TR-478 Pathogen Risk to Human Health in Potable Water Related to Nonpoint Sources of Contamination: Colorado River Alluvium Case Study, River Segment 1428 Phase II Final Report
Authors: T.A. Berthold, T. Gentry
Public and private wells that use alluvial aquifers as a drinking water source have an increased risk of contamination from pathogens. This reconnaissance study, conducted by the Texas Water Resources Institute (TWRI) and subcontractors, focused on Segment 1428 of the Colorado River as a site of highest contamination risk based on (1) density of OSSFs, (2) groundwater chemistry, and (3) areas Texas Commission on Environmental Quality (TCEQ) Water Supply Division has previously identified as either having fecal coliform positive samples in raw well samples or when 1 micron filtration samples are indicative of “Groundwater under the influence of Surface Water.”
Groundwater (and adjacent surface water) sampling was conducted following dam releases from Tom Miller Dam and transmitted through Longhorn Dam. Water chemistry data (pH, specific conductance, dissolved oxygen, temperature) was evaluated to determine the effects of the mixing of surface water and groundwater. A transect of wells at different distances from the river was sampled to determine to what degree distance from the river controls the level of pathogens. Transects were sampled at one location along the river. Water samples were analyzed for bacteria. Polymerase chain reaction (PCR) for Cryptosporidium and for selected viruses was conducted on selected samples (minimum of 3). This final report provides an account of activities conducted under this scope of work as well as work from a companion Clean Water Act (CWA) 604(b) grant project titled “Pathogen Risk to Human Health in Potable Water Related to Nonpoint Sources of Contamination: Colorado River Alluvium Case Study, River Segment 1428.”