Abestos Cement Transmission Main Replacement

RH2 supported the Northeast Sammamish Sewer and Water District in identifying a $20+ million capital improvement as part of the District’s Water System Plan update to replace aging asbestos cement (AC) transmission mains. Condition assessments and testing identified interior and exterior pipe degradation, and routine water quality monitoring detected trace levels of asbestos—issues expected to worsen as the infrastructure continued to age.

The District had already replaced more than 12,500 linear feet of AC pipeline, but these findings required an accelerated, system-wide response. RH2 worked with the District to secure low-interest funding for both design and construction, enabling replacement of approximately 10,000 linear feet of 10- and 12-inch transmission main. The improvements increase system redundancy, enhance seismic resilience, and address long-term water quality concerns. This work forms a key component of the District’s broader capital improvement program focused on protecting public health and strengthening critical infrastructure.