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Home My WebLink About613 S MELDRUM ST CARRIAGE HOUSE - FDP200028 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT LOCATED IN OLD TOWN PHONE: 970-773-0610 BOX 2211 EMAIL: Les@LesCrawfordPE.com FORT COLLINS, CO 80522 WEB: www.LesCrawfordPE.com November 2, 2020 Matt Simpson [via email: MASimpson@fcgov.com] Stormwater/Utility Development Review 700 Wood Street PO Box 580 Fort Collins, CO 80522 RE: Drainage Memo for 613 South Meldrum Street – single-family residence + Carriage House Building Permit _____________ Dear Matt, I am pleased to submit for your review and approval, this Final Drainage Memo for the Single Family Residential Redevelopment of 613 South Meldrum Street (Lot 13, Block 86, FTC) in Old Town Fort Collins. I certify that this report for the drainage design was prepared in accordance with the criteria in the City of Fort Collins Storm Drainage Manual and the Drainage Information for Residential Permit Applications Memo dated 10/2015. I appreciate your time and consideration in reviewing this submittal. Please call if you have any questions. Respectfully, Les Crawford PE Colorado # 31480 LOCATED IN OLD TOWN PHONE: 970-773-0610 BOX 2211 EMAIL: Les@LesCrawfordPE.com FORT COLLINS, CO 80522 WEB: www.LesCrawfordPE.com LOCATION AND SITE DESCRIPTION This project is located at 613 S Meldrum Street approximately 1,600+ feet west of South College Avenue and approximately 700 feet south of West Mulberry Street in Old Town Fort Collins. The existing lot is 9,500 square feet with a small single-family residence and a garage in the rear yard. The existing grading is classic Type ‘A’ lot grading with the lot draining to the street in the front. The gravel alley in the rear catches only minute adjacent areas. Ground slopes are between 1 and 2% in the area with the street gutter averaging 2.5% to the north. The public alley suffers from rutting and minor puddling but does adequately drain to the north at an overall slope of 2.5%+/-. Both public ways ultimately drain to the existing storm inlet at the southwest corner of South Meldrum Street and East Myrtle Street. Per the City of Fort Collins Floodplain mapping and FEMA Map Panel Number: 08069C0979H Dated 5/2/2012, this project is not within any mapped flood hazard area. PROPOSED PROJECT The proposed construction will remove the existing garage and its foundation. Then the construction of a two-story 1,577 square foot carriage house. Final grading will perpetuate the Type ‘A’ lot grading of the neighborhood with the high point being near the alley but with the adjacent driveway sloping away from the new carriage house towards the alley. Downspouts on both existing and proposed structures will direct roof runoff to the adjacent side yard swales. The swales are graded at 1 to 2% to the street. No runoff from this site is captured by the Arthur Ditch infrastructure. The addition of 3,292 square feet requires a Drainage Memo or Report and a Grading Plan by a Professional Engineer. However, the added hard surface is less than 5,000 square feet so the project qualifies for an Exception to the Water Quality and Water Quantity Requirements. In addition.this site’s ‘standard water quality’ requirement is already provided for in the City’s Udall Natural Area water treatment facility. Permeable Pavers or flagstone are proposed wherever practical. A single-family house plus one Carriage House does not require the addition of LID analysis. Computation of the percentage of hard surface found it to be 57% after construction. No additional storm drainage requirements apply to this project. No adverse effects are expected because of this proposed project. LOCATED IN OLD TOWN PHONE: 970-773-0610 BOX 2211 EMAIL: Les@LesCrawfordPE.com FORT COLLINS, CO 80522 WEB: www.LesCrawfordPE.com DRAINAGE CALCULATIONS FOR 613 S Meldrum Street Fort Collins, Colorado NEW HARD SURFACE CALCULATION EXISTING PROPOSED Front Walk 74 SF Front Walk 74 SF House 1,047 SF House 1,047 SF Garage 340 SF Decks 287 SF Garage Walk 30 SF Rear Deck 245 SF Carriage House 1,577 SF Side Deck 42 SF Light Wells 40 SF Front Porch 142 SF Pavers/Flagstone 2045 SF Concrete Patio 387 SF TOTAL 2,165 SF TOTAL 5,457 SF PROPOSED - EXISTING = 3,292 SF of new Impervious Surface LOCATED IN OLD TOWN PHONE: 970-773-0610 BOX 2211 EMAIL: Les@LesCrawfordPE.com FORT COLLINS, CO 80522 WEB: www.LesCrawfordPE.com WATER QUALITY AND WATER QUANTITY DETENTION EXCEPTION 2,377 SF of New Hard Surface is less than the 5.000 SF allowed. Therefore the exception is allowed. LOCATED IN OLD TOWN PHONE: 970-773-0610 BOX 2211 EMAIL: Les@LesCrawfordPE.com FORT COLLINS, CO 80522 WEB: www.LesCrawfordPE.com PERCENT IMPERVIOUS CALCULATION 613 S Meldrum Street Fort Collins, Colorado IMPERVIOUS SURFACE TOTAL PARCEL Front Walk 74 SF House 1,047 SF Lot Area 9,500 SF Decks 287 SF SF Carriage House 1,577 SF Light Wells 40 SF Pavers/Flagstone 2045 SF Concrete Patio 387 SF Front Walk 74 SF House 1,047 SF TOTAL 5,457 SF TOTAL 9,500 SF PERCENT IMPERVIOUS SURFACE 57% USGS The National Map: Orthoimagery. Data refreshed October, 2020. National Flood Hazard Layer FIRMette 0 500 1,000 1,500 2,000250 Feet Ü SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT SPECIAL FLOOD HAZARD AREAS Without Base Flood Elevation (BFE) Zone A, V, A99 With BFE or DepthZone AE, AO, AH, VE, AR Regulatory Floodway 0.2% Annual Chance Flood Hazard, Areas of 1% annual chance flood with average depth less than one foot or with drainage areas of less than one square mileZone X Future Conditions 1% Annual Chance Flood HazardZone X Area with Reduced Flood Risk due to Levee. See Notes.Zone X Area with Flood Risk due to LeveeZone D NO SCREEN Area of Minimal Flood Hazard Zone X Area of Undetermined Flood HazardZone 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 map complies with FEMA's standards for the use of digital flood maps if it is not void as described below. The basemap shown complies with FEMA's basemap accuracy standards The flood hazard information is derived directly from the authoritative NFHL web services provided by FEMA. This map was exported on 11/1/2020 at 1:00 AM and does not reflect changes or amendments subsequent to this date and time. The NFHL and effective information may change or become superseded by new data over time. This map image is void if the one or more of the following map elements do not appear: basemap imagery, flood zone labels, legend, scale bar, map creation date, community identifiers, FIRM panel number, and FIRM effective date. Map images for unmapped and unmodernized areas cannot be used for regulatory purposes. Legend OTHER AREAS OF FLOOD HAZARD OTHER AREAS GENERAL STRUCTURES OTHER FEATURES MAP PANELS 8 B 20.2 The pin displayed on the map is an approximate point selected by the user and does not represent an authoritative property location. 1:6,000 105°5'17"W 40°35'N 105°4'40"W 40°34'33"N 613 SOUTH MELDRUM STREETFORT COLLINS, COLORADONOVEMBER 2020PALOMOCARRIAGEHOUSECOLORADO * KANSAS * MONTANA * NEBRASKA NORTH DAKOTA * OKLAHOMA * UTAH * WYOMING 242 LINDEN ST FORT COLLINS CO Les @LesCrawfordPE.com (970) 773-0610 Les Crawford PE SITE DEVELOPMENT SOLUTIONS NDRAINAGEPLAN