FLOOD04641

• County: Denver
• Community: All
• Stream Name: All
• Basin: South Platte
• Title: Proposed Hydrology for use in Hydraulic Analysis of FEMA Flood Studies and Restudies
• Date: 9/1/1989
• Prepared For: State of Colorado
• Prepared By: Resource Consultants
• Floodplain - Doc Type: Educational/Technical/Reference Information

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11.2

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the remaining 320 feet to Academy Boulevard where it enters two
6 by 6 feet box culverts. It flows under Academy Boulevard and
a small shopping center on the west side of the boulevard for
900 feet. There it outfalls into a concrete-lined channel at
the same point as the culvert from Briargate Boulevard (near
point P5 on Figure 11.1).

A 52-inch RCP culvert enters this same concrete channel 280
feet dDwnstream from the two previously discussed outfalls.
This culvert conveys the runoff from subbasins T4 and T8 to
this point. As previously mentioned, flow from subbasin T4 is
detained (In Pond 3) before reaching PCT. This detention
facility discharges into a 42" CMP which increases in size to a
48" RCP before connecting with this 54" RCP at Academy
Boulevard. Runoff from subbasin T8 is directed Into these same
pipes vla grated inlets and connecting storm drain laterals.

Drainag'. continues in a 2,300 feet concrete-lined channel which
diverts the flow due west instead of allowing it to follow the
natural PCT draInage flowing southwest. With the exclusion of
subbasins T9 and TIO, the consolidated flow of the PCT basins
Is conv'.yed to the main PC channel through this structure. The
confluence wi th PC is generally referred to as the Chapel Hills
Mall Outfall. The total length of flow from Pond 2 to this
point is approximately 2 miles.

A natural channel exists from the Chapel Hills Mall Outfall to
the confluence with Monument Creek, a distance of 0.7 miles.
Along the way. runoff from subbasin TIO enters the channel via
the historic PCT channel and storm drain outfall points.

Three previous studies have been conducted for the PC/PCT
watershed. They include the FIS -=- Cltv of Colorado Sorings
(Reference 6) and the ~Ineering Study of Cottonwood Creek
Draina&€l BasIn (ESCC) (Reference 21). The stream referred to
as the North Cottonwood Tributary in the ESCC is the same
watercourse beIng referred to as PCT is this study. The latest
work was done under the Pine Creek Drainage Basin Plannin!!:
~tudv (I'CDB) (Reference 22). Drainage details for subbasins T4
and T8 were obtained from the recently completed Master
Develollment Drainage Plan Chall.l Hills Crossin!!: (MDRCH)
(Reference 23).

PreviOUH Studies

The FIS study was based on hydrology developed by the U. S.
Army Corps of Engineers (Reference 10) in 1976. As discussed
earlier (see South Shooks Run), this analysis tended to result
In very generalized estimates of streamflow when applied to
small watersheds.

Both of the other two previous studies (ESCC and PCDB) used
storm parameters specifIed under older DCM guidelines. These
assumed 6-hour storm durations with Type IIA distributions

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