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Home My WebLink AboutGUARDIAN SELF STORAGE - PDP190020 - DOCUMENT MARKUPS - ROUND 2 - DRAINAGE REPORTFINAL DRAINAGE REPORT FOR Guardian Storage Fort Collins Prepared For: Guardian Storage Fort Collins 1555 South 76th Street Superior, CO 80027 Kevin Cohen (303) 250-2059 December 2019 Project No. 39737.01 Prepared By: JR Engineering, LLC 2900 South College Avenue, Suite 3D Fort Collins, CO 80525 Fort Collins Utilities Comments PDP Rnd 1 1-7-2020 Matt Simpson Guardian Storage Fort Collins Final Drainage Report iv Engineer’s Certification Block I hereby certify that this Final Drainage Report for Guardian Storage Fort Collins was prepared by me (or under my direct supervision) for JR Engineering, LLC and the owners thereof and meets or exceeds the criteria of the City of Fort Collins Stormwater Design Standards. Rebecca A. Brush, PE Registered Professional Engineer State of Colorado No. 53260 Update certification language to statement from FCSCM: Compliance statement: “I hereby attest that this report for the [preliminary or final] drainage design for the [project name] was prepared by me or under my direct supervision, in accordance with the provisions of the Fort Collins Stormwater Criteria Manual. I understand that the City of Fort Collins does not and will not assume liability for drainage facilities designed by others.” Registered professional engineer must affix their seal with signature and date. JR Response: Addressed per recommendation. Guardian Storage Fort Collins Final Drainage Report 1 GENERAL DESCRIPTION AND LOCATION LOCATION The site is located in the North West Quarter of the South West Quarter of Section 1, Township 6 North, Range 69 West of the 6th Principal Meridian in the City of Fort Collins, Larimer County, Colorado. More specifically, the site is a 1.857 acre property that is currently undeveloped. The site is located adjacent to S. Collage Ave, and Fossil Creek Pkwy. The site will be developed into a commercial self-storage facility. DESCRIPTION OF PROPERTY The Guardian Self Storage site is 1.857 acres at the northeast corner to S. Collage Ave and Fossil Creek Pkwy. The existing site currently has dirt stockpiled on-site. The existing site generally slopes from northwest to southeast with slopes ranging between 0.70% and 25%. The property is generally covered with sparse native grasses. The site currently drains from the northwest corner to the southeast corner to an existing 30”x44” HERCP which outfalls to Fossil Creek, which is located approximately 190 feet south of the site. The site is tributary to the Fossil Creek drainage basin. The Guardian Storage site will be developed in concurrence to Snead Drive directly adjacent to the site along its eastern border as well as open space Tract A with areas of 0.5187 acres and 0.292 acres respectively. FLOODPLAIN SUBMITTAL REQUIREMENTS The site is on FEMA FIRM panel 08069C1000F. The flood map for this location has a status of "not printed". This means that the entire area of the panel is in a single flood zone, so FEMA chose to economize and not create a printable image for this location. The site lies within FEMA Zone X, areas which are determined to be outside the 0.2% annual chance floodplain. The site is not located within a FEMA regulated floodway, but the eastern portion of the site is located within the City of Fort Collins Fossil Creek floodplain and is characterized by the city as “City High Risk – Floodway” as shown in Appendix A, FC Maps – Guardian Self Storage. The City of Fort Collins is in the process of reanalyzing and updating the Fossil Creek floodplain and the BFEs (Base Flood Elevations) for Fossil Creek near the site. The revised BFE at out outfall location was estimated to be 4944.84 and the lowest building finished floor elevation is set at minimum 18” above that at 4946.60. add: "mapping" site. The revised BFE at out outfall location was estimated to be 4944.84 and the lowest building finished Check with BFE on page 7. Please note the names of the adjacent developments. These can be obtained from the County Assessor's webmap JR Response: Addressed per recommendation. JR Response: Addressed per recommendation. Guardian Storage Fort Collins Final Drainage Report 2 DRAINAGE BASINS AND SUB-BASINS MAJOR BASINS AND SUB-BASINS The proposed Guardian Self Storage site is located in the Fossil Creek basin. The Fossil Creek drainage basin extends along the south end of Fort Collins, from the foothills across Interstate 25 past CR 5. It encompasses 32 square miles in the City of Fort Collins and Larimer County. Historically, the basin consisted of agricultural land, but the basin has experienced significant development in the recent past. SUB-BASIN DESCRIPTION Guardian Storage is governed by the City’s Reasonable Use policy, in which the proposed drainage basins will need to follow the generally accepted principle of releasing the 100-year developed condition flow rate at the same location and magnitude as the 2-year pre-development condition flow rate. There are offsite areas that flow across the proposed development site. The existing drainage basins within the site flow to the southeast of the site. EXISTING OFFSITE DRAINAGE BASINS Currently the site collects offsite runoff from 3 locations: the northwest corner, the northeast corner and the southeast corner. The existing offsite land use is developed and is discussed in JR Engineering’s Memorandum Fossil Creek Property Stockpile Permit dated June 8th 2017, see Appendix E. These offsite flows will be collected in inlets and piped through the site to the outfall location, a 30”x42” HERCP in the southeast corner of the site that drains directly to Fossil Creek. The offsite flows will be routed through the site separately from any onsite runoff and will be piped directly to the outfall location, no detention or water quality will be provided for the offsite runoff. Any onsite runoff from the site development and Snead Drive will be collected in curb and gutter or inlets and piped to the proposed sand filter which will provided LID treatment and water quality for onsite runoff only. PROPOSED SUB-BASINS DESCRIPTIONS The proposed Sub-Basins are discussed below. The sub-basin represents basins that are adjacent to the site, as shown in the Appendix D, Drainage Map. "existing" Please note the offsite flow rates (100-yr). Existing? JR Response: Addressed per recommendation. JR Response: Addressed per recommendation. Guardian Storage Fort Collins Final Drainage Report 6 DRAINAGE DESIGN CRITERIA REGULATIONS This report was prepared to meet or exceed the City of Fort Collins stormwater criteria. The City of Fort Collins Stormwater Criteria Manual (dated 2018)(FCSCM) and the Urban Drainage Flood Control District’s (UDFCD) Drainage Criteria Manual (USDCM) Volumes 1, 2 and 3 were referenced as guidelines for this design. MINIMIZATION OF THE DCIA Volume reduction is an important part of the Four Step Process and is fundamental to effective stormwater management. Per City criteria, a minimum of 50 percent of new impervious surface area must be treated by a Low-Impact Development (LID) best management practice (BMP). The proposed LID BMPs will have the effect of slowing runoff through the site lot and increasing infiltration and rainfall interception by encouraging infiltration and careful selection of vegetative cover. The improvements will decrease the runoff coefficient from the site and are expected to have no adverse impact on the timing, quantity, or quality of stormwater runoff. 100% of the new impervious area is treated by the proposed sand filter in the southeast corner of the site as illustrated in the LID/Surface Map is provided in Appendix G. DEVELOPMENT CRITERIA REFERENCE AND CONSTRAINTS The master drainage report for the Fossil Creek Drainage Basin was prepared by ICON Engineering, Inc. April 9tthh, 2002. Guardian Storage falls within element 30 in the SWMM file associated with the master drainage report. The development of the Guardian Storage site must not have a negative impact on downstream discharges, volumes and water surface elevations. The elements directly downstream from the Guardian Storage site are elements 47 and 29 from the master SWMM file. HYDROLOGIC CRITERIA The rational method was performed to calculate the peak runoff rates for each basin. Weighted percent imperviousness and weighted runoff coefficients were calculated for each basin using USDCM Tables 6-4 and 6-5 based on Natural Resources Conservation Service (NRCS) Type B hydrologic soil classification and surface characteristics of each basin. The time of concentration was calculated using FCSCM Equation 5-3 and the intensity was interpolated from Table 3.4-1 in the FCSCM. The City of Fort Collins stormwater management. Per City criteria, a minimum of 50 percent of new impervious surface area 75% (50% LID is if Pavers are used) The rational method was performed to calculate the peak runoff rates for each basin. Weighted percent imperviousness and weighted runoff coefficients were calculated for each basin using USDCM Tables 6-4 and 6-5 based on Natural Resources Conservation Service (NRCS) Type B hydrologic soil classification and surface characteristics of each basin. The time of concentration was calculated using FCSCM The Tc calcs appear to have been done with a different method. Please check the Tc calcs against the FCSCM method. C values and perc. imperv. should come from Fort Collins Stormwater Criteria Manual. From reviewing your calcs, I believe you used the FCSCM method. Please confirm and update text. Volume reduction is an important part of the Four Step Process and is fundamental to effective Please expand discussion of the 4 Step Process for receiving water protection. It is acceptable for this discussion to be concise and short. and surface characteristics of each basin. The time of concentration was calculated using FCSCM JR Response: Addressed per JR Response: Corrected to 75% Recommendation JR Response: Addressed per recommendation. JR Response: Tc calcs have been checked and changed to FCSCM method. Guardian Storage Fort Collins Final Drainage Report 7 area has 2-year, 1-hour rainfall depth of 0.82 inches and a 100-year, 1-hour rainfall depth of 2.86 inches. These depths do account for the 1997 adjusted rainfall depths. HYDRAULIC CRITERIA The ultimate Guardian Self Storage storm drainage system will be designed to convey the minor and major storm events through the property with the proposed inlets, storm sewer pipes, and swales for the flows being calculated by this report. Per the requirements provided by the City of Fort Collins Storm Drainage Design Criteria and Construction Manual, all inlets and storm pipes will be designed to convey the 100-year storm flows. During the major storm event, the developed condition 100-year storm, the accumulated water depth in the sand filter will be held to a maximum level of one-foot below all building finished floor elevations. FLOODPLAIN REGULATIONS COMPLIANCE As previously stated, the eastern portion of the Guardian Self storage site is within the City of Fort Collins Fossil Creek flood plain. The City of Fort Collins is in the process of reanalyzing and updating the Fossil Creek floodplain and the BFEs (Base Flood Elevations) for Fossil Creek near the site. The revised BFE at out outfall location was estimated to be 4945.00 and as such the lowest building finished floor elevation is set at least 18” above that at 4946.60. The portion of the site that is within the floodplain is located within the ineffective flow area of the Fossil Creek floodplain model and a no-rise memo will be completed to show that the proposed development is within the ineffective flow area and will therefore result in no-rise of the BFE. MODIFICATIONS OF CRITERIA Chapter 6, Section 1.1 of the City of Fort Collins Stormwater Criteria Manual states that stormwater detention is required on site. There are four characteristics of the site that make meeting the detention requirements in the Fort Collins Stormwater Criteria Manual not feasible. First, this site has a large amount of offsite runoff being routed through it to Fossil Creek in its current condition. In the proposed condition, the offsite water needs to be collected in pipes and routed through the site and not through a detention pond, creating a complicated stormwater pipe network that limits the space and depth that would be needed for a detention pond. Second, the site is only about 2.15 acres in size but has approximately twelve feet of elevation difference from the northwest corner to the southeast corner of revised BFE at out outfall location was estimated to be 4945.00 and as such the lowest building finished Check with BFE on page 1 For Beat the Peak option (varience from detention), the justification is the BTP analysis results. Hardship justification is not necessary - this can be removed from report. detention is required on site. There are four characteristics of the site that make meeting the detention requirements in the Fort Collins Stormwater Criteria Manual not feasible. First, this site has a large amount of offsite runoff being routed through it to Fossil Creek in its current condition. In the proposed condition, the offsite water needs to be collected in pipes and routed through the site and not through a detention pond, creating a complicated stormwater pipe network that limits the space and depth that would be needed for a detention pond. Second, the site is only about 2.15 acres in size but has approximately twelve feet of elevation difference from the northwest corner to the southeast corner of JR Response: Addressed per Recommendation. Guardian Storage Fort Collins Final Drainage Report 8 the site which creates a significant challenge for grading the site, roadway, and a detention pond to be able to tie out appropriately to the site outfall and boundary. Third, the City of Fort Collins right of way dedicated for the extension of Snead Drive to Fossil Creek Parkway bisects the site. Additional right of way is proposed to be dedicated for the Snead Drive extension which removes additional site area. Lastly, the Snead right of way is also composed of wetland areas that need to be mitigated. The wetland mitigation and replacement takes up more of the already limited site area. It is for these reasons that a variance to the detention requirement is being sought. Due to the site's proximity to Fossil Creek, a "beat the peak" alternative in conjunction with a sand filter sized to treat 100% of the proposed impervious area is the proposed alternative to the detention requirement. BEAT THE PEAK ANALYSIS Per Chapter 6, Section 2.5 of the City of Fort Collins Stormwater Criteria, if a site is nearby to a drainage or water way and the proposed site hydrograph is shown to “beat the peak” stormwater detention may be eliminated from the site. The City of Fort Collins provided the master hydrology model for Fossil Creek. The Guardian Storage site is located within Basin 30 in the SWMM model. Basin 30 was modified per the proposed Guardian Storage site condition within the model. A summary of the results can be seen in Table 1 below. Element 30 (channel) Element 47 (direct flow) Element 29 (channel) From the City Peak (cfs) 451.9 cfs 3488.9 cfs 3430.8 cfs Stage (ft) 0.5' - 7.5' Time (hr/min) 36 min 2hr 47 min 3hr 5 min Revised UD SWMM Peak (cfs) 456 cfs 3489 cfs 3431 cfs Stage (ft) 0.5' - 7.5' Time (hr/min) 36 min 2hr 47 min 3hr 5 min Element 30 contains the proposed site and element 47 and 29 are the next two elements downstream. The full UDSWMM output is located in Appendix F. The was essentially no increase in flow rate to the site which creates a significant challenge for grading the site, roadway, and a detention pond to be able to tie out appropriately to the site outfall and boundary. Third, the City of Fort Collins right of way dedicated for the extension of Snead Drive to Fossil Creek Parkway bisects the site. Additional right of way is proposed to be dedicated for the Snead Drive extension which removes additional site area. Lastly, the Snead right of way is also composed of wetland areas that need to be mitigated. The wetland mitigation and replacement takes up more of the already limited site area. It is for these reasons that a variance to the detention requirement is being sought. JR Response: Addressed per Recommendation. Guardian Storage Fort Collins Final Drainage Report 9 Fossil Creek in downstream elements, basin volumes or basin water surface elevations as a result of the development. DRAINAGE FACILITY DESIGN GENERAL CONCEPT The proposed improvements to the Guardian Storage site will result in developed condition runoff being conveyed around the proposed building and to the east via storm sewer and surface flow. Low-impact development best management practices are proposed to improve the quality of runoff and aid in reducing peak flows. Specifically, a sand filter is proposed on the southeast sides of the site to improve water quality. Runoff from the site is captured in inlets located in the parking lot, the drive aisle to the north of the building, and in Snead Drive. Runoff is conveyed in storm sewers, along curb and gutter, and via surface flow to the proposed sand filter at the south end of the site. Secondly, surface overflow paths have been provided, such that the 100-year storm flows remain at least one foot below the finished floor elevation in a fully clogged inlet condition. WATER QUALITY/ DETENTION FACILITIES The Guardian Self Storage sand filter water–quality treatment facility is located at the southern portion of the site near Snead Drive and Fossil Creek Pkwy. The Urban Drainage UD-BMP spreadsheet version 3.07 was utilized to design and size the proposed sand filter. The sand filter design details can be found in Appendix D. LOW IMPACT DEVELOPMENT A minimum of 50 percent of new impervious surface area is treated by a Low-Impact Development (LID) best management practice (BMP) in accordance with City criteria. The BMPs proposed for the Guardian Storage site are a sand filter for water quality treatment. Of the total 1.73 acres of new impervious area, all 1.73 acres are treated by LIDs (100%). Since more than 75% of the site is treated by LID the minimum threshold of permeable pavers for new parking is not required. An illustrative LID/ Surface Map is provided in Appendix G and the sizing of the LID sand filter is provided in Appendix D. flow to the proposed sand filter at the south end of the site. Secondly, surface overflow paths have been provided, such that the 100-year storm flows remain at least one foot below the finished floor elevation in a fully clogged inlet condition. Please show the overflow location and flow path on the drainage map. Please add: Trib area, % Imperv., WQCV depth (watershed in.), and WQCV volume (CF). A minimum of 50 percent of new impervious surface area is treated by a Low-Impact Development 75% unless using pavers Not needed JR Response: Overflow path and location added to drainage map. JR Response: Addressed per Recommendation. JR Response: Addressed per Recommendation. JR Response: Addressed per Recommendation. Guardian Storage Fort Collins Final Drainage Report 10 CONCLUSIONS COMPLIANCE WITH STANDARDS The hydrologic and water quality calculations were performed using the required methods as outlined in the City of Fort Collins Stormwater Criteria Manual. The proposed drainage improvements meet or exceed the City’s requirements except for the detention requirement in Chapter 6, Section 1.1. A variance request has been submitted in conjunction with this report. This report exhibits that both the storm water systems meet or exceed the requirements set forth in the City of Fort Collins “Storm Drainage Criteria Manual and Construction Standards” and addenda. DRAINAGE CONCEPT The proposed concept for the development of the Guardian Self Storage site involves surface flows and piping of developed conditions flows to a proposed onsite sand filter. LID site enhancements will treat the site runoff at the source before outfall to Fossil Creek. All the offsite flows will be conveyed through the site and directly released at the quality and rate that has historically passed through the site. The existing conditions drainage patterns are maintained in the proposed and future conditions. The proposed improvements will have no adverse impacts on the flow rate, character, or quality of runoff leaving the site. Please note in the report: -Describe the stormwater impact (or lack of) to adjacent properties. -Statement of compliance with Erosion Control Criteria and all Erosion Control Materials will be provided with the Final Drainage Report JR Response: Addressed per Recommendation. JR Response: Noted Subdivision: 0 Project Name: Guardian Storage Fort Collins Location: Fort Collins Project No.: Calculated By: AJ Checked By: AJH Date: 12/6/19 A1 0.68 100% 0.00 0.0% 90% 0.68 90.0% 100% 0.00 0.0% 2% 0.00 0.0% 90.0% B1 0.03 100% 0.03 100.0% 90% 0.00 0.0% 100% 0.00 0.0% 2% 0.00 0.0% 100.0% B2 0.05 100% 0.05 100.0% 90% 0.00 0.0% 100% 0.00 0.0% 2% 0.00 0.0% 100.0% B3 0.04 100% 0.04 100.0% 90% 0.00 0.0% 100% 0.00 0.0% 2% 0.00 0.0% 100.0% B4 0.02 100% 0.02 100.0% 90% 0.00 0.0% 100% 0.00 0.0% 2% 0.00 0.0% 100.0% B5 0.09 100% 0.06 60.7% 90% 0.00 0.0% 100% 0.00 0.0% 2% 0.04 0.8% 61.5% C1 0.14 100% 0.11 77.0% 90% 0.00 0.0% 100% 0.002 1.5% 2% 0.03 0.4% 79.0% D1 0.30 100% 0.00 0.0% 90% 0.00 0.0% 100% 0.00 0.0% 2% 0.30 2.0% 2.0% E1 0.30 100% 0.18 57.8% 90% 0.00 0.0% 100% 0.03 11.0% 2% 0.09 0.6% 69.5% E2 0.26 100% 0.17 63.4% 90% 0.00 0.0% 100% 0.05 17.7% 2% 0.05 0.4% 81.5% F1 0.10 100% 0.09 84.5% 90% 0.00 0.0% 100% 0.02 15.5% 2% 0.00 0.0% 100.0% F2 0.26 100% 0.26 100.0% 90% 0.00 0.0% 100% 0.00 0.0% 2% 0.00 0.0% 100.0% G1 0.28 100% 0.00 0.0% 90% 0.00 0.0% 100% 0.00 0.0% 2% 0.28 2.0% 2.0% TOTAL 2.57 67.0% OSA 0.29 100% 0.18 61.3% 90% 0.00 0.0% 100% 0.04 12.3% 2% 0.08 0.5% 74.2% TOTAL 5.43 4.0% Weighted % Imp. % Imp. Area (ac) 39737.01 COMPOSITE % IMPERVIOUS CALCULATIONS Weighted % Imp. Basins Total Weighted % Basin ID Total Area (ac) % Imp. Area (ac) Imp. Lawns % Imp. Area (ac) Weighted % Imp. Paved Roads/Ashphalt Roofs CONCRETE WALK % Imp. Area (ac) Weighted % Imp. X:\3970000.all\3973701\Excel\Drainage\3973701 Drainage_Calcs_Template_v2.07.xlsm Page 1 of 1 12/6/2019 Please update 'Total' row, or remove JR Response: Addressed per Recommendation. Subdivision: 0 Project Name: Guardian Storage Fort Collins Location: Fort Collins Project No.: Calculated By: AJ Checked By: AJH Date: 12/6/19 FINAL BASIN D.A. Hydrologic Impervious C2 C 100 L S o t i L t S t K VEL. t t COMP. t c TOTAL Urbanized t c t c ID (ac) Soils Group (%) (ft) (%) (min) (ft) (%) (ft/s) (min) (min) LENGTH (ft) (min) (min) A1 0.68 B 90% 0.95 1.00 50 1.0% 1.9 180 1.0% 20.0 2.0 1.5 3.4 230.0 12.1 5.0 B1 0.03 B 100% 0.95 1.00 7 1.0% 0.7 35 1.5% 20.0 2.4 0.2 1.0 42.0 9.2 5.0 B2 0.05 B 100% 0.95 1.00 7 1.0% 0.7 35 1.5% 20.0 2.4 0.2 1.0 42.0 9.2 5.0 B3 0.04 B 100% 0.95 1.00 7 1.0% 0.7 35 1.5% 20.0 2.4 0.2 1.0 42.0 9.2 5.0 B4 0.02 B 100% 0.95 1.00 7 1.0% 0.7 35 1.5% 20.0 2.4 0.2 1.0 42.0 9.2 5.0 B5 0.09 B 61% 0.64 0.79 7 1.0% 2.2 35 1.5% 20.0 2.4 0.2 2.5 42.0 15.8 5.0 C1 0.14 B 79% 0.78 0.97 20 2.0% 2.1 304 3.3% 20.0 3.6 1.4 3.5 324.0 14.0 5.0 D1 0.30 B 2% 0.15 0.19 5 2.0% 3.1 95 3.5% 15.0 2.8 0.6 3.6 100.0 26.6 5.0 E1 0.30 B 70% 0.70 0.88 5 2.0% 1.3 228 1.0% 20.0 2.0 1.9 3.2 233.5 16.2 5.0 E2 0.26 B 81% 0.80 1.00 5 2.0% 1.0 251 1.0% 20.0 2.0 2.1 3.0 256.1 14.2 5.0 F1 0.10 B 100% 0.95 1.00 15 2.0% 0.8 58 1.0% 20.0 2.0 0.5 1.3 73.0 9.4 5.0 F2 0.26 B 100% 0.95 1.00 15 2.0% 0.8 80 2.3% 20.0 3.0 0.4 1.3 95.0 9.4 5.0 G1 0.28 B 2% 0.15 0.19 15 2.0% 5.3 30 20.0% 15.0 6.7 0.1 5.4 45.0 25.8 5.0 OSA 0.29 B 74% 0.74 0.92 25.39 5.0% 1.9 313 3.0% 20.0 3.5 1.5 3.4 338.3 14.9 5.0 NOTES: DATA (URBANIZED BASINS) INITIAL/OVERLAND (Ti) TRAVEL TIME (Tt) STANDARD FORM SF-2 TIME OF CONCENTRATION SUB-BASIN tc CHECK 39737.01 X:\3970000.all\3973701\Excel\Drainage\3973701 Drainage_Calcs_Template_v2.07.xlsm Page 1 of 2 12/6/2019 These equations are not from the updated FCSCM. Please see Ch 5. (Hydrology) Section 3.3 and update to the Fort Collins time of concentration equations. https://www.fcgov.com/utilities/business/builders-and-developers/development- forms-guidelines-regulations/stormwater-criteria JR Response: Equations updated per Ch5 of the FCSCM. Project Name: Guardian Storage Fort Collins Subdivision: 0 Project No.: Location: Fort Collins Calculated By: AJ Design Storm: Checked By: AJH Date: TRAVEL TIME STREET Design Point Basin ID Area (ac) Runoff Coeff. tc (min) C*A (ac) I (in/hr) Q (cfs) tc (min) C*A (ac) I (in/hr) Q (cfs) Qstreet (cfs) C*A (ac) Slope (%) Qpipe (cfs) C*A (ac) Slope (%) Pipe Size (inches) Length (ft) Velocity (fps) tt (min) REMARKS Sheet Flow runoff from north 8.7 Offsite Flow from previous report OS1 Basin J from Fossil Creek Drainage Memo Type R Sump Inlet 1 B5 0.09 0.79 5.0 0.08 9.95 0.8 9.5 Piped flow from north 34.5 Add piped flow from North 1.1 DP 6 from Fossil Creek Drainage Memo 44.0 Piped to DP 2 Runoff from north inlet 19.5 MH 2 Basin K from Fossil Creek Drainage Memo 63.5 Piped to DP 2 Piped flow from FCLWSD 21.5 Piped to DP 4.1 3 Basin M from Fossil Creek Drainage Memo Runoff from east side of Snead Drive 15.3 Proposed on-grade inlet 4 DP 12 from Fossil Creek Drainage Memo 3.3 12.0 Collected flow to DP 4.1, bypass flow to DP 14 4.1 33.5 Piped to DP 6 Runoff from west side of Snead Drive 15.3 5 DP 12 from Fossil Creek Drainage Memo Replaces on-grade inlet 5 C1 0.14 0.97 5.0 0.14 9.95 1.4 16.6 4.6 12.0 Collected flow to DP 6, bypass flow to DP 15 MH 6 45.5 Piped to DP 17 7 A1 0.68 1.00 5.0 0.68 9.95 6.8 Roof Drain piped north Area Inlet B4 0.02 1.00 5.0 0.02 9.95 0.2 5.0 0.70 9.95 7.0 Piped to DP 8.1 Area Inlet 8 B3 0.04 1.00 5.0 0.04 9.95 0.4 Piped to DP 8.1 8.1 5.0 0.74 9.95 7.4 Piped to DP 9.1 Area Inlet 9 B2 0.05 1.00 5.0 0.05 9.95 0.5 Piped to DP 9.1 9.1 5.0 0.79 9.95 7.9 Piped to DP 10.1 Area Inlet 10 B1 0.03 1.00 5.0 0.03 9.95 0.3 Piped to DP 10.1 Project Name: Guardian Storage Fort Collins Subdivision: 0 Project No.: Location: Fort Collins Calculated By: AJ Design Storm: Checked By: AJH Date: TRAVEL TIME STREET Design Point Basin ID Area (ac) Runoff Coeff. tc (min) C*A (ac) I (in/hr) Q (cfs) tc (min) C*A (ac) I (in/hr) Q (cfs) Qstreet (cfs) C*A (ac) Slope (%) Qpipe (cfs) C*A (ac) Slope (%) Pipe Size (inches) Length (ft) Velocity (fps) tt (min) REMARKS STORM DRAINAGE SYSTEM DESIGN STANDARD FORM SF-3 (RATIONAL METHOD PROCEDURE) 39737.01 PIPE 100-Year DIRECT RUNOFF TOTAL RUNOFF 12/6/19 STREET 11.1 5.0 0.92 9.95 9.2 Piped to Sand Filter DP 16 Curb Cut 12 F2 0.26 1.00 5.0 0.26 9.95 2.6 to Sand Filter Dp 16 Area Inlets 13 D1 0.30 0.19 5.0 0.06 9.95 0.6 Piped to DP 14.1 Sump Inlet 14 E2 0.26 1.00 5.0 0.26 9.95 2.6 5.9 Piped to DP 14.1 14.1 5.0 0.32 9.95 6.5 Piped to DP 15.1 Runoff from west Fossil Creek PKWY 33.4 Offsite Flow from previous report OS2 DP 14 from Fossil Creek Drainage Memo Type R On-grade Inlet OS3 OSA 0.29 0.92 5.0 0.27 9.95 2.7 0 0 0.6 2.7 0.3 Collected flow to DP 17, Bypass flow to DP 15 Sump Inlet 15 E1 0.30 0.88 5.0 0.27 9.95 2.7 5.0 0.27 9.95 7.3 Piped to DP 15.1 15.1 5.0 0.59 9.95 13.8 Piped to Sand Filter DP 16 16 G1 0.28 0.19 5.0 0.05 9.95 0.5 23.4 23.4 Sand Filter, discharge to DP 17 17 71.6 Piped to Outfall Notes: Street and Pipe C*A values are determined by Q/i using the catchment's intensity value. X:\3970000.all\3973701\Excel\Drainage\3973701 Drainage_Calcs_Template_v2.07.xlsm Page 2 of 2 12/6/2019 23.4 23.4 Sheet 1 of 2 Designer: Company: Date: Project: Location: 1. Basin Storage Volume A) Effective Imperviousness of Tributary Area, Ia Ia = 74.2 % (100% if all paved and roofed areas upstream of sand filter) B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 0.742 C) Water Quality Capture Volume (WQCV) Based on 12-hour Drain Time WQCV = 0.24 watershed inches WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i) D) Contributing Watershed Area (including sand filter area) Area = 101,786 sq ft E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = cu ft VWQCV = WQCV / 12 * Area F) For Watersheds Outside of the Denver Region, Depth of d6 = 0.43 in Average Runoff Producing Storm G) For Watersheds Outside of the Denver Region, VWQCV OTHER = 2,004 cu ft Water Quality Capture Volume (WQCV) Design Volume H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER = cu ft (Only if a different WQCV Design Volume is desired) 2. Basin Geometry A) WQCV Depth DWQCV = 1.8 ft B) Sand Filter Side Slopes (Horizontal distance per unit vertical, Z = 5.00 ft / ft 4:1 or flatter preferred). Use "0" if sand filter has vertical walls. C) Minimum Filter Area (Flat Surface Area) AMin = 944 sq ft D) Actual Filter Area AActual = 1146 sq ft E) Volume Provided VT = 2006 cu ft 3. Filter Material 4. Underdrain System A) Are underdrains provided? 1 B) Underdrain system orifice diameter for 12 hour drain time i) Distance From Lowest Elevation of the Storage y= 0.8 ft Volume to the Center of the Orifice ii) Volume to Drain in 12 Hours Vol12 = 2,004 cu ft iii) Orifice Diameter, 3/8" Minimum DO = 1 1/4 in Guardian Storage Fort Collins, CO Design Procedure Form: Sand Filter (SF) AJH JR Engineering December 6, 2019 UD-BMP (Version 3.07, March 2018) Choose One Choose One 18" CDOT Class B or C Filter Material Other (Explain): YES NO UD-BMP_v3.07.xlsm, SF 12/6/2019, 2:33 PM Imperv. calc table shows 67%. Please confirm,update or explain. Which subbasins drain here? Please check against the subbasins table. FYI, Fort Collins does not require an orifice on the sand filter outlet. The Fort Collins detail, D-55, can be found here: https://www.fcgov.com/utilities/business/builders-and-developers/development-forms- guidelines-regulations/stormwater-criteria Sheet 2 of 2 Designer: Company: Date: Project: Location: 5. Impermeable Geomembrane Liner and Geotextile Separator Fabric A) Is an impermeable liner provided due to proximity of structures or groundwater contamination? PROVIDE A 30 MIL (MIN) PVC GEOMEMBRANE PER TABLE SF-4 WITH SEPARATOR FABRIC (PER TABLE SF-3) ABOVE IT. PROVIDE SEPARATOR FABRIC BELOW THE GEOMEMBRANE AS WELL IF SUBGRADE IS ANGULAR OR COULD OTHERWISE PUNCTURE THE GEOMEMBRANE. 6. Inlet / Outlet Works A) Describe the type of energy dissipation at inlet points and means of conveying flows in excess of the WQCV through the outlet Notes: Design Procedure Form: Sand Filter (SF) AJH JR Engineering December 6, 2019 Guardian Storage Fort Collins, CO Flows In excess of the WQCV will enter the outlet structure box through an overflow grate and flow to the outfall unrestricted. Choose One YES NO UD-BMP_v3.07.xlsm, SF 12/6/2019, 2:33 PM 7200 South Alton Way, Suite C400 Centennial, CO80112 303-740-9393 Fax 303-921-7320 130 East Kiowa Street, Suite 400 Colorado Springs, CO80903 719-593-2593 Fax 303-921-7320 2900 South College Avenue, Suite 3D Fort Collins, CO80525 970-491-9888 Fax 303-921-7320 MEMORANDUM JR Engineering, LLC has completed an existing condition preliminary storm drainage evaluation for the Fossil Creek Stockpile Permit application. The following memorandum and calculations summarizes the findings discovered for the existing condition 100 year storm drainage tributary to the site in order to quantify and route the existing runoff through the site during the stockpile period. JR investigated this site’s contributing runoff within the fossil creek area using a combination of approved final drainage reports, drainage map, and existing storm basin calculations. The basins and the runoff associated with each are shown in Appendix A. All basin calculations can be found in Appendix B including the inlet calculations at design points 4, 5, 6, and 16. The seemingly abandoned drainage ditch and 16’’ CMP StormCAD model results are also found in Appendix B. All inlet calculations were performed within UD-Inlet Version 4.05. For the purpose of this memorandum, only the 100 year storm event flows will be considered. Upon reading the “Master Drainage Report for Arbor Plaza and Final Drainage Report for Arbor Plaza Phase 1” prepared by Drexel, Barrell & Co. dated January 16, 1986, the runoff from this basin is routed underneath South College Avenue to Mail Creek. It should also be noted that according to the “Hydrologic and Hydraulic Report – South Transit Center” by HDR dated May 2011, the runoff from the South Transit Center is captured in a detention pond and released along Fossil Boulevard towards Fossil Creek. For the above mentioned reasons, the runoff from these two northwesterly sites does not end up at the Fossil Creek Stockpile Site. Basin Description Basin A: Basin A is characterized by approximately 9.82 acres of developed commercial land used for the Spradley Barr Dealership. Runoff from this basin was referenced from the “Final Drainage and Erosion Control Study for the Spradley Barr Dealership Fort Collins, Colorado” by The Sear-Brown Group dated December 8, 1997. During the 100 year storm event, the runoff ends up in a detention pond located in the southeast portion of the site where 2.29cfs is released in an inlet at Design Point 1a(DP1a) and routed east across college to the existing trapezoidal irrigation ditch. There is an additional 11.84cfs that is released into the South College Avenue curb and gutter at DP1b. To: Mr. Shane Boyle From: Tim Halopoff, PE Date: June 8, 2017 Subject: Fossil Creek Property Stockpile Permit (Drainage Analysis) final drainage reports, drainage map, and existing storm basin calculations. The basins and the runoff associated with each are shown in Appendix A. All basin calculations can be found in Appendix B Please provide JR Response: Appendix B of memorandum now provided in appendicies. !), & &') &##!%( &#&'& !), % !%' ) )' ()+)' )!#!), ) )&'$+)' )!#!), ) '"( ')!&% ) '! % !%' ) %*!'&%$%)# #%%' ) ) %% '*$&"(#!!) *"('!% )$%$)+ %&( *" %& This is great. Thank you! JR Response: Noted Fort Collins requires 120% of the WQCV. See FCSCM, Ch 7, section 5.4 for more information JR Response: Revised calculations are 1,956 cu ft required X1.2 = 2292cu ft provided JR Response: OSA area was included in calculation. Revised to 67% JR Response: Revised to 111,949 which is the area of all on site subbasins. JR Response: Noted How is the flow rate at DP 16 calculated? When I add up the inflows at DP 16, I end up with 25.6 cfs. 71.6 How is the flow rate at DP 17 calculated? Where did flow from OS2 go? JR Response: DP16+DP6 +DPOS3+DPOS2 JR Response: DP11.1+DP15.1 +DP16 direct runoff+DP12 JR Response: Calculation error was found and inconsistancies have been corrected. 10.1 5.0 0.82 9.95 8.2 Piped to DP 11.1 Sump Inlet 11 F1 0.10 1.00 5.0 0.10 9.95 1.0 Piped to DP 11.1 STORM DRAINAGE SYSTEM DESIGN STANDARD FORM SF-3 (RATIONAL METHOD PROCEDURE) 39737.01 PIPE 100-Year DIRECT RUNOFF TOTAL RUNOFF 12/6/19 STREET X:\3970000.all\3973701\Excel\Drainage\3973701 Drainage_Calcs_Template_v2.07.xlsm Page 1 of 2 12/6/2019 Does the flow at DP 6 account for the offsite flows and flows at DP 2? JR Response: Flow at DP6 accounts for offsite flows coptured in inlets at DP5 and DP 4 as well as piped flow from FCLWSD(DP3)