South Shore 2 Wastewater System Rehabilitation
Approximately 4,000 linear feet of sewer pipe lining, the rehabilitation of over 80 sewer manholes, nearly 40 sewer lateral connections, nearly 900 linear feet of sewer lateral lining, the correction of 4 stormwater cross connections, and the replacement of 13 manhole covers. (Project as a result of the I/I Reduction Program Study)
Because the majority of the City of Lake Oswego’s wastewater enters the City of Portland’s Tryon Creek Wastewater Treatment Plant, Lake Oswego is required to meet Compliance Conditions and Schedules in the City of Portland Bureau of Environmental Services’ National Pollutant Discharge Elimination System Waste Discharge Permit (NPDES). The goals of this program are to decrease the wastewater flow volume from the Lake Oswego system and to limit wastewater overflows during any rain event.
The City of Lake Oswego completed an update to its Wastewater Collection System Master Plan (Plan) in March 2013 that identified historically high wet-weather peak wastewater flows attributed to excessive inflow and infiltration (I/I) in several basins. The Plan identified approximately $20 million of infrastructure work focused on reducing I/I. The City also recently partnered with BES on the Tryon Creek wastewater treatment plan facility update. Both parties are interested in finding ways to reduce flows to the plant and are evaluating I/I reduction goals.
The Plan recommends the City implement an aggressive Infiltration and Inflow (I/I) reduction program to reduce I/I within the existing wastewater collection and conveyance system. Although several of the City’s many wastewater collection and conveyance system basins need I/I reduction, a portion of the South Shore Basin has been chosen for an initial I/I reduction effort. Though not described in the Plan as having the highest I/I rate, the South Shore Basin is described as having a significantly high I/I rate, and it is tributary to the recently completed Lake Oswego Interceptor Sewer (LOIS). Aggressive I/I reduction within basins tributary to the LOIS is mandatory, if the LOIS is to continue to alleviate system overflows.
VALUE TO THE SEWER SYSTEM
Replacement or rehabilitation of the South Shore 2 Basin sanitary sewer will extend the service life of sewer lines and provide additional maintenance access via property line cleanouts. Additionally, reduction of I/I entering the sanitary sewer system reduces the treatment volume reaching the Tryon Creek Wastewater Treatment plant, possibly reducing the City’s water treatment costs.
March 31, 2021
The South Shore 2 Rehabilitation Project is currently in out to bid. The City anticipates awarding the contract for construction in May of 2021. Construction is expected to begin in Summer 2021 and conclude in Fall 2021.