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HomeMy WebLinkAboutCHEROKEE FLYING HEIGHTS - PDP - 17-00 - CORRESPONDENCE - REVISIONS (9)Page 4 February 14, 2001 Project No: 1760-01-00 Re: Cherokee Flying Heights; Ft. Collins, Colorado If you have further comments or questions, please call us directly at 226-5334 so we can resolve any specific issue immediately. Sincerely, Mark Oberschmidt, Design Engineer Shear Engineering Corporation MEO/mo Shear Engineering Corporation cc: Mike Jensen Cameron Gloss; Current Planning Mikal Torgerson; M Torgerson Architects Derek Marchi; Advanced Professional Engineering Rick Lewis; RJL Surveyors .- Ib Page 3 February 14, 2001 Project No: 1760-01-00 Re: Cherokee Flying Heights; Ft. Collins, Colorado a. Sub -basin 1 contributes to the proposed water quality/detention pond. b. Sub -basin 2 consists of Lot 1 and a portion of the entry road. c. Sub -basin 3 consists of the'/s ROW along the frontage of the site. 3. Sufficient freeboard is provided between the buildings and the valley pan along the south property line. Lowest openings for the units are specified to be 1.5 feet above the maximum Water Surface Elevation (72.00) or 73.50 feet. A note is provided on the Drainage and Erosion Control Plan stating this. 4. A table listing the proposed TOW elevations and the lowest allowable opening elevation is included on the Drainage and Erosion Control Plan. 5. Additional detail on the proposed concrete channels, specifically profiles, showing the flowlines and tops of the tall curb will be provided prior to approval. 6. A larger scale plan of the detention pond will be provided in order to show sufficient detail for construction prior to final approval. 7. Sufficient freeboard is provided in the curbed channel along the north property line for the expected 100-year flow at the 90-degree turn located at the northeast corner of the developed lot. 8. Additional detail of the water quality structure and the outlet structure will be provided after we have discussed the criteria for designing the pond. ..9. A speed bump was added at the high point on the private drive located east of the valley pan to prohibit stormwater from leaving the site via the street. The street profile is shown and was used to model the cross section through the pan to determine its capacity and the estimated flow depth. This should suffice for the cross section you requested. 10. Metal sidewalk culverts are shown on the plans at all locations where there is concentrated flow into the street from the lawn areas. This concludes our response to your most current review comments concerning the Final Drainage and Erosion Control Report and the Final Utility Plans for Cherokee Flying Heights We would like to meet with you and discuss our the issues discussed here. Page 2 February 14, 2001 Project No: 1760-01-00 Re: Cherokee Flying Heights; Ft. Collins, Colorado c. A special improvement district, set up by the City, would help pay for these improvements. Property owners, including our client, aided by these improvements, would share in these expenses. d. The City encourages development of sites with densities such as provided by Cherokee Flying Heights. The City also encourages infill developments like this site. This density prohibits/conflicts with complete compliance of the current City Stormwater criteria (i.e. detaining and releasing at the 2-year historic rate). Since providing this detention severely impacts the development of the site in accordance with the densities proposed by the city plan, a comparison is presented between the pond requirements following a historic 2-year release and a historic 100-year release. It is proposed that the historic 100-yr peak flows be used as the design criteria rather than the 2-year peak flow. 3. The street capacity at the low point is the major storm street capacity. 4. Sub -basin 1 consists of four minor basins (In, Is, lc and Ip). A peak flow calculation was not provided for minor basin 1p since it is the pond site. Therefore, it is not included in the flow summary. 5. The historic basin area of the site has been corrected to be consistent with the developed site area. The existing ROW area was not included in the previous calculations. 6. We have provided a peak flow calculation for the entire site as well as the peak flow calculation from sub -basin 1 only. 7. The overland flow length for design points I and Ic begins at the southwest corner of the site and flows north. A travel path exhibit is included in the calculations for your convenience. 8. The capacity of the valley pan and the street at the low point has been determined. We have provided a speed bump at the high point to ensure that the high point is not over topped. 9. The landscape architect has been provided with the site data including all drainage, sewer and water infrastructure. Responses to Written Comments 1. It is understood that you are requesting detention and water quality. The proposed site plan does not contain enough open land area to provide both the required detention volume and water quality volume. We would like to get together with you at your earliest convenience to discuss the alternatives noted previously. 2. Development of the site has divided the site into 3 sub -basins (1-3). February 14, 2001 Project No: 1760-01-00 Basil Hamden City of Ft. Collins Stormwater Utility P.O. Box 580 Ft. Collins, Colorado 80524 Re: Cherokee Flying Heights; Ft. Collins, Colorado Dear Basil, This letter serves as the response to your most current review comments concerning the Final Utility Plans and the Final Drainage and Erosion Control Report for Cherokee Flying Heights. We have addressed your written comments that we received by e-mail on February 12, 2001 as well as the redlined comments on the plans and in the report. Please note the following plan changes made since our last submittal. • Provisions for a future north south ROW have been provided at the request of the Planning Department and the Engineering Department. This ROW has been relocated to the center of the site. • Provisions for access onto the Oak Street ROW to the south are now provided for future dedication. When the connection is made onto Oak Street, the connection onto North Taft Hill Road will be removed. Responses to redlined comments in the report 1. The three sub -basins are more clearly defined in the report. 2. It is our understanding that you would like this site to provide water quantity detention as well as quality. Please consider the following issues: a. The site is located near the southern limits of the West Vine Basin. Based on this, a conclusion can be reached that the flows from the site restricted for water quality or water quantity only, will not adversely affect the street capacity of Taft Hill Road in this area. b. The City is currently looking at how to improve the drainage conditions in the West Vine Basin by implementing regional improvements. Regional improvements are much more effective at restricting the stormwater flows to prescribed levels than small site - by -site detention ponds. This site could be considered in the design of the regional improvements, not as stand-alone. 4836 S. College, Suite 12 Ft. Collins, CO 80525 (970) 226-5334 Fax (970) 282-0311 www.sheitrengineering.com