Wells Fargo Parking Lot Improvements

Transcription

1 DRAINAGE REPORT FOR Wells Fargo Parking Lot Improvements 112 West Magnolia Street Fort Collins, CO Prepared for: Cox Pavement Consulting, LLC 228 Stratton Park Road Bellvue, CO, Prepared by: St. Cloud Drive, Suite 180 Loveland, CO (970) Project No: Date: June 28, 2017

2 Parking at 112 West Magnolia Street FINAL DRAINAGE REPORT ENGINEER S CERTIFICATION I hereby certify that this Final Drainage Report for the design of stormwater management facilities for the Parking at 112 West Magnolia Street Project was prepared by me, or under my direct supervision, in accordance with the provisions of the City of Fort Collins Storm Drainage Design Criteria and Construction Standards for the owners thereof. Cody Geisendorfer, P.E. Registered Professional Engineer State of Colorado No

3 I. Table of Contents I. GENERAL LOCATION AND DESCRIPTION... 1 A. Location...1 B. Description of Property...1 II. DRAINAGE BASINS AND SUB-BASINS... 2 A. Major Basin Description...2 B. Sub-Basin Description...2 III. DRAINAGE CRITERIA... 2 A. Regulations...2 B. Implementation of the Four Step Process...3 C. Development Criteria Reference and Constraints...4 D. Hydrological Criteria...4 E. Hydraulic Criteria...5 F. Modifications of Criteria...5 IV. DRAINAGE FACILITY DESIGN... 5 A. General Concept...5 B. Specific Details...5 V. CONCLUSIONS... 6 A. Compliance with Standards...6 B. Drainage Concept...7 VI. REFERENCES... 7

4 VII. APPENDICES A. Hydrologic Computations Vicinity Map Fort Collins Flood Map FEMA FIRM Map Panel 08069C0979H USGS Soil Map Fort Collins Rainfall Intensity Curve Fort Collins Rainfall Intensity Table Table RO-11 Rational Method Runoff Coefficients for Composite Analysis Rational Method Calculated Composite C Tables Rational Method Calculated Imperviousness Rational Method Calculated Flows B. Hydraulic Computations Modified FAA Method Orifice Sizing Calculation C. Map Pocket Drainage Plan

5 I. GENERAL LOCATION AND DESCRIPTION A. Location The proposed site is located in the northeast quarter (NE ¼) of Section 11, Township 7 North, Range 69 West of the 6th P.M. in Larimer County, Colorado. Specifically, the property is located at the southeast corner of West Magnolia Street and College Avenue. The property address is 112 West Magnolia Street, Fort Collins, Colorado, (Please see the vicinity map located in the Appendix A). B. Description of Property The property s parcel number is The site is located on Lots 1 and 2, Block 113 Fort Collins Subdivision and is currently acres of gravel parking lot surrounded by the clock tower building to the north, Wells Fargo to the south, and office buildings to the east and west. West Magnolia is located directly south, College Avenue is located directly east, and an alley is located west of the property. There is an existing access to the site on all three roadways. The existing accesses on College Avenue and Magnolia Street are to be abandoned. The access on Magnolia Street will be replaced with a new access. Both existing West Magnolia Street and College Avenue are paved with curb, gutter, sidewalk, and utilities installed. The existing property is a gravel parking lot that drains south to West Magnolia Street and College Avenue. Existing West Magnolia Street drains west to the existing inlet, where it is conveyed to the Poudre River. Existing College Avenue drains north towards the existing storm inlet, where it is conveyed to the Poudre River. There are generally no offsite flows that drain toward the property. The entire site is located within the Cityregulatorty 100-year Old Town Basin Floodplain, prepared by Anderson Consulting Engineers, July 15, The northern half of the site is located in a moderate risk area, and the southern half of the site is located within the city flood fringe (see City Flood Risk Map in Appendix A). According to the NRCS soils map survey, the native soils consist of the Type C soils. These soils consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. There are no irrigation facilities located within the proposed site area. Irrigation for landscaping is proposed for the new development. The proposed development will consist of the construction of a 35-space off-street parking lot that will act as employee parking for the Wells Fargo directly across West Magnolia PG. 1

6 Street. The parking lot will be paved concrete and pervious paver in parking stalls with curb and gutter. The existing alley will be repaved with concrete. Seven on-street parking stalls will be added to West Magnolia Street. II. DRAINAGE BASINS AND SUB-BASINS A. Major Basin Description The proposed site is located within the Old Town Drainage Basin, located in north-central Fort Collins. The basin has a drainage area of approximately 2,120 acres, including approximately 400 acres of the Colorado State University campus. The entire basin is urbanized, with some development dating back to the late 1800s. Generally, the basin drains from west to east. The Old Town Basin receives some runoff water from the Canal Importation Basin directly west of Old Town. Most of the water from Old Town drains to the Poudre River, just to the east. B. Sub-Basin Description Historically, most of the site drains south to West Magnolia Street. The developed site is delineated into one sub-basin, with underground detention designed to provide the required detention for the site. Sub-basin B1, (0.436 acres), consists of a concrete parking lot, landscaped area, and permeable pavers. Rainfall travels via overland flow for short distances to gutters and to permeable pavers in the parking stalls. The parking stalls incorporate the City of Fort Collins LID water quality feature, which treats the water by filtering it through a layer of #57 Base, followed by a layer of #2 Rock Sub-Base. The water is then collected in perforated PVC subdrains, and routed to the existing City stormwater collection system. Currently, offsite flows do not enter the site property. This will not change after the site has been developed. III. DRAINAGE CRITERIA A. Regulations Drainage design criteria specified in the City of Fort Collins Storm Drainage Design Criteria and Construction Standards Manual (FCSDCM) and the Urban Storm Drainage Criteria Manual, Volume 3 by the Urban Drainage and Flood Control District (UDFCD) have been referenced in the preparation of this study. PG. 2

7 B. Implementation of the Four Step Process Our stormwater management strategy utilizes the Four Step Process to minimize adverse impacts of urbanization on receiving waters, as follows: Step 1 Employ Runoff Reduction Practices. The first consideration taken in trying to reduce the stormwater impacts of this development is the site selection itself. The land use for the site remains unchanged: it has been a gravel parking lot, but to provide a higher level of service to their employees, Wells Fargo is paving the parking lot. This will reduce the amount of dirt that is tracked on to the paved streets in the area by vehicles during precipitation events. By selecting a site with historically undetained runoff, the burden of development will be reduced, because underground detention is being provided. Underground detention allows this high value downtown site to be fully utilized, whereas a pond would consume space in this busy area. Permeable pavers are used to reduce the area of impervious surfaces. Step 2 Implement BMPs That Provide a Water Quality Capture Volume (WQCV) with Slow Release. Urban development will cause stormwater runoff to increase from the site. The primary water quality control will occur in the permeable paver detention, located under the parking spaces of the lot. Refer to the map pocket for permeable paver details and crosssections. The detention will increase water quality and promote infiltration. Water quality treatment for 50% of the site is provided for in the Udall Natural Area water treatment facility. Step 3 Stabilize Drainageways. The Poudre River is the governing drainageway for the proposed site. By improving the water quality and increasing infiltration, the likelihood of bed and bank erosion from this site is reduced. Step 4 Implement Site Specific and Other Source Control BMPs. Permeable Pavement Systems: Flow from the parking lot will directly flow into the void area of the pavers, avoiding any extra pollutant-flow contact time. Landscaping: Personnel from Coffey Engineering and CS Design worked with the City of Fort Collins Forestry Department to preserve a large tree on the west side of the parking lot. Interception storage, the water caught by plants at the onset of a rainstorm, is significant when PG. 3

8 a large tree shades a small lot. Some amount of the intercepted water evaporates, never reaching the ground. Additionally, water retained by the leaves and branches moves more slowly through the hydrograph. In the case of this tree, the canopy hangs directly over existing impervious asphalt area. With infill development, we need to work around numerous existing infrastructure items, in three dimensions. The stormwater piping had to be routed around the tree in both the lateral and vertical directions, and the pavement design slightly altered in the alley in order to retain the tree. C. Development Criteria Reference and Constraints The criteria used as the basis for analysis and design of stormwater management improvements for this site are found in the references cited. To the knowledge of the author, there are no other capital drainage improvements planned for the site that would constrain or otherwise influence the design of the stormwater improvements for this site. D. Hydrological Criteria Stormwater runoff is analyzed for storms with 2-year and 100-year return frequencies. The Rational Method was chosen for this small site. The Rational Method provides that: Q = CIA, where: Q = Design flow in cubic feet per second (cfs) C = Coefficient of runoff for the area under consideration I = Rainfall intensity for the design storm duration (in/hr) A = Area of the drainage sub-basin under consideration (ac) Peak flows were calculated using the Rational Method for the 2-year and 100-year storm events. We used the local 1-hour rainfall depth and Fort Collins rainfall intensities, calculated as a function of the time of concentration. These values were obtained by the City of Fort Collins Rainfall Intensity-Duration-Frequency (IDF) curve/table; Figure 3-1 and Table 3-1a, and can be found in Appendix A. Additionally, per the City of Fort Collins, the coefficients have been multiplied by the appropriate storm factors. Percent imperviousness values were taken from Table RO-11, Rational Method Runoff Coefficients for Composite Analysis, FCSCM (See Appendix A). Soils of hydrologic soil type C dominate the site. Onsite runoff was calculated to determine the runoff differential between existing and developed conditions for use in sizing the WQCV as required by the FCSDM. The hydrologic basin parameters and runoff rates are included in the Appendices and include quantification of the allowable volume reduction. PG. 4

9 The design worksheets included in the Appendices to this Final Drainage Report present documentation of the hydrologic calculations for the on-site storm drainage systems. We modified Urban Drainage spreadsheets to incorporate Fort Collins criteria as follows: The Modified FAA spreadsheet incorporates the rainfall data from the Fort Collins Criteria Manual, Volume 1, Table RA-7 and RA-8. The numbers from RA-7 and RA- 8 were manually entered in the first two columns of the UDFCD spreadsheet, which overrides the automatic table normally provided in the spreadsheet. A modified UDFCD Stage Storage Sizing for Detention Basins sheet was used to calculate the volumes for the underground detention. The volumes corresponding to drawing C5.0, Drainage Plan are referenced as P1 through P4. The media under the pavers conforms to Fort Collins Detail D-54, Interlocking Pavers Cross Section, with the #57 Base thickness 4 and the #2 Rock thickness 16. The #2 Rock provides the detention volume. The void space of the #2 Rock is set to 30% in the calculations. E. Hydraulic Criteria Within this development, all runoff will be conveyed on the surface, initially as sheet flow and subsequently as concentrated flow in shallow pans and gutters. The assessment of required capacity and the sizing of the respective components of the drainage system are based on the anticipated runoff from the 100-year storm event. The surface runoff will culminate into the permeable pavers. F. Modifications of Criteria There are no modifications or variances requested in connection with the design of the stormwater management for the parking at 112 West Magnolia site development. IV. DRAINAGE FACILITY DESIGN A. General Concept The storm drainage system is designed to safely convey developed storm flows by sheet flow, concentrated pan, underdrain, and gutter flow to the permeable pavers and street flowlines. The design worksheets included in the Appendices to this Final Drainage Report present details of the hydrologic and hydraulic calculations pertinent to the design of the on-site storm drainage system. A drainage plan, showing the proposed development of the site and developed drainage patterns is included in the map pocket following the Appendices. B. Specific Details Sub-basin B1, (0.436 acres), consists of a concrete parking lot, landscaped area, and permeable pavers. Rainfall travels via overland flow to the gutter flowline of the parking area PG. 5

10 into the permeable pavers. Overland flow will also infiltrate the permeable pavers in the parking stalls, where it will be treated. The 100-year flow is released at the 2-year historic rate, via an 8 pipe with an orifice plate with a 3.2 opening into the storm drain system. After treatment within the permeable pavers, the WQCV will also be released into storm drain system, where it will be eventually conveyed to the Poudre River. If the paver system overflows due to clogging, catch basins at the low point of the pavers will direct runoff into the underdrain system. Sub-basin B1 produces a 100-year flow of 3.53 cfs. The UDFCD FAA spreadsheet was modified to incorporate rainfall data from the Fort Collins Criteria Manual, Volume 1, Table RA-7 and RA-8. This spreadsheet was used to calculate the outflows and inflows from the basin, and to generate a Stage Storage Table. A key parameter is the Major Stage Storage Volume, 2,250 ft 3. The underground detention under the pavers is designed per Fort Collins Detail D-54, Interlocking Pavers Cross Section. The detention volume is the #2 rock, with a height of 16 inches, and a surface area of 5658 ft 2 (see sheet C5.0 for a tabulation of areas). 30% of the volume of the rock is void space. The detention volume for each paver section is: PAVER SECTION PAVER AREA #2 SUB-BASE DEPTH DETENTION VOLUME SQ FT 16" 276 CU FT SQ FT 16" 720 CU FT SQ FT 16" 720 CU FT SQ FT 16" 548 CU FT DETENTION VOLUME FOUND USING AREA X DEPTH X 30% TOTAL: 2264 CU FT This compares favorably with our Major Stage Storage Volume of 2,250 ft 3. Water quality parameters were also checked in the calculations. V. CONCLUSIONS A. Compliance with Standards The drainage design for the Parking at 112 West Magnolia Street follows the requirements of the City of Fort Collins Storm Drainage Design Criteria and Construction Standards Manual as well as the City s floodplain regulations. The criteria and recommendations of the Urban Storm Drainage Criteria Manual are also reflected in the design of the drainage systems. PG. 6

11 B. Drainage Concept The drainage design for the Parking at 112 West Magnolia Street will safely convey onsite flows from the parking lot into the storm drains, by way of the permeable paver detention system. Underground detention and the preservation of an existing large tree help to minimize the impact of the development. Excellent water quality treatment will be achieved by the underground detention system. VI. REFERENCES City of Fort Collins Stormwater Criteria Manual, City of Fort Collins, Adopted December City of Fort Collins Municipal Code, Chapter 10 Flood Protection and Prevention City of Fort Collins, Urban Storm Drainage Criteria Manual, Volumes 1, 2, and 3, Urban Drainage and Flood Control District, April PG. 7

12 VII. APPENDICES APPENDIX A: Hydrologic Computations Vicinity Map Fort Collins Flood Map USGS Soil Map FEMA FIRM Map Panel 08069C0979H Fort Collins Rainfall Intensity Curve Fort Collins Rainfall Intensity Table Table RO-11 Rational Method Runoff Coefficients for Composite Analysis Rational Method Calculated Runoff Coefficients Rational Method Calculated Imperviousness Rational Method Calculated Flows

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14 S COLLEGE AVE W MAGNOLIA ST High Risk City Floodway - Area of 100-year floodplain with greatest depths and fastest velocities. City Flood Fringe - May Include: - Areas of FEMA 100-year floodplain (FEMA Zones A, AE, AO, and AH) - Areas of City 100-year floodplain including ponding areas and sheet flow areas with average depths of 1-3 feet. There is a 1% annual chance that these areas will be flooded. Moderate Risk May include: - Areas of FEMA 500-year floodplain (FEMA Zone X-shaded). - Areas of FEMA or City 100-year floodplain (sheet flow) with average depths of less than 1 foot. - Areas protected by levees from the 100-year flood. Low Risk Areas outside of FEMA and City mapped 100-year and 500-year floodplains. Local drainage problems may still exist.. City Flood Risk Map This information is based on the Federal Emergency Management Agency (FEMA) Flood Insurance Rate Map (FIRM) and the City of Fort Collins Master Drainageway Plans. This letter does not imply that the referenced property will or will not be free from flooding or damage. A property not in the Special Flood Hazard Area or in a City Designated Floodplain may be damaged by a flood greater than that predicted on the map or from a local drainage problem not shown on the map. This map does not create liability on the part of the City, or any officer or employee thereof, for any damage that results from reliance on this information. All floodplain boundaries are approximate Feet Printed: 03/25/2016

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17 112 W Magnolia Street 35 C /18/2016

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20 Table RO-11 Rational Method Runoff Coefficients for Composite Analysis Character of Surface Streets, Parking Lots, Drives: Runoff Coefficient Asphalt 0.95 Concrete 0.95 Gravel 0.5 Roofs 0.95 Recycled Asphalt 0.8 Lawns, Sandy Soil: Flat <2% 0.1 Average 2 to 7% 0.15 Steep >7% 0.2 Lawns, Heavy Soil: Flat <2% 0.2 Average 2 to 7% 0.25 Steep >7% 0.35 (4) A new Section 2.9 is added, to read as follows: 2.9 Composite Runoff Coefficient Drainage sub-basins are frequently composed of land that has multiple surfaces or zoning classifications. In such cases a composite runoff coefficient must be calculated for any given drainage sub-basin. The composite runoff coefficient is obtained using the following formula: C n ( C A ) i * i= = 1 A t i (RO-8) Where: C = Composite Runoff Coefficient C i = Runoff Coefficient for Specific Area (A i ) A i = Area of Surface with Runoff Coefficient of C i, acres or feet 2 n = Number of different surfaces to be considered A t = Total Area over which C is applicable, acres or feet 2 (5) A new Section 2.10 is added, to read as follows: 41

21 Composite C Values WELLS FARGO PARKING EXPANSION Design Point Basin(s) Asphalt Area (acres) Concrete Area (acres) Gravel (acres) Pavers (acres) Lawns (acres) Total Area Minor (2-YR) Major (100-YR) (C = 0.95) (C = 0.95) (C = 0.50) (C = 0.50) (C = 0.15) (acres) Composite "C" Composite "C" (Cf x C) Existing P1 E Alley Alley Developed D1 B Alley Alley Notes: Composite C values obtained from Table R0-11 Major Storm Runoff factored per Table R0-12 MAP Wells Fargo Rational Method.xlsx 5/30/2017

22 Impeviousness WELLS FARGO PARKING EXPANSION Design Point Basin (s) Asphalt Area (acres) Concrete Area (acres) Gravel (acres) Pavers (acres) Lawns (acres) Total Area Percent Effective Impervious Area (I = 100) (I = 100) (I = 40) (I = 50) (I = 0) (acres) Imperviousness (S.F) Existing P1 E % 7, Alley Alley % Developed D1 B % 12, Alley Alley % 2, Notes: Percent Impervious Values per Table R0-11, Urban Drainage Manual CAG Wells Fargo Rational Method.xlsx 5/30/2017

23 Basin Flow Calculations WELLS FARGO PARKING EXPANSION Design Point Basin (s) Area Minor Major (acres) Composite "C" Composite "C" Length (ft) Slope (%) Initial/Overland Time Minor t ov (min) a Major t ov (min) a Length (ft) Slope (%) Channel Type Velocity (fps) c t t (min) Minor T C (min) Intensity (in/hr) Basin Flows (cfs) Major T C (min) 2-yr 10-yr 100-yr 2-yr 10-yr 100-yr Existing P1 E PA Alley Alley PA Developed D1 B PA Alley Alley PA Travel Time Final T C Notes: a t ov 1.87(1.1 CCf ) D 1 / 3 S 1/ 2 b HM = Heavy Meadow, TF = Tillage/field, PL = Short pasture and lawns, BG = Nearly bare ground, GW = Grassed Waterway, PA = Paved Areas c Velocity alues from Figure 3-3/Table RO-2 Estimate of Average Flow Velocity for use with the Rational Method CAG Wells Fargo Rational Method.xlsx 5/30/2017

24 APPENDIX B: Hydraulic Computations Modified FAA Method Orifice Sizing Calculation

25 DETENTION VOLUME BY THE MODIFIED FAA METHOD Project: Wells Fargo Parking Lot Improvements Basin ID: (For catchments less than 160 acres only. For larger catchments, use hydrograph routing method) (NOTE: for catchments larger than 90 acres, CUHP hydrograph and routing are recommended) Determination of MINOR Detention Volume Using Modified FAA Method Determination of MAJOR Detention Volume Using Modified FAA Method Design Information (Input): Design Information (Input): Catchment Drainage Imperviousness I a = percent Catchment Drainage Imperviousness I a = percent Catchment Drainage Area A = acres Catchment Drainage Area A = acres Predevelopment NRCS Soil Group Type = C A, B, C, or D Predevelopment NRCS Soil Group Type = C A, B, C, or D Return Period for Detention Control T = 2 years (2, 5, 10, 25, 50, or 100) Return Period for Detention Control T = 100 years (2, 5, 10, 25, 50, or 100) Time of Concentration of Watershed Tc = 11 minutes Time of Concentration of Watershed Tc = 11 minutes Allowable Unit Release Rate q = 1.05 cfs/acre Allowable Unit Release Rate q = 1.05 cfs/acre Determination of Average Outflow from the Basin (Calculated): Determination of Average Outflow from the Basin (Calculated): Runoff Coefficient C = 0.53 Runoff Coefficient C = 0.81 Inflow Peak Runoff Qp-in = 0.59 cfs Inflow Peak Runoff Qp-in = 3.53 cfs Allowable Peak Outflow Rate Qp-out = 0.46 cfs Allowable Peak Outflow Rate Qp-out = 0.46 cfs Mod. FAA Minor Storage Volume = cubic feet Mod. FAA Major Storage Volume = 2,235 cubic feet 5 <- Enter Rainfall Duration Incremental Increase Value Here (e.g. 5 for 5-Minutes) Rainfall Rainfall Inflow Adjustment Average Outflow Storage Rainfall Rainfall Inflow Adjustment Average Outflow Storage Duration Intensity Volume Factor Outflow Volume Volume Duration Intensity Volume Factor Outflow Volume Volume minutes inches / hr cubic feet "m" cfs cubic feet cubic feet minutes inches / hr cubic feet "m" cfs cubic feet cubic feet (input) (output) (output) (output) (output) (output) (output) (input) (output) (output) (output) (output) (output) (output) , , , , , , , , , , , , , , , , , , , , , , ,

26 Project: Date: By: /10/2017 RJP Orifice Calculator Directions: Input all known variables. Change the orifice diameter, D, to match Q all to Q req. Orifice Inputs Inputs Q req = 0.46 cfs D = 3.20 in (diameter of orifice) g = 32.2 ft/s 2 A o = ft 2 (area of orifice) H = 2.5 ft C d = 0.65 Q all = C d A o [(2gH)^1/2] Orifice Flow Calculation Q all = 0.46 cfs vs. Q req = 0.46 cfs Academy Court, #201 Fort Collins, CO (970)

27 Drainage Plan APPENDIX C: Map Pocket

28 (GAS) DRAINAGE LEGEND BASIN ID L.I.D. LEGEND FLOODPLAIN NOTES DRAINAGE AREA D1 MINOR "C" COEFFICIENT MAJOR "C" COEFFICIENT SYMBOL LEGEND ENGINEERING & SURVEYING 4045 St. Cloud Drive, Suite 180 Loveland, CO [P] [F] R/W E1 (UP) (UP) (UP) (UP) (UP) (UP) (UP) (UP) (UP) (UP) (UP) EXISTING STORM INLET D1 UNDERDRAIN S INV: 92.7' (UP) 4996 SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS 20.0' ROW (FO) (GAS) (GAS) (GAS) (GAS) (GAS) (GAS) (GAS) (GAS) (GAS) (GAS) (GAS) (GAS) (GAS) (GAS) (UP) (UP) 18.81' C/O INV: 93.77' UNDERDRAIN INV: 93.34' UNDERDRAIN INV: 93.30' FORT COLLINS 100-YEAR FLOODWAY (FO) 25.0' FORT COLLINS 100-YEAR FLOOD FRINGE (FO) 5 (FO) (UP) (FO) 4997 DRAINS TO PAVER SECTION #1 C/O INV: 93.11' UNDERDRAIN INV: 92.89' 5.0' AREA = 1,146 SQ FT PAVER SECTION # (FO) DRAINS TO STREET AREA = 598 SQ FT (FO) 11 (UP) (UP) (UP) PLANTING AREA (FO) (FO) (FO) (GAS) (GAS) (GAS) (GAS) (GAS) (GAS) (GAS) (GAS) (GAS) (GAS) (GAS) (GAS) (GAS) FO EXISTING BUILDING (UP) 7 (UP) (UP) (UP) 11 (UP) (UP) (UP) (UP) (UP) (UP) (UP) (UP) (UP) (UP) (UP) (UP) (UP) (UP) (UP) (UP) (UP) (FO) (FO) (FO) (FO) (FO) (FO) (FO) (FO) (FO) W W W W W W W W W W W W W W W W W W MAGNOLIA STREET DRAINS TO PAVER SECTION #2 AREA = 2,771 SQ FT 24.0' 24.0' 24.0' 24.0' FORT COLLINS MODERATE RISK FLOODPLAIN FORT COLLINS 100-YEAR FLOOD FRINGE UNDERDRAIN INV: 93.03' PROPOSED 18" CATCH BASIN ' TYP UNDERDRAIN INV: 93.29' 64.2' 5.0' 11.5' 4996 PAVER SECTION #2 C/O INV: 93.51' 9.0' TYP UNDERDRAIN INV: 93.33' UNDERDRAIN INV: 93.33' ' 4995 LANDSCAPING AREA 4996 UNDERDRAIN INV: 93.57' UNDERDRAIN INV: 93.61' DRAINS TO PAVER SECTION #3 PAVER SECTION #3 30.9' AREA = 2,811 SQ FT C/O INV: 93.75' UNDERDRAIN INV: 93.61' FORT COLLINS MODERATE RISK FLOODPLAIN 6.5' LINCOLN CENTER FLOODPLAIN REVISION HEC-RAS MODEL CROSS-SECTION RIVER: MAGNOLIA7 REACH: MASON-COLLEGE RIVER STATION: 2068 BASE FLOOD ELEVATION: ' FORT COLLINS 100-YR FLOOD FRINGE 6.0' 4996 DRAINS TO PAVER SECTION #4 AREA = 1,246 SQ FT FORT COLLINS 100-YEAR FLOOD FRINGE FORT COLLINS 100-YEAR FLOODWAY 8.0' 8.0' 8.0' PAVER SECTION #4 8 (OHP) (OHP) (OHP) VB (OHP) (OHP) (GAS) (GAS) (GAS) (GAS) (GAS) (GAS) (GAS) 11.5' 6.0' C/O INV: 94.22' UNDERDRAIN INV: 93.83' UNDERDRAIN INV: 93.79' 5.0' PROPERTY LINE (UP) (UP) (UP) (UP) (UP) (UP) W W W W W W W W W W W W W (FO) (FO) (FO) (FO) (FO) (FO) (FO) (FO) (FO) (FO) (FO) (FO) (FO) (FO) W W FORT COLLINS 100-YEAR FLOOD FRINGE FORT COLLINS 100-YEAR FLOODWAY N 0 10' 20' G R G (UP) (UT) SS X WS WS WS WS WS W (OHP) WS W FS SS R/W E E E % 11 W FOR BURIED UTILITY INFORMATION THREE (3) BUSINESS DAYS BEFORE YOU DIG CALL 811 (OR ) UTILITY NOTIFICATION CENTER OF COLORADO (UNCC) CITY OF FORT COLLINS, COLORADO UTILITY PLAN APPROVAL 112 W. MAGNOLIA ST. PARKING 112 WEST MAGNOLIA STREET FORT COLLINS CO, DRAINAGE PLAN SCALE: 1" = 10' C5.0