From the Summit Daily News:
July 6 marked the 40th anniversary of the agreement that created the Silverthorne/Dillon Joint Sewer Authority. On that date in 1971, Silverthorne and Dillon entered into a joint venture to construct and mutually use the Blue River Wastewater Treatment Plant and sewer interceptor system. Soon after, Dillon Valley and Buffalo Mountain signed agreements to participate in the JSA, and in 1980 Mesa Cortina signed a similar agreement.
More wastewater coverage here.