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Home My WebLink AboutBURNS RANCH AT QUAIL RIDGE RF CLUSTER PLAN AND RF SUBDIVISION REVIEW - 23-90B - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTPRELIMINARY DRAINAGE REPORT FOR THE BURNS RANCH AT QUAIL RIDGE October 26, 1990 Prepared for: The Burns Family 2837 Overland Trail Fort Collins, Colorado 80526 Prepared by: RBD, Inc. Engineering Consultants 2900 c3outh College Avenue Fort Collins, Colorado 80525 (303)226-4955 RB.) Job No. 394-001 INDEX Page Introduction 1 Location Purpose 1 Existing Condition 1 Proposed Description 1 Procedure 2 Design Criteria 2 Offsite Drainage 2 onsite Drainage 3 Conclusions and Recommendations 3 .References g Appendix vicinity Map 1 2 Year and 100 Year Historical and Developed Rational Storm Discharge Calculations 2 Quail Hollow Culvert Sizing Calculations g Quail Hollow Detention Pond No. 1 Sizing Calculations 10 Mass Diagram Calculations for Pond No. 1 1 11 Burns Ranch Storm Sewer System Sizing Calculations 14 I I INTRODUCTION Location The Burns Ranch at Quail Ridge; as shown on the vicinity map in Appendix, is a parcel of land with approximately 45 acres planned for estate residential development and open space. The northern boundary of the site is located 1/4 mile south of Drake Road and the southern boundary lies 1/2 mile South of Drake Road. The site lies west of the southerly extension of overland Trail and west of the future Filing 7 in the Quail Hollow Subdivision. More specifically this site is located in the Northeast 1/4 of Section 29, Township 7 North, Range 69 West of the 6th Principal Meridian in Fort Collins, Colorado. Purpose The purpose of this report is to create an organized plan for future development within the Burns Ranch. This report will address passing the runoff from the 2-year and 100-year design storms through the site to assure the safety of life and property. EXISTING -CONDITION The site is vegetated with natural Colorado grasses and slopes generally easterly at grades around 7% to 12%. Historically, flows in this area have been transported to Spring Creek via an unnamed tributary. The site is traversed by an irrigation canal lateral. There is an existing wetlands/wildlife area in the adjacent Filing 7 of the Quail Hollow Subdivision. (See Preliminary Drainage Plan). This area has been created by the artificially damming of a natural drainage channel in order to 'create an irrigation water source. The Burns Ranch development will discharge storm water runoff into the existing wetlands/wildlife area in Filing 7 of Quail Hollow. Stormwater runoff will pass through the wetlands/wildlife area and eventually be transported to Pond No. 1 within the Quail .Hollow Subdivision. Pond No. 1 is a proposed temporary detention pond to be used until a regional detention pond is built in the future by others. PROPOSED DESCRIPTION this site, in a fully developed condition, is proposed to be estate single family residences with open spaces meandering through the development. The southern portion of the project is bounded by the City of Fort Collins Pine Ridge Open Space and the western portion of the project is bounded by the Dixon Reservoir.. 1 PROCEDURE Design Criteria In accordance with the City of Fort Collins Storm Drainage Design Criteria, this estate residential development was modeled for a 2 year (minor) and a 100 year (major) storm event using the Rational formula in accordance with Section 3.2 in Fort Collins Drainage Criteria Manual. Basin runoff calculations; included in the Appendix; were based on the following assumptions: historical calculations are based upon existing slopes and overland flow times for pasture land/nearly bare ground, and developed calculations are based on the proposed developed ground (ie. paved area, grassed waterway, open space etc.) and proposed street grades to the points of concentration. Detention storage was calculated; using the Mass Diagram Method; per the City of Fort Collins Storm Water Utility. The required storage is the difference between the 100 year developed flow and the 100 year historical flow. Typically, detention storage is based on the difference between the 100 year developed flow and the 2-year historical event. However, based upon the Spring Creek Master Plan, the City of Fort Collins Storm Water Utility is planning a regional detention facility at Spring Creek just South of Drake Road and on the west side of Taft Hill Road. Upon completion of that facility, on -site detention facilities upstream will not be required. However, prior to completion of the regional detention facility, on -site detention facilities must be designed to release the historical rate of the occurring event. Detention ponds must be sized with staged outlet structures to release the historical rate of the occurring event. (ie. 2-year storm will release 2-year historic release rate). Rational calculations detailing basin areas, sloped, basin lengths etc. are included in the Appendix. ,. Offsite-Drainage From the Quail hollow Subdivision Filings 4 thru 7 Preliminary Drainage Report, discharge from the area east of the hogback to the west edge of the Quail Hollow subdivision (Burns Ranch) was routed through the Quail Hollow subdivision and into the onsite detention facility referred to as pond No. 1. At the time of the above referenced drainage report, we were under the impression that the Burns Ranch property would remain as undeveloped ground in the future. Therefore the culverts through Filing 7 of Quail Hollow were sized assuming the Burns Ranch property remained in its historic natural condition. Now with the development of the Burns Ranch property, we have resized the culverts through Filing 7 of Quail Hollow and also. recalculated the required storage in their onsite detention facility referenced to as pond No. 1. These calculations are included in the Appendix. The Burns Family will coordinate with the owners of Quail Hollow in�order to insure that the increased' pipe sizes and detention pond volume are compensated for and constructed. Onsite Drainaae The Burns Ranch site is divided into two primary drainage basins by a minor ridge line. The drainage basins can be seen on the drainage' plan. A portion of the site is proposed to drain northeast to the intersection of Overland Trail and Skimmerhorn Drive. The remainder of the site is proposed to drain to a low point near Skimmerhorn Drive and Skimmerhorn Court. In order to prevent cross basin diversion of flows, we are proposing to intercept the 100 year surface runoff collected at the intersection of Skimmerhorn Drive and Overland Trail by a storm sewer and inlet system. These drainage flows will be redirected southerly and eventually be collected in Pond No. 1. within Quail Hollow. Because the Burns Ranch site lies immediately south of a minor ridge line of which Overland Trail has a high point on, and Skimmerhorn Drive intersects Overland Trail on the opposite side of the ridge line, the above described storm sewer system is necessary to redirect surface runoff to the south side of the ridge line. The low point at Skimmerhorn Drive and Skimmerhorn Court is proposed in order to collect the 100 year surface runoff from the site and transport the drainage waters, by a storm sewer system, beneath the existing irrigation canal lateral. The drainage waters are proposed to be released onto the Quail Hollow Filing 7 existing wetland/wildlife area and will pass through this area and eventually be collected in Pond No. 1 within Quail Hollow. Calculations for these facilities are included in the Appendix. Additionally the 2 year surface runoff form the site will be collected by the Storm sewer and inlet systems and redirected southerly to Pond No. 1 within Quail Hollow. CONCLUSIONS AND RECOMMENDATIONS All computations within this report have been completed in compliance with the City of Fort Collins Drainage Criteria Manual. The proposed drainage concepts will adequately transport and provide for the detention of developed on -site flows from the proposed Burns Ranch development. A few minor modifications to Filings 5 and 7 within the Quail Hollow Subdivision will be necessary in order to direct the Burns Ranch surface runoff into Pond No. 1 within Quail Hollow. The following culverts within Filing 7 of Quail Hollow need to be increased in size or added: F EXISTING CULVERT SIZE PER QUAIL HOLLOW PRELIM - LOCATION NARY DRAINAGE REPORT Tiflin Ct. None Brendan Ct. 36" RCP Overland Trail 4211 RCP PROPOSED CULVERT.SIZE PER THIS PRELIMINARY DRAINAGE REPORT 36" RCP 54" RCP 5411 RCP in addition to the above culvert modifications, an additional 1.23 acre- feet of detention pond storage is necessary in the Quail Hollow Pond No. 1, in order to detain developed surface runoff from the Burns Ranch. Respectfully submitted by: RBD, Inc. Engineering Consultants Prepared by: 4' ` Sevin W. Gingeey6,p E. Project Engineer u;;ui;;tliilli, '��V M 4 REFERENCES 1. Storm Drainaae Desian.Criteria_and Construction Standards by the City of Fort Collins,,Colorado May 1984. 2. Quail Hollow Subdivision, Filings 4 through 7, Preliminary Drainage. Report by RBD, Inc., Engineering Consultants, November 1989. 5 APPEND IIX a 1, 1 "',) I . 1. tZ ......... ..... ............... 2-4 - 4•1; 1T 505 H ighe Stt di,. diui 1 A b live!- It of PLEASANT x L AK E'AN 0 ANAL 11. T4 W BRAKEBRAKEROAD 5090 i".BUR S RA CH T QUAIL RIDGE 4\- V 'Drt Lake tit Z, 33 I.I.. 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