. 14

15 Table 3: Simple statistics summarizing each of the parameters over the monitoring period. Pollutant Statistic Influent Effluent Pollutant Statistic Influent Effluent n n mean 79 4 mean DL DL TSS(mg/l) ER 95% ER "78% DIN(mg/l) AVGRE 89% AVGRE "132% MedianRE 93% MedianRE "80% SD SD Cv Cv n n mean 63 2 mean DL DL SSC(mg/l) ER 96% ER 24% TKN(mg/l) AVGRE 91% AVGRE 21% MedianRE 96% MedianRE 23% SD 83 2 SD Cv Cv n 4 4 n mean mean DL DL TPH"D(ug/l) ER 73% ER 5% TN(mg/l) AVGRE 68% AVGRE 1% MedianRE 70% MedianRE 4% SD SD Cv Cv n n mean mean DL DL TZn(mg/l) ER 52% ER 53% TP(mg/l) AVGRE 62% AVGRE 44% MedianRE 67% MedianRE 50% SD SD Cv Cv Note: n = number of storms; DL = detection limit; ER = efficiency ratio; AVG RE = average removal efficiency; SD = standard deviation; Cv = coefficient of variation 15

16 StormTreat Performance Monitoring--TSS Total Suspended Solids (mg/l) % % % 70% % % % % 20% % 0 0% Feb-11 Jun-11 Sep-11 Dec-11 Apr-12 Jul-12 Oct-12 Influent Effluent RE Removal Efficiency Figure 8: TotalSuspendedSolidsEventMeanConcentrationsatinfluentandeffluentlocationsandRemoval Efficienciesfor19stormevents. StormTreat Performance Monitoring--SSC Suspended Sediment Concentration (mg/l) % Feb-11 Jun-11 Sep-11 Dec-11 Apr-12 Jul-12 Oct-12 Influent Effluent RE 100% Figure 9: SuspendedSedimentConcentrationEventMeanConcentrationsatinfluentandeffluentlocationsand RemovalEfficienciesfor19stormevents. 90% 80% 70% 60% 50% 40% 30% 20% 10% Removal Efficiency 16

17 StormTreat Performance Monitoring--TPH-D Total Petroleum Hydrocarbons - Diesel Range (ug/l) % Feb-11 Jun-11 Sep-11 Dec-11 Apr-12 Jul-12 Oct-12 Influent Effluent RE 100% Figure 10:TotalPetroleumHydrocarbons"DieselRangeEventMeanConcentrationsatinfluentandeffluent locationsandremovalefficienciesfor3stormevents. 90% 80% 70% 60% 50% 40% 30% 20% 10% Removal Efficiency StormTreat Performance Monitoring--TZn Total Zinc (mg/l) % 90% % % 60% % 40% % % 10% % Feb-11 Jun-11 Sep-11 Dec-11 Apr-12 Jul-12 Oct-12 Influent Effluent RE Removal Efficiency Figure 11: TotalZincEventMeanConcentrationsatinfluentandeffluentlocationsandRemovalEfficienciesfor 16stormevents. 17

18 StormTreat Performance Monitoring--NO3 Nitrate (mg/l) % -50% -100% -150% -200% -250% -300% -350% -400% Removal Efficiency Figure 12: NitrateEventMeanConcentrationsatinfluentandeffluentlocationsandRemovalEfficienciesfor11 stormevents % Feb-11 Jun-11 Sep-11 Dec-11 Apr-12 Jul-12 Oct-12 Influent Effluent RE StormTreat Performance Monitoring--TKN % Total Kjeldahl Nitrogen (mg/l) % 60% 40% 20% 0% -20% -40% % Feb-11 Jun-11 Sep-11 Dec-11 Apr-12 Jul-12 Oct-12 Influent Effluent RE Removal Efficiency Figure 13:TotalKjeldahlNitrogenEventMeanConcentrationsatinfluentandeffluentlocationsandRemoval Efficienciesfor17stormevents. 18

19 StormTreat Performance Monitoring--TN Total Nitrogen (mg/l) % % 60% 40% 20% 0% -20% -40% -60% -80% % Feb-11 Jun-11 Sep-11 Dec-11 Apr-12 Jul-12 Oct-12 Influent Effluent RE Removal Efficiency Figure 14: TotalNitrogenEventMeanConcentrationsatinfluentandeffluentlocationsandRemoval Efficienciesfor17stormevents. StormTreat Performance Monitoring--TP Total Phosphorus (mg/l) % 80% 60% 40% 20% 0% -20% -40% Removal Efficiency Figure 15: TotalPhosphorusEventMeanConcentrationsatinfluentandeffluentlocationsandRemoval Efficienciesfor20stormevents % Feb-11 Jun-11 Sep-11 Dec-11 Apr-12 Jul-12 Oct-12 Influent Effluent RE 19

20 7.2 Additional Performance Evaluation Enterococci UNHSC conducted performance evaluation of the STS with respect to bacteria removals. This testing was in conjunction with a separately funded project and is additional to the contracted scope of work for this performance evaluation. Results are presented here purely in an informational context. Influent and effluent samples were sent to an outside lab and analyzed for E. coli, Fecal Coliform (FC), and Enterococci. Only Enterococci data is presented here as the E. coli and FC data was too inconsistent to draw any meaningful conclusions from. A times series plot with removal efficiencies for each event is presented in Figure 16 and statistics are presented in Table 4. Concentration(cfu/100ml) StormTreatPerformanceMonitoring"" Enterococci % 90% 80% % 60% 50% 10 40% 30% 20% 10% 1 0% Apr"11 Jun"11 Jul"11 Sep"11 Nov"11 Dec"11 Influent Effluent %RE RemovalEfficiency Figure 16: Enterococci concentrations from influent and effluent sample locations and Removal Efficiencies for 7 storm events. Table 4: Simple statistics summary of Enterococci results over monitoring period. Pollutant Statistic Influent Effluent n 7 7 mean Enterococci (cfu/100ml) DL ER 83% AVGRE 81% MedianRE 88% SD Cv

21 7.3 Additional Real-Time Water Quality Monitoring Water quality parameters were recorded throughout the monitoring period using an YSI 600XL multi-parameter probe. Parameters include specific conductivity, dissolved oxygen, ph, and temperature. Table 5 lists the average effluent values over the duration of each sampled storm event with summary statistics for all monitored events. Table 5: Average effluent real-time water quality parameters for each sampled storm event. AverageReal"TimeWaterQualityParameters Date Specific Dissolved Temperature Conductivity Oxygen ph ( F) (µs/cm) (mg/l) 5/18/ /11/ /18/2011 1, /22/ /13/2011 1, /6/ /15/ /21/ /6/ /22/ /29/ /10/2011 1, /30/2011 1, /23/2012 3, /26/2012 2, /22/ /15/2012 1, /2/ /22/2012 1, /26/ n Average 1, Median StDev Coefficient ofvariation

22 8.0 SUMMARY AND CONCLUSIONS The STS performed well for total suspended solids (TSS) and suspended sediment concentration (SSC) removal. In all cases, TSS and SSC effluent concentrations border the sample detection limit throughout the 15 month monitoring period. As with other studied systems total petroleum hydrocarbons diesel range (TPH-D) and total zinc (TZn) removals tend to be equitable with sediment removals. Influent loading for TPH-D in this study was very inconsistent with levels commonly below detectable limits making conclusions difficult. TZn removals were high with effluent values consistently bordering the detection limit with little fluctuation evidenced by a low standard deviation of Dissolved inorganic nitrogen levels (NO2, NO3, NH3) show a pattern of export which may be associated with a lack of unit processes effectively targeting dissolved nitrogen species. Total Kjeldahl Nitrogen (TKN) shows modest removals. As there is seldom measurable levels of ammonia in stormwater runoff, TKN represents the organic fraction of nitrogen species. Total nitrogen removal efficiencies (TN = DIN + TKN) are flat with influent and effluent means equal: meaning that while nitrogen may be changing oxidative states in-situ, there is little to no mass reduction over the monitoring period. Total phosphorus (TP) reductions in the STS system demonstrate a high capacity to sorb phosphorus. The relatively low influent concentrations, mean of 0.07mg/l, coupled with an efficiency ratio 53% is indicative of strong treatment performance. Phosphorus sorptive capacity in stormwater management systems is typically not unlimited. Once sorptive capacity is reached, breakthrough occurs and systems can begin to leach, or pass through phosphorus. Biological unit processes can regenerate sorptive capacity in filter media. Additional analyses may reveal the time to phosphorus breakthrough for the STS treatment practice. Finally, while the number of sampled events for enterococci is small (n=7) the STS shows great promise for bacterial removals RE median of 88%. Bacteria removals are often of great concern for coastal watershed and the ability to reduce indicator colonies is a positive result. 22