VERMONT PUBLIC COMMUNITY WATER SYSTEMS-GROUNDWATER INTERFERENCE STUDY

摘要

The Vermont Rural Water Association completed an assessment of groundwater interference caused by the pumping of Public Community Water Supply (PCWS) sources throughout Vermont. The majority of PCWS sources in Vermont are wells completed in fractured crystalline bedrock aquifers, with a more limited number completed in sand and gravel aquifers present in some valley locations. Due to the non-homogenous, anisotropic nature of these aquifers, interference with nearby private and public wells and springs is difficult to predict unless measured in the field. Existing source evaluation reports prepared since 1980 by the environmental consulting community were reviewed to develop a geodatabase with key information about the pumped wells and observation wells monitored during these tests. This information includes specific pumping test information, derived values such as aquifer transmissivity and storativity, the degree of interference noted at observation locations, and a determination of acceptable versus unacceptable interference. Although the review was limited to currently active or permitted drilled PCWS sources, over 200 sources and 1,100 observation points were evaluated across the state. The results of the study indicate that, overall, groundwater interference is not a chronic problem in Vermont. However, unacceptable interference - where a specific observation well source could no longer meet its intended demand - was noted in several instances in areas of higher concentrations of PCWS sources. It was also determined that cumulative interference at a given observation location is not always accurately tracked over time, as an effective method to track cumulative interference has not existed for use by state regulators. The geodatabase developed during this study, if kept updated as new PCWS sources are permitted, would allow for effective tracking of groundwater interference across Vermont.