This project reviewed the ability of hydrilla to release THM-precursors should this plant become established in the Occoquan Reservoir. It was found that the Occoquan Reservoir could support hydrilla. Three sources of THM-precursors were found to result from hydrilla. These included: 1) extracellular products (ECP) from hydrilla itself; 2) ECP from periphyton that colonized the hydrilla; and 3) decay products from hydrilla. This study projected aa potential increase in THMFP of 23 ug/L should hydrilla become established in the Occoquan. The current level of THMFP in the H reservoir is approximately l,OOO ug/L.