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Home My WebLink AboutDrainage Reports - 07/19/2013City of Ft Colli prov Plans Approved By �t Date :7:--19-13 FINAL DRAINAGE AND EROSION CONTROL STUDY PRESTON CENTER THIRD FILING LOT 7 PRESTON 7 Prepared for: Ric Flattman Hattman Associates 145 W Swallow Road 0 A4 Fort Collins, CO (970)223-7335 Prepared by: North Star Design, Inc. 700 Automation Drive, Unit I Windsor, Colorado 80550 (970)686-6939 April 28, 2013 Revised June 5. 2013 Revised July 17, 2013 Job Number 345-01 r I I I .1 r FINAL DRAINAGE AND EROSION CONTROLSTUDY PRESTON CENTER THIRD FILING LOT 7 PRESTON 7 Prepared for: Ric Hattman Hattman Associates 145 W Swallow Road # A4 Fort Collins, CO (970)223-7335 Prepared by: North Star Design, Inc. 700 Automation Drive, Unit I Windsor, Colorado 80550 (970) 686-6939 April 28, 2013 Revised June 5, 2013 Revised July 17, 2013 Job Number 345-01 u I %North Star ' design 700 Automation Drive, Unit I ' Windsor, CO 80550 Phone:970-686-6939 Fax: 970-686-1188 [1 I I n 1 i L July 17, 2013 Glen Schlueter City of Fort Collins Stormwater 700 Wood Street Fort Collins, CO 80522-0580 RE: Final Drainage and Erosion Control Study for Preston Center Third Filing, Lot 7 Dear Glen, I am pleased to submit for your review and approval, this Final Drainage and Erosion Control Study for Preston Center Third Filing, Lot 7. I certify that this report for the drainage design was prepared in accordance with the Overall Drainage Report for the Preston Center Third Filing and the criteria in the City of Fort Collins Storm Drainage Manual. I appreciate your time and consideration in reviewing this submittal. Please call if you have any questions. Patricia Kroetch, n ��1 TABLE OF CONTENTS TABLEOF CONTENTS............................................................................................................... iii 1. GENERAL LOCATION AND DESCRIPTION 1.1 Location ............................. :...................................................................................... 1 1.2 Description of Property............................................................................................ I 2. DRAINAGE BASINS AND SUB -BASINS 2.1 Major Basin Description..........................................................................................1 2.2 Sub -Basin Description.............................................................................................2 3. DRAINAGE DESIGN CRITERIA 3.1 Regulations..............................................................................................................2 3.2 Development Criteria Reference and Constraints...................................................2 3.3 Hydrologic Criteria..................................................................................................2 3.4 Hydraulic Criteria....................................................................................................3 4. DRAINAGE FACILITY DESIGN 4.1 General Concept......................................................................................................3 4.2 Specific Flow Routing.............................................................................................3 4.3 Drainage Summary..................................................................................................4 5. STORMWATER MANAGEMENT CONTROLS 5.1 Written Analysis.....................................................................................................4 5.2 SWMP Contact Information...................................................................................5 5.3 Identification and location of all potential pollution sources..................................6 5.4 Best Management Practices (BMP's) for Stormwater Pollution Prevention ........... 6 5.5 BMP Implementation.............................................................................................10 6. CONCLUSIONS 6.1 Compliance with Standards..................................................................................13 6.2 Drainage Concept..................................................................................................13 7. REFERENCES..................................................................................................................12 APPENDICES A Vicinity Map B Hydrologic Computations C Excerpts from Previous Reports iii 11 GENERAL LOCATION AND DESCRIPTION 1.1 Location ' The Preston 7 site is located on Lot 7 of the Preston Center Third Filing. This project is located in Section 5, Township 6 North, Range 68 West of the Sixth Principal Meridian, in the City of Fort Collins, Larimer County, Colorado. See the location map in Appendix A. The project is located south of Harmony Road between Gifford Court and Zeigler Road. ' The project is bounded on the north by an irrigation ditch, on the south and east by existing office buildings and on the west by Gifford Court. ' 1.2 Description of Property The entire site consists of approximately 1.7 acres of land. The land is currently undeveloped and falls to the southeast at slopes ranging from approximately 1% to 3% and will flow to an existing detention pond in Basin 110 of the Preston Center Third Filing. Portions of this site drain to the north and west and offsite. This pond was sized by JR Engineering in conjunction with the drainage study for the overall Preston Center Third Filing. This pond is not being modified with this development and the original volume will be maintained. This project will include the development of a multi -tenant building, parking, private drives and a drive through lane. The site will continue to drain to the existing detention pond as intended by the original Third Filing report. 2. DRAINAGE BASINS AND SUB -BASINS ' 2.1 Major Basin Description ' The proposed development lies within the McClellands Drainage Basin. Preston Center Third Filing, including this site, lies within McClellands Creek Master Drainage Plan. 2.2 Sub -basin Description L This site (Lot 7) is included in the "Final Drainage and Erosion Control Study for Preston Center Third Filing" by JR Engineering dated July 12, 2000. The report includes Lot 7 in Basin 110 and the detention pond is shown in Basin 110. 1 n 3. DRAINAGE DESIGN CRITERIA 3.1 Regulations This report was prepared to meet or exceed the "City of Fort Collins Storm Drainage Design Criteria Manual" specifications. Where applicable, the criteria established in the "Urban Storm Drainage Criteria Manual" (UDFCD), 1984, developed by the Denver Regional Council of Governments, has been used. 3.2 Development Criteria Reference and Constraints The runoff from this site has been routed to conform to previous calculations completed ' with the Preston Center Third Filing report. The model included in this report limits Basin 101 to a 10 year C-value of 0.80 and a 100 C-value of 1.00. The site as proposed has a 10 year C-Value of 0.72 and 100 year C-Value of 0.79 which are well under the values assumed in the overall drainage report for Preston Center Third Filing. Based on these values, the detention pond provides adequate detention for the developed site as indicated in the JR report, therefore no additional detention is being provided with this development. ' Runoff from the onsite detention pond is released east under Timberwood Drive and enters Pond 305. This pond releases water into an existing storm system along the west side of Zeigler Road. 3.3 Hydrologic Criteria Runoff coefficients calculations were prepared for the 10-year minor and 100-year major ' storm frequency utilizing the rational method. Since the runoff coefficients were less than allowed by the overall Third Filing report, no additional runoff calculations were completed. ' The drainage plan for this development shows the original defined Basin 101 and the 2 I I proposed Basin I that is directed to the detention pond and the proposed Basin OS1 that ' flows offsite to the irrigation ditch, Harmony Road or Gifford Court. The original Third Filing report anticipated these flows to leave the site and this design follows the general intent of that report. A small area of the southwest corner of the site will flow to Gifford Court that was not anticipated with the original report but this runoff will have negligible impacts to the flow depth in Gifford Court. Gifford will convey these flows to the Idetention pond which will meet the general intent of the Third Filing drainage concept 3.4 Hydraulic Criteria No subsurface drainage conveyances are proposed with this development, therefore no hydraulic calculations were completed with this design. 4. DRAINAGE FACILITY DESIGN ' 4.1 General Concept ' The runoff from this site will be collected in concrete pans and be conveyed to an existing inlet on the east side of the site or flow in the parking lot and curbs. All runoff ' will be discharged into the pond in the southeastern portion of the Third Filing development. 1 No flows are anticipated to enter the site from adjacent properties. 1 4.2 Specific Flow Routing ' A summary of the drainage patterns within each basin is provided in the following paragraphs. ' Basin 1 encompasses the majority of the proposed development including the building, parking lots, sidewalks, private drives and drive through lane. A majority of the runoff flows in the parking lot to the south and is collected in an existing concrete pan which will convey the flows east to an existing inlet. This storm pipe will convey the flows to the existing detention pond. A small portion of the flows on the east side of the site will flow to an existing inlet and will be conveyed directly to the detention pond. 1 3 lJ I 1 Basins OS1 includes the north and west portions of the site which encompass the ' proposed patio, the 8' wide bike trail and the existing walk along Gifford. The runoff from this basin will either flow west directly into Gifford and be conveyed to the ' detention pond or north into the existing irrigation ditch or Harmony Road. This flow path was anticipated with the original overall Preston Center Third Filing report. 4.3 Drainage Summary All runoff from this site and the adjacent sites will be safely conveyed in storm piping or via surface flow to the detention pond. The site will conform to the overall drainage ' report for this subdivision and will maintain the drainage patterns that currently exist on site. The City of Fort Collins will be responsible for maintenance of the existing storm drainage facilities located within the right-of-way. The drainage facilities located outside of the right of way (including the detention ponds and inlets) will be maintained by the Preston Center Association. ' S. STORMWATER MANAGEMENT CONTROLS 5.1 Written Analysis The soils on this site are classified by the USGS Soil Survey as Fort Collins Loam and Nunn Clay Loam. The soils are classified in the hydrologic groups B and C. The rainfall and wind erodibility is deemed to be moderate on this site. 1 The site is surrounded by developed sites including streets and paved areas. The construction shall utilize silt fence around the perimeter to control sediment transport from rainfall and from wind. The silt fence that is located in the proposed pavement areas will be removed prior to placing new pavement. Rock socks will be utilized in the existing curb to capture sediments that are not fully contained by the silt fence placement. The locations of the rock socks will be in the areas of concentrated flow such as the existing curb, the proposed concrete channel and the existing inlet. Rock socks will be placed across the concrete trail on the north side of the site. 1 4 F I �J ' The site will also utilize a vehicle tracking control pad to minimize sediment from being ' tracked onto adjacent pavements. Sediment that is tracked will be removed and placed within the site or permanently disposed of off site. A concrete washout will be used on site during the concrete placement. All hardened concrete will be disposed of off site. Permanent erosion control consists of covering the soils with a building, concrete walks, ' asphalt pavement and sod. No soil will be left exposed to erosion after the construction is complete. Refer to the landscape plan for areas of and instructions for placement of sod and soil amendments prior to placement of sod. Refer to section 5.5 for the timing of the construction phases and the sequential installation of all BMP phasing for this site. I/Refer to the end of Section 5.4 for the Erosion Control Surety calculations. 5.2 SWMP contact information Permit holder: Name: ' Address: Phone Number: Email Address: Appointed agent: ' Name: Address: ' Phone Number: Email Address: I 1 5 I 1 5.3 Identification and location of all potential pollution sources L7 I I Potential Pollutant Source Activity . Potential Pollutant Generated Applicable to this project _ Disturbed Areas Sediment X Soil stockpiles Sediment X Travel to adjacent public streets Tracked sediment X Contaminated soils Sediment, chemicals Loading and unloading chemicals Chemicals Outdoor storage of chemicals Chemicals On site equipment maintenance Oil, grease On site equipment fueling Diesel, gasoline X Dust generating activities Particulates, sediment X Use of fertilizer, pesticides, herbicides Fertilizer, pesticides Use of detergents, solvents, oils Detergents, solvents, oil X Waste dumpsters, waste piles Chemicals X Concrete washout Concrete, sediment X On site equipment washing - Detergents, oil On site asphalt batch plant Asphaltic cement, sediment On site concrete batch plant Cement, sediment Portable toilets Domestic sewage X 5.4 Best Management Practices (BMP's) for Stormwater Pollution Prevention Structural Practices for Erosion and Sediment Control Structural practices for the site will consist mainly of silt fence and rock sock filters and are described in detail in the following paragraphs. These BMP's are expected to change as the construction progresses and it is the responsibility of the contractor to ensure appropriate BMP's ' are in place and/or removed at the appropriate time in the construction sequence. All temporary and permanent erosion and sediment control practices must be maintained and repaired as needed to assure continued performance of their intended function. Silt fence and rock sock filters shall be in place prior to commencement of construction activities. During clearing and grubbing necessary for silt fence installation, all cleared material shall be placed on the uphill side so that if erosion occurs from the cleared material, the sediment will be trapped and not transported downstream. Rock socks shall be implemented in the existing 6 L �n I I I' t I I curb line as shown on the Drainage & Erosion Control Plan. Inlet Protection shall be located around the existing curb inlet. All BMP's shall be installed per the details shown on the construction plan set. Temporary & Permanent Structural BMP's: Structural BMP - - - ,Approximate location on site - :.Applicable to this .- Project = Silt Fence Site perimeter, refer to site map X Straw bale dams Rock Socks At existing curb, refer to site map X Earthen diversion dams Vegetated swales Sediment trap/pond Pipe slope drains Geogrid Inlet/outlet protection Existing inlet, refer to site map X Culverts Riprap Erosion control mats Inlet protection At inlets, refer to site map X Non -Structural Practices for Erosion and Sediment Control: Soils exposed during the earthwork phase and landscape prep phase shall be kept in a roughened condition by ripping or disking along land contours until mulch, vegetation, or other permanent erosion control is installed. No large amount of soils (in excess of 15 yards) will be allowed to be stock piled on site. Overburden from the utility pipe trenching will be piled adjacent to trenches upstream of sediment controls and will be replaced in the trenches within 72 hours. Excess excavated materials from the demolition and grading phases of the project that cannot be reused on site will be exported as it is excavated. This includes any asphalt pavement from the existing site that is to be removed. A vehicle tracking pad will be installed at a location most beneficial to the site construction as determined by the contractor. Vehicles will not be permitted in the excavated area if soil is muddy. Gravel sub base will be placed and compacted in the areas indicated for pavement following excavation. In the current pre construction state the site enables tracking of silt onto the adjacent streets during wet conditions. During construction activities the street will be monitored for foreign debris tracked out of the site and mechanical sweeping and clean up will be performed as needed. I 1 1 i i E i 1 i 1 1 1 1 1 1 1 No area shall remain exposed by land disturbing activity for more than thirty (30) days before required temporary or permanent erosion control (e.g. seed/mulch, landscaping, etc.) is installed. Temporary & Permanent non-structural BMP's: Non -Structural BMP Approximate location on site Applicable to this Project Surface roughening Entire site X Soil stockpile height limit (less than 10') Perimeter vegetative buffer West boundary of site X Minimization of site disturbance Entire site X Mulch Seed & mulch stockpiles after 30 days Stockpile toe protection (silt fence, wattles or ditch) Preservation & protection of west boundary of site X existing vegetation & trees Good site housekeeping (routine Entire Site X cleanup of trash & constr debris) Heavy equip staged on site, properly maintained & inspected Staging area X daily (no onsite maintenance) L SEDIMENT/EROSION CONTROL BEST MANAGEMENT PRACTICES (BMPs) COST OPINION SPREADSHEET Preston Center Third Filing, Lot 7 Item BMP ID Unit Installation Unit Cost Maintenance as % of Installation Installation & Maintenance Unit Cost Quantity Cost 'No. 1 Check Dam CDR LF 25% $0.00 $0.00 2 Check Dam (Reinforced) CDR LF 25% $0.00 $0.00 Concrete Washout Area CWA EA $1,200.00 200% $3,600.00 1 $3,600.00 '3 4 Construction Fence CF LF 25% $0.00 $0.00 5 Construction Markers CM I LF 1 50% $0.00 1 $0.00 '6 7 Culvert Inlet Filter Dewatering CIF DW LF EA 25% 50% $0.00 $0.00 $0.00 $0.00 8 Diversion Ditch (Unlined) DID LF 25% $0.00 $0.00 9 Diversion Ditch (ECM or plastic) DID LF 10% $0.00 $0.00 '10 11 Sediment/Erosion Control Matting Inlet Protection ECM IF SY LF 25% 50% $0.00 $0.00 $0.00 $0.00 12 Reinforced Rock Berm RRB LF 25% $0.00 $0.00 Sediment Basin (1) SB LF 25% $0.00 $0.00 '13 14 Sediment Control Log (Wattle) SCL LF $4.60 25% $5.75 0 $0.00 15 Seeding and Mulching SM AC 50% $0.00 $0.00 '16 17 Silt Fence Rock Sock SF RS LF LF $3.00 $10.00 75% 10% $5.25 $11.00 1010 70 $5,302.50 $770.00 18 Stabilized Staging Area SSA SY 50% $0.00 $0.00 Surface Roughening SR AC 25% $0.00 $0.00 '19 20 21 Temporary Stream Crossing Topsoil (6-inch Lift) TSC TSL EA AC $2,500.00 1 25% 25% $0.00 $3,125.00 0.26 $0.00 1875.00 22 Vehicle TrackingControl12) VTC EA $1,500.00 100% $3,000.00 1 $3,000.00 Contractor Added BMP(s)13) 23 % $0.00 24 % $0.00 45 % $0.00 26 % $0.00 27 % $0.00 28 % $0.00 SUBTOTAL COST $13,547.50 CONTINGENCY 15% $2,032.13 TOTAL COST (4) $15,579,63 1 5.5 BMP Implementation ' I) Phased BMP Implementation ' BMP's are expected to change as the construction progresses and it is the responsibility of the contractor to ensure appropriate BMP's are in place and/or removed at the ' appropriate time in the construction sequence. All BMP's shall be inspected and repaired or replaced as required to satisfy the conditions of the Stormwater Discharge ' Permit. All BMP's must be maintained and repaired as needed to assure continued performance of their intended function. ' The following phase depictions and erosion controls are suggestions to the contractor only and are in no way intended to dictate construction phasing or control of the work on site. ' The contractor shall be responsible to control construction phasing and provide adequate erosion control associated with each phase in order to comply with the SWM Plan and Permit that is obtained by the contractor (or owner) for the site. ' Phase 1 — Mobilization Install silt fence, Install storm drain inlet protection at existing inlet, set dumpster. ' Phase 2 — Overlot Grading Cut and fill on site to achieve subgrade elevations Phase 3 - Utilities ' Excavate and install for water and sewer, excavate and install dry utilities Phase 4 — Exterior concrete Establish temporary concrete washout area, cut for curb and gutter and walks, place ' concrete curbs and walks Phase 5 — Site Paving Remove silt fence in pavement area, Install sub base, install, Asphalt pavement Phase 6 — Building construction Install concrete foundation, remove concrete washout. Complete building construction Phase 7 — Landscape installation ' Backfill curbs and final shape planting areas, Install irrigation system, Install soil amendments, Landscape plant installation, Install mulch ground cover Phase 8 — Final Stabilization Final stabilization is complete when constructed improvements are in place, Inspect completed construction for possible sources of erosion and amend the plan as required to ' trap sediments. 1 10 �l Materials Handlinu and Snill Prevention Materials Handling & Spilt Approximate location on site Applicable to this Prevention BMP Project Portable toilets, anchored & Refer to site map X located away from drainages Fuel storage located in bulk tanks with secondary containment & spill kit Mobile fueling performed at least 200 feet away from drainages & Refer to site map X fully attended Fertilizers, form oil, solvents, cleaners, detergent stored in 55 gal Refer to site map X or smaller containers, kept in storage units Dumpsters containing used chemicals containers & liquid Refer to site map X wastes kept covered Equipment cleaning (on site) uses no detergents & flows to onsite retention basin In case of a release of fuel or other chemicals, absorbent booms or earthen berms will be immediately Location of spill X constructed to contain the spill & prevent runoff to adjacent surface waters MSDS sheets for onsite chemicals will be kept at the construction Constmction Trailer X trailer to facilitate spill response & cleanup 3) Dedicated Asphalt or Concrete Batch Plant: Not proposed with this development. 4) Vehicle Tracking Pad: Vehicle tracking control pad shall be installed wherever construction vehicle access routes intersect paved public roads. Vehicle tracking control pads shall be installed to ' minimize the transport of sediment (mud) by runoff or vehicles tracking onto the paved ' surface. Any mud tracked to public roads shall be removed on a daily basis and after any significant storm that causes sediment to be transported. ' It is unlawful to track sediment/mud onto public streets and may be enforced by the City ' of Fort Collins or by the State of Colorado. 1 5) Waste Management and Disposal: ' Portable toilets will be anchored & periodically maintained by waste management company. Dumpsters on site will be covered & periodically emptied by waste ' management company. Concrete waste will be allowed to harden and then will be removed from site. ' No washing activities will occur on site. ' Location of the concrete washout is shown on the site map. The washout will be sufficiently deep to accommodate all anticipated concrete truck wash water. Waste concrete will be allowed to harden and be removed from site periodically as the washout reaches 50% of its capacity. Truck wash water will not be allowed to reach the curb & gutter or any other water course. ' 6) Groundwater and Stormwater Dewatering: ' No groundwater encountered during soils exploration therefore not anticipated to be an issue. ' If groundwater is encountered a groundwater discharge permit shall be obtained and a detailed report shall be completed describing the location and the route of where ' pumped groundwater will be conveyed and the measures taken to prevent the transport 1 12 I ' of any pollutants to downstream waters. ' 7) Inspection & Maintenance: It is required that routine site inspections are performed to effectively address maintenance and ' repair of Best Management Practices (BMP's). The site inspections are to performed by the contractor or an inspector designated by the administrator at a minimum of once every fourteen (14) calendar days on active construction sites and after any significant storm event (an event ' causing runoff). As part of the site inspections the inspector is required to keep documentation of all inspections and BMP maintenance, including an updated Site Map indicating new BMP's or the removal of BMP's since the previous inspection. ' Any maintenance, repair, or necessary installation of BMP's that are noted during the inspection ' must be completed within seven (7) calendar days from the date of the inspection. ' 6. CONCLUSIONS ' 6.1 Compliance with Standards All computations that have been completed within this report are in compliance with the ' City of Fort Collins Storm Drainage Design Criteria Manual and the Final Drainage and Erosion Control Study for Preston Center Third Filing. ' 6.2 Drainage Concept ' The proposed drainage concepts presented in this report and on the construction plans adequately provide for conveyance of runoff to the detention areas. Conveyance ' elements have been designed to pass required flows and to minimize future maintenance. ' If, at the time of construction, groundwater is encountered, a Colorado Department of Health Construction Dewatering Permit would be required. 1 1 13 7. REFERENCES 1. City of Fort Collins, "Storm Drainage Criteria Manual", (SDCM), dated March, 1986. 2. Urban Drainage and Flood Control District, "Urban Storm Drainage Criteria Manual", Volumes 1 and 2, dated March, 1969, and Volume 3 dated September, 1992. 3. McClellands Creek Master Drainage Plan Update by ICON Engineering, Inc. dated November 30, 2000. 4. "Final Drainage & Erosion Control Report for Preston Center Third Filing" by JR Engineering dated July 12, 2000. 14 I 1 1 APPENDIX A 1 VICINITY MAP i 1 1 [1 i i i 1 1 1 i 1 1 1 I i EROSION CONiPIX NOTES'. 1) line City Stormwoler Department a control inspector must be notified at least 24 hours prior to any construction on this site. 2) All required BMPS shall be lnstallea prior fo any land disturbing activity Dart (9tOtkpiling, slripp:n0, grading, etc). All O( required dr09 Contra l measures must o do GO be installed al tFe ppropriate time in the construction sequence a indicated in the approved project %chetivle, construction plans, and erosion control repwL p o ' as �NO NO 3) Pre -disturbance vegetation shall be protected and retained wherever possible. p p Cy R m vat ar distvrbOnc of existing vegetation shall be Ilmited to the area required �._ - p do m tar immetliote con5lruclion operations. and for the smartest practical period of time. C o 0 m O 4) All soils evposed during land disturbing activity (stripping, grading. utility rr^�^' OI Q . y pl 20 10 0 20 40 installations, stockpiling, fining, etc.) shall be kept in a roughened Con6tion by vJ N o X EAST HARMONY ROAD ripping or risking alonlam contours Emil mulch. vegetation, or other perm ent W \�\— — e - t linstalled. N 1 outside project street rights or way '�-O 3 B_ILL .-. SCPLE: 1' 20a/ WCF 's _\\\\ 5M1 I p d by d disturbing activity f than thirty (JO) days Y _ _ otherwise t Ito before tl required temporary� a ten a permanent o a (by9 q he Starri landscaping. PP O __-__ 4- s) Theproperty t in t o d " f d l II t' during construct on < hall ba _ activities immediately discontinued tp d tM1 al g} dustimpacts All adjacent disturbing pin'pg t l 1 5 1� `- - as determined by the City Engineering Department, - PS 6) All temporary reconstructedy(t t I) t t in -inspected d w repaired r ft h ff t and every 14 days in a and Pr to assuretrued performance of their intendedfunction, All retuned sediments. p t mm rly those on pored aaw^y°s surfaces, shall b removed and ra OT I x WRWc 0.W5Ru0T disposed a f' a anner and location soas t t9 their a into an 9 Y y d m 1 I )) No soil stockpile shall exceed ten (10) feet in height All Soil stakiias shall b¢ 0 1 / protected r m sediment transport by surface roughening t g and perimeter Slit It r g. A y S l t Hpl 9 1t 30 d o Sanll be seeded and mulched. D ss o.zT 8) City Ordinance prohibits y tracking, g tl pp a depositingert sots any other B�,, material be t -t streets b the M1 An 'nadvertenl deposited tei al n ; G.z �='-"a'�° L� "':n'y � sFan be cleaned ymmed a � °f cono-aaror. �'w . let nr the z o �GY I = ' ••• A y'x 0.WSThUGnCN ICU.. R E. ower LEGFIO _ ___EMSi NG PIPES -.Sol -- -- ECEIC a CONTWe 101 � - ExNsnrvG cCONTOURz z.z6 0. 4905 PPMOYO 5 CONTOUR xl p Y Y 4 IA t � 11 PROPOSED I CONiWR � II a 0 T Z3 OESGN p°tit r PNASE t 9ET pangs B.O 1. BE Ix a y fP—d'/IIY R R - ! Mli OVRNG OfxWTgl k BASIN GiERA N OLEmnT GRIDm6 PFLovE PMCR O.z6 0.9 m RvxDEF cWmclErvT _ o 10 SUBBASE NSTA1lATW N -N o AREA ACRES In or In ncy, 4w Pa ties m wo SB EASE DdOs W N t I BASIN BWNOAPi m 3 'lit O_ BlEx CLE — SALT FENCE 'Al O O�LNKgO SlE{S' /t n 313W mi m` O t^ __ __ _ __ __ ____ _ ___ __ 6 0: 0� - � i F SF CONCRETE wASNWi AREAStu "a Q•? �I :: EYISTNG NIET SE➢NENi CONTROL LOG<x"`r rv1Ei PPOIECnON •- 1 RS =� D«m z z ICA D1Snlp OF PANIIwT e Si Z 4WptElE PAN $FPS $ $TE—C ____J ..r. O $ems $F� Svc-------- p'- - 'ZH o — On: z �F—e `W Few o PS _ __ - l PS g,°i V!r O O Pay_ WZJ -a CCW W _' hat. NI _ Z W aCTjI O �' Few z P W City of Fort Collins, Colorado ku; UTILITY PLAN APPROVAL a D APPROVED'. [lv En9nw D°te SHEET 'T CHECKED BY: t.,y D°,. CALL Onl1OF COLORAD ON m„� �T w°'^ ° w°"°"°'. u J_ CENTER OF C0.ORADOy CHECKED BT: Dote 1.800_-922.1987 (811) elmmwtm Ba lY WORD you OIG rNAOE ON E CAVAft EASSNESS DAYS IN AMANNIGIC CHECKED BT: pO n FOR ME MA IxG OF UNDERMWUO ha k Rene°te 0°le NEN� minus. CHECKED BY: S OF B ' raft° En9 nea D°b CHECKED By Job No. 345-01 I 1 1 1 1 Li 1 1 APPENDIX B HYDROLOGIC COMPUTATIONS u M 0 W a N H Z W U LL LL W O U LL LL 0 Z 7 Of w o Z o O o O E 21 LL O LL 8 N r O 00 o 0 U O W 7 r m U O O z Q O m U LL LL LL LL W U N j O o 0 m U LL LL LL O U O m n e o 0 � U O e e d N O E w a N U W z M p m 0 < 2 Q J J W Q � W � ¢ m U W w K W M U m v m Z Q 0 U ¢ w r n m = a o m a LL O w Y O O n N K Q m Q F w K y N N n O 0 J _ f w U O Q N O N N F z m O N o m - o m 0 U I 1 1 CI 1 t 1 I I 1 APPENDIX C EXCERPTS FROM PREVIOUS REPORTS 14 I I FINAL DRAINAGE & EROSION CONTROLSTUDY PRESTON CENTER AT WILD WOOD BUSINESS PARK THIRD FILING Prepared for: Western Property Advisors, Inc. Stanford Plaza, Suite 100 3555 Stanford Road Fort Collins, Colorado 80521 Prepared by: JR ENGINEERING 2620 E. Prospect Rd., Suite. 190 Fort Collins, Colorado 80525 (970)491-9888 July 2, 1998 Revised April 11,2000 Revised January 17, 2000 June 12, 2000 Job Number 9177.07 this unofficial copy was downloaded on Apr-29-2013 from the City of Fort Collins Public Records Website: http://cilydocs.fcgov.com Runoff from Subbasin 101 is conveyed via sheet flow and gutter flow to a double Type 16 combination inlet at Design Point 1. The flows are then conveyed to the detention pond via pipe flow. Runoff from Subbasin 102 is conveyed via sheet and gutter flow to a 5' Type `R' inlet at Design Point 2. From there it joins the flows from Sub -basin 101 and is conveyed to the detention pond via pipe flow. Subbasin 103 includes the parking lot in the northeast portion of the site. The runoff from this subbasin is conveyed via sheet and gutter flow to a 5' Type `R' inlet at Design Point 3. This runoff joins runoff from subbasins 101 and 102 to be diverted to the detention pond. Runoff from Subbasin 104 is conveyed via sheet and gutter flow to a 5' curb cut and sidewalk chase at Design Point 4 that directly discharges into the detention pond. Subbasin 105 includes parking areas, parts of buildings, and landscaped areas. Runoff from this area is conveyed via sheet and gutter flow to a 4' curb cut and sidewalk chase that leads to the detention pond. Runoff from Subbasin 106 is conveyed via sheet and gutter flow to a 10' Type "R" inlet at Design Point 6 and piped to the detention pond. Subbasin 107 contains the eastern half of Gifford Court. Runoff from this Subbasin is conveyed via sheet and gutter flow to an existing 4' Type 'R' inlet at design point 7. This flow is carried in a storm pipe to the detention area. Subbasin 108 includes the southern half of the hotel and the landscaped area south of it. This runoff is conveyed via overland and swale flow to a Type 'C' inlet at Design Point 8, where it joins flows from Subbasins 106 and 107 to be carried to the detention pond. Runoff from Subbasin 109 is conveyed via sheet and gutter flow across the parking lot to a 4' curb opening at Design Point 9 that leads to the detention pond. his unofficial copy was downloaded on Apr-29-2013 from the City of Pot Collins Public Records Website: littp://citydocs.fcgov.com ..,_ i.:___.. _i____ -------r_u: Subbasin I10 contains the detention pond and the area that overland flows into the detention pond. Subbasin 111 contains the north area of the site. This area includes the existing irrigation ditch. Runoff from this subbasin is conveyed via overland flow and swale flow to the existing irrigation ditch. The sub -basins imperviousness has only slightly changed by the addition of sidewalks. These sidewalks will have minimal effect on the drainage patterns and flows. From this information the assumption that the area is very close to historic and undeveloped and therefore the basin was not included in any release calculations. Subbasin 112 contains the area that drains directly to Timberwood Drive. Runoff from this area is conveyed via sheet flow and gutter flow to an existing inlet at Design Point 12. This basin and its flows and drainage structure were designed with the Timberwood Drive plans and have not been altered. Subbasin 113 contains the historic farm site and cannot, for historic reasons, be regraded:. The existing grading directs the runoff from this subbasin to County Road 9 and because of the historic significance of this site, this condition will continue. 3.5 Hydrologic Analysis of the Proposed Drainage Conditions The Rational Method was used to determine both 10-year and 100-year peak runoff values for each Subbasin. The Rational Method utilizes the SDDCCS equation: Q = CICIA (1) where Q is the flow in cubic feet per second (cfs), A is the total area of the basin in acres, Cr is the storm frequency adjustment factor, C is the runoff coefficient, and I is the rainfall intensity in inches per hour. The frequency adjustment factor (Cl) is 1.0 for the initial 10-year storm and 1.25 for the major 100-year stone. The appropriate rainfall intensity information was developed based on rainfall intensity duration curves in the SDDCCS Manual. his unofficial copy was downloaded on Apr-29-2013 from the City of Fort Collins Public Records Website: httpl/citydocs.(cgov.com In order to utilize the rainfall intensity curves, the time of concentration is required. The following equation was used to determine the time of concentration. t.=t,+t, (2) where it, is the time of concentration in minutes, t, is the initial or overland flow time in minutes, and t, is the travel time in the channel, pipe, or gutter in minutes. The initial or overland flow time is calculated with the equation: t, = [1.87(1.1 - CQLo.el/(S)o.3a (3) where L is the length of overland flow in feet (limited to a maximum of 500 feet), S is the average slope of the basin in percent, and C and Cr are as defined previously. All hydrologic calculations associated with the subbasins are attached in Appendix B of this report. Table 3.1 provides a summary of design flows. WE MMARY TABL Design Tributary Area C 110) C (100) tc (10) tc (100) Q(10)tot Q(100)tot Sub -basin Point I I Jac) (min) (min) (cfs) (cfs) 3 103 0.74 0.65 0.81 5.0 5.0 2.3 4 104 1.16 0.80 0.99 5.0 5.0 4.4 gO 5 105 1.14 0.68 0.85 5.0 5.0 3.8 6 105 1.02 0.69 0.86 5.0 5.0 3.4 7 107 0.53 0.63 0.78 8.0 6.3 1.4 3.8 8 108 0.48 0.47 0.59 11.2 9.9 0.8 2.2 9 109 1.40 1 0.61 0.76 1 12.3 11.3 1 3.0 7.9 110 1.43 0.18 0.22 12.2 12.2 0.9 2.3 111 1.56 0.20 0.25 14.6 14.6 1.0 2.6 12 112 1.14 0.65 0.81 5.1 5.1 3.5 9.0 113 0.73 0.29 0.36 9.6 9.2 0.8 2.1 10 Total to Pond 10.45 0.63 0.79 15.1 13.4 20.9 56.2 1Z unofficial copy was downloaded on Apr-29-2013 from the City of Pon Collins Public Records Website: littp:Hcitydoes.fcgov.com ad:.:,....e:..r,,........,,_,._.... ,,ir...:..i ..,....._i.------...1;-a1c--1„11:....n.a:a...vnn11--'e....... c-- 1..n:_.. 11 oncnn nen