PUBLIC HEALTH ASSESSMENT ADDENDUM
SOMERSWORTH MUNICIPAL LANDFILL
SOMERSWORTH, STRAFFORD COUNTY, NEW HAMPSHIRE
HEALTH ASSESSMENT
FOR
SOMERSWORTH MUNICIPAL LANDFILL NPL SITE
01 NHD980520225
Somersworth, Strafford County, New Hampshire
March 1989
Prepared By The
Bureau of Health Risk Assessment
New Hampshire Division of Public Health Services (DPHS)
Department of Health and Human Services
Under A Cooperative Agreement With The
Agency for Toxic Substances and Diseases Registry (ATSDR)
United States Public Health Service
Department of Health and Human Services
The Somersworth Municipal Landfill National Priorities List (NPL) Site is located in a predominantly residential part of central Somersworth, New Hampshire, approximately one mile southwest of downtown Somersworth. The Town of Somersworth has operated a landfill on the 26-acre property since at least 1945. According to the U.S. Environmental Protection Agency (EPA), disposal operations at the site may have begun as early as the mid-1930s. The eastern ten acres of the landfill were reclaimed as a recreational park in 1981. on-site soils are contaminated with low levels of volatile organic compounds (VOCs), metals and polycyclic aromatic hydrocarbons (PAHs). Exposures to surface soils are expected to occur as a result of recreational activities at the site and the adjacent park. However, this media has not been analyzed. Therefore, the public health significance of this exposure pathway cannot be evaluated. Groundwater beneath the site is contaminated with low levels of VOCs. Groundwater migrating to the northwest is contaminated with VOCs, arsenic, chromium, and lead, at a level such that it is unfit for human consumption. The majority of the residences in the area of the site are connected to a municipal water supply. However, a number of wells are located in the vicinity of the site. The only well found to be contaminated by the landfill has been decommissioned. The site is located adjacent to a wetland and Peter's Marsh Brook, a tributary to the Salmon Falls River which supplies drinking water to Somersworth and Berwick, Maine. These wetlands are receiving leachate from the landfill and have been found to be contaminated with low levels of VOCs, phenols, arsenic, and mercury. Exposures to these waters are not expected to result in adverse health effects. The potential bioaccumulation of contaminants in edible aquatic organisms has not been evaluated. Based on information reviewed, the Agency for Toxic Substances and Disease Registry (ATSDR) has concluded that the Somersworth Landfill Site is of potential public health concern under current conditions because of the potential risk to human health resulting from possible exposure to hazardous substances at concentrations that may result in adverse health effects.
II. BACKGROUND
The Somersworth Municipal Landfill Site is located on the north side of Blackwater Road in the central portion of Somersworth, New Hampshire, approximately one mile southwest of downtown Somersworth. The site is listed on the U.S. Environmental Protection Agency's (EPA) National Priorities List (NPL). The approximately 26-acre site is located on land owned by the Town of Somersworth (see Figure 1). The Town has operated a disposal site on the property since at least 1945. According to EPA, disposal at the site may have begun as early as the mid-1930s. Disposal activities have led to the contamination of on-site soil and groundwater and off-site soil, groundwater, and surface waters with various volatile organic chemicals (VOCs), acid and base/neutral extractable compounds (ABNs), and inorganic compounds. The eastern-most ten acres of the site were reclaimed as a recreational park in 1978. Since 1981, the landfill has been inactive except for a stump dump.
The landfill is located in a predominantly residential area of Somersworth. The site is bordered to the north by a cemetery and two sand and gravel mining operations, to the east by Maple Street Extension, to the south by Blackwater Road, and to the west by Peter's Marsh Brook and associated wetlands. As indicated previously, the Forest Glade Park sits atop the eastern half of the landfill. The park consists of a playground, baseball diamonds, tennis courts, and a basketball court. An apartment building for elderly residents, a fire station, and a National Guard Armory abut the property to the east. Numerous single-family residences lie along Blackwater Road and Maple Street Extension. An elementary school is located approximately 1000 feet northeast of the landfill across the Maple Street Extension. An automobile salvage and scrap metal yard is located across Blackwater Road south of the site.
The former Somersworth Municipal Supply Well #3 is located approximately 2,300 feet to the north-northwest of the landfill. This well was decommissioned in 1984 and is being dismantled. Prior to 1984, it supplied approximately 10 percent of the Town's total water supply and was mainly used during peak periods. The water from the well had historically high levels of iron and manganese, which was a factor contributing to its decommissioning. Also in the area is the Somersworth Municipal Supply Well #4, located about 800 feet southwest of the landfill. This well has never been used as a municipal water supply source because of insufficient yield and high levels of iron. According to the town water superintendent, there are no plans to use this well in the future. Contaminants from the landfill have not been detected in either well.
Peter's Marsh Brook, located adjacent to the western edge of the landfill, is a tributary of Tate's Brook, which, in turn, is a tributary of the Salmon Falls River. Both the Town of Somersworth, New Hampshire, and the Town of Berwick, Maine, withdraw water from the river for their drinking water supplies. Water intakes are located approximately 1.5 miles north-northeast of the landfill, approximately 0.5 mile downstream of the confluence with Tate's Brook (see Figure 1). The river supplies drinking water to approximately 625 residents of downtown Berwick, and 25 to 30% of the approximately 11,000 residents of Somersworth.
Beginning around 1945, the town operated an open burning dump in the northeast corner of the landfill with an entrance road off of the Maple Street Extension. In 1958, the site was converted to a landfill for the disposal of household trash, business refuse, and industrial wastes generated in Somersworth. Although the landfill expanded generally westward, the full extent of refuse deposits are not known. Between 1962 and 1976, a garage was built in the southwest corner of the site and an entrance established off of Blackwater Road. Landfilling was reportedly stopped in the eastern portion of the site after 1975. Around that time, this section was proposed as a park. By 1978, the eastern section had been covered with soil and seeded. Cover material consisted primarily of sand overlain by a thin layer of topsoil. This was placed directly over the landfill cover, which itself consisted of sand. Construction of the park was completed in 1978.
Landfilling continued in the western section of the site until approximately April 1981 at which time the Town's solid waste began to be transported to an incinerator. Since 1981, the only wastes disposed of at the site consist of materials such as stumps, construction debris, household appliances, brush, and old furniture that cannot be incinerated.
There is no record of the amounts or types of wastes that were disposed of in the landfill. Up until July 1979, when the State adopted the Hazardous Waste Management Act, disposal of industrial wastes in this and other landfills was permissible. Local industries that may have disposed some or all of their wastes at the landfill include tanneries, bleacheries, shoe manufacturers, and metal finishing companies. The only information that does exist consists of telephone interviews conducted by the Strafford Regional Planning Commission to determine industrial waste quantities and composition in the Somersworth area. These surveys were compiled into a report entitled "Solid Waste Management Alternatives for Dover and Somersworth, New Hampshire: Detailed Report," (1). The results indicate that wastes consisted primarily of paper and plastic with lesser amounts of wood, rags, leather, and similar wastes. Scrap metal was reportedly recycled or sold to a scrap dealer. One industry was identified in the survey to have disposed chemical wastes at the landfill. Reported quantities were on the order of eighty 35-gallon drums per week. The types of chemical wastes were not reported.
Closure of the site began in June 1981 with the placement of four monitoring wells. An area approximately 350 feet by 400 feet along the northern portion of the site was "capped" with a one to two foot layer of sandy silt clay. Construction of the cover was terminated when the site was placed on EPA's interim list of 418 top-priority disposal sites.
A Draft Remedial Investigation (RI) was submitted in May, 1988 (2). This Health Assessment (HA) is being performed in connection with a forthcoming Record of Decision (ROD) for the site.
B. Site Visit
A site visit was conducted on July 27, 1988, by the New Hampshire Division of Public Health Services (NH DPHS). The visit was directed by the New Hampshire Department of Environmental Services (NH DES) Site Manager, Richard Pease.
Prior to entering the site, a tour of the surrounding area was conducted. The residential wells that have been monitored by the NH DES were pointed out. These are located about one mile west of the site near the junction of Blackwater Road and Route 16. Mr. Pease indicated that all of these wells have been free of contamination.
The site is accessed through an entrance off of Blackwater Road. When open, an attendant monitors dumping at an active stump dump. Wastes observed being dumped included brush, furniture, and old windows. The old landfill rises about 10-15 feet above ground level. The extreme western portion is unvegetated, probably because of constant vehicular traffic during dumping. The eastern section is vegetated with grasses up to knee height and a few scattered trees. The cover material at the stump dump appears to be a silty sand. Various mounds of dirt, gravel, cement, and other debris are scattered about this area from relatively recent dumping.
Peter's Marsh Brook and wetlands lie immediately west of the site. A newly constructed dirt road spurs off to the west into the wetlands, presumably for placement of a monitoring well. This road has obstructed the flow of the brook. When reformed north of the road, the brook appears heavily contaminated with rust-brown leachate. Observations of the brook further downstream revealed less opacity, yet it still appeared brown from leachate. The wetlands north of the site and east of Peter's Marsh Brook were similarly bright rust-brown with leachate.
A gas line access road runs along the northern border of the site between the landfill and the wetlands. Use of this road for biking and snowmobiling was indicated by Mr. Pease.
No discernible evidence of trespassing, such as tire tracks, beer bottles, etc., was observed at the site. However, use of the site for recreational purposes was confirmed by Mr. Pease, although the site's small size probably deters many trespassers. The site is easily accessible from all sides, except to automobiles.
The recreational park lies immediately adjacent to the stump dump. No barrier prevents access to the landfill. Other than portions of the baseball diamonds, the entire park is covered with grass. There was no evidence of erosion of the surface of the park. However, various depressions and upheavals were noted in the tennis courts and parking lot because of uneven settling of the underlying landfill. No one was observed using the park at the time of the visit. According to the town recreation department, little league baseball games are held five nights per week in the summer and the playground is used by day care groups.
III. ENVIRONMENTAL CONTAMINATION AND PHYSICAL HAZARDS
Environmental contamination at the Somersworth Landfill has been documented in on-site soils and groundwater and off-site soils, groundwater and surface water. The contaminants that have been detected include volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs), and metals. PCBs and pesticides were not detected on-site or off-site. The contaminants posing the greatest risks to human health were selected as contaminants of concern. Tables I and 2 summarize the levels of these chemicals detected in on-site and off-site media, respectively. The values presented are a summary of the maximum concentrations detected in multiple rounds of sampling. The park on the eastern half of the landfill is considered on-site.
Table 1 summarizes the levels of contamination present in on-site media. Sampling was performed in July-August 1985 and October-December 1986. The majority of sampling was performed off-site. Eleven test pits were dug on-site, seven of which were sampled for VOCs, and only two for metals, acid and base/neutral extractables (ABNs), pesticides and PCBs. One soil boring was located on-site. The soil was sampled for VOCs, metals, ABNs, pesticides and PCBs. Five monitoring wells were located on-site. The groundwater was analyzed for VOCs only. There was no surface water or sediments located on-site. On-site air monitoring was conducted during initial site reconnaissance in November 1984 using an HNu photoionization detector. No VOCs were detected at a detection limit of 1 ppm.
On-site subsurface soils and groundwater have displayed contamination with a number of substances. VOCs and PAHs were detected infrequently and at relatively low concentrations in on-site test pits and soil boring. Heavy metals were detected in all three samples analyzed but were present at concentrations below expected background levels. Groundwater sampling of on-site monitoring wells has revealed relatively low levels of a number of VOCs. Analyses for PAHs and inorganic compounds were not performed.
Table 2 summarizes off-site sampling results. Off-site sampling during the RI coincided with on-site sampling. Three test pits were dug off-site, yet were not sampled. Twelve soil borings were located off-site. All were analyzed for VOCs, 7 for metals, 9 for ABNs, and 9 for pesticides and PCBs. Twelve monitoring well clusters encompassing 26 sampling points were drilled off-site. All were analyzed for VOCs, 17 for metals, 19 for ABNS, and 5 for pesticides and PCBS. Seven surface water and 8 sediment stations, were sampled off-site. All samples were analyzed for VOCS. Three samples of each media were analyzed for the other parameters. Off-site air monitoring was conducted during the RI in January-February 1987 using an organic vapor meter (OVM). No VOCs were detected at a detection limit of 1 ppm.
Contamination from the landfill has migrated to off-site soils, groundwater and surface water. The levels of VOCs in off-site soil borings are comparatively lower than levels detected on-site. PAHs were detected in two soil borings at somewhat higher levels; however, heavy metals in off-site soils were comparable to on-site levels.
Table 1. On-Site Contaminants of Concern
The following table was not available in electronic format for conversion to HTML at the time of preparation of this document. To obtain a hard copy of the document, please contact:
Agency for Toxic Substances and Disease Registry
Division of Health Assessment and Consultation
Attn: Chief, Program Evaluation, Records, and Information Services
Branch, E-56
1600 Clifton Road NE, Atlanta, Georgia 30333
Table 2. Off-Site Contaminants of Concern
The following table was not available in electronic format for conversion to HTML at the time of preparation of this document. To obtain a hard copy of the document, please contact:
Agency for Toxic Substances and Disease Registry
Division of Health Assessment and Consultation
Attn: Chief, Program Evaluation, Records, and Information Services
Branch, E-56
1600 Clifton Road NE, Atlanta, Georgia 30333
VOCs in groundwater off-site are particularly elevated in monitoring wells northwest of the landfill and east of Peter's Marsh Brook. PAHs were not detected in off-site groundwater. Arsenic, chromium and lead were detected in downgradient groundwater samples above their respective U.S. Environmental Protection Agency (EPA) Maximum Contaminant Levels (MCLs) and Maximum Contaminant Level Goals (MCLGs).
Table 3 presents residential well sampling data contained in the RI. One residential well located on the south side of Blackwater Road was found to be contaminated with 76 ppb tetrahydrofuran in July 1985. Subsequent samples were determined to be uncontaminated. The only other detection of VOCs in a residential well was toluene at less than 5 ppb, which was suspected to be due to laboratory contamination. No contaminants from the landfill have been detected in Somersworth Well #3.
Low levels of several VOCs were detected in surface water samples from Peter's Marsh Brook and adjacent wetlands. One sediment sample also contained low levels of VOCS. Arsenic and mercury were the only inorganic contaminants of concern detected in surface water samples. The highest concentration of mercury (5.3 ug/1) was detected in a sample upstream of the site.
C. Physical Hazards
The only physical hazards identified on-site are associated with dumping activities at the stump dump. Various scrap metals, appliances, and glass were observed at the stump dump.
Residential Well Sampling
| Contaminant | Frequency a | Range | Mean b |
| Tetrahydrofuran | 1/12 | ND-76.0 | 76.0 |
| Toluene | 1/12 | ND-5 | 5 |
IV. DEMOGRAPHICS
The Somersworth Landfill is located in a predominantly residential area of town. Residential properties directly border the site to the south and east along Blackwater Road and Maple Street Extension, respectively. The Forest Glade Park is a recreation park that sets atop the eastern 10 acres of the old landfill. There are no barriers restricting access to the landfill from the park. A chain-link fence with a swinging bar gate along Blackwater Road is the only form of access restriction at the landfill. An apartment building for, elderly residents is located adjacent to the reclaimed park east of the landfill. Located east of Maple Street Extension, approximately 1,000 feet from the site, is the Maple Wood Elementary School with 420 pupils. Approximately 11,000 people live in Somersworth. An estimated 2,000 people live within a one-mile radius of the landfill. The majority of homes in the area obtain their drinking water from the Somersworth municipal supply. However, there are at least seven private wells in the area.
Other properties located near the site include a fire station, a National Guard armory, the General Linen Service Company, an automobile salvage and scrap yard, Forest Glade Cemetery, and two sand and gravel mining operations.
V. EVALUATION
Sampling during the RI included on-site subsurface soil and groundwater samples and off-site soil, groundwater, surface water, and air samples. No surface soil samples were taken on-site or off-site. Of the eight on-site subsurface soil samples, only three were analyzed for metals and ABNS. None of these three were located in the park. Consequently, the present condition of surface soils in the landfill and the park cannot be evaluated. Additional sampling would be required to fully characterize this medium.
Groundwater contamination migrating off-site is only characterized up to approximately 800 feet northwest of the site. The fate of contaminants beyond the monitoring well cluster at this location cannot be assessed without additional data. According to the EPA Remedial Project Manager, Roger Duwart, additional sampling has been proposed to determine the full extent of the contaminant plume.
Peter's Marsh Brook and adjacent wetlands have been sampled for VOCS; however, only three samples were analyzed for inorganic compounds and ABNS. Mercury was detected at 5.3 ug/l at a sampling point south of Blackwater Road, upstream of the site. Further characterization of the level of inorganics in Peter's Marsh Brook and potentially consumable aquatic organisms is necessary.
Information on the demographics of the population within a one-mile radius of the site was not provided in the RI. Seven residential wells were identified and sampled in a survey of the area. These wells are monitored by the NH DES. This Health Assessment is based on the site and surrounding wetlands remaining undeveloped.
This Health Assessment is based on information received by ATSDR, including the 1988 RI. It is assumed that the samples were handled properly and that the analytical data have been validated by a QA/QC review. The accuracy of the conclusions and recommendations contained within this Health Assessment is determined by the availability and reliability of the data.
Air monitoring conducted to date has not detected organic vapors at the landfill at a detection limit of 1 ppm. However, monitoring was conducted in the months of November, January and February, when volatilization would be expected to be minimal because of the cold climate. Despite this, detectable volatilization from the landfill is not expected given the low levels of VOCs detected in on-site soils.
Surface contaminants may be entrained in the air as a result of ongoing disposal activities or recreational use of the site. Contaminant levels in surface soils have not been evaluated. Therefore, the significance of this potential contaminant transport pathway cannot be assessed without additional data.
No intact drums were encountered during the RI; however, numerous crushed and deteriorated 55-gallon drums and 5-gallon cans were encountered in test pits. Soil borings and test pits on-site and off-site have contained relatively low levels of VOCS, PAHs, and inorganic compounds. Contaminant leaching from refuse, contaminated soil in the unsaturated zone, and potentially intact drums represent the primary transport pathways for contaminant migration from soils.
The flow of groundwater in the upper aquifer occurs in a westerly direction across the landfill, then northwesterly towards Peter's Marsh Brook and associated wetlands. Migration of contaminants by advective-dispersive transport is expected to follow the direction of groundwater flow.
Contamination has also migrated south of the landfill across Blackwater Road, presumably as a result of seasonal fluctuations in flow patterns, local variations in flow direction, and hydrodynamic dispersion at the limits of the plume.
The ultimate fate of groundwater contaminants in the upper aquifer appears to be discharge to Peter's Marsh Brook and adjacent wetlands. Analysis of the groundwater flow pattern indicates that groundwater underlying the landfill discharges to Peter's Marsh Brook and adjacent wetlands in an area north of Blackwater Road and south of the Somersworth Well #3.
The fate of contaminants in the bedrock aquifer is not clear. Consultation with NH DES personnel indicates that concentrations in bedrock wells north of the site have increased in recent sampling. The potential for further migration in the direction of residential wells or the drinking water intakes on Salmon Falls River is not known at this time.
The highest level of VOCs in groundwater was detected in two off-site monitoring well clusters: one located approximately 250 feet northwest of the landfill (13,266 ug/1), the other 100 feet south of the landfill across Blackwater Road (2,056 ug/1). Contamination exists in both the overburden and bedrock aquifers, with some stratification of VOCs based upon solubilities and specific gravities in the vicinity of the site. VOCs with relatively low aqueous solubilities and specific gravities greater than one (e.g., 1,1-dichloroethane, I,I-dichloroethylene, 1,2-dichloroethylene, trichloroethylene, and tetrachloroethylene) are present in higher concentrations in bedrock monitoring wells. Conversely, VOCs with low aqueous solubilities and specific gravities less than one (e.g., ethylbenzene, toluene, xylenes, methyl ethyl ketone, and methyl isobutyl ketone) are present in higher concentrations in overburden wells.
Peter's Marsh Brook and associated wetlands have been identified as the primary receptors for contaminants emanating from the landfill. To date, VOCS have been detected in surface water and sediment samples downgradient of the site. Discharge of contaminated groundwater is the principal source of these contaminants. Before discharging to surface waters, the groundwater must pass through a layer of peat approximately 15 to 25 feet thick. Because of the large percentage of organic carbon in peat, adsorption of VOCs and ABNs is expected to be a significant attenuation mechanism. Degradation and biotransformation by microbes in the peat is also anticipated to occur. once discharged to surface water, VOCs are expected to readily volatilize.
Sediment samples of Peter's Marsh Brook analyzed for inorganic compounds revealed higher concentrations of arsenic, chromium, and lead in the vicinity of the site. Desorption from sediments may release inorganic compounds to surface waters. Of these elements, only arsenic was present above detection limits in surface water samples. Therefore, the contribution of sediments to the inorganic contaminants in Peter's Marsh Brook does not appear to be significant.
The concentration of mercury in Peter's Marsh Brook was greater upstream of the site. The source of this contamination is not known.
Salmon Falls River is a potential receptor for surface water contaminants. However, based on a simple dilution analysis, a 35:1 dilution factor of Peter's Marsh Brook concentrations was estimated. Based on this analysis and the probable contributions of other attenuation mechanisms (e.g., volatilization, photodegradation, and biodegradation), contaminant concentrations in the vicinity of the municipal water supply intakes of Somersworth and Berwick resulting from surface water transport are not expected to be significant, if even detectable. However, without actual data, this pathway cannot be fully assessed.
The potential for contaminated groundwater in the bedrock aquifer to discharge to the river is not known. One sample taken of Salmon Falls River at the confluence with Tate's Brook did contain low levels of twelve VOCS. This sample, along with several other samples collected on the same day from other sampling points (including other media and another hazardous waste site), is considered suspect because of a similar profile of contaminants in each sample. No VOCs were detected in four subsequent sampling rounds.
A potential environmental pathway of contaminants in Peter's Marsh Brook is bioaccumulation in aquatic organisms. Arsenic, chromium, lead, and mercury all bioconcentrate in freshwater fish with bioconcentration factors ranging from 60 to 1000. Of the VOCs detected in surface water samples, only chloroform, tetrachloroethylene, and trichloroethylene have the potential to bioaccumulate in aquatic organisms. Any bioaccumulation that may occur would be weak to moderate, yet probably not a significant pathway in comparison to volatilization. Biomagnification in the food chain is not expected to occur.
Much of the area west and north of the landfill is undeveloped woodlands and wetlands. As a result, terrestrial mammals may frequent contaminated on-site and off-site areas. Animals drinking from Peter's Marsh Brook or eating vegetation that has accumulated contaminants may themselves accumulate contaminants. Except for terrestrial animals that spend a large percentage of their lifetimes in contaminated areas, this pathway is not expected to result in significant bioaccumulation of contaminants.
The environmental pathways most relevant to the site include entrainment of surface soils in the air; leaching of contaminants to groundwater; discharge of contaminated groundwater to Peter's Marsh Brook and associated wetlands; and potential bioaccumulation in aquatic organisms.
Air sampling for VOCs conducted in 1984 and 1987 does not indicate that exposure to these substances is likely to be an area of concern. The inhalation of fugitive dusts generated at the landfill, especially in those areas of the stump dump not covered with vegetation, may be an exposure pathway for stump dump employees and dumpers, as well as users of the park. The level of contamination present in surface soils and the ability of these soils to become entrained via atmospheric dispersion has not been evaluated. Therefore, the public health significance of this exposure pathway cannot be assessed.
Direct exposure to subsurface soils is unlikely. Ingestion and dermal contact with on-site and off-site surface soils, in addition to the inhalation pathway discussed above, represent probable exposure pathways because of the proximity of the park and the site's use as a recreational area. The landfill is accessible on all sides, including from the park. Surface soil analyses have not been performed, while only relatively low levels of contaminants have been detected in subsurface soils both on-site and off-site. However, the possibility remains that isolated hot spots of contaminants exist at the landfill and park that have not been identified. PAHs were detected in one of three on-site and two of nine off-site subsurface soil samples. The placement of cover material on the landfill in 1981 should reduce the likelihood of exposure to potentially contaminated soils. The material used to cover the landfill during park construction reportedly consisted of sand and a thin layer of topsoil. No evidence of erosion of this layer was observed at the park. However, the integrity of this cover has not been assessed.
The groundwater beneath the landfill and extending northwestward towards Peter's Marsh Brook is unfit for human consumption. Although the majority of homes in the area obtain their drinking water from a municipal supply, there are at least seven private wells in the area located upgradient from the site. These wells are monitored by the NH DES and have been found to be free of contamination. However, contamination of one downgradient well south of Blackwater Road has been documented and this well has been decommissioned.
The two municipal wells near the site, Somersworth Wells #3 and #4, are not currently being used as water supplies. Well #3 is being dismantled. Data do not indicate that this well was ever at risk of contamination from the site. Well #4 has never been used as a municipal water supply. According to the Town's public works director, there are no plans to use this well in the future. Exposure to contaminated municipal water supplies is, therefore, not an area of concern.
The Peter's Marsh Brook and associated wetlands are not waters expected to be used for drinking, swimming, or fishing. The levels of contaminants detected in these waters are generally low, although benzene and trichloroethylene were detected at levels close to or in excess of their respective MCLS. Mercury was detected in one upstream surface water sample at 5.3 ug/l. This level is above the MCL (2 ppb) and proposed MCLG (3 ppb). Exposures to these surface waters, including leachate seeps, may occur as a result of children wading in the wetlands, although evidence of this exposure has not been observed.
Contaminant concentrations in Salmon Falls River in the vicinity of the drinking water intakes for Somersworth and Berwick are not expected to reach toxic levels. Therefore, this medium is not likely to result in human exposure to site contaminants at a level of concern.
According to the RI report, Peter's Marsh Brook is heavily fished with a large population of native trout. Compounds, particularly mercury, may bioaccumulate in edible aquatic organisms. Mercury was present above the U.S. EPA Ambient Water Quality Criteria for freshwater fish (acute 2.4 ppb, chronic 0.012 ppb). It was also present above the Water Quality Criteria for water and fish ingestion (144 ppt) and fish consumption (146 ppt). Consumption of aquatic organisms that have bioaccumulated compounds is a potential exposure pathway, the significance of which is not known at this time.
Portions of the area surrounding the landfill may be suitable for hunting. However, the extent of hunting in the area is limited in scope by new residential and commercial properties that are encroaching into the woodlands. Animals that have spent a large proportion of their lifetimes in contaminated areas and that have bioaccumulated contaminants, represent a potential human exposure pathway. However, unless game animals were to comprise a major proportion of an individual's daily intake, this exposure pathway is not expected to result in significant chemical exposure.
The human exposure pathways of primary public health concern are direct contact, ingestion, and inhalation of potentially contaminated soils; direct contact and incidental ingestion of contaminated surface water; ingestion, direct contact, and inhalation of vapors from contaminated groundwater; and consumption of potentially contaminated fish.
VI. PUBLIC HEALTH IMPLICATIONS
Disposal activities at the site have led to contamination of on-site soils and groundwater. In the event that the site is developed, exposure to subsurface soils may be a concern. PAHs were detected in soils. Long-term exposure to PAHs may increase the risk of developing cancer. However, at this time there does not appear to be any human exposure to this medium. Ingestion, inhalation, and direct contact with surface soils, especially in Forest Glade Park, are probable exposure pathways. The level of contamination in this soil has not been determined. Therefore, a definitive assessment of this medium cannot be made at this time. Groundwater beneath the site is unfit for human consumption. Exposure to contaminants in groundwater may result in both acute and chronic adverse health effects, including an increased risk of cancer. There does not appear, however, to be any current exposure to this medium.
Contaminants are migrating off-site in groundwater and surface water. The groundwater migrating northwest of the site is unfit for human consumption. However, there are no known withdrawals from this source at this time. The majority of residences in the area are connected to a municipal supply. The residential wells that do exist are located west of the site and have been found to be free of contamination. In the event that further development occurs in the area, treatment of this water, or an alternate supply, would be necessary to prevent exposure to contaminants. Exposure to contaminated groundwater may result in acute and chronic adverse health effects, including cancer.
Various contaminants of concern have been detected in Peter's Marsh Brook and associated wetlands, including carcinogens (arsenic, benzene, dichloromethane, tetrachloroethylene and trichloroethylene) and noncarcinogens (mercury). While these waters are not expected to be used for consumptive purposes, other exposures, such as dermal contact and accidental ingestion, would be a concern if children were to frequently wade in the brook. The primary health concern would be an increased risk of developing cancer as a result of repeated exposure. Such exposures, although possible, are not considered likely due to the location of the wetlands.
VII. CONCLUSIONS AND RECOMMENDATIONS
VIII. PREPARERS OF REPORT
| New Hampshire Staff: | Jeffrey S. Smith, MSPH Environmental Health Specialist NH Division of Public Health Services Ellen Cavalier, MPH |
| Regional Representative: | Marilyn DiStrio Regional Representative Office of External Affairs Field Operations Branch |
| Technical Co-project Officer: | Clifford L. Moseley, CIH Project Officer Office of Health Assessments Health Sciences Branch |
| Typist: | Tammy Brasier Word Processing Operator NH Division of Public Health Services |
IX. REFERENCES
FIGURES
| Figure 1. | Map of Groundwater Flow Direction and Monitoring Well Location |
| Figure 2. | Map of Somersworth, NH |
Figure 1. Map of Groundwater Flow
Direction and Monitoring Well Location
Figure 2. Map of Somersworth, NH
Public Comments and Responses on the Addendum
to the Public Health Assessment
Responsiveness Summary
| 1. Comment: | The Somersworth Sanitary Landfill site is inappropriately categorized in the
Addendum as an "indeterminate public health hazard". |
| Response: | The purpose of the Pubic Health Assessment is to assess any current or future health
impact resulting from the release of hazardous substances into the environment, to develop health
advisories or other appropriate recommendations, and to identify studies or other actions needed
to evaluate and prevent adverse health effects. The product of a public health assessment is the
development of a set of conclusions and recommendations which guide further public health
actions for the site. A critical conclusion for each public health assessment involves identifying
the level of public health hazard associated with the site.
The indeterminate public health hazard category was created to indicate a level of hazard when available data does not indicate that humans are being or have been exposed to levels of contamination that would be expected to cause adverse health effects but data and information are not available for all environmental media to which humans may have been exposed. ATSDR and the New Hampshire Division of Public Health Services, in the Addendum to the Public Health Assessment categorized the site as an indeterminate public health hazard. This categorization of the site was appropriate given that 1) the available data does not indicate that humans have been or currently are being exposed to site related contaminants at levels that would be expected to cause adverse health effects, and 2) data are not available for all environmental media which may pose a risk to humans living at or near the site. The Addendum identified the lack of information on the generation of explosive gases (methane) in the landfill as a data gap (refer to Summary, paragraph 2) and indicated that the risk associated with this pathway could not be assessed without additional data. The Addendum contained a recommendation that soil gas sampling be conducted to assess the potential explosive hazard risk to buildings surrounding the landfill. It is important that the public health assessment evaluate all potential pathways of concern given
that explosive levels of landfill gases have been documented at other landfills that are in similar
environmental settings and that serious injuries or deaths have been reported as the result of
landfill gas fires and explosions. The conclusion that ATSDR and NH DPHS adopted to
characterize the level of hazard for the site (indeterminate public health hazard) is therefore
appropriate. The recommendation that soil gas sampling be conducted to evaluate the potential
explosive hazard of methane and other landfill generated gases is a valid and prudent public
health recommendation. |
| 2. Comment: | There is no methane explosion risk associated with the landfill site. |
| Response: | The addendum identified the lack of information on the presence of explosive gases
(methane) in the landfill as a data gap. The Addendum concluded that the Somersworth Sanitary
Landfill site constitutes an indeterminate public health hazard because of this data gap and
recommended that "soil gas sampling be conducted to assess the potential explosive hazard risks
to buildings surrounding the landfill" (see Recommendations). It is ATSDR' and NH DPHS'
position that there is insufficient information to evaluate methane gas as an explosive hazard.
There are no environmental measurements, such as soil gas analyses for methane or other
explosive gases, upon which an evaluation of the potential hazard posed by landfill generated
gases can be based. Although it is possible to derive theoretical calculations for methane gas
generation at the landfill, these calculations are not a substitute for the gathering of empirical
information from field and laboratory studies. Explosive levels of soil gases have been
documented at other landfills in environmental settings similar to the Somersworth Sanitary
Landfill site. Serious injuries and deaths from landfill gas fires can occur and have been
documented in the past. It is because of the potentially serious consequences that can result from
landfill gas fires and explosions, that actual measurements rather than theoretical calculations be
used to determine the existence or absence of a fire or explosion hazard at the site.
As indicated in Comment #1, the categorization of the Somersworth Sanitary Landfill site as an indeterminate public health hazard is appropriate given this data gap and the recommendation
that soil gas sampling be conducted to assess the risk associated with landfill fires and explosions is a necessary public health recommendation. |
| 3. Comments: | The three active municipal wells and the residential wells mentioned in the
Addendum are not at risk to contamination from the Somersworth Sanitary Landfill site. |
| Response: | The Addendum did not indicate that the three municipal wells or the five currently
active residential wells are at risk to site related contaminants (refer Demographics, Land Use
and National Resource Use, paragraph 1). The wells were mentioned relative to a discussion of
existing water supplies located in the site area. This section of the Addendum reviews
demographic information and land use at or near the site in order to evaluate the types and
frequency of activities of the surrounding population and the probability for human exposure.
The information presented in this section of the Addendum is then used in combination with the information gathered relative to environmental contamination and the analysis of exposure pathways to develop conclusions about the public health significance of the site and to make recommendations for future public health actions. The Addendum initially stated that there were four active residential wells in the area of Landfill.
Recent consultation with the DES Remedial Project Manager for the Somersworth Sanitary
Landfill site revealed that there currently are five active residential wells in the area of the Landfill. |
| 4. Comment: | There is no risk from fishing in the manmade pond located at the confluence of
Peter's Marsh Brook and Tates Brook. |
| Response: | Similar to comment #3, the recreational fishing in the pond located north of the
landfill was identified in the Demographic, Land Use and Natural Resource Use section of the
Addendum as an example of the type of human activity which could contribute to exposure to
site related contaminants and which would be evaluated in the Addendum. The Addendum does
not identify the consumption of fish from this pond as a source of risk. The Addendum does
state that the sediment of Peter Marsh's Brook was sampled by EPA in July, 1992 as part of the
yearly site assessment (refer Environmental Contamination and Physical Hazards, B. Off-site
Contamination, paragraph 5). The sediment samples were analyzed for VOCs and metals. EPA
reported that contamination was not detected in these samples. |
| 5. Comment: | It is incorrectly stated in Table 1 of the Addendum that the detection limits used for
trichloroethene (TCE) and vinyl chloride were in excess of the current EPA Maximum
Contaminant Levels (MCL) for the two compounds. The detection limits for these two
compounds was actually l part per billion (ppb), which is below the MCL. |
| Response: | The current MCL for TCE is 5 ppb and for vinyl chloride, 2 ppb. The information
presented in Table 1 of the Addendum is taken from the Remedial Investigation Data Gathering
Report for the Somersworth Landfill (1992). A review of Table 10 of the Data Gathering Report,
which summarizes the volatile organic compound (VOC) analyses for on-site and off-site
groundwater for 1989 and 1990, reveals that the detection limits reported for TCE and vinyl
chloride exceeds 1 ppb and the MCLs for the respective compounds for some of the samples
represented. One example is Sample #5009-10 collected from monitoring well OB-3, sampled
November 11, 1989 which indicated that no TCE was detected with a detection limit of 25 ppb
and no vinyl chloride was detected with a detection limit of 50 ppb.
VOC analyses data for groundwater samples collected during 1989 and 1990 have been reviewed
and Table 1 of the Addendum has been updated to reflect that there were samples where the detection limits for TCE and vinyl chloride were below the
respective MCLs. |
| 6. Comment: | There are various errors contained in the data tables in the Addendum relative to
the reporting of detection limits and contaminant levels found in groundwater samples collected
during 1989 and 1990. For example, Table 1 of the Addendum indicates that the detection limits
for 1,2 clichloroethane were 25 and 50 ppb when, in fact, detection limits of 1 and 5 ppb were
used in connection with the samples collected during this time period. In addition, Table 1
indicates that all groundwater samples contained detectable concentrations of vinyl chloride,
trichloroethene (TCE), tetrachloroethene (PCE), and arsenic when, in every case, there were
measurements where the contaminants were at non-detectable levels. The Table also indicates
that methyl ethyl ketone was not analyzed for in the samples when, in fact, it was analyzed for
and detected. |
| Response: | As indicated in the response to comment #5, the information presented in the data
tables in the Addendum is taken from the Remedial Investigation Data Gathering Report for the
Somersworth Landfill (1992). The Data Gathering Report contains a summary of the volatile
organic compound analyses for groundwater for 1989 and 1990. This data indicates that, with
respect to 1,2 dichloroethane, the detection limits were in the range 1-50 ppb for the samples
analyzed during this period. For example, sample #5032-6 from monitoring well B-8L, which
was collected in 1989, indicated that 1,2 dichloroethane was not detected with a detection limit
of 25 ppb. The Addendum identified the Cancer Risk Evaluation Guide for 1,2
dichloroethane(0.38 ppb) as the appropriate comparison value for the evaluation of the risk posed
by this chemical. There is a concern that, for samples where the analytical detection limits
exceed the comparison value, 1,2 dichloroethane may exist at significantly elevated levels and go undetected.
The situation is similar for other chemicals identified in this comment. A range of detection limits were reported for vinyl chloride, TCE, PCE, and arsenic for the groundwater samples collected during 1989 and 1990. For vinyl chloride, TCE, and arsenic, there are samples where the reported detection limits exceed the comparison values specified in Table 1. It is possible that there may be concentrations of these chemicals in these samples at levels of public health concern that could go undetected. This would affect the evaluation of the risk posed by exposure to these chemicals in groundwater and could result in an underestimate of risk. Finally, a review of the groundwater monitoring data contained in the 1992 Data-Gathering
Report indicated that the groundwater samples collected in 1989 and 1990 were analyzed for
methyl ethyl ketone. Methyl ethyl ketone was identified in the Data- Gathering Report by its
synonym, 2-butanone. The levels of methyl ethyl ketone found in these samples appear to be
below the chosen comparison value (Lifetime Health Advisory-200 ppb) for this chemical. |
| 7. Comment: | The Addendum originally stated that there were "observed anomalies with respect
to contamination and direction of groundwater flow" and that this statement was one of the bases
for concluding that the site is an indeterminate public health hazard. The data collected to date
shows that the contaminated groundwater flows away from the residences and discharges into the
wetlands adjacent to the site. There is no basis for concluding that existing residential wells are at risk from contaminated groundwater. |
| Response: | The categorization of the Somersworth Sanitary Landfill site as an indeterminate
public health hazard was based on the identification of a data gap for the evaluation of soil gases
as an explosive hazard. Refer to the response to Comment #1 for a discussion of this matter.
The Addendum does not state that the residential wells identified in the area of the landfill are at
risk to contaminated groundwater. The Addendum indicates that these wells are upgradient of
the site and states that "these residences are not expected to become impacted by the
northwesterly plume of contamination." (refer to Pathways Analysis, B, Potential Exposure
Pathways). |
| 8. Comment: | Cecile Street is upgradient from the Landfill as are other existing residential wells
located on Blackwater Road. |
| Response: | A recent discussion with the DES Remedial Project Manager for the Somersworth Sanitary Landfill site indicated that the active residential wells located on Cecile Street and Blackwater Road are upgradient from the Landfill. Information as to the location of the residential well on Cecile Street was not available to ATSDR at the time that the July 7, 1992 site visit was made. |
