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Home My WebLink AboutELEMENTARY SCHOOL 1990 - SPECIAL SITE PLAN REVIEW - 14-88A - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTFINAL DRAINAGE REPORT FOR POUDRE R-1 SCHOOL DISTRICT 1990 ELEMENTARY SCHOOL ENGINEERING PROFESSIONALS INC. 2000 Vermont Dr., Fort Collins, CO 80525 (303) 226-3852, 440-0506 (Denver Metro) Plaza of the Rockies, 111 South Tejon, Suite 300, Colorado Springs, CO 80903 (303) 634-5006 ■ 4 4 ■ 4 4 FINAL DRAINAGE REPORT FOR POUDRE R-1 SCHOOL DISTRICT 1990 ELEMENTARY SCHOOL MARCH, 1989 Prepared For: Dulaney Architecture 5261 South Quebec Street Suite 210 Englewood, Colorado 80111 Prepared By: Engineering Professionals, Inc. 2000 Vermont Dr. Fort Collins, CO 80525 w 4 ■ FINAL DRAINAGE REPORT FOR POUDRE R-1 SCHOOL DISTRICT 1990 ELEMENTARY SCHOOL LOCATION . The proposed school is to be situated on 10.0 acres located approximately 1500 feet west of South Taft Hill Road and 200 feet north of West Horsetooth Road, within the Horsetooth West Masterplanned area. More specifically, the site is located within the southeast quarter of section 28, Township 7 north, Range 69 West, which puts it in the upper third of the Spring Creek Basin. 0 EXISTING CONDITIONS The site presently drains by overland flow to the northeast. Two offsite basins (denoted as OS1 and OS2 on the plan) with a combined area of 4.62 acres located southwest of the site contribute overland flow to the site along the south and west property lines. The property has moderate slopes ranging between 1 % and 2.5%, with ground cover generally being sparse grasses. The site is not located within any designated floodplain. The school is located within an area assumed to contribute flow to the Rossborough Subdivision at historical rates (identified as offsite basin 2 in the Drainage Report for Rossborough Subdivision, prepared by Stewart and Associates, dated April 13, 1979). A drainage channel was constructed within the Rossborough Subdivision along the east side of Taft Hill Road to accept runoff from this basin, route it around the subdivision, and direct it to the Trend - Cedar outfall to Spring Creek. Currently, flow from this basin is directed to the west side of Taft Hill Road north of West Horsetooth Road where it appears to pond before ultimately flowing to the north and possibly overtopping South Taft Hill Road. To our knowledge, no operable culverts under South Taft Hill Road exist in this area which direct flows to the Rossborough channel. PROPOSED DRAINAGE School Site The school site will be drained in such a manner so as to maintain the existing drainage patterns as much as possible. The school site is divided into 3 basins (S1, S2 and S3) with each basin having its own detention pond. Flows are directed by swales, gutters and concrete pans to the detention ponds which are generally located along the east side of the property adjacent to the proposed collector street. The total runoff released from the 3 ponds will be the historic 2-year runoff for the site (3.3 cfs) in addition to the historic runoff from the offsite areas. The released flows will be directed to the west flow line of the proposed collector street 4 ■ by a sidewalk chase and covered channel. The following tables present the proposed developed school property drainage basin and detention pond data. SCHOOL SITE DRAINAGE BASIN DATA BASIN AREA (acres) C Q10 (cfs) Q10 0(cfs) 1 1.48 0.72 4.8 9.7 2 3.27 0.39 3.6 7.0 3 5.25 0.40 4.8 9.8 OS1 1.25 0.25 1.2 3.1 OS2 1.59 0.25 0.9 1.9 DETENTION POND DATA POND NO. VOLUME REQ'D RELEASE RATE HIGH WATER ELEV. (cubic feet) (cfs) 1 10,840 0.49 2 11,075 1.08 3 18,415 1.73 Collector Street Three basins, S1, S2 and S3, in addition to the school site area (and offsite basins) will ultimately direct runoff to the collector street. The boundaries of these basins were determined by discussions with the land planners for the Horsetooth West Master Plan as well as the topography of the area adjacent to the street. Historic flows were assumed from basins S1 and S3 while developed flows were projected for basin S2 and the street itself (basins S4 and S5). Detention storage for basin S2 and the street will ultimately be provided for within the Horsetooth West regional detention pond to be located adjacent to South Taft Hill Road. The following table presents data for the drainage basins directly contributory to the collector street. COLLECTOR STREET DRAINAGE BASIN DATA BASIN AREA (acres) C Q10 (cfs) 0100 (cfs) S1 0.76 0.25 0.4 0.9 S2 2.34 0.70 7.5 11.9 S3 0.46 0.25 0.3 0.5 S4 0.64 0.95 2.7 4.5 S5 0.64 0.95 2.7 4.5 Historical runoff from the school site will combine with the street drainage and be directed to a low point in the collector street adjacent to the school. The 10 and 100 year recurrence interval design flows at the upstream end of the cross pan to be constructed at the LE ■ low point are 6.7 cfs and 9.2 cfs, respectively. All flows will then be directed to the curb return constructed for future Bronson Street. From this point runoff will be via a temporary earthen swale to the west side of Taft Hill Road. The 10 and 100 year design flow for the swale are 16.9 and 25.6 cfs, respectively. Ultimately this runoff will be directed to the aforementioned regional detention pond by Bronson Street and a possible storm sewer system. 0 CONCLUSION The proposed drainage scheme for the Poudre R - 1 School District 1990 Elementary School safely routes minor and major storm flows through the site. Furthermore, the drainage design for the site is in accordance with the City of Fort Collins storm drainage criteria and is compatible with future improvements planned for the immediate area. 4 ENGINEERING PROFESSIONALS, INC. 9 Steven L. Kraushaar, P.E. I a a a a a a I 0