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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Soils throughout the two basins can be defined as well-drained
sandy loams. Those with the highest concentratIons of clay are
located in the eastern subbasins of PC and the western
subbasIns of PCT. These soils fall in the "B" type hydrologic
classification. The remainder of the watershed consists of the
hIghly-permeable "A" type sons.

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Runoff from the PC basin collects in two forks (north and
south) which flow westward for approximately 3 miles before
combining in the PC Channel. This natural channel continues in
a southwesterly direction for 1. 5 miles to State Highway 83.
The remainder of the dIstance to Academy Boulevard (0.9 miles)
consists of manmade channel along the eastern right-of-way of
Interstate 25. After passing under Academy Boulevard, flow
continues through manmade channel (0.6 miles) to the Chapel
Hills Mall drainage outfall (point P8a on Figure 11.1).

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Runoff from the PCT basin is detained at several locations
before being passed on to the main PC channel. Drainage from
subbasins Tl, T2. and TI, all culminate in individual detention
facilities. Pond 2. whIch collects the runoff from subbasin
Tl, is located on what was historically the PCT main channel.
Flow out of this pond is now directed to a 90- inch CMP culvert
that lies under Mirage Drive. The flow from Pond 1, which
collects the runoff from subbasin T2, is also diverted into
this culvert.

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At the IntersectIon of Chapel Hills DrIve and Mirage Drive, the
90-Inch culvert flows southwest under the Chapel Hills Mall
parking lot to outfall into an open concrete channel north of
Briargate Boulevard. This channel starts approximately 750
feet west of Chapel Hills Drive and continues along the north
side of Brlargate Boulevard for 1,650 feet to Academy
Boulevard. Here it enters a 90-inch CSP culvert which carries
the flow 1,000 feet under Academy Boulevard and along Kelly
Johnson Boulevard before outfalllng to a concrete-lined channel
(near point P6 on Figure 11.1).

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Runoff from suhhasln T3 flows into a small pond which provides
little to no detention capability before being discharged to an
open channel flowing southwest through subbasin T7. This
natural channel becomes concrete-lined before being diverted
southeast to Jamboree Drive at a point approximately 900 feet
northeast of Academy Boulevard. It enters an 83-inch by 128-
inch elliptical CMP culvert which flows under Jamboree Drive
and the Chapel Hills Mall parking lot for 275 feet. At this
point, It is joined by an 84-Inch CSP culvert flowing southwest
from the upper reaches of subbasIn T6. It is assumed that this
culvert collects storm runoff from the neighborhoods of the
northeastern portion of subbasin T6.

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Combined flow of these two culverts continues southwest
approximately 550 feet through a 108-inch CSP culvert to
outfall into a concrete-lined channel. This carries the flow

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R€~OURC€ CON~UlTI\NT~ INC

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