|LARIMER COUNTY BOXELDER STORMWATER INFORMATION||BOXELDER STORMWATER |
Flood Mitigation Project
The Boxelder Creek Watershed represents a vast, relatively undeveloped part of northeastern Larimer County. The drainage basins in this watershed cover approximately 260 square miles and extend from southeast Fort Collins north into Wyoming. It contains some of the best agricultural land in the County.
Close to I-25, the area has developed into an agribusiness and agri-research corridor which includes a major brewery, the Colorado State University Horticultural Research Center, and the Colorado State University Agricultural Research, Development, and Educational Center.
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.
The Boxelder Creek Watershed has a long history of flooding. A Soil Conservation Service report documents that in a 65 year period from 1904-1969, on average there was a damaging flood every 1-3 years somewhere in the watershed. In addition to the 24 major storm events documented within this timeframe, there were numerous localized storms occurring over the irrigated land causing flooding, sediment and erosion damages as well.
In 1947, a Coloradoan newspaper headline read, "Violent Rainstorm Floods Large Area; Crop Losses Heavy." In this storm, as much as five inches of rain fell northwest of Wellington, damaging nearly 1,000 acres of grain, alfalfa and corn as well as washing out bridges.
In 1967, heavy rains again flooded the area, causing Boxelder Creek to overtop roads which resulted in the death of a mother and her three daughters on a county road southeast of Wellington. Seven times that summer county bridges in the Watershed were destroyed by flooding.
Since 1976, the Boxelder Creek Watershed, along with other parts of Larimer County, has been included in the National Flood Insurance Program. As part of that program, Larimer County, the Town of Wellington, and the City of Fort Collins must regulate land uses in the FEMA designated floodplain. More than 5,000 acres of land in the Boxelder Creek Watershed are in the floodplain.
For individuals, this means that if their house was previously built in what is now designated as a floodplain, they could be prohibited from adding on to their house, building a garage, or making substantial improvements. They might even be restricted in a landscape design change.
For farmers and ranchers, a floodplain designation might restrict where a farmer can park his equipment, or a rancher may place a loafing shed.
Flooding concerns in the Boxelder Creek Watershed can impact property values and result in mandatory flood insurance requirements. With approximately 5,000 acres of this watershed located in the floodplain, this is a significant issue for many residents.
Flooding affects everyone, not just the residents directly located in a floodplain. In the event of a flood on Boxelder Creek, the following may occur:
In addition to the hundreds of homes located within the current floodplain boundary, there are two schools, two gas stations, a liquid propane storage facility, numerous business and commercial facilities, sanitary sewers, electrical lines, water transmission lines and other critical infrastructure that could be impacted or damaged. Access to an electrical substation could be cut off in a major storm event and over 18 detention ponds and irrigation storage reservoirs, 4 irrigation canals, and 30 roads are predicted to overtop and likely be damaged during the 100-year flood event.
In early 2005, stormwater engineers from various entities began studying stormwater and drainage needs in the area. The group consisted of representatives from Larimer County, Town of Wellington, City of Fort Collins, Town of Timnath, Town of Windsor, North Poudre Irrigation Company, Boxelder Sanitation District, New Cache La Poudre Irrigation Company, Colorado Water Conservation Board, and a private property group.
The group completed a Stormwater Master Plan for a portion of the Boxelder Creek Watershed (consisting of those lands tributary to Boxelder Creek, extending from County Road 70 north of Wellington, south about 12 miles to those areas where Boxelder Creek floodwaters join the Cache La Poudre River.)
The Master Plan focuses on the concept of storing floodwater within higher portions of the Service Area and releasing it slowly so that no damage is done as it flows downstream.
To help mitigate the extensive flood hazard within the portion of the Boxelder Watershed (called the 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 occur over time, 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)These improvements will be completed through the newly created Boxelder Stormwater Authority.
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 project is being designed and constructed by Larimer County on behalf of the Authority. The elements of this project include:
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)
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.
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).
Potential trail and recreational opportunities.
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)
These improvements are not a part of the Stormwater Authority projects.Phase II improvements include:
Phase III Improvements (5-15 Years)
These improvements are not a part of the Stormwater Authority projects.
Implementation of the regional improvements listed in the adopted Master Plan will be overseen by the Boxelder Stormwater Authority, a new separate governmental entity, created through intergovernmental agreement among Larimer County, the Town of Wellington, and City of Fort Collins. The Authority, or local entities on behalf of the Authority, will design, construct, operate, and maintain the improvements.
Funding to build and maintain these facilities will come from state and federal sources (including a $3 million dollar federal grant), a one-time development fee for new buildings or developments, and a stormwater user fee charged each year to owners with developed property within the Service Area of the Boxelder Drainage Basin.
It is anticipated that the first regional project, the Coal Creek Flood Mitigation Project, will be constructed in 2011.