Malloy Drain Phase 2B

In 2017, following consecutive flooding events from extreme precipitation that impacted both private property owners and public infrastructure, the Town of Coaldale, in partnership with Lethbridge County and the St. Mary River Irrigation District (SMRID), initiated Phase 2B of a three-phase Project Implementation Plan for the Malloy Drainage Basin. The Malloy Drain 2B Project will provide approximately 380,000 m3 of stormwater storage in South Coaldale by repurposing abandoned raw water reservoirs to provide a 280,000 m3 of storage. Additionally, a new stormwater management facility (SWMF) with wetland components will be constructed south of the Town of Coaldale, with approximately 100,000 m3 of storage, which will limit the flow of stormwater into the Town and to the repurposed reservoirs. A new 1.0 m3/s bioswale with a pump station will direct the stormwater from the newly constructed south SWMF and into the repurposed reservoirs. Given the large geographical scope and scale of the impacts, strong partnerships and tri-lateral agreements were necessary to prompt the initial Project Implementation Plan. Developing a rigorous project vision and mandate were key to ensuring success beyond political and geographical boundaries.

Identifying Actions

The Malloy Drain 2B Project is part of the following Malloy Drain Three Phase Implementation Plan prepared by MPE Engineering in 2014:

  1. Phase 1 (completed in 2016): Rehabilitate 3,700m of Malloy Drain, including two rural road crossings and the Highway 512 crossing.
  2. Phase 2 A & B (in progress): Redeploy the abandoned raw water reservoirs in the Town of Coaldale and provide stormwater storage around Coaldale.
  3. Phase 3 (TBD): Rehabilitate 5,300m of Malloy Drain, including three rural road crossings and the Highway 3 crossing.

To prevent significant flooding the Malloy 2B Project will provide approximately 380,000 m3 of storage in South Coaldale as described below:

  • The Town’s abandoned raw water reservoirs, with an available storage volume of 520,000 m3, will be repurposed to provide a 280,000 m3 additional stormwater storage for this project. The reservoirs are located in the southeast part of the Town of Coaldale and can be repurposed for stormwater storage with minimal improvements and cost.
  • A new stormwater management facility (SWMF) with wetland components will be constructed south of the Town of Coaldale, with approximately 100,000 m3 of storage that will limit the stormwater flow into Town and to the repurposed reservoirs.
  • A new 1.0 m3/s bioswale with a pump station will direct the stormwater from the newly constructed south SWMF and into the repurposed reservoirs.

Implementation

Land acquisition for the Malloy Phase 2B Project is currently being finalized, and a complete preliminary engineering update will be provided to current project stakeholders and to ultimately kick start construction in 2023. Future additions to previous phases may also include a bike path and wetland park for public access. By providing storage south of Town and in the reservoirs, this project will protect the Town residents and Town, County and SMRID infrastructure. Just as Malloy 2B will provide flood protection against incoming rural stormwater flow to the south, Malloy 2A provided similar protection against rural stormwater flow from the west.

Outcomes and Monitoring Progress

The current focus is on completion of phase 2. The timing and funding of phase 3 and beyond will likely need to be more closely examined and re-assessed by all stakeholders soon. Given the large geographical scope and scale of the project, and the number of partners involved, several ‘lessons learned’ were identified:

  • Develop a rigorous project vision and mandate that would ensure success.
  • Project phases should be decided by science and engineering, not politics.
  • Project design should incorporate value-added elements wherever possible.
  • Ensure flexibility within budgets.
  • Keep your eyes on the horizon as a way to avoid the pitfalls of group work “sea sickness”.
  • Above all, collaboration is “a choice that one consciously makes to practice; it doesn’t appear magically; it is, more than anything else, a matter of the will”.

Next Steps

Project stakeholders are re-visiting the overall status of the Malloy Drain Master Drainage Plan and implementation plans in conjunction with the design and construction of Malloy 2B.

Resources

Link to original case study

Additional Resources: