1997-03-19_REPORT - M1981302

• Permit No: M1981302
• IBM Index Class Name: Report
• Doc Date: 3/19/1997
• Doc Name: INITIAL RECONNAISSANCE OF DRAINAGE NETWORK AND SOUTH BOULDER CREEKS HYDROLGOY HWY 36 TO APPROXIMATEL
• From: TAGGART ENGINEERING ASSOC INC
• To: URBAN DRAINAGE AND FLOOD CONTROL DISTRICT
• Media Type: D
• Archive: No

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ENGINEERING ASSOCIATES.INC.
2480 West 26tn Avenue•Suite 340-B•Denver.Colorado 80211 •1303)455.3600•FAX[phone]
March 19, 1997
' Mr. Bill DeGroot
Chief, Floodplain Management
Urban Drainage and Flood Control District
2480 West 26th Avenue, Suite 156-B
Denver, CO 80211
RE: Initial Reconnaissance of Drainage Network and South Boulder Creek's
Hydrology, Highway 36 to Approximately the Wellman Ditch, Phase 11.
Dear Mr. DeGroot:
Our Phase I effort identified that the Flood Hazard Area Delineation Report
(FHAD) underestimated the flow leaving South Boulder Creek at Highway 36 and
did not portray spillage paths to the west side of the valley, particularly along
Foothills Parkway. This Phase II report provides an initial reconnaissance of the
overflow routes and approximate flows of the West Valley Overflow north of
Highway 36 to the area of the Wellman Ditch. Drawing No. 3 depicts the results
of this overflow analysis (Drawings 1 and 2 are with the Phase I report).
We obtained and reviewed additional hydrology information by the U.S. Army
Corps of Engineers (Corps). In Phase I we modified the Corps' Storm Water
Management Model (SWMM) model to better reflect the Viele watershed and its
U outfall channel to South Boulder Creek. In this Phase II we have greatly refined
�1 the SWMM model detail downstream of Highway 36 in order to identify
Usignificant flow paths and approximate discharges.
The 100 year spill from South Boulder Creek just upstream of Highway 36 would
flow to the northwest along the south side of the freeway, with an initial portion
returning to South Boulder Creek through the Viele outfall, spillage from the Dry
Creek Ditch No. 2, and the Anderson Ditch. The majority of the spill would
U overtop Highway 36 west of Foothills and flow northerly to the intersection of
Baseline and Foothills. The intersection topography would largely control the
hydraulics of the spill distribution and would result in six surface flow paths and a
seventh path through the culverts under Foothills between the small detention
ponds that are south of Baseline on either side of Foothills. Three of the surface
paths would follow Foothills to the north (two travel lanes and the westerly
u borrow ditch). Two would follow Baseline to the east, and one would overtop
u Foothills slightly south of the intersection. The last three routes would
commingle and split again, following the streets to the north and the Crossover
Hydrology•Hydraulics•Sediment Transport
Civil Engineering for Flood Control Waterways.Water Supply and Parks
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