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HomeMy WebLinkAboutNEWTON SINGLE-FAMILY DETACHED - BASIC DEVELOPMENT REVIEW - BDR180019 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE RELATED DOCUMENTKai Kleer June 16th, 2018 City Planning Department 0309.18 281 N College City of Fort Collins 80524 RE: 1520 West Vine Drive – Site Drainage and Erosion Control Report Dear Kai, GENERAL INFORMATION The proposed development located at 1520 West Vine Drive includes the construction of a four bedroom single family residence on a large vacant lot. The total structure square footage is 2,593 including the two car garage and will be situated on a 1.44 acre site. Access will be utilized from the existing driveway at 1516 West Vine Drive and onto West Vine Drive. A separate emergency pervious gravel surface access will be constructed adjacent to the existing 1516 West Vine Drive and will access onto West Vine Drive. SITE DRAINAGE The site is located just north of West Vine Drive and slopes gradually less than 0.33% to the southeast towards West Vine Drive. Due to the small footprint of the proposed structure and driveway that are located on 1.44 acres, runoff is expected to be very minimal. There are no proposed storm sewer or detention pond designed for this site. Drainage is likely to infiltrate into the soil or gradually migrate to West Vine Drive and very slowly drain to the east. As shown in the attachment, the Q100 pre-development runoff from the site is 0.93 cfs versus the Q100 post development runoff of 1.79 cfs. The additional runoff pre-development versus post- development is 987 cubic feet of water or 0.02 acre feet. The site is also located in both the City Floodway and City Flood Fringe. The finish floor, ductwork, HVAC, and electrical components of the proposed structure will be constructed at an elevation 2.5 feet above the 100 year water surface elevation for that area. For the City Floodway area, all proposed development will be constructed to the existing elevation or just below the existing elevation to prevent a rise in the water surface elevation. An elevation certification will be provided once construction is completed for both the structure and the portions of the driveway constructed in the floodway. The structure will be elevated with existing soil material backfilled, compacted and sloping down from the just below the finish floor at a 4:1 slope to the existing ground. This slope will provide positive drainage away from the structure. EROSION CONTROL Erosion Control measures for the proposed improvements have been shown on the Landscape and Erosion Control Plan. Erosion control measures include silt fence surrounding and located just outside the construction limits of the project. As stated in the drainage section, the site is relatively flat which will help minimize sediment runoff. During rain events, sediment will be captured by the silt fence and prevented from traveling offsite. The proposed construction limits is approximately 32,000 sf or 0.74 acres. Since the site will disturbed less than one acre, a storm water discharge will not be required. However, if the contractor decides to expand the area, a permit will be required prior to doing so. The site will also include a sediment tracking pad at the construction site exit. This will include larger aggregate or fabricated pad to be selected by the project Contractor. This will minimize material being tracked offsite onto West Vine Drive. In the event material is tracked offsite, the Contractor will be responsible to remove said material and dispose of properly. The site includes one storm sewer pipe culvert that is located at West Vine Drive and the proposed emergency access. Straw waddles will be placed at the entrance of the pipe culvert to minimize sediment entering said pipe culvert. In the event sediment enters the pipe, the Contractor will be responsible to remove said material and dispose of properly. The Contractor will modify erosion control measures as necessary for conditions, and construction phases. The final stages of construction will include seeding and reclamation efforts. Once the site has been stabilized with final surfacing materials and vegetation, the Owner or Contractor will be able to remove the silt fence and straw waddles. STOCKPILING OPERATIONS Stockpiling of dirt during construction may be necessary for the sequencing of construction activities and should be somewhat minimal and temporary for this site. Stockpiles that are generated shall be contained within the silt fence area to minimize sediment issues. It is anticipated stockpile material will be utilized to backfill around the concrete foundation once concrete strength has been achieved. STRUCTURE CONSTRUCTION The excavated dirt in and around the building needs to be contained during construction so sediment is not transported to the parking lot during storm events. This should be contained by means of silt fence or straw wattles. Dirt that will remain for an extended period of time shall be covered with reinforced poly plastic sheets ore seeded. SUMMARY Due to existing conditions, slopes of the property and comparing the size of the proposed development to the existing lot, no negative impacts are anticipated for this development or create issues for adjacent properties. I appreciate your time and consideration in reviewing this submittal. Please contact me at 970- 420-0086 or kent@avipc.com if you have any questions. Respectfully Submitted, AVI PROFESSIONAL CORPORATION Thomas Kent, P.E.