Agenda Date: 11/17/2020
Subject:
Title
Resolution 75-2020: Approving an intergovernmental agreement with Mile High Flood District regarding final design, right-of-way acquisition, and construction of drainage and flood control improvements for Jackass Gulch at Highline Canal
Body
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Prepared by: |
Carolyn R. Roan, Water Resource Manager |
PURPOSE:
Does Council support an agreement with Mile High Flood District (MHFD) to design and construct drainage and flood control improvements along Jackass Gulch, from the Highline Canal to Jamison Way?
PRESENTATIONS:
Staff Presenter(s): N/A
Additional Presenter(s): N/A
SUMMARY:
Jackass Gulch has been actively eroding and sending sediment to the South Platte River for many years. Residents along Jamison Way were increasingly concerned as the creek eroded closer to their homes. South Platte Park was concerned about sediment entering the South Platte River where recent river restoration had occurred, because sediment negatively impacts the cobble substrate and fish habitat in the river. These factors led to a 2017-2018 project to stabilize that reach of the gulch behind Jamison Way.
Significant erosion still occurs upstream of the Jamison Way project. There are approximately 20’ tall vertical or overhanging channel banks, fallen fence lines, and active erosion. This continues to generate a significant amount of sediment in flowing water. Sediment (of unnatural amounts) is considered a pollutant in stormwater. It can carry naturally occurring phosphorus which has a regulated Total Maximum Daily Load (TMDL) in the South Platte River, has negative impacts on fish habitat, and its deposition downstream reduces channel and flood capacity.
Jackass Gulch has improvements described in a 1990 Master Plan Report by MHFD including stabilization and flood detention in this area. Some of the property is city-owned open space and other portions are in public drainage easement on private property. The City and MHFD are currently updating this master plan and floodplain delineation for Jackass Gulch. This study will better inform design of stabilization of the channel, and locations for ponds that provide flood detention and storm water quality improvement.
An open space park with water engagement and additional trails at this location would provide additional recreation opportunity, connecting existing elements such as the Mineral Trail, Highline Canal trail, and Writer’s Vista Park. The city recently received grant funding from Arapahoe County Open Spaces for design of the city-owned portions of the project. The project is supported by South Suburban Parks and Recreation District, the Highline Canal Conservancy, and surrounding homeowners’ associations.
In addition to the grant funds, this agreement would encumber additional funds from the city and MHFD. It is expected that this would be a multi-year agreement with amendments each year until total funding needs are reached. Partnerships with MHFD’s capital improvement program require a 50% cost match from the local jurisdiction.
PRIOR ACTIONS OR DISCUSSIONS:
City council approved the pursuit of grant funding for this project on May 5, 2020 (Resolution 40-2020). After the grant was awarded, City Council approved the Intergovernmental Agreement with Arapahoe County for this project on August 18, 2020 (Resolution 56-2020).
ANALYSIS:
Staff Analysis
Stabilization of Jackass Gulch has been planned by staff for many years and has recently become a priority due to rapidly degrading conditions and increased resident concerns. The initial project (along Jamison Way) was a partnership with MHFD in 2017 to address the erosion that was threatening adjacent homes. Continual erosion in the creek, upstream of that 2017 project is a large concern of residents who are losing their property to the erosion. The erosion presents safety risk, being located next to a regional trail (Mineral Trail). There is a water quality concern as excessive sediment reaches downstream to the South Platte River. In addition, there are potential flooding issues located farther downstream that might benefit from flood detention provided with this project.
Council Goal, Objective, and/or Guiding Principle
This project meets Goal 2-Financial Sustainability, Objectives 3 and 4 by identifying a long-term capital need and identifying funding sources. This project also meets Goal 3-Good Governance, Objective 3 by leveraging funding assistance and strategic partnerships with Mile High Flood District and Arapahoe County.
Fiscal Impacts
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City 2020 contributions: |
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Grant funds (Arapahoe County Open Spaces) |
$97,110 |
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City storm drainage fund (grant cost match) |
$10,790 |
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City storm drainage fund |
$67,100 |
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Total |
$175,000 |
50% |
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Mile High Flood District 2020 |
$175,000 |
50% |
Alternatives
Should this agreement not be authorized by City Council, the project design and construction cannot commence, and the city would lose the pledged matching funds from Mile High Flood District for 2020. The environmental and safety issues associated with the erosion would continue to worsen.
STAFF RECOMMENDATION:
Staff has placed a priority on addressing the erosion and flooding concerns along Jackass Gulch and supports this agreement with Mile High Flood District to leverage and maximize available funding sources.
PROPOSED MOTION:
Proposed Motion
I move to approve the resolution approving an intergovernmental agreement with Mile High Flood District regarding final design, right-of-way acquisition, and construction of drainage and flood control improvements for Jackass Gulch at Highline Canal.