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HomeMy WebLinkAboutJEFFERSON COMMONS PUD - PRELIMINARY - 50-95 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE RELATED DOCUMENTPROJECT: -JPI Multi -Family, Inc. Student Housing SEQUENCE FOR 1996-97 ONLY COMPLETED BY: Chris Carlson DATE: 11/20/95 Indicate by use of a bar line or symbols when erosion control measures will be installed. Major modifications to an approved schedule may require submitting a new schedule for approval by the City Engineer. July Aug. Sept. Oct. Nov. Dec. Jan. Feb. to June OVERLOT GRADING WIND EROSION CONTROL Soil Roughing Perimeter Barrier Vegetative Methods Mulching / Sealant RAINFALL EROSION CONTROL STRUCTURAL: Detention Pond Pond Outlet Filters Straw Barriers Silt Fence Barriers Sand Bags Bare Soil Preparation Contour Furrows Asphalt / Concrete Paving VEGETATIVE: Permanent Seed Planting Mulching / Sealant Temporary Seed Planting Sod Installation Nettings / Mats / Blankets BUILDING CONSTRUCTION: STRUCTURES: INSTALLED BY: Contractor VEGETATION / MULCHING CONTRACTOR: Contractor DATE SUBMITTED: 11/20/95 MAINTAINED BY: Contractor APPROVED BY CITY OF FORT COLLINS Figure 6. Construction schedule. 14 Ayres Associates The furthest upstream crossing will require 3 3-foot by 7-foot box culverts. A complete hydraulic analysis and design will be completed for the final submittal. Design of the spillways and outlet pipe profiles will also be completed for the final submittal. EROSION CONTROL PLAN Overview JPI Multi -Family, Inc. Student Housing will be an 16.7 net acre development on moderate erodibility soil. Overlot grading will begin in July 1996, with building construction to begin in November 1996 (Figure 6). Both proposed wind and water erosion control measures will be addressed in this plan; however, calculations will be completed only for the final submittal. Wind Erosion Since construction will occur during the winter and spring months, effective wind erosion plans must be established. On moderate erodibility soil, significant erosion could occur without steps taken to protect the soil. Those portions of all basins not covered with pavement, concrete, or buildings will have 2 tons/acre of straw mulch applied for water erosion control, which also meets the requirements for minimum wind erosion protection. All mulches -will be properly anchored. Rainfall Erosion Runoff leaves the site in three areas: (1) overland flow into the drainageway, (2) sheetflow across the southeast property line, and (3) onto West Elizabeth Street. Measures will be taken to prevent sediment from leaving the site at these areas. A silt fence, which will prevent sediment from flowing off the property will be placed along the eastern property line from Elizabeth to Plum Streets. The swales that run to the main detention pond (element 144) will contain straw bale dikes, as will the drainageway itself. These dikes will be placed no more than 100 feet apart in accordance with City of Fort Collins Storm Drainage Design Criteria procedures. During overlot and final grading, the soil will be roughened and furrowed perpendicular to the prevailing winds (northwest to southeast). All areas not covered by asphalt, concrete, or foundations will have 2 tons/acre of straw mulch either crimped 4 or more inches into the soil or sprayed with a tackifier. After the detention outlet pipes are completed, gravel filters will be installed at the pipes' inlets. The two curb inlets on Orchard Place will also have gravel inlet filters. All filters will remain in place until construction is complete. With proper precautions, damage to off -site areas from a greater than historic sediment load �i can be eliminated and the loss of sediment from the site minimized. Calculations for performance standards and effectiveness will be submitted with the final drainage and erosion control plan. 13 Ayres Associates Table 6. Detention Pond 172 Outlet Rating Curve. Water Surface Elevation Pond Volume (ac-ft) Released Q (cfs) 77.50 0.000 0.00 78.00 0.017 0.27 78.50 0.079 0.45 79.001 0.140 0.59 100-Year WSEL = 78.61 1 100-Year Volume = 0.092 100-Year Q = 0.48 The northern detention pond, element 170, was sized to contain the 100-year storm runoff from subbasin 79. Runoff will enter the pond through overland flow from the tennis courts. For a 3-hour, 100-year storm, the detention pond must detain 0.079 ac-ft of water. The 100-year water surface elevation is 76.67, corresponding to a maximum depth at the outlet of 1.87 feet. For a 3-hour, 2-year storm, the detention pond must detain 0.016 ac-ft of water. The 2-year water surface elevation is 75.38, corresponding to a maximum depth of 0.58 foot. The pond's outlet structure will consist of a 10-inch diameter ADS N-12 pipe and 3-inch diameter orifice. The outlet pipe connects to the north inlet on Orchard Street. The maximum rate at which water will be released from the pond is 0.14 and 0.30 cfs during the 2- and 100-year storms, respectively. Detention pond 170's outlet rating curve is shown in Table 7. Table 7. Detention Pond 170 Outlet Rating Curve. Water Surface Elevation Pond Volume (ac-ft) Released Q (cfs) 74.80 0.000 0.00 75.00 0.002 0.08 76.00 0.040 0.24 77.0010.098 1 0.33 100-Year WSEL = 76.67 1 100-Year Volume = 0.079 1 100-Year Q = 0.30 Two type R curb inlets under sump conditions will be placed on Orchard Place to prevent excessive water from flowing down the existing Orchard Place and having negative impacts on the street capacity. Each inlet will be 13-feet long and remove the 100-year runoff from the street. The north inlet, element 168, empties into a 15-inch diameter RCP storm drain that runs under Orchard Place to the south inlet. The outlet pipe from detention pond 170 daylights in this inlet box. Flow through the south inlet combines with that from the 15-inch RCP and empties into an 18-inch ADS N12 pipe which runs to the drainageway. Preliminary calculations show that the drainageway (at element 150) has a normal depth of 1.11 and 2.68 feet during 2- and 100-year flows, respectively. The 100-year flow at element 150 is 319 cfs. With a maximum depth of 3.0 feet, the drainageway has a capacity of 397 cfs. Three box culvert crossings will be placed in the drainageway. Under inlet control, 3 3- foot by 8-foot box culverts will be required at the furthest downstream and middle crossing. 12 Ayres Associates �I The central detention pond, element 144, was sized to contain the 100-year storm runoff from subbasins 60, 61, 62, 63, 64, 65, 66, and 67. Runoff will enter the pond through 6 � swales and overland flow. For a 3-hour, 100-year storm, the detention pond must detain 1.240 acre-foot (ac-ft) of water. The 100-year water surface elevation is 77.88, corresponding to a maximum depth at the outlet of 3.08 feet. For a 3-hour, 2-year storm, the detention pond must detain 0.312 ac-ft of water. The 2-year water surface elevation is 76.25, corresponding to a maximum depth of 1.45 feet. The pond's outlet structure will consist of an 18-inch diameter ADS N-12 pipe and 14-inch diameter orifice. The outlet pipe daylights at the drainageway. To reduce the rate of low flows leaving the pond, a 1.5-foot high weir structure will be built around the outlet pipe. A 3-inch diameter PVC pipe allows nuisance flows through the weir and the detention pond to completely drain. As water ponds over 1.5 feet high, it will flow over the weir and into the outlet pipe. During large storm events, such as the 100-year storm, water will flow over the weir at an increasing rate until the orifice becomes the controlling structure. The maximum rate at which water will be released from the pond is 0.90 and 8.33 cfs during the 2- and 100-year storms, respectively. The central detention pond's outlet rating curve is shown in Table 5. Table 5. Central Detention Pond, #144, Outlet Rating Curve. Water Surface Elevation Pond Volume (ac-ft) Released Q (cfs) 74.80 0.000 0.00 75.00 0.004 0.08 75.80 0.157 0.24 76.00 0.195 0.31 76.50 0.432 1.51 77.00 0.669 5.78 77.50 0.994 7.30 78.00 1.319 8.66 100-Year WSEL = 77.88 100-Year Volume = 1.240 100-Year Q = 8.33 A 20-foot wide by 0.30-foot deep overflow spillway will be located above the pond's outlet structure. The spillway, set at elevation 78.00, would release water into the drainageway if the orifice clogged during the 100-year storm. The western detention pond, element 172, was sized to contain the 100-year storm runoff from subbasin 69. Runoff will enter the pond through a curb culvert and overland flow. For a 3-hour, 100-year storm, the detention pond must detain 0.092 ac-ft of water. The 100- year water surface elevation is 78.61, corresponding to a maximum depth at the outlet of 1 1.11 feet. For a 3-hour, 2-year storm, the detention pond must detain 0.012 ac-ft of water. The 2-year water surface elevation is 77.85, corresponding to a maximum depth of 0.35 foot. The pond's outlet structure will consist of an 12-inch diameter ADS N-12 pipe and 4.5- inch diameter orifice. The outlet pipe daylights at the drainageway. The maximum rate at which water will be released from the pond is 0.19 and 0.48 cfs during the 2- and 100-year storms, respectively. Detention pond 172's outlet rating curve is shown in Table 6. 11 Ayres Associates Table 4. SWMM Results Comparison. Master Plan Master Plan Master Plan with JPI Element Description (FullyyDevelo(Existing Conditions an JPI Site(Fully Developed) 2-Year 100-Year 2-Year 100-Year 2-Year 100-Year cfs cfs ds crs Us cfs 85 Flow entering JPI property in 60 305 60 305 60 305 drainageway 88/152 Flow leaving JPI property in 67 335 62 • 328 64 323 drainageway 90 Flow on Orchard Place at Taft 6 31 6 31 6 32 Hilt 89 Flow in drainageway at Taft 69 344 63 338 66 333 Hill 99 Flow In drainageway below 83 391 77 387 82 382 Taft Hill 101 Flow in drainageway at 93 448 88 447 92 444 Glenmoor Drive - 107 Flow in drainageway west of 105 521 100 525 104 520 Skyline Drive 112 Flowinto regional detention 111 550 107 555 110 552 208 Regional detention pond 62. 2.6 196, 26.8 60, 2.4 192, 26.5 61. 2.5 189, 26.3 ds, ac-ft Runoff from subbasins 71, 74, and 81 flow directly into the drainageway. These areas are primarily grassed and landscaped. Runoff from subbasins 72, 73, and 75 flow off the parking lots, through curb culverts, and into the drainageway. That area representing Orchard Place along the northern property line, subbasins 77 and 78, contribute runoff that flows easterly down the street gutters to curb inlets, which transfer the water via stormdrain to the major drainageway. Detention pond 170 detains runoff from the tennis courts, subbasin 79, and releases it at a controlled rate. The pond's outlet pipe ties into the north inlet, element 166, and flows through the same stormdrain pipes to the major drainageway. A portion of area, subbasin 80, contributes a small amount of runoff r onto Orchard Place that flows eastward off the property. The additional undetained flow does not negatively effect Orchard Place through Sunray Place Apartments. Subbasin 76, which represents a small amount of land between a retaining wall and the eastern property line, will be graded such that runoff will flow along the property boundary to the drainageway. Part of this strip of land cannot be graded to drain toward the drainageway. This area, which lies in the southeast comer, flows eastward across the property boundary. It has no effect on West Elizabeth Plaza, subbasin 37. STORM DRAINAGE FACILITIES A major portion of drainage flows off of parking lots through sidewalk or curb culverts. The culverts are labeled on the enclosed grading and drainage plan, along with a table showing �! their respective lengths. All culverts are either 2- or 4-foot long. All drainage swales in the development will have a 2-foot wide concrete trickle pan and 5 to 1 side slopes. They will contain the 100-year runoff with a minimum of 33 percent additional capacity. Where the swales cross sidewalks, sidewalk culverts with convey the water underneath. Due to steep bank slopes, riprap protection will be provided where swales empty into the central detention pond. I10 Ayres Associates Table 3. Conveyance Elements and Peak Discharges. Gutter Connected To: Type Width or Dia. (ft) Length (ft) Slope (ft(ft) Side Slopes Manning n Peak Discharge Left H: Right H: 2-Year ds 100-Year cfs 130 162 Channel 20.0 185 0.018 50 50 0.020 3 12 162 131 Street Detention 3 11 131 143 Channel 2.0 207 0.011 5 5 0.060 2 10 132 161 Channel w/ Overflow 0.5 163 0.010 0 12 0.016 2 8 5.01 163 0.010 20 20 0.020 133 161 Channel w/ Overflow 0.5 235 0.012 0 12 0.016 2 8 5.0 235 0.012 20 20 0.020 161 134 Street Detention 3 15 134 142 Channel 2.0 111R007 5 5 0.060 3 15 142 143 Channel 10.0 124 20 20 0.040 3 14 135 - 160 Channel w/ Overflow 0.5 190 0 12 0.018 2 9 5.0 190 20 20 0.020 160 136 Street Detention 2 4 136 143 Channel 2.0 86 5 5 0.060 2 4 139 163 Channel w/ Overflow 0.5 146 0 12 0.016 2 11 5.0 146 20 20 0.020 163 140 Street Detention - - 2 10 140 143 Channel 2.0 117 0.0131 51 5 0.060 2 10 143 144 Channel 20.0 235 0.0071 111 11 0.040 8 36 141 164 Channel w/ Overflow 0.5 173 0.013 0 12 0.016 2 6 5.0 173 0.013 20 20 0.020 164 14{ Street Detention - - 2 6 1371 138 1 Channel w/ Overflow 0.5 62 0.003 0 12 0.016 1 3 5.0 62 0.003 20 20 0.020 144 Channel 2.0 59 0.010 5 5 0.060 1 3 157 Detention Pond - 1 8 148 Detention Pond - - 0 0 P144 149 Channel w/ Overflow 0.5 134 0.005 0 12 0.016 1 3 5.0 134 0.005 20 20 0.020 149 Channel w/ Overflow 0.5 122 0.008 0 12 0.016 1 2 5.0 122 0.008 20 20 0.020 1481 149 1 Channel w/ Overflow 10.01 75 0.008 5 3 0.040 61 305 25.0 75 0.008 100 100 0.080 149 158 Channel w/ Overflow 20.0 183 0.008 4 5 0.040 61 309 25.0 183 0.008 30 100 0.080 157 158 Pi w/ Overflow 1.8 226 0.004 0 0 0.020 1 8 10.0 226 0.004 20 20 0.040 158 150 Channel w/ Overflow 20.0 79 0.008 41 5 0.0401 61 316 20.0 79 0.008 50 100 0.080 147 165 Channel w/ Overflow 0.5 260 0.004 0 12 0.016 2 9 5.01 260 0.004 20 20 0.020 165 150 Street Detention 1 5 150 151 Channel w/ Overflow 20.0 208 0.007 3 3 0.040 63 319 100.0 208 0.007 50 50 0.060 153 151 Channel w/ Overflow 0.5 130 0.004 0 12 0.016 1 3 5.0 130 0.004 20 20 0.020 154 159 Channel 1.0 173 0.0121 251 20 0.0201 1 6 159 152 Street Detention 1 5 155 167 Channel w/ Overflow 0.5 493 0.012 0 12 0.016 1 4 5.0 493 0.012 20 20 0.020 166 Channel w/ Overflow 0.5 513 0.011 0 12 0.016 1 4 5.0 513 0.011 20 20 0.020 169 Diversion To 168 - Curb Inlet 1 4 169 Diversion To 171 - Curb Inlet - - 1 4 P167 168 Pi 1.3 40 0.004 0 0 0.016 1 4 169 Detention Pond - - 0 0 90 Channel 2.0 115 0.008 30 30 0.020 0 2 151 Pi 1.8 120 0.004 0 0 0.018 2 8 152 Channel 18.0 81 0.007 0 0 0.020 64 321 152 69 Channel w/ Overflow 10.0 32 0.007 3 3 0.040 84 323 10.0 32 0.007 151 151 0.080 Ayres Associates Table 1. Subcatchment Constants. Parameter Value Manning's n for impervious surfaces 0.016 Manning's n for pervious surfaces 0.25 Surface retention storage for impervious surfaces 0.1 in. Surface retention storage for pervious surfaces 0.3 in. Maximum infiltration rate 0.51 in./hr Minimum infiltration rate 0.5 in./hr Decay rate 6. 0018 Storm duration 3 hours Time step 1 minute Table 2. Basin Parameters. Subcatchment Connected To: Width (ft) Area (ac) Percent Impervious N Slope (ft/ft) 60 130 463 1.699 50 0.017 61 132 233 1.230 50 0.020 62 133 437 1.043 50 0.018 63 135 479 1.155 601 0.014 64 137 362 0.374 60 0.010 65 139 538 1.483 50 0.024 66 -141 320 0.807 60 0.019 67 144 780 1.702 15 0.062 68 145 223 0.307 70 0.011 69 172 117 0.733 351 0.010 70 146 74 0.254 90 0.009 71 149 353 1.295 15 0.027 72 147 426 1.116 70 0.021 73 153 202 0.348 70 0.020 74 150 380 0.349 5 0.132 75 154 476 0.711 601 0.036 76 152 18 0.161 5 0.028 77 155 993 0.456 66 0.020 78 156 1178 0.541 53 0.020 79 170 101 0.508 68 0.004 80 169 317 0.197 56 0.025 81 148 43 0.2251 5 0.022 8 Ayres Associates Z r w Z 2 O w 0 d J w Z Z Z w a _o 0 U H H Z Z Q U Q O W } - H it W Z Z p in z F u 3 Q o ii Z o on U O J U Li Z W (Db w J O � N U f6 N L U N i U) a) A:: fR L6 N 7 O) iT 7 Ayres Associates LL M. Ayres Associates Results indicate a 29 cfs runoff from south of the drainageway (Subbasin 32) and 12 cfs from north of the drainageway (subbasin 33) during the 100-year storm. The total flow in the drainageway leaving the site is 328 cfs (element 88). During the 2-year storm event, the peak runoff from subbasin 32 is 4 cfs and 1 cfs from subbasin 33. The total flow in the drainageway leaving the site is 62 cfs (element 88). SWMM output is shown in the Appendix. PROPOSED DRAINAGE CONDITIONS A detailed grading, drainage, and erosion control plan (enclosed in pocket) shows the building layout and storm drainage facilities that will be used for JPI Multi -Family, Inc. Student Housing. The map uses a 1-foot contour interval. Schematics of the proposed conditions SWMM network and the JPI site SWMM network are shown in Figures 4 and 5, respectively . . The JPI Multi -Family, Inc. Student Housing property consists of 22 subbasins that contribute drainage to separate outlets from the property. Design points were identified at all locations where storm runoff will leave the property. SWMM, which was used to determine the existing condition runoff and the Master Plan hydrologic analysis, was used to determine the proposed condition 2- and 100-year peak discharges, detention pond volumes, and downstream effects. Subcatchment constants are shown in Table 1, basin parameters in Table 2, and conveyance elements and runoff in Table 3. A comparison of SWMM results between the Master Plan fully developed model and the JPI fully developed model is shown in Table 4. In the southwest corner of the property, subbasin 60 contributes runoff primarily from parking areas and an off -site lot. Drainage flows northeasterly through a 4-foot sidewalk culvert near the parking lot corner. A grass -lined swale with trickle pan conveys the water into the central detention pond. Subbasins 61 and 62 represent area along West Elizabeth Street that flows north away from the street. Runoff enters a swale through a 4-foot sidewalk culvert (labeled SC6) and flows to the central detention pond. Runoff from subbasins 63, 64, 65, and 66 flows across parking lots to sidewalk culverts. Swales convey the runoff from each sidewalk culvert to the central detention pond. The central detention pond, element 144, detains runoff from subbasins 60, 61, 62, 63, 64, 65, 66, and 67. It releases the stored water into the major drainageway at a reduced rate. Subbasin 69 contributes runoff to a second detention pond, element 172, which lies along the western property boundary. Stored water is released into the major drainageway at a reduced rate. Subbasins 68 and 70, which are primarily parking lots, contribute water undetained into the major drainageway. The runoff flows to a curb culvert on the furthest upstream box culvert, where it spills into the drainageway. 5 Ayres Associates CSU EQUESTRIAN CENTER m PLEASANT VALLEY AND ` LAKE CANAL 12 , ® H PROPOSED .. DETENTI01��` . <POND 1 z \ W \ 0 11 \ vi � PROPOSEDi� SCENIC VIEWS SUBDIVISION LEGEND STREET SUBCATCHMENT BASIN BOUNDARY — — — — — — CHANNEL OR GUTTER 11 BASIN LABEL ® CONVEYANCE ELEMENT OP05 DETENTION POND • CONCENTRATION POINT R KIMBALL DETENTION C 14 POND i � 1r 15 x r 0 z 600 300 0 600 SCALE: I"=600' NEW MERCER CANAL PEAR DETENTION] m Mk, m m POND a r' •RESTMORE PL�] I I ME rips] �1 ... I �`a �J[:fi/ rEa Sri ®le:lil �E:b1 . 4N1 �b7 -ELEMENTARY1 ® filSCHOOL ' C • T'�� `� APARTMEPLUM iffoUl mw DETENTION PROPOSE7D tu STU a t 1n HOUSINGENT •i' ; h DEVELOPMENT N 0 in 0 N m V a _ 1LOpo M 1 © 00 ® FFO-1 I 01 © O M '� r N � Q M N � 01 M �— O N O a } R w z �\ LLI 2 J O ILp a Go W W Z O a Z o Z 0 LO 06 v " z a z O a Cr u w 0� } w z z z z o M 96 © M N a Z O r w L) z 3 o 00 U in O J m z w f � M w I J Jv� 00 m N M M M PitN N N rm N � N1 1 A© N N ~ O bL M N _ U f�6 d L U N 07 0 w a c O U C N X C Z (6 (6 L (D 0 a) L E 3 Ayres Associates N PROJECT LOCATION MULBERRY 11 11 "�<F I I ST. TO 1-25 v LAUREL ST. COLORADO W. ELIZABETH UNIVERSTYFwF,R.:s,TErT CAMPUS Q RD TOI-25 0 Z Q J 0 { W W O K N > > W Q Q > DRAKE RD. r Q Li Li J HORESETOOTH RD. J w _J V, W = N Li!/ 2 F -i J J W w J Q K Q = O w F N Q m ti HARMONY RD. r TO I-25 FRONCCANGE IF I� VICINITY MAP N.T.S. Figure 1. Vicinity map. Ayres Associates i INTRODUCTION This report summarizes the storm drainage investigations performed for the proposed JPI Multi -Family, Inc. Student Housing in Fort Collins, Colorado. A hydrologic analysis of the proposed development was completed to determine the magnitude and location of storm runoff, allowable release rates into an existing drainageway, develop detention ponds, and determine downstream effects of the proposed development. This study and drainage plan was prepared to meet City of Fort Collins Storm Drainage Design Criteria for the development. The JPI Multi -Family, Inc. Student Housing is located along the north side of West Elizabeth ' Street approximately 1,000 feet west of Taft Hill Road as shown in Figure 1. It consists of approximately 16.7 acres occupying the northeast quarter of Section 16, Township 7 North, Range 69 West, of the 6th Principal Meridian and lies within the West Plum Street basin. ' PREVIOUS STUDIES ' Previous drainage, studies of the area include (1) West Plum Street Basin Master Drainage Plan (RCI 1990), and (2) Update of Hydrologic Analysis for West Plum Street Basin (Ayres Associates 1995). 'These were reviewed to assist with the preparation of this report. ' EXISTING DRAINAGE CONDITIONS The JPI Multi -Family, Inc. Student Housing site lies along the north side of West Elizabeth Street, approximately 1,000 feet west of Taft Hill Road. Skyline Mobile Home Park lies to the north, Sunray Place Apartments and West Elizabeth Plaza to the east, and Miller- ' Layland subdivision to the west. A major drainageway runs eastward across the property from Miller-Layland to the Sunray Place Apartments. The drainageway is constricted and improved both up- and downstream, but remains unimproved on the site. The majority of ' runoff flows to this drainageway. Along West Elizabeth Street, there are two small houses, several sheds, and a horse corral. An irrigation/drainage ditch lies between these houses and Elizabeth Street. The ditch is overgrown with vegetation, filled with debris, and appears to be unused with the exception of storm drainage that it collects off of Elizabeth Street. The ditch dead ends at the West Elizabeth Plaza boundary where curb and gutter begin. Curb and gutter have not been installed along Elizabeth Street adjacent to the property. ' Except for the two houses and a horse corral, the site is currently at historic conditions covered with native grasses. Existing runoff calculations were performed to determine the 2- and 100-year runoffs for the ` site using the Storm Water Management Model (SWMM, UDFCD 1985). A schematic showing the linkages of the subcatchments and conveyance elements for the existing j' conditions is shown in Figure 2. The overall basin is shown in Figure 3. Both figures contain information from the West Plum Street Master Drainage Plan SWMM model. The hydrologic analysis used the Master Plan SWMM model with those subcatchments representing the JPI Student Housing site altered to reflect existing conditions. ' 1 Ayres Associates TABLE OF CONTENTS INTRODUCTION..................................................................................................................1 PREVIOUSSTUDIES...........................................................................................................1 EXISTING DRAINAGE CONDITIONS..................................................................................1 PROPOSED DRAINAGE CONDITIONS...............................................................................5 STORM DRAINAGE FACILITIES................................................................................:......10 EROSION CONTROL PLAN...............................................................................................13 Overview.........................................................................................................................13 WindErosion...................................................................................................................13 RainfallErosion...............................................................................................................13 APPENDIX........................................................................................................................... -- LIST OF FIGURES Figure1. Vicinity map..........................................................................................................2 Figure 2. Overall basin existing conditions SWMM schematic.............................................3 Figure 3. West Plum Street basin........................................................................................4 Figure 4. Overall basin proposed conditions SWMM schematic...........................................6 Figure 5. JPI site SWMM schematic....................................................................................7 Figure 6. Construction schedule.........................................................................................14 LIST OF TABLES Table 1. Subcatchment Constants.......................................................................................8 Table 2. Basin Parameters...............:...................................................................................8 Table 3. Conveyance Elements and Peak Discharges.........................................................9 Table 4. SWMM Results Comparison................................................................................10 Table 5. Central Detention Pond, #144, Outlet Rating Curve.............................................11 Table 6. Detention Pond 172 Outlet Rating Curve.............................................................12 Table 7. Detention Pond 170 Outlet Rating Curve.............................................................12 i Ayres Associates /SIRES ASSOCIATES November 9, 1995 Mr. Basil Hamdan City of Fort Collins Stormwater Utility 235 Mathews Street Fort Collins, Colorado 80524 Re: JPI Multi -Family, Inc. Student Housing Dear Basil, Enclosed please find our "Preliminary Grading and Drainage Report For JPI Multi -Family, Inc. Student Housing." This report was prepared in accordance with the City of Fort Collins Storm Drainage Criteria as revised in May 1991. We appreciate your time and consideration in reviewing this submittal. Please call if you have any questions. Sincerely, Owen Ayres & Associates, Inca C ris Carlso , E.I.T. C vJin Scott Quee , P.E. Civil Enaineer CC/SQ/sp Enclosure Owen Ayres & Associates, Inc. Engineers/Scientists/Surveyors 3665 JFK Parkway, Building 2, Suite 300, P.O. Box 270460, Fort Collins;CO 80527 (970) 223-5556, Denver Metro (303) 572-1806, FAX (970) 223-5578 Printed on recycled paper HAMD11 B.LTR 34-0276.00 RELIMINARY GRADING AND DRAINAGE REPORT FOR JPI MULTI -FAMILY, INC. STUDENT HOUSING Prepared for JPI Texas Development P.O. Box 619208 Dallas, Texas 75261-9208 AVMmS ASSOCIATES P.O. Box 270460 Fort Collins, Colorado 80527 AWES(970) 223-5556, FAX (970) 223-5578 ASSOCIATES