The Graton Resort & Casino (Resort) is located in the Laguna de Santa Rosa watershed within the Santa Rosa Valley Basin (Basin) in Sonoma County. The Basin consists of three sub-basins: the Santa Rosa Plain Sub-Basin, the Healdsburg Area Sub-Basin, and the Rincon Valley Sub-Basin. The Resort is located in the Santa Rosa Plain Sub-Basin (Sub-Basin). Several thousand wells pump from the Sub-Basin, including agricultural wells, municipal wells, and rural domestic wells.

Water is supplied in the vicinity of the Resort by private domestic wells, irrigation wells, and local water suppliers. The largest water purveyors in the area are the City of Rohnert Park and Sonoma Water (SW). Other water purveyors include Sonoma State University, the City of Cotati, and Penngrove Water Company. The Resort is within an agricultural area where irrigation pumping is substantial.

The Federated Indians of Graton Rancheria (“FIGR”) has funded a voluntary well monitoring program since 2012 to assess groundwater levels on privately owned wells within a 2-mile radius of the Graton Resort & Casino. This voluntary program was previously conducted by the Sonoma Resource Conservation District, which recently opted to discontinue participation. Montrose Environmental has been retained to continue implementation of the program.

To address concerns regarding groundwater sustainability, the County and other groundwater users within the Santa Rosa Plain Sub-Basin developed a Groundwater Sustainability Plan as required by the Sustainable Groundwater Management Act (SGMA). Graton Rancheria is voluntarily participating in the Groundwater Sustainability Agency Advisory Committee formed in October 2017. Groundwater sustainability of the Santa Rosa Plain Sub-basin has been addressed in the County’s Groundwater Sustainability Plan following the criteria defined in the SGMA.