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[SWMU O-1]

SWMU O-1 Work Plan

RL 17 Project, February 1996

Soils: Tarrant Association, gently undulating

Known: The oxidation pond was an evaporation pond constructed in 1975 for the disposal of waste liquids and sludges from the bluing operation. The pond was lined with a plastic liner. In 1985, the pond was filled in with surrounding soil and the liner system was destroyed during excavation activities (ES, 1993b). During the 1992 Environmental Assessment site visits performed by Parsons ES, CSSA personnel stated that the liner was bulldozed and shredded during destruction of the oxidation pond. Geophysical surveys of the oxidation pond in March 1995 showed a disturbed area. Drilling and sampling around the area in 1995 indicated only pieces of black plastic material in one boring. A 1995 soil-gas survey indicated a "hot spot" of PCE in soil gas. A subsequent investigation into the integrity of the liner was performed by AL/OEB and Parsons ES personnel on January 8-10, 1996, and the liner was found in pieces throughout the area, with no one piece being greater than about 5 feet in diameter. The site is depicted in Figure O1-1.

Previous Investigations: The Environmental Assessment verified the site location and that it had been bulldozed and graded to land surface in 1992 (ES, 1993b). In 1995, CSSA decided to initiate field work at seven potential sources of groundwater contamination under the work plan for AL/OEB contract F33615-89-D-4003, order 67. A geophysical survey using EMI and GPR techniques was performed in March 1995 (Parsons ES, 1995a). The apparent ground conductivity, shown in Figure O1-2, indicates the extents of the oxidation pond while the in-phase EMI data, shown in Figure O1-2, do not reveal any metal debris underneath the ground surface (Parsons ES, 1995a). The increase in conductivity values in Figure O1-2 indicates that the ground has been disturbed. The GPR confirmed the results of the EMI survey, indicating the site to be about 75 feet in diameter and less than 5 feet deep.

Drilling and sampling were also conducted at the site in March 1995 (Parsons ES, 1995b). The field investigation revealed that the site contained weathered limestone and caliche at the surface with little vegetation. Two feet of fill was found in sample OX-SB3 and 4 feet in OX-SB2 (Parsons ES, 1995b). The fill consisted of clay, limestone fragments, sand, and waste material. Results indicated the presence of PCE, toluene, xylenes and the metals cadmium, chromium, lead, and nickel (Table O1-1).

A surface water sample detected positive for toluene at a concentration of 0.034 mg/l (Table O1-1). The MCL for toluene, as promulgated under the Safe Drinking Water Act, is 1.0 mg/l, well above the level detected in the surface water sample. For comparison of water samples, the MCL specifies the maximum concentration in groundwater for residential exposure conditions. No perched groundwater was observed during drilling at SWMU O-1. During a 1995 soil gas survey, both PCE and TCE were detected at the oxidation pond. The detected concentrations of PCE correspond with the results of the soil samples and form contours approximating the dimensions of the pond (see Figure O1-4). The highest concentrations are found where the pond was deepest. The high levels of PCE indicate residual saturation of PCE in the soil which could persist as a source of groundwater contamination. This area of contoured soil-gas concentrations is referred to as a "hot spot". Further soil-gas survey efforts to define the size of the "hot spot" were conducted in November and December 1995. The preliminary evaluation of the data indicated that the highest concentrations are in the south central area of the O-1 unit. The soil-gas surveys and results at O-1 and other SWMUs pertinent to the AL/OEB order 67 groundwater investigation are be discussed in "Groundwater Investigation and Associated Source Characterization" (Parsons ES, 1996d).

Table O1-1 - Chemical Constituents Detected in Soil and Groundwater

 

8260 Volatile Organic

8270 SVOC

Compounds

Compounds

6010 Metals

Sample ID

Depth (ft)

PCE

Toluene

m,p-Xylene

Phth.

Cd

Cr

Pb

Ni

Soil

(mg/kg)

(m g/kg)

(mg/kg)

OX-SB1

3.5 - 5

<0.005

<0.003

<0.005

<1000

<0.25

4.6

4.6

2

OX-SB1

15 - 16

<0.005

<0.003

<0.005

5300

0.48(U)

3.8

3.4

4

OX-SB1

26.5 - 27.5

0.012

0.005

0.005

4700

0.27(U)

1.3(U)

1.6

6.6

OX-SB2

0 - 2

46

<0.3

<0.5

4800

1.5

320

12

18

OX-SB2

0 - 2 Dup

49

<0.3

<0.5

5500

4.8

730

28

73

OX-SB2

4 - 5.7

<0.5

<0.3

<0.5

5500

<0.25

2.5(U)

<1.5

2.4

OX-SB2

11 - 12.5

<0.005

<0.003

<0.005

<1000

0.65(U)

5.3

4.6

6.4

OX-SB3

0 - 2

0.015

<0.003

<0.005

<1000

0.33(U)

34

2.7

2.3

OX-SB3

6 - 8

<0.005

<0.003

<0.005

<1000

0.35(U)

5.3

2.1

3.4

OX-SB3

12.5 - 13.5

<0.005

<0.003

<0.005

<1000

0.56(U)

4.9

3.7

3.4

OX-SB4

0 - 2

<0.005

<0.003

<0.005

<1000

0.49(U)

9.5

3.6

3.6

OX-SB4

4 - 6

<0.005

<0.003

<0.005

<1000

<0.25

4.6

2.2

3.6

OX-SB4

11 - 13

<0.005

<0.003

<0.005

<1000

0.51(U)

4.8

3.2

3.1

OX-SB4

11 - 13 Dup

<0.005

<0.003

<0.005

<1000

0.51(U)

5.8

3.2

3.1

OX-SB4

26 - 27.5

<0.005

<0.003

<0.005

<1000

0.63(U)

3.1

3.3

7.6

Standard 1

Comparison

<2

Unk

Unk

Unk

Unk

N/E

N/E

N/E

N/E

Criteria

 

 

 

 

 

 

 

 

 

Comparison

>2

Unk

Unk

Unk

Unk

0.55

7.5

69.3

29.4

Criteria

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Standard 2

 

 

 

 

 

 

 

 

 

MCL

all

207

3,630

5,800

N/A

1020

5100

1000

20400

 

 

 

 

 

 

 

 

 

 

ND = Analytes were not detected at concentrations exceeding practical quantitation limits.

U = Estimated.

Unk = Unknown

Phth. = The phthalate detected at O-1 was di-n-butylphthalate

PCE = Tetrachloroethene (Perchloroethene)

mg/kg = Milligrams per kilogram

u g/kg = Micrograms per kilogram

ug/L = Micrograms per liter

N/E = Background level has not been established.

mg/l= Milligrams per liter

N/A = Not applicable