Willow Creek Project Wins Award

The District and project sponsors Arapahoe County and South Suburban Parks and Recreation District won the 1999 Colorado Association of Stormwater & Floodplain Managers (CASFM) Grand Award for Engineering Excellence presented at their annual conference in September. The Willow Creek Project is a multi-faceted project that addresses both the flood control and water quality aspects of stormwater management. It was a joint project between the District’s Capital and Maintenance Programs.

The project is located in Arapahoe County in a natural open space park area. The watershed area tributary to the project site is 8.10 square miles (5184 acres), the 2 year discharge is 1650 cfs and the 100 year discharge is 6100 cfs. The Willow Creek watershed is fully urbanized in the lower half of the basin where the project is located, and is actively being developed in the upper half of the basin (Highlands Ranch area).

The primary purpose of the project was to stabilize the Willow Creek channel and to repair a vertical channel bank approximately 30 feet in height. Through the creativity and willingness of all project sponsors, several bioengineering techniques were used instead of traditional stabilization techniques. During the design phase, an opportunity arose to address water quality concerns, specifically sediment from the upstream watershed. A sedimentation pond was constructed to remove sediment before it reaches the Englewood dam flood pool area. The pond enhances the water quality of the stormwater before reaching the open space area, and it mitigates excessive sediment buildup that repeatedly closed the recreation trail downstream of the project area.


The sedimentation pond during construction (left), soon after completion (center), and after several small events (right)

District Sponsored Project Wins Award

Taggart Engineering Associates, Inc. (TEA) has won the American Consulting Engineers Council of Colorado 1999 Engineering Excellence Award for "Lena Gulch Drop Structure Below Maple Grove Reservoir." The project was sponsored by the District, Lakewood, Wheat Ridge and The Consolidated Mutual Water Company. Other consultants were SDG, Inc., CTL Thompson, EDAW, Inc., and Arrow Engineering and Surveying. The contractor was L&M Enterprises, Inc.

A design was required to replace a failing concrete drop structure and to protect endangered homes in the floodplain below Maple Grove Reservoir. Since the structure was adjacent to Kenneth King’s property, which was certified by the National Wildlife Federation as a Backyard Wildlife Habitat, an environmentally sound solution was required.

TEA relocated the waterway through a 4-stage grouted boulder drop structure with planted riprap banks to dissipate energy and control major floods. The modified stream funnels the wide floodplain through the upstream curved grouted boulder drop crest, falls into a deep stilling pool, then over a lower drop cascade, into a second stilling pool, and then safely transitions to the downstream waterway. The complex grouted boulder and planted rock configurations are designed to achieve flood control, aesthetic, and ecological objectives. What looks like natural rocks and rock outcroppings is actually a complex design to direct flow and dissipate energy.

TEA further developed planted rock and stabilization soil lining techniques. Organic clayey soil fills the rock voids for the full riprap thickness. Plants with substantial root growth were used to act like a natural glue in the rocks and keep water turbulence out during high water, increasing the riprap integrity and allowing the plants to further dissipate energy.

The crest of the drop structure is built on a strong base, interlocking steel sheet piling. Joints are filled with a new sealant that expands upon contact with water, preventing the normal seepage through the piling. Above the gulch, an existing pedestrian bridge has been reset at a higher level for increased capacity.

The project maintains the property’s Backyard Wildlife Habitat status with wetlands and riparian planting including sedges, grasses, bushes, and trees. The Kings participated in the sophisticated landscape plan by planting the berry and fruit bearing trees and bushes which provide food and shelter for wildlife. Chubs, small mouth bass and blue gills have returned with the improved water aeration. Hellgramites (a species dependent on high oxygen content) have been observed here for the first time. The Kings, who are avid bird watchers, have documented 65 different bird species passing through and living in their wildlife habitat.

District Wins Accounting Award

For the eleventh year in a row the District has received a "Certificate of Achievement for Excellence in Financial Reporting" from the Government Finance Officers Association of the United States and Canada. The certificate is presented to government units whose comprehensive annual financial reports achieve the highest standards in government accounting and financial reporting. Congratulations to Frank Dobbins, Chief of Finance and Accounting, for continuing this string of awards.

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