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PUBLIC HEALTH ASSESSMENT ADDENDUM

SOMERSWORTH MUNICIPAL LANDFILL
SOMERSWORTH, STRAFFORD COUNTY, NEW HAMPSHIRE


APPENDIX A


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


I. SUMMARY

The Somersworth Municipal Landfill National Priorities List (NPL) Site is located in apredominantly residential part of central Somersworth, New Hampshire, approximately one milesouthwest of downtown Somersworth. The Town of Somersworth has operated a landfill on the26-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 tenacres of the landfill were reclaimed as a recreational park in 1981. on-site soils are contaminatedwith low levels of volatile organic compounds (VOCs), metals and polycyclic aromatichydrocarbons (PAHs). Exposures to surface soils are expected to occur as a result of recreationalactivities 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 migratingto the northwest is contaminated with VOCs, arsenic, chromium, and lead, at a level such that itis unfit for human consumption. The majority of the residences in the area of the site areconnected to a municipal water supply. However, a number of wells are located in the vicinity ofthe site. The only well found to be contaminated by the landfill has been decommissioned. Thesite is located adjacent to a wetland and Peter's Marsh Brook, a tributary to the Salmon FallsRiver which supplies drinking water to Somersworth and Berwick, Maine. These wetlands arereceiving leachate from the landfill and have been found to be contaminated with low levels ofVOCs, phenols, arsenic, and mercury. Exposures to these waters are not expected to result inadverse health effects. The potential bioaccumulation of contaminants in edible aquaticorganisms has not been evaluated. Based on information reviewed, the Agency for ToxicSubstances and Disease Registry (ATSDR) has concluded that the Somersworth Landfill Site isof 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

    A. Site Description

The Somersworth Municipal Landfill Site is located on the north side of Blackwater Road in thecentral portion of Somersworth, New Hampshire, approximately one mile southwest ofdowntown 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 ownedby the Town of Somersworth (see Figure 1). The Town has operated a disposal site on theproperty since at least 1945. According to EPA, disposal at the site may have begun as early asthe mid-1930s. Disposal activities have led to the contamination of on-site soil and groundwaterand off-site soil, groundwater, and surface waters with various volatile organic chemicals(VOCs), acid and base/neutral extractable compounds (ABNs), and inorganic compounds. Theeastern-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 miningoperations, to the east by Maple Street Extension, to the south by Blackwater Road, and to thewest by Peter's Marsh Brook and associated wetlands. As indicated previously, the Forest GladePark sits atop the eastern half of the landfill. The park consists of a playground, baseballdiamonds, 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-familyresidences lie along Blackwater Road and Maple Street Extension. An elementary school islocated 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 thenorth-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 wasmainly used during peak periods. The water from the well had historically high levels of ironand manganese, which was a factor contributing to its decommissioning. Also in the area is theSomersworth Municipal Supply Well #4, located about 800 feet southwest of the landfill. Thiswell has never been used as a municipal water supply source because of insufficient yield andhigh 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'sBrook, 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 theirdrinking water supplies. Water intakes are located approximately 1.5 miles north-northeast ofthe 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, and25 to 30% of the approximately 11,000 residents of Somersworth.


Figure 1. Somersworh Landfill

Beginning around 1945, the town operated an open burning dump in the northeast corner of thelandfill with an entrance road off of the Maple Street Extension. In 1958, the site was convertedto a landfill for the disposal of household trash, business refuse, and industrial wastes generatedin Somersworth. Although the landfill expanded generally westward, the full extent of refusedeposits are not known. Between 1962 and 1976, a garage was built in the southwest corner ofthe site and an entrance established off of Blackwater Road. Landfilling was reportedly stoppedin the eastern portion of the site after 1975. Around that time, this section was proposed as apark. By 1978, the eastern section had been covered with soil and seeded. Cover materialconsisted primarily of sand overlain by a thin layer of topsoil. This was placed directly over thelandfill 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 whichtime the Town's solid waste began to be transported to an incinerator. Since 1981, the onlywastes disposed of at the site consist of materials such as stumps, construction debris, householdappliances, 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. Upuntil July 1979, when the State adopted the Hazardous Waste Management Act, disposal ofindustrial wastes in this and other landfills was permissible. Local industries that may havedisposed some or all of their wastes at the landfill include tanneries, bleacheries, shoemanufacturers, and metal finishing companies. The only information that does exist consists oftelephone interviews conducted by the Strafford Regional Planning Commission to determineindustrial waste quantities and composition in the Somersworth area. These surveys werecompiled into a report entitled "Solid Waste Management Alternatives for Dover andSomersworth, New Hampshire: Detailed Report," (1). The results indicate that wastes consistedprimarily 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 areaapproximately 350 feet by 400 feet along the northern portion of the site was "capped" with a oneto two foot layer of sandy silt clay. Construction of the cover was terminated when the site wasplaced 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 thesite.

B. Site Visit

A site visit was conducted on July 27, 1988, by the New Hampshire Division of Public HealthServices (NH DPHS). The visit was directed by the New Hampshire Department ofEnvironmental Services (NH DES) Site Manager, Richard Pease.

Prior to entering the site, a tour of the surrounding area was conducted. The residential wellsthat have been monitored by the NH DES were pointed out. These are located about one milewest 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 attendantmonitors 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. Theextreme western portion is unvegetated, probably because of constant vehicular traffic duringdumping. The eastern section is vegetated with grasses up to knee height and a few scatteredtrees. 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 dirtroad 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 brookappears heavily contaminated with rust-brown leachate. Observations of the brook furtherdownstream 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 thesite. However, use of the site for recreational purposes was confirmed by Mr. Pease, althoughthe 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 accessto the landfill. Other than portions of the baseball diamonds, the entire park is covered withgrass. There was no evidence of erosion of the surface of the park. However, variousdepressions and upheavals were noted in the tennis courts and parking lot because of unevensettling 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 soilsand groundwater and off-site soils, groundwater and surface water. The contaminants that havebeen detected include volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons(PAHs), and metals. PCBs and pesticides were not detected on-site or off-site. Thecontaminants 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 inmultiple rounds of sampling. The park on the eastern half of the landfill is considered on-site.

    A. On-site Contamination

Table 1 summarizes the levels of contamination present in on-site media. Sampling wasperformed in July-August 1985 and October-December 1986. The majority of sampling wasperformed 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. Onesoil boring was located on-site. The soil was sampled for VOCs, metals, ABNs, pesticides andPCBs. Five monitoring wells were located on-site. The groundwater was analyzed for VOCsonly. There was no surface water or sediments located on-site. On-site air monitoring wasconducted during initial site reconnaissance in November 1984 using an HNu photoionizationdetector. No VOCs were detected at a detection limit of 1 ppm.

On-site subsurface soils and groundwater have displayed contamination with a number ofsubstances. VOCs and PAHs were detected infrequently and at relatively low concentrations inon-site test pits and soil boring. Heavy metals were detected in all three samples analyzed butwere 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 forPAHs and inorganic compounds were not performed.

    B. Off-site Contamination

Table 2 summarizes off-site sampling results. Off-site sampling during the RI coincided withon-site sampling. Three test pits were dug off-site, yet were not sampled. Twelve soil boringswere located off-site. All were analyzed for VOCs, 7 for metals, 9 for ABNs, and 9 forpesticides and PCBs. Twelve monitoring well clusters encompassing 26 sampling points weredrilled off-site. All were analyzed for VOCs, 17 for metals, 19 for ABNS, and 5 for pesticidesand PCBS. Seven surface water and 8 sediment stations, were sampled off-site. All sampleswere 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 organicvapor 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 thelandfill 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 theirrespective 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 locatedon the south side of Blackwater Road was found to be contaminated with 76 ppb tetrahydrofuranin July 1985. Subsequent samples were determined to be uncontaminated. The only otherdetection of VOCs in a residential well was toluene at less than 5 ppb, which was suspected to bedue to laboratory contamination. No contaminants from the landfill have been detected inSomersworth Well #3.

Low levels of several VOCs were detected in surface water samples from Peter's Marsh Brookand adjacent wetlands. One sediment sample also contained low levels of VOCS. Arsenic andmercury were the only inorganic contaminants of concern detected in surface water samples. Thehighest 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.



Table 3.

Residential Well Sampling
ContaminantFrequency aRangeMean b
Tetrahydrofuran1/12ND-76.076.0
Toluene1/12ND-55
          a - 12 samples of 7 wells
          b - mean of detected concentrations

IV. DEMOGRAPHICS

The Somersworth Landfill is located in a predominantly residential area of town. Residentialproperties directly border the site to the south and east along Blackwater Road and Maple StreetExtension, respectively. The Forest Glade Park is a recreation park that sets atop the eastern 10acres of the old landfill. There are no barriers restricting access to the landfill from the park. Achain-link fence with a swinging bar gate along Blackwater Road is the only form of accessrestriction at the landfill. An apartment building for, elderly residents is located adjacent to thereclaimed park east of the landfill. Located east of Maple Street Extension, approximately 1,000feet 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 aone-mile radius of the landfill. The majority of homes in the area obtain their drinking waterfrom the Somersworth municipal supply. However, there are at least seven private wells in thearea.

Other properties located near the site include a fire station, a National Guard armory, the GeneralLinen Service Company, an automobile salvage and scrap yard, Forest Glade Cemetery, and twosand and gravel mining operations.

V. EVALUATION

    A. Site Characterization
    1. Environmental Media

Sampling during the RI included on-site subsurface soil and groundwater samples and off-sitesoil, groundwater, surface water, and air samples. No surface soil samples were taken on-site oroff-site. Of the eight on-site subsurface soil samples, only three were analyzed for metals andABNS. None of these three were located in the park. Consequently, the present condition ofsurface soils in the landfill and the park cannot be evaluated. Additional sampling would berequired to fully characterize this medium.

Groundwater contamination migrating off-site is only characterized up to approximately 800 feetnorthwest of the site. The fate of contaminants beyond the monitoring well cluster at thislocation cannot be assessed without additional data. According to the EPA Remedial ProjectManager, Roger Duwart, additional sampling has been proposed to determine the full extent ofthe contaminant plume.

Peter's Marsh Brook and adjacent wetlands have been sampled for VOCS; however, only threesamples were analyzed for inorganic compounds and ABNS. Mercury was detected at 5.3 ug/l ata sampling point south of Blackwater Road, upstream of the site. Further characterization of thelevel of inorganics in Peter's Marsh Brook and potentially consumable aquatic organisms isnecessary.

    2. Land Use and Demographics

Information on the demographics of the population within a one-mile radius of the site was notprovided 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 andsurrounding wetlands remaining undeveloped.

    3. Quality Assurance/Quality Control (QA/QC)

This Health Assessment is based on information received by ATSDR, including the 1988 RI. Itis assumed that the samples were handled properly and that the analytical data have beenvalidated by a QA/QC review. The accuracy of the conclusions and recommendations containedwithin this Health Assessment is determined by the availability and reliability of the data.

    B. Environmental Pathways
    1. Air

Air monitoring conducted to date has not detected organic vapors at the landfill at a detectionlimit of 1 ppm. However, monitoring was conducted in the months of November, January andFebruary, 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 orrecreational use of the site. Contaminant levels in surface soils have not been evaluated. Therefore, the significance of this potential contaminant transport pathway cannot be assessedwithout additional data.

    2. Soil

No intact drums were encountered during the RI; however, numerous crushed and deteriorated55-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 potentiallyintact drums represent the primary transport pathways for contaminant migration from soils.

    3. Groundwater

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 ofcontaminants by advective-dispersive transport is expected to follow the direction ofgroundwater 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, andhydrodynamic dispersion at the limits of the plume.

The ultimate fate of groundwater contaminants in the upper aquifer appears to be discharge toPeter's Marsh Brook and adjacent wetlands. Analysis of the groundwater flow pattern indicatesthat groundwater underlying the landfill discharges to Peter's Marsh Brook and adjacent wetlandsin 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 thesite have increased in recent sampling. The potential for further migration in the direction ofresidential 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 feetsouth of the landfill across Blackwater Road (2,056 ug/1). Contamination exists in both theoverburden and bedrock aquifers, with some stratification of VOCs based upon solubilities andspecific gravities in the vicinity of the site. VOCs with relatively low aqueous solubilities andspecific gravities greater than one (e.g., 1,1-dichloroethane, I,I-dichloroethylene, 1,2-dichloroethylene, trichloroethylene, and tetrachloroethylene) are present in higher concentrationsin bedrock monitoring wells. Conversely, VOCs with low aqueous solubilities and specificgravities less than one (e.g., ethylbenzene, toluene, xylenes, methyl ethyl ketone, and methylisobutyl ketone) are present in higher concentrations in overburden wells.

    4. Surface Water

Peter's Marsh Brook and associated wetlands have been identified as the primary receptors forcontaminants emanating from the landfill. To date, VOCS have been detected in surface waterand sediment samples downgradient of the site. Discharge of contaminated groundwater is theprincipal source of these contaminants. Before discharging to surface waters, the groundwatermust pass through a layer of peat approximately 15 to 25 feet thick. Because of the largepercentage of organic carbon in peat, adsorption of VOCs and ABNs is expected to be asignificant attenuation mechanism. Degradation and biotransformation by microbes in the peat isalso anticipated to occur. once discharged to surface water, VOCs are expected to readilyvolatilize.

Sediment samples of Peter's Marsh Brook analyzed for inorganic compounds revealed higherconcentrations of arsenic, chromium, and lead in the vicinity of the site. Desorption fromsediments may release inorganic compounds to surface waters. Of these elements, only arsenicwas present above detection limits in surface water samples. Therefore, the contribution ofsediments 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. Thesource 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'sMarsh Brook concentrations was estimated. Based on this analysis and the probablecontributions of other attenuation mechanisms (e.g., volatilization, photodegradation, andbiodegradation), contaminant concentrations in the vicinity of the municipal water supply intakesof Somersworth and Berwick resulting from surface water transport are not expected to besignificant, if even detectable. However, without actual data, this pathway cannot be fullyassessed.

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 didcontain low levels of twelve VOCS. This sample, along with several other samples collected onthe same day from other sampling points (including other media and another hazardous wastesite), is considered suspect because of a similar profile of contaminants in each sample. NoVOCs were detected in four subsequent sampling rounds.

    5. Food Chain Contamination

A potential environmental pathway of contaminants in Peter's Marsh Brook is bioaccumulationin aquatic organisms. Arsenic, chromium, lead, and mercury all bioconcentrate in freshwater fishwith bioconcentration factors ranging from 60 to 1000. Of the VOCs detected in surface watersamples, only chloroform, tetrachloroethylene, and trichloroethylene have the potential tobioaccumulate in aquatic organisms. Any bioaccumulation that may occur would be weak tomoderate, 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. Animalsdrinking from Peter's Marsh Brook or eating vegetation that has accumulated contaminants maythemselves accumulate contaminants. Except for terrestrial animals that spend a large percentageof their lifetimes in contaminated areas, this pathway is not expected to result in significantbioaccumulation of contaminants.

    6. Summary

The environmental pathways most relevant to the site include entrainment of surface soils in theair; leaching of contaminants to groundwater; discharge of contaminated groundwater to Peter'sMarsh Brook and associated wetlands; and potential bioaccumulation in aquatic organisms.

    C. Human Exposure Pathways
    1. Air

Air sampling for VOCs conducted in 1984 and 1987 does not indicate that exposure to thesesubstances is likely to be an area of concern. The inhalation of fugitive dusts generated at thelandfill, especially in those areas of the stump dump not covered with vegetation, may be anexposure pathway for stump dump employees and dumpers, as well as users of the park. Thelevel of contamination present in surface soils and the ability of these soils to become entrainedvia atmospheric dispersion has not been evaluated. Therefore, the public health significance of this exposure pathway cannot be assessed.

    2. Soil

Direct exposure to subsurface soils is unlikely. Ingestion and dermal contact with on-site andoff-site surface soils, in addition to the inhalation pathway discussed above, represent probableexposure 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 notbeen performed, while only relatively low levels of contaminants have been detected insubsurface soils both on-site and off-site. However, the possibility remains that isolated hotspots of contaminants exist at the landfill and park that have not been identified. PAHs weredetected in one of three on-site and two of nine off-site subsurface soil samples. The placementof cover material on the landfill in 1981 should reduce the likelihood of exposure to potentiallycontaminated soils. The material used to cover the landfill during park construction reportedlyconsisted of sand and a thin layer of topsoil. No evidence of erosion of this layer was observed atthe park. However, the integrity of this cover has not been assessed.

    3. Groundwater

The groundwater beneath the landfill and extending northwestward towards Peter's Marsh Brookis unfit for human consumption. Although the majority of homes in the area obtain theirdrinking water from a municipal supply, there are at least seven private wells in the area locatedupgradient from the site. These wells are monitored by the NH DES and have been found to befree of contamination. However, contamination of one downgradient well south ofBlackwater 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 beingused as water supplies. Well #3 is being dismantled. Data do not indicate that this well was everat 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.

    4. Surface Water

The Peter's Marsh Brook and associated wetlands are not waters expected to be used fordrinking, swimming, or fishing. The levels of contaminants detected in these waters aregenerally low, although benzene and trichloroethylene were detected at levels close to or inexcess of their respective MCLS. Mercury was detected in one upstream surface water sample at5.3 ug/l. This level is above the MCL (2 ppb) and proposed MCLG (3 ppb). Exposures to thesesurface waters, including leachate seeps, may occur as a result of children wading in thewetlands, although evidence of this exposure has not been observed.

Contaminant concentrations in Salmon Falls River in the vicinity of the drinking water intakesfor Somersworth and Berwick are not expected to reach toxic levels. Therefore, this medium isnot likely to result in human exposure to site contaminants at a level of concern.

    5. Food Chain Contamination

According to the RI report, Peter's Marsh Brook is heavily fished with a large population ofnative 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 forwater and fish ingestion (144 ppt) and fish consumption (146 ppt). Consumption of aquaticorganisms that have bioaccumulated compounds is a potential exposure pathway, thesignificance of which is not known at this time.

Portions of the area surrounding the landfill may be suitable for hunting. However, the extent ofhunting in the area is limited in scope by new residential and commercial properties that areencroaching into the woodlands. Animals that have spent a large proportion of their lifetimes incontaminated areas and that have bioaccumulated contaminants, represent a potential humanexposure pathway. However, unless game animals were to comprise a major proportion of anindividual's daily intake, this exposure pathway is not expected to result in significant chemicalexposure.

    6. Summary

The human exposure pathways of primary public health concern are direct contact, ingestion,and inhalation of potentially contaminated soils; direct contact and incidental ingestion ofcontaminated surface water; ingestion, direct contact, and inhalation of vapors fromcontaminated groundwater; and consumption of potentially contaminated fish.

VI. PUBLIC HEALTH IMPLICATIONS

    A. Exposure to On-Site Contaminants

Disposal activities at the site have led to contamination of on-site soils and groundwater. In theevent that the site is developed, exposure to subsurface soils may be a concern. PAHs weredetected 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, areprobable 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. Groundwaterbeneath the site is unfit for human consumption. Exposure to contaminants in groundwater mayresult 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.

    B. Exposure to Off-Site Contaminants

Contaminants are migrating off-site in groundwater and surface water. The groundwatermigrating northwest of the site is unfit for human consumption. However, there are no knownwithdrawals from this source at this time. The majority of residences in the area are connected toa municipal supply. The residential wells that do exist are located west of the site and have beenfound 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 tocontaminants. Exposure to contaminated groundwater may result in acute and chronic adversehealth effects, including cancer.

Various contaminants of concern have been detected in Peter's Marsh Brook and associatedwetlands, including carcinogens (arsenic, benzene, dichloromethane, tetrachloroethylene andtrichloroethylene) and noncarcinogens (mercury). While these waters are not expected to be usedfor 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 concernwould be an increased risk of developing cancer as a result of repeated exposure. Suchexposures, although possible, are not considered likely due to the location of the wetlands.

VII. CONCLUSIONS AND RECOMMENDATIONS

    A. Conclusions
  1. Based on information reviewed, ATSDR has concluded that the Somersworth Landfill Site isof potential public health concern under current conditions because of the potential risk to humanhealth resulting from possible exposure to hazardous substances at concentrations that may resultin adverse health effects. As noted in Section V C, human exposure to contaminated surfacewater and potentially contaminated surface soils are likely occurring. Exposure to surface wateris likely to occur via direct contact and accidental ingestion, while inhalation, direct contact andaccidental ingestion of surface soils are possible.

  2. The extent of surface soil contamination in Forest Glade Park is unknown. This park is usedon a regular basis and exposure to these soils is likely.

  3. Mercury was present in Peter's Marsh Brook above established criteria for fresh water. Theimpact that this contamination has had on consumable aquatic organisms in Tates Brook andSalmon Falls River is not known at this time.
    B. Recommendations
  1. The level of contamination in surface soils at the landfill and Forest Glade Park should beevaluated.

  2. An assessment should be made on the impact that site contamination has had on consumableaquatic organisms in Peter's Marsh Brook.

  3. Residential wells in the area of the site should continue to be monitored for VOCs on a regular basis.

  4. In accordance with CERCLA as amended, the Somersworth Landfill Site has been evaluatedfor appropriate follow-up with respect to health effects studies. Although there are indicationsthat human exposure to on-site and off-site contaminants may be currently occurring, this site isnot being considered for follow-up health studies at this time because the number of peoplepotentially exposed and the level of exposures are not expected to be sufficient to produce adetectable response in the exposed population.



VIII. PREPARERS OF REPORT
New Hampshire Staff:Jeffrey S. Smith, MSPH
Environmental Health Specialist
NH Division of Public Health
Services

Ellen Cavalier, MPH
Supervisor, Bureau of Health Risk Assessment
NH Division of Public Health Services

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

  1. Mitre Corporation, (1978). Solid Waste Management Alternatives for Dover andSomersworth, New Hampshire: Detailed Report.


  2. Wehran Engineers and Scientists, (May 1988). Draft Remedial Investigation, Somersworth Municipal Landfill, Somersworth, New Hampshire. Volumes 1, 2 & 3.



FIGURES

APPENDIX B
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

APPENDIX C
1. Comment:The Somersworth Sanitary Landfill site is inappropriately categorized in theAddendum as an "indeterminate public health hazard".

Response:The purpose of the Pubic Health Assessment is to assess any current or future healthimpact resulting from the release of hazardous substances into the environment, to develop healthadvisories or other appropriate recommendations, and to identify studies or other actions neededto evaluate and prevent adverse health effects. The product of a public health assessment is thedevelopment of a set of conclusions and recommendations which guide further public healthactions for the site. A critical conclusion for each public health assessment involves identifyingthe level of public health hazard associated with the site.

The indeterminate public health hazard category was created to indicate a level of hazard whenavailable data does not indicate that humans are being or have been exposed to levels ofcontamination that would be expected to cause adverse health effects but data and informationare 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 thePublic Health Assessment categorized the site as an indeterminate public health hazard. Thiscategorization of the site was appropriate given that 1) the available data does not indicate thathumans have been or currently are being exposed to site related contaminants at levels that wouldbe expected to cause adverse health effects, and 2) data are not available for all environmentalmedia 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 riskassociated with this pathway could not be assessed without additional data. The Addendumcontained a recommendation that soil gas sampling be conducted to assess the potentialexplosive hazard risk to buildings surrounding the landfill.

It is important that the public health assessment evaluate all potential pathways of concern giventhat explosive levels of landfill gases have been documented at other landfills that are in similarenvironmental settings and that serious injuries or deaths have been reported as the result oflandfill gas fires and explosions. The conclusion that ATSDR and NH DPHS adopted tocharacterize the level of hazard for the site (indeterminate public health hazard) is thereforeappropriate. The recommendation that soil gas sampling be conducted to evaluate the potentialexplosive hazard of methane and other landfill generated gases is a valid and prudent publichealth 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 SanitaryLandfill site constitutes an indeterminate public health hazard because of this data gap andrecommended that "soil gas sampling be conducted to assess the potential explosive hazard risksto 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 otherexplosive gases, upon which an evaluation of the potential hazard posed by landfill generatedgases can be based. Although it is possible to derive theoretical calculations for methane gasgeneration at the landfill, these calculations are not a substitute for the gathering of empiricalinformation from field and laboratory studies. Explosive levels of soil gases have beendocumented at other landfills in environmental settings similar to the Somersworth SanitaryLandfill site. Serious injuries and deaths from landfill gas fires can occur and have beendocumented in the past. It is because of the potentially serious consequences that can result fromlandfill gas fires and explosions, that actual measurements rather than theoretical calculations beused 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 recommendationthat 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 theAddendum 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 currentlyactive residential wells are at risk to site related contaminants (refer Demographics, Land Useand National Resource Use, paragraph 1). The wells were mentioned relative to a discussion ofexisting water supplies located in the site area. This section of the Addendum reviewsdemographic information and land use at or near the site in order to evaluate the types andfrequency 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 theinformation gathered relative to environmental contamination and the analysis of exposurepathways to develop conclusions about the public health significance of the site and to makerecommendations 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 SanitaryLandfill 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 ofPeter's Marsh Brook and Tates Brook.

Response:Similar to comment #3, the recreational fishing in the pond located north of thelandfill was identified in the Demographic, Land Use and Natural Resource Use section of theAddendum as an example of the type of human activity which could contribute to exposure tosite related contaminants and which would be evaluated in the Addendum. The Addendum doesnot identify the consumption of fish from this pond as a source of risk. The Addendum doesstate that the sediment of Peter Marsh's Brook was sampled by EPA in July, 1992 as part of theyearly site assessment (refer Environmental Contamination and Physical Hazards, B. Off-siteContamination, paragraph 5). The sediment samples were analyzed for VOCs and metals. EPAreported 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 fortrichloroethene (TCE) and vinyl chloride were in excess of the current EPA MaximumContaminant Levels (MCL) for the two compounds. The detection limits for these twocompounds 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 informationpresented in Table 1 of the Addendum is taken from the Remedial Investigation Data GatheringReport 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-sitegroundwater for 1989 and 1990, reveals that the detection limits reported for TCE and vinylchloride exceeds 1 ppb and the MCLs for the respective compounds for some of the samplesrepresented. One example is Sample #5009-10 collected from monitoring well OB-3, sampledNovember 11, 1989 which indicated that no TCE was detected with a detection limit of 25 ppband 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 reviewedand 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 therespective MCLs.

6. Comment:There are various errors contained in the data tables in the Addendum relative tothe reporting of detection limits and contaminant levels found in groundwater samples collectedduring 1989 and 1990. For example, Table 1 of the Addendum indicates that the detection limitsfor 1,2 clichloroethane were 25 and 50 ppb when, in fact, detection limits of 1 and 5 ppb wereused in connection with the samples collected during this time period. In addition, Table 1indicates that all groundwater samples contained detectable concentrations of vinyl chloride,trichloroethene (TCE), tetrachloroethene (PCE), and arsenic when, in every case, there weremeasurements where the contaminants were at non-detectable levels. The Table also indicatesthat methyl ethyl ketone was not analyzed for in the samples when, in fact, it was analyzed forand detected.

Response:As indicated in the response to comment #5, the information presented in the datatables in the Addendum is taken from the Remedial Investigation Data Gathering Report for theSomersworth Landfill (1992). The Data Gathering Report contains a summary of the volatileorganic compound analyses for groundwater for 1989 and 1990. This data indicates that, withrespect to 1,2 dichloroethane, the detection limits were in the range 1-50 ppb for the samplesanalyzed during this period. For example, sample #5032-6 from monitoring well B-8L, whichwas collected in 1989, indicated that 1,2 dichloroethane was not detected with a detection limitof 25 ppb. The Addendum identified the Cancer Risk Evaluation Guide for 1,2dichloroethane(0.38 ppb) as the appropriate comparison value for the evaluation of the risk posedby this chemical. There is a concern that, for samples where the analytical detection limitsexceed 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 detectionlimits were reported for vinyl chloride, TCE, PCE, and arsenic for the groundwater samplescollected during 1989 and 1990. For vinyl chloride, TCE, and arsenic, there are samples wherethe reported detection limits exceed the comparison values specified in Table 1. It is possiblethat there may be concentrations of these chemicals in these samples at levels of public healthconcern 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-GatheringReport indicated that the groundwater samples collected in 1989 and 1990 were analyzed formethyl ethyl ketone. Methyl ethyl ketone was identified in the Data- Gathering Report by itssynonym, 2-butanone. The levels of methyl ethyl ketone found in these samples appear to bebelow the chosen comparison value (Lifetime Health Advisory-200 ppb) for this chemical.

7. Comment:The Addendum originally stated that there were "observed anomalies with respectto contamination and direction of groundwater flow" and that this statement was one of the basesfor concluding that the site is an indeterminate public health hazard. The data collected to dateshows that the contaminated groundwater flows away from the residences and discharges into thewetlands 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 indeterminatepublic health hazard was based on the identification of a data gap for the evaluation of soil gasesas 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 atrisk to contaminated groundwater. The Addendum indicates that these wells are upgradient ofthe site and states that "these residences are not expected to become impacted by thenorthwesterly plume of contamination." (refer to Pathways Analysis, B, Potential ExposurePathways).

8. Comment:Cecile Street is upgradient from the Landfill as are other existing residential wellslocated on Blackwater Road.

Response:A recent discussion with the DES Remedial Project Manager for the SomersworthSanitary Landfill site indicated that the active residential wells located on Cecile Street andBlackwater Road are upgradient from the Landfill. Information as to the location of theresidential well on Cecile Street was not available to ATSDR at the time that the July 7, 1992 site visit was made.


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