North Santiam Sewer Authority
Project Schedules and Workflows
The following graphics show the predicted schedules and workflows for wastewater system implementation in the Mill City/Gates basin (Project A) and Detroit/Idanha basin (Project B). For more information, refer to the North Santiam Sewer Authority Wastewater Master Plan.​
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Project A: Mill City/Gates Basin Schedule
Month 1 refers to January 2022. Estimated project completion in 2026-2027.
Project B: Detroit/Idanha Basin Schedule
Month 1 refers to January 2022. Estimated project completion in 2027-2028.
Future Municipal Sewer System and Studies to date (hydrologic and soils)
In Detroit Idanha basin, evaluation for potential suitable site for municipal wastewater treatment and disposal site started in 2020. Four sites were pre-selected for desktop evaluation for potential infiltration of advanced treated (Class A) wastewater based on the following characteristics: (1) the level of effort for site development, (2) potential permitting challenges, (3) the volume of water that can likely be infiltrated based on aquifer characteristics, (4) the aerial extent of the aquifer beneath the infiltration facility, and (5) surficial soil permeability. The sites were ranked by infiltration potential with the objective of selecting two of the sites for infiltration testing to measure soil permeability. In addition, permitting and other regulatory requirements for the sites were evaluated. Two sites were selected for further testing with one site, McCoy, advancing for surface and ground water level monitoring. The McCoy Site is located on a combination of U.S. Forest Service (USFS) and privately-owned property located approximately two miles southeast of Idanha, Oregon.
Test pits were dug and six groundwater monitoring wells (three stilling and three monitoring wells) were installed to assess the compatibility of the site as a potential location for treated wastewater infiltration. Based on the test and evaluation results, it was found to be incompatible due to insufficient permeability of subsurface soils, the occurrence of shallow ground water, and potential for wastewater to discharge to McCoy Creek. The wells were decommissioned in March 2025.
With Oregon’s Three Basin rule amendment in December 2025, Detroit and Idanha now have a pathway for a municipal wastewater treatment facility.
Commercial Septic (Tsige)
As an investment in sewer infrastructure is an eligible activity under American Rescue Plan Act (ARPA) that serves the dual purpose of aiding wildfire recovery and economic development in the North Santiam River Canyon, Marion County has created Commercial Septic Repair, Alteration and Replacement Grant Program. The program provides financial assistance in the form of cash reimbursement for actual costs sustained by eligible property owners for the repair, alteration, replacement or construction of commercial-grade septic systems serving commercially zoned properties and essential public facilities. This Program has limited funding and grant awards are made on a first come, first served basis.