City of Richmond, Virginia conducts Bacteriological Monitoring in the James River as Indicator of the Effectiveness of its Established Long Term Combined Sewer Overflow (CSO) Control Program

摘要

The City of Richmond, Virginia conducted in 2000 a bacteriological monitoring program to complement the existing data collected in previous bacteriological sampling programs conducted in the 1980’s and 1990s. The James River in the study area is a “Tier I” protected river which requires maintenance and protection of existing aquatic uses. The Virginia Department of Environmental Quality (DEQ) is currently considering E. coli and enterococci as potentially better suited for predicting the presence of gastrointestinal illness-causing pathogens in freshwater. The study included all microbial organisms considered as probable indicators of human contact related health effects. Understanding the population levels of these organisms upstream and downstream of a wet weather CSO discharge is critical in the application of water quality based controls. Evaluating the combined effects of all interacting bacteriological sources is paramount to all municipalities addressing CSO control in assigning properly designed engineering control measures. This monitoring program was conducted as part of the City’s Long Term CSO Control Program under a Special Order agreed upon with the DEQ as issued October 8, 1999. This study also provides Richmond, other localities and the Commonwealth of Virginia sound scientific basis to indicate if attainment of the present bacterial water quality standard is possible or if movement towards an alternative based on water quality improvements from a well designed and operated CSO Long Term Control Program is needed. Utilization of actual river bacterial monitoring information as input to both the combined sewer system model and the James River tidal model provided the basis to conduct the necessary long range CSO planning analysis based on gains in river bacterial water quality.