A GIS DATABASE THAT INCLUDES RELEVANT OSSF INFORMATION, SUCH AS LOCATION, SYSTEM AGE, LOT SIZE, AND OTHER IMPORTANT PARAMETERS WAS CREATED

In a collaborative effort between Texas Water Resources Institute (TWRI), Cameron County Public Health (CCPH), Texas A&M AgriLife Extension (TAMAE), and the University of Texas Rio Grande Valley (UTRGV), a GIS database that includes relevant OSSF information, such as location, system age, lot size, and other important parameters was created.

This OSSF database, along with publicly available GIS data, was used to create an integrative GIS-based risk assessment model where OSSF risk parameters were assigned a risk factor and combined into a spatial contamination risk for surrounding areas and their receiving waterbodies. Parameters were broken down into two categories: environmental factors and OSSF system factors. Environmental parameters included soil type, land slope, floodplain, surface water proximity, drinking water supply proximity, and groundwater recharge areas. OSSF system parameters included system age and OSSF density. A model sensitivity analysis was then conducted using map removal sensitivity analysis and single parameter sensitivity analysis. A limited bacterial assessment was also conducted by enumerating E. coli in low and high risk waterbodies to provide a framework for future model calibration and validation.