Sealand, Limited Superfund Site
Mt. Pleasant, Delaware
Prepared by: U.S. Environmental Protection Agency, Region III, Philadelphia, Pennsylvania
Thomas C. Voltaggio, Director
Hazardous Waste Management Division
U.S. Environmental Protection Agency
Hazardous Waste Management Division
Five-Year Review (Type I)
Sealand, Limited Superfund Site (Mt. Pleasant, Delaware)
EPA Region III conducted this review pursuant to CERCLA section 121(c), NCP section 300.400(f)(4)(ii), and OSWER Directives 9355.7-02 (May 23, 1991), and 9355.7-02A (July 26, 1994). It is neither a statutory nor a policy review, but, at the Region's discretion, was required by the 1991 Record of Decision to address State concerns over the protectiveness of the selected remedy (No Action). The purpose of a five-year review is to ensure that a remedial action remains protective of public health and the environment and is functioning as designed. This document will become a part of the Site file. This review (Type I) is appropriate at this Site.
The Sealand, Limited Site is located in Mt. Pleasant, New Castle County, Delaware. In August of 1982, Sealand, Limited began treating and/or recycling waste streams such as off-specification creosote, No. 4 oil, No. 6 oil, and oil/gas tar. One year later, the owner abandoned the Site, leaving behind 21 steel tanks, one 10,000-gallon wooden storage tank, over 300 steel drums, a boiler house, and various mixing chambers and pressure vessels. During a Site inspection conducted by the Delaware Department of Natural Resources and Environmental Control (DNREC), several drums and tanks were found to be leaking. In response, EPA initiated an emergency removal action in December of 1983. During this action, all of the drums were removed from this site, as was all of the liquid contained in the various tanks, which were cleaned and left near the Site. The process area was capped with one foot of clay and six inches of topsoil.
In December of 1988, EPA and 14 Potentially Responsible Parties (PRPs) entered into an Administrative Order on Consent to conduct a Remedial Investigation/Feasibility Study (RI/FS) at the Site. During the remedial investigation, both ground water and the soil beneath and near the capped area were sampled. Low levels of volatile organic compounds and some semivolatile compounds were found in the soil beneath the cap. Metals were found in Site soil at levels generally consistent with background levels. Neither volatile nor semivolatile compounds were found at significant concentrations in the ground water. One onsite well contained elevated levels of metals, particularly nickel; however, there was no clear correlation between the Site and the metals.
During the risk assessment, ground water was not considered a potential contaminant exposure pathway. The most likely exposure scenarios included children who could be exposed to shallow soil while trespassing on the Site, and workers who could be exposed to subsurface soil during construction activities. The risk assessment assumed that the Site, which is zoned for industrial use and is bordered by an active Conrail freight line and a paving company, would not be rezoned for residential use. Given this assumption, the risks associated with the two most likely exposure scenarios were below the lower boundary of the acceptable risk range. It was determined that the Site did not pose a threat to human health or the environment, and the Region issued a Record of Decision (ROD) calling for no further action in September of 1991.
II. Remedial Objectives; ARARs Areas of Noncompliance
During the preparation of the ROD, DNREC expressed concern about the proposed remedy. They believed that the contaminants which would be left in place beneath the cap could pose a future threat to ground water. In response to this concern, EPA included in the selected remedy a review of the site five years after the signing of the ROD, even though a five year review would not ordinarily be required for this type of remedy. Furthermore, EPA acknowledged in the ROD that although Federal law did not require action at the site, the State was still free to act under it own laws. Nonetheless, DNREC did not concur with the ROD.
Subsequent to the signing of the ROD, DNREC took action pursuant to the authority of 7 Del. C., Chapter 91, the Delaware Hazardous Substance Cleanup Act (HSCA). HSCA was not considered an Applicable or Relevant and Appropriate Requirement (ARAR) during the remedy selection process, as ARARs are not considered in a no action decision. DNREC required the PRPs to install additional monitoring wells and to resample the ground water. The results of the sampling showed no organic contamination in the wells. However, some metals, including nickel, were present at elevated levels in some wells. There was no clear pattern to the wells containing metals; one is apparently upgradient of the contaminated soil, and adjacent to the active Conrail tracks.
Using this information, DNREC issued a Proposed Plan of Remedial Action in October of 1995. The proposed remedial action included five years of continued ground water monitoring, as well as deed restrictions to ensure that the property's zoning does not change from industrial to residential. This plan has since been finalized, and DNREC is negotiating with the PRPs to conduct this work.
III. Summary of Site Visit; Areas of Non-Compliance
The Region visited the site on June 26, 1996. A visual inspection of the Site area indicated that little has changed since the ROD was signed, although some new monitoring wells have been installed in the vicinity of the capped area by the PRPs at the direction of DNREC. The clay cap is intact and well vegetated, with no indication of erosion or other degradation. There are no areas of non-compliance with the ROD.
It is recommended that EPA proceed with the deletion of this Site. There have been no apparent, significant changes since the ROD was signed. As anticipated in the ROD, DNREC has chosen to take action at this Site pursuant to HSCA; thus, future Federal action will not likely be necessary.
IV. Statement on Protectiveness
I certify that the remedy selected for this site remains protective of human health and the environment.
V. Next Five-Year Review.
There will be no need for future five year reviews at this Site.