Welcome to the Ground Water Interference Website

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The Vermont Rural Water Association (VRWA) completed an assessment of groundwater interference caused by the pumping of Public Community Water Supply (PCWS) sources throughout Vermont. This study was completed in June 2009 under a contract with the Vermont Department of Environmental Conservation Drinking Water and Groundwater Protection Division (DWGWPD).

Since the early 1980s, protocols for the testing of new PCWS groundwater sources (e.g., drilled bedrock wells, drilled gravel wells), have existed in Vermont. These protocols were initially developed by the Vermont Department of Health, which at that time was the regulatory body for new PCWS sources in Vermont. Since the transfer of PCWS regulatory authority to the Water Supply Division in 1991, requirements associated with the testing and permitting of new PCWS sources has been codified in the Environmental Protection Rules, Chapter 21: The Water Supply Rule.

One aspect of the Source Permitting process is measuring and evaluating whether pumping a proposed PCWS will withdraw enough water to reduce water levels in wells and springs near the pumping well.  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, the impact of water withdrawal on nearby private and public wells and springs is difficult to predict unless measured in the field. By monitoring water levels in nearby water supply wells and springs during a constant discharge test (pumping test) the observed and future impact can be predicted. The impact to existing drinking water supplies is called Interference and can range from non-existent to adverse – where there isn’t enough water to meet the demands of the current use. Source permitting also takes into consideration the results from previous pump tests in the area and adverse or unacceptable interference is required to be mitigated before a Source Permit can be issued.

Existing source evaluation reports prepared between 1980 and 2008 by the environmental consulting community were reviewed to develop a geodatabase that includes key information about the pumped wells and observation wells and springs 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. The geodatabase was developed in conjunction with Stone Environmental, Inc. of Montpelier, Vermont.

Information concerning PCWS source pumping tests and observation well monitoring has been submitted to the state in the form of source evaluation reports prepared by environmental consultants in association with the permitting of new PCWS sources. These are the reports that were researched and reviewed to develop the groundwater interference geodatabase for this study. The compilation of this considerable amount of data into an easy to use Database and GIS format marks the first time that this information has been assimilated and organized into a single geodatabase that can be used to provide information about PCWS sources, observation well responses and cumulative calculated interference around the state.

The VRWA final report was limited to currently active or permitted drilled PCWS sources. This represents 203 PCWS sources and 1,082 observation points evaluated across the state up to 2008. 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 design demand – was noted in several instances in areas of higher concentrations of PCWS sources.

This database is dynamic and will be populated by the most current information available as part of the ongoing DEC Source Permitting process. Public water system source testing information will be added soon for evaluations completed from 2008 to present. These data may include other water systems where interference analyses were done such as Non-Transient Non-Community and Transient Non-Community wells.

Click on this link to view the VRWA Public Community Water Systems Groundwater Interference Project Final Report

The links below are taken from the VRWA Final Report and represent a synopsis of the information used or excluded in the development of the database:

Table A-1 PCWS Bedrock, Gravel, and Dug Wells for which Source Evaluation Reports with Observation Well Data was located (Data entered into Groundwater Interference Geodatabase).

Table A-2 PCWS Sources  Developed Prior to 1980. (Data not included in Groundwater Interference Geodatabase).

Table A-3 PCWS Bedrock Well Sources  tested since 1980 with no off-site Observation Well Data. (No Groundwater Interference Data - Not included in Groundwater Interference Geodatabase).

Table A-4 PCWS Gravel Well Sources  tested since 1980 with no off-site Observation Well Data. (No Groundwater Interference Data - Not included in Groundwater Interference Geodatabase).

Table A-5 PCWS Sources  tested for which no Source Evaluation Reports were located. (No Data included in Groundwater Interference Geodatabase).

Table A-6 Spring Sources  coded as Wells in SDWIS Database. (No Pumping Test Data for PCWS Springs).

To send an email to request an account to enter Production Well and Observation Well data, click this link