MAINTENANCE PROGRAM ACTIVITIES

by
Mark R. Hunter, P. E.
Chief, Maintenance Program

Routine Maintenance

Through the routine program $490,000 was spent in 1996 for mowing and debris pickups on approximately 210 different sections of drainageways within the District boundaries. This equates to a total of nearly 100 miles of drainageways in the Denver area that were given routine maintenance.

Some of the drainageways we maintain are quite urbanized with adjacent homes, streets, and improved parks. In recent years we have responded to numerous requests to increase the number of mowings we do per year in the more urbanized areas. Other drainageways we maintain are more rural in character. On portions of some of these more rural drainageways we have taken the opportunity to reduce or eliminate our mowing activities. This has been done to encourage habitat and leave a more natural character in the corridor.

Restoration Maintenance

In 1996 the restoration program completed $1.02 million of work. Restoration projects typically address isolated drainage problems where the solution involves small scale construction. Seventy-eight individual activities were completed during the year.

Lena Gulch discharges into Clear Creek on the east side of Kipling Street at 41st Avenue in Wheat Ridge. The final 300 feet of Lena Gulch is parallel to and lower than the Clear Creek channel. Through natural forces Clear Creek captured or took over that 300 feet of Lena Gulch. The result was that Clear Creek abandoned a portion of its previous channel and its water flowed in the captured portion of Lena Gulch along with the water of Lena Gulch. This was certainly a natural process, but in an urban area the results were undesirable. Clear Creek water backed up approximately 500 feet above the capture point in the Lena Gulch channel. A pedestrian bridge was occasionally under water. Mosquitoes were more common and uncontrolled vegetation was evident. The Lena Gulch trickle channel was completely submerged under a 50 foot wide pool of slow-moving water.

In early 1996 the maintenance program regraded part of the confluence area to put Clear Creek back in its channel. We also cleaned the sediment out of the Lena Gulch trickle channel and tilled and revegetated the area that had been under water. Our efforts were short lived. With the spring runoff in 1996 Clear Creek recaptured Lena Gulch and the pool of slow-moving water returned.

We continue to spend money to treat the symptoms of this natural process. At the same time we are approaching the appropriate parties to put together a project to solve the larger problem of stabilizing the channel of Clear Creek.

Rehabilitation Maintenance

Twenty-seven projects were at various stages of design or construction during 1996. Those projects are listed in the accompanying table titled "STATUS OF MAINTENANCE REHABILITATION PROJECTS". Rehabilitation projects usually take the form of consultant-designed repairs that are intended to address severe problems that have occurred on a previously improved drainageway. By the end of 1996 the District will have spent about $2,826,000 on rehabilitative design and construction for the year. A few of the unique projects are discussed below.

Since we reported on it last year our project on Westerly Creek immediately south of the Stapleton Airport site in Aurora has been on hold due to right-of-way considerations. The good news is that the right-of-way issues have been resolved and the project is now out for bid. The project still calls for replacing a collapsing 60" pipe with an open channel. This small project area will ultimately be part of the Westerly Creek "green" corridor serving the neighborhoods around the old Stapleton Airport.

Deteriorated and collapsing pipes under a road in Adams County have given us the opportunity to repair portions of Niver Creek near the South Platte River. By cooperating with Adams County in funding the project the deteriorated pipes which now carry Niver Creek will be replaced with a bridge and an open channel. An adjacent section of the creek will also be rehabilitated. It will be widened width and more accessible side slopes. If enough land can be acquired the county is also considering expanding the Niver Creek trail-head park.

We have another project this year that calls for replacing an existing pipe system with an open channel grass-lined drainageway. West Harvard Gulch flows through a linear park in Englewood on the west side of the South Platte River. Base flows and small storm events are carried in a 60" pipe that runs beneath the park. The pipe is badly deteriorated. The 2600 linear feet of pipe will be removed and replaced by a new open channel and two drop structures. Once construction is completed all runoff will flow on the surface through the linear park.

In last year's Flood Hazard News we reported that a landscape architect was the prime consultant for a project on Airport Creek at 112th Avenue and Harlan Street in Westminster. Construction has now been completed on this project to correct localized aggradation and degradation. The wide drainageway corridor permitted the consultant to take advantage of the gently graded open space to design the drainage repairs and incorporate some aesthetic features. Cook Park is also on Goldsmith Gulch and is one and one-half miles downstream from Bible Park. It is in the City of Denver and is immediately east of Monaco Parkway where Goldsmith Gulch joins Cherry Creek. The erosion in the low flow channel in Cook Park has created a steep-sided channel that is three to six feet

The heavy spring runoff in 1995 severely damaged a drop structure and about 100 feet of gabion bank protection on Lena Gulch. The site is downstream from the Consolidated Mutual water treatment plant at 27th Avenue in Lakewood. Construction of a new grouted boulder drop structure and adjacent features has recently been completed. Rebuilding this facility was possible because of the cooperation of the City of Lakewood, the City of Wheat Ridge, Consolidated Mutual Water Company, the capital and maintenance programs of the District, and the adjacent property owner.

Bible Park is located on Goldsmith Gulch between Yale Avenue and Dartmouth Avenue in Denver. Within Bible Park the drainageway flows through an area of natural grassed and volunteer trees and shrubs. Through this area the low flow channel for Goldsmith Gulch has eroded into a vertical-sided channel ranging from three to ten feet deep. The design process is well under way with representatives from nearby neighborhoods, the Denver parks department, the consultant and the District maintenance program contributing to the partnership. The goal of the project is to repair the erosion damage to the channel and, at the same time, to make the gulch a more accessible and aesthetic component of the natural area of the park.

Cook Park is also on Goldsmith Gulch and is one and one-half miles downstream from Bible Park. It is in the City of Denver and is immediately east of Monaco Parkway where Goldsmith Gulch joins Cherry Creek. The erosion in the low flow channel in Cook Park has created a steep-sided channel that is three to six feet deep. Although this is not as severe as in Bible Park the setting in Cook Park is an improved blue-grass multi-use area. This dictates that the channel configuration for Goldsmith Gulch be rehabilitated to be less of a threat to existing facilities such as pedestrian bridges and play areas. It also means that visitor safety and convenience will be a component of the design. The design for this project has just begun. As with Bible Park, the design of maintenance repairs to Goldsmith Gulch through Cook Park will incorporate the contributions of the neighborhood representatives and the participating governmental departments.

Barnum Lake on Weir Gulch at Federal Boulevard and 6th Avenue has filled in with so much sediment over the years that it now has an average water depth of nine inches. The lake serves primarily as a natural habitat area and a stormwater detention pond. By its location it inevitably serves as a sediment trap. The Denver Parks Department is designing a project to remove the accumulated sediment and restore the lake to an area and a stormwater detention pond. By its location it inevitably serves as a sediment trap. The Denver Parks Department is designing a project to remove the accumulated sediment and restore the lake to an attractive wildlife habitat. Plans also include nature trails and fishing stations on the banks of the lake. The maintenance program can participate in this project at two levels. Any sediment that is within the stormwater detention volume of the lake qualifies for maintenance of a flood control facility. The maintenance program can fully fund the removal of sediment that occupies some of the designed detention volume. Any sediment that is trapped within the permanent pool of the lake does not impact detention volume but does serve to improve the quality of the stormwater in Weir Gulch. The maintenance program will fund a part of the removal of this portion of the sediment recognizing that improved water quality is a long-term benefit to the function of the drainageway.

Another District Award

The District, Wright Water Engineers, and L & M Enterprises received a Certificate of Recognition from the International Erosion Control Association for a project on Lena Gulch downstream of Youngfield Street. The project had been nominated for an Environmental Excellence Award in the Design Category. The project consisted of 1500 lineal feet of boulder walls and riprap stabilized channel bottom featuring several unique landscape accents; a grouted boulder drop structure with stilling basin, tree protection designs, and a modified wall section to allow for pedestrian access to the channel bottom. Congratulations to David Bennetts from the District, Wright Water, and L&M Enterprises.

STATUS OF MAINTENANCE REHABILITATION PROJECT

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