(17)AR 121807 Informational item - Perchlorate Update

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ITEM #17 CITY OF COLTON AGENDA REPORT FOR THE CITY COUNCIL AND COLTON UTILITY AUTHORITY MEETING OF DECEMBER 18, 2007 TO: HONORABLE MAYOR AND MEMBERS OF THE CITY COUNCIL, HONORABLE CHAIRPERSON AND UTILITY AUTHORITY MEMBERS FROM: ERIC R. FRASER, DIRECTOR OF WATER & WASTEWATER OPERATIONS SUBJECT: PERCHLORATE UPDATE FOR THE CITY OF COLTON DOMESTIC WATER SUPPLY DATE: DECEMBER 5, 2007 BACKGROUND: Since 1997 the City has tested its domestic water supply wells for Perchlorate. Results from those analyses showed variable and unpredictable levels of the constituent in Well Nos. 15, 17 and 24. In 2002 the Wells 15, 17, and 24 were removed from service until treatment was installed to remove Perchlorate to less than detectable levels. This was in response to the Perchlorate levels exceeding the then existing action level of 6 micrograms per liter set by the State of California. These actions were a driving factor to make the determination to remove the wells from service and install treatment to ensure that the water provided to our customers would be in compliance with the forthcoming water quality standards. DISCUSSION/ANALYSIS: On October 19, 2007, the State of California adopted a Maximum Contaminate Level (MCL) for Perchlorate of 6 micrograms per liter (6 ug/L). Since the adoption of that standard, some of our impacted wells have fluctuated just below and slightly over that level. At no time has water been delivered to our customers over the MCL. Because the levels of Perchlorate in the water being produced in our Wells 15, 17 and 24 vary and are close to or exceed the MCL, all water in those Wells will be run through the treatment system prior to delivery to the distribution system to ensure compliance with the MCL. This analysis of continued wellhead treatment is discussed in greater detail in the attached DPRA Report, Assessment and Evaluation of the Need to Continue Wellhead Treatment Within the Rialto -Colton Groundwater Basin, County of San Bernardino, California, dated December 4, 2007. FINANCIAL IMPACT: Funds to operate the water treatment systems for the impacted wells are included in the current year budget. The City is mandated under the Safe Drinking Water Act to provide water in compliance with the Maximum Contaminate Levels as adopted by regulation.