Preliminary Drainage Report
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PRELIMINARY DRAINAGE REPORT FILING NO. 1, LOT 1, BLOCK 1, FIRESTONE SUBDIVISION ENT CREDIT UNION E. Hampden Avenue & S. Tower Road Aurora, CO 80013 PREPARED FOR: PREPARED BY: Ent Credit Union Galloway & Company, Inc. 7250 Campus Drive 6162 S. Willow Drive, Suite 320 Colorado Springs, CO 80920 Greenwood Village, CO 80111 Contact: Jeff Wilkins Contact: Jennifer Romano, PE Tel: (719) 550-6795 Tel: (303) 770-8884 DATE: February 23, 2021 6162 S. Willow Drive, Suite 320 Greenwood Village, CO 80111 303.770.8884 • GallowayUS.com PRELIMINARY DRAINAGE REPORT ENT Credit Union Legal Description Lot 1, Block 1, Firestone Subdivision Filing No. 1, located in the southwest 1/4 of Section 34, Township 4 South, Range 66 West of the 6th Principal Meridian, City of Aurora, County of Arapahoe, State of Colorado, containing 36,984 square feet or 0.849 acres of land more or less. Preparation Date 02/23/2021 Revised: 04/23/2021 Revised: XXXXX Prepared for Ent Credit Union 7520 Campus Dr Colorado Springs, CO, 80920 Attn: Jeff Wilkins Email: [email protected] Tel: (719) 550-6795 Prepared by: Reviewed by: ________________________________________ ____________________________ Duncan Rady Jenny Romano Galloway & Company, Inc. Page 2 of 16 Ent Credit Union - Hampden & Tower Aurora, CO ENGINEER’S STATEMENT I affirm that this report and plan for the Preliminary drainage design for Ent Credit Union was prepared by me (or under my direct supervision) in accordance with the provisions of the City of Aurora Storm Drainage design & Criteria manual for the owners thereof. I understand that the City of Aurora does not and will not assume liability for drainage facilities designed by others. Jenny Romano, PE #44401 Date For and on behalf of Galloway & Company, Inc. DEVELOPER’S CERTIFICATION “Ent Credit Union hereby certifies that the drainage facilities for Ent Credit Union shall be constructed according to the design presented in this report. I understand that the City of Aurora does not and will not assume liability for the drainage facilities designed and/or certified by my engineer and that the City of Aurora reviews drainage plans pursuant to the Municipal Code; but cannot, on behalf of Ent Credit Union, guarantee that final drainage design review will absolve Ent Credit Union and/or their successors and/or assigns of future liability for improper design.” Authorized Signature Date Jeff Wilkins Galloway & Company, Inc. Page 3 of 16 Ent Credit Union - Hampden & Tower Aurora, CO TABLE OF CONTENTS I. Introduction ................................................................................................................................................ 6 Location ............................................................................................................................................ 6 a. Adjacent Streets, subdivision name, lot and block, site plan name .............................................. 6 b. Vicinity Map ................................................................................................................................... 6 c. Surrounding Development ............................................................................................................ 6 Proposed Development.................................................................................................................... 6 a. Property Description ...................................................................................................................... 6 b. Type of Development .................................................................................................................... 6 c. Requested Variances .................................................................................................................... 7 II. Historic Drainage ....................................................................................................................................... 7 Overall Basin Description ................................................................................................................. 7 a. Off-Site Basin ................................................................................................................................ 7 b. Major Drainage Ways .................................................................................................................... 7 Drainage Patterns Through Property ............................................................................................... 7 Outfalls Downstream from Property ................................................................................................. 8 III. Design Criteria ......................................................................................................................................... 8 Design Criteria References .............................................................................................................. 8 a. Existing Drainage Reports ............................................................................................................ 8 b. USDCM ......................................................................................................................................... 8 c. City Master Plan and Drainage Studies ........................................................................................ 8 Hydrologic Criteria ............................................................................................................................ 8 a. Rainfall Source .............................................................................................................................. 8 b. Calculation Method ....................................................................................................................... 8 c. Detention Volume Computation Method ....................................................................................... 8 d. Design Frequencies ...................................................................................................................... 9 Hydraulic Criteria .............................................................................................................................. 9 a. Reference Sources Other than USDCM ....................................................................................... 9 b. Identify Design Frequencies .......................................................................................................... 9 c. Water Surface Profile Method ....................................................................................................... 9 d. Major Drainageways ..................................................................................................................... 9 IV. Drainage Plan .......................................................................................................................................... 9 General Concept .............................................................................................................................. 9 a. Conveyance of Off-Site Drainage ............................................................................................... 10 Galloway & Company, Inc. Page 4 of 16 Ent Credit Union - Hampden & Tower Aurora, CO b. Coordination with Surrounding Developments ............................................................................ 10 c. Detention Pond/Water Quality BMP Plan ................................................................................... 10 Specific Details ............................................................................................................................... 10 V. Conclusions ............................................................................................................................................ 11 Compliance with Standards ........................................................................................................... 11 Summary of Concept ..................................................................................................................... 11 a. Degree of Protection to Existing Site .......................................................................................... 11 b. Measures Taken to Provide Adequate on-site Drainage and Enhancement to Stormwater Quality .................................................................................................................................................. 12 VI. References ............................................................................................................................................ 12 Appendices: A. Exhibits and Figures B. Existing Drainage Reports C. Hydrologic Computations D. Hydraulic Computations E. Drainage Map Galloway & Company, Inc. Page 5 of 16 Ent Credit Union - Hampden & Tower Aurora, CO I. Introduction Location a. Adjacent Streets, subdivision name, lot and block, site plan name The proposed Ent Credit Union is located in Arapahoe County, within the Seven Hills Plaza shopping complex, at the corner of South Tower Road and East Hampden Avenue, and within the original tenant space of Firestone Complete Auto Care facility. The site is contained in the southwest quarter of Section 34, Township 4 South, Range 66 West of the 6th Principal Meridian. This site is immediately north of East Hampden Avenue and approximately 650’ east of South Tower Road. b. Vicinity Map Please refer to Appendix A for Vicinity Map. c. Surrounding Development Adjacent development consists of primarily commercial