Filtration Avoidance

August 9, 2017

Chazen helped the Village evaluate whether three existing wells situated near the Croton River required microfiltration. A detailed study designed by Chazen indicated that natural sediments provided ample filtration, resulting in significant cost savings to the community.

Chazen first conducted a hydrogeologic review of existing well construction details and available hydrogeologic analysis and well logs. These records suggested that layers of silt and clay lay between the river and the saturated sand and gravel horizon supporting groundwater flow to the Village wells.

Chazen then developed a test protocol to examine groundwater temperature and electrical conductivity through many pumping cycles. This approach demonstrated very stable groundwater conditions which were quite different from river quality conditions. Chazen also collected groundwater samples for biological review.

Results of the study were presented to the Department of Health, which determined that water from the Village wells did not qualify as Groundwater Under Direct Influence (GWUDI) of surface water, giving assurance to Village residents that these wells provide high-quality groundwater that does not need micro-filtration beyond that already provided by the aquifer sediments.