Review of 2002 Annual Groundwater Monitoring Report
MESSER STREET MANUFACTURED GAS PLANT SITE
LACONIA, BELKNAP COUNTY, NEW HAMPSHIRE
This health consultation has been prepared to follow up on recommendations listed in the 2000Public Health Assessment for the Messer Street Manufactured Gas Plant (MGP) Site located inLaconia, New Hampshire. The following document was prepared by the New HampshireDepartment of Health and Human Services, Office of Community and Public Health, Bureau ofEnvironmental and Occupational Health (BEOH), through a cooperative agreement with theAgency for Toxic Substances and Disease Registry (ATSDR). This health consultation reviewssampling data that was collected in 2002 from the area of the former Messer StreetManufactured Gas Plant (MGP) site, where coal tar waste was present, for the purpose ofidentifying current public health implications associated with exposure to chemical contaminants on and off the site.
Site Description and History
The Messer Street Manufactured Gas Plant site is located in Laconia, New Hampshire, north ofthe Messer Street Bridge over the Winnipesaukee River (Figure 1). The area surrounding thesite is a combination of commercial and residential properties. From the late 1800's to 1952, thesite was occupied by a manufactured gas plant (MGP). By-products of this coal gasificationprocess included: coal and oil ash, coke, coal tar, creosote, lubricating oils, solvents, ammonia,sulfur, and phenol. The plant ceased gas production operations in 1952 and was dismantled in1981 [NUSC, 1995].
Between 1993 and 1999, the parties who have undertaken responsibility for the site, NortheastUtilities Service Company and EnergyNorth Natural Gas, Inc., conducted several siteinvestigations under state environmental rules and guidelines. In 1999, these parties produced aRemedial Action Plan for the site and began remedial work.
In 2000, BEOH performed a Public Health Assessment of the site. Due to large amounts of coaltar globules that were found in the river sediments, the site was listed as a public health hazard. Under the conditions found at this time, people who swim or wade in the river would be at risk for short-term skin or eye irritation if they were exposed to coal tar in the sediments [ATSDR,2000].
Concern about exposure to coal tar in sediments prompted BEOH to post "No Swimming" signsalong the river in 1995. These signs have been posted every year since. A series of activity userestrictions (AURs) were put on the site to prevent future exposures to contamination insubsurface soils and groundwater [ATSDR, 2000]. There has been extensive remediation in theWinnipesaukee River and Opechee Bay since the 2000 Public Health Assessment, andenvironmental conditions may differ from what was evaluated in 2000.
Several phases of remediation have taken place since September 1999. To prevent seepage ofmobile coal tar from the ground beneath the site into the Winnipesaukee River, a sheetpilewall/collection trench was installed along the edge of the river. Coal tar globules in thesediments of the Winnipesaukee River and Opechee Bay were identified and a vacuum was usedto surgically remove 200 gallons of the substance. Sediments from a three-acre area of both theriver and the bay were either dredged, stabilized, or both. In addition, a large subsurface holdingtank containing coal tar waste, presumably a major source of contamination, was discovered andthe coal tar removed. Groundwater beneath the site was monitored.
In January 2003, the New Hampshire Department of Environmental Services (DES) providedBEOH a copy of the 2002 Groundwater Monitoring Report (GMR) for the Messer Street MGP. BEOH was asked if the current environmental conditions still warrant the placement of "NoSwimming" signs. The purpose of this Health Consultation is to provide an answer to DES byevaluating new data from the GMR to determine if remedial actions are adequately protectingpublic health.
Overview of Sampling Data:
Regarding the public health status of the site, the GMR includes the following:
- Post-remediation human health risk characterization of surface water and fish samples;
- Monitoring of stabilized/dredged areas of the site;
- Observation of the sheetpile wall built along the site; and
- Removal of remaining coal tar observed on the river bottom.
Fish samples were collected from 22 captured fish that anglers were most likely to eat. The fishwere captured on the downstream side of the railroad bridge (Figure 1). Surface water sampleswere collected from three locations: near the Opechee Bay boat launch, near the Messer Streetbridge and near the railroad bridge (Figure 1). These locations are areas where people are mostlikely to come in contact with water and sediment through use of the boat launch, wading andswimming.
In preparing this document, BEOH relied on the information provided by outside sources. Onlydata collected using appropriate sampling and laboratory methods were considered in thisanalysis. Data with demonstrated QA/QC problems were excluded unless they provided uniqueand relevant information. Certified laboratories performed all chemical testing. Measurementsof chemical concentrations were taken directly from laboratory data sheets to avoid transcriptionerrors.
As a follow-up to the 2000 public health assessment, BEOH evaluated new data from the GMRto determine if there was any remaining contamination that would present a public health hazardto nearby residents or users of the Winnipesaukee River and Opechee Bay. BEOH firstcompared the contaminant concentrations to ATSDR's health comparison values (HCVs). AnHCV represents the amount (or concentration) of a chemical contaminant in an environmentalmedium, such as soil, air or water, that is used in a first step in evaluating whether actualexposure may likely result in an adverse health effect. HCVs are screening levels. When theconcentration of a contaminant is below the HCV, it is highly unlikely that any kind of harmfuleffect will result. If a contaminant concentration is greater than the HCV, it doesn't necessarilymean that exposure is going to result in a health problem. It only means that additionalevaluation of the circumstances in which humans may be exposed and the public healthimplications of that exposure are needed.
As a conservative measure, BEOH selected chemicals of concern by evaluating the maximumlevel of each contaminant on the site. If a sample contained a chemical above its respectiveHCV, additional evaluation of that chemical was conducted.
Chemicals of Concern
Coal tar was the primary contaminant found at the site and previously found in the sediments ofthe Winnipesaukee River and Opechee Bay. Coal tar contains primarily polycyclic aromatichydrocarbons (PAHs), as well as some volatile organic compounds (VOCs).
The maximum values of all PAHs and VOCs found in surface water samples from the river canbe seen in Table 1. The maximum level (0.0072 µg/L) of benzo[a]pyrene was above itscomparison value (0.005 µg/L). For all other chemicals tested, both their maximum levels andaverage levels were below their respective comparison value.
Fish tissues were analyzed for PAHs. Eight PAH compounds were detected in the 22 fish thatwere sampled. The maximum and average values of all PAHs found in fish caught near the sitecan be seen in Table 2. While there are no applicable comparison values for fish consumption,BEOH evaluated the public health implications by examining PAH concentrations and how oftenpeople fish near the site.
People who swim or wade near the site could be exposed to free-phase coal tar (i.e., globules of"pure" coal tar) and PAHs in the sediments and surface water. PAHs in surface water could beabsorbed through the skin, and coal tar could get into a person's eyes. Small amounts of waterand sediment may also be incidentally ingested while swimming or wading. Adolescents are themostly likely population to be involved in this type of activity. During the summer months whenschool is out of session, adolescents could swim in the river several times per week.
People could also be exposed to PAHs by consuming caught near the site. Previous reports[ATSDR, 2000] have indicated that people fish in the vicinity of the site.
Public Health Implications of Exposure
Coal Tar in Sediments
From 1999 through 2001, several phases of remediation removed free phase coal tar andcontaminated sediments from the Winnipesaukee River. These steps included the following(H&A, 2001):
- Installation of a sheetpile wall between the Messer St. MGP site and the WinnipesaukeeRiver, to prevent coal tar from seeping into the river water;
- Identification and vacuum removal of 200 gallons of coal tar from the riverbed;
- Dredging of 17,520 tons of sediment from 2.95 acres of riverbed; and
- Placing of 10,737 tons of stabilization material over 2.87 aces of riverbed.
Observations of the sheetpile wall indicated that the flow of groundwater from the MGP site intothe river has been dramatically reduced, as it was designed to do. Therefore, it is unlikely thatmore coal tar is flowing from the groundwater beneath the site into the river.
In 2002, remediated areas of the river and bay were inspected for evidence of free-phase coal tarand scour (scour is the deepening of a river channel by extreme flow events). The GMR reviewsinspections of the formerly contaminated areas of the Winnipesaukee River and Opechee Bay. These inspections were collected in two ways. Remediated areas exposed or in shallow waterwere inspected during dam drawdown in fall 2002. Sediments in deeper areas were inspectedvia diving.
No evidence of scour was found in the stabilized areas of the river botton. During the diveinspections, two small globules of coal tar were observed. The first was found in 12 feet ofwater and was completely removed. The second globule was found in 30 feet of water and hasnot yet been removed. Since this remaining coal tar is at a significant depth, it is unlikely that aperson swimming or wading in the river could be (or could have been) exposed to it.
Free phase coal tar in the Winnipesaukee River and Opechee Bay has been extensivelycharacterized and removed. It is not known how the coal tar originally got into the riversediments (dumping vs. seepage through groundwater). These observations of the sheetpile walland stabilized areas demonstrate that there is very little known freephase coal tar remaining inthe river sediments. The only known area of contamination is beneath thirty feet of water. There is no evidence of new coal tar being discharged into the river.
The basis for designating this area of the river as a public health hazard in the 2000 public healthassessment was based on the existence of free phase (pure) coal tar in the river sediments.Contact with this substance causes mild-to-severe skin irritation and lesions. Eye irritation andconjunctivitis have also been noted after exposures to coal tar [ATSDR, 1995]. The remedialactions that have taken place have effectively removed all known coal tar in the river sediment(the exception to this is at a depth not accessible to swimmers and waders). Therefore, theexposure pathway of contact with free phase coal tar to skin and eyes has been eliminated.
Benzo[a]pyrene in Surface Water
PAHs comprise a group of over 100 different chemicals that are formed during the incompleteburning of coal, oil, gas, garbage, and other organic substances such as tobacco or charbroiledmeat. PAHs are usually found as a mixture containing two or more of these compounds. Because of the complexity of these mixtures, the most toxic compound, benzo[a]pyrene, is usedas the indicator compound. While not all PAHs are considered carcinogenic (e.g., pyrene), theEPA has determined that benzo[a]pyrene, is a probable human carcinogen [ATSDR 1995].
From an environmental perspective, PAHs can usually be found at very low concentrationseverywhere in the environment. Lake and river environments can be contaminated with smallamounts of PAHs from stormwater, oil spills and recreational boat usage (Albers 2002). LakeWinnipesuakee is a popular boating area, and it also has many built-up urban areas along itsshores. Therefore, it is difficult to discern if these contaminants are the result of coal tar,stormwater drainage or boat activity.
The maximum value of benzo[a]pyrene only slightly exceeds the comparison value (Figure 1). It should be noted that the comparison value is for drinking water. A drinking water comparisonvalue assumes that a child drinks at least one liter of water per day; in the case of swimming it isprobable that a child only (accidentally) ingests much smaller amounts. Moreover, the averagevalue is nearly ten-fold lower than the comparison value. The average level of a benzo[a]pyreneis the concentration that swimmers and waders are more likely to be exposed to over the longterm; long term exposure, as opposed to short term exposure, is the concern when evaluatingthese low-level PAH exposures. Therefore, it is possible to conclude that these levels do notpose a public health hazard to people who swim or wade in the water.
PAHs in Fish Tissue
Twenty-two fish samples were collected in 2002. The levels of PAHs in the fish tissue werelower than the levels found in the fish tissues analyzed in 1999 (Haley and Aldrich, 1999); thesamples taken in 1999 were collected prior to the remedial activity that has taken place.
While PAHs can be found in low concentrations in fish tissue, they are not expected toaccumulate because most fish have the capacity to metabolize and excrete these compounds[ATSDR, 1995].
BEOH has a state-wide advisory for the consumption of freshwater fish from New Hampshirewater bodies to protect the public from mercury, a contaminant that is found in fish throughoutthe state. The general population is advised to limit their consumption to four 8-ounce meals permonth. Young children (6 years old or younger) and women of child-bearing age arerecommended to eat only one 8-ounce meal per month.
Recreational fishers typically eat approximately 30 grams of fish that they have caught per day[USEPA, 1995], which is equivalent to the state-wide fish consumption advisory for the generalpopulation (four 8-ounce meals per month). This is likely an overestimate of fish consumptionnear the site given that most anglers fish from different water bodies during the year. Regardless,at this consumption rate, exposures to PAHs in fish near the Messer Street MGP Site would behundreds of times lower than ATSDR Minimum Risk Levels for individual PAHs, and over onemillion times lower than the levels at which developmental effects were seen in animals.Therefore, consumption of fish from near the site would not result in an appreciably increasednon-cancer effect. Moreover, these levels are low enough so that long-term exposure would notresult in an appreciable increased cancer risk.
Children are at a greater risk than adults from certain kinds of exposure to hazardous substancesemitted from waste sites. They are more likely to be exposed for several reasons (e.g., they playoutdoors more often than adults, increasing the likelihood that they will come into contact withchemicals in the environment). Because of their smaller stature, they may breathe dust, soil, andheavy vapors close to the ground. Children are also smaller, resulting in higher doses ofchemical exposure per body weight. The developing body systems of children can sustainpermanent damage if certain toxic exposures occur during critical growth stages. Mostimportantly, children depend completely on adults for risk identification and managementdecisions, housing decisions, and access to medical care.
With specific regard to contaminants in surface water and sediment, children are at higher risk ofexposure because they are more likely to come in contact with surface water and sediment thanadults. This occurs through playing in the water, wading and swimming. This results infrequent contact with surface water, contact with sediments and sediment/water possibly stickingto clothing or exposed skin. Contaminated sediment and water can be spread, resulting inindirect exposures by other children.
Since there is no evidence of coal tar in the sediments of the Winnipisaukee River and OpecheeBay, exposure to free phase coal tar is no longer a pathway of concern. As a result, children whoswim or wade in these areas are unlikely to experience any adverse health effects.
- The Messer Street MGP site represents no apparent public health hazard in the presentand future because there is no known remaining free-phase coal tar in the sediments that areaccessible to those who use the Winnipesaukee River or Opechee Bay. This area represented apublic health hazard to waders and swimmers in the past, due to concerns about coal tar causingskin and eye irritation. Since contamination in the sediments has been thoroughly characterized,sequestered and removed, the exposure pathway to the eyes and skin is eliminated.
- Contact with surface water in Lake Winnipesaukee and Opechee Bay is not expected toresult in exposures to contaminants at levels of health concern. Therefore, contaminants insurface water in these areas pose no apparent public health hazard.
- Eating fish caught near the site (in accordance with the state-wide freshwater fishconsumption advisory) is not expected to result in adverse health effects. The concentrations ofPAHs in the tissues of fish caught near the site are low and, therefore, pose no apparent publichealth hazard.
- Since a large area of the site has been dredged and successfully stabilized, swimming andwading bans are no longer necessary. "No Swimming" signs that were recommended in the2000 Public Health Assessment are no longer necessary.
- Residents and visitors should follow the BEOH state-wide freshwater fish consumptionadvisory. The general population is advised to limit their consumption of freshwater fish fromNew Hampshire water bodies to four 8-ounce meals per month. Young children (6 years old oryounger) and women of child-bearing age are recommended to eat only one 8-ounce meal permonth. BEOH issued this advisory to protect the public from exposures to mercury in fishtissues, which is common throughout the state.
- Residents and visitors should not enter restricted areas of the site while remedial actionsare ongoing.
The purpose of the Public Health Action Plan is to ensure that this Health Consultation not onlyidentifies any current and potential exposure pathways and related health hazards, but alsoprovides a plan of action to mitigate and prevent adverse human health effects resulting fromexposures to hazardous substances in the environment. The first section of the Public HealthAction Plan contains a description of completed and ongoing actions taken to mitigateenvironmental contamination. In the second section there is a list of additional public healthactions that are planned for the future.
(A) Completed or Ongoing Actions
Significant progress has been made by the parties who have assumed responsibility for theremediation of the Messer Street MGP Site and DES towards cleaning up the contamination onthe site. The following is a summary of major accomplishments and works in progress that bearspecifically on public health aspects of the site.
- Starting in 1994, the parties who have assumed responsibility for cleaning up the sitehave completed multiple environmental investigations at the site. In combination, theseassessments provide a comprehensive description of the nature and extent of contamination onthe site.
- In 1995, after reviewing environmental data for sediments near the site, BEOH issued anadvisory against swimming in the section of the river starting at the Messer Street bridge andextending 1,000 feet downstream. Permanent "No Swimming" signs were posted around theaffected area.
- In January 1999, a Remedial Action Plan for the site was developed that, whencompleted, would eliminate the public health hazard on the site. Work on the first phase of theremedial actions began in the fall of 1999.
- In March 1999 BEOH held a public availability session at the Laconia City Hall. At thissession, residents identified their health concerns to state health officials in confidence.
- In July 1999, DHHS distributed a survey to residents in the immediate vicinity of the siteto gather information on their health concerns about the site. Forty two (42) of the 113 surveys(37%) were returned.
- Between September 1999 and January 2000, the first phase of the remediation was nearlycompleted, the objective of which was to stop discharges of mobile coal tar to the river.
- In January 2000, BEOH completed a draft Public Health Assessment for the site anddistributed it for public comment. The public comment period ended on February 18, 2000.
- In February 2000, at the request of DES, BEOH prepared a health consultation on thepublic health impacts of the proposed plan for remediating contaminated sediments in theWinnipesaukee River and Opechee Bay.
- In May 2000, BEOH completed the Public Health Assessment on the Messer Street MGPand the affected off-site areas of the Winnipesaukee River and Opechee Bay.
- Between September 2000 and March 2001, the second phase of remediation wascompleted. This consisted of selected dredging, stabilization and monitoring of contaminatedsediments in the Winnipesaukee River and Opechee Bay.
- In December 2001, DES established a Groundwater Management Zone in areas withgroundwater contaminated by the Messer Street MGP site.
- In November 2002, Haley & Aldrich Inc. completed, on behalf of DES and theresponsible parties, an Annual Groundwater Monitoring Report.
- In January 2003, BEOH advised DES that since only small amounts of coal tar remainedat depths beyond the reach of swimmers, "No Swimming" signs were no longer necessary toprotect public health.
(B) Planned Actions
- BEOH will continue to advise DES on questions of public health regarding the site. Aspart of this, BEOH will review new environmental data collected at the site.
- If conditions on the site change from those evaluated in this public health assessment,BEOH will revisit its conclusions regarding the public health hazards present on the site.
- An additional risk assessment will be performed by a DES contractor in 2003 to confirmthe results of the 2002 risk assessment.
- BEOH will notify the Laconia town health officer of the status of the site. BEOH willalso provide the health officer and concerned residents a FAQ sheet regarding the status of thesite.
Todd C. Hudson
Environmental Health Risk Analyst
Bureau of Environmental and Occupational Health
New Hampshire Department of Health and Human Services
Concord, New Hampshire
(603) 271-3991 (fax)
The Health Consultation on the former Messer Street Manufactured Gas Plant inLaconia, New Hampshire was prepared by the New Hampshire Department of Health andHuman Services under a cooperative agreement with the Agency for Toxic Substancesand Disease Registry (ATSDR). It is in accordance with approved methodology andprocedures existing at the time the Health Consultation was begun.
Gregory V. Ulirsch, M.S.
Technical Project Officer
Superfund Site Assessment Branch (SSAB)
Division of Health Assessment and Consultation (DHAC)
The Division of Health Assessment and Consultation, ATSDR, has reviewed this HealthConsultation and concurs with its findings.
Chief, SPS, SSAB, DHAC, ATSDR
|Chemical||Frequency of Detection||Max. Conc. |
|Mean Conc. |
|Drinking Water Comparison Value |
|Polycyclic Aromatic Hydrocarbons|
|Volatile Organic Compounds|
|Methyl-tert-butyl ether (MTBE)||3/3||1.17||1.17||70||NH GW-1|
1 and 2 - These chemicals have no published comparison value, and surrogate toxicity values were used based on the knowledge of that chemical's mechanism of toxicity. The comparison value for pyrene was used to represent the toxicity of acenaphthylene. The comparison value for naphthalene was selected to represent the toxicity of 2-methylnapthalene.
3 - Risk-Based Concentration
4 - Cancer Risk Evaluation Guide
5 - New Hampshire Drinking Water Comparison Value
|Chemical||Frequency of Detection||Max. Conc. |
|Polycyclic Aromatic Hydrocarbons|
Albers, P. H. 2002. Impacts of Motorized Watercraft on Shallow Estuarine and CoastalMarine Environments. Journal of Coastal Research 37: 143-150.
Northeast Utilities Service Company (NUSC). 1995. Results of the 1994 SiteInvestigation. Manchester, New Hampshire.
Agency for Toxic Substances and Disease Registry (ATSDR). 2000. Public HealthAssessment for the Messer Street Manufactured Gas Plant. Public Health Service,Atlanta, Georgia.
Haley and Aldrich, Inc. 2002. Annual Groundwater Monitoring Report for formerMesser Street Manufactured Gas Plant Site. Manchester, New Hampshire.
Agency for Toxic Substances and Disease Registry (ATSDR). 1995. ToxicologicalProfile for Polycyclic Aromatic Hydrocarbons. Public Health Service, Atlanta, Georgia.
U.S. Environmental Protection Agency (USEPA). 1995. Guidance for AssessingChemical Contaminant Data for Use in Fish Advisories. EPA 823-R-95-007. Office ofWater, Washington, DC.