FLOOD10420

• County: Adams
• County: Broomfield
• County: Weld
• Community: Broomfield, Westminster and Thornton
• Stream Name: Lower Big Dry Creek
• Title: Lower Big Dry Creek Hydrology Study
• Date: 6/1/2005
• Prepared For: Big Dry Creek Watershed Association
• Prepared By: Wright Water Engineers, Inc.
• Floodplain - Doc Type: Floodplain Report/Masterplan

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Lower Big Dry ~reek Hydrologic Study

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. In general, the area visited between 1-25 and 160th Ave. is experiencing significant growth
in the form of residential developme~t in Thornton's urban growth area. Additionally,
active road construction in the wasJngton, York, and Highway 7 areas was occUlTing.
Near E-470, roadwork was also beinJ completed. Big Dry Creek northeast ofE-470 also
showed evidence of erosion, as showJ in a photograph where a fence is several feet inside
of an eroded bend in the stream.

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The greenhouses adjacent to Washington Street documented in the first WWE (2:000)
study have been removed. Erosion uJstream of Washington Street was still evident.

In several locations, utilities and oilld gas pipelines were threatened by the accelerated
erosion. Most of the property ownbrs had at least one oiVgas tank surrounded by a
containment berm on their Property.ITWO landowners noted that an oil/gas company had
constructed or provided routine repair:s to their driveway bridges.

In one location, county bridge repail were evident and attributed by one landowner to
damage from last summer's storms.

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6.1 Howard Property

As shown on Figure 8, the Howard family farms a large area in the Big Dry Creek watershed,
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with Big Dry Creek traversing much of their property. Appendix A, Photos 1-21 illustrate and
describe the problems on their property. TJe single most important issue is erosion around the
Y oxall Ditch headgate, which currently Jctions, but it is vulnerable to damage as erosion
continues. For the Howards, control of futur~ flow conditions is particularly important.

During the sommer of 2004 storms, crops ld bay were flooded when the stream flowed out of
its banks. Sand deposits from these flows wJre present in the fields at the time ofWWE's visit.

An exposed gas pipeline was present in 1 area were the str~ambank had eroded, but the
Howards indicated the pipeline was presumeb to be abandoned.

971-179.092
June 2005

Page 44

Wright wrr Engineers, Inc.

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