Last Mountain Lake National Wildlife Area Water Control Structure Re-naturalization Project

Environment and Climate Change Canada and Transport Canada must determine whether the proposed re-naturalization of waterbodies through removal of water control infrastructure within Last Mountain Lake National Wildlife Area,  Saskatchewan, is likely to cause significant adverse environmental effects. To help inform this determination, Environment and Climate Change Canada and Transport Canada are inviting comments from the public respecting that determination. All comments received will be considered public and may be posted online. For more information, individuals should consult the Privacy Notice https://iaacaeic.gc.ca/050/evaluations/protection on the Registry website. Written comments must be submitted by August 28, 2024 to:

Kerry Hecker

Wildlife Area Manager

Last Mountain Lake National Wildlife Area and Migratory Bird Sanctuary

Environment and Climate Change Canada

Box 280, Simpson SK. S0G 4M0

Kerry.hecker@ec.gc.ca

 

Jackie Barker

Regional Environmental Advisor, Environmental Programs, Prairie and Northern Region

Transport Canada / Government of Canada

jackie.barker@tc.gc.ca

 

The Proposed Project

 

The Last Mountain Lake (LML) National Wildlife Area (NWA), located at the north end of Last Mountain Lake contains several Ducks Unlimited Canada (DUC) wetland projects that are co-managed with the Canadian Wildlife Service.  Construction of water control structures dates back to the 1960's and several structures received upgrades in 1986 to ensure they remained in a functional state.  DUC intends to return wetland areas within the LML NWA to its pre-construction status.  Four projects located within the NWA (Saline Creek Diversion control, LML Basin- B-1 Inlet structure, LML Basin D outlet control, LML Basin E outlet control) will have previously constructed earthworks and structures modified to a naturalized condition.

 

Shields Project comprises of water control structures that were originally constructed in 1955/56 and included a 243-m dam and a concrete control which created a 136-ha wetland. The proposed plan to re-naturalize includes:

  • Remove the concrete control (2-Bay Concrete weir with 2-2.7-m stoplog bays)
  • Remove existing dam and construct a naturalized control section through the dam footprint using on-site rock which will be designed to convey projected flows.
  • Remove A-1 to Saline Creek diversion dyke and fill ditch

 

Last Mountain Lake Extension, Basin A-1, B-1 was constructed in 1985 and designed to flood 72.4 ha (A-1) and 34.5 ha (B-1). The proposed plan is to re-naturalize the project and remove existing controls, includes:

  • Remove E-W grid road control and replace with a culvert
  • Breach the main dyke (Dyke A-1, adjacent to Lanigan Creek) in four locations to connect basin A and A-1 (total of 784.44 m3 of fill to be removed)

 

Last Mountain Lake, Basin B was constructed in 1970 and is a 8.9-ha natural wetland that receives local inflow from Basin B-1 when required to supplement local runoff.  The existing inlet control culvert (1200 mm x 12 m CMP in concrete headwall with stoplogs) will be replaced with a through pipe.

 

Last Mountain Lake, Basin C was constructed in 1970 and is a 113.1-ha wetland controlled by Dam C and two control structures. Proposed naturalization of this project includes:

  • Breach Dam C for a 300-m length
  • Re-naturalize Ditch C-E by removing control structure (1200 mm x 12 m CMP with modified end section) and filling ditch
  • Remove a temporary culvert that was installed in 2023

 

Last Mountain Lake, Basin D was constructed in 1970, and is 74 ha wetland controlled by a control structure and dam which also functions as a crossing in the LML NWA road system. The existing structure (600 mm x 24 m CMP in concrete headwall with 20-10C gate) will be removed, dam breached and replaced with a through pipe to allow for unrestricted fish passage between basins.

 

Last Mountain Lake, Basin E is a 37.4 ha wetland constructed in 1970. Water levels are controlled by a control structure and Dam E which also functions as a road crossing in the LML NWA road system. The existing structure (600 mm x 19 m CMP in concrete headwall with stoplogs) will be removed, dam breached and replaced with a through pipe to allow for unrestricted fish passage between basins.

 

All areas disturbed by construction activities will be stabilized (as necessary) and seeded with a native vegetation mix. Decommissioning will strive to mimic natural pre-project conditions as closely as possible and facilitate natural succession at the site.

 

This project will require approval under Canadian Navigable Waters Act.  ECCC is responsible for Issuing a National Wildlife Area permit.

More

Latest update

The assessment is in progress.

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Key documents

Key documents
Document Number Document Title File Date
1 Notice of Intent to make a Determination - Start of Public Comment Period - July 26, 2024

Contacts

Last Mountain Lake National Wildlife Area
Environment and Climate Change Canada, Canadian Wildlife Service
Kerry Hecker, Protected Areas Manager
PO Box 280
Simpson, Saskatchewan S0G 4M0
Telephone: 306-836-2022
Fax: 306-836-2010
Email: kerry.hecker@ec.gc.ca


  • Location

    • Last Mountain Lake National Wildlife Area (Saskatchewan)

  • Nature of Activity

    • Water Management
    • Remediation and conservation

  • Assessment Status

    In progress

  • Start Date

    2024-07-26

  • Proponent

    Ducks Unlimited Canada

  • Authorities

    • Environment and Climate Change Canada
    • Transport Canada

  • Assessment Type

    Project on federal lands

  • Reference Number

    88755
Disclaimer

This map is for illustrative purposes. The markers represent the approximate locations based on available data. More than one marker may be identified for a given assessment.

 
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