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PRELIMINARY PUBLIC HEALTH ASSESSMENT

DEL AMO FACILITY
LOS ANGELES, LOS ANGELES COUNTY, CALIFORNIA


ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS

This section presents contaminants identified for further evaluation or follow-up. Selecting these contaminants does not necessarily mean that a health threat exists. We evaluate these contaminants in the subsequent sections of the preliminary public health assessment and determine whether exposure to them has public health significance. CDHS/ATSDR selects and discusses these contaminants based upon the following factors:

  1. concentrations of contaminants on and off the site;


  2. field data quality, laboratory data quality, and sample design;


  3. comparison of on-site and off-site concentrations with health assessment comparison values for noncarcinogenic and carcinogenic endpoints; and


  4. health concerns expressed by the community.

The data tables included within the On-site and Off-Site Contamination subsections present the maximum concentration of each contaminant detected for comparison with existing health guidance values. Contaminants exceeding these values, or for which no value is available, are selected for further evaluation. When selected as a contaminant of concern in one medium, that contaminant will be reported in all media. The tables in this section include the following acronyms:

  • CREG Cancer Risk Evaluation Guide


  • EMEG Environmental Media Evaluation Guide


  • NREG Noncancer Risk Evaluation Guide


  • MCLG Maximum Contaminant Level Goal


  • MCL Maximum Contaminant Level


  • PMCLG Proposed Maximum Contaminant Level Goal


  • LTHA Lifetime Drinking Water Health Advisory


  • ppm parts per million (equivalent to milligrams per kilogram [mg/kg]; a milligram is one thousandth of a gram)


  • ppb parts per billion (equivalent to micrograms per kilogram [ug/kg]; a microgram is one millionth of a gram)

Health guidance values used to select contaminants for further evaluation include Environmental Media Evaluation Guides (EMEGs), Cancer Risk Evaluation Guides (CREGs), Noncancer Risk Evaluation Guide (NREGs), and other relevant guidelines. EMEGs are media specific values developed by ATSDR to serve as an aid in selecting environmental contaminants of concern that need to be further evaluated for potential health impacts. EMEGs do not consider carcinogenic effects and are derived from ATSDR's Minimal Risk Levels (MRLs). NREGs also consider noncancer health effects, but are derived using EPA's Reference Dose (RfD). Both MRLs and RfDs are estimates of daily exposure to a chemical considered unlikely to cause noncancer adverse health effects.

CREGs are estimated contaminant concentrations which theoretically could cause one excess cancer in a million persons exposed over a lifetime. CREGs are calculated from EPA's cancer slope factors.

EPA's Lifetime Drinking Water Health Advisory (LTHA) defines a concentration in drinking water at which noncancer adverse health effects would not be expected to occur. EPA's Maximum Contaminant Level Goal (MCLG) is a drinking water health goal. These values also include a margin of safety and represent a level where no known or anticipated adverse health effects are expected to occur. Proposed Maximum Contaminant Level Goals (PMCLGs) are MCLGs that are being proposed. Maximum Contaminant Levels (MCLs) represent contaminant concentrations that EPA deems protective of public health (considering the availability and economics of water treatment technology) over a lifetime (70 years) at an exposure rate of 2 liters water per day. While MCLs are regulatory standards and reflect economic and technological feasibility, LTHAs, PMCLGs, and MCLGs are based solely on health considerations.

A. TOXIC CHEMICAL RELEASE INVENTORY (TRI) SEARCH

The Toxic Chemical Release Inventory (TRI) contains information on estimated annual releases of toxic chemicals to the environment (via air, water, soil or underground injection) which is reported by companies to EPA. TRI data can be used to give a general idea of the current environmental emissions occurring at a site and in the area surrounding a site. TRI data may also be used to determine whether the on-going emissions from reporting facilities may be contributing an additional exposure to the nearby population.

We conducted a computer search of TRI data for 1987, 1988, and 1989 (the years for which TRI data were available at the time this preliminary public health assessment was written). Since the former rubber manufacturing facilities stopped operating in the early 1970s, no information about them would be contained in TRI. However, the TRI search of the zip code area in which the Del Amo site is located showed information on environmental releases from other companies in the same zip code area. This information may be representative of background conditions in the general vicinity of the site.

In 1987, five companies reported releases totalling 532,919 pounds of 15 different chemical compounds into air, 1,000 pounds of 2 compounds onto land, and none to water or underground injection wells. In 1988, six companies reported air releases totaling 419,779 pounds for 17 compounds. Four companies reported releases of 16 compounds into air in 1989. No land, water, or underground releases were reported for 1988 or 1989. Some of the compounds listed as being released into air include styrene, ethylbenzene, xylene, toluene, and sulfuric acid, as well as copper, chromium, and lead compounds.

B. ON-SITE CONTAMINATION

The information presented in this section only describes the currently available data for the 3.7-acre waste disposal area consisting of waste ponds 1A, 1B, and 1C and waste pits 2A through 2F. EPA is currently developing a workplan to fully characterize contamination of the full 280-acre Del Amo site.

Sub-surface Soil/Waste - Waste Pond 1A

As described previously, Western Waste Industries (WWI) excavated pond 1A between 1982-1985. There is incomplete information on how samples were collected from waste pond 1A before or during excavation(7). Based on records available from DTSC, pre-excavation samples of the materials and soil in waste pond 1A mainly contained metals and polycyclic aromatic hydrocarbons (PAHs). The PAHs are a group of chemicals formed during incomplete burning of coal, oil and gas, garbage, and other organic substances(25). As shown in Table 1, some of the PAHs found in pond 1A prior to excavation included naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, and anthracene. The metals barium, chromium and arsenic were also found at levels above health comparison values, but the levels were within the background levels generally reported for the western United States(26).

After excavation of pond 1A to an approximate depth of 25' below ground surface (bgs) in 1984, 14 soil borings were drilled in and around the pond to determine the extent of vertical and lateral migration of contaminants. Seven soil borings were made to depths of within 3' of the Bellflower aquitard (65-70' bgs); 3 borings within the floor of the excavation area (western end, middle and eastern end), 2 borings in the space separating pond 1A and 1B, and 2 borings south of the excavation area. The samples taken from these borings showed lower levels of some of the contaminants still remaining. Naphthalene concentrations ranged from about 800 ppm at 30' bgs to about 100 ppm at 40' bgs. Volatile aromatic hydrocarbons (benzene and ethylbenzene) were about 50 ppm at 30' and 40' bgs. No contaminants were detected at 45' bgs. DTSC allowed WWI to backfill the excavated area with clean fill. No further sampling of the backfill materials has occurred to date(8,10).

Subsurface Soil/Waste: Waste Ponds 1B and 1C

In 1984, Dames and Moore completed two borings each in waste ponds 1B and 1C in order to characterize the soil cover, the waste, and the soil beneath. Based on visual observations, each of the waste ponds appeared to be about 8' deep. The cover fill in waste pond 1B appeared to be 3.8' deep. Dames and Moore observed sludge like waste exposed at ground surface in some parts of waste pond 1C due to the absence of cover soil. Waste materials found in the ponds reportedly resembled a clay like sludge(1).

Dames and Moore did not take any surface soil (0-3" deep) samples for either waste pond. As indicated in their 1984 report, for each waste pond Dames and Moore collected 24 total samples (12 core samples from each boring location) at 2.5' to 5' intervals below ground surface to a depth of 45'. For each waste pond, six samples out of the 24 taken were selected for analysis. The analyzed samples mainly consisted of underlying soil samples or a mixture of waste and underlying soil. One of the six samples from waste pond 1C consisted of a mixture of soil cover and waste and another of waste only. No analysis of cover soil alone was done since none of the samples analyzed for either waste pond were taken from depths less than 5'. The one sample taken at 5' which was analyzed consisted of both waste and cover material and contained contaminants(6,12).

As shown in Table 2, contaminants found in soil boring samples taken from waste ponds 1B and 1C primarily consist of metals, PAHs, and volatile aromatic hydrocarbons (VAHs) such as benzene, ethylbenzene, and toluene. These same substances were found in waste pond 1A prior to excavation. Dames and Moore reported values collectively for some PAHs. The maximum concentration of all contaminants were found in samples taken between 5' and 10' bgs, except for naphthalene and benzene which showed a maximum concentration of 5,800 ppm at 15' bgs and 450 ppm at 45' bgs, respectively. Concentrations for metals are similar to background concentrations for the western United States(26).

Dames and Moore tried to make samples representative of the subsurface soil and wastes for characterization of ponds 1B and 1C. However, with only two boreholes in each of the half- acre waste ponds, the analytical results may not be representative. EPA estimates about 10,000 cubic yards of wastes and contaminated soil may be present in ponds 1B and 1C(1).

Subsurface Soil/Waste: Waste Pits 2A-2F

In 1984, Dames and Moore completed three soil borings in waste pit 2A in order to characterize the cover soil, waste, and soil beneath the waste. No surface soil samples (0-3" deep) were taken. Eight core samples were collected at 1.5' to 5' intervals to a depth of 25 feet. Based on visual observations of core samples, pit 2A appears to have a one foot deep soil cover layer and an overall depth of 21'. Three samples out the eight core samples were analyzed. The soil cover was not analyzed(6,12).

To characterize pits 2B through 2F, Dames and Moore drilled one soil boring in each of the pits. Visual inspection of core samples indicated that the soil covering the sludge-like waste in pits 2B through 2F ranged from 3.2' to 8' thick. Waste pits 2B-2F ranged in depth from 17' to 22'. Dames and Moore collected up to seventeen samples from each boring location at 2.5' to 5' intervals below ground surface to a depth of 51.5'. Two to four samples from each boring location were selected for chemical analyses.

Dames and Moore observed two types of wastes in pits 2A through 2F, a plastic, clay-like waste and a thick fluid tar-like waste which hardened to a solid upon exposure to air. As compared to Ponds 1B and 1C, pits 2A-2F apparently contain more VAHs, mainly benzene and ethylbenzene, than PAHs. As shown in Table 3, the highest levels of contaminants were found in samples taken at depths of about 7' to 15' bgs. A soil cover sample from pit 2F taken at 5' bgs showed mainly nondetectable levels for all contaminants except for benzene (1 ppm) and ethylbenzene (2 ppm). Concentrations of the metals arsenic, barium, cadmium, chromium, copper, and lead were similar to background concentrations found in other soil from the Western United States.

Table 1:

Contaminants in On-site Sub-surface Soil/Waste: Waste Pond 1A
Contaminant Concentration (ppm) (Before Excavation) Concentration (ppm) (After Excavation)(1) Comparison Value
ppm source
Benzene NA 50(2) 24 CREG
Ethylbenzene 140 55 200 NREG
1,1'-Biphenyl 250 ND 100 NREG
Acenaphthene 1,520 ND 120 NREG
Acenaphthylene 2,940 96.9 NA NA
Anthracene 628 ND 600 NREG
Benzo(a)anthracene 402 ND NA NA
Chrysene 352 14 NA NA
Fluorene 2,290 237 80 NREG
Fluoranthene 966 11.0 80 NREG
Indene 220 ND NA NA
Methylnaphthalene 940 NA NA NA
Naphthalene 16,000 804 8 NREG
Phenanthrene 13,000 447 NA NA
Pyrene 2,350 217 60 NREG
Styrene 540 ND 400 NREG
Arsenic 18 NA 0.6 NREG
Barium 124 NA 140 NREG
Chromium 18 NA 10-VI(3)
2000-III
NREG
Copper 25 NA NA NA
Lead 17 NA NA NA
Nickel 17 NA 40 NREG
Zinc 106 NA NA NA

Source: Reference 10
NA = Not Available;ND = Not Detected

(1) At 5' below floor of excavation, or 30' bgs; floor of excavation was approximately 25' bgs in the deepest part of the excavation.
(2) Approximate analytical result.
(3) Comparison values for hexavalent chromium (Chromium V) and trivalent chromium (Chromium III).

Dames and Moore tried to make samples representative of the soil and waste contained in pits 2A through 2F. However, with only three boreholes in pits 2A and one each in pits 2B through 2F, a total area of about 13,000 square feet, the analytical results may not be representative. EPA estimates about 7,000 cubic yards of wastes and contaminated soil may be present in the pits(1).

In 1987, DTSC contracted with Woodward-Clyde to evaluate the extent of vertical and lateral spread of contaminants from the waste pits and ponds at the Del Amo site. Soil samples were collected from 13 soil borings drilled mainly around the waste pits 2A through 2F at varying depths up to 57.5' bgs. No samples were collected adjacent to Pit 1B. Selected samples were analyzed for VAHs and PAHs(11).

Subsurface samples taken from around the pits indicate contamination may extend about 20' to 25' north and/or south of several of the pit boundaries, and possibly 35' to 40' away from pits 2F and 2E boundaries. Woodward-Clyde reported that phenanthrene, pyrene, naphthalene, and fluoranthene were commonly found. Analysis and interpretation of the results from Woodward-Clyde's investigations are somewhat unclear because of the spacing of borings and undefined location of actual pit boundaries. Information reviewed also indicates some of the samples could have been mislabeled(11,12).

Woodward-Clyde reported having to stop drilling at a depth of 24' for a boring between pits 2E and 2F because field measurements noted a high concentration of VAHs in the work area of the drilling crew. Samples from this boring were not analyzed for VAHs. Samples from a nearby boring located 33' south of pit 2F showed 1800 ppm benzene and 1900 ppm ethylbenzene. In their review of Woodward-Clyde's investigations, Dames and Moore noted that an underground petroleum pipeline right-of-way runs close by and possibly could be a contributing source of benzene and ethylbenzene(12).

Soil Gas

In 1984, Dames and Moore used a downhole emission chamber and realtime gas analyzers to conduct subsurface soil gas measurements during borings of the waste and soil in ponds 1B and 1C and pits 2B, 2C, and 2E. Gas samples were also collected in canisters and analyzed. Laboratory analysis of downhole gas samples taken at depths from 7.5' to 30' showed VAHs, mainly benzene, to be the primary substance in the organic gases collected. Soil gas samples from pits 2B, 2C, and 2E appeared to have higher emission rates as well as higher levels of total VAHs than samples taken from ponds 1B and 1C. Samples taken at 10' and 12.5' showed the highest levels of total VAHs (31,300 and 48,500 ppm respectively). High soil sample concentrations of VAHs such as benzene were also found at similar depths (see Table 3).

Table 2.

Maximum Concentrations of Contaminants in On-Site Subsurface Soil/Waste: Waste Ponds 1B and 1C
Contaminant Maximum Concentration (ppm) Depth (feet) Comparison Value
ppm Source
Benzene 450 45 24 CREG
Ethylbenzene 3500 7.5 200 NREG
Toluene 570 7.5 400 NREG
Xylene 520 7.5 4,000 NREG
1,1'-Biphenyl 310 7.5 100 NREG
Acenaphthylene/
Acenaphthene (1)
4,400 7.5 120(2) NREG(2)
Benzo(b)fluoranthene/
Benzo(k)fluoranthene/
Benzo(a)pyrene (1)
3,500 5 0.12(3) CREG(3)
Chrysene 770 5 NA NA
Dibenzo(a,h)anthracene/
Indeno(1,2,3,-cd)pyrene/
Benzo(g,h,i)perylene (1)
1,110 5 NA NA
Fluoranthene/Pyrene/
Benzo(a)anthracene (1)
8,100 7.5 80(4)
60(5)
NREG(4)
NREG(5)
Fluorene 660 7.5 80 NREG
1-H-Indene 740 7.5 NA NA
Methylnaphthalene 1,160 7.5 NA NA
Naphthalene 5,800 15 8 NREG
Phenanthrene/
Anthracene (1)
3,900 7.5 600(6) NREG(6)
Styrene 1,400 7.5 400 NREG
Arsenic 25 NA 0.6 NREG
Barium 180 35 140 NREG
Cadmium 8.6 20 0.4 EMEG
Chromium (7) 1,700 7.5 10-VI
2000-III
NREG
Copper 75 7.5 NA NA
Lead 40 7.5 NA NA
Nickel 58 7.5 40 NREG
Zinc 630 7.5 NA NA

NA = Not Available
Source: Reference 6.
(1) Concentrations only reported collectively.
(2) Value for acenaphthene; comparison value not available for acenaphthylene.
(3) Value for benzo (a) pyrene; comparison value not available for benzo (b) flouranthene or o (k) flouranthene.
(4) Value for flouranthene.
(5) Value for pyrene; comparison value not available for benzo (a) anthracene.
(6) Value for anthracene; comparison value not available for phenanthrene.
(7) Comparison values reported for chromium (VI) and chromium (III).

During their soil investigations in 1987, Woodward-Clyde installed soil gas probes in 23 locations around pits 2A through 2F. Gas samples were collected at 4, 8, 12, and 16 foot depths and analyzed in the field using a gas chromatograph. Results show benzene, ethylbenzene, toluene, and xylene detected at only two locations for all depths tested. The highest concentrations were seen at the lowest depth. The probes may not have penetrated deeply enough to be able to provide adequate information about soil gas migration(11,12).

Ambient Air

In 1983, Wilson Environmental Associates designed a 12-day air monitoring program as part of an overall worker safety health plan prepared for waste pond 1A excavation activities which were overseen by DTSC. A portable organic vapor analyzer (OVA) measured only total hydrocarbons along the perimeter of pond 1A and in the excavation area itself. Naphthalene was used as the reference gas, with total hydrocarbons assumed to be all naphthalene. No air quality measurements were taken off-site, and no analysis for metals or other particulates in the air were done. The data indicate excavation activities resulted in air releases of total hydrocarbons, with higher values from the excavation area as compared to the perimeter (2-35 ppm at the excavation, 1-5 ppm at the perimeter). Reports maintained by Wilson indicate no occupational health violations occurred and no odor or fugitive dust nuisances were recorded by the excavation workers. However, nearby residents registered odor complaints with DTSC staff during excavation of waste pond 1A(12).

In 1984, Dames and Moore investigated the impact of the Del Amo site on ambient air during undisturbed conditions and during drilling activities. The investigations included an undisturbed surface soil gas emission survey, a disturbed soil gas emission survey, and an upwind/downwind ambient air monitoring survey. No information on metals or particulates in air was gathered during any of the surveys.

For the undisturbed surface soil gas emission survey, Dames and Moore used HNu and OVA monitors to measure total concentrations of hydrocarbons and sulfur dioxide releases from samples taken on-site in the waste disposal area and samples taken at background locations noted to be away from the site. Surface soil gas flux measurements were also taken using isolation chambers to quantify soil gas emission rates. The limited data available from these sampling events indicate results for on-site and background samples did not appear to differ. The average hydrocarbon surface concentration on-site was 0.26 ppm as compared to 0.23 ppm for background(6). Background and site release for sulfur dioxide were not different (0.02 ppm)(6,12). However, in reviewing Dames and Moore's data, Woodward-Clyde noted that the testing methods used and equipment problems could have led to low readings(27). Dames and Moore also noted the data could not be used to draw conclusions about what impact the site in its undisturbed state might have on the area's ambient air(12).

The disturbed soil vapor emission survey included downhole sampling during soil boring activities described previously under Soil Gas. The results suggest that air emissions increased during disturbed soil conditions such as drilling at pits 2A through 2F(6).

Table 3.

Maximum Concentrations of Contaminant in On-Site Subsurface Soil/Waste: Waste Pits 2A through 2F
Contaminant Maximum Concentration (ppm) Depth (feet) Comparison Value
ppm Source
Benzene 66,000 15 24 CREG
Ethylbenzene 50,000 15 200 NREG
Toluene 940 15 400 NREG
Xylene 8,500 15 4,000 NREG
1,1'-Biphenyl 41 15 100 NREG
Acenaphthylene/
Acenaphthene (1)
9,900 12.5 120(2) NREG(2)
Benzo(b)fluoranthene/
Benzo(k)fluoranthene/
Benzo(a)pyrene (1)
19,000 7.5 0.12(3) CREG(3)
Chrysene 769 15 NA NA
Dibenzo(a,h)anthracene/
Indeno(1,2,3,-cd)pyrene/
Benzo(g,h,i)perylene (1)
2,100 7.5 NA NA
Fluoranthene/Pyrene/
Benzo(a)anthracene (1)
2,400 7.5 80(4)
60(5)
NREG(4)
NREG(5)
Fluorene 380 35 80 NREG
1-H-Indene ND 15 & 35 NA NA
Methylnaphthalene ND 15 & 35 NA NA
Naphthalene 409 15 8 NREG
Phenanthrene/
Anthracene (1)
360 7.5 600(6) NREG(6)
Styrene 1,200 35 400 NREG
Arsenic 25 15 0.6 NREG
Barium 250 15 140 NREG
Cadmium 12 15 0.4. EMEG
Chromium (7) 170 15 10-VIII
2000-III
NREG
Copper 29 15 NA NA
Lead 34 15 NA NA
Nickel 25 15 40 NREG
Zinc 240 15 NA NA

NA = Not Available
Source: Reference 6.
(1) Concentrations only reported collectively.
(2) Value for acenaphthene; comparison value not available for acenaphthylene.
(3) Value for benzo(a)pyrene; comparison values not available for benzo(b)fluoranthene or benzo(k)fluoranthene.
(4) Value for fluoranthene.
(5) Value for pyrene; comparison value not available for benzo(a)anthracene.
(6) Value for anthracene; comparison value not available for phenanthrene.
(7) Comparison values reported for chromium(IV) and chromium(III).

Upwind and downwind monitoring of ambient air was also done during the 1984 soil boring activities for waste pits 2A through 2F using portable realtime analyzers. Field notes indicate the wind mainly came from the west during the monitoring. Dames and Moore did not specify the upwind monitoring location, although the downwind location was noted to have been 130' east. Results for the 11 day survey show upwind or background total hydrocarbon concentrations averaged 0.47 ppm (range 0.08 to 2.20 ppm) as compared to 0.84 ppm (range of 0.12 to 6.80 ppm) for the downwind concentrations. Analyses of two grab samples taken on only one day of the survey showed an increase in air contamination over the site during drilling activities (upwind- 0.21 ppm, downwind - 0.44 ppm total hydrocarbons, collected 130' downwind)(6,12). Analyses of the grab samples for specific volatile aromatic hydrocarbons show that in both the downwind and upwind samples benzene levels exceeded health comparison values (see Table 4). No analyses for specific PAH compounds, metals, or particulates were included.

In 1985, DTSC used a dispersion model to assess the impact to ambient air of pond 1A as an open area after excavation activities were completed. Using concentrations reported for post excavation soil samples and available volatility and soil characteristics data, the findings from this model indicated minimal ambient air impact would occur and that emissions would be even lower if the pond were covered with clean soil(10).

Table 4:

Contaminants in Ambient Air Samples Taken During Soil Boring Activities
Contaminant Maximum Concentration (ppm) Downwind Maximum Concentration (ppm) Upwind (Background) Comparison Value (ppm) Comparison Value Source
Benzene 0.1443 0.03 0.000038 CREG
Ethylbenzene 0.0117 0.0009 0.3 EMEG
Styrene 0.0062 0.0019 NA NA
Toluene 0.0117 0.0009 1 EMEG

Source: reference 12.
NA = Not Available

Groundwater: Monitoring Wells

There are a total of six on-site monitoring wells which draw water from the Bellflower aquitard. This aquitard is the uppermost water bearing unit under the site, lying about 60' below ground surface (bgs). In 1984, Dames and Moore drilled and sampled 3 monitoring wells (DM-1, DM-2 and DM-3) around the waste disposal area. In 1987, Woodward-Clyde installed another on-site monitoring well (P-2) in the Bellflower aquitard and sampled all the monitoring wells. In 1988, EPA's contractor Ecology and Environment, Inc. (E&E), sampled all the wells. Dames and Moore received duplicate samples from E&E and had them analyzed separately(12). Additionally, in 1990, Montrose's contractor, Hargis and Associates, installed two monitoring wells (MW-20 and MW-21) on the Del Amo site further north (and hydraulically upgradient) of the other wells in order to characterize groundwater contaminants related to the neighboring Montrose site(4). Figure 3 (see Appendix A) shows location of the monitoring wells.

Table 5 presents maximum concentrations detected in the on-site wells located near the waste disposal area, which were sampled by Dames and Moore, Woodward-Clyde, and E&E. Also included are concentrations reported by Hargis and Associates for benzene and ethylbenzene found in MW-20 and MW-21 during an April 1990 sampling event. Only a few PAHs were included in the different groundwater analyses conducted. For metals, only arsenic, barium, copper, lead, and nickel were detected.

As reported by Woodward-Clyde, Dames and Moore, and EPA, benzene is the main contaminant detected in shallow groundwater samples taken from on-site monitoring wells. The highest benzene concentrations were reported in wells hydraulically upgradient of the waste ponds and pits with respect to groundwater flow direction (Wells DM-1, DM-2, P-2, MW-20, MW-21). Wells DM-1 and DM-2 located just north of the waste pond area showed 380,000 ppb and 150,000 ppb benzene respectively(15). MW-20, located upgradient from these two wells showed 1,100,000 ppb benzene contained in a floating layer observed in the well in April 1990(4). Well DM-3 located immediately downgradient from the waste disposal area showed 7,500 ppb benzene(15). Information we reviewed did not indicate the depths at which the different wells are screened. Being screened at different levels of the Bellflower aquitard may account for the different contaminant concentrations in the various wells. A well screened below the floating layer would probably not show as high levels.

The former rubber manufacturing plants located north of the waste ponds and pits may account for part of the present distribution of contaminants. As discussed previously, the handling and storage practices of raw materials, by-products, and wastes, as well as the extensive underground pipelines and storage tanks related to the former rubber manufacturing facilities may also account for the distribution of contaminants. Other sources of groundwater contamination may be found as the rest of the 280-acre site is characterized. In 1990, Hargis and Associates installed one monitoring well (LW3) in the Lynwood aquifer near MW-20 and MW-21. No contaminants have been detected in this well. There are no on-site monitoring wells screened in the Silverado aquifer.

TABLE 5.

Contaminants in On-Site Groundwater Monitoring Wells
Contaminant Concentration (ppb) Comparison Value
1984
Dames & Moore
1987
Woodward-Clyde
1988
Dames & Moore
1988
E & E
1990(1)
Hargis & Associates
ppb Source
Benzene 750,000 1,600,000(2) 400,000 380,000 1,100,000 1.2 CREG
Ethylbenzene 4,000 ND NT NT 46.000 1,000 NREG
Toluene 2,600 300 <50,000 5,500 NA 2,000 NREG
Xylene NT ND NT ND NA 20,000 NREG
Acenaphthalene 220 7.3 NT 23 NA NA NA
Acenaphthene 40 NT NT NT NA 600 NREG
Fluorene 20 NT NT ND NA 400 NREG
Phenanthrene/
Anthracene(3)
64 NT NT ND NA 3000(4) NREG
Benzo(k)fluoranthene NT 1.3 NT NT NT 0 PMCLG
Chrysene/(3)
Benzo(a)anthracene
18 NT NT NT NA 0(5) PMCLG
Naphthalene 42 66 NT 35 NA 20 LTHA
Arsenic 0.009 NT NT 23 NA 3 NREG
Barium .13 NT NT 133 NA 700 NREG
Chromium ND NT NT ND NA 50-VI(6)
10,000-II
NREG
Copper 0.64 NT NT 3.5 NA 13,000 PMCLG
Lead ND NT NT 2.4 NA 0 PMCLG
Nickel ND NT NT ND NA 100 PMCLG
Zinc 0.045 NT NT 146 NA 2000 LTHA

Source: References 4,6,11,12,15,47
NT = not tested; ND=Not detected; NA=not available.
(1) From MW 20 and MW 21, upgradient from waste disposal area.
(2) Duplicate sample for same well measured 380,000 ppb.
(3) Reported collectively.
(4) NREG for anthracene, NA for phenanthrene.
(5) Value both for chrysene & benzo(a)anthracene.
(6) Values for hexavalent chromium (chromium IV) & trivalent chromium (chromium III).

C. OFF-SITE CONTAMINATION

Soil (0-3') from Residential Backyards

In response to community concerns, DTSC took soil samples in 1983 from nine houses whose backyards bordered Del Amo Boulevard immediately across from the waste disposal area. For background comparison, samples were also taken from the yard of a house located 2 miles south of the site. Laboratory reports indicate corehole samples were taken from each yard, at 0-1' and 2'-3' levels for each corehole(29). A total of 20 samples were collected and analyzed for metals, volatile organic compounds, PAHs, and pesticides. Results show no VAHs were detected above the detection limit of 0.002 ppm. The PAHs naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, chrysene, and 1,2-benzanthracene included in the analyses were not detected above the detection limit of 0.005 ppm(30). In general, the samples taken between 2' to 3' deep had lower levels of metals than the 0-1' samples; the levels were generally similar to those reported for the background sample. As shown in Table 6, several heavy metals were detected at levels above health comparison values in the 0-1' samples.

Table 6.

Range of Contaminant Concentrations in Soil Samples from Off-site Residential Backyards (0-1')
Contaminant Concentration (ppm) Background Sample Concentration (ppm) Comparison Value (ppm) Comparison Value Source
Arsenic 4.5 - 19.4 5.8 0.6 NREG
Barium 71.2 - 219 51.0 140 NREG
Cadmium 0.9 - 6.7 0.9 0.4 EMEG
Chromium 14 - 514 12.6 VI - 10
III- 2000
NREG
Copper 15.7 - 110 12.3 NA NA
Lead 20.7 - 88.1 16.4 NA NA
Nickel 5.1 - 240 3.5 40 NREG
Zinc 38.4 - 135 102 NA NA

Source: Reference 30.

Soil Gas in Residential Areas

In March and April, 1991, DTSC collected soil gas samples from the unpaved Del Amo Boulevard due to odor complaints from residents(7). Based on DTSC's preliminary review of the data, DTSC staff have indicated there does not appear to be off-site migration of soil gases from the waste pits.

Groundwater - Monitoring Wells

Currently there are 9 off-site monitoring wells (see Figure 3, see Appendix A) related to the Del Amo site, but no regular sampling of these wells currently occurs. Three of the wells are screened in the Bellflower aquitard (P-3, P-1, and DA-1C), four in the Gage aquifer (G-1, G-2, DA-1B, and DA-2B), and two in the Lynwood aquifer (DA-1A and DA-2A). Woodward Clyde installed and sampled P-1, P-3, G-1, and G-2 during their 1987 investigations(11). EPA's contractor, E&E, installed wells DA-1, DA-1A, DA-1B, DA-2A, and DA-2B in 1988. The off-site wells are primarily located downgradient (south/southeast) from the waste disposal area in the residential area south of the site. Wells DA-1, DA-1A, and DA-1B are about a quarter mile southeast of the site. Wells DA-2A and DA-2B lie about 2 miles southwest of the waste disposal area. (Figure 3 see Appendix A).

Well boring logs for well DA-2A show that the aquitard which normally separates the Gage and Lynwood aquifers is absent and the Gage, Lynwood, and Silverado aquifers are interconnected at that location(15). At the location of well DA-1A, well boring logs show the Gage aquifer is separated from the deeper Lynwood and Silverado aquifers by a 50 foot deep layer of clay. The Silverado aquifer serves as the primary drinking water aquifer for the area.

E&E sampled all the wells during their 1988 investigations to determine if contaminants had migrated to deeper water bearing units(15). Groundwater samples were analyzed for metals, pesticides, polychlorinated biphenyls, and volatile and semivolatile organic compounds which included fluorene, phenanthrene, naphthalene, and 2-methylnaphthalene. With the exception of well P-1 which is screened in the Bellflower aquitard, none of the off-site wells showed detectable levels for the substances tested. Dames and Moore received duplicates of the samples taken by E&E and had them analyzed separately. In their analyses, benzene was not detected in any of the samples from off-site wells except for well P-1(12).

Table 7 shows levels of contaminants detected in well P-1 by Woodward-Clyde in 1987 and E&E in 1988. Woodward Clyde's analysis reflects the presence in well P-1 of a floating layer of a light nonaqueous phase liquid consisting primarily of petroleum hydrocarbons, mainly benzene, ethylbenzene, toluene, and xylene. Chlorobenzene was also detected in the groundwater but not in the limited soil/waste samples taken by Dames and Moore(12). Its presence may reflect contamination from other sources.

Woodward Clyde discovered the floating layer in well P-1 during its 1987 sampling and measured its thickness in the well to be about 12'. In 1988, Dames and Moore measured the thickness to be 14'. The areal extent of the floating layer is currently unknown. Other monitoring wells have not shown the presence of the floating layer, but they may have been screened more deeply(3). The source of the floating layer is not known. Well P-1 is located in the residential area south of Del Amo Boulevard within 300' of a petroleum pipeline corridor running along Del Amo Boulevard. Dames and Moore is currently conducting an investigation aimed at determining the source of the petroleum observed in well P1. EPA has contacted the pipeline companies who have indicated they were not aware of any past pipeline leaks.

Table 7.

Contaminants in Off-Site Groundwater Monitoring Well P1
Contaminant Concentration (ppb) Comparison Value
1987
Woodward-Clyde1
1989
Ecology andEnvironment
1988
Dames &Moore
Value (ppb) Source
Benzene 700,000 520 920,000 1.2 CREG
Chlorobenzene 300,000 NT NT 200 NREG
Ethylbenzene 300,000 NT NT 1000 NREG
Toluene 1,100,000 ND 1,100,000 2,000 NREG
Xylene (Total) 140,000 570 NT 20,000 NREG
Methylnaphthalene NT 3,500 NT NA NA
Naphthalene NT 2,200 NT 20 LTHA
Fluorene NT 360 NT 400 NREG
Phenanthrene NT 710 NT 0 PMCLG

Source: Reference 11,12,15
ND=not detected; NT=not tested

(1) Woodward-Clyde's analysis reflects floating layer of a light non-aqueous phase liquid.

A number of other monitoring wells associated with different facilities exist within one mile from the Del Amo site. As part of remedial investigation activities for the neighboring Montrose site, Hargis and Associates has conducted extensive groundwater sampling of a number of these wells which are screened in the Bellflower aquitard or the Gage aquifer. Contaminants reported to be present in some of these wells included chlorobenzene, dichlorobenzene, benzene, chloroform, ethylbenzene, phenol, and diesel fuel(28). For well P-3, which is located immediately downgradient from the waste disposal area, sampling results reported for August 1990 show nondetectable levels for all compounds tested. However, Hargis and Associates reported that wells located further south of well P-1 showed benzene and ethylbenzene in both the Bellflower aquitard and the Gage aquifer. Based on the information which we reviewed, the nature of commingling of the groundwater plumes in the area cannot currently be defined. However, EPA confirms that available data indicate the contaminated ground water plume from Montrose and Del Amo have merged within parts of the Bellflower aquitard and possibly the Gage Aquifer.

Groundwater - Municipal Wells

No contamination has been detected in nearby municipal wells, which are shown in the inset in the inset in Figure 3 (see Appendix A)(1). However, municipal wells in the immediate area draw from the deeper Lynwood and Silverado aquifers which appear to interconnect with the Gage aquifer about 2 miles southwest of the site. In 1990, E&E identified six functioning municipal wells drawing from the deeper aquifers within a 4 mile radius of the Del Amo site. A seventh well, well 19, was recently replaced by well 19A due to problems with the well casing(31). Wells 19A, 79, and 75A all belong to Dominguez Water Corporation and are located downgradient (southeast) from the site, with well 19A being the closest (about 2 miles away). These 3 wells supply about 25% of the local water supply and serve about 10,000 people(15).

Three other municipal wells, known as City of Torrance wells 4, 5, and 6, are located about 2 miles west of the site. In drilling the two off-site monitoring wells DA-2A and DA-2B, which are located within a half mile south of wells #4 and #5, E&E documented that the Gage, Lynwood, and Silverado aquifers merge together. The City of Torrance wells draw water from the deeper aquifers to supply about 12% of the total water supply for the city, serving about 25,000-30,000 people(15).

In 1983, neighboring residents requested sampling of their tap water to see if any contaminants were in their drinking water. The Los Angeles County Public Health Department collected tap water samples from four houses receiving water from Dominguez Water Corporation and samples from Well 19 for analysis. No hazardous contaminants were reportedly detected in the samples(32). Samples analyzed in September 1991 from Well 19A, which has replaced Well 19, have not shown the presence of any contaminants(31).

Groundwater - Private Wells

E&E identified four private wells within a four mile radius of the site(1). These wells are used for commercial/industrial or nursery irrigation purposes. No other information is available about these wells.

D. QUALITY ASSURANCE AND QUALITY CONTROL

We reviewed the Quality Assurance Review for the Hazard Ranking System Documentation and the Quality Assurance/Quality Control (QA/QC) summary for groundwater data collected by E&E for the CERCLA Expanded Site Inspection. No analytical problems were noted.

We did not review QA/QC information for data collected and reported by Dames and Moore and Woodward-Clyde. We assume the data passed DTSC's QA/QC review. However, in their review of Dames and Moore's air data, Woodward-Clyde noted some methodological and equipment problems which could have led to low readings. Also Dames and Moore reported that Woodward-Clyde may have mislabeled soil/waste samples.

In preparing this preliminary public health assessment, CDHS and ATSDR generally rely on the information provided in the referenced documents. Unless otherwise noted, we assume that adequate quality assurance and quality control measures were followed with regard to chain-of-custody, laboratory procedures, and data reporting. The validity of the analysis and conclusions drawn for this health assessment are determined by the completeness and reliability of the referenced information.

E. PHYSICAL AND OTHER HAZARDS

The 280-acre site currently serves as an industrial park with a number of businesses on it. The former waste disposal area is fenced, but as described under Site Visit, someone could enter through an opening in the locked gates and gain access to the area. Also, the unpaved part of Del Amo Boulevard which borders the southern boundary of the site presents physical hazards. We noticed ruts in the road, piles of garbage and refuse, abandoned cars, and a strong sewage type smell, and observed people and moving vehicles in the alley.


PATHWAYS ANALYSES

To determine whether nearby residents and workers in the surrounding area are exposed to contaminants migrating from the site, CDHS and ATSDR evaluate the environmental and human components that lead to human exposure. This pathways analysis consists of five elements: 1) a source of contamination; 2) transport through an environmental medium (such as air or soil); 3) a point of human contact with the contaminated medium (known as the exposure point); 4) a route of human exposure (such as inhalation or ingestion); and 5) an exposed population.

CDHS and ATSDR categorize an exposure pathway as a completed or potential exposure pathway if the exposure pathway cannot be eliminated. In completed exposure pathways, each of the five elements exists and indicates that exposure to a contaminant has occurred in the past, is occurring, or will occur in the future. In potential exposure pathways, however, at least one of the five elements is missing but could exist. An exposure pathway may also be considered as potential if it is indeterminate due to lack of information. Potential exposure pathways indicate that exposure to a contaminant could have occurred in the past, could be occurring now, or could occur in the future. An exposure pathway can be eliminated if at least one of the five elements is missing and will never be present. Table 8 identifies the completed exposure pathways, and Table 9 identifies the potential exposure pathways. The discussion that follows these tables only covers those pathways that are important and relevant to the site. The toxicological implications of the various pathways identified as being of concern are evaluated in the Public Health Implications section.

A. COMPLETED EXPOSURE PATHWAYS

As shown in Table 8, existing information for the Del Amo site indicates a completed exposure pathway, through inhalation of contaminated ambient air, exists by which site-related contaminants may impact people in the surrounding area.

Ambient Air

Past exposure has occurred and present and future exposures to VAHs and PAHs may occur to residents and workers in the area surrounding the site. The VAHs, mainly benzene, ethylbenzene, xylene, and toluene, migrate from contaminated soil or groundwater as soil gases and evaporate or volatilize readily into the air where they are inhaled. In contrast, the PAHs such as benzo(a)pyrene, anthracene, and chrysene, adhere to particulates such as dust or soil, become airborne, and then are inhaled or ingested. The contaminated airborne particulates can settle in yards or homes where people can also come into direct skin contact with them. Although the release of VAHs and PAHs to the atmosphere is assumed because of odor complaints of nearby residents during excavation of waste pond 1A, off-site air monitoring or house dust data are not available to determine the levels of contaminants the site may have or now be contributing to the area.

In addition to the former waste disposal area, other possible non-site related sources of contaminants such as benzene, ethylbenzene, toluene, and xylene include vehicular emissions, petroleum pipelines and refineries, and commercial businesses and industries in the area such as those reported in the Toxic Chemical Release Inventory (see Environmental Contamination and Other Hazards section). The site is located near two major freeways; therefore, vehicular traffic contributes to the ambient air contamination of the area. Pipelines and underground storage tanks, which may release volatile contaminants, related to the former rubber manufacturing facility may still remain on parts of the 280-acre site. Other pipelines are likely in the area and could leak at some time. Several other industries in the area report releases of the same types of contaminants found at the site, thereby contributing to the ambient air contamination. Those people who work or play outdoors a large part of the time experience the highest levels of exposure. However, volatile contaminants in ambient outdoor air can also affect indoor air quality.

In general, current background air data are lacking that indicate "typical" contaminant levels for the area near the site. However, in 1987, the South Coast Air Quality Management District issued a report noting that ambient air in the Los Angeles area contained a number of organic gases, including benzene and particulates such as metals, at levels which could contribute to adverse health effects(34). The California Air Resources Board has an air monitoring station in Long Beach, about 10 miles southeast of the Del Amo site. The station is away from industrial and vehicular sources of air contamination. During 1990, the concentrations of benzene in air samples taken from the Long Beach station ranged from 0.0014 to 0.011 ppm. Ethylbenzene ranged from less that 0.0006 to 0.0017 ppm, toluene from 0.0025 to 0.029 ppm, xylene from 0.0012 to 0.0094 ppm, and styrene from 0.0002 to 0.0016 ppm(35).

As described in the Environmental Contamination and Other Hazards section, a downwind air sample taken during 1984 soil boring activities at the site showed an increase of VAHs as compared to an upwind, or background, sample. Analysis for specific compounds of the one gas sample taken showed benzene levels to be above health comparison values in both the upwind and downwind samples. As compared to the 1990 Long Beach data, the downwind sample had higher levels of benzene, ethylbenzene, and styrene. The upwind sample also showed higher levels of benzene and styrene, but not ethylbenzene and toluene. Records regarding excavation of pond 1A also indicate an increased release of hydrocarbons during excavation. Although no off-site air measurements were taken at the time, residents complained about odors during that excavation.

From the 1940s to the mid 1960s, during the time the rubber manufacturing facilities were operating and the pits and ponds were in use and uncovered, air releases from the deposited waste materials and plants probably occurred. However, no data exist to evaluate past exposures to the contaminants. Adequate data on possible current releases do not exist. Dames and Moore indicate that, through measurements they have taken, there are not likely to be significant air releases as the site stands now. However, measurements may not have been correctly taken(11,12). Equipment problems and incorrect techniques could have affected the accuracy of the measurements.

Table 8:

Completed Exposure Pathways
Pathway Name Exposure Pathways Elements Time Frame
Source Environmental Medium Exposure Point Exposure Route Exposed Population
Ambient Air 3.7-acre waste disposal area

Vehicular traffic

Commercial/industrial businesses in the area

Ambient Air Surrounding areas, including residential and business areas

Businesses in the area

Inhalation Residents and workers in the surrounding area Past

Table 9:

Potential Exposure Pathways
Pathway Name Exposure Pathways Elements Time Frame
Source Environmental Medium Exposure Point Exposure Route Exposed Population
Indoor Air Contaminated groundwater

Contaminated subsurface soil

Contaminated ambient air

Indoor Air Residences

Commercial/industrial facilities

Inhalation Residents and workers in the surrounding community Past
Present
Future
Soil (surface and subsurface) Waste disposal areas Soil (surface and subsurface) Residential areas

Businesses in the area

Unpaved Del Amo Boulevard

Ingestion

Inhalation

Skin contact

Residents

Commercial/industrial workers

Remedial workers

Trespassers

Past
Present
Future
Municipal Wells Contaminated drinking water aquifers (Lynwood/ Silverado) Groundwater Residences

Businesses

Ingestion
Skin contact
Inhalation
Users of local water supplies - residents and workers in the area Present
Future

B. POTENTIAL EXPOSURE PATHWAYS

Table 9 shows potential exposure pathways which may exist. The discussions that follow explain in detail how exposures may occur.

Indoor Air

The quality of indoor air can be affected by contaminants in ambient air and also in soil gas. No data currently exist to show whether or not soil gas containing VAHs like benzene is being released into houses or other structures from underlying contaminated groundwater or soil. The floating layer found in an off-site monitoring well screened in the most shallow aquifer underlying the residential area south of the site contained high levels (700,000-920,000 ppb) of benzene. The well was last sampled in 1988; how deep and how far this floating layer extends into the residential area is presently unknown. An on-site well located upgradient from the waste disposal area also showed a floating layer containing 1,100,000 ppb benzene. Benzene was also detected in soil gas samples taken around the waste disposal area. Petroleum pipelines in the area may also be sources of soil gas containing VAHs.

Depending on subsurface conditions such as soil density and composition, transport of soil gas could occur through soil and could be released at the surface. Releases could be to the ambient air or contaminated soil gas could enter confined spaces within buildings and houses through crawl spaces, cracks in the foundation, or through openings for utility or plumbing pipelines, and accumulate indoors. Residents and workers could be exposed through inhalation to contaminants contained in the indoor air.

In 1985, Woodward-Clyde identified subsurface migration of soil gas as possibly being a significant route of exposure to residents in the surrounding community. They also stated that during rainy periods, which could cause a decrease in surface permeability, any existing subsurface migration could be enhanced. Rain could increase movement of volatile compounds into dry soil which may exist underneath houses and other structures. Residents have noted odors present after rainy periods(7).

Soil

Past, current, and future exposure pathways involving contaminated soil are possible at several areas: residential yards and businesses in the surrounding area, the unpaved Del Amo Boulevard area, and the waste disposal area itself. Contaminated surface soil or subsurface soil on the site exposed through excavation activities can be transported by wind, surface water runoff, and fugitive dust from vehicular traffic to areas of human contact.

Skin contact, inhalation of soil dust, and incidental soil ingestion are likely routes of exposure for people to contaminated soil. Incidental soil ingestion is likely if a person eats, drinks, smokes, or participates in recreational or occupational activities near soil containing contaminants. For residential yards and recreation areas, soil ingestion can be an important route of exposure, especially for children less than 6 years of age(33). Soil ingestion is greater for young children because of their greater hand-to-mouth activity. Young children typically ingest about 200 milligrams (mg) soil per day while adults and older children ingest less than 100 mg per day. Children who have pica behavior, a tendency to eat non-food items such as dirt, may ingest up to 5,000 mg per day.

Polycyclic aromatic hydrocarbon compounds (PAH's) such as those found in the waste pits and ponds strongly adsorb to soil. During past excavation activities, contaminated soil and dust could have been airborne and deposited in residential yards or other surrounding areas. Any contaminants present near the surface of the waste disposal area could also migrate by wind or surface water runoff to areas of human contact. The waste pits and ponds were reportedly covered with soil in between 1969 and 1972, but in 1984, Dames and Moore noted that pond 1C had areas lacking soil cover, resulting in waste materials being exposed at the surface. Also information about the soil cover is not available. No surface soil (0-3") samples have been taken of the soil cover over the waste disposal area. The waste disposal area presently has grassy vegetation over most of it which helps to prevent surface soil from being blown or washed off, but a few bare areas are visible. With respect to the rest of the 280-acre site, much of the surface is paved or asphalted. However, several undeveloped lots of land with unrestricted access do exist on the site with areas of uncovered soil. No information currently exists about contamination of these areas.

Past, current, and future exposure pathways are possible for residents surrounding the site. About 26,000 people live within a one-mile radius of the site, with about 15,000 of them living one mile south. Surface soil runoff and wind dispersion of soil particles and dust could transfer contaminated soil to residential yards. Prevailing wind directions appear to vary in the area, sometimes blowing from the west, east, or north (see Natural Resource Use and Features section). For residents living in the surrounding areas, no off-site surface soil samples have been taken. For contaminants that may be present, the greatest exposure will likely be at or near the surface. Soil samples taken at depths greater than 3" may underestimate the actual concentrations that exist near the soil surface. In 1983 during excavation activities for waste pond 1A, soil samples were taken from 12" deep coreholes from 9 residential backyards across from the waste disposal area and one yard located 2 miles further south which was sampled for background comparison. Soil samples 0-12" deep taken in 10 residential yards south of the site may not adequately characterize surface soil contamination in the residential areas around the site. Analyses only showed the presence of several heavy metals at levels above health comparison values used to help select contaminants for further follow-up (see Environmental Contamination-Offsite section). For arsenic, barium, cadmium, copper, lead, and zinc, the reported levels were similar to the ones found in the background sample taken and also similar to levels reported for soil in the western United States.

Residents may also be exposed through food items that come into contact with contaminated soil. Soil can be deposited on vegetables and fruits grown in residential yards and inadvertently ingested. Plant uptake of contaminants such as some metals and PAHs may also be possible. For instance, PAHs can be absorbed in root crops with some oil content, such as carrots and onions. Free ranging chicken and other fowl who peck and scratch the ground surface for food may also ingest contaminated soil and have contaminants accumulate in their meat or eggs. People eating these fowl or their eggs may become exposed to soil contaminants through this route also. Some of the residents we spoke with said they eat home grown produce and/or the eggs and chickens they raised. Some also told us they had experienced some difficulties growing produce or raising chickens. No other information about these food items is available.

The unpaved Del Amo Boulevard area exists as a dirt alley between residential yards and the waste disposal area. No data exists to show evidence of surface or subsurface soil contamination in the dirt alley, but contaminated soil from the waste disposal area could easily migrate there through wind or surface water runoff during rainy periods. Access to the alley is unrestricted, and we observed children, adults, and vehicles traveling through the alley during our site visits.

Past, present, and future exposure of commercial, industrial and business workers in the surrounding area by way of incidental soil ingestion, inhalation, or skin contact is minimal for those workers who spend most of their work hours indoors. More than 35 businesses exist on-site and in the surrounding area. Although we contacted city and county planning departments, we were unable to get figures on the number of workers in the area. Most of the businesses operate north of the power right-of-way which lies about 200 feet north of the waste disposal area. Workers closest to the waste disposal area include employees of Western Waste Industries which occupy lots surrounding the former waste area to hold metal dumpsters.

Prior to 1983, the waste disposal area was unfenced. As reported by local residents, children often played there and could thus have experienced exposure to contaminants through skin contact, inhalation or ingestion. Two chainlink fences currently limit access to the former waste disposal area. However, as noted previously under Site Visit, trespassers could gain access through an opening in the locked outer fence gate or by crawling underneath the fence which is not secured at the bottom, and could get exposed to soil contaminants. In 1985, during one of their site visits, consultants from Woodward-Clyde noted that the outermost fence southwest of the site had been pushed over to let people and two-wheeled vehicles enter the adjoining lot. The fence enclosing the waste pit area had a large hole cut in it such that an adult could walk through or bring in a two-wheeled vehicle. The mound over pit 2F on the west end of the waste disposal area may have been attractive to people riding two wheeled vehicles like bicycles or motorcycles.

Remedial workers who participated in excavation activities for waste pond 1A may have experienced a past exposure to surface and subsurface contaminants unless preventive measures were taken. Future exposure of remedial workers involved with possible excavation and removal activities for the remaining waste ponds and pits could be minimized if they wear appropriate personal protective equipment and comply with applicable health and safety guidelines. If appropriate dust control measures are taken, future exposure of residents and workers in the surrounding community could also be minimized during excavation or other activities where the waste disposal area is disturbed.

Although residential development on the former waste disposal area or other parts of the 280- acre site is highly unlikely, future development of the contaminated waste disposal area for industrial use may occur since the rest of site serves as an industrial park. Deed and building restrictions to prevent development until contamination has been reduced to levels below health concern or to prevent contact with contaminants at points of exposure will decrease the likelihood of future exposure to construction workers as well as people in the surrounding community.

Groundwater

Although site-associated contaminants have been shown to be present in high concentrations in the uppermost Bellflower aquitard which underlies the site and surrounding areas, this groundwater does not serve as a source of water for the area. Municipal wells draw from the much deeper Silverado aquifer (over 500' below ground surface) for higher quality and yield.

Contaminants may have migrated from the Bellflower aquitard to the Gage aquifer which occurs about 200' below ground surface. In off-site monitoring wells screened in the Gage aquifer and sampled by Montrose's contractor, contaminants were found to be present. Contaminants may also migrate into the deeper aquifers. The Gage and the deeper Lynwood and Silverado aquifers merge about 2 miles southwest of the site, near known municipal wells. People receiving tap water from these deeper aquifers may be exposed to contaminants in the future. To date, no contamination has been detected in any of the municipal wells within a four-mile radius drawing from the deeper Lynwood/Silverado aquifers. Tap water samples taken in 1983 from four homes receiving water from the closest downgradient municipal well drawing from the Silverado aquifer showed no detectable levels of contamination either. Drinking water supplied to the 26,000 residents in the area consists of a blend of groundwater drawn from the deep Silverado aquifer and imported water from northern California and Arizona.

Additional monitoring of the Bellflower aquitard and Gage aquifer is needed in order to determine the current depth, extent, concentration, and thickness of contaminant layers present. Information from other monitoring wells in the area needs to be reviewed as well.

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