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Home My WebLink AboutMAVERIK CONVENIENCE STORE & FUEL SALES - PDP - PDP150028 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT‘ Preliminary Drainage Report for Maverik City of Fort Collins, Colorado Developer: Maverik Inc 880 West Center Street Salt Lake City, UT 84054 801.335.3851 Contact: Don Lilyquist Engineer: Atwell, LLC 143 Union Blvd, Suite 700 Lakewood, CO 80228 303.462.1100 Project Number 15001770 November, 2015 I hereby certify that this Preliminary Drainage Report for the design of Maverik was prepared by me or under my direct supervision in accordance with the provisions of the Urban Drainage and Flood Control District Manual and the Fort Collins Amendments for the owners thereof. I understand that the City of Fort Collins does not and will not assume liability for drainage facilities designed by others. ______________________________ Registered Professional Engineer State of Colorado No. ________ I hereby certify that the drainage facilities for Maverik shall be constructed according to the design presented in this report. I understand that the City of Fort Collins does not and will not assume liability for the drainage facilities designed and/or certified by my engineer. I understand that the City of Fort Collins review drainage plans but cannot, on behalf of Maverik, guarantee that final drainage design review will absolve The Maverik, LLC and/or their successors and/or assigns of future liability for improper design. I further understand that approval of the Final Development Plan does not imply approval of my engineer’s drainage design. _________________________________ Name of Developer _________________________________ Authorized Signature Date Table of Contents Introduction 1 Drainage System Description 1 Drainage Analysis and Design Criteria 3 Grading and Erosion and Sediment Control Plan 3 Stormwater Management Plan 3 Conclusions 3 References 4 Appendix A – Reference Hydrologic Soil Group Report Appendix B – Hydrologic Calculations Historic Composite Run-off Coefficients Historic Time of Concentration Historic Minor Storm Runoff Calculations Historic Major Storm Runoff Calculations Composite Run-off Coefficients Time of Concentration Minor Storm Runoff Calculations Major Storm Runoff Calculations Appendix C – Stormwater Quality Calculations Detention Volume by the Full Spectrum Method Historic Drainage Plan Back Pocket Preliminary Drainage Plan Back Pocket                                                     I. Introduction The purpose of this report is to provide a guide for the City of Fort Collins and the developer to use for the planning and final design of drainage facilities for the Maverik development site. The Maverik development site occupies 1.77 acres that includes Lot 2 of Maverik Subdivision Filing No. 1 and Lot 17 of Interchange Business Park. The site is located within the Northwest one-quarter of Section 15, Township 7 North, Range 68 West of the 6th Principal Meridian. The parcel’s street frontage is along I-25 Frontage Road with an address of 4333 E. Mulberry Street. The site is bounded by Lot 1 of Maverik Subdivision Filing No. 1 to the south and west; the Frontage Road to the south and east; and CDOT ROW for Intersate-25 to the north. A vicinity map is included within Appendix A of this report. The proposed development site currently has a round brick building that formerly served as a restaurant. The east side of the site generally slopes from north to south at about a 1percent grade, while the west side generally slopes from east to west. Both sides of the site drain to grated inlets within the existing parking lot that discharge flow into an existing detention pond on the north side of the site. This detention pond has a controlled outlet that discharges to a roadside drainage swale along the I-25 off-ramp to E. Mulberry Street. Soils on the site are identified as Fort Collins loam, which is a Hydrologic Group B soil. Refer to the soils map in Appendix A of this report for additional soils information. The proposed use for the redeveloped property is a convenience store & fueling station. The development parcel lies within the limits of the Boxelder Creek Regional Master Plan. The development site is identified as outside of the 100-yr floodplain (Zone X) as shown on the flood insurance rate map number 08069C1003G, dated May 2, 2012. II. Drainage System Description As stated in section I, the east side of the site generally slopes from north to south at about 1percent, while the west side generally slopes from east to west. There is an existing detention pond in the northwest corner of the property. The outfall drainage way is identified as a tributary of Boxelder Creek in the aforementioned Regional Master Plan. Under existing conditions, runoff from the site reaches the outfall drainage way via area drains in the parking                                                        lot on the south side of the site and west of the pond. The proposed development contains a gas station configuration replacing the existing restaurant building along with expanding to the northeast with parking, a rest with tot lot area, and a dog park. Sub-Basin A, comprising of 1.21 acres, contains the new building, the new canopy, most of the parking lot, and the recreation area & dog park. Sub-Basin A drains to an existing grated inlet near the south driveway entrance which then conveys the flows via an 18” reinforced concrete pipe to the pond. Sub-Basin B, comprising of 0.32 acres, contains the northern driveway, the new outdoor dining area, and the back side of the new building. Sub- Basin B drains west off property, then to the northwest to an existing grated inlet, just west of the existing detention pond, on the adjacent property that then conveys the flows via an 18” reinforced concrete storm sewer pipe. Both storm sewers combine into the detention and water quality pond in the northwest corner of the property. Sub-Basin C consists of a slim strip of land encompassing 0.02 acres on the southeast side of the new building. Sub-Basin C drains to 2 grated slot drains inside of the sub-basin, which convey the flows northeast to the 18” reinforced concrete storm drain sewer pipe in Sub-Basin A. Sub-Basin D, comprising of 0.16 acres, is the area of land that contains the existing detention pond. Sub-Basin D will not be altered by site development. Rational Method Calculations of site-generated runoff for the 2-year and 100-year storm events are included in the appendix. The existing on-site detention pond will be reused in its’ existing condition. Detention volumes and release rates are as follows: Stage Volume (acre-feet) Release Rate (cfs) 100-yr detention 0.26 1.45 Excess Urban Runoff Volume (EURV) 0.14 72-hour drain time Detained storm water from the site will be discharged toward the northwest through the existing outlet structure located at the northwest end of the pond. The outlet will discharge to the existing swale just beyond the northwest property line, which is identified as the outfall from storm water flows in this area. No changes are proposed to the existing outlet structure or pond at this time.                                                        III. Drainage Analysis and Design Criteria Drainage analysis and facility design has been prepared in accordance with UDFCD standards and the Fort Collins Amendments. Essentially all the flow from Basins A, B, & C are collected by the slot drains. IV. Grading and Erosion and Sediment Control Plan A Grading Plan has been prepared and is included in the Preliminary Development Plans. An Erosion & Sediment Control Plan will be included in the Final Development Plan. V. Storm Water Management Plan All phases of construction will provide temporary erosion control measures in accordance with Urban Storm Drainage Criteria Manual and as required by the Colorado Department of Health. These measures will remain in place until the permanent erosion control facilities are in place. Storm water management and erosion control measures will be included in the Storm Water Management Plan (SWMP). Standard best management practices (BMP’s) will be employed as required by References 1 and 2. VI. Conclusions This study is in compliance with the Urban Storm Drainage Criteria Manual and the Fort Collins Amendments. This study is also consistent with the overall drainage concept in previously prepared regional drainage study (References 3). The proposed development and proposed drainage facilities will result in no adverse impacts created by the quantity or quality of storm water generated by this project.                                                        VII. References 1. Urban Storm Drainage Criteria Manual; Denver Regional Council of Governments; August 2011. 2. Fort Collins Amendments to the Urban Drainage and Flood Control District Criteria Manual; City of Fort Collins; December 12, 2012 3. Final Boxelder Creek Regional Stormwater Master Plan; Larimer County & Boxelder Creek Regional Alliance; October 2006 4. Floor Insurance Rate Map, Larimer County, Map Number 08069C1003G; Federal Emergency Management Agency; May 2, 2012 Appendix A Reference Hydrologic Soil Group—Larimer County Area, Colorado Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 11/16/2015 Page 1 of 4 4491990 4492030 4492070 4492110 4492150 4492190 4492230 4492270 4491990 4492030 4492070 4492110 4492150 4492190 4492230 4492270 499960 500000 500040 500080 500120 500160 500200 500240 500280 500320 500360 499960 500000 500040 500080 500120 500160 500200 500240 500280 500320 500360 40° 34' 52'' N 105° 0' 2'' W 40° 34' 52'' N 104° 59' 43'' W 40° 34' 43'' N 105° 0' 2'' W 40° 34' 43'' N 104° 59' 43'' W N Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84 0 50 100 200 300 Feet 0 30 60 120 180 Meters Map Scale: 1:2,030 if printed on A landscape (11" x 8.5") sheet. MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Rating Polygons A A/D B B/D C C/D D Not rated or not available Soil Rating Lines A A/D B B/D C C/D D Not rated or not available Soil Rating Points A A/D B B/D C C/D D Not rated or not available Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:24,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: http://websoilsurvey.nrcs.usda.gov Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Larimer County Area, Colorado Hydrologic Soil Group Hydrologic Soil Group— Summary by Map Unit — Larimer County Area, Colorado (CO644) Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 34 Fort Collins loam, 0 to 1 percent slopes B 10.9 63.6% 73 Nunn clay loam, 0 to 1 percent slopes C 5.5 32.3% 76 Nunn clay loam, wet, 1 to 3 percent slopes C 0.7 4.1% Totals for Area of Interest 17.1 100.0% Description Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long-duration storms. The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (A/D, B/D, and C/D). The groups are defined as follows: Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes. Hydrologic Soil Group—Larimer County Area, Colorado Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 11/16/2015 Page 3 of 4 Rating Options Aggregation Method: Dominant Condition Component Percent Cutoff: None Specified Tie-break Rule: Higher Hydrologic Soil Group—Larimer County Area, Colorado Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 11/16/2015 Page 4 of 4 Appendix B Hydrologic Calculations COMPOSITE C-FACTOR & WEIGHTED PERCENT IMPERVIOUSNESS ANALYSIS Maverik Atwell, LLC CBS Date: Nov 2015 Historic Runoff Coefficients C2 C100 I (%) Landscaping 0.08 0.52 5.0% Paved Area 0.89 0.96 100.0% (Table 1, Ref. 1) Roof Area 0.73 0.83 90.0% (Table 1, Ref. 1) Total Area Landscaping Paved Area Roof Area BASIN (AC) (AC) (AC) (AC) Comp. C2 Comp. C100 Comp. I (%) OS1 0.01 0.01 0.0001 0.00 0.09 0.53 6.1% OS2 0.08 0.08 0.00 0.00 0.08 0.52 5.0% A 1.25 0.49 0.52 0.24 0.55 0.76 61.3% B 0.25 0.01 0.25 0.00 0.87 0.95 97.6% C 0.01 0.01 0.00 0.00 0.27 0.62 27.1% D 0.16 0.16 0.00 0.00 0.08 0.52 5.0% Composite On-Site Basins 1.68 0.66 0.77 0.24 0.55 0.77 61.0% STANDARD FORM SF-2 HISTORIC TIME OF CONCENTRATION PROJECT: Maverik CALCULATED BY: CBS DATE: Nov 2015 SUB-BASIN DATA INITIAL/OVERLAND TRAVEL TIME Tc CHECK FINAL REMARKS TIME (Tc) (Tt) (Urbanized Basins) Tc DESIGN: AREA C5 LENGTH AVG. SLOPE Ti LENGTH AVG. SLOPE VEL Tt COMP TOTAL Tc=(L/180)+10 (acres) (ft) (%) (min) (ft) (%) (fps) (min) Tc LENGTH (ft) (min) (min) OS1 0.01 0.53 13 2.4 2.8 0.0 2.8 13 10.1 5.0 OS2 0.08 0.52 40 11.8 2.9 0.0 2.9 40 10.2 5.0 A 1.25 0.76 233 1.3 8.5 271 0.5 1.4 3.2 11.7 504 12.8 11.7 B 0.25 0.95 205 0.9 4.0 176 0.8 1.7 1.7 5.7 381 12.1 5.7 C 0.01 0.62 27 5.5 2.6 317 0.5 0.5 10.7 13.2 344 11.9 11.9 D 0.16 0.52 40 2.0 5.3 0 5.0 1.6 5.3 40 10.2 5.3 CBS JOB NO: 15001770 DATE: Nov 2015 PROJECT: Maverik CHECKED BY: DESIGN STORM: 2-year DESCRIPTION DESIGN POINT AREA DESIG. AREA (Acres) RUNOFF COEFF Tc (min) C A (Acres) I (in/hour) Q (cfs) Tc (min) (C A) (Acres) I (in/hour) Q (cfs) OS1 1 OS1 0.01 0.09 5.0 0.00 2.88 0.003 OS2 2 OS2 0.08 0.08 5.0 0.01 2.88 0.02 A 4 A 1.25 0.55 11.7 0.68 2.16 1.5 B 5 B 0.25 0.87 5.7 0.22 2.78 0.6 C 6 C 0.01 0.27 11.9 0.00 2.14 0.01 D 7 D 0.16 0.08 5.3 0.01 2.84 0.04 . . 2-year P1 = 0.85 inches (UDFCD, Fig. RA-1) I = 28.5(P1)/(10+Tc) 0.786 (Ref. 2, Eq RA-3) STANDARD FORM SF-3 STORM DRAINAGE SYSTEM DESIGN (RATIONAL METHOD PROCEDURE) HISTORIC CALCULATED BY: DIRECT RUNOFF TOTAL RUNOFF CBS JOB NO: 15001770 DATE: Nov 2015 PROJECT: Maverik CHECKED BY: DESIGN STORM: 100-year DESCRIPTION DESIGN POINT AREA DESIG. AREA (Acres) RUNOFF COEFF Tc (min) C A (Acres) I (in/hour) Q (cfs) Tc (min) (C A) (Acres) I (in/hour) Q (cfs) OS1 1 OS1 0.01 0.53 5.0 0.01 9.06 0.1 OS2 2 OS2 0.08 0.52 5.0 0.04 9.06 0.4 A 4 A 1.25 0.76 11.7 0.96 6.78 6.5 B 5 B 0.25 0.95 5.7 0.24 8.72 2.1 C 6 C 0.01 0.62 11.9 0.01 6.72 0.05 D 7 D 0.16 0.52 5.3 0.09 8.93 0.8 100-year P1 = 2.67 inches (UDFCD, Fig. RA-6) I = 28.5(P1)/(10+Tc) 0.786 (Ref. 2, Eq RA-3) HISTORIC (RATIONAL METHOD PROCEDURE) STORM DRAINAGE SYSTEM DESIGN STANDARD FORM SF-3 CALCULATED BY: DIRECT RUNOFF TOTAL RUNOFF COMPOSITE C-FACTOR & WEIGHTED PERCENT IMPERVIOUSNESS ANALYSIS Maverik Atwell, LLC CBS Date: Nov 2015 Runoff Coefficients C2 C100 I (%) Landscaping 0.08 0.52 5.0% Paved Area 0.89 0.96 100.0% (Table 1, Ref. 1) Roof Area 0.73 0.83 90.0% (Table 1, Ref. 1) Total Area Landscaping Paved Area Roof Area BASIN (AC) (AC) (AC) (AC) Comp. C2 Comp. C100 Comp. I (%) OS1 0.01 0.01 0.00 0.00 0.08 0.47 5.5% OS2 0.05 0.05 0.00 0.00 0.08 0.52 5.0% A 1.21 0.23 0.69 0.29 0.70 0.85 79.5% B 0.32 0.05 0.27 0.00 0.76 0.89 85.1% C 0.02 0.02 0.00 0.00 0.08 0.51 4.9% D 0.16 0.16 0.00 0.00 0.08 0.52 5.0% Composite On-Site Basins 1.71 0.46 0.96 0.29 0.64 0.82 72.6% PROJECT: Maverik CALCULATED BY: CBS DATE: Nov 2015 SUB-BASIN DATA INITIAL/OVERLAND TRAVEL TIME Tc CHECK FINAL REMARKS TIME (Tc) (Tt) (Urbanized Basins) Tc DESIGN: AREA C5 LENGTH AVG. SLOPE Ti LENGTH AVG. SLOPE VEL Tt COMP TOTAL Tc=(L/180)+10 (acres) (ft) (%) (min) (ft) (%) (fps) (min) Tc LENGTH (ft) (min) (min) OS1 0.01 0.53 13 2.4 2.8 0.0 2.8 13 10.1 5.0 OS2 0.05 0.52 40 11.8 2.9 0.0 2.9 40 10.2 5.0 A 1.21 0.85 358 1.5 7.6 271 0.5 1.4 3.2 10.8 629 13.5 10.8 B 0.32 0.89 254 0.5 7.6 175 0.5 1.4 2.1 9.6 429 12.4 9.6 C 0.02 0.51 25 1.1 5.2 317 0.5 0.5 10.7 15.9 342 11.9 11.9 D 0.16 0.52 40 2.0 5.3 0 5.0 0.0 5.3 40 10.2 5.3 TIME OF CONCENTRATION STANDARD FORM SF-2 CBS JOB NO: 15001770 DATE: Nov 2015 PROJECT: Maverik CHECKED BY: DESIGN STORM: 2-year DESCRIPTION DESIGN POINT AREA DESIG. AREA (Acres) RUNOFF COEFF Tc (min) C A (Acres) I (in/hour) Q (cfs) Tc (min) (C A) (Acres) I (in/hour) Q (cfs) OS1 1 OS1 0.01 0.081 5.0 0.001 2.88 0.003 OS2 2 OS2 0.05 0.519 5.0 0.03 2.88 0.1 A 4 A 1.21 0.70 10.8 0.85 2.23 1.9 B 5 B 0.32 0.76 9.6 0.24 2.33 0.6 C 6 C 0.02 0.08 11.9 0.00 2.14 0.003 D 7 D 0.16 0.08 5.3 0.01 2.84 0.04 . . 2-year P1 = 0.85 inches (UDFCD, Fig. RA-1) I = 28.5(P1)/(10+Tc) 0.786 (Ref. 2, Eq RA-3) CALCULATED BY: DIRECT RUNOFF STANDARD FORM SF-3 STORM DRAINAGE SYSTEM DESIGN (RATIONAL METHOD PROCEDURE) REDEVELOPED TOTAL RUNOFF CBS JOB NO: 15001770 DATE: Nov 2015 PROJECT: Maverik CHECKED BY: DESIGN STORM: 100-year DESCRIPTION DESIGN POINT AREA DESIG. AREA (Acres) RUNOFF COEFF Tc (min) C A (Acres) I (in/hour) Q (cfs) Tc (min) (C A) (Acres) I (in/hour) Q (cfs) OS1 1 OS1 0.01 0.47 5.0 0.01 9.06 0.1 OS2 2 OS2 0.05 0.52 5.0 0.03 9.06 0.2 A 4 A 1.21 0.85 10.8 1.03 7.00 7.2 B 5 B 0.32 0.89 9.6 0.28 7.33 2.1 C 6 C 0.02 0.51 11.9 0.01 6.73 0.1 D 7 D 0.16 0.52 5.3 0.09 8.93 0.8 100-year P1 = 2.67 inches (UDFCD, Fig. RA-6) I = 28.5(P1)/(10+Tc) 0.786 (Ref. 2, Eq RA-3) CALCULATED BY: STANDARD FORM SF-3 STORM DRAINAGE SYSTEM DESIGN (RATIONAL METHOD PROCEDURE) REDEVELOPED DIRECT RUNOFF TOTAL RUNOFF Appendix C Stormwater Quality Calculations Project: Basin ID: 1.71 72.6% 0 72.6% Percentage of Area Area (acres) 0.0 100.0% 1.7 0.0 Initial--f i Final--fo 4.5 0.6 0.0018 (watershed inches) (acre-feet) 0.98 0.14 Design Oulet to Empty EURV in 72 Hours 100-year Detention Volume plus WQCV 5 1.84 0.26 1.45 Notes: * User input data shown in blue. 2) Results shown reflect runoff reduction from Level 1 or 2 MDCIA and are plotted at the watershed's total imperviousness value; the impact of MDCIA is reflected by the results being below the curves. 3) Maximum allowable release rates for 100-year event are based on Table SO-1. Outlet for the Excess Urban Runoff Volume (EURV) to be designed to empty out the EURV in 72 hours. Outlet design is similar to one for the WQCV outlet of an extended detention basin (i.e., perforated plate with a micro-pool) and extends to top of EURV water surface elevation. Recommended Horton's Equation Parameters for CUHP Effective Imperviousness 1 Type C or D Decay Coefficient-- 4) EURV approximates the difference between developed and pre-developed runoff volume. 5) User has opted to add the WQCV to the 100-year detention volume to satisfy local regulations. This is not required per the USDCM. Detention Volumes 2,5 DETENTION VOLUME BY THE FULL SPECTRUM METHOD Maverik Detention Pond 1) Effective imperviousness is based on Figure ND-1 of the Urban Storm Drainage Criteria Manual (USDCM). Area of Watershed (acres) Subwatershed Imperviousness Level of Minimizing Directly Connected Impervious Area (MDCIA) Hydrologic Soil Type Type A Type B Excess Urban Runoff Volume 4 Infiltration (inches per hour) Maximum Allowable Release Rate, cfs 3 0.00 0.50 1.00 1.50 2.00 2.50 0 20 40 60 80 100 Runoff Voume - Inches Percent Total Imperviousness 100-yr Vol Type A Soil 100-yr Vol Type B, C & D Soils EURV Type A Soil EURV Type B Soil EURV Type C/D Soil 100-yr Storage Volume EURV Storage Volume 15001770-UD-Detention_v2.32.xls 11/20/2015, 10:41 AM Survey Area Data: Version 10, Sep 22, 2015 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Apr 22, 2011—Apr 28, 2011 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Hydrologic Soil Group—Larimer County Area, Colorado Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 11/16/2015 Page 2 of 4