AWWA WQTC62611

AWWA WQTC62611 Monitoring Groundwater Aquifers in Anticipation of the Groundwater Rule
Conference Proceeding by American Water Works Association, 11/01/2005

Fujioka, Roger; Sato, Dayna; Vithanage, Gayatri; Yoneyama, Bunnie

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An objective of the pending Ground Water Rule (GWR) is to determine which potable groundwater sources are vulnerable to fecal contamination so appropriate remediation actions can betaken. One reason for the delay in finalizing the GWR is disagreement on the fecal indicators tobe used to determine when that groundwater source is free of fecal contamination. Inanticipation of the GWR, large volumes (200-1,000 ml) of groundwater samples from the islandof Kauai were analyzed for all of the microbial fecal indicators (total coliform, Escherichia coli,enterococci, Clostridium perfringens, FRNA coliphages, somatic coliphages) being consideredunder the GWR. Kauai, one of the smaller islands in the state of Hawaii was selected as the studysite because cesspools and septic tanks are extensively used to discharge untreated and poorlytreated sewage into shallow sub-surface soil, often over potable water aquifers. Over a 14-monthperiod, 48 groundwater samples from 37 wells operated by the County of Kauai and 61groundwater samples from 10 wells operated by private water utilities were analyzed. The resultsshowed that 15% (7/48) of the well water samples operated by the County of Kauai was positivefor total coliform but none of these samples was positive for E. coli (0/48), enterococci (0/41),FRNA coliphages (0/48), somatic coliphages (0/48) and C. perfringens (0/47). In comparison,16% (10/61) of the well water samples from private sources was positive for total coliform, 2%(1/61) were positive for E. coli, and 11% (6/53) were positive for enterococci. However, none ofthese samples were positive for FRNA coliphages (0/61), somatic coliphages (0/61) and C.perfringens (0/56). These results provide evidence that, based on monitoring groundwater sourcesfor the fecal microorganisms being considered for monitoring under the GWR, the potablegroundwater sources on the island of Kauai are not vulnerable to contamination with fecalmatter. Moreover, the monitoring data show that extensive use of cesspools and septic tanks onKauai is not measurably contaminating the potable groundwater sources. Includes 16 references, tables, figures.