Agenda - Council - 10/08/2019 - Laserfiche WebLink

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contaminant source locations identified during the implementation of this WHPP will be verified by the City with the assistance of the Wellhead Protection Consultant, if needed. 7.7.5.1 Source of Action City staff. 7.7.5.2 Cooperators City staff and the Wellhead Protection Consultant, if needed. 7.7.5.3 lime Frame When new potential contaminant sources in the DWSMA are identified. 7.7.5.4 Estimated Cost Approximately $500-$3,000. City staff time and Wellhead Protection Consultant costs, if needed. Actual costs will depend upon the number of new potential contaminant source locations that must be verified and in any update could be higher than the estimated range shown. 7.7.5.5 Goals Achieved Verification of newly identified potential contaminant source locations within the DWSMAs will allow the City to remain in compliance with the requirements of the State of Minnesota's Wellhead and Source Water Protection Program. Verification of the newly identified locations will also ensure that the City uses the most accurate data on type and location of potential contaminant sources as implementation of this WHPP proceeds. Success criterion: All potential contaminant source locations in the database are verified to the extent possible. 7.7.6 Tritium and Indicator Parameter Sampling In the April 4, 2019 Scoping Decision Notice (MDH, 2019b), the MDH recommended that the City should sampling Wells 1, 3, 4, 6, and 7 for tritium and the indicator parameters ammonia, bromide, chloride, nitrate and nitrite, and sulfate. Tritium (3H), a radioactive isotope of hydrogen, whose atmospheric concentrations rose in the 1950s and early 1960s due to atmospheric hydrogen bomb testing. It has been used extensively to date groundwater. Tritium activities peaked during atmospheric hydrogen bomb testing of the 1950s and 1960s, and values of 3H in precipitation reached a maximum of approximately 10,000 TU (tritium units) in 1963 (Mazor, 2004). Natural production of 3H in the upper atmosphere introduces approximately 5 TU to precipitation each year (Mazor, 2004). The presence of tritium at concentrations above 1 tritium unit in a groundwater sample indicates the presence of a significant fraction of post-1954 (i.e., recently infiltrated) water in the sample. The indicator parameters provide additional information on the rate at which an aquifer recharges and can also provide evidence of impacts to groundwater by human activities. 36