PUBLIC HEALTH ASSESSMENT ADDENDUM
SOMERSWORTH MUNICIPAL LANDFILL
SOMERSWORTH, STRAFFORD COUNTY, NEW HAMPSHIRE
ENVIRONMENTAL CONTAMINATION AND PHYSICAL HAZARDS
Additional environmental sampling has been conducted in and around this site since the April 12, 1989 Health Assessment. The Settling Parties conducted sampling between October 1989, and March 1992. Groundwater sampling was conducted on three occasions (November 1989, March 1990, January 1992). Air monitoring was conducted in October 1990. The results of these investigations can be found in the (RI) Data Gathering Report (2). The State of New Hampshire Department of Environmental Services and the Environmental Protection Agency have also conducted additional sampling at this site.
When conducting an ATSDR public health assessment, health assessors identify and review all available environmental contamination data for a site. The On- and Off-site portions of this section describe sampling that has been done and identify contaminants of concern. The following is a discussion of the process ATSDR uses for selecting contaminants of concern and Toxic Chemical Release Inventory (TRI) data.
Selection of Contaminants of Concern
ATSDR selects contaminants for further evaluation based upon the following factors (8):
| (1) | comparison of concentrations of contaminants on and off site with media values for noncarcinogenic and carcinogenic endpoints, |
| (2) | sampling plan and field and laboratory data quality, and |
| (3) | community health concerns. |
Identification of a contaminant of concern in the On-site and Off-site Contamination subsections does not mean that exposure will result in adverse health effects, only that additional evaluation is necessary. The public health significance, if any, of exposure to the contaminants of concern is evaluated in subsequent sections of the public health assessment.
Comparison values are used to select contaminants for further evaluation. The ones used in this public health assessment were ATSDR's Environmental Media Evaluation Guides (EMEGs) and Cancer Risk Evaluation Guide (CREG), and EPA's Reference Doses (RfD), Maximum Contaminant Levels (MCLs), and lifetime drinking water health advisories (LTHA). Both carcinogenic and noncarcinogenic endpoints were considered in selecting contaminants of concern.
EMEGs are media-specific estimates of exposure levels that pose a minimal risk to humans. They are based on ATSDR's minimal risk levels (MRLs). When a MRL is not available for a substance, an EPA RfD, if available, is used to estimate media-specific exposure levels. CREGs are estimated contaminant concentrations based on a one excess cancer in a million persons exposed over a lifetime. CREGs are calculated from EPA's cancer slope factors. MCLs represent contaminant concentrations that EPA deems protective of public health (considering the availability and economics of water treatment technology) over a lifetime (70 years) at an exposure rate of 2 liters of water per day. LTHAs are similar to MCLs except that only health factors are considered. The availability and economics of water treatment technology is not.
Contaminants of concern for this site include benzene, 1,2 dichloroethane (1,2 DCA), vinyl chloride, trichloroethene (TCE), tetrachloroethane (PCE), 1,2 dichloroethene (cis & trans), methyl ethyl ketone, bromoethane, and arsenic.
Review of Toxic Chemical Release Inventory (TRI) Data
To identify possible facilities that could contribute to contamination near the Somersworth Sanitary Landfill Site the New Hampshire Division of Public Health Services (NH DPHS) searched the 1987 and 1988 Toxic Release Inventory (TRI). The TRI is developed by the U.S. Environmental Protection Agency (EPA) from the chemical release information provided by certain industries. A search of the TRI did not contain information on toxic chemical releases in the towns of Barrington, Durham, Lee, Madbury, and Rollinsford, NH (see Appendix B). Information on toxic chemical releases to the air was found during a search of the TRI for facilities in the cities of Somersworth, Dover, Portsmouth, and Rochester and in the surrounding town of Newington. A toxic chemical release to water was also found in the 1987 TRI for one facility in the City of Rochester. Although some of the toxic chemicals released to the environment from the facilities listed in the TRI may be contributing to ambient air quality at and around the site, previous investigations have indicated that the levels of volatile organic compounds (VOCs) measured in the air near the site should not present increased health risks for residents living near the site.
Additional data to supplement information contained in the RI (8) were collected relative to air and groundwater quality on-site and are reported in the RI Data Gathering Report (2). Additional residential and monitoring well sampling was conducted by the State of New Hampshire (3,2). Additional sediment sampling was conducted by EPA as part of a yearly site assessment in July of 1992 (10).
AIR
Ambient air quality was monitored at four sampling stations located along the perimeter of the landfill property and at one sampling station near the center of the landfill in October 1989. The results of this ambient air sampling indicated that VOC emission levels from the landfill were low and were similar to those previously reported during the RI sampling rounds in 1985 and 1986.
GROUNDWATER
Additional monitoring wells were installed on-site between 1989 and 1992. Groundwater monitoring at these and other wells was conducted during November 1989, March 1990, and January and March 1992. Sampling during these monitoring periods indicated the presence of high concentrations of volatile organic compounds (VOCs) and several inorganic contaminants (some of the inorganic contaminants are naturally occurring in this area of New Hampshire).
Analysis of the groundwater data indicates that the locations and concentration levels for various contaminants fluctuates. One explanation of this may be the fact that not all monitoring wells were sampled during each sampling round and that analytical limits exceeded health based comparison values on several occasions.
Detailed information on the concentrations of the contaminants of concern in groundwater at this site can be found in Tables 1 and 2. The most frequently detected chemicals at the Somersworth site are TCE, PCE and vinyl chloride.
Table 1: Somersworth Landfill On & Off-site Groundwater Analyses
Concentration Range in PPB For November 1989 and March 1990 Sampling Round
| Contaminant | 11-89 | 3-90 | Comparison Value | Source |
| Benzene | ND - 5 | ND - 6 | 1.2 | CREG |
| 1,2 Dichloroethane | ND | ND | 0.38 | CREG |
| Vinyl Chloride * | ND - 390 | ND - 520 | 0.2 | EMEG |
| Trichloroethene * | ND - 320 | ND - 9,000 | 5.0 | MCL |
| Tetrachloroethene | ND - 97 | ND -120 | 100 | RfD |
| 1,2 Cis & Trans Dichloroethene | ND - 580 | ND - 840 | 70 | LTHA |
| Methyl ethyl ketone | ND | ND | 200 | LTHA |
| Arsenic (in.) * | 4.8 - 148 | 1.7 - 33.3 | 3 | RMEG |
ND: Not detected
(*): Detection Limit for some samples exceed comparison value
NR: Not reported
CREG - Cancer Risk Evaluation Guide
EMEG - ATSDR's Environmental Media Evaluation Guide
RMEG - Reference Dose Media Evaluation Guide
MCL - EPA's Maximum Contaminant Level
RfD - EPA's Reference Dose
LTHA - EPA'S Drinking Water Lifetime Health Advisory
in. - inorganic
During the 1985 and 1986 sampling rounds TCE had been reported at concentrations ranging from not detected (ND) to 6 parts per billion (ppb) in on-site monitoring wells. This compound has been detected at high concentrations in off-site monitoring wells, but was not detected in two new on-site monitoring wells, during the November 1989 and March 1990. The analytical detection limits for TCE for those samples range from 5 ppb to 25 ppb. This detection limit range exceeds the current EPA Maximum Contaminant Level (MCL) for TCE which is 5 ppb. Thus, concentration levels of concern may have gone undetected.
Vinyl chloride, which had been detected in off-site monitoring wells at elevated levels during the November 1989 and March 1990 sampling rounds, was not detected in two on-site monitoring wells. Once again the detection limits exceeded health and technology based standards. The detection limits for vinyl chloride ranged from 10 ppb to 50 ppb in the samples from these wells. This range exceeds ATSDRs EMEG of 0.2 ppb for this chemical. The other five on-site groundwater monitoring wells, which were previously sampled for VOCs in 1985 and 1986, were not tested for trichloroethylene or vinyl chloride during November 1989, and March 1990 sampling round.
In January 1992, six on-site wells were sampled (OB-15R, OB-15U, OB-16R, OB-16U, OB-17R, OB-17U, see figure 1). More appropriate detection limits were used at this time. The results of this sampling round indicated very high on-site levels of TCE, PCE, and vinyl chloride. Maximum contaminant levels for four of the contaminants of concern were detected in monitoring well OB-17U and two other maximums were detected in monitoring well OB-17R. In March 1992 OB-17U and OB-17R were re-sampled resulting in similar findings. Maximum contaminant levels for five of the contaminants of concern were detected in monitoring well OB-17U. Wells OB-17U, which is screened in the overburden aquifer, and OB-17R, which is screened in the fractured bedrock aquifer, are located in the center of the site along the northern down gradient edge of the landfill.
Groundwater monitoring well sampling was conducted off-site in November 1989, and March 1990 (2). This sampling round confirmed the presence of elevated levels of VOCs in off-site groundwater. TCE was detected in monitoring wells north and west of the site at concentrations ranging from ND to 320 ppb. Vinyl chloride, which had not been tested for previously in these monitoring wells, was found at levels ranging from ND to 520 ppb. In monitoring wells south of the site across Blackwater Road, TCE was detected at concentrations ranging from ND to 9,000 ppb and vinyl chloride was found at concentrations from ND to 17 ppb.
In January 1992, eleven off-site wells were sampled (B-5L, OB-6U, OB-6R, OB-7U, OB-7R, OB-9R, B-12L,B-12R, OB-18U, OB-19U, OB-20U, see figure 1). Maximum contaminants levels for three of the contaminants of concern were detected in OB-6U, maximums for two contaminants were found in B-12R, and maximums for one each in OB-18U and OB-20U.
Table 2: Somersworth Landfill On and Off-site Groundwater Analyses
Concentration Range in PPB for January 1992 and March 1992 Sampling Round
| Contaminant | On (1-92) | Off (1-92) | On (3-92) | Off (3-92) | Comparison Value |
Source |
| Benzene | ND - 10 | ND - 2 | 8 - 11 | ND* - 1.5 | 1.2 | CREG |
| 1,2 Dichloroethane | ND - 7 | ND - 1 | ND - 11 | ND | 0.38 | CREG |
| Vinyl Chloride | 1- 1900 | ND - 14 | 68 - 1900 | ND* - 26 | 0.2 | EMEG |
| Trichloroethene | ND - 84 | ND - 6200 | 6 - 26 | ND - 5400 | 5.0 | MCL |
| Tetrachloroethane | ND | ND - 69 | ND | ND | 100 | RfD |
| 1,2 C&T Dichloroethene | ND - 1200 | ND - 250 | 130 - 1500 | 7 - 120 | 70 | LTHA |
| Methyl Ethyl Ketone | NR | NR | ND - 350 | ND* | 200 | LTHA |
| Bromomethane | ND | ND | ND - 20 | ND* | 14 | RfD |
| Arsenic (in.) | ND - 203 | ND - 25.5 | NR | NR | 3 | RMEG |
ND: Not detected
ND*: Detection Limit exceeds comparison value
NR: Not reported
CREG - Cancer Risk Evaluation Guide
EMEG - ATSDR's Environmental Media Evaluation Guide
RMEG - Reference Dose Media Evaluation Guide
MCL - EPA's Maximum Contaminant Level
RfD - EPA's Reference Dose
LTHA - EPA'S Drinking Water Lifetime Health Advisory
in. - inorganic
In March 1992, three off-site wells (B-13L, B-13R, B-12R, see figure 1) were sampled by the State of New Hampshire in order to confirm that contamination still existed along that portion of Blackwater Road. Results indicated the presence of four contaminants of concern at elevated levels. Two maximums concentrations were detected in B-12R and one each in the two other wells.
In July 1991, the State of New Hampshire sampled four residential wells located west of the landfill along Blackwater Road and one located on Cecile Street. The wells along Blackwater Road and on Cecile Street are considered upgradient of the plume of contamination. The results of the analyses indicated no volatile organic compounds (3).
In addition to groundwater sampling, Peter's Marsh Brook sediment was sampled in July 1992, by EPA as part of a yearly site assessment. Five sediment samples were analyzed for metals and VOCs. EPA has reported that contamination was not detected (10). Also, as part of the RI Data Gathering Report off-site soil gas monitoring was conducted. The results of this sampling indicated the presence of TCE, PCE and other soil gases. The presence of methane was not analyzed for in these samples.
D. Physical and Other Hazards
The possibility of methane generation from degradation of landfill wastes has not been addressed. The composition of waste materials deposited in landfills may allow for the production of methane, a highly explosive gas. Off site soil gas monitoring has indicated the presence of TCE, PCE and other soil gases. The presence of methane was not analyzed for in these samples.
During winter periods when topsoil is frozen, lateral movement of methane gas can result in potentially explosive conditions in the basement of homes and other confined spaces under conditions where venting is not provided. As was stated in the original health assessment, this site is surrounded by a residential neighborhood. One of the closest residences is a senior citizens complex located next to the recreation areas of the site (4). Additional information is needed before an assessment of the potential for physical hazard resulting from explosion can be made.
In addition to the potential explosive hazard, the existence of scrap metal at this site introduces a
small risk for cuts and scrapes to trespassers. There are also large appliances such as
refrigerators disposed of on-site. Depending on the position of the appliances a suffocation
hazard to children trespassing could exist. During the site visit it was observed that the risk of
this hazard was minimized by placing the refrigerator doors adjacent to the ground surface. In
this position it would be difficult for a child to gain entrance.
In this section of the public health assessment, the possible exposure pathways are evaluated to help determine whether persons have, are, or will be exposed to contaminants associated with the site. This pathway analysis consists of five elements (8):
| (1) | identifying contaminants of concern, |
| (2) | determining that these contaminants have/are/will be transported through an environmental medium, |
| (3) | identifying a point of exposure (i.e., a place or situation where humans might be exposed to the contaminated media), |
| (4) | determining that there is a plausible route of human exposure (i.e., can the contaminant enter the body?), and |
| (5) | identifying an exposed population (i.e., how many people, if any, are at the point of exposure). |
An exposure pathway is considered complete when there is good evidence that all five elements exist. The presence of a completed pathway indicates that human exposure to contaminants has occurred in the past, is currently occurring, or will occur in the future. When one or more of the five elements of an exposure pathway are missing, that pathway is considered potential. The presence of a potential exposure pathway indicates the human exposure to contaminants could have occurred in the past, could be occurring now, or could occur in the future. An exposure pathway can be eliminated if at least one of the five elements is missing and will never be present.
A. Completed Exposure Pathways
The surface water pathway is the only completed pathway at this site. Although the latest sampling conducted by EPA reportedly does not indicate sediment contamination in Peter's Marsh Brook, the brook has been observed to be contaminated by leachate from the landfill. Individuals who trespass at the site may come into contact with contaminated surface water through direct contact. The risk of this occurring is minimal however as this brook is not used regularly for recreational purposes.
B. Potential Exposure Pathways
A potential exposure pathway at this site exists for exposure to contaminated groundwater.
There currently are five known residences close to the landfill that are not connected to the
municipal water supply. These residences, located west of the site, are not expected to become
impacted by the northwesterly plume of contamination. The State of New Hampshire has
periodically monitored four of these wells. The fifth residence has recently been identified and
will be monitored in the future. The most recent monitoring results of July 1993 indicated that
no volatile organic compounds were detected in the wells. The state plans to continue
monitoring.
B. Health Outcome Data Evaluation
The Health Officer for the City of Somersworth has indicated that there are no known public health concerns or complaints by local residents regarding the Somersworth Sanitary Landfill Site at the present time (7). The latest available data from the New Hampshire State Cancer Registry indicated that there is no known increase in the cancer incidence rate for the City of Somersworth, NH at this point in time (6).
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