"States Rate Septic Tanks as No. 2 Source of Groundwater Pollution
Small Flows Quarterly, Fall 2000, Page 4
In a recently published U.S. Environmental Protection Agency (EPA) report, 31 states listed septic systems as their second greatest potential source of groundwater contamination. Leaking underground storage tanks headed the list.
This document, the National Water Quality Inventory: 1998 Report to Congress, is the twelfth biennial report to Congress and the public about the quality of U.S. rivers, streams, lakes, ponds, reservoirs, wet-lands, estuaries, coastal waters, and groundwater. It was prepared under Section 305(b) of the Clean Water Act (CWA), which requires states and other jurisdictions to assess the health of their waters and the extent to which they meet state water quality standards and the basic goals of the CWA. This information is submitted to the EPA every two years and summarized in the biennial report to Congress.
States have not yet comprehensively assessed all of their waters, but this edition of the biennial report is based on the assessment of almost 25 percent of the nation's total river and stream miles; 40 percent of its lake, pond, and reservoir acres; and 30 percent of its estuarine square miles.
This 1998 report represents the second 305(b) cycle of data collection based on groundwater guidelines introduced to states as part of the 1996 305(b) reporting cycle. The chapter on groundwater is the result of data submitted by 37 states, three territories, four tribes, and the District of Columbia (all collectively referred to as states). States reported ground-water-monitoring data for a total of 146 aquifers or hydrogeologic sitings.
The report concluded that while the quality of U.S. groundwater is good and can support the many different uses of this resource, aquifers across the nation are showing measurable impacts from human activities. Monitoring has detected elevated levels of petroleum hydrocarbon compounds, volatile organic compounds, nitrates, pesticides, and metals. Improperly constructed and poorly maintained septic systems are believed to cause substantial and widespread nutrient and microbial contamination to groundwater.
The significance of this to the environment as a whole can be seen in the results of a U.S. Geological Survey study (cited in the report) that included at least 2 streams in each of 24 physiologic and climatic regions nationwide to investigate groundwater and surface water interactions. Based on daily stream flow values for the 30-year period 1961 to 1990, the analysis indicated that an average of 52 percent of all the streamflow in the U.S. was contributed by groundwater. This contribution ranged from 14 to 90 percent. Historically, surface water and groundwater have been treated as separate entities in the management of water resources.