Rat Farm is a public boat launch on PG&E property accessed via a 3-mile graded dirt road from McArthur, featuring a gravel parking area and pit toilet.

The launch provides access to Horr Pond and Ahjumawi Lava Springs State Park, ideal for kayaks and canoes, though shallow water areas require careful navigation to avoid bottoming out.

This is the only access point to the remote 6,000-acre park, which offers 13 miles of scenic shoreline and primitive camping.