PUBLIC HEALTH ASSESSMENT
NEW BRIGHTON/ARDEN HILLS
(a/k/a U.S. ARMY TWIN CITIES AMMUNITION PLANT)
NEW BRIGHTON, RAMSEY COUNTY, MINNESOTA
| Age |
|Anoka County||Hennepin County|
|< 5|| |
|> 64|| |
| Age |
| Age |
|Anoka County||Hennepin County|
| Age |
| Age |
|Anoka County||Hennepin County|
| American Indian, |
| Asian or |
|< 5 years||401||176||240||203||436||40||1496|
|> 65 years||131||76||73||38||96||11||425|
| American Indian, |
| Asian or |
|< 5 years||434||367||581||340||252||36||324||196||392||302||3224|
|> 65 years||421||113||182||274||170||889||145||179||472||2845|
Derived from the U.S. Army Environmental Hygiene Agency's
Ecological Assessment Report
Site A is an area of approximately 7.5 hectares at the northern boundary of the plant. It appears to be fairly flat, but a slight change in elevation is sufficient to produce an area of intermittent marsh in the southeastern corner. The cover is mainly grass; trees are intermittent at the eastern end of the area. There are shrubby willows in the marsh areas. One building is on site: the extremely long and narrow indoor firing range (Bldg. 308). The area has been divided into five subsites. These were in use from the 1940s until at least 1966.
Past disposal activities in this area included burial of mercurous nitrate-contaminated cartridge cases; dumping of sewage sludge; open burning of primer, tracer, and incendiary waste; burning of flammable liquids; and burial of miscellaneous debris. Most burning seems to have been carried out in pits rather than on the surface. There is a landfill face in Area A-5 with exposed debris, such as paint cans. Surface soils and sediments are contaminated with metals.
Site B, just to the east of Site A, consists of three separate subsites totalling about 0.9 hectare along the northern boundary of TCAAP. These subsites are in an area of intermittent, small marshes. There is little relief in the area. There are numerous clusters of trees, especially around a farmstead that was abandoned before construction of TCAAP. There is no documentation of hazardous substance disposal at this site, although it is possible that small amounts of sewage sludge were dumped before 1966. The southeastern corner of Area B-3 is part of a large landfill area.
Site C is a flat grassland of 6.7 hectares just south of Site A. Area C-1, the subsite of primary concern, is about 1.4 hectares. From 1947 to at least 1957, the site was used for the open burning of lumber, solvents, oils, and other production materials. Burning of brush and grass continued until 1970. Solvents and oils were burned in pits.
Site D is a 0.7-hectare area on the slopes of the Arsenal Kame. It has been completely cleared, and it supports only a sparse growth of grasses and forbs (herbs other than grass). Most of the area has been covered by a clay cap and structures associated with an ISV. Pits at this site were used for burning oil, solvents, rags, floor sweepings, and powder from sumps in production buildings. Thousands of gallons of solvents were placed in these pits; the sandy substrate at this location provided a pathway to the groundwater. Additional materials disposed of were neutralized cyanide solutions from plating operations and wastes from decontaminated machines and buildings. The site was in use from 1950 until at least 1968, and perhaps as late as 1973.
Site E comprises 5 hectares of the Arsenal Kame. This portion of the kame is composed of grassland and patches of forest; Subsite E-2 was last cleared in 1980 and has only light vegetation. There is a considerable amount of manmade relief across the site, including a 300-meter fill face with a variety of protruding debris. The top of the landfill has been covered with clean fill, graded, and revegetated with grasses. This area was a dump for noncombustible rubbish dating from the building of the plant until late 1949. Unidentified chemicals may also have been disposed of there. E-2 also was used as a burning area for rubbish.
Site F is about 4 hectares and is low on the eastern slope of the Arsenal Kame. The disposal area is a plateau that falls off abruptly to the south. This level area has a hard substrate of gravel with a light covering of forbs and grasses. There are a few scattered trees, mainly around the perimeter of the area. This site was used from 1950 to at least 1978 for burning scrap powder and ordnance, including mercurous nitrate-contaminated cartridge cases, in tanks and kettles. Pits for the burial of those cases and of cyanide-contaminated pots were also located on the site. These activities generated the highest levels of surface contamination on the property. Some use was made of the site until at least 1981. Site F shows some evidence of chemical stress; a small plot of unvegetated ground is in an area of high surface contamination. The sparse vegetative cover over other parts of this site may result in part from past disturbances there; it was in use more recently than any other site.
Site G covers about 1.7 hectares at the base of the Arsenal Kame, about 200 meters south of Site F. This site functioned as a general purpose dump from the 1940s until late 1976. Some of its contents include material from demolished buildings, urethane foam, floor sweepings, scrap metal and metal grindings, and ashes from scrap paper-burning cages. Most of the site is now an artificial plateau characterized by a fairly high and steep fill face with protruding debris. Water sampled from a seep at the base of this face and shows some radioactivity. This plateau has been covered with a clay cap and is the site of another ISV system. Just off the fill areas to the north and south are bands of trees; otherwise, the area is lightly vegetated. Immediately to the northeast of the site boundary is a small pond (0.1 hectare) that receives drainage from the site. This pond is heavily used by wildlife in the vicinity, because it is some distance to any other standing water.
Site H is in the southeastern corner of the property. It occupies 4.5 hectares of rolling grassland on the north shore of Sunfish Lake; there are intermittent trees. A cage used for burning wood and paper trash was located near the shore until late in 1946. Another cage located west of this spot was used for similar purposes from 1953 to 1968 or 1969. A considerable portion of the area has been used as a dump. Aerial photographs show that an entire bay of the lake was filled in during World War II. There is a fill face along a portion of the lake shore, and some minor debris is visible on the land surface and on the lake bottom. Dumping probably ceased when off-site waste disposal began in 1967. Solvents, incinerator clinkers, and ash from the burning cages are some of the materials that were dumped at Site H. With a maximum depth of 1.6 meters and a median depth of 1.25 meters, the lake is subject to winter kill. The consequent lack of large predatory fish has made it suitable for use as a rearing pond for game fish to be released by the Minnesota Department of Natural Resources.
Site I is in the industrial area of the plant and corresponds to Building 502 and its immediate surroundings. Part of the Site I facility has been used to produce artillery shell forgings. The forges were cooled by water that was discharged to floor drains along with water used in general clean-up operations. The floor drains in this part of the building were connected to the storm sewer system rather than the sanitary sewer. The forging equipment used large quantities of hydraulic fluid containing high percentages of PCBs. Leakage from this equipment, lubricants used in the forging process, and other contaminants consequently had a pathway into the storm sewer. The storm sewer discharged into a ditch that feeds into Round Lake through a sewer outfall at the intersection of Highways 96 and 10.
During 1942 and 1943, about 1.9 million liters of waste were discharged from this building and Building 501 into the lake each day. In 1944, when the forges were added to both of these buildings, daily discharges increased. They remained high until the end of the war. The storm sewer system was altered in 1953 in response to complaints about grease and oil pollution in Round Lake; water from some of the floor drains was subsequently sent to the sanitary sewer. For about 1 year before this conversion, Round Lake may have received about 3.8 million liters (1 million gallons) of waste water that was still being discharged to the floor drains. In 1969, Honeywell, the tenant of the building, noted that many floor drains were still connected to the storm sewer. This situation has since been remedied.
Quantities of PCBs were found in the soils outside the eastern end of the building. These soils were excavated and contained in a facility on the site. Site I is a major point of origin for VOCs that are contaminating the groundwater. These contaminants appear at relatively low concentrations in the shallow Unit 1 aquifer, which might contribute groundwater to Round Lake. However, the remedial investigation calls for additional study of this aquifer. Site I has also been the location of depleted uranium milling operations since 1974. Low levels of depleted uranium have been detected in the lake sediments near the sewer outfall. The depleted uranium in the samples was below the levels of uranium that occur naturally in the soil. Site I is still in use as a production facility.
Site J is a portion of the TCAPP sewer system. It is relevant to this assessment because of an emergency overflow provision that allowed sanitary sewer wastes to flow into Round Lake. The overflow outfall entered Round Lake at a point west of the storm sewer outfall. This part of the sewage system was blocked off in 1982 or 1983. There have been at least 5 on-site and 14 off-site sewer main breaks that might have necessitated diversion of either treated or untreated sewage to Round Lake. Generally, it is unknown how much sewage may have been diverted to the lake from this source during the plant's history. There are records of several multimillion-liter discharges. A great variety of contaminants could have been included in this sewage, including depleted uranium, other metals, and cyanide.
Site K, which corresponds to Building 103 and its immediate surroundings, is adjacent to Rice Creek. Rice Creek is used for fishing and is classified as suitable for wildlife uses. Building 103 was used for .50-caliber ammunition manufacture during World War II. From 1946 through 1951, cleaning, storage, and degreasing of production machinery took place there. Ammunition manufacture resumed in 1951 and was finally terminated in 1957. The building was reactivated in 1961 and continues to be used; products were changed from ammunition to fuses, mines, and weapons systems. Degreasing, metal finishing, and painting have been important activities in this most recent phase.
There is significant contamination of soils and groundwater with both solvents and zinc beneath Building 103. The piezometric surface of the perched aquifer beneath the building is higher than the surface of Rice Creek. Thus, this groundwater has the ability to move towards the creek. In the past, the storm sewer has provided a pathway for contaminated groundwater to enter the creek. Currently, a system is in place that extracts contaminated groundwater and sends it through an air-stripping tower to remove most of the volatile organic solvents, but the tower does not remove metals. The processed water is then discharged to Rice Creek. Analysis of this effluent has occasionally shown levels of zinc in excess of acute toxicity levels. The remedial investigation calls for additional sampling of surface water and sediments in the creek to delineate and quantify more adequately any contamination that may exist.
Site 129-3 is in the middle of the Arsenal Kame, southeast of Site E. At one point, their boundaries are separated by about 50 meters. The site occupies about 0.5 hectare of savanna, which slopes gently to the west. This site was used for the disposal of sump wastewater, mainly from a lead styphnate primer mixing process. For this purpose, two pits, with a total area of about 900 square meters, were excavated. Neutralized sump water was dumped into the pits and allowed to percolate into the ground or evaporate. Residue remaining in the pit was then burned. There may have been a separate pit for the disposal of mercurous nitrate. This site was in operation from December 1971 until sometime before July 1976. The pits were filled in and sealed sometime during 1977.
Site 129-5 is a 2.2-hectare area of mixed terrain near the western shore of Lake Marsden. About half of the area in the northern edge of the firing range consists of a savanna habitat that slopes gently toward the lake and is cut by gullies. The gravel surface is sparsely revegetated. In 1945 or 1946, pits for burning explosives were established in an unspecified location in the southeastern quadrant of the site. Some of the northeastern corner of the site may have been included in a large area that was established in 1948 for burning ammunition and smokeless powder. This operation ceased in 1951. The area was subsequently mined and then covered over by gravel-washing activities. Some solvents may have been burned at the site, and ammunition debris is visible on the surface.
Site 129-15 occupies 2.7 hectares of the kame and lies about 100 meters from Site F, which is on the same east-facing slope. This site, the northern part of F, and the intervening ground are covered with forest interspersed with small clearings and roads. Animals that are part of the TCAAP deer herd are frequently found in this area. The most prominent feature of the site is a landfill; it has created an artificial plateau with a steep fill face about 7 or 8 meters high. The top of the fill area is covered with gravel and is only partly revegetated with herbs and forbs. This area was used as a general landfill for nonsalvageable and supposedly noncombustible materials, including urethane foam and plastics and demolition debris. It was active from 1970 or 1972 until 1978.