The county is investigating a property near Nicasio School as a potential site for 16 units of farmworker housing. Though it has determined that a septic system could be installed at the 2.2-acre site, it still needs to find out if there is an adequate water supply to support the project. The county-owned property is located across from the Department of Public Works corporation yard on Nicasio Valley Road, between the school and West Marin Compost. Planners had hoped that a well now serving the public works facility could also supply enough water for housing, but Sutro Science, the engineering firm conducting a groundwater study for the county, found that the well would not produce enough for 16 units. Last week, the Board of Supervisors extended its contract with the firm, which last summer drilled in search of a location for a new well but came up dry. The company plans to make a second attempt in August. If enough water is discovered, the county will reach out to developers to see if they are interested in the project. The housing would be clustered on a portion of a larger 14-acre property owned by the county. The site is one of many in Marin rezoned as possible locations for affordable housing to meet ambitious construction targets set by the state. Leelee Thomas, a county housing specialist, said planners might consider a scaled-back project if the corporation yard well proves to be the only available water supply.