PUBLIC HEALTH ASSESSMENT
JOSLYN MANUFACTURING AND SUPPLY COMPANY
BROOKLYN CENTER, HENNEPIN COUNTY, MINNESOTA
The Joslyn Manufacturing and Supply Company site is listed by the U.S. Environmental Protection Agency (EPA) on the National Priorities List (NPL). Wood-preserving operations were conducted at the site from the 1920's until 1980. Process wastes containing creosote, pentachlorophenol (PCP), and copper/chromium/arsenic (CCA) were disposed in two on-site waste ponds. In addition, burial of wastes and at least two large spills of wood treating solutions also occurred during the history of site operations.
Groundwater and soil at the site are contaminated with polynuclear aromatic hydrocarbons (PAHs), and with pentachlorophenol (PCP). Polychlorinated dioxins and furans, common contaminants of PCP, have also been detected in soils and groundwater in the area of heaviest PCP contamination.
Remediation of the site began in 1988. Roughly 20,000 tons of contaminated soil were removed and disposed off-site in an EPA-permitted hazardous waste landfill. Nearly all contaminated soil at the site has been excavated and is being treated on-site. A groundwater pump-out system for the on-site surficial aquifer and middle sand unit began operating in 1989. Pump-out of the most contaminated material (a sinking liquid phase) will be delayed because Joslyn recently opted to modify and resubmit its design plans for the pumpout and oil seperation system. Following construction of the extraction well and treatment unit, pumping is likely to begin in late 1994 or 1995. This waste will be shipped off-site for recycle or incineration. It is beyond the scope of this report to describe all the clean-up efforts taken at the site to date.
Individuals working with contaminated soil on the site may be exposed to PAHs and PCP via dermal contact with contaminated soil, or via inhalation or ingestion of contaminated soil or dusts. Persons within a building on-site that houses equipment associated with the pump-out system could inhale contaminants volatilized from extracted groundwater or free product. The Health and Safety Plans for on-site remediation workers have addressed methods for eliminating or minimizing these possible exposures.
Monitoring wells south and east of the site have detected PAHs, PCP, and low levels of polychlorinated isomers of dioxin and furan in groundwater. Some of the detections of PCP and PAHs have exceeded state and federal health-based guidelines for drinking water. All residences within the area of measured groundwater contamination are now connected to a municipal water supply that is not affected by site contamination, so exposure to chemicals in the groundwater is probably only infrequent if remaining private wells are still used. Residents of the area have been informed of the groundwater contamination through public meetings. Some residents continue to use their wells for what they reported to be non-potable purposes.
Persons living and working in the site's immediate vicinity may be exposed to low levels of airborne contaminants from the site. A number of methods are used to control dusts at the site. Air monitoring at the site has not indicated that dust generation or volatilization of site contaminants has been significant. A recently completed risk evaluation study for potential exposure to contaminated dusts did not suggest any health threat to off-site populations.
Based upon currently available information, the Minnesota Department of Health (MDH) concludes that the former Joslyn Manufacturing is classified as an indeterminate health hazard due to: 1) Past and continuing use of contaminated or potentially contaminated groundwater near the site; 2) Data which suggests that air-borne contaminants could pose a health risk to persons on-site if safety precautions are not adhered to; 3) Potential human exposure to contaminants in soil for persons on-site, again primarily involving any workers who might neglect to use adequate personal protection. Any trespassers entering on-site areas where contaminated media are accessible may also place themselves at risk; and 4) Data gaps concerning site contaminants potantially accumulated in organic matter and possibly biota of Twin Lakes.
The indeterminate risk classification is selected indicating "that available data do not indicate that people are being or have been exposed to levels of site contaminants that would be expected to cause adverse health effects, but data or information are not available for all environmental media to which people could be exposed." Much has been done at the Joslyn site to prevent and minimize potential risks to the public and workers, and efforts are planned to continue clean-up efforts in a way that is believed to be protective of the pulic and workers; however, the indeterminate hazard classification is chosen mainly because of questions about potential risks from past exposures which cannot be answered.
The ATSDR Health Activities Recommendation Panel has determined that this site be referred for consideration of a dose reconstruction endeavor. In addition, a community health education effort is needed.
The Minnesota Department of Health will inform users of potentially contaminated groundwater near the site about possible health risks and recommended usage, assess the air pathway for off-site exposure to volatilized contaminants when additional sampling data become available, will review sampling data and plans for any further site investigation or site closure actions when requested by the Minnesota Pollution Control Agency, and keep the local community informed as clean up of the site progresses.
In cooperation with the Agency for Toxic Substances and Disease Registry (ATSDR), the Minnesota Department of Health (MDH) has evaluated the public health significance of this site. MDH has determined whether health effects are possible and has recommended further measures to reduce or prevent possible health effects. ATSDR is a federal agency within the U.S. Department of Health and Human Services and is authorized by the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA) to perform health assessments at hazardous waste sites.
1. Physical Description
The former wood treating facility operated on a 29-acre site in Section 10, T118N, R21W in the southern portion of Brooklyn Center, Hennepin County, Minnesota. The site is north of the cities of Minneapolis and Robbinsdale, and east of Crystal.
The west side of the triangular site borders on the middle lake of the Twin Lakes chain and an adjacent wetland area. Adjacent to the site's south side are residential homes, commercial property, and wooded lots. The northwest to southeast border is adjacent to a Soo Line railroad track, with industrial and residential areas north of the tracks. Small wetlands are also north of the site's border and the Soo Line tracks.
Ryan Lake is located about one-half mile southeast of the site and Ryan Creek flows northeast from the lake to Shingle Creek. Over one mile east of the site, Shingle Creek flows south and east toward the Mississippi River. The Mississippi River is two and one-half miles (13,000 feet) east of the site. Many of the landmarks described in this section are shown in Figures 1 and 2.
The site is relatively flat and covered by sandy soil. Sandy fill was placed over much of the site during the early period of facility construction or operation. As a result, very little topsoil or vegetation is present on the site.
In 1992, the site's surface was clear and unused, except for remediation work. A land treatment unit (LTU) and a large stockpile of soils occupy most of the site's west end. The pile contained roughly 40,000 cubic yards of contaminated soil. The control building (shown in several of the following figures) was the only permanent structure on-site.
The geology under the Joslyn site is complex due to the discontinuous nature of fine-grained deposits which retard or restrict the movement of groundwater and contaminants. A buried bedrock valley under the western portion of the site also complicates the area hydrology.
The site is underlain by an 80 to 140 foot thick sequence of unconsolidated (loosely arranged) sand, peat and sandy fill materials. The uppermost glacial deposit is a stratified fine- to medium-grained sand that ranges from 26 to 50 feet in thickness and is continuous under the site. This sand contains some beds of gravel and becomes progressively finer-grained with depth. The lower portions of the upper sand contains interbeddings of silt and silty clay. Beneath these materials is a layer of low-permeability silt, sand, and clay which ranges from 20 to 60 feet thick. This layer, referred to as the middle confining unit, covers the eastern two-thirds of the site.
An ice block depression (near monitoring well 251) in the upper sand materials holds a zone of groundwater which is contained by a thin sandy clay layer. A buried bedrock valley under the western one-third of the site, is filled with sand and gravel. The valley cuts through the St. Peter and into the Prairie du Chien Group. The middle confining unit is absent in the buried valley.
Beneath the upper sand unit and middle confining unit, is the St. Peter Sandstone. This is the uppermost bedrock formation under the site. The St. Peter is a poorly cemeted, fine- to medium-grained quartzose sand. The St. Peter is estimated to be 75 feet thick east of the site and absent in the buried bedrock valley on the west third. The Prairie du Chien Group lies beneath the St. Peter Formation. The upper (Shakopee dolomite) portion of the Prairie du Chien group contains well-developed horizontal solution channels. Such channels were noted in a log of the Joslyn plant well.
3. Operations and History
The Naugle Pole and Tie Company was the original site owner and operator. Wood treating began at the site in the early 1920s, but little is known about early operations. In the 1940s, the Consolidated Pole Treating Company purchased the property. The Joslyn Manufacturing and Supply Company (now Joslyn Corporation), a partial owner of the latter company, became sole owner of the facility in the early 1960s. Wood treating operations continued under Joslyn's ownership until its closure in September 1980.
Site operations consisted of treating wood products (poles, posts, railroad ties, timbers, etc.) with preservatives. Creosote was used primarily until 1965; Pentachlorophenol (PCP) was also used during the early 1960s. A thermal treating process involved dipping wood products into tanks of heated preservative solution. This process was converted in 1965 to a pressure treatment system. PCP, soluble metal salts (arsenic, copper, and chromium), and to a lesser extent creosote were used in the pressurized process until 1980. Locations of several of the storage tanks, working tanks, pressure cylinders, and thermal treating tanks used at the site are shown in Figure 3.
Portions of the site were used for disposal of liquid and sludge from the wood-treating processes and from the cleaning of storage, reclamation, and treating units. Until roughly the 1950s, boiler blowdown water was disposed in disposal ponds on site. Disposal pond (denoted as pond A) was constructed following the conversion to pressure treatment in 1965 to hold waste water from the pressure treating cylinders. This waste water was routed through a reclamation system and preservatives and oil were skimmed from the water before it entered pond A. Sludge generated by tank and cylinder cleaning from 1976 to 1980 was shipped off-site for disposal. Former employees of the facility indicated that wood treating solutions were spilled around 1960 and again in 1968.
According to a 1982 Minnesota Pollution Control Agency (MPCA) Inspection Report of the Joslyn site, the MDH found oil from the site on the surface of Twin Lakes in the mid-1940's and MPCA asked that inputs to the lake be stopped. Aerial photographs of the site show that in or around 1957, waste-water pond (B) was established on site. The previously existing pond (C) connected to the drainage system was partially filled in.
In 1961, the city of Brooklyn Center found phenols in the groundwater sampled from private wells near the Joslyn site. MDH advised owners of contaminated wells to connect to the municipal water system. In 1974, MPCA's Water Quality Emergency Response Unit began work on the Joslyn site. By 1980, six on-site monitoring wells revealed contamination of the shallow groundwater under the site. In 1980, resampling of many of the residential wells by MPCA confirmed that phenols and PCP were present in groundwater off-site.
In 1983, the site was placed on the National Priorities List (NPL) because of extensive soil and ground-water contamination. In September 1983, the MPCA issued a Request for Response Action to Joslyn requesting an investigation, feasibility study, and remedial actions be undertaken. In May 1985, Joslyn and the MPCA executed a Response Order by Consent. Pursuant to that order, Joslyn hired Barr Engineering to perform a Remedial Investigation and Feasibility Study (RI/FS) for the site.
The RI was completed in 1986. Based upon findings of the RI and a subsequent FS, final groundwater and soil remedies were selected. The remedy included four major components: 1) a groundwater pump-out system; 2) removal and off-site disposal of heavily contaminated soils; 3) on-site land treatment of contaminated soil; and 4) long-term monitoring of groundwater. The selection and a description of the remedy were presented in a Record of Decision (ROD) for the site signed by MPCA in 1989. However, EPA has not concurred with the ROD at this time.
A number of changes have occurred at the site since the detection of groundwater contamination in 1980 -- much of it following the RI/FS. Following closure of the facility, all equipment formerly used for wood-treating operations were removed from the site. In December of 1981, roughly 30,000 gallons of wood treating solution were removed from the site. The following year, approximately 6,500 gallons of sludge were removed to a hazardous waste disposal facility. As an interim response action approved by MPCA, 20,000 cubic yards of highly contaminated soil was removed to a hazardous waste landfill in 1988. A former disposal area (Pond A) was drained, excavated, and backfilled in that same year. It is beyond the scope of this document to describe all remediation activities at the taken at this site; therefore, some conditions may have changed from the time this report was written.
The land treatment unit (LTU) for remediating contaminated soils occupies most of the site's west end. During the treatment season, which runs from early May through September, soil is mechanically tilled on a daily basis. Microbes, water, and nutrients are added to the LTU as needed. Contaminated soil is applied to the LTU in lifts typically 18 inches deep over ten-acre parcels -- this is about 18,000 cubic yards of soil per lift. The first lift was completed in 1990 and the second begun in the Fall of 1990.
Part of the LTU flooded in 1991 delaying soil treament for the second lift. In order to manage surface water in the future, Joslyn constructed a 600,000-gallon water storage/treatment basin in April 1992. This basin is lined with 40-mil high-density polyethylene and is diked. The basin is used for pretreatment (oil-seperation and particulate sedimentation) of water. Water collected in this basin will be treated as necessary, discharged to the sanitary sewer, or reapplied to the LTU.
Nearly all contaminated soil at the site has been excavated. Figure 4 shows locations of soil excavated from 1988 to the present. Because heavy rains in 1991 interfered with planned excavations and land-treatment, a portion of contaminated soil (estimated 4,000 - 8,000 cubic yards) near the LTU and stockpile remains to be excavated. This excavation was completed in 1992. Soil to be treated is stockpiled near the LTU on a 40-mil high density polyethylene (HDPE) liner and covered (12-mil HDPE) until application to the LTU. The LTU is shown in Figure 5.
To prevent future movement of contaminants in groundwater below the site, a long-term pump-out system was installed in 1988 and began operation in early 1989. This system includes seven pump-out wells for the shallow groundwater, two pump-out wells for the middle sand units, and a two-well enhancement system for a deep oily (refined oil and creosote) deposit detected about 80 feet below the former process area: This is termed the DNAPL, for Dense Non-Agueous Phase Liquid. Operation of the DNAPL extraction well will be delayed because Joslyn recently opted to modify and resubmit its design plans for the pumpout and oil seperation system. Following construction of the extraction well and treatment unit, pumping is likely to begin in late 1994 or 1995.
The capture zone for pumpout of shallow groundwater approximates the southeastern site boundary. Pumped water is pretreated on-site to separate oil and discharged (under permit with the Metropolitan Waste Control Comission) to the sanitary sewer system.
The MDH conducted a preliminary Health Assessment for the Joslyn site in April through July, 1988 (MDH 1988). MDH updated the 1988 document to a full Health Assessment in 1990 (MDH 1990). The current Public Health Assessment has been performed to reflect findings of additional investigations and update site conditions.
On April 7, 1988 and February 23, 1989, MDH staff visited the Joslyn site as part of the 1988 and 1990 health assessments for the site. At the time of the February 1989 site visit, the fence was in good condition, except for a few areas where the barbed wire had been bent back or removed. The site was clear of debris. Blowing dust was observed from traffic on the site's roadway.
On May 12, 1992, MDH and MPCA staff revisited the site. Staff walked the site and photographed items of interest. Off-site areas were also inspected. No environmental samples were collected. On May 22, MDH staff returned to inspect the outer edges of the site and to examine off-site areas once more. The following observations were recorded from the 1992 visits:
Odors were noticed on-site and to the east and south (May 12). Odors were fairly strong outside an apartment building located next to the site's southern border near the middle of the site. During the second visit (5/22) the wind was from the south and PCP odors were perceptable to the north of the site.
A person was seen running along the dirt trail parallel to the site's northern border (on railroad right-of-way) outside the site perimeter fence on May 22, 1992.
There were signs of wildlife in the area; including ducks and geese in the wetlands to the west, pheasants, rabbits and turtles off-site, and deer tracks on the berm around the LTU.
A few of the construction contractor's staff were working in the LTU on May 12, in Level-C protective clothing. Three other personnel were also on-site in Level-D clothing (ordinary work clothes) during the site visit. On May 22, the site was locked and no workers were present.
The site was fairly flat and open. The control building near the site's center was the only building remaining on-site. Trailers for site workers (decontamination, site operations, support, etc.) were located south of the control building.
The stockpiled soils in the western end of the site were entirely covered with a plastic sheet that is weighted and tied down.
Large berms (roughly 8 foot height) had been constructed around the LTU which occupies most of the western end of the site. The berms had recently been seeded. Oily water was standing on the surface in portions of the LTU.
Surface water was controlled in the LTU area by newly modified earthen dikes. Water from the LTU was collected and treated in a large basin constructed in 1992.
Water falling outside the treatment and remaining excavation area is directed outside the LTU and off site to the west. Hay bales were placed along the western fence line to prevent erosion of the LTU dikes and runoff.
A chainlink fence surrounds the entire site. Gates were chained and locked. A few breaches caused by vandalism to the fence were noted.
Lawn sprinklers and hoses were positioned along the driveway to the control building for dust control.
According to data from the 1990 Census, the population of Brooklyn Center was 28,887 in 1990. The population is predominantly white (91 percent). About seven percent of the total population for Brooklyn Center is under the age of five years, 24 percent under the age of 18 years. Demographics for the population in the immediate vicinity of the site are not available. Roughly another 40,000 people live in the nearby communities of Robbinsdale and Crystal.
The Joslyn site is located in a fairly populated suburban area. There is a home within a few hundred feet north of the site's west end and others just south of the site boundary at the west end. Lots immediately south of the site's west end are for sale. North of the site's east end, beyond a large commercial building, is a development of new homes (Twin View Meadows Development). Some of the homes were still under contruction during the May 1992 site visit.
In 1985, Barr conducted a well search downgradient of the Joslyn site. A total of 155 of the 160 property owners in the well search area were contacted. Forty-four functioning wells were identified by homeowners. At that time, six homes in the area used private wells as potable supplies and these were connected to the municipal water supply in 1988. Thirty-eight other wells were reportedly used regularly outdoors, but not for drinking water. The areas bordering the well search area are also residential areas, with most residences using the municipal water supply. However, some residences beyond the area of low level groundwater contamination (in the area bordering the well search area) may still use private wells for potable water.
Following closure of the wood treating facility, the site was leased to another company. The site was used for storage and distribution of lumber products. A railroad company also leased the site property during the mid- to late 1980s. Currently only remediation personnel use the site. Aside from the few problems noted during recent site visits, the fence around the site restricts public access to the property and to the contaminated soils in the site's west end.
Light industry and residential areas exist near the Joslyn site. Land around the east end of the site is used for commercial and industrial purposes. One building on the site's south border stores water supply equipment in the lot next to the site's fence.
There is much evidence of refuse disposal in areas near the site. In the wetlands on the site's west side, concrete and treated lumber are piled in the woods and wetland. Trash has been dumped along the Soo line railroad. Property just north of the site's east end is used for disposal of demolition debris. In the wooded areas south and north of the site's west end there are other debris, trash, and discarded treated wood products (poles).
An open area and wetland is west of the site. Joslyn owns this land and there is evidence of past refuse (concrete, poles, debris, scrap metal) disposal on the land and into the wetland. This area is used by the public as evidenced by plastic cups and well-worn paths. MPCA staff have seen adults playing splatball in this area on a few occasions. One path runs along the outside of the western fence line. The area surrounding the western end of the site (southwest, west, and northwest) is partially wooded and has well worn paths. Near the lakes, west of the site, people ride dirt bikes.
Several surface-water bodies are located in the vicinity of the site. The southern lake of Twin Lakes and a small wetland area are on the western border of the site. Another small wetland is located just north of the site. Ryan Lake, Ryan Creek, Shingle Creek, and the Mississippi River are all within 2.5 miles east of the site. Twin Lakes, which border the Joslyn site on the west, are used for recreational purposes such as boating, swimming, and fishing. During the May 1992 site visit, people fishing on the lake, numerous boats and docks on the shore, a broken tire swing on the bank just northwest of the site, and people riding jet skis were noted.
There are biking and walking paths along Shingle Creek which winds through residential neighborhoods east of the Joslyn site. The outfall for the Highway 100 drain tile system empties into ponds that are located in a city park and golf course roughly one-mile (or more) east-northeast of the site. These ponds eventually empty into the creek. Highway 100 is surrounded by city streets and large commercial parking lots.
Groundwater in the upper aquifer moves from the west to east -- from Twin Lakes to the Mississippi River. The bedrock aquifers between the site and the Mississippi River are thought to be used only for industrial and residential nonpotable purposes. The St. Peter and Prairie du Chien-Jordan (deeper) aquifers also discharge to the Mississippi River. The Prairie du Chien-Jordan bedrock aquifers are important sources of drinking water for the Twin Cities metropolitan area. The municipal well nearest to the site draws from the Jordan and is about 1 mile to the northeast of the site.
Potential future uses of the site and surrounding areas include plans for a city park after cleanup is complete. A network of public recreation trails (Twin Lake Trailway) has been proposed to circle much of the Twin Lakes area, including the Joslyn property west of the fenced-in site.
Only a limited number of health outcome data are routinely collected for Minnesota populations. These include data from Certificates of Live Birth, Certificates of Fetal Death, and Death Certificates.
In the past a small number of residents living near the site's south border have reportedly contacted the MPCA and possibly the site's owner about odors in air. These complaints and the nature of any concerns, if there were any expressed, are not documented or documentation is not available.
The community surrounding the site has been informed about the groundwater contamination through MPCA releases and public meetings. The community seems content to be able to continue using free water from their wells, despite the issue of groundwater contamination in the area. According to MPCA staff, attendance at public meetings regarding the site has typically been low.
The goal of this section in the public health assessment is to identify contaminants of concern for further evaluation. For completeness, comprehensive lists of the chemicals found at the site (by medium) are included in Tables 1 through 5 found in Appendix A. These lists will be referred to where appropriate. Chemicals included in this section will be assessed in subsequent parts of this public health assessment. It is important to note that their inclusion below does not necessarily imply that a threat to human health exists. This section focuses on those chemicals found or detected on or off site which are selected as contaminants of concern based on the following considerations:
1) ATSDR has developed environmental media evaluation guides (EMEGs) and cancer risk evaluation guides (CREGs) to assist in selecting chemical concentrations for further evaluation in public health assessments. EMEGs are media-specific (for example, air, water and soil) screening values that are used to select chemicals which produce noncarcinogenic toxic effects (Orloff 1992). EMEGs are derived from estimates of daily doses of a chemical that humans may take in, over a specified period of time, that are unlikely to produce adverse health effects. The environmental concentration of each chemical is compared to the appropriate EMEG value. If the environmental concentration of the contaminant is greater than the EMEG, the contaminant is evaluated further for its potential health impact. If the environmental concentration is less than the EMEG, exposure to the contaminant in that medium (air, soil, or water) is unlikely to pose a health hazard. CREGs are media-specific screening values that are used to select chemicals which produce carcinogenic effects. Media-specific CREG values are defined as the estimated contaminant concentration that will result in one excess cancer in a million persons exposed continuously over lifetime. CREGS are used in exactly the same way as are EMEGs. EMEGs and CREGs for site contaminants are listed in Appendix B.
2) Chemicals found in groundwater are considered to be chemicals of concern and are included in this evaluation if they exceed health-based Recommended Allowable Limits (RALs) developed by MDH for contaminants in private drinking water supplies. RALs have been derived for those chemicals which are most frequently found in Minnesota's groundwater. RALs for non-carcinogens are often taken from the Drinking Water Health Advisories published by the EPA Office of Drinking Water. RALs for carcinogens are derived from the potency slopes (estimates of cancer causing ability) from the EPA Carcinogen Assessment Group and reflect an estimated lifetime excess cancer risk of 1 in 100,000. Although the RALs used in Minnesota are currently applied as health-based guidelines, Health Risk Limits (HRLs) being developed by MDH by the same methods used for calculating the RALs will soon be adopted as rules and will thus be enforceable.
Chemicals found in surface water are considered to be chemicals of concern and included in this evaluation if they exceed Surface Water Quality Standards developed by MPCA (Minnesota Rules chapter 7050). The Minnesota Surface Water Standards are numerical standards having a human-health based component. These standards are based on 1) toxicity to aquatic organisms; 2) toxicity to humans through fish consumption, drinking, or incidental ingestion during swimming; and 3) toxicity to wildlife that consume aquatic organisms. The standards for carcinogenic chemicals reflect a 1 in 100,000 estimated excess lifetime risk of cancer.
Chemicals detected in other media are included as chemicals of concern for further evaluation if they exceed media specific concentrations calculated using ATSDR-derived MRLs, EPA-derived RfDs, and other appropriate risk assessment methods and assumptions. The concentrations for carcinogens reflect a lifetime excess risk of cancer estimated to be 1 in 100,000.
3) Chemicals which do not exceed the values for selecting contaminants of concern may also present a potential health hazard. These may also be included as chemicals of concern based on professional judgement. There may be a concern when there are low levels of many chemicals because of the unknown consequences of exposure to mixtures. Professional judgement may also inidcate a concern exists when exposure may be ocurring through more than one route (including background), or when there are extenuating circumstances related to known or suspected exposures. Examples of such circumstances include subsistence fishing or pica (an uncommon and unusual propensity for eating non-food items) behavior.
4) Furthermore, chemicals may also be included as contaminants of concern based upon site-specific information and low confidence in the adequacy and the (spatial and temporal) representativeness of sampling data. For example, releases and the movement of chemicals from hazardous waste sites may be unpredictable. Chemicals are often released in pulses and monitoring results may reflect peak concentrations found during pulses or they may reflect lower concentrations between pulses. Therefore, chemicals not found or those detected at low concentrations may be detected at much higher concentrations in future sampling events. Additional uncertainty may be the result of the geological variability which is typical of Minnesota glacial formations and the imprecise nature of hydrogeologic characterization.
5) Consideration is also given to field data quality, laboratory data quality, and the sampling design. Community concerns about particular chemicals or health effects are also considered in selecting contaminants of concern.
The primary contaminants of concern at the site are polynuclear aromatic hydrocarbons (PAHs) and pentachlorophenol (PCP). Several PAHs at the site are classified as probable or possible human carcinogens (cPAHs) by EPA (1975); other PAHs are considered to be noncarcinogenic (nPAHs). Soluble metal salts of copper, chromium, and arsenic, used as wood-treating chemicals in later years of operation, are also of potential concern. Chlorinated dibenzo-p-dioxins and dibenzofurans, which are often found as impurities in commercial-grade PCP are also of concern. These compounds have been detected in groundwater or on-site soil.
The compounds routinely tested for during the RI and subsequent investigations and monitoring were 33 polynuclear aromatic hydrocarbons (PAHs - see Appendix A, Table 1), and 14 phenolic compounds, including PCP. Analyses for chlorinated dibenzo-p-dioxins and chlorinated dibenzofurans content were conducted in five shallow groundwater samples taken in 1990, a soil sample from former Pond A, a soil sample composited from contaminated on-site areas, and land treament unit soil samples collected in 1992.
a. Past soil conditions
Investigations of on-site soil found a number of areas of contamination. Most contaminated material was located near the former process (treatment operations) area and below the waste disposal ponds.
During the RI, exploratory excavations and soil borings were placed on-site to investigate the extent of soil contamination. The excavations ranged up to 10 feet deep and the two borings were 16 feet deep. The presence of a visible oil sheen when water was added to soil samples from the excavations, observations of discoloration and odor of soils, and analytical data were used to determine areas of soil contamination. The largest volumes of contaminated soil were found in the former process area and under and around waste disposal Pond A.
During the RI, 11 soil samples from excavations and borings were analyzed for PAHs and PCP. Of these, seven of the samples were taken from areas of soil contamination that were not removed in the 1988 excavation; these were removed in later excavation work. Also, a soil sample composited from former Pond B and soil contamination Areas 4-6 (at depths of 2 to 5 feet) was analyzed for PAHs, PCP, dioxins, and furans. See Table 2 (Appendix A) for maximum contaminant concentrations detected in on-site soils from 1984 to 1988. These results are given as indicative of contaminant levels in soils that were found on site during site investigation. These results are not intended to represent current levels of contaminants in site soil, because nearly all contaminated soils have been excavated, are covered, and have been, or will be, treated to reduce the levels of PCP and PAHs. These soils will also be covered when bioremediation is completed.
A few Pond A soil samples were analyzed for arsenic and chromium in 1981. Sampled on-site soils were found to contain only low levels of heavy metals (not above background), which would not inhibit bioremediation.
At least 10 shallow soil borings and 30 deep soil borings (depths ranging from 26 to 137 feet) were placed following the RI to further evaluate the extent of soil contamination and the stratigraphy beneath the site. These investigations gave evidence that all areas of significant on-site soil contamination had been identified.
From September to November 1988, 20,000 cubic yards of contaminated soil were excavated from the site and transported to an EPA-permitted, triple-lined landfill. Under the response action plan approved by MPCA, biological land treatment of remaining contaminated soil within 3 feet of the surface is being conducted on-site. Contaminated soil underneath the pond A location was excavated and treated in the first lift of the land treatment operations.
b. Present soil conditions
Contaminated soils at depth are still in place in only a few areas. Soils near the city water main (south side of the site) were not excavated because the levels of contaminants were below treatment goals. Greater than two feet of clean soil was replaced over these soils. Other contaminated soil still in place at the site is located near a drainline which terminated near the site's northern border, near the control building, near a treatment pond and decontamination pad, and in the vicinity of wells W255 and 253.
In 1989, a drain line and pipeline were discovered on the site's northern side. Both structures were removed along with contaminated on-site soil up to the site's fence. The drain line ended on the site property, but the pipeline's end has not been located. Residue sampled from the pipeline revealed PCP levels ranging from 1,400 to 3,000 milligrams per kilogram (mg/kg). Three borings were placed on the site's northern border (outside the fence) to two feet below the water table in the area of the drainline. Discoloration, oily sheen, and strong chemical odors were noted in boring logs from two borings at depths below 6.5 and 9.5 feet. Composite samples from these two borings both showed contamination; up to (maximum) 450 mg/kg cPAHs, 1,900 mg/kg nPAHs, and 110 mg/kg PCP were detected in the composite samples.
Visibly contaminated soil east of the control building was detected from a depth of seven feet to at least 21 feet (the end of the boring). A composite sample from this boring yielded 610 mg/kg cPAHs, 22,000 mg/kg nPAHs, and PCP not detected above a 370 mg/kg (detection limit). Contaminated soil east of the control building was excavated in 1992. On the west side of the control building, contaminated soil was also noted during excavation approaching the building's foundation. This was located below a depth of roughly eight feet. The level of contaminants present in this area have yet to be submitted for evaluation. Results of sampling on-site soils that remain in place are presented in Table 3 (Appendix A).
Approximately 40,000 to 70,000 cubic yards of contaminated soil have been excavated and stockpiled on-site or placed in the land treatment area. Only a small portion of contaminated soil near the LTU remains to be excavated in 1992 (see Figure 5). These were mentioned above as soils near wells W253 and W255. Eventually, all the excavated soil will be treated.
Thirty-one wells are currently in place at the site and several are used for monitoring groundwater quality and/or groundwater extraction. Wells labelled with a U (e.g. U1, U2, U3...) are screened in the shallow aquifer and are used for removing contaminated groundwater. Monitoring well W131 was recently installed to monitor shallow groundwater just downgradient of the LTU. Figure 6 shows the on-site monitoring and pump-out wells.
Of the original monitoring wells, 11 were (some have been abandoned) screened at the surface of the upper aquifer (11 to 27 feet), four are screened at mid-depth in the upper aquifer (wells at 35 to 82 feet), five are screened in discontinuous middle sand units (wells at 80 to 85 feet), and three are screened in sand units and the St. Peter bedrock unit of the deep aquifer (wells at 132-138 feet).
During monitoring between 1984 and 1986, filtered groundwater samples contained concentrations of arsenic ranging from <1 to 11 µg/L, chromium ranging from <0.5 to 5.5 µg/L, and copper ranging from <0.5 to 7 µg/L. These metal levels were lower than federal and then-existing state drinking water advisory levels (the RAL for arsenic has since been lowered substantially), and monitoring for these metals was subsequently discontinued (MDH 1990). In 1990, the MPCA sampled four on-site monitoring wells (filtered samples) for elemental mercury and found less than 0.1 µg/L (Barr 1991 addendum).
A floating oil layer (low-density non-aqueous phase liquide - LNAPL) has been detected on the surface of shallow groundwater in monitoring wells in the former process area. Oil mixed with water was found at depths of 10 to 20 feet below the ground surface in monitoring well W113. PAHs, PCP, chlorinated dibenzofurans, and dibenzo-p-dioxins have been detected in this oil; tetrachlorodibenzo-p-dioxin (TCDD) or tetrachlorodibenzofuran (TCDF) were not found. Table 4 (Appendix A) lists these findings.
A dense non-aqueous phase liquid (DNAPL) was found below the former process area, above a confining layer. The DNAPL is thought to be isolated in a clay-lined depression, at the bottom of the surficial aquifer. Samples of the DNAPL obtained from W251 (at 82 feet) have contained cPAHs, nPAHs, and PCP. Isomers of hexa- and hepta-chlorinated dibenzofurans and hexa- and hepta-chlorinated dibenzo-p-dioxins were also detected in a sample from well W251. TCDD and TCDF were not detected.
The heaviest groundwater contamination under the site has been detected in the shallow aquifer and middle sand wells near the former process area. Many of the on-site monitoring or pumping wells have shown PAHs and PCP levels exceeding state and federal health-based screening values (for example, RALs and EMEGs) for these compounds from 1984 until 1991. In the most contaminated shallow monitoring wells, the levels of PCP have generally decreased significantly in recent years. On the other hand, the levels of cPAHs detected in middle sand and lower aquifer wells have recently increased in W252, W254, W300SP, and W307.
Maximum concentrations of cPAHs, nPAHs (as categorized in site reports), and PCP detected in the surficial aquifer and lower aquifer on-site between December 1984 and October 1991 are also shown in Table 4 (Appendix A). High levels of PAHs (20 - 1,300 µg/L) and PCP (<5 - 50,000 µg/L) have been detected, 1988 through 1991, from the pump-out system's wells U1 - U8. High levels of PAHs and PCP have also been detected in shallow aquifer samples takennear the site's south central, southeast, and north central borders. The PAH detection limits in recent samples near the site's edges from W6, W10, and W112 were too high to detect low level contamination in the range of the RALs for total nPAHs and total cPAHs.
In August 1990, shallow groundwater from four off-site monitoring wells and monitoring/pumping well U2 on the site's southern border was sampled as part of a risk assessment "for continued use" of contaminated groundwater downgradient of the site (Barr 1990b). The sample from well U2 was tested for chlorinated dibenzodioxins and chlorinated dibenzofurans; tetra- and octachlorinated dibenzofurans, and tetra-, hepta-, and octachlorinated dibenzo-p-dioxins were found. These findings are also included in Table 4 (Appendix A). Specific isomers 2,3,7,8-TCDF and 2,3,7,8-TCDD were measured in the single sample at 0.0012 and 0.0033 nanograms per liter (ng/L) respectively. The distribution of groundwater contaminants is discussed further in a later section of this report.
3. Surface Water
There are no natural surface-water bodies on-site. Water in a former disposal pond was found to contain high concentrations of cPAH, nPAH, PCP, arsenic, and copper during the RI. In a permitted action in 1988, all this water in the pond was treated and pumped to the sanitary sewer, and the contaminated soil beneath the pond was removed and the area was backfilled. The LTU encompasses the area formerly occupied by this pond.
Runoff from the site is expected to be minimal due to the the relatively flat topography of the site, berm barriers, and the absorptive, sandy site soil. Precipitation that collects in the LTU is contained within its dikes. Drainage from the outer surfaces of the LTU dikes or compacted surrounding areas is directed away from the treatment area and flows off-site to the west.
Excavation water has been treated in two settling ponds previously on the site's south side. This water was tested to ensure compliance with discharge permits before sewering. Water from the large surface water control basin is also discharged under permit.
Results reported for air monitoring at the site, which is described below, are listed in Table 6 (Appendix A).
The original bioremediation contractor for the site monitored air quality during treatment of the first lift of contaminated soil (4/90 - 7/90) and during the excavation and placement of the second lift (8/90 - 9/90). Dust was monitored at the site perimeter using an optical scattering device. 24-hour ambient air samples were collected from 4/90 - 7/90 using a high-volume airflow filter sampler. Worker exposure was measured with personnel sampling low-volume airflow filter samplers.
Real-time dust samples collected at the site perimeter during treatment of Lift 1 soils ranged from nondetected to 0.79 milligram per cubic meter (mg/m3). A maximum of 40 mg/m3 total dust was measured in eight full-shift worker personnel samples; however, seven of the samples were near or below 1 mg/m3. Ambient air sampling measured total suspended particulates (TSP) less than 1 mg/m3 near the center of the site's west end and near the south central portion of the site (Barr 1990a). Results from full-shift personnel sampling and high-volume particulate monitoring on a berm near the middle of the LTU during treatment of Lift 2 soil were also very low (Barr 1992b).
From the middle of July through October 1991, during construction and excavation work, Barr Engineering sampled ambient air at the site for total suspended particulates. A total of 19 samples were collected using a high-volume filtration sampler located near well W206 on the site's south side. Total dust, rather than that having diameter of 10 micrometers or less (PM10) was measured. Results showed a maximum of 141 µg/m3 (24-hour concentration) and an average of 58.3 µg/m3 for total dust (Barr 1992b). The national primary and secondary ambient air quality standards for particulate matter (PM10) are 150 µg/m3 as a maximum 24-hour concentration and 50 µg/m3 as a maximum annual average for PM10 (40 CFR Part 50.6). The maximum result for TSP is listed in Table 6 (Appendix A).
During soil treatment in 1990, personal sampling film badges placed in three locations around the LTU and were worn by selected site personnel; no hydrocarbons were detected. At three locations around the LTU, daily measurements for organic vapors were also taken with a photoionization detector. The same monitoring was conducted for total hydrocarbons in 1991: Four eight-hour samples were collected weekly.
In July 1991, Barr Engineering monitored air quality near an excavation point, near a soil handling (screening) area, and inside the control building office. Samples from near the screening area and the excavation were taken for coal tar pitch volatiles (CTPVs) and PCP. Office samples were taken for PCP. Samples from the excavation area were also for naphthalene, phenol, BTX compounds (benzene, ethyl benzene, toluene, and xylenes), and total dust. All of the sample results were below OSHA standards. Personnel sampling was also performed for naphthalene, PCP, and phenol.
In August 1991, an air sample taken at the edge of excavation work one foot above the ground exceeded the OSHA permissible exposure limit (PEL) for PCP. This sample was collected at the edge of an area under excavation. Black oily product reportedly surfaced in the excavated area. PCP was measured at 2.6 mg/m3, above the occupational standard of 0.5 mg/m3 (Barr 1992b).
During October 1991, air was sampled for phenol and naphthalene in the control building's tank effluent room. Neither compound was detected.
5. Other (Toxic Chemical Release Inventory)
To determine if other facilities in the area could potentially contribute to contamination of the environment near the site, MDH reviewed the most recent Toxic Chemical Release Inventory (TRI 1989). TRI is developed by EPA using industry reports of chemical releases. These reports are mandatory for releases of specific amounts of hazardous substances -- as established by EPA.
Only one facility reporting to TRI was found near the site. This operation, the CON-AGRA Fertilizer Plant reported releases of 255 pounds of ammonia and sulfuric acid to the atmosphere in 1990. The reports also showed that these two compounds were also disposed to the sanitary sewer.
In 1980, there was a fire at a fertilizer warehouse owned by Howe Inc., located greater than 2,500 feet east of the Joslyn site. The groundwater under the Howe facility and extending to the east was found to be contaminated with up to ten identifiable commercial herbicides (for example, Atrazine, Lasso, Bladex, etc.). MDH conducted a search of private wells surrounding this facility following the fire. The westward limit of this well search is the eastward limit of the area searched by Barr for the Joslyn investigation. After one year of pumping groundwater under the Howe facility, monitoring results showed that the plume of contaminated groundwater due to the fire had moved beyond the monitored area. The Howe site has been turned over to the Minnesota Department of Agriculture who is in early stages of deciding what, if anything, may need to be done.
Other non-industrial uses of the surrounding area may potentially affect the quality of the local environment. Examples of these include the motorized traffic in areas surrounding the Highway 100 drain tile and catchment areas of the local storm water sewer system, and boat traffic on Twin Lakes. Sampling results discussed in this Public Health Assessment report suggest that both these were likely sources of PAHs in surface water sampled as part of investigations related to the Joslyn site.
Soil and sediments contaminated with what was believed to be hydraulic oil (termed the non-conforming soil) were found beyond the site's fence on the west of the site's property. These contaminated materials were excavated from a wetland fringe area west of monitoring wells W101, W201, and W301 (recall Figure 4). These were excavated and placed in the LTU. It is unknown if sampling was performed in the excavated area to verify that all contaminated material was removed.
Investigation of the drain line and pipeline encountered on the site's northern side suggests that these structures may have contaminated off-site areas. The drain line terminated on the site property and was removed. Contaminated soil associated with the drain line was estimated to extend to the north (roughly ten feet beyond the site's border). The railroad has not allowed investigation to proceed onto its property. The pipeline, which held residue found to contain up to 3,000 mg/kg PCP, ran roughly north/south just beyond the east edge of the LTU. Radio wave tracing in 1991 showed that the pipeline turns to the west and roughly follows the edge of the site property. However, the end of the pipeline was not found. Figure 7 shows the locations of the drain line and the pipeline at the site's northern edge.
Six borings were placed south of the site, just beyond the property boundary, in June 1989 to check for contamination in that area. No visibly contaminated soils were detected in the borings from the north or the southern areas explored. A sample from one boring south of the site was found to have a very small amount (0.3 mg/kg) of PCP in the subsurface soil.
In 1961, the city of Brooklyn Center found private residential wells near the Joslyn site were contaminated with phenols. Additional testing in 1980 by the MPCA, found phenols and PCP in residential wells off-site (MDH 1990).
The groundwater investigation found contamination extending from the site to the east; in the direction of groundwater movement. The following information characterizing the hydrogeology in the region of the Joslyn site will help to explain the movement of site contaminants in groundwater:
The unconsolidated materials that make up the surficial aquifer in the region surrounding the site are approximately 100 feet thick, and overlie the St. Peter Sandstone and Prairie du Chien-Jordan bedrock aquifers. These unconsolidated materials consist of outwash sand, peat, and sandy fill. A unit of lower permeability confines most of the lower aquifer on the eastern two-thirds of the site. The DNAPL located beneath the former process area is believed to be confined to an ice-block depression in the upper aquifer by a thin sandy clay unit. Discontinuous middle sand units are partially located beneath this depression. The direction of ground-water flow in the surficial and lower aquifers is east-southeast from the site, toward the Mississippi River 2.5 miles (13,000 feet) to the east. The velocity of ground-water flow in the upper aquifer is estimated to range from 250 to 1,000 feet per year.
A buried bedrock valley exists beneath the western third of the site, where the sands that comprise the upper and lower aquifers are continuous and not separated by the low permeability units. Therefore, contaminants in the surficial aquifer on the western third of the site may have moved to the lower aquifer more quickly or more readily than those in the surficial aquifer on the eastern two-thirds of the site. There seems to be a southern component to ground-water flow on the west side of the site, as evidenced by contaminants present in monitoring wells W127-W129 and W328.There are ten shallow, one mid-depth, and two deep monitoring wells installed south, southeast, and east of the site. One of these wells, W130, was recently installed northeast of the site and was first sampled in 1990. Figure 8 shows the locations of the off-site monitoring wells.
Monitoring results from 1985 to 1989 showed elevated levels of PAHs (primarily non-carcinogenic PAHs) were regularly found in monitoring wells W122, W123, 125, W223, and W323. PCP was also found in upper aquifer wells south and southeast of the site and in the mid-depth upper aquifer well W223 between 1985 and 1989. Maximum contaminant concentrations detected in these wells are given in Table 5 (Appendix A).
Modified plots of the plumes extending off-site to the east are presented in Figures 9, 10, 11, and 12. These isoconcentration plots show that high levels of groundwater contaminants extended as far to the east as monitoring well W125 in 1988 and 1989. The plots do not show results form 1986 when higher levels of nPAHs and PCP were found in W127 and W129. Figure 14 shows maximum concentrations measured in shallow aquifer wells between 1984 and 1992; results from three shallow wells (installed in 1979 for an investigation of the contamination from the Howe Chemical facility) sampled once in May 1985 are included. These additional wells are labelled P03, P02, and P23 in Figure 13. Monitoring results from the 1985 sampling showed non-detectable or only very low levels of PAHs and PCP in the shallow aquifer east of the monitoring points for the Joslyn site. There is no data on deep aquifer conditions in this eastward area, nor information on water quality in this area for times other than 1985 when the Howe-investigation wells were sampled for PAHs and PCP.
Although contaminant levels have shown a decrease since the pump-out system was installed, PAHs detected in 1990 and 1991 sampling rounds have continued to exceed state and federal health-based screening values for cPAHs or nPAHs in off-site monitoring wells: W121 (cPAHs 0.052 µg/L), W122 (nPAHs 11 µg/L), W125 (nPAHs 0.73 µg/L), W126 (cPAHs 0.23 µg/L; nPAHs 0.4 µg/L), W129 (nPAHs 0.37 µg/L), and W223 (nPAHs 88 µg/L). Although only one of these recent findings was included among the maximum levels in Table 5, they indicate groundwater contamination persists at levels of potential concern if humans use the water regularly in a manner that results in direct human exposure. PCP concentrations in off-site groundwater samples have decreased greatly in 1990 and 1991 samples. Since 1989, the concentration of PCP in all samples from off-site monitoring wells was less than 50 µg/L.
In August and September 1990, shallow groundwater from four off-site monitoring wells (W122, W124, and W125 to the east, and W128 to the south) were sampled and tested for total chlorinated dibenzodioxins and chlorinated dibenzofurans. Data from these wells showed tetra-, hexa-, and octachlorinated dibenzofurans. Specifically, the 2,3,7,8-TCDF isomer was identified in wells W122 (0.0072 ng/L), and W128 (0.0014 ng/L). Penta- and hexachlorinated dibenzo-p-dioxins were detected in the sample from W125 and hepta- and octachlorinated dibenzo-p-dioxin isomers were found in samples from each of the four off-site wells. 2,3,7,8-TCDD was not detected in any of the samples (detection limits 0.0014 to 0.0023 ng/L). These findings are also included in Table 5 (Appendix A). Data collected from monitoring wells at the Howe chemical fire did not indicate high levels of PCP or PAHs in their locations/depths at the time they were sampled in May 1985 (see Figure 13 for locations), but samples were not tested for chlorinated dibenzodioxins or chlorinated dibenzofurans.
3. Surface Water
a. Highway 100 drain tile
A shallow drain-tile system for Highway 100 intermittently intercepts surficial groundwater from the site and discharges it to a storm sewer. Water from the storm sewer, along with urban runoff, outlets into a pond at a golf course northeast of the site (see Figure 14). Water from this system just east of the site contained 30 µg/L nPAH and 570 µg/L PCP in November 1987. In late 1990, when water was again noted in the drain tile system, maximum levels of 64 µg/L PCP and 46 µg/L nPAHs were found; cPAHs were not detected. Maximum findings in eight samples collected in 1991 were substantially lower. Table 7, found in Appendix A, summarizes the early monitoring results from the drain-tile system, storm sewer outfall, and Shingle Creek (background).
Drain tile water combines with runoff from other area storm sewers and flows from the golf course pond into Shingle Creek. Sampling of the drain tile outlet and the creek (upstream) showed that the contribution of PAHs assumed to be from the site was minimal in November 1990 and April through December of 1991; showing that there are probably other sources of these compounds also reaching the drain tile and pond. No contribution of PCP to the creek was detectable in November 1990: for example the sample from the drain tile system contained 11 µg/L PCP, but none (<6 µg/L) was detectable at the pond outlet (Barr 1992a).
The recent, 1992 and 1993, monitoring results from the drain tile system and the outfall have showed that the levels of potentially site-related contaminants have remained lower in the drain tile waters since the pump-out system began at the Joslyn site. The levels of contaminants in the outfall have remained low over the period of monitoring (1990-1993); suggesting little impact due to the levels of contaminants in the drain tile.
The sometimes slightly higher level of PAHs in the outfall is probably not significant given the small estimated input of the storm sewer to the estimated total flow of the creek. In 1991, Barr estimated the flow rate in the drain tile to be 30 to 50 gallons per minute and that of Shingle Creek roughly 10 times greater (Barr 1992b).
b. Shingle Creek
In 1990 and 1991, surface water in Shingle Creek was also sampled at an upstream position. Generally, the level of cPAHs was greater in the upstream creek sample than in the corresponding drain tile sample. In contrast, the level of nPAHs was typically higher in samples from the drain tile than in the sewer outlet and in the creek samples. In nearly all samples (including creek background), the levels of cPAHs exceeded the Aquatic Life Criteria for Shingle Creek water; Aquatic Life Criteria are listed in Appendix B. In the November 1990 or the eight 1991 creek samples, essentially no PCP was detected (<6 µg/L) at or above the detection limit (Barr 1992b), indicating there is no significant source of PCP to the river upstream from the outlet point for the drain tile system. Past contributions of PCP from the drain tile system are unknown as higher levels of PCP (29 - 64 µg/L) were found in the drain tile (prior to discharge) in 1990, at a time the outfall and creek were not sampled to check for contribution to the creek (Barr 1992a). Sediments of the creek were not tested for any residual PCP from past releases.
Recent (1992 and 1993) samples tested from the creek did not show any significantly different levels of PAHs in the upstream waters (background) compared to past monitoring. This suggests that the general contamination of the creek from upstream sources is an ongoing condition which is independent of the Joslyn site. The contamination in the creek has typically been within the same order of magnitude as concentrations from the drain tile system.
c. Twin Lakes
Suface water runoff from the Joslyn site to Twin Lakes is unlikely, due to the flat topography of the site. Moreover, groundwater in both the upper and lower aquifers flows east from the lakes, toward the site. Monitoring of Twin Lakes in 1985 indicated that water quality of the lake is not affected by the site. Although some water samples from Twin Lakes did contain low levels of PAH compounds, background sample concentrations suggested these were not due to the site; the highest levels were found in samples from the north end of the upper portion of the lake (MDH 1990). PCP was not detected in 1985 samples of lake water.
Investigation of the wetlands west of the site revealed a small area of contaminated soil (termed non-conforming soils). This was excavated and placed in the first lift of the land treatment unit. The wetlands situated north of the site were also investigated to the depth of the water table in June 1989. No PAHs or PCP were detected in borings there.
d. Ryan Lake/ Ryan Creek
Ryan Lake and Ryan Creek are perched above the water table and thus will not recieve groundwater from the site moving to the east. As a result, the lake and creek are not likely to be affected by groundwater contaminants from the site.
Air quality off-site has not been tested. Blowing dusts were noted in the past (MDH 1990); however, water is currently applied during soil evcavation and soil moving. Water is also used to control dusts on transportation areas, such as the road into the site. Odors detected during site visits were noticeable north and south of the site's boundary as well as on the site itself.
Results of ambient air sampling near the LTU and the site's perimeter in 1990 and 1991 ranged from nondetected to 0.79 mg/m3 for total suspended particulates (Barr 1990a, 1992b). Results of 1991 sampling near the site's south central border showed a maximum of 141 µg/m3 (24-hour concentration) and an average of 58.3 µg/m3; Total dust, rather than PM10 was measured (Barr 1992b). The national primary and secondary ambient air quality standards for particulate matter (PM10) are 150 µg/m3 as a maximum 24-hour concentration and 50 µg/m3 as a maximum annual average for PM10. The sampling results suggest that the levels of PM10 off-site were likely below the ambient air quality standards, since particulates of this size probably comprised only a portion of the total dust sample collected.
For specific contaminants of concern, there has been no monitoring of ambient air at the site's perimeter or off-site. However, limited on-site monitoring in 1991, where known contaminants were likely to be present in the air, did not detect coal tar pitch volatiles (CTPVs), naphthalene, phenol, or BTX compounds above OSHA workplace standards. PCP was measured above the occupational standard in only a single sample taken near on-site excavating. Total hydrocarbons around the LTU have only been detected infrequently and at low levels. Air monitoring results are presented in Table 6 of Appendix A.
Details of sampling methods and quality assurance/quality control procedures have been provided to MPCA for each round of ground-water monitoring. Stabilization tests recommended by MPCA have been conducted on all monitoring wells before sample collection. The laboratory used for sample analysis is a participant in the EPA National Contract Laboratory Program for Superfund. For each round of sampling, field blanks and blind duplicates have been analyzed.
EPA Method 625 has been used for analysis of samples for phenolic compounds, and a modified EPA Method 625 has been used in analyses for PAH/heterocyclic compounds. The same methods have been used for the analyses of PAH and phenolic content of soil samples, except for the use of the Soxhlet extraction method for soils. Results of soil and ground-water analyses have indicated good precision of test results and only infrequent detection of contaminants in blanks. Detection limits for PAH compounds have usually been in the low ng/L range, except for highly contaminated samples. The methods of quality assurance and quality control used have led MPCA technical staff to conclude that data for the Joslyn site investigation have a generally high level of reliability and precision.
The RI monitoring well samples that were analyzed for arsenic, chromium, and copper were filtered samples. Samples such as these are often filtered, because monitoring wells generally are not pumped regularly and are not as well-developed as residential wells. These conditions can lead to the presence of sediments in the water samples, which in turn can yield sampling results not representative of the mobile ground-water constituents in unfiltered samples. However, the process of filtering may also remove small colloidal metal particles which are mobile in groundwater (EPA 1989a). When samples from potable wells are analyzed for metals, they are not filtered, because filtering may lower metal concentrations below levels normally present at the tap.
Because of the different sampling techniques used for metals monitoring in monitoring wells versus potable wells, the RI analyses of metals in groundwater at the site may not be representative of metal concentrations that would be found in unfiltered samples from potable wells.
The site's surface is free of debris. Only earthmoving and treatment equipment remains present. There are no known physical hazards on the site.