Located in San Juan, Washington, the Jefferts Dam stands as a crucial water resource structure for irrigation and recreation purposes. Completed in 1988, this earth-type dam boasts a hydraulic height of 15 feet and a structural height of 12 feet, with a storage capacity of 52 acre-feet. Situated on the Tr-San Juan Channel, the dam covers a surface area of 5 acres and serves a drainage area of 0.06 square miles.

Owned privately, the Jefferts Dam is regulated and permitted by the Washington Department of Ecology, ensuring its compliance with state laws and regulations. With a low hazard potential and a condition assessment of "Not Rated," this dam plays a significant role in water management and conservation efforts in the region. Despite its modest size, the dam has a maximum discharge capacity of 100 cubic feet per second, providing a vital water source for the surrounding agricultural lands.

Managed by the Seattle District of the US Army Corps of Engineers, the Jefferts Dam maintains a strong operational record, with regular inspections and enforcement procedures in place. With its strategic location and purposeful design, this dam serves as a testament to the importance of sustainable water resource management in the face of changing climate patterns and growing water demands.