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Home My WebLink AboutSUNSHINE HOUSE AT BUCKING HORSE - FDP190016 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTFORT COLLINS: 301 North Howes Street, Suite 100, 80521 | 970.221.4158 GREELEY: 820 8th Street, 80631 | 970.395.9880 | WEB: www.northernengineering.com July 17, 2019 City of Fort Collins - Stormwater 700 Wood Street Fort Collins, Colorado 80524 RE: Bucking Horse Filing Two - Major Amendment Fort Collins, Colorado Dear Staff: Bucking Horse Filing Two - Major Amendment (Sunshine House) is a proposal to change the previously approved working farm to a daycare facility. The revised project will include a revised building footprint using slab-on-grade construction. Updated flatwork for the building’s new use will be provided and the existing concrete parking lot will be expanded slightly to add approximately six (6) parking spaces. Drainage Patterns The proposed site improvements will not alter the existing designed drainage patterns that were approved with the original project. Drainage in the parking lot will generally flow to a series of inlets in the middle of the lot and will be conveyed to Pond 215 via the existing storm drain. Runoff from the building and playground will drain to Pond 215 via sheet flow or via a series of area drains and swales. Site Imperviousness The previously approved impervious area of the site was 43,135 square feet. The proposed impervious area of the Major Amendment is 42,574 square feet. This results in a net decrease of 561 square feet of impervious area. Detention and Water Quality The reduction in overall imperviousness noted above indicates that the detention volume originally provided in Pond 215 will continue to be adequate and that no additional onsite detention will be required. The decrease in impervious area also ensures that the water quality volume provided in Pond 215 will also be able to serve the updated project. Low Impact Development (LID) Since the approval of Bucking Horse Filing Two, the City has adopted Low Impact Development (LID) requirements that specify 50% of all newly added impervious areas receive water quality treatment from a LID facility. Since the parking area for this project is existing, only the building roof and new flatwork require LID treatment. These areas are approximately 22,200 sf. Discussions with staff have acknowledged that the parking area is the area with the highest pollutant loads and the highest priority for LID treatment. With that in mind, rain gardens have been added to the center islands that will treat approximately 17,014 sf of the parking area, which is 76% of the new impervious area that has been added, which meets the City LID Requirement. FORT COLLINS: 301 North Howes Street, Suite 100, 80521 | 970.221.4158 GREELEY: 820 8th Street, 80631 | 970.395.9880 | WEB: www.northernengineering.com Other areas of the site will not receive LID treatment from a specific LID facility, but additional treatment will occur. In particular, the roof downspouts will discharge into landscaped swales that will allow for the settling of particulates prior to entering the storm drain system. Also, paved areas in the playground area will sheet flow across large, flat grass areas which will allow for treatment of stormwater runoff from those areas. Erosion and Sediment Control During construction, the Contractor will follow the appropriate and applicable City of Fort Collins standards for erosion and sediment control. This project disturbs more than 10,000 sf and is contained in the originally approved Erosion Control Report. No changes to that report are needed as a result of the changes proposed with this Major Amendment. Post construction water quality and erosion control will be achieved by a fully established and stabilized site. All areas disturbed during construction will receive permanent hardscape, landscape, or building structure. Floodplains This project falls within the FEMA 500-yr floodplain (Zone X-shaded) for the Poudre River as shown on Panel 0992G of Floodplain Map 08069C0992G (Revised May 2, 2012). Per City Code Section 10-81(a), a Childcare facility would not normally be allowed within this zone since it is considered a critical care facility; however, a variance was granted by the City Water Board on January 17, 2019 acknowledging that the proposed building is located several feet above the existing 500-yr floodplain and that there is minimal risk of the building being located within any future floodplain revisions. FORT COLLINS: 301 North Howes Street, Suite 100, 80521 | 970.221.4158 GREELEY: 820 8th Street, 80631 | 970.395.9880 | WEB: www.northernengineering.com As a part of the variance approval, the Water Board included the following conditions: 1. The lowest floor and all HVAC, electrical, and mechanical shall be elevated to 4893.0 feet (NAVD 88) or higher. A FEMA elevation certificate shall be submitted and approved prior to issuance of the Certificate of Occupancy. 2. An Emergency Response and Preparedness Plan that conforms with the minimums outlined in the applicant’s variance application and such plan will be finalized and approved by staff from Office of Emergency Management and Floodplain Administration prior to obtaining a Certificate of Occupancy. The plan must be submitted to OEM for final review a minimum of 60 days prior to anticipated CO. 3. An annual update of the Emergency Response and Preparedness Plan will be required in perpetuity that the building is operated as a daycare and remains mapped in the Shaded Zone X on the FEMA Flood Insurance Map. The Plan Update must be submitted to the City of Fort Collins Stormwater Department during the first quarter of each calendar year. 4. A deed restriction is placed on the property to indicate the variance approval and conditions including the requirements related to notification and evacuation in the Emergency Response and Preparedness Plan and the requirement for annual recertification. If in the future, the property is mapped out of the Shaded Zone X area on the FEMA Flood Insurance Rate Map, the deed restriction may be removed. The deed restriction must be completed prior to CO. 5. Written notification shall be given to parents of all children enrolled in the day care facility notifying them of the floodplain variance approval and of the notification and evacuation procedures. The written notice shall be available prior to CO. 6. The property owner will include the requirements of the Emergency Response and Preparedness Plan and all other conditions of the variance into the lease agreement with Sunshine House and any future daycare providers. This shall be completed prior to CO. 7. The maximum number of children will be 176. The capacity of the facility will not be further expanded in the future without seeking an additional variance request. 8. The building shall not be converted to a different type of critical facility in the future (Ex. Daycare converted to group home or nursing home, etc.). 9. Conditions 2-8 are revoked if, in the future, the property is mapped out of the Shaded Zone X area on the FEMA Flood Insurance Rate Map. FORT COLLINS: 301 North Howes Street, Suite 100, 80521 | 970.221.4158 GREELEY: 820 8th Street, 80631 | 970.395.9880 | WEB: www.northernengineering.com Conformance with Water Board Variance The proposed grading design elevates that finished floor above the minimum required elevation of 4893.00. All HVAC equipment shall be elevated to meet this elevation as well. The table below summarizes the existing base flood elevation and proposed design elevations. Please refer to the approved grading plan for additional information. Conclusions The proposed grading concept closely matches the originally approved drainage patterns and decreases overall site imperviousness thereby negating the need for any additional detention or water quality volumes. The project meets the city requirements for Low Impact Development treatment. Additionally, all conditions related to the design that were required from the approved Water Board variance have been met. Therefore, it is my professional opinion that the Bucking Horse Filing Two Major Amendment (Sunshine House) satisfies all applicable stormwater criteria and will effectively limit potential damage associated with its stormwater runoff. Please do not hesitate to contact me if you have questions or require additional information. Sincerely, Andy Reese Benjamin Ruch, PE Project Manager Project Engineer 500-yr Poudre River Base Flood Elevation 4888.69 Minimum Finished Floor Elevation 4893.00 Minimum HVAC Elevation 4893.00 X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X 4 20 SF CLASSROOM 9 HALL 11 1149 SF BARN 12 6" 114 SF OFFICE 15 115 SF OFFICE 16 WOMENS 17 MENS 18 X X X X X X X X X X X X X X X X MILES HOUSE AVENUE RAIN GARDEN REQUIRED VOLUME: 567 CU. FT. PROVIDED VOLUME: 588 CU. FT. TREATMENT AREA: 17,014 SF NEW IMPERVIOUS AREA 22,220 SF BUCKING HORSE FILING TWO - MAJOR AMENDMENT SHEET NO: D:\PROJECTS\687-007\DWG\DRNG\687-007_LID.DWG 301 N. Howes Street, Suite 100 Fort Collins, Colorado 80521 E NGINEER ING N O R T H E RN PHONE: 970.221.4158 www.northernengineering.com DRAWING REFERENCE: LID TREATMENT EXHIBIT B. Ruch 1 in = 40 ft July 17, 2019 LID-1 DRAWN BY: SCALE: ISSUED: ( IN FEET ) 0 1 INCH = 40 FEET 40 40 LEGEND NEW IMPERVIOUS AREA RAIN GARDEN AREA RAIN GARDEN TREATMENT AREA BUCKING HORSE FILING TWO - MAJOR AMENDMENT ONSITE LID TREATMENT NEW IMPERVIOUS AREAS 22,200 SF RAIN GARDEN TREATMENT AREA 17014 SF TREATMENT AREA PERCENTAGE 76.6% Sheet 1 of 2 Designer: Company: Date: Project: Location: 1. Basin Storage Volume A) Effective Imperviousness of Tributary Area, Ia Ia = 100.0 % (100% if all paved and roofed areas upstream of rain garden) B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 1.000 C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.40 watershed inches (WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i) D) Contributing Watershed Area (including rain garden area) Area = 17,014 sq ft E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = 567 cu ft Vol = (WQCV / 12) * Area F) For Watersheds Outside of the Denver Region, Depth of d6 = in Average Runoff Producing Storm G) For Watersheds Outside of the Denver Region, VWQCV OTHER = 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 (12-inch maximum) DWQCV = 12 in B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 0.00 ft / ft (Use "0" if rain garden has vertical walls) C) Mimimum Flat Surface Area AMin = 340 sq ft D) Actual Flat Surface Area AActual = 352 sq ft E) Area at Design Depth (Top Surface Area) ATop = 823 sq ft F) Rain Garden Total Volume VT= 588 cu ft (VT= ((ATop + AActual) / 2) * Depth) 3. Growing Media 4. Underdrain System A) Are underdrains provided? B) Underdrain system orifice diameter for 12 hour drain time i) Distance From Lowest Elevation of the Storage y = ft Volume to the Center of the Orifice ii) Volume to Drain in 12 Hours Vol12 = N/A cu ft iii) Orifice Diameter, 3/8" Minimum DO = N/A in Design Procedure Form: Rain Garden (RG) B. Ruch Northern Engineering February 26, 2019 Bucking Horse Sunshine House (Bucking Horse Filing 2 Major Amendment) Fort Collins, CO UD-BMP (Version 3.06, November 2016) Choose One Choose One 18" Rain Garden Growing Media Other (Explain): YES NO UD-BMP_v3.06_RG WQVol.xlsm, RG 2/26/2019, 1:58 PM 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? 6. Inlet / Outlet Control A) Inlet Control 7. Vegetation 8. Irrigation NO SPRINKLER HEADS ON FLAT SURFACE A) Will the rain garden be irrigated? Notes: Design Procedure Form: Rain Garden (RG) B. Ruch Northern Engineering February 26, 2019 Bucking Horse Sunshine House (Bucking Horse Filing 2 Major Amendment) Fort Collins, CO Choose One Choose One Choose One Sheet Flow- No Energy Dissipation Required Concentrated Flow- Energy Dissipation Provided Plantings Seed (Plan for frequent weed control) Sand Grown or Other High Infiltration Sod Choose One YES NO YES NO UD-BMP_v3.06_RG WQVol.xlsm, RG 2/26/2019, 1:58 PM USGS The National Map: Orthoimagery. Data refreshed October, 2017. National Flood Hazard Layer FIRMette 0 250 500 1,000 1,500 2,000 Feet Ü 105°1'55.33"W 40°33'21.66"N 105°1'17.87"W 40°32'54.32"N SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT HAZARD SPECIAL AREAS FLOOD Without Zone A, V, Base A99 Flood Elevation (BFE) With BFE or Depth Zone AE, AO, AH, VE, AR Regulatory Floodway 0.of 2% 1% Annual annual Chance chance Flood flood with Hazard, average Areas depth areasdrainage of less less than than one one foot square or with mile Zone X Future ChanceAnnual Conditions Flood Hazard 1% Zone X Area Levee.to with See Reduced Notes. Flood Risk due Zone X Area with Flood Risk due to LeveeZone D NO SCREEN Area of Minimal Flood Hazard Zone X Area of Undetermined Flood Hazard Zone D Channel, Culvert, or Storm Sewer Levee, Dike, or Floodwall Cross Sections with 1% Annual Chance 17.5 Water Surface Elevation Coastal Transect Coastal Transect Baseline Profile Baseline Hydrographic Feature Base Flood Elevation Line (BFE) Effective LOMRs Limit of Study Jurisdiction Boundary Digital Data Available No Digital Data Available Unmapped This digital map flood complies maps if with it is FEMA's not void standards as described for the below. use of The accuracy basemap standards shown complies with FEMA's basemap The authoritative flood hazard NFHL information web services is derived provided directly by FEMA. from This the map was reflectnot exported changes on or 2/amendments 22/2019 at 5:subsequent 53:56 PM to and this does date and time. becomeor The superseded NFHL and effective by new data information over time. may change This elementsmap map image do not is appear: void if basemap the one or imagery, more of flood the following zone labels, legend, FIRM panel scale number, bar, map and creation FIRM effective date, community date. Map identifiers,images for unmapped regulatoryfor purposes. and unmodernized areas cannot be used Legend OTHER FLOOD AREAS HAZARD OF OTHER AREAS STRGUECNTUERREASL FEATURES OTHER MAP PANELS 8 1:6,000 B 20.2 The point pin selected displayed by the on the user map and is does an approximate not represent an authoritative property location. 371 SF TRACTOR / EQUIP. STORAGE 19 COW MILKING 20 MILKING PREP 21 JAN. 22 MECH. 23 MILES HOUSE AVENUE X X X X X X X X MILES HOUSE AVENUE ROOFTOP CONCRETE GRAVEL SURFACE AREA (SF) % IMPERV. IMPERV. AREA (SF) 6,478 36,657 0 100% 100% 40% TOTALS 43,135 TOTAL= 43,135 ROOFTOP CONCRETE ASPHALT SURFACE AREA (SF) % IMPERV. IMPERV. AREA (SF) 11,501 31,073 0 100% 100% 100% TOTALS 42,574 TOTAL= 42,574 PREVIOUSLY APPROVED PROPOSED 6,478 11,501 36,657 0 30,898 0 D:\PROJECTS\687-007\DWG\DRNG\687-007_IMPERVIOUS.DWG BUCKING HORSE FILING TWO - MAJOR AMENDMENT FORT COLLINS COLORADO 301 N. Howes Street, Suite 100 Fort Collins, Colorado 80521 E NGINEER ING N O R T H E RN PHONE: 970.221.4158 www.northernengineering.com DESCRIPTION PREVIOUSLY APPROVED VS. PROPOSED IMPERVIOUS AREA DRAWN BY B. RUCH DATE JULY 17, 2019 PROJECT 838-024 SK-C1 SCALE DRAWING 1"=60' ( IN FEET ) 0 1 INCH = 60 FEET 60 60 ASPHALT 0 100% 0 GRAVEL 0 40% 0