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Boxelder Stormwater Master Plan Elements



The Boxelder Creek Watershed represents a vast, relatively undeveloped part of northeastern Larimer County. The drainage basins that make up the watershed cover approximately 260 square miles and extend from southeast Fort Collins north into Wyoming. The entire Town of Wellington, a portion of the City of Fort Collins, and areas adjacent to the towns of Windsor and Timnath are included in this watershed. The lower portion of the watershed is more urbanized and is impacted by many existing man-made structures such as irrigation canals and culverts. Floodplain In-Service Area.

To help mitigate the extensive flood hazard within the portion of the Boxelder Watershed being called the Proposed Service Area, the project partners pooled funds and hired an engineering consultant to study the problem and propose solutions. After an extensive public process, a recommended alternative for regional improvements was selected. The improvements would be phased, with construction to start on the upstream projects first, to achieve the greatest benefit as quickly as possible. Project Locations

Phase I Improvements (1-5 Years)

  1. Clark Reservoir Storage Detention, Coal Creek Diversion

This will remove properties from the Coal Creek floodplain from south of CR 70, through the Town of Wellington and lessen the probability of damages in areas south of the town. The elements of this project include:

  • Improvement of the North Poudre Canal to capture and convey Coal Creek flood flows into the existing Clark Reservoir
  • Culvert crossings associated with the North Poudre Canal
  • Dredging of Clark Reservoir to provide for additional storage
  • Associated right-of-way acquisition
  • Spillway and outlet works improvements to Clark Reservoir
  • Agreement associated with flood storage capacity within reservoir

Regional Benefits:
Reduces peak discharges downstream (approximately 90% in Coal Creek: 5-10% in Boxelder Creek) due to increased capacity in Clark Reservoir).

Local Benefits:
Reduces floodplain extents by approximately 150-215 acres; minimizes flooding potential and damages for approximately 180 structures (including 2 schools, community center, residential and commercial structures)
  1. Edson Stormwater Detention Facility

Edson would be a dry stormwater detention basin located on Indian Creek. There are numerous possible sites with the intent that the final location provides sufficient storage while benefiting adjacent landowners.

The Edson Stormwater Detention Project would require construction of an earthen embankment and un-gated outlet to impound approximately 660-990 acre-feet of stormwater runoff on Indian Creek during a 100-year flood. There are a number of possible sites for Edson. The Master Plan suggests choosing a site upstream of County Road 60 in order to provide flood mitigation benefits to the largest area, but others may work equally as well, or better.

Regional Benefits:
Detention storage of floodwater in Edson Facility will reduce peak discharges downstream (approximately 40-60%). It will also reduce the size of required downstream conveyance improvements. It reduces the area in the floodplain and potential for downstream split flows.

Local Benefits:
Minimizes flooding potential and damages to approximately 165 existing structures within Larimer County and the City of Fort Collins (in conjunction with other improvements).
  1. Middle Boxelder Creek Stream Improvements
  • Improvements to the Middle Boxelder Creek from CR54 to CR52
  • Construction of two storm drainage channels to direct flow to Boxelder Creek
Regional Benefits:
Potential trail and recreational opportunities.

Local Benefits:
Reduces potential for overflow and split flows adjacent to I-25 and impacting Cooper Slough; removes approximately 535 acres of the Boxelder Overflow (in conjunction with upstream detention)

Phase II Improvements (3-8 Years)

Phase II improvements include:
  • Construction of a siphon structure along the Larimer and Weld Canal at Boxelder Creek to reduce overtopping;
  • Construction of an I-25 Split Flow Diversion Channel that would protect CR 42E and remove approximately 300 additional acres from the floodplain;
  • Improvements to Prospect Rd west of I-25;
  • Construction of a spillway structure on Boxelder Creek and a channel to the Cache la Poudre River.

Phase III Improvements (5-15 Years)

Phase III includes:
  • Middle Boxelder Creek road crossing improvements; and
  • Cooper Slough/Mulberry Street and Lake Canal improvements.



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