South Platte River Program Notes
by
Ben Urbonas, P.E., Chief, South Platte River Program

Maintenance Activities

Routine Maintenance
In 2000 the South Platte River routine maintenance included an equivalent of

• 9.1 miles of tree trimming and pruning along the river trail,
• 3.6 acres of string trimming at access ramps and rest areas,
• 78 miles of trail edge mowing, and
• 192 miles of trash and debris pickup and removal along the river.

A total of 160 truckloads of trash and debris were removed from the river and taken to landfills. We continue to study statistical data pertaining to trash and debris accumulation patterns gathered over the past five years, and in 2001 we will further tailor our removal program to maximize results.

For the fourth consecutive year we participated in the Greenway Foundation’s annual NIMBY Fest volunteer trash pickup, during which an additional twelve truckloads of trash were removed. In addition, government personnel and volunteer groups picked up and removed trash from the river corridor throughout the year. Unfortunately, we do not have an estimate of the volume removed by them. Trash is also regularly removed from trash receptacles maintained by park personnel along all recreational trails.

Routine maintenance continues to be the most cost effective program in terms of environmental enhancement and public service. Without it, the trash along and in the river would accumulate. Since it was begun under the South Platte River Program we now have twice the number of yearly trash pickups, mowing of trail edges and invasive weed control than we did 14 years ago. At this level of activity we find the river corridor needs are addressed quite well.

Removal of Undesirable Tree Species
In 2000 the routine maintenance program continued to work with local government agencies to control infestations of non-native and undesirable tree species along the river. In the City of Brighton’s Morgan Smith nature area we removed 133 tamarisk plants and planted 36 cottonwood trees. Working with the South Suburban Park and Recreation District and the City of Littleton, we removed 217 Russian olives from the riverbanks in South Platte Park. In addition, we removed 77 dead and diseased Siberian elms in Denver and another 300 in Adams County. The removal of invasive non-native trees provides the opportunity for native cottonwoods, box elders, willows, and others to become established. These natives in turn provide better habitat for wildlife native to this region.

Restoration Maintenance
In 2000, the restoration maintenance program continued to stabilize, rehabilitate, and revegetate eroded riverbanks, protect exposed utility crossings, and rehabilitate existing structures. The District also assisted local governments with maintaining the recreation trails along the river which are used for maintenance access. In addition, the program restored a vacant lot adjacent to the river.

Over 2000 feet of badly eroded, degraded and trashed out riverbanks were cleaned up, regraded to a gentler slope, protected with buried rock riprap, and revegetated with native grasses, shrubs and Cottonwood trees. These types of bank restoration projects normally comprise the bulk of the restorative maintenance work performed by the South Platte River Maintenance Program.

This year, however, the largest restorative maintenance project buttressed an exposed utility crossing near the plant owned by the Metro Wastewater Reclamation District at 64^th Avenue and York Street. The structure was a major barrier to fish migration and a hazard to anyone boating the river. The drop is now a sloping grouted boulder drop structure approximately 80 feet long. (See before and after photos). It was jointly funded by the District and Metro and not only made the utility crossing more structurally sound, but also provided for safer boater passage and fish migration.

Before and after views of the utility crossing protection project.

At 58^th and York Street in Adams County, a unique opportunity presented itself. A vacant lot adjacent to the river was continually being used and abused by the public. The District was constantly removing trash and debris that had been dumped on this site. Therefore, with the help of Adams County Parks we cleaned up, regraded, and revegetated the lot; and installed bollards along the roadway to limit access and hopefully limit trash dumping. Metro Wastewater Reclamation District pitched in to help restore this site by donating Metro-Gro compost for use as a topsoil amendment.

This year the old wooden pedestrian bridge near Huron Street in Denver was removed and replaced with a 10-foot wide, self-weathering steel bridge with concrete deck. Denver and the District jointly funded this replacement. Icon Engineering and SDG, Inc. were the consultants and Tierdael Construction was the general contractor. The new, wider bridge and improved trail approaches allow for better recreation/maintenance access that now meets ADA requirements. A lane of traffic for one block along northbound Platte River Drive was eliminated as part of this project, providing for a wider riparian area so important to the movement of wildlife.

The project to replace a wooden pedestrian bridge near First Avenue (extended) was delayed again, this time due to the discovery of elevated contaminant levels in the area; a heritage of past industrial practices on adjacent properties. It is now necessary to investigate options for environmental cleanup and different construction alternatives. To summarize, this project has to consider that this bridge replacement project: (1) is within a major river floodway, (2) involves limited channel/trail right-of-way (adjacent to Interstate 25 and a chemical plant), (3) may disturb contaminated soils, (4) must conform to ADA requirements, (5) will require major trail detour during construction, and (6) ask, what's next? We hope to overcome these issues and look forward to this bridge replacement becoming a reality by 2002.

Cooperative Projects with Private Property Owners
Cooperative projects are constructed on flowage and maintenance access easements dedicated to the District by private property owners adjacent to the river in exchange for river restoration work. To date almost 500 acres of these easements have been dedicated, resulting in over 20 bank stabilization and riparian revegetation projects on these properties since 1988. Often, the local park departments use these easements for the construction of recreation trails.

One cooperative project was completed this year and two were designed for construction in 2001. The completed project involved the extension of a series of bendway weirs adjacent to the Ready Mixed Company's gravel pit in Brighton. Seven new weirs were built downstream of five weirs originally constructed in 1997. So far, we are experiencing success with the weir concept at this site and hope to report on its successful operation in the future.

A bendway weir is a low-level, upstream angled rock sill, keyed in to the outer bank of a waterway bend. The weirs help reduce flow velocity and concentration of current along the outer bank of the bend, thus encouraging an eroded bank to "heal" itself. With the weirs in place, the risk of bank failure is significantly reduced. For more information on bendway weirs, the reader is encouraged to visit several articles on the internet by searching on "bendway weirs" or visiting the 1997 issue of Flood Hazard News.

Two additional cooperative projects are planned for 2001. Aggregate Industries, Inc. and Asphalt Specialties, Inc. have both expressed an interest in working with the District in order to fulfill their bank stabilization requirements for mining within 100-year floodplains in Adams County. We hope to complete bank stabilizations along these future sand and gravel pits by the fall of 2001.

Capital Improvement Projects

Upper Central Platte Valley Project
Since last year the pace for this project picked up considerably through the involvement by the City and County of Denver of the U.S. Army Corps of Engineers. The Corps has agreed to do a river restoration project of the Colfax Reach (I-25 to 12^th Avenue) of this project; and has completed the reconnaissance and feasibility studies, and the final design for this reach in record time. The project was bid and is now under construction. It is expected that the work will be completed by Spring of 2002.

Because of certain legal restrictions, Denver and the District could not sign the project cooperation agreement with the Corps. The Greenway Foundation has agreed to do so on behalf of Denver for this project. For subsequent projects Denver will be the signatory for Corps projects within its corporate boundaries. This is because the Corps’ rules that prevented this from happening for the Colfax Reach project have been changed. Much credit for this change goes to the Corps. They took the initiative to find ways that now treat local sponsors in more of a partnership role than before, a trend which we hope will continue.

The Cops has received an authorization to do reconnaissance and feasibility studies for the Zuni and Sun Valley Reaches starting late in 2000. The river restoration work for these two reaches has been estimated to cost $15,000,000 and Corps help to have this plan implemented is much needed. The Corps plans to follow the basic concepts developed for Denver and the District by McLaughlin Water Engineers.

Globeville Area Project
As reported last year, Phases 1 and 2 of this project have been completed, but before the benefits of this work can be fully realized, Phase 3 will have to be built. The design for Phase 3 was completed, but the Farmers Reservoir and Irrigation Company (FRICO) refused to accept the new diversion concept. As a result, we went back to the drawing board and asked Love & Associates to develop an entirely different concept. One was developed that appears to be much more acceptable to FRICO, but the costs have now risen from $7.1M to around $13M and we still need to work out many issues and details before the new concept can be finalized and implemented. One of these is to find the additional moneys to build it. Only 1/3 of the added costs can be attributed to the change in concept. The rest are the result of escalating construction costs in our region during the related delays. Nevertheless, we now need to find another $6M to finalize the Globeville project, not an easy task. Regardless, Denver and the District will continue to pursue implementation in order to provide flood relief for this North Denver neighborhood.

Adams County Master Plan Update
We continue to work with CDM (since 1998) and with Adams County, the cities of Brighton, Thornton, Commerce City, South Adams County Water and Sanitation District and the Denver Water Department to update the South Platte River Major Drainageway Plan through Adams County. Many local, state and federal agencies, as well as many individuals and local organizations, have contributed their ideas toward its development. The Phase A report was completed in 2000 and we expect the Phase B, namely the final master plan, to be completed by spring of 2001. Once completed, this plan will provide the communities of Adams County with a long-term roadmap of how the South Platte River corridor will be preserved and develop.

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