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Drainage Reports - 11/29/2017 (3)
' November 13, 2017 City of Ft. Collins rov Plans Approved By lz ---i tDate 1/ -st q - .201 ? C 1 I 1 ' Prepared for: Laura Olive 125 S. Howes Street, Suite 120 ' Fort Collins, CO 80525 Prepared by: NORTHERN ENGINEERING ' 301 North Howes Street, Suite 100 Fort Collins, Colorado 80521 Phone: 970,221.4158 Fax: 970.221.4159 www. northernengineeri ng.com t This Drainage Report is consciously provided as a PDF. Please consider the environment before printing this document in its entirety. ' When a hard copy is absolutely necessary, we recommend double -sided printing. Project Number: 1076-001 — Nnrr{r PrnFnnln P,xrinn.rnrn // 970271.61 SA i I W NORTHERN ENGINEERING November 13, 2017 City of Fort Collins Stormwater Utility ' 700 Wood Street Fort Collins, Colorado 80521 IRE: Final Drainage Report for West Village Off Taft LJ [1 1 Dear Staff: Northern Engineering is pleased to submit this Final Drainage Report for your review. This report accompanies the Conceptual Review submittal for the proposed West Village Off, Taft. This report has been prepared in accordance with the City of Fort Collins Stormwater Criteria Manual (FCSCM) and the Urban Drainage and Flood Control District (UDFCD) Urban Storm Drainage Criteria Manual and serves to document the stormwater impacts associated with the proposed West Village Off Taft project. We understand that review by the City of Fort Collins is to assure general compliance with standardized criteria. If you should have any questions as you review this report, please feel free to contact us. Sincerely, GINEERING SERVICES, INC. ;: tia•. spa. Eo 5 91 :J moo`:, t1.t�,►'� ?'�� 0:0 Cody Snowdon, PE Project Manager Blaine Mathisen, El Project Engineer 301 N. Howes Street, Suite 100, Fort Collins, CO 80521 I 970.221.4158 I www.northernengineering.com ■� NORTHERN ENGINEERING I I I I Il H I 1 1 TABLE OF CONTENTS I. General Location and Description............................................................................... 1 A. Location.............................................................................................................................................1 B. Description of Property .....................................................................................................................1 C. Floodplain..........................................................................................................................................2 II. Drainage Basins and Sub-basins.................................................................................. 3 A. Major Basin Description....................................................................................................................3 B. Sub -Basin Description.......................................................................................................................3 III. Drainage Design Criteria............................................................................................4 A. Regulations........................................................................................................................................4 B. Four Step Process..............................................................................................................................4 C. Development Criteria Reference and Constraints............................................................................5 D. Hydrological Criteria ..................................................... :................................................................... 5 E. Hydraulic Criteria..............................................................................................................................6 F. Floodplain Regulations Compliance..................................................................................................6 G. Modifications of Criteria...................................................................................................................6 IV. Drainage Facility Design............................................................................................ 6 A. General Concept...............................................................................................................................6 B. Specific Details ................................ .................................................................................................. 7 V. Conclusions.............................................................................................................9 A. Compliance with Standards..............................................................................................................9 B. Drainage Concept..............................................................................................................................9 References....................................................................................................................... 10 APPENDICES: APPENDIX A —. Hydrologic Computations APPENDIX B — Hydraulic Computations B.1 — Detention Facilities B.2 — Inlet and Weirs APPENDIX C — Water Quality Design Computations APPENDIX D — Erosion Control Report LIST OF TABLES AND FIGURES: Figure 1 - Aerial Photograph - Google Earth............................................................................ 1 Figure 2 - Proposed Site Plan............................................................................................... 2 Figure3 - Existing City Floodplain.......................................................................................... 3 Table1 - LID Table............................................................................................................4 Final Drainage Report W INORTHERN ENGINEERING W11 MAP POCKET: C7.00 - Drainage Exhibit C7.01 — Historic Drainage Exhibit Final Drainage Report ' NORTHERN ENGINEERING IN 1 11 11 1 I GENERAL LOCATION AND DESCRIPTION A. Location 1. Vicinity Map Figure 1 - Aerial Photograph - Google Earth 2. West Village Off Taft is in Township 7 North, Range 69 West of the 61h p.M., City of Fort Collins, County of Larimer, State of Colorado. 3. The project site is located on the east side of S. Taft Hill Rd. near the intersection of S. Taft Hill Rd. and Sheffield Dr. It is directly across the street from Blevins Middle School. The project site is surrounded by residential homes to the north, east, and south. 4. Currently the existing lot remains mostly undeveloped. However, there is currently a two-story house with an associated detached garage and landscaping. This house has been deemed historical and therefore cannot be demolished but instead must be incorporated into the over plan for the proposed subdivision. The house sits along the western property line adjacent to the pedestrian cross walk across S. Taft Hill. B. Description of Property 1. West Village Off Taft project site is 2.35 net acres. West Village Off Taft is not proposing any improvements to S. Taft Hill Rd. However, due the lack of storm sewer infrastructure the proposed project will be discharging east into Dover Dr. through a sidewalk chase therefore additional offsite improvements will be necessary near the south-east corner of the project site. Also, West Village Off Taft will leave the historical house untouched other than two landscaping walls that jutted to far south into the private drive aisle. Overall, the proposed site will maintain the historic drainage Final Drainage Report I ' W� NORTHERN ENGINEERING West Village Off Taft patterns. ' 2. West Village Off Taft will be maintaining the overall historic drainage characteristics of this site. There are currently no water quality amenities or any existing storm infrastructure on site. West Village Off Taft is proposing to install a Filterra System as ' well as several retaining walls to help meet required detention and water quality volumes, this will be discussed in Section IV.B. There is no offsite runoff entering the site from S. Taft Hill Rd. ' 3. Per the United States Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS) Soil Survey, 100 percent of the site consists of Altvan- Satanta loams, which fall into Hydrologic Soil Groups B. ' 4. The proposed development will include the clearing of existing vegetation, twelve (12) tress, the removal of 180 sf. of sidewalk where the proposed entrance is and the removal of roughly 135 sf. of concrete walls behind the existing detached garage. ' West Village Off Taft will be developing seven (7) single-family lots, two separate detention facilities, and a private drive aisle to serve all the lots, associated drainageways, and detention facilities. 1 1 [1 C Figure 2 - Proposed Site Plan 5. There are no irrigation facilities, erosion buffer zones, or major drainage ways within the property limits. 6. The project site is within a Low Density Residential zoning district. Therefore, the proposed use is permitted within this zone district. C. Floodplain 1. The subject property does not lie within a FEMA floodplain. The project site falls within the FIRM Panel 08069C986G for Larimer County, dated May 2nd, 2012. 2. West Village Off Taft does not fall within a city floodplain. Final Drainage Report 2 NORTHERN ENGINEERING Off Taft ' N%S prti 4•,, PFtoj T SITF hW.>•,v Mapb N6* 361 oh it h Figure 3 - Existing City Floodplain II. DRAINAGE BASINS AND SUB -BASINS A. Major Basin Description 1. West Village Off Taft is within the Canal Importation drainage basin. This basin, which suffered significant property damage in the flood of 1997, is almost completely urbanized with primarily mixed density residential and isolated commercial land uses. Runoff from the basin empties into the Old Town or Spring creek basins. 2. There are no previous drainage studies for the area associated with this project site. B. Sub -Basin Description 1. West Village Off Taft historically sheet flows from the northwest towards the southeast corner of the project site. The overall historic condition will be maintained. Basin H1 Basin H 1 is associated with the entire project site and has an overall area of 2.35 acres. Basin H 1 has one two story house with a detached garage and an associated gravel driveway. There is currently no stormwater infrastructure or water quality facilities. Additionally, there are no offsite flows entering Basin H1. Basin H1 has a historic 2-year flow of 1.26 cfs. 2. A more detailed description of the projects proposed drainage patterns follows in Section IV.A.4., below. Final Drainage Report 3 ' NORTHERN ENGINEERING West Village Ofi ' 3. There are no offsite flows associated with West Village Off Taft. ' 4. A full-size copy of the Historic and Proposed Drainage Exhibit can be found in the Map Pocket at the end of this report. ' III. DRAINAGE DESIGN CRITERIA I 1 11 A. Regulations There are no optional provisions outside of the FCSCM proposed with the West Village Off Taft project. B. Four Step Process The overall stormwater management strategy employed with the West Village Off Taft project utilizes the "Four Step Process" to minimize adverse impacts of urbanization on receiving waters. The following is a description of how the proposed development has incorporated each step. Step 1 — Employ Runoff Reduction Practices Several techniques have been utilized with the proposed development to facilitate the reduction of runoff peaks, volumes, and pollutant loads as the site is developed from the current use by implementing multiple Low -Impact Development (LID) strategies including: Providing as much vegetated open areas as possible along the north, east, west and south portion of the site to reduce the overall impervious area and to minimize directly connected impervious areas (MDCIA). Routing flows, to the extent feasible, through either the grass swale or into the Filterra System. Providing on -site detention to increase time of concentration, promote infiltration and reduce loads on downstream storm infrastructure. Below is a table that shows the breakdown of the proposed LID amenities compared to the proposed impervious area. Design Point al bl Percent of LID Impervious Area BasinlD Basin Area Treatment Type Impervious Area System Treated by LID System Extended Al 1.168 ac. No 0.213 ac. 0.00% Detention Ell 1.185ac. Filterra Yes 0.598ac. 73.74% Total 2.353 ac. 0.811 ac. 74% Table 1 - LID Table Step 2 — Implement BMPs That Provide a Water Quality Capture Volume (WQCV) with Slow Release The efforts taken in Step 1 will facilitate the reduction of runoff and provide the necessary BMPs required for water quality. Stormwater generated along the northern portion of the project site will sheet flow north where it will be collected and routed through a grass lined Final Drainage Report 4 ' NORTHERN ENGINEERING West Village Off Taft ' swale. Runoff generated near the middle of the project site will sheet flow south across the private drive aisle where it will enter the Filterra System. Eventually all the runoff is routed ' to one of the two ponds that border the southern property line. Stormwater will be released into Dover Drive at the historic 2-year runoff. ' Step 3 — Stabilize Drainageways As stated in Section 1.B.5, above, there are no major drainageways in or near the subject site. While this step may not seem applicable to West Village Off Taft, the proposed ' project indirectly helps achieve stabilized drainageways nonetheless. Once again, site selection has a positive effect on stream stabilization. By repurposing an under-utilized site with no existing stormwater infrastructure, combined with LID, the likelihood of bed and ' bank erosion is greatly reduced. Furthermore, this project will pay one-time stormwater development fees, as well as ongoing monthly stormwater utility fees, both of which help achieve Citywide drainageway stability. 1 Step 4 — Implement Site Specific and Other Source Control BMPs. This step typically applies to industrial and commercial developments and is not applicable for this project. C. Development Criteria Reference and Constraints 1. There are no known drainage studies for the existing property. 2. The subject property is essentially an "in -fill' development project as the property is surrounded by currently developed properties. As such, several constraints have been identified during this analysis that will impact the proposed drainage system including: K Existing elevations along the east, west, north, and south property lines will be maintained. K During the construction of West Village Off Taft, it is imperative that the house that currently sites on the project site remains untouched except for the two concrete walls behind the detached garage that will need to be removed. wa Overall drainage patterns of the existing site will be maintained. K The shallow curb and gutter on Dover Drive is the ultimate discharge location for West Village Off Taft. D. Hydrological Criteria 1. The City of Fort Collins Rainfall Intensity -Duration -Frequency Curves, as depicted in Figure RA-16 of the FCSCM, serve as the source for all hydrologic computations associated with this development. Tabulated data contained in Table RA-7 has been utilized for Rational Method runoff calculations. 2. The Rational Method has been employed to compute stormwater runoff utilizing coefficients contained in Tables RO-11 and RO-12 of the FCSCM. 3. The Rational Formula -based Modified Federal Aviation Administration (FAA) procedure has been utilized for detention storage calculations. 4. Two separate design storms have been utilized to address distinct drainage scenarios. The first event analyzed is the "Minor," or "Initial' Storm, which has a 2-year recurrence interval. The second event considered is the "Major Storm," which has a 100-year recurrence interval. 5. No other assumptions or calculation methods have been used with this development Final Drainage Report E NORTHERN ENGINEERING West Village Off Ta- ' that are not referenced by current City of Fort Collins criteria. ' E. Hydraulic Criteria 1. As previously noted, the subject property historically drains from the northwest to the southeast. The entire site drains stormwater via overland flow. 2. All drainage facilities proposed with the West Village Off Taft project are designed in accordance with criteria outlined in the FCSCM and/or the Urban Drainage and Flood ' Control District's (UDFCD) Urban Storm Drainage Criteria Manual. 3. As stated in Section I.C.1, above, the subject property is not located within a City regulatory floodplain. 4. West Village Off Taft does not propose to modify any natural drainageways. F. Floodplain Regulations Compliance 1. As previously mentioned, the project site does not fall within a FEMA or City regulatory floodplain. ' G. Modifications of Criteria The proposed West Village Off Taft development is requesting that the required amount of freeboard be reduced from one (1) foot to six and a half (6.5) inches. Due to the shallow outfall elevation (Dover flow line), extremely flat site, and elevation constraints on the Northern, Southern, and Eastern Boundaries. Pond A has a freeboard height of 6.72" and Pond B has a freeboard height of 8.16". A weir has been designed to adequately convey 130% of the 100-year event at the high-water surface elevation but still 6" inches below the freeboard. IV. DRAINAGE FACILITY DESIGN ' A. General Concept 1. The main objectives of the West Village Off Taft drainage design is to maintain ' existing drainage patterns and ensure no adverse impacts to any adjacent properties or existing infrastructure occurs. C 2. As previously mentioned, there are no off -site flows draining onto the project property. 3. A list of tables and figures used within this report can be found in the Table of Contents at the front of the document. The tables and figures are located within the sections to which the content best applies. 4. West Village Off Taft has been divided into two (2) major drainage basins, designated as Basins Al, and B1. Basin Al Basin Al is located along the northern and eastern edges of the project site. Runoff from Basin Al is generated from assumed roofs, back porches, and landscaping. With these lots not being fully designed, it was assumed that each lot would allow for 1,310 sf roof (66.66% draining to the rear yard). Basin Al sheet flows south to north where it is collected in a grass lined swale. The swale conveys the collected runoff into Pond A which is situated at the southeast corner of the project site. From there the runoff will be released east by a swale at a restricted rate into Dover Drive. Final Drainage Report 6 NORTHERN ENGINEERING West Village Off Taft Basin B1 Basin B1 is in the middle of the project site and drains stormwater via overland flow from the north to the south. Runoff from Basin B1 is generated from roofs, driveways, sidewalk, landscaping, and the drive aisle. With these lots not being fully designed, it was assumed that 33.33% (655 sf) of the roofs drained towards the front, and each house was assumed to have a 20'x2O' concrete driveway, and a 10'x20' concrete porch. All the runoff generated in Basin B1 sheet flows across the private drive aisle and is collected in curb and gutter where it is then conveyed to the Filterra System for water quality treatment. Once, the runoff has been treated by the Filterra System it will discharge out the back of the boxes and enter Pond B for detention. Pond B releases into Pond A at a reduced release rate of 1.00 cfs. Once the runoff has entered Pond A it will then be free released east into a swale and concrete chase into Dover Drive at the historic 2-year rate. B. Specific Details 1. The main drainage problems associated with this project site is the deficiency of existing stormwater infrastructure present. Basins Al, and B1 will all be treated either by an LID amenity or via extended detention. �r A restrictor plate will be placed at the outfall of Pond A to ensure that the site is not discharging at a rate greater than the historic 2-year of the entire project. K Pond B will also have a 100-year restrictor plate on the outfall structure and an emergency spillway set at the 100-year water surface elevation, which will help route excess flows east into Pond A, and eventually to the ultimate outfall location in Dover Drive. Pond A and Pond B were both sized using a reduced historic 2-year release rate. Ultimately though, Pond A will be releasing the entire site at the historic 2-year release rate. 2. The release rate for the undeveloped land (pre -development) was established by calculating the Historic 2-year peak runoff rate for the entire project area (Basin H1) with no reduction because all the runoff generated on the site is being captured and treated. The overall historic 2-year peak runoff rate was calculated to be 1.26 cfs. This release rate was utilized in the FAA procedure detention storage computations (Refer to Appendix B for these calculations). 3. Detention Pond Calculations West Village Off Taft has two ponds that are right next to one another but act hydraulically independent of each other. Pond B is situated directly west of Pond A and they are separated by a berm and headwall that has a weir and restrictor plate on it. However, Pond A will have all runoff from the site eventually passing through it because it is the ultimate discharge location. Pond A will discharge east into a proposed swale and concrete chase into Dover Drive at the historic 2-year rate (1.26 cfs). Pond B will be releasing into Pond A at 1.00 cfs which will be bypassing Pond A because Pond A was sized using a release rate of 0.26 cfs. Pond A The FAA method was used to size Pond A. The overall historic 2-year release rate is Final Drainage Report 7 NORTHERN ENGINEERING 1 1 11 I 1 1 I t I 1.26 cfs and Pond A was sized using a release rate of 0.26 cfs and Pond B was sized using a release rate of 1.00 cfs. Based on the characteristics of Basins Al and an adjusted release rate of 0.26 cfs, formulate a detention volume of 6220 cu. ft. However, Basin Al is receiving water quality in the form of extended detention and following UDFCD standards Basin Al requires 415.77 cu. ft. of volume for water quality. Therefore, the required volume for the 100-yr detention plus the WQCV is 6636 cu ft. The top of pond for Pond A is at an elevation of 5084.05' and the top of freeboard is at 5084.61' therefore there is slightly less than 7 inches of free board (6.72"). A designed overflow weir has been designed to convey, any runoff that overtops this spill elevation, towards a designed swale. Pond A will be releasing at the full 2-year historic rate (1.26 cfs) and the emergency overflow weir, as described above, for Pond A is at the southeast corner of the site and discharges east into the swale that will convey the flows into Dover Drive. Pond B The FAA method was used to size Pond B as well. As mentioned in the description of Pond A, Pond B was sized using a release rate of 1.00 cfs. The reason different flow rates were used in sizing the two ponds was because Pond B is in a spot within the project site that allows for a larger pond. Based on characteristics from Basin B1 with an adjusted release rate of 1.00 cfs, formulate a detention volume of 7854 cu. ft. Basin B1 is receiving its water quality through the Filterra Systems. Therefore, the required volume for Pond B is only for the 100-yr detention. The top of Pond B is at an elevation of 5084.99' and the top of the emergency weir is at 5085.65 therefore there is 8.14" of freeboard. Pond B will release at a rate of 1.00 cfs into Pond A through a 12" HDPE pipe that connects the two ponds. Once into Pond A it will release at the historic 2-year rate of 1.26 cfs with Pond A's runoff. The emergency spillway, as described above, for Pond B is located at the headwall that divides Pond A and Pond B. The excess runoff will flow east until it reaches the swale east of Pond A where it will be conveyed to Dover Drive. 4. Water Quality Results Basin Al Water quality for Basin Al will be provided partially by a grass lined swale, but fully by extended detention in Pond A. Following UDFCD Standards, a required WQCV for Basin Al is 415.77 cu. ft. This volume is included within Pond A. Pond A will have an outlet structure located at design point al that detains and attenuates runoff and promotes the settlement of pollutants. Basin B1 Basin B1 will have water quality provided via Filterra Systems located at a low point within the private drive aisle in the middle of the private drive aisle. The Filterra Stystems were designed by a Contech Stormwater Engineer. Northern Engineering provided the flows entering the system and Contech designed the rest. 5. The emergency overflow weir for Pond B conveys (130% of the WO -year developed flow rate) excess runoff east over the berm/headwall into Pond A. The emergency overflow path is located at design point al. From there all excess flow will overtop the pond wall and flow east via swale into Dover Drive. 1 Final Drainage Report 8 NORTHERN ENGINEERING West Village Off Taft 1 V. CONCLUSIONS A. Compliance with Standards 1. The drainage design proposed with the West Village Off Taft project complies with the ' City of Fort Collins' Stormwater Criteria Manual. 2. The drainage design proposed with the West Village Off Taft project complies with the City of Fort Collins' Master Drainage Plan. ' 3. There are no city regulatory floodplains and/or erosion buffer zones associated with the West Village Off Taft project. 4. The drainage plan and stormwater management measures proposed with the West Village Off Taft development are compliant with all applicable State and Federal regulations governing stormwater discharge. B. Drainage Concept 1. The drainage design proposed with this project will effectively limit potential damage associated with its stormwater runoff. West Village Off Taft will detain and treat the entire project site and release at the historic 2-year rate east into Dover Drive during the developed 100-year storm. ' 2. West Village Off Taft will provide water quality via an LID feature, as well as extended detention. 1 1 Final Drainage Report 9 11 NORTHERN ENGINEERING References 1. City of Fort Collins Landscape Design Guidelines for Stormwater and Detention Facilities, November 5, 2009, BHA Design, Inc. with City of Fort Collins Utility Services. 2. Fort Collins Stormwater Criteria Manual, City of Fort Collins, Colorado, as adopted by Ordinance No. 174, 2011, and referenced in Section 26-500 (c) of the City of Fort Collins Municipal Code. 3. Larimer County Urban Area Street Standards, Adopted January 2, 2001, Repealed and Reenacted, Effective October 1, 2002, Repealed and Reenacted, Effective April 1, 2007. 4. Soils Resource Report for Larimer County Area, Colorado, Natural Resources Conservation Service, United States Department of Agriculture. 5. Urban Storm Drainage Criteria Manual, Volumes 1-3, Urban Drainage and Flood Control District, Wright -McLaughlin Engineers, Denver, Colorado, Revised April 2008. u l Final Drainage Report 10 NORTHERN APPENDIX A Y FY r i • :� p :: Zi CL Y O y A _ �ylY � I �to 0 DO / I / I I I I I I I @ I �\ 16 �\ I k0EE,��n� ¢ { �= iv �- Di 9—L) Q § §� OD m ¥:! 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W N, A g o .. 0 V w A p0, I� W Cn � o I a m m m z z0 z � Mm m ;OM -m m Z I I 1 I 1 I 1 I 11 1 B.1 — Detention Facilities B.2 — Inlets and Weirs Nnrth&mFnninworina_mm It 970.221.4152 E+me+*ot-1 Delenwn ao�now At� Ylo r,. i exM OverMw' SWrw�r r - . d nnTan POO \ 8eew.r Dry EG Po d -)W � NM Eo Pona O i Nnrt F.ornFnninrnrinn rnm // Q70.Y71.41 SR I NORTHERN 1 ENGINEERING 1 1 r-, J 1 1 1 1 1 1 1 1 1 1 I� 1 1 DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins ID'F Project Number 1076-001 Project Name West Village Off Taft Project Location Fort Collins, Colorado Pond No Pond A Input Variables Results Design Point a2 Design Storm 100-yr C = 0.47 Tc = 15.00 min A = 1.17 acres Max Release Rate = 0.26 cfs Required Detention Volume 6220 ft3 0.143 ac-ft Time (min) Ft Collins 100-yr intensity inlhr Inflow Volume (ft3) Outflow Adjustment Factor Qav (cfs) Outflow Volume (ft) Storage Volume (ft3) 5 9.950 1639 1.00 0.26 78 1561 10 7.720 2543 1.00 0.26 156 2387 15 6.520 3221 1.00 0.26 234 2987 20 5.600 3689 0.88 0.23 273 3416 25 4.980 4101 0.80 0.21 312 3789 30 4.520 4466 0.75 0.20 351 4115 35 4.080 4703 0.71 0.19 390 4313 40 1 3.740 4927 0.69 0.18 429 4498 45 3.460 5128 0.67 0.17 468 4660 50 3.230 5319 0.65 0.17 507 4812 55 3.030 5489 0.64 0.17 546 4943 60 2.860 5652 0.63 0.16 585 5067 65 2.720 5823 0.62 0.16 624 5199 70 2.590 5972 0.61 0.16 663 5309 75 2.480 6126 0.60 0.16 702 5424 80 2.380 6271 0.59 0.15 741 5530 85 2.290 6411 0.59 0.15 780 5631 90 2.210 6551 0.58 0.15 819 5732 95 2.130 6665 0.58 0.15 858 5807 100 2.060 6785 0.58 0.15 897 5888 105 2.000 6917 0.57 0.15 936 5981 110 1.940 7029 0.57 0.15 975 6054 115 1 1.890 7159 0.57 0.15 1014 6145 120 1 1.840 7273 0.56 0.15 1053 6220 Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2. 1076-001 DetentionVolume PondA FAAModified Method.xls Page 1 of 1 Aoowess: NORTHERN JOr N. Newva aura. sr+m +oo 97a.22t.At58 WE6SITE: ENGINEERING '-1 `""'"r CO a°s:' fAx. n"rtMm�ngmo ing.c"m 919.221.A159 Project Title West Village Off Taft Date: 11/9/2017 Project Number 1076-001 Calcs By: B. Mathisen Client Pond Designation Pond A ion 5082.06ft .artVgwvolurne 0.0095 ac-ft 100- r Detention Volume 0.1430 ac-ft me 0. L525 ac-ft v_D*(Al +A2+ A,*Ai/ 3 D = Depth between contours (ft.) Ai = Surface Area lower contour (ft') A2 = Surface Area upper contour (ft') .. ._ ._.. PondWIMe _ Elevation Surface Incremental Incremental Total Vol. Total Vol. (ft) Area (ft') Depth (ft) Vol. (ft') (ft3) (ac-ft) 5082.20 135.30 0.14 6.31 6.31 0.0001 5092.40 709.91 0.20 77.01 83.32 0.0019 5082.60 1460.37 0.20 212.57 295.89 0.0068 5082,80 2374.91 0.20 379.84 675.73 0.0155 5083.00 3457.44 0.20 579.86 1255.59 0.0288 5083.20 4354.03 0.20 779.43 2035.01 0.0467 5083.40 4956.05 0.20 930.36 2965.37 0.0681 5083.60 5401.25 0.20 1035.41 4000.78 0.0918 5083.80 5860.51 0.20 1125.86 5126.64 0.1177 5084.00 6340.76 0.20 1219.81 6346.46 0.1457 5084.20 6841.94 0.20 1317.95 7664.41 0.1760 5084.40 7363.42 0.20 1420.22 9084.63 0.2086 5084.60 1 7921,06 0.20 1528.11 10612.73 0.2436 Elevation Depth Volume WQCV 5082.66 0.60 0.0095 100-yr Detention 5083.98 1.92 0.1430 Overall Detention 5084.05 1.99 0.1525 WQCV 100-yr Vol Total Vol Dia (in.) i,a „ Min S, 1 n t 1/4 Area/Row 0.05 Required Area 0.060 sq-in Per Row No. of Rows 2 Total Outlet 0.10 s q. in. Area I 1 J VNONE ADDRESS: 970.221AISSNORTHERNwa.wYiE6SITE: ENGINEERING `"` cwa. co ws21 PAX, 970.221A159 Project Title Project Number Client Pond Designation West Village Off Taft Date: November 27, 2017 1076-001 Calcs By: B. Mathisen Pond A Q=CA 2g En-E Q = Release Rate (cfs) C = Discharge Coefficients (unitless) Aa = Area Allowed of Opening (ft) g = Gravity (32.2 ft/s') Eh = High Water Surface Elevation (ft) E; = Elevation of Outlet Invert (ft) Cos=yR—�B=2Cos -' lR E= A=�dtZ—K 2 j — Sln K= 2 H = Height of Opening (in.) R = Inner Radius of Outfall Pipe (in.) A = Top of Plate to Center of Pipe (in.) S = Arc Length of Open Area (in.) A = Area of Opening (in Z) B = Angle of Plate on Pipe to Center Pipe (radians) = 1.26 cfs = 0.605 Eh = 5084.05 ft = 5082.06 ft rA,0.183969 ftZ 26.4916 in' 26.08 sq. in. 1 Project Title Project Number Client Pond DesiRnatic NORTHERN ENQINEERIN0 West Taft Hill 1076-001 Pond A Q = Release Rate (cfs) C = Discharge Coefficients (unitless) A, = Area Allowed of Opening (ft) g = Gravity (32.2 ft/s') E„ = High Water Surface Elevation (ft) E; = Elevation of Outlet Invert (ft) E, = Elevation of Outlet Centroid (ft) Circular Orifice 100-Year Orifice Orifice Size (in.) 5 1/2 in. Area (in') 24.66 sq-in Q 1,18 cfs 3e-(taC Ilro 100-Year Orifice Orifice Height (in.) 5 in. Orifice Width (in.) 5 in. Area (in) 24.66 sq-in Q 1.19 cfs HON 11 AODRC33: 70.221A13! WEBSITE: iM Co�ln.. CO WS31 FAX, vWrw.nprtwninony4n.�r�r9 Coin 9]0.221 A159 Date: November 27, 2017 Calcs By: B. Mathisen Q = 1.26 cfs C = 0.65 Eh = 5084.05 ft E; = 5082.06 ft E,= 5082.29ft Circular E,= S082.27 ft Rectangular ft 10.171233099 24.657566 n NORTHERN ' ENGINEERING 1 1 'MMENMCM FaEFFAUCULATION;VOMPED FAAMETHOD wl Ft Collins OF Project Number : 1076-001 Project Name : West Village Off Taft Project Location : Fort Collins, Colorado Pond No Pond B Input Variables Results Design Point b1 Design Storm 100-yr C = 0.75 Tc = 10.00 min A = 1.19 acres Max Release Rate = 1.00 cfs Required Detention Volume 7862 ft3 0.180 ac-ft Time (min) Ft Collins 100-yr intensity n/hr Inflow Volume (ft3) Outflow Adjustment Factor Qav (cfs) Outflow s Volume (ft) Storage Volume (ft3) 5 9.950 2653 1.00 1.00 300 2353 10 7.720 4117 1.00 1.00 600 3517 15 6.520 5215 0.83 0.83 750 4465 20 5.600 5972 0.75 0.75 900 5072 25 4.980 6639 0.70 0.70 1050 5589 30 4.520 7231 0.67 0.67 1200 6031 35 4.080 7615 0.64 0.64 1350 6265 40 3.740 7977 0.63 0.63 1500 6477 45 3.460 8303 0.61 0.61 1650 6653 50 3.230 8612 0.60 0.60 1800 6812 55 3.030 8887 0.59 0.59 1950 6937 60 2.860 9151 0.58 0.58 2100 7051 65 2.720 9428 0.58 0.58 2250 7178 70 2.590 9668 0.57 0.57 2400 7268 75 2.480 9918 0.57 0.57 2550 7368 80 2.380 10153 0.56 0.56 2700 7453 85 2.290 10380 0.56 0.56 2850 7530 90 2.210 10606 0.56 0.56 3000 7606 95 2.130 10790 0.55 0.55 3150 7640 100 2.060 10985 0.55 0.55 3300 7685 105 2.000 11198 0.55 0.55 3450 7748 110 1.940 11380 0.55 0.55 3600 7780 115 1.890 11590 0.54 0.54 3750 7840 120 1.840 11774 0.54 0.54 3900 7862 'Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2. 1076-001_DetentionVolume_PondB_FAAModified Method.xls Page 1 of 1 NORTHERN •°°"E_�""` 1o,n HoS: seen. sdm.00 970.21A158 WE631TE: ENGINEERING inx. eertbmee9Ma M9.cem ..221A15Y Project Title West Village Off Taft Date: 11/27/2017 Project Number 1076-001 Calcs By: B. Mathisen Client Pond Designation Pond 8 Invert Elevation 5083.03 k -- - Water Quality Volume 0.0000ac-ft 300- r Detention Volume 0.1805 ac-ft _ e 0.1805 ac-ft j,_D•A,+A2+ A,*A2/ 3 D = Depth between contours (ft.) A2 = Surface Area lower contour (k2) A2 - Surface Area upper contour (ft) Elevation Surface Incremental Incremental Total Vol. Total Vol= (ft) Area (ft') Depth (ft) Vol. (ft') (ft;) (ac-ft) 5083.20 369.44 0.17 20.69 20.69 0.0005 5083.40 861.05 0.20 119.63 140.32 0.0032 5083.60 1685.41 0.20 250.08 390.40 0.0090 5083.80 2870.65 0.20 450.38 940.77 0.0193 5084.00 435SA6 0.20 717.44 1558.22 0.0358 5084.20 5661.45 0.20 998,81 2557.03 0.0587 5084.40 6465.79 0.20 1211.83 3768.86 0.0865 5084.60 6772.74 0.20 1323.73 5092.60 0.1169 5084.80 7110.34 0.20 1388.17 6480.77 0.1486 5085.00 7449.87 0.20 1455.89 7936.66 D,1822 5085.20 7790,27 0.20 1523.89 9460.54 0.2172 5085.40 1 3132.22 0.20 1592,13 11052.67 0.2537 Elevation Depth Volume 100-yr Detention Overall Detention 5084.99 5084.99 1.96 1.96 0.1805 0.1805 Total Vol Project Title Project Number Client Pond Designation : NORTHERN "°°REss ENGINEERING West Village Off Taft 1076-001 Pond B Q=CA 28(Ee—E� Q = Release Rate (cfs) C = Discharge Coefficients (unitless) A, = Area Allowed of Opening (ft') g = Gravity (32.2 ft/s2) Eh = High Water Surface Elevation (ft) E, = Elevation of Outlet Invert (ft) ' Cos=7R---)B=2Cos-1 JR S=RB ' RZ jR—Sin �R K= � ' H = Height of Opening (in.) R = Inner Radius of Outfall Pipe (in.) A = Top of Plate to Center of Pipe (in.) S = Arc Length of Open Area (in.) A = Area of Opening (in 2) PHONE: 970.221.4158 WESSITE: FAA: --- www.north�mon9�n�onny.com 970.221.4159 Date: August 14, 2017 Calcs By: B. Mathisen 1.00 cfs = 0.605 Eh = 5084.99 ft E; = 5083.03 ft 0.147196 ft' A, 21.19619 in' C B = Angle of Plate on Pipe to Center Pipe (radians) Proposed Outfall Pipe Diameter 12 in Design Height of Opening (H) 2-7/8 in Calculated Area of Opening (AJ 20.82 sq. in. PHONE: INORTHERNADDRESS: 970.21.415Er4p oo+ w.�NWEBSITE: ENGINEERINGcenm, co 90521 /A%+ ......no 1h.m.nyM.Mny.cwn 970.224.4159 I:_ _- Project Title West Taft Hill Village Date: November 9, 2017 Project Number 1076-001 Calcs By: B. Mathisen Client Pond Designation Pond B Q= Release Rate (cfs) C = Discharge Coefficients (unitless) A. = Area Allowed of Opening (ft) g = Gravity (32.2 ft/sz) Eh = High Water Surface Elevation (ft) E; = Elevation of Outlet Invert (ft) E; = Elevation of Outlet Centroid (ft) Circular Orifice 100-Year Orifice Orifice Size (in.) 5 in. Area (in') 1 19.72 sq-in Q 0.95 cfs Rectangular Orifice 100-Year Orifice Orifice Height (in.) 5 in. Orifice Width (in.) 4 in. Area (in 2) 19.72 sq-in Q 0.95 cfs Q= 1,00cfs C = 0.65 Eh = 5084.99 ft E, = 5083.03 ft E,= 5083.24ft Circular E,= 5083.24 ft Rectangular ft L0.136935381 Az 19.718695 inz t I 11 1 Nn,tharnPnninaa rinn s nm 11 970.271.41 SR pp N C C H �o O N H� O � o ' i i O T Z O � W a � a d a 0 d N W � n N � A C7 fJ � 1l a yN X rw c D � (D O O N � � O W Co N N ' N t0 O 1 Capacity (cfs) IJ NI In O + N N N N �1 O fJ to +l N O N O UI I J 1 1 i 1 J 1 1 1 1 7 L 1 1 1 1 u I 1 I 1 1 I 1 1 IT f.11 0 0 0 tll 0 n) OD N co m m O w O O I O Sta 0+00.00 - Outfall - Grnd. El. 5084.89 Inv. El. 5084.16 In m N G W O A O � I N S O Sta 0+60.00 - Ln: 1 rn o Grnd. El. 5088.50 Inv. El. 5085.36 Out 0 eo 0 O o I 0 0 0 0 0m o W Ul CD w {D A -4 O 0 O 0 O 0 O 0 O 0 O 0 crd CD Mi ml O rt I I [J I !y 3 zr o Z O O N m z (n ;a m O D _ Er D a CD m � W m r a cn m n o N O N _T N E g O O ^tnr A m OD y r n � W m �r xCM o m o O 7 N vY r A y O � Of mg o r< CD c� v m o N O 7 O O (D Y z m O G) f r 3 A 7 N w V O 7 CD O D o CD N r V o xN 3 V y � O rY j OD p R r C V 7 O m m m 0 S 7 7 m y _ CL N V_ N 0 z N K C W n O 3 I I i I I I I I I I I I I I I I IT 9 to i r Z p J N J m y Z (p i p O D (i m W o A n w No CD v � N � x 3 A < m n 0 CD NoOD m 2 r _ w J Q n o v x w 0 x S v O N D � � a x m y d tD N — xmm O J w — O, 0 N m x ci < r A A A p e � O O O O � O O N < D W N N = co v:O C) N < r J p x CD 'O Z s c o D_ a m a o x d w o N N 3 p cn— (D fD J O. CD m x w m N < r N A o M O ZJ C O p M 00 p m n 7 O W A � xo m v N 7 N � O V 0 r, O p s o 3 OJ N N O 1 Weir Report Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Pond A - Emergency Overflow Weir ' Trapezoidal Weir Crest = Sharp Bottom Length (ft) = 15.00 Total Depth (ft) = 0.50 Side Slope (z:1) = 4.00 Calculations Highlighted Depth (ft) Q (cfs) Area(sgft) Velocity (ft/s) Top Width (ft) Weir Coeff. Cw = 3.10 'Compute by: Known Q Known Q (cfs) = 13.88 =130% of Q100 for Basin A and Basin B lepth (ft) Pond A - Emergency Overflow Weir 1.00 0.50 1 1 0.00 ' -0.50 0 2 4 6 8 10 12 Weir W.S. Monday, Aug 14 2017 = 0.43 = 13.88 = 7.19 = 1.93 = 18.44 Depth (ft) I 1.00 0.50 W1 -0.50 22 24 Length (ft) I Weir Report Hydraflow Express Extension for Autodesk® Auto CAD® Civil 3D® by Autodesk, Inc. Pond B - Emergency Overflow Weir Trapezoidal Weir Crest = Sharp Bottom Length (ft) = 10.00 Total Depth (ft) = 0.50 Side Slope (z:1) = 4.00 ' Calculations Weir Coeff. Cw = 3.10 'Compute by: Known Q Known Q (cfs) = 9.14=130% of Q100 for Basin B Highlighted Depth (ft) Q (cfs) Area (sqft) Velocity (ft/s) Top Width (ft) epth (ft) Pond B - Emergency Overflow Weir ' 1.00 0.50 1 0.00 ' -0.50 0 2 4 6 8 ' Weir W.S. Monday, Aug 14 2017 = 0.41 = 9.139 = 4.77 = 1.91 = 13.28 Depth (ft) 1.00 0.50 1 11 -0.50 10 12 14 16 18 Length (ft) C 1 I I r I 1 NnrtharnFnni nna. rinn.tnm // 970-771.41SR PHONE: NORTHERN '01MMADDRESS: 970.221.4159 i01 M"Wef 91ree1, Sidle 100 ENGINEERING "`" °°°"' FAX: 970.221,4159 Project Title West Village Off Taft Date: Project Number 1076-001 Calcs By: Client Pond Designation Pond A WQCV=a0.91i1-1.19i2+0.79i Drain 40hr -I aA 1 WQCV = Watershed inches of Runoff (inches) 16.00% a = Runoff Volume Reduction (constant) i =Total imperviousness Ratio (i = Iwq/100) WQCV = 0.098 in Water Quality Capture Volume 0.5 0.45 WQCV =a(0.91i'-1.19i2+0.78i) 0.4 L c 0.35 a 0.3 r a 0.25 3 0.2 > 0.15 0.09E� 0.1 3 0.05 0 IWEBSITE: �: www.nOrthernongineermg.c"m August 9, 2017 B. Mathisen 6 hr ---- 12 hr 24 hr 40 hr 0 0 0 o O O O O O O «- O O O O O O O O D O O O Total Imperviousness Ratio (i = Iwq/100) Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event V — WQCV \ A — 1.17 ac 12 0.0095 ac-ft 415.77 cu. ft. V = Water Quality Design Volume (ac-ft) WQCV = Water Quality Capture Volume (inches) A = Watershed Area (acres) NORTHERN ENGINEERING PHONE: ADDRESS: 970.221.4158 301 N. Howes Street, Suite 100 WEBSITE: Fort Collins, CO 80521 FAX: www.northernengineering.com 970.221.4159 Filterra Sizing Calculation: Water Quality Treatment Flow: 0.705 cfs Filterra infiltration Rate: 0.00324 ft/sec Required Square Footage to achieve treatment flowrate: 0.705/0.00324=217.59 sq. ft. Square footage provided by (2) 14'x8' Filterra Units: 224 sq. ft. I I II II II II II 11 to com CONNIM 1J y®�--�-- • ffiacr nw Nnrtharn Fnnin as rinn.rnm // Q70 771.41 SR ' (NORTHERN ENGINEERING South Taft Hill A comprehensive Erosion and Sediment Control Plan (along with associated details) will be included with the final construction drawings. It should be noted, however, that any such Erosion and Sediment Control Plan serves only as a general guide to the Contractor. Staging and/or phasing of the BMPs depicted, and additional or different BMPs from those included may be necessary during construction, or as required by the authorities having jurisdiction. rIt shall be the responsibility of the Contractor to ensure erosion control measures are properly maintained and followed. The Erosion and Sediment Control Plan is intended to be a living document, constantly adapting to site conditions and needs. The Contractor shall update the location of BMPs as they are installed, removed or modified in conjunction with construction activities. It is imperative to appropriately reflect the current site conditions at all times. ' The Erosion and Sediment Control Plan shall address both temporary measures to be implemented during construction, as well as permanent erosion control protection. Best Management Practices from the Volume 3, Chapter 7 — Construction BMPs will be utilized. Measures may include, but are not limited to, silt fencing along the disturbed perimeter, gutter protection in the adjacent roadways and inlet protection at proposed storm inlets. Vehicle tracking control pads, spill containment and ' clean-up procedures, designated concrete washout areas, dumpsters, and job site restrooms shall also be provided by the Contractor. ' Grading and Erosion Control Notes can be found on Sheet C62 of the Utility Plans. The Utility Plans at final design will also contain a full-size Erosion Control Plan as well as a separate sheet dedicated to Erosion Control Details. In addition to this report and the referenced plan sheets, the ' Contractor shall be aware of, and adhere to, the applicable requirements outlined in any existing Development Agreement(s) of record, as well as the Development Agreement, to be recorded prior to issuance of the Development Construction Permit. Also, the Site Contractor for this project will be required to secure a Stormwater Construction General Permit from the Colorado Department of Public Health and Environment (CDPHE), Water Quality Control Division — Stormwater Program, before commencing any earth disturbing activities. Prior to securing said permit, the Site Contractor shall develop a comprehensive StormWater Management Plan (SWMP) pursuant to CDPHE requirements and guidelines. The SWMP will further describe and document the ongoing activities, inspections, and maintenance of construction BMPs. 1 Final Erosion Control Report MAP POCKET ' HISTORIC DRAINAGE EXHIBIT PROPOSED DRAINAGE EXHIBIT 1 1 1 1 NnrthnrnEnnin"rinn.rnm // 970.771.615A USE SO IS In FEET) 1 LID TABLE: - ._-- t Oeslin Bazln 10 Basin Area Treatment TYPe NU PoIMelAl 1.16Aac. No - 0.313 x.bl Mo.m Bla sac Flkerta Yes 0.5%x.Tote)1.353x. 0.811 x. SUMMARY TABLE: ilizaam mw will uRA a am n BD n w w al AT 1.17 COX) EASS at at 1.IB 1150 SJ5 130 1 99 1 L.41 ).W I LEGEND PRIMARILY IV VERTICAL GIBS AND GUETTE+ PBGPreEDDOmGIR ---tiaw---- EXURING TNATBw EGAME SLOPE PRDroaFo OVI RUNI ISSUE FIRESTONE y CONCENTRATED ELM DIRECTION (1 PUSTNGIHETGRI URGE F/ISTNGICOARF. TRE o EXISTING LIGHT PETER gjPARTNER STOW INAGE PAGES AREA �__ _ �AINAGEBASIS BANKER AL.IG, GGEFF. 0 OEGONPOINT TOP OF Ppp EIEVATIO4 MCCYELEVATKKI LEGEND: t. BBBIro T1E SMLL MNVTIEIEIM R FOR ADDITIONAL VFTAFr IO xmmmx EwlxaelwB. aATEo nn>xn Fw ADG+wNR<IHFORIMTILW. FOR DRAINAGE REVIEW ONLY NOT FOR CONSTRUCTION PLAN APPROVAL APPROVED an, mISSI pf. CIEIXm BY: 41q IS 1"G,'tV D{Iny GAP CIEIMEO BY: So�Ps EC�t1 qt. (STIESSAIM BY: ..�FbTR.on.T.R r MECRM BN _ v GIECNEO Br w ^^E^, w PSe.. B.Y Z c.0 A Z E S W W A ZW i g So4 gi LL FQ- 0] LL = O w w z `g W 0 Sheet C7.00 15 of 18 DINNER IDLAQKJAAM 1 I1 • � ly y II ,I II U. I b I I y_ fW .I — It l - �lo II AD / AS `%& I �� I I / ----4 J' ASS. -- LOTI I \lltpELY6i1NMAlO tlNNI MA I i LME LOi31 LOTII LOF9 I I 1 / I / AS AD AS AAA YAL YA, AA, Orr I j \ I aHt I T f \\ I I ! It jjW AAA AAA i AAA AAA 'DYSYYY AS ] AS AD N it f______________________ I , two _____� k,— ------------ 7 ----------- Inr> sorb Lora \ \ Imb - __ wADEeEar THrm FllxO \ SUMMARY TABLE: DESIDN BASIX DIW PDIM ID MG C] CIOD Ts h WI) NY III MI Lb 0]! D]5 Ibb tlJ 1% sm A•:• 1 w Sit IFEEL) x a'il LEGEND: �� EwsnxG EUBe/OJLiFA fIONLWE ___tigyo---_Eomxc caxTaW -- mww saPE .i..s 1`110P05ED oiEIMND Mw EIRII H CIXICEn1RATED FLOW DREnON EYISTING INLET CRATE EXISTING OECD. TREE EGSTING Cp11F TWEE A EESI LIOIT PqE ^� EMISTING STUMP ¢ 10 DRAINAGE BASIN DRBASIN A MAINAGE ORAINAC£ BASH MINORMAJOR COEF. QOENCN POINT 2m a iyZ R W� s S W W N Q E� LEGEND: Zw 1 WAVETM�NTNE 41Wi dW1UpEP£PCM Fpi NFAVLIN3ECPFiAF1'BY ExxxEERxe. DATED I t :vron FOR ADonovu xeroMAmN. �D as 44 FOR DRAINAGE REVIEW ONLY NOT FOR CONSTRUCTION CALL kJory NTFIGTW CEMER Ci COUNAM 10 x,..emarsbelow. Call bef«e you aiR. GAL DIG WILD, SIR Ai FDA THE City of Fort Collins, Colorado UTILITY PLAN APPROVAL AnPROGED: Coy B..1..., u k. «E«ED eY: MI w T'n... t.. Utility a cxE«eD er: U D ILI ll1ECNED BY: CHECKED BC Tonle olwa.ee. CHECKED BY: CD X ILL. H W IL W U_ (D O Q W z J J_ Q w 3 0