Researchers have been collecting water samples at 30 river sites — 15 in the Lampasas River watershed and 15 in the Leon River watershed — monthly since February. They’ve also been taking fecal samples from all over the watersheds of known possible sources: home septic systems, wildlife, livestock, pets and water-treatment plants. The samples are then “genetically fingerprinted” to determine exactly what the source of E. coli is.