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GeoInsighter Fall 1999 Newsletter
Volume 4 Number 4

New Aquifer Protection Area Delineations Affect Notification & Cleanup Thresholds

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Additional Zone II Well Head Protection Areas (WHPAs) are being delineated in Massachusetts as compliance with the Federal Safe Drinking Water Act Amendments of 1996 continues to be phased in by the Massachusetts Department of Environmental Protection (MADEP). The MADEP's objective is to delineate Zone IIs for all public water supply wells with 100,000 gallon per day capacities or greater by June 2000. A Zone II is defined as the entire extent of the aquifer deposits which could fall within, and upgradient from, the production well's capture zone based upon the predicted drawdown after 180-day drought conditions at the approved pumping rate. Currently there are approximately 430 approved Zone II WHPAs in Massachusetts. Each Zone II encompasses single or multiple production wells. Approximately 250 more production wells will be included in newly designated Zone IIs under the MADEP's Source Water Assessment Program (SWAP). These wells are currently protected with Interim Well Head Protection Areas (IWPAs). In contrast to the protective 0.5 mile radius IWPAs universally applied around well heads, Zone IIs vary in size and shape depending on the geology of the aquifer surrounding a particular well head. 

The change in shape of the protected area around a particular well head could have ramifications for notifying the MADEP of releases and potential releases and on cleanup standards for sites already regulated under the Massachusetts Contingency Plan (MCP). For example, some properties currently located within 0.5 mile radius IWPAs may not be included in the new Zone II WHPAs. This may effectively change the notification threshold for these sites from the RCGW-1 values to the higher RCGW-2 values. Conversely, properties that were not within an IWPA may fall within a new Zone II. However, notification is only retroactive for those sites where sample data are collected after the Zone II effective date and it indicates that the applicable RCGW notification threshold is met. The new delineations will also affect some active sites that will no longer be required to meet GW-1 cleanup standards. Here again, other properties will be subject to the more stringent GW-1 cleanup standards that formerly had to meet generally less stringent GW-2 and GW-3 cleanup standards. The new delineations will not affect sites that have already obtained permanent solutions (Class A or B Response Actions Outcomes [RAOs]) by the time a particular Zone II designation becomes effective, provided that the closure levels adequately protect the former IWPA. Sites still active in the system, and those with Class C RAOs, will be subject to meeting the GW-1 cleanup standards if they are located within the Zone II. This may significantly change cleanup strategies for these sites as current approaches may not be capable of meeting the more stringent standards. Other MCP requirements may also apply that would require one or more of the following actions: reclassification as a Tier I or Tier II site, filing of a Major Permit Modification, and/or changing the amount of an Annual Compliance Fee.

A schedule for implementing a Zone II designation for a particular well head is posted on the MADEP's Web site at http://www.state.ma.us/dep/brp/dws/dwspubs.htm#swap. The schedule, updated in August 1999, includes estimated Zone II delineation completion dates for 56 of the approximately 200 affected well heads. The MADEP's GIS group will update Zone II data layers monthly, and hard copies of specific Zone II delineations will be available at MADEP's Boston and regional offices. 

Michael F. Dacey
mfdacey@geoinc.com

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