E8-18836. Sole Source Aquifer Designation of Conanicut Island, Narragansett Bay, RI

AGENCY:

Environmental Protection Agency.

ACTION:

Notice of determination.

SUMMARY:

The Regional Administrator of Region I of the Environmental Protection Agency (EPA) has determined, pursuant to section 1424(e) of the Safe Drinking Water Act, that the aquifer system that underlies Conanicut Island, Rhode Island is the sole or principal source of drinking water for this area and if the aquifer system were contaminated would create a significant hazard to public health. As a result of Sole Source Aquifer (SSA) designation, federal financially-assisted projects over the designated aquifer area will be subject to EPA review to ensure that these projects are designed and constructed so that they do not contaminate this aquifer so as to create a significant hazard to public health.

DATES:

Effective Date: This determination shall become effective on August 14, 2008.

ADDRESSES:

The data and record upon which these findings are based are available to the public and may be inspected during normal business hours at the U.S. Environmental Protection Agency—Region I, Office of Ecosystem Protection, One Congress Street, Suite 1100, Boston, MA 02114-2023.

FOR FURTHER INFORMATION CONTACT:

Douglas Heath, U.S. EPA—Region I at the address above or at [phone], e-mail: [e-mail].

SUPPLEMENTARY INFORMATION:

I. Background

Section 1424(e) of the Safe Drinking Water Act, 42 U.S.C. 300h-3(e), states: “If the Administrator determines, on his own initiative or petition, that an area has an aquifer which is the sole or principal drinking water source for the area and which, if contaminated, would create a significant hazard to public health, he shall publish notice of that determination in the Federal Register. After the publication of any such notice, no commitment for federal financial assistance (through a grant, contract, loan guarantee, or otherwise) may be entered into for any project which the Administrator determines may contaminate such aquifer through a recharge zone so as to create a significant hazard to public health, but a commitment for federal financial assistance may, if authorized under another provision of law, be entered into to plan or design the project to assure that it will not so contaminate the aquifer.”

On February 1, 2006, EPA Region I received a petition from the North End Concerned Citizens (NECC) requesting the designation of the aquifer system underlying Conanicut Island as a SSA. NECC subsequently submitted a revised petition. Among other things, the revised petition removed references to an original request that EPA review closure plans for a landfill and the location of a proposed Town Garage. On August 17, 2007, EPA completed its technical review of the completeness and adequacy of the petition. On February 13, 2008, EPA held a public meeting in Jamestown and invited public comment on the petition. The public comment period closed on March 19, 2008.

II. Basis for Determination

Among the factors considered by the Regional Administrator as part of the review and technical verification process for designating an area under section 1424(e) were:

1. The aquifer system underlying Conanicut Island supplies the service area population with 50% or more of its drinking water needs. Approximately 57% of the island's residents rely solely on residential supply wells. The remaining 43% of residents rely on municipal water provided by the Jamestown Water District (a portion of which is also ground water extracted by bedrock wells) with a peak flow of 400,000 gallons per day.

2. There is no physical, legal and/or economical alternative drinking water source or combination of sources to meet all of the needs of the designated service area.

3. The EPA finds that the petition appropriately delineates the boundaries of the aquifer project review and service area. For purposes of this designation, EPA finds the Conanicut Island Aquifer System boundary is based on the mean high tide line since this marks the freshwater-saltwater boundary.

4. While the quality of the area's ground water is considered to be good, it is vulnerable to contamination due to the relatively thin soil cover and rapid movement of ground water in fractured rock, coupled with increasing development and other land uses. Recharge of the water supply is by infiltration of precipitation over the entire island. The designated area is underlain primarily by a fractured bedrock aquifer system. The aquifer system is overlain by areas of glacial till and soil deposits. Freshwater in bedrock fractures under the island forms a lens-shaped body that floats on saltwater as its density is less than that of saltwater. According to a 1997 study by the University of Rhode Island, the thickness of the freshwater lens is estimated to range from a few tens of feet near the shoreline to more than 500 feet in the central part of the island under non-pumping conditions.

III. Description of the Conanicut Island Aquifer System That Underlies Conanicut Island

The Conanicut Island Aquifer System is a nine-square-mile island located in Narragansett Bay, Rhode Island. The island is divided into three land masses: North Island, Central Island, and Beavertail Peninsula. North Island rises to an elevation of about 140 feet above sea level and is characterized by parallel ridges running north-south which create the Jamestown Brook Watershed. To the south, separated by Great Creek and extensive wetlands, is the Central Town area. The Central Island area is comprised of gently rolling hills up to 100 feet elevation with bedrock outcrops in the Dumplings and Fort Wetherill area. To the southwest is the Beavertail Peninsula rising to an elevation of 125 feet. The peninsula is connected to the rest of the island by a sandy isthmus called Mackerel Cove Beach.

The average annual precipitation is approximately 43 inches. The island's climate is moderated by the waters of Narragansett Bay and the Atlantic Ocean.

Conanicut Island's bedrock is terrestrial metasedimentary rock of Pennsylvanian age (approximately 300 million years old) in the north and the Cambrian-age Conanicut group in the center of the island and on Beavertail. Originally deposited as sediments ranging from coarse-grained gravel to fine-grained silt, these materials hardened over time into metamorphic rocks. Fort Wetherill on the southeastern portion of the island is underlain by Proterozoic Newport Formation granites. These are overlain by poorly-sorted glacial till ranging from 0 to about 45 feet in thickness. Because the rock and till transmit water very slowly, seasonally-high water table conditions occur throughout much of the island.

IV. Information Utilized in Determination

The information utilized in this determination includes: The petition and supporting documents submitted by the NECC, letters received before and during the public comment period, and public comments received during the public hearing. In addition, much of the information has been derived from published literature on the hydrogeology and water resources of the region. This information is available to the public and may be inspected at the EPA Region I office in Boston, Massachusetts (address listed above). The petition and support document and EPA's response summary to public comment are also available at the Jamestown Public Library in Jamestown, Rhode Island.

V. Summary and Discussion of Public Comments

Most comments received were in favor of the designation. Written comments in support were received from the Honorable Lincoln Chaffee, U.S. Senate; Senate Majority Leader M. Teresa Paiva Weed and House Deputy Minority Whip Bruce J. Long of the Rhode Island General Assembly; the Rhode Island Department of Health; the Rhode Island Department of Environmental Management; and 36 residents/households of Jamestown. On March 11, 2008, a majority of the Jamestown Conservation Commission voted to support the petition. On March 17, 2008, a majority of the Town Council approved a motion to support SSA designation. EPA received five written comments expressing opposition to the designation. Among these were letters from two members of the Town Council.

EPA has addressed the written comments received in a Responsiveness Summary, which is part of the record of this decision. The Responsiveness Summary is available at the EPA Region I offices and at the Jamestown Public Library.

VI. Project Review

After the effective date of this designation, EPA will evaluate projects within the designation area that include federal financial assistance to determine whether the project may contaminate the aquifer so as to create a significant hazard to public health. Where practicable, EPA will offer comments as to how the project may be designed to protect the aquifer. EPA anticipates that few future projects will trigger SSA review. Where review is required, EPA will coordinate with state and local agencies and the project's developers. EPA will give their comments full consideration. Through its review, EPA will attempt to complement and support state and local ground water protection measures. Although the project review process cannot be delegated, EPA will rely to the maximum extent possible on any existing or future state and/or local control measures to protect the quality of ground water in the review area. EPA also will work to integrate any review with related reviews required pursuant to other federal laws, such as the National Environmental Policy Act (NEPA) as amended 42 U.S.C. 4321, et seq., to avoid delay or duplication of effort.

Authority: This action is issued under the authority of section 1427 of the Safe Drinking Water Act as amended 42 U.S.C. 300h-3(e).

Dated: July 30, 2008.

Ira Leighton,

Acting Regional Administrator, USEPA Region I.