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HomeMy WebLinkAbout1ST BANK AT HARMONY MARKET PUD, 4TH FILING - PRELIMINARY & FINAL - 54-87F - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT FINAL DRAINAGE AND EROSION CONTROL STUDY FOR THE 1ST BANK IN THE HARMONY MARKET P.U.D. FOURTH FILING FORT COLLINS, COLORADO REIINC. Engineering Consultants I I N I FINAL DRAINAGE AND EROSION CONTROL STUDY FOR THE 1ST BANK IN THE HARMONY I MARKET P.U.D. FOURTH FILING FORT COLLINS, COLORADO 1111 August 31, 1992 Prepared for: Client: 1st Bank of Westland 10403 West Colfax Lakewood, Colorado 80215 Prepared by: RBD, Inc. Engineering Consultants 2900 South College Avenue Fort Collins, Colorado 80525 (303) 226-4955 RBD Job No. 519-001 I 111 9SONC. Engineering Consultants 2900 South College Avenue I Fort Collins,Colorado 80525 303/226-4955 FAX:303/226-4971 August 31, 1992 Ms. Kathy Malers City of Fort Collins Utility Services Stormwater 235 Mathews Fort Collins, Colorado 80522 111 t RE: Final Drainage and Erosion Control o Study for the 1st Bank Dear Kathy: We are pleased to submit to you, for your review and approval, this Final Drainage and Erosion Control Study for the 1st Bank to be located in the Harmony Market P.U.D. Fourth 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 111 have any questions. Respectfully, RBD Inc. Engineering Consultants W•11=4:77 Kevin W. Gingery, P.E. I I I Other offices:Denver 303/458-5526•Vail 303/476-6340•Longmont 303/678-9584 I TABLE OF CONTENTS DESCRIPTION PAGE I. GENERAL LOCATION AND DESCRIPTION IA. LOCATION 1 B. DESCRIPTION OF PROPERTY 1 II. DRAINAGE BASINS A. MAJOR BASIN DESCRIPTION 1 B. SUB-BASIN DESCRIPTION 1 III. DRAINAGE DESIGN CRITERIA A. REGULATIONS 1 B. DEVELOPMENT CRITERIA REFERENCE AND CONSTRAINTS 2 C. HYDROLOGICAL CRITERIA 2 D. HYDRAULIC CRITERIA 2 E. VARIANCES FROM CRITERIA 2 IV. DRAINAGE FACILITY DESIGN 111 A. GENERAL CONCEPT 2 B. SPECIFIC DETAILS 2 V. EROSION CONTROL A. GENERAL CONCEPT 3 B. SPECIFIC DETAILS 3 VI. CONCLUSIONS A. COMPLIANCE WITH STANDARDS 4 B. DRAINAGE CONCEPT 4 C. EROSION CONTROL CONCEPT 4 REFERENCES 4 APPENDIX IHYDROLOGY 1 HYDROLOGY 3 I EROSION CONTROL 12 TABLES AND FIGURES 16 I I I I FINAL DRAINAGE AND EROSION CONTROL STUDY I FOR THE 1ST BANK IN THE HARMONY MARKET P.U.D. FOURTH FILING IFORT 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. More specifically, this site is located in the northeast corner of Section 1, Township 6 North, Range 69 west of the 6th Principal Meridian in Fort Collins, Colorado. II B. Description of Property P P Y The existing Harmony Market P.U.D. has been developed in three phases and contains a Pace Warehouse, Builders , S uare and Steeles Market. Square, I Adjacent to the Steeles Market is the proposed site of the 1st Bank. The site is located on the southwest corner of the Lemay Avenue and Harmony Road intersection. II. DRAINAGE BASINS IA. Major Basin Description The site is located within the McClellands Basin. No major drainageway 111 exists within the Harmony Market P.U.D. development or downstream Oak/Cottonwood Farm site. B. Sub-Basin Description Historic drainage patterns on the subject site are southwesterly across the site to the existing Steels Market access roadway and existing storm sewer system. No off-site drainage crosses the subject site. III. DRAINAGE DESIGN CRITERIA A. Regulations 111 The City of Fort Collins Storm Drainage Design Criteria is being used for the subject site. I 11 I B. Development Criteria Reference and Constraints The subject site historically drains southwesterly to the existing storm sewer system and inlet adjacent to the site in the Steels Market access roadway. The Harmony Market P.U.D.Third Filing contains an existing detention pond with a release rate in conformance with the McClellands Basin Master Drainage Planning criteria. The detention pond was sized for fully developed storm water runoff from the subject site. C. Hydrological Criteria The Rational Method is being used to determine runoff peak flows from the site. The 10 and 100 year rainfall criteria, which was obtained form the City of Fort Collins, is the criteria which was utilized. This criteria is included in the Appendix. D. Hydraulic Criteria All calculations within this study have been prepared in accordance with the City of Fort Collins Drainage Criteria. E. Variances from Criteria No variances are being sought for the subject site drainage. IV. DRAINAGE FACILITY DESIGN A. General Concept The 1st Bank is planned as a bank site. The site will be developed in stages,with a modular building installed in the initial stage, and a permanent U building installed as banking warrants. Included in the back pocket of this report is the Drainage and Erosion Control Plan for the subject site. B. Specific Details Basin 1 is proposed to drain into the existing Steels Market storm sewer I system and related detention pond. Runoff from the site will outlet onto the Steels Market access roadway, travel south to the existing cross pan, travel west across the cross'pan and into the existing curb inlet/detention pond system. From the appendix calculations, the existing detention pond volume was examined and found to be adequate to accommodate the ultimate developed 1st Bank site. 2 I I Basin 2 is proposed to drain into the existing curb and gutter of Lemay Avenue. This basin is proposed as all grass and thus the runoff will be very small. The Lemay Avenue curb and gutter system should be able to handle this very small amount of storm water runoff from the subject site. V. EROSION CONTROL A. General Concept The 1st Bank site 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 lot and landscaped areas until the disturbed ground is again vegetated. Thus the new improvements will be subjected to both wind and rainfall erosion. Per the City of Fort Collins Erosion Control Reference Manual for Construction Sites and related calculations in the appendix, the erosion control performance standard for the subject site is 78.35 % . From the calculations in the appendix, the effectiveness of the proposed erosion control plan is 99.57 % . It is anticipated that the construction duration of this project will be less than 6 weeks due to the limited amount of work to be completed. Therefore the erosion control plan as specifically detailed below, most nearly meets the City of Fort Collins requirements. • B. Specific Details If the curb, gutter, and asphalt are not installed within 6 weeks after their construction begins, then these improvements should not be included in the erosion control effectiveness calculations. Given the size of this project and the small amount of work to be completed, we anticipate that construction of the curb, gutter, and asphalt can be completed within 6 weeks after their Iconstruction begins. As the first step in the construction process, the erosion control gravel inlet filter should be installed to protect the existing storm sewer system. Then the subject site should have a silt fence installed around the perimeter of the property to prevent construction sediment from leaving the site. After the overlot grading and utility installation has been completed, the parking lot surface should receive the curb, gutter and pavement surfaces. After installation of the curb, gutter and pavement surfaces, the permanent landscaping surfaces (grass sod) should be installed to protect the bare ground. Once all of these improvements have been completed, the Isediment fence and gravel inlet filter can be removed from the construction 3 I site. VI. CONCLUSIONS 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 plan are in compliance with the City of Fort Collins drainage criteria. The developed storm water runoff from the site will be collected in the adjacent Steels Market detention facilities and conveyed downstream as currently is occurring with historic drainage from the subject site. C. Erosion Control Concept The proposed erosion control concepts adequately provide for the control of wind and rainfall erosion from the 1st Bank site. Through construction of the proposed erosion control concepts, the City of Fort Collins 111 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 the City of Fort Collins erosion control criteria. 1 REFERENCES 1. Storm Drainage Design Criteria and Construction Standards by the City of Fort Collins, Colorado, May 1984, Revised January 1992. 2. Erosion Control Reference Manual for Construction Sites by the City of Fort Collins, Colorado, January 1991. 111 3. Harmony Market P.U.D. Third Filing Final Drainage Report by RBD Inc., September 20, 1990. U 4