Agriculture and Irrigation - Request for Proposal - Lethbridge Northern Headworks Operations and Monitoring- 2025

Background: The Lethbridge Northern Headworks canal begins within the Piikani Reserve near Brocket approximately 16 km west of Fort MacLeod in section 21-8-27 W4M on the Oldman River. It was primarily constructed to supply irrigation water for the Lethbridge Northern Irrigation District. The upper most reach of the headworks canal was constructed in 1922, rehabilitated in the early 1980’s, and again rehabilitated in 2022-2024. Since the most recent rehabilitation, impacts of groundwater and seepage from the canal have become an increased concern during operations. Operations, Groundwater and Seepage Issues: In the 1980’s LNH canal rehabilitation design included an impermeable PVC liner which was installed as a positive blockage for seepage control. The function of the liner is to provide protection against seepage induced instability and internal erosion. The original liner exceeded its design life of 25 years and sections have been replaced. In addition, seepage must be contained to avoid artificial impacts to the ecosystem and land use due to saturation or increased soil salinity. Reach 3 of LNH is defined as the section between the Headworks Diversion Weir at the Oldman River and the end of the Oldman River Fume (this section is labelled section 1 in TEC documents). The rehabilitated portion of the canal within Reach 3 is between Stations 2+300 and 6+020. This reach has observed seepage during the operating seasons from 2021 to 2024 inclusive. The liner was replaced and toe berms have been installed in a several areas downstream of Station 2+300 in 2023 and 2024. Included in the rehabilitated canal are 41 existing piezometers for the monitoring of groundwater conditions. During the 2024 monitoring season Reach 3 was divided into 7 risk Areas (MPE 2024). Of these 7 Areas, Areas 6 and 7 were deemed to be high risk and Areas 2 and 5 were deemed to be medium risk. All risk areas require monitoring during the 2025 operational season, with the high-risk areas requiring a greater monitoring frequency. Scope of Work: Alberta Agriculture and Irrigation requires the services of an Engineering Consultant to provide monitoring and operational guidance, modelling and stability analysis for LNH Reach 3. The work shall be split into two parts, the initial phase will be during the 2025 operating season, typically ending in October, and the second phase shall be during the offseason in preparation for the 2026 operating season, typically starting in April.