October 2021 - Plaster Reservoir Management Plan Update

CLOSED: This discussion has concluded.

In 2020, Broomfield engaged Smith Environmental and Engineering (SMITH) to develop a reservoir management plan that outlined an approach to the maintenance of Plaster Reservoir. The impetus for the project was the odor complaints that Parks and Open Space & Trails had received in the past from residents who live around the reservoir.

The management plan consisted of three phases: Data Gathering, Public Engagement and Development of Recommendations. The Data Gathering phase consisted of field measurements of flood storage capacity, an assessment of ecosystem health through the observation of vegetation and wildlife as well as the review of water quality data, and the observation of existing passive recreation opportunities. The Public Engagement phase included a public open house, and two presentations to the Open Space and Trails Advisory Committee (OSTAC) for their review and input.

Finally, the Development of Recommendations phase was divided into four improvement type categories: flood capacity, ecological, water quality, and passive recreation recommendations. These recommendations were divided into three phases. Phase 1 issues were deemed high priority and were planned to be addressed beginning in 2021, Phase 2 issues could be completed when staff and budget allowed, and Phase 3 issues were noted to be implemented only after reservoir dredging, if this was deemed necessary. Recommendations are summarized in the table below:



FC1 – Update Floodplain Analysis

Phase 1: Pursue if recommendation FC2 does not move forward.

FC2 – Dredge to Existing Capacity

Phase 1: flood capacity impact is uncertain, but the issue may be significant.

FC3 – Regular Sediment and Capacity Analysis

Phase 3: routine bathymetry and LIDAR analysis was just completed in 2020.

E1 – Vegetating the North Shoreline

Phase 3: would provide ecological benefit, but the riprap is currently functioning for erosion control

E2 – Shrub Plantings

Phase 3: action would enhance local ecosystem, but may be disrupted by dredging

E3 – Seedling Plugs in

Saline Areas

Phase 3: action would enhance local ecosystem, but may be disrupted by dredging

E4 – Turtle Basking


Phase 2: action would enhance local ecosystem and could be easily moved or removed to accommodate dredging

E5 – Bee Boxes

Phase 2: action would enhance local ecosystem and would not interfere with other activities

E6 – Osprey Platform

Phase 3: best implemented after dredging to avoid seasonal disturbance restrictions on nesting raptors

E7 – Cattail Management

Phase 1: identified by the public as a high priority issue

WQ1 – Annual Monitoring Program

Phase 1: provides critical baseline data and should be resumed in spring 2021

WQ2 – Algae and Aquatic Weed Treatment

Phase 1: issue identified by the public, annual assessments and treatments as needed should be scheduled

WQ3 – Phosphorus


Phase 2: identifying the source of the elevated phosphorus will allow targeted management, if necessary

R1 – Educational Signage

Phase 3: permanent placement recommended after dredging activities

After completion of the Plaster Reservoir Management Plan, SMITH, the management plan consultant, was subsequently asked to provide a scope of work to begin to address Recommendation FC2 for Broomfield to better understand the scale of excavation being recommended (and associated costs) and to better understand some of the externalities that would be associated with the construction. This scope of work included:

  • Detailed topographic survey and recalculation of the existing flood storage capacity,

  • Alternatives analysis evaluating the possibilities for construction access,

  • Preliminary excavation plan to meet live storage capacity requirements,

  • Opinion of probable construction cost,

  • The 100-year inundation areas pre- and post-excavation,

  • Visual inspection of outlet structure and report by a structural engineer, and

  • A hydraulic analysis of existing and proposed conditions.

Broomfield conducted an internal review of the above listed items and determined that moving forward with excavation of the reservoir at this time was not in the best interest of the community for the following reasons:

  • Without additional modeling, benefits of increased flood storage capacity are unclear,

  • Based on the current hydraulic/hydrologic model, no surrounding structures would be inundated in the current condition, so no benefit to structures immediately surrounding the reservoir would be achieved,

  • Disruption to surrounding residents for excavation activities would be significant, with an estimated 1,200 to 1,400 truck trips during construction,

  • Excavation was estimated to cost between $1.2 and $1.5 million, and

  • Ecological disruption would be significant, and would require extensive restoration, likely over several years to re-establish pre-construction conditions.

Broomfield has requested instead that the Mile High Flood District (MHFD) add the Quail Creek and Plaster Reservoir Floodplain and Open Space Areas to their Five-year Master Drainage Plan (MDP) Studies list to develop appropriate maintenance activities and schedules as well as re-evaluate tributary area and floodplain extents. This approach allows for greater collaboration, coordination, and potential cost-sharing with communities located downstream. The strategy also brings the project into the overall MHFD master planning efforts.

Broomfield staff has determined that with no dredging planned in the foreseeable future, all other recommendations may be evaluated for programming into Parks and Open Space & Trails maintenance activities, subject to available budgets. The City and County of Broomfield has developed a draft operations plan for Plaster Reservoir that will be presented to OSTAC on October 28, 2021 for their review and comment.

Share October 2021 - Plaster Reservoir Management Plan Update on Facebook Share October 2021 - Plaster Reservoir Management Plan Update on Twitter Share October 2021 - Plaster Reservoir Management Plan Update on Linkedin Email October 2021 - Plaster Reservoir Management Plan Update link


Thank you to all that participated in the creation of the the Plaster Reservoir Open Space Management Plan.  You can learn more about the history of this project, how community input shaped the guiding principles of this plan and the plan itself by reading below. 

<span class="translation_missing" title="translation missing: en-US.projects.blog_posts.show.load_comment_text">Load Comment Text</span>