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

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Sampling of City wells for tritium and the indicator parameters at regular intervals will allow for tracking of concentrations over time. If concentrations of these monitoring parameters in a groundwater sample from a well are significantly higher than the concentrations in a previous sample from the same well it could be an indication that there is a pathway such as a leak in the well casing or an unused, unsealed well in the vicinity that allows water to move from the surface to the source water aquifer faster than before the pathway became available. The City will work with the MDH to sample Wells 1, 3, 4, 6, and 7 in year five after approval of this WHPP. Thereafter, the City will work with the MDH to sample the municipal wells for these parameters at least every 10 years. The City recognizes that, contingent on funding, the MDH will provide sample bottles and cover analytical costs but City staff may be required to perform the sample collection and ship samples to the MDH. 7.7.6.1 Source of Action City staff 7.7.6.2 Cooperators MDH 7.7.6.3 Time Frame In year five after approval of this WHPP and then at least every 10 years thereafter. 7.7.6.4 Estimated Cost At the time this plan was prepared, cities were not charged by the MDH for tritium and indicator parameter sampling and analysis. 7.7.6.5 Goals Achieved Obtaining data to evaluate if pathways that allow for relatively rapid movement of water from the surface to the source water aquifers are present. Success criterion: Collection of groundwater samples from the selected City wells and analysis of these samples for tritium and the indicator parameters on the schedule outlined in section 7.7.6.3. 7.7.7 Evaluation of Well 1 Casing In the Part 1 WHPP amendment (MDH, 2018) it was noted that the tritium concentration in a groundwater sample collected from Well 1 in 2017 was higher than the tritium concentration in a sample collected from the well in 2006. The rise in tritium concentration could be an indication of a leak in the well casing. Therefore, the City will hire a well contractor to evaluate the condition of the casing during the next scheduled maintenance of the well. 7.7.7.1 Source of Action City staff 37