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HomeMy WebLinkAboutHARMONY MARKET PUD, 5TH FILING - PRELIMINARY & FINAL - 54-87G - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT1 FINAL DRAINAGE AND EROSION CONTROL STUDY FOR HARMONY MARKET P.U.D. FIFTH FILING FORT COLLINS, COLORADO March 1, 1993 Prepared for: White and Warburton 1023 East Lincoln Way Cheyenne, Wyoming 82001 Prepared by: RBD, Inc. Engineering Consultants 209 South Mel drum Fort Collins, Colorado 80521 (303) 482-6368 RBD Job No. 547-001 MiSOINC. Engineering Consultants 209 S. Meldrum Fort Collins, Colorado 80521 303/482-5922 FAX: 303/482-6368 March 1, 1993 Ms. Kathy Malers City of Fort Collins Utility Services Stormwater 23.5 Mathews Fort Collins, Colorado 80522 RE: FINAL DRAINAGE AND 'EROSION CONTROL STUDY FOR THE HARMONY MARKET P.U.D. FIFTH FILING 547-001 Dear Kathy: We are pleased to submit to you, for your review and approval, this Final Drainage and Erosion Control Study for the Harmony Market P.U.D. Fifth Filing. All computations within this report have been completed in compliance with the City of Fort Collins Storm Drainage Design Criteria We appreciate your time and consideration in reviewing this submittal. Please call if you have any questions. Respectfully, RBD Inc. Engineering Consultants 7,47 ziae Tracy Kittell Design Engineer cc: John White P Other Offices: Denver 303/458.5526 • Vail 303/476-6340 TABLE OF CONTENTS DESCRIPTION PAGE GENERAL LOCATION AND DESCRIPTION ............................ 1 Location................................................. 1 Description of Property ...................................... 1 DRAINAGE BASINS ............................................. 1 Major Basin Description ..................................... 1 Sub -Basin Description ...................................... 2 DRAINAGE DESIGN CRITERIA ..................................... 2 Regulations .............................................. 2 Development Criteria Reference and Constraints .................... 2 Hydrological Criteria ........................................ 2 Hydraulic Criteria ...... ..................................... . 2 Variances from Criteria ...................................... 3 DRAINAGE FACILITY DESIGN ..................................... 3 General Concept .......................................... 3 Specific Details ........................................... 3 EROSION CONTROL ............................................. 4 General Concept .......................................... 4: Specific Details ......................................... 5 CONCLUSIONS ................................. 5 Compliance with Standards ................................. 5 Drainage Concept ....... ............................. 5 Erosion Control Concept .................................... 6 REFERENCES ................................................ 6 APPENDIX HYDROLOGY DETENTION EROSION CONTROL TABLES AND FIGURES DRAINAGE AND EROSION CONTROL PLAN l FINAL DRAINAGE AND EROSION CONTROL STUDY FOR THE HARMONY MARKET P.U.D. FIFTH FILING FORT COLLINS, COLORADO I. GENERAL LOCATION AND DESCRIPTION A. Location The Harmony Market P.U.D. is located immediately south of Harmony Road between Boardwalk Drive and Lemay Avenue. Morespecifically, this site Y is located in the Northeast quarter of Section 1, Township 6 North, Range 69 West of the 6th Principal Meridian in Fort Collins, Colorado. B. Description of Property The existing Harmony Market P.U.D. has been developed in three phases and contains a Pace Warehouse, Builders Square, and Steeles Market. The First Bank of Westland has submitted the Harmony Market P.U.D. Fourth Filing and has been given approval to construct a bank on the southwest corner of the Lemay Avenue and Harmony Road intersection, adjacent to Steeles Market. At the time of this report, First Bank has not started construction on their site. The Harmony Market P.U.D. Fifth Filing site is currently undeveloped. An existing road, without curb and gutter on the west side, is located on the west property line and is included in this study as a part of the project site. Oakridge Drive is located on the south perimeter of the study site, Lemay Avenue to the east and an undeveloped parcel of land to the north. IL DRAINAGE BASINS A. Major Basin Description The project site is located within the McClellands Basin. No major drainageway exists within the Harmony Market. P.U.D. development or downstream of the Oak/Cottonwood Farm site. 17 ` B. Sub -Basin Description Historic drainage patterns on the study site are southeasterly across the site to a temporary sediment basin and existing storm sewer system, both - constructed as a part of Harmony Market P.U.D. Third Filing [1]. The EWA existing asphalt paved road on the west of the project site drains across the study site because currently there is no curb and gutter to convey flow to Oakridge Drive. No off -site drainage cross the study site. III. DRAINAGE DESIGN CRITERIA A. Regulations The City of Fort Collins Storm Drainage Design Criteria [2] is being used for [1111 this study. B. Development Criteria Reference and Constraints The Fifth Filing of Harmony Market P.U.D. is part of Basin "F" as described in the Harmony Market P.U.D. Third Filing Final Drainage Report [1]. The Harmony Market P.U.D. Third Filing contains an existing temporary sedimentation pond located on this study site. The pond was constructed in accordance with the possible future layout of the project site. The layout of the project site is different that originally planned, proposed Y therefore the sedimentation pond will not be utilized for on -site detention. Filing contains a detention and release The Harmony Market P.U.D.. Third g P rate of 0.20 cfs/acre for this project site. This release rate was dictated by 1 the capacity of downstream facilities for the Oakridge West P.U.D. First Filing. This downstream development dictates a release rate of 0.20 cfs/acre for the maximum 100 year release rate. C. Hydrological Criteria The Rational Method is being used to determine run-off peak flows from the study site. Rainfall criteria for this study was obtained from the City of Fort Collins [2] and is included in the Appendix. The 10, and 100 year rainfall criteria was utilized to determine the planned developed flows. - D. Hydraulic Criteria All calculations within this study have been prepared in accordance with the City of Fort Collins Drainage Criteria [2]. 2 ■'. IV. E. Variances from Criteria No variances are being requested. DRAINAGE FACILITY DESIGN A. General Concept The Harmony Market P.U.D. Fifth Filing is planned as a "quick" auto lube center and car wash. Storm runoff from the site will be detained on -site with a release rate of 0.31 cfs into the existing storm sewer system. The parking/driveway will serve as the detention pond area. To prevent sediment from eroding onto the project site and Lemay Avenue and to replace the sediment pond currently located on the project site, a temporary sediment pond will be rough graded in the undeveloped lot located to the immediate north of the project site. B. Specific Details Basin 1's runoff is proposed to drain into an on -site detention pond and be released into the existing storm sewer system at a rate of 0.31 cfs. Storm water from the site will be conveyed to an area inlet located in the southwest corner of Basin 1 (Design Point 1) by overland and shallow gutter flow. Removed storm water by an area inlet will be transported via a proposed 15 inch reinforced concrete pipe (RCP) to an existing 15 inch RCP located north of the existing junction manhole. The release rate from Basin 1's detention pond will be controlled by an orifice plate located directly beneath the frame and grate of the area inlet. If the release rate is limited to 0.20 cfs/acre, the orfice size becomes unacceptably small. By placing the orfice horizontally beneath the frame and grate, the head on the orifice is reduced. With the orifice equation, a smaller value for the head results in a larger orifice size. the orfice size was set at a three inch diameter, which is considered the smallest practical orfice size. The resulting release rate increased to 0.31 cfs or 0.44 cfs/acre.. Since the area drained by the detention pond is only 0.707 acres, this higher release rate has minimal effect on the loading of downstream facilities. Because of the potential for clogging at the area inlet, an emergency spillway was provided on the east end of the south berm. Basin 2 is proposed to drain into the existing curb and gutter in Lemay Avenue and Oakridge Drive. This basin will consist of minor amounts of concrete sidewalk and will be landscaped with grass sod, trees, and shrubs. 3 At the corner of Lemay Avenue and Oakridge Drive (Design Point 2) the 10 year and 100 year runoff from Basin 2 will be 0.2 and 0.5 cfs respectively. The existing sump curb inlet and storm sewer system at Design Point 2 will be able to handle this very small storm water runoff from the project site. Storm water runoff from Basin 3 consists of flow from the existing asphalt road and proposed landscaped areas. A curb and gutter will be installed along the existing road to convey the storm water runoff to Oakridge Drive (Design Point 3). From Design Point 3, the flow will be carried to the sump curb inlet located at Design Point 2 by Oakridge Drive's curb and gutter. The 10 and 100 year storm water runoff at Design Point 3 will be 0.4 and 1.0 cfs respectively. - These flows are notincreased significantly from the current runoff because the impervious area within Basin 3 is only increased by approximately 300 square feet. The Oakridge Drive curb and gutter system and the existing sump curb inlet at Design Point 2 will be able to convey this runoff without exceeding their capacity. A temporary sediment pond is proposed to be rough graded in the undeveloped lot to the immediate north of the project site. This sediment pond is to replace the existing pond located within the project site. The existing 15 inch RCP storm sewer pipe, located within the existing sediment pond, will be extended north to the proposed sediment pond. V. EROSION CONTROL A. General Concept The Harmony Market P.U.D. Fifth Filing lies within the Moderate Rainfall and Wind Erodibility Zone per the City of Fort Collins zone maps. The potential exists for erosion problems during construction of the parking/driveways and landscaped areas until the disturbed ground is paved or revegetated. The proposed sediment pond within the undeveloped parcel of land north of the project site has the potential for erosion problems until adequate sediment barriers are installed together with revegetating the disturbed ground. Per the City of FortCollins Erosion Control Reference Manual for Construction Sites [3] and related calculations in the Appendix, the erosion control performance standard for the project site is 78.10%. The effectiveness of the proposed erosion control plan for the project site is 99.9%. Refer to the Appendix for the erosion control effectiveness calculations. 4 It is anticipated that the construction duration of this project will be less than six weeks due to the limited amount of work to be completed. Therefore, the erosion control plan as specifically detailed below, should meet the City of Fort Collins requirements. �Y B. Specific Details If the curb, gutter, and asphalt are not installed within six weeks after overlot grading begins, then these improvements should not be included in the erosion control effectiveness calculations. Given the size and scope of work to be completed for this construction project, we anticipate that installation �i of the curb, gutter, and asphalt can be completed within six weeks after construction begins. As a first step in the construction process, the temporary sedimentation pond will be rough graded in the undeveloped lot and sediment barriers ■� installed in the pond area to prevent sediment from leaving the site. The disturbed area within and around the pond will be seeded and mulched as shown on the Drainage and Erosion Control Plan in the Appendix. Before any grading or trenching begins within the project site, a sediment fence will be installed around the east, south, and west perimeter of the construction site. After the overlot and utility installation has been completed, the parking/driveway surfaces will receive the curb, curb inlet, gutter, and pavement surfaces. A gravel inlet filter will be installed around the curb inlet until the permanent landscaping surfaces (grass sod) has been installed. Once all of the improvements have been completed, the gravel inlet filter and sediment fence can be removed from the construction site. VI. CONCLUSIONS �i A. Compliance with Standards All computations within this report have been completed in compliance with the City of Fort Collins Storm Drainage Design Criteria. B. Drainage Concept The proposed drainage concepts presented in this report and shown on the Drainage and Erosion Control Plan are in compliance with the City of Fort Collins drainage criteria. The developed storm water runoff from the site will 5 �I be collected in an on -site detention pond, and the existing Lemay Avenue and Oakridge Drive's curb and gutter system. The release from the detention pond into the existing storm sewer system will be 0.44 cfs/ac for a total of 0.31 cis. The undetained storm water runoff that will enter the existing sump curb inlet at the corner of Lemay Avenue and Oakridge Drive k will be 0.6 cfs and 1.5 cfs for the 10 and 100 year storms respectively. This includes storm water runoff from Basins 2 and 3. These flows should have minimal effect on the existing sump curb inlet and related storm sewer system should be capable of conveying these flows with minimal -effect on the downstream system. C. Erosion Control Concept The proposed erosion control plan adequately provides for the control of wind and rainfall erosion from the study site. Through the construction sequence and proposed erosion control measures, the City of Fort Collins performance standards will be met. The proposed erosion control concepts presented in this report and shown on the Erosion Control Plan are in compliance with thd'City of Fort Collins erosion control criteria. REFERENCES 1. RBD Inc., Harmony Market P.U.D. Third Filing Final Drainage ReportTotal Site Preliminary - Revised Drainage ReportFort Collins. Colorado, August 30, 1990. 2. City of Fort Collins, Storm Drainage Design Criteria and Construction Standards, May 1984, Revised 1.992. 3. City of Fort Collins, Erosion Control Reference Manual for construction Sites, January 1992. C-9