five-year review report for the mosley road sanitary landfill oklahoma city, oklahoma ... ·...

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FIVE-YEAR REVIEW REPORTFOR THE

MOSLEY ROAD SANITARY LANDFILLOKLAHOMA CITY,

OKLAHOMA COUNTY, OKLAHOMA

Prepared for:

WASTE MANAGEMENT OF OKLAHOMA, INC.3300 MOSLEY ROAD

OKLAHOMA CITY, OKLAHOMAand

U. S. ENVIRONMENTAL PROTECTION AGENCY

Date Prepared : September 27, 2000Prepared by : Tetra Tech EM Inc.Telephone No. : 214-754-8765

FIVE-YEAR REVIEW REPORTFOR THE

MOSLEY ROAD SANITARY LANDFILLOKLAHOMA CITY,

OKLAHOMA COUNTY, OKLAHOMA

This memorandum documents the U.S. Environmental Protection Agency’s (EPA) approval of theMosley Road Sanitary Landfill (MRSL) Five-Year Review Report prepared by Tetra Tech EM Inc.

Summary of Five-Year Review Findings

Data review indicates that the remedial action is protective of human health and the environment. Nostatistically significant exceedance of the baseline concentrations have occurred in the seven semiannualground water sampling events that have occurred since 1997. However, a trend of increasingconcentrations is becoming evident for barium in well MW12R and manganese in well MW201.

Actions Needed

Based on the review of the available information for this five-year review, the following actions areneeded: (1) surface water samples from Crutcho Creek should resume on an annual basis; (2) thelandfill cover system along the north face needs to be repaired; and (3) one of the monitoring well capsneeds repair.

Determinations

I have determined that the remedy for the MRSL site is protective of human health and the environment.

CONCURRENCESFIVE-YEAR REVIEW REPORT

MOSLEY ROAD SANITARY LANDFILLSUPERFUND SITE

OKLAHOMA CITY OKLAHOMA

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CONTENTS

Section Page

ACRONYMS AND ABBREVIATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

EXECUTIVE SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ES-1

1.0 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i

2.0 SITE CHRONOLOGY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

3.0 BACKGROUND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

3.1 PHYSICAL CHARACTERISTICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

4.0 REMEDIAL ACTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

4.1 REMEDIES SELECTED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84.2 REMEDY IMPLEMENTATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114.3 SYSTEM OPERATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

5.0 FIVE-YEAR REVIEW PROCESS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

6.0 FIVE-YEAR REVIEW FINDINGS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

6.1 INTERVIEWS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136.2 SITE INSPECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136.3 ARAR REVIEW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146.4 DATA REVIEW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

7.0 ASSESSMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

8.0 DEFICIENCIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

9.0 RECOMMENDATIONS AND FOLLOW-UP ACTIONS . . . . . . . . . . . . . . . . . . . . . . . 19

10.0 PROTECTIVENESS STATEMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

11.0 NEXT REVIEW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

12.0 OTHER COMMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Appendices

A DOCUMENTS REVIEWED

B SITE VISIT REPORT

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TABLES

Table Page

1 CHRONOLOGY OF SITE EVENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2 IDENTIFIED DEFICIENCIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

3 RECOMMENDATIONS AND FOLLOW-UP ACTIONS . . . . . . . . . . . . . . . . . . . . . . . 20

FIGURES

Figure Page

1 SITE LOCATION MAP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2 SITE VICINITY MAP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

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ACRONYMS AND ABBREVIATIONS

A-1 A-1 Sanitation Company, Inc.ARARs Applicable or relevant and appropriate requirementsCERCLA Comprehensive Environmental Response, Compensation, and Liability ActCFR Code of Federal RegulationsEORDF East Oak Recycling and Disposal FacilityEPA U.S. Environmental Protection AgencyGPM Gallons per minuteLGMS Landfill Gas Management SystemMCLs Maximum contaminant levelsmg/L Milligrams per liter or parts per million (ppm)MRSL Mosley Road Sanitary LandfillNCP National Oil and Hazardous Substances Pollution Contingency PlanNPL National Priorities ListO&M Operations and MaintenanceOCC Oklahoma County ClerkOCD Oklahoma City Disposal Inc.OSDH Oklahoma State Department of HealthOUs Operable unitsRA Remedial ActionRALs Risk action levelsRCRA Resource Conservation and Recovery ActRD Remedial DesignRI/FS Remedial investigation/feasibility studyROD Record Of DecisionSCA SCA Services Inc.SDWA Safe Drinking Water ActTetra Tech Tetra Tech EM Inc.UAO Unilateral Administrative OrderVOCs Volatile organic compoundsWMO Waste Management of Oklahoma, Inc.

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EXECUTIVE SUMMARY

Tetra Tech EM Inc. (Tetra Tech) was contracted by Waste Management of Oklahoma, Inc. (WMO)

to conduct this, the first five-year review for the Mosley Road Sanitary Landfill (MRSL or the Site)

located in Oklahoma City, Oklahoma County, Oklahoma. This report documents the methods, findings,

and conclusions of the review conducted from March to August 2000. The purpose of this five-year

review is to determine whether the remedy chosen for the Site is protective of human health and the

environment.

The Site consists of approximately 72 acres in a relatively undeveloped area between Oklahoma City

and Midwest City, Oklahoma County, Oklahoma (Figure 1). Located at 3300 Mosley Road, the Site

is bordered to the north and south by NE 36th and NE 23rd Streets, respectively; Mosley Road to the

west; and the Burlington Northern rail line to the east. The currently operating East Oak Recycling and

Disposal Facility is located across Mosley Road to the west of the Site.

MRSL was originally owned by Floyd Swen and was operated by the A-1 Sanitation Company (A-1).

A-1 conducted landfill operations under a permit from the Oklahoma State Department of Health

(OSDH) (now Oklahoma Department of Environmental Quality [ODEQ]) from June 1973 to 1975. In

1975, Oklahoma City Disposal Inc. (OCD) took over operations at MRSL. Between February 20,

1976, and August 24, 1976, OSDH authorized OCD to accept hazardous industrial wastes due to the

temporary closure of the Royal Hardage Landfill in Criner, Oklahoma, which had previously been

accepting such wastes. During those 6 months, approximately 1.7 million gallons of mostly liquid

industrial hazardous waste was deposited in three unlined pits, referred to as the waste pits, located

within the boundaries of what is now defined as the Mosley Road Landfill. In 1984, WMO acquired

the stock of SCA Services, which had OCD as a subsidiary, thus transferring the ownership and

operational responsibilities of MRSL to WMO. MRSL reached its permitted capacity in November

1987 and was closed after 16 years of operation. A compacted clay cover was installed in 1988, in

accordance with governing landfill regulations.

Although no release of contaminants to the ground water was documented, the disposal of hazardous

industrial wastes at the MRSL site in unlined pits presented a potential hazard to human health and the

environment due primarily to hazardous substances migrating into both the shallow and deep aquifers

that underlie the site-specifically the deeper Garber-Wellington aquifer, which is used as a source of


drinking water by surrounding communities. On June 24th, 1988, after the MRSL site was scored on

the Hazard Ranking System, the U.S. Environmental Protection Agency (EPA) proposed it for

inclusion on the National Priorities List (NPL). The MRSL. site was placed on the NPL on February

21, 1990.

Analysis of the data derived from the remedial investigation (RI) initiated in January 1990, indicated that

the shallow alluvial aquifer, and to some extent, the deeper Garber-Wellington aquifer, were adversely

impacted by the disposal of the hazardous material below grade in the waste pits. Surface water bodies

near the site were found to be impacted by discharges from sources located upstream of the landfill.

Based on available ground water data, it did not appear that surface water had been measurably

impacted by discharges of compounds transported by ground ,water from the landfill or waste pits.

The remedial action for the MRSL site was undertaken pursuant to the terms of a Unilateral

Administrative Order (UAO) issued by the EPA on January 28, 1994, which became effective

February 14, 1994. The UAO required the implementation of the selected remedy as described in the

1992 Record of Decision (ROD). Work on the Remedial Action (RA) commenced in early

February 1995, in accordance with the remedy stipulated in the ROD, with the installation of a 14-well,

ground water monitoring network. WMO initiated the ground and surface water monitoring program in

March 1995. Construction of the landfill gas management system and the MRSL cover remediation

continued through May 1996.

Institutional controls have been implemented by WMO in accordance with requirements set by EPA.

Land use restrictions are binding on all current and future owners of the property. These restrictions

prohibit domestic use of extracted water from onsite wells, installation of ground water wells onsite

other than those for remedial purposes, and the use of property for residential or agricultural purposes.

WMO also filed a deed notice informing prospective purchasers and users of the property that

institutional controls are in place.

The results of the applicable or relevant and appropriate requirements (ARAR) review determined that

no new chemical- or location-specific ARARs have been promulgated that could jeopardize the

protectiveness of the MRSL remedial action.

To date, no statistically derived contaminant concentration exceedances have occurred for any of the

six semiannual monitoring events. Therefore, contingency measures outlined in the ROD have not been


necessary. Both the site health and safety plan and site contingency plan are in place, are sufficient to

control risks, and are being properly implemented. Some minor erosion rutting has occurred on the

north face of the cap, but has not affected the performance or the integrity of the cover system.

Regrading and the continued application of strewn hay on the north face is required. The site continues

to prove effective at protecting human health and the environment. The remedial action is protective of

human health and the environment.


Five-Year Review Summary Form

Deficiencies:

Some minor erosion rutting has occurred on the north face of the cap, but has not affected theperformance or integrity of the cover system.

Recommendations and Follow-up Actions:

Current operation and maintenance (O&M) procedures in place and instituted by WMO personnel areeffective at validating the protectiveness provided by the remedy utilized at the MRSL site.

Continue application of strewn hay on the north face. Monitor erosion on the north face.

Protectiveness Statement(s):

The remedial action for the OU is protective, thus the remedy for the site is protective of human healthand the environment.

Other Comments:

None.

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1.0 INTRODUCTION

As required by statute, this, the first five-year review report for the Mosley Road Sanitary Landfill

(MRSL or the Site) Superfund Site is consistent with the requirements stipulated in the Comprehensive

Environmental Response, Compensation, and Liability Act (CERCLA) and the National Oil and

Hazardous Substances Pollution Contingency Plan (NCP). The specific goal of this five-year review is

to make a determination regarding the effectiveness of the Site’s remedy to protect human health and

the environment. The Site’s remedial action will leave hazardous substances, pollutants, or contaminants

at the Site above concentrations that preclude unrestricted use and unlimited exposure and the Record

of Decision (ROD) was signed after October 17, 1986. Therefore, the review of the Site’s

effectiveness at protecting human health and the environment is statutorily required every five years

subsequent to the triggering action date (typically the beginning of the remedial action [RA]

construction). Tetra Tech EM Inc. (Tetra Tech) was contracted by Waste Management of Oklahoma,

Inc. (WMO), the current owneroperator of MRSL, to conduct this five-year review of the effectiveness

of the remedies instituted during the RA.

2.0 SITE CHRONOLOGY

Table 1 lists the chronology of events for the MRSL site.

3.0 BACKGROUND

The following sections discuss the physical characteristics of the site, the land and resource use, and the

history of contamination.

3.1 PHYSICAL CHARACTERISTICS

Located at 3300 Mosley Road between NE 23rd and NE 36th Streets, the Mosley Site consists of

approximately 72 acres surrounded by predominantly undeveloped land between Oklahoma City and

Midwest City, Oklahoma County, Oklahoma (See Figure 1). The Mosley site is bordered to the west

by Mosley Road, which separates MRSL from the East Oak Recycling and Disposal Facility

(EORDF), which is also owned and operated by WMO. One half mile further west of the MRSL site is

the North

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TABLE 1

CHRONOLOGY OF SITE EVENTS

Date Event

June 1973 Permit to operate Mosley Road Sanitary Landfill (MRSL) site as a sanitarylandfill received from Oklahoma State Department of Health (OSDH).

February 20, 1976to August 24, 1976

MRSL authorized by OSDH to accept industrial hazardous wastes

November 1987 MRSL reached permitted capacity and was closed.

1988 Compacted clay cap cover installed over the landfill.

June 24, 1988 MRSL site proposed to the National Priorities List (NPL).

February 21, 1990 MRSL site added to NPL.

July 28, 1989 Waste Management of Oklahoma, Inc. (WMO) and Mobile Waste Controlsigned Administrative Order on consent requiring them to initiate remedialinvestigation (RI)/feasibility study (FS) at the site.

January 1990 Commencement of RI field work

August 1991 RI Completed

November 1991 FS completed

June 29, 1992 Record of Decision (ROD) signed.

January 28, 1994 Unilateral Administrative Order issued.Remedial design (RD) commences.

April 1, 1994 Deed restrictions filed with Oklahoma County Clerk (OCC).

May 12, 1994 Deed notice filed with OCC.

January 5, 1995 U.S. Environmental Protection Agency (EPA) approves the use ofconstruction debris as fill material for the landfill.

February 9, 1995 Installation of ground water monitoring wells commences.

February 25, 1995 Ground water monitoring well installations completed.

March 15, 1995 EPA approves the landfill gas management system (LGMS) design andwaives the requirement for a Remedial Action (RA) work plan (for the gasmonitoring component of the RA) to expedite construction.

August 24, 1995 Construction of LGMS commences.

November 6, 1995 EPA approves the RD and RA work plan.


TABLE 1 (Continued)

CHRONOLOGY OF SITE EVENTS

Date Event

February 21, 1996 Construction involving clay soil cover remediation, surface water drainage,and the access road commences.

May 24, 1996 Construction of clay soil cover, surface water drainage system, and accessroad completed

February 26, 1998 WMO begins plugging and abandonment of monitoring wells

July 21,1998 WMO completes plugging and abandonment of the monitoring wells andpiezometers which are not part of the ground water monitoring network

Notes:

EPA U.S. Environmental Protection AgencyLGMS Landfill Gas Management SystemMRSL Mosley Road Sanitary LandfillNPL National Priorities ListOCC Oklahoma County ClerkOSDH Oklahoma State Department of HealthRA Remedial ActionRD Remedial DesignRI/FS Remedial Investigation/Feasibility StudyROD Record of DecisionWMO Waste Management of Oklahoma, Inc.


Canadian River, a major perennial stream that flows from southwest to northeast. MRSL is bordered to

the east by the Burlington Northern rail line and Crutcho Creek, a perennial stream tributary to the

North Canadian River. Other surface water bodies bounding the Mosley site include a shallow surface

water body to the north that was formerly used as a soil borrow area (North Pond), a shallow

water-filled borrow pit to the south that was used as a source of daily cover for EORDF (South

Swamp), and an inactive sand and gravel excavation southwest of the Site. In addition, a small

(approximately ½ acre) sedimentation pond, referred to as the retention pond, is located in the

northeastern corner of the site and collects surface runoff near the pond.

Predominantly operated as an aboveground facility, the site is underlain with North Canadian River

alluvium overlying the bedrock unit known as the Garber-Wellington sandstone. The alluvium is

composed of unconsolidated sediments deposited by the North Canadian River. It is the uppermost of

the two principal geologic units, contains the shallowest ground water layer, and extends to a depth of

about 50-feet below the ground surface. The underlying Garber-Wellington formation is a consolidated

unit composed of sandstone, siltstone, and claystone. Portions of the Garber-Wellington form an aquifer

that is used as a source of drinking water by the cities of Midwest City, Spencer, and Oklahoma City.

The maximum thickness of the Garber-Wellington formation is reported to be 900 feet thick; however,

the RI was designed to characterize hydrogeological and geochemical conditions in the alluvium and the

upper 30 feet of the Garber-Wellington formation only.

The MRSL was originally owned by Floyd Swen, who operated the site under the name A-1 Sanitation

Company from 1971 to 1975. From 1975 through 1984, the landfill was owned and operated by

Oklahoma City Disposal Inc. (OCD), which at the time was a subsidiary of SCA Services Inc. (SCA).

Originally permitted by Oklahoma State Department of Health (OSDH) (now Oklahoma Department

of Environmental Quality [ODEQ]) to be operated as a sanitary landfill, OCD was authorized by

OSDH to accept industrial hazardous wastes between February 20, 1976 and August 24, 1976, due to

the temporary closure of the Royal Hardage Landfill in Criner, Oklahoma. During this 6 month time

period, OCD accepted approximately 1.7 million gallons of predominantly liquid hazardous waste,

which included industrial sludges, caustics, plating sludge, acid solutions, oil emulsions, alkaline

solutions, solvents, paint sludge, toxaphene, and trichlorethylene. All of the hazardous waste was placed

in three below-grade unlined pits (referred to as the waste pits) that are now buried beneath municipal

waste. In 1984, WMO acquired the stock of SCA, which thus transferred the ownership and operation

and maintenance (O&M) of the MRSL to WMO. The landfill reached its permitted capacity and was

closed


in November 1987. A compacted clay cover was installed over the landfill in 1988 in accordance with

existing regulations governing landfill closure. That same year, the Mosley site was proposed to the

NPL, pursuant to Section 105 of the CERCLA.

The nature and extent of contamination near the MRSL was evaluated by sampling various media

during the RI. RI activities included field sampling and testing of surface and near-surface soils, waste

pit soils, landfill leachate, ground water, surface water, and sediments.

Waste pit soil and leachate samples were collected first to determine what contaminant constituents

were present in the waste pits, and to establish concentration baselines for those contaminants to aid in

clarifying a source of any contamination found in the media sampled around the site. The waste pit soil

samples exhibited elevated concentrations of inorganic compounds indicative of the industrial hazardous

waste that may have been disposed of in the waste pits. However, none of the other media sampled

exhibited elevated concentrations of similar compounds, indicating that the inorganic compounds have

not migrated out of the waste pits at appreciable concentrations. Similarly, analysis for organic

compounds in the waste pit soils indicated that a distinct source of organic constituents was absent. In

all instances, maximum concentrations of volatile organic compounds are less than 100

milligram/kilogram (mg/kg).

During the RI, leachate was defined as water contained within the MRSL that would have come into

contact with municipal refuse or waste pit soils. Since industrial hazardous wastes were reportedly

disposed of as liquids, compounds contained within the wastes would have contributed directly to

leachate or could have sorbed onto waste pit soils and then subsequently desorbed into leachate.

Analytical comparisons conducted during the RI found that compounds in leachate samples were

generally 10 to 100 times lower than the maximum concentrations detected in the waste pit soil samples

indicating minimal transport of contaminants from the waste pit soils to the leachate.

Because the waste pits are below grade, the primary exposure pathway was considered to be through

ground water migration. Organic compounds detected in the alluvial ground water suggested that it was

potentially impacted by contaminant migration from the MRSL, historic pesticide use in the area, and

the waste pits. This was based on the fact that elevated organic concentrations were detected

downgradient of the landfill and the waste pits, in the area immediately north of the landfill. However, no

definable plume (which would point to a specific source) of organic contamination was observed. The


concentrations of all volatile organic compounds in the alluvial ground water were below Safe Drinking

Water Act (SDWA) MCL standards, with the exception of vinyl chloride and trichloroethene. The

waste pit soil samples exhibited elevated concentrations of inorganic compounds indicative of the

industrial hazardous wastes that may have been disposed at the MRSL. However, none of the other

media samples exhibited elevated concentrations of similar compounds, suggesting that the inorganic

compounds have not migrated out of the waste pits at appreciable concentrations. (Golder 1991).

The Garber-Wellington ground water was determined to have been slightly impacted by downward

recharge from the overlying alluvial aquifer in the area immediately north of the landfill. Organic and

inorganic analytical results suggest slightly elevated concentrations of some compounds in the

Garber-Wellington aquifer in this area. Hydraulic head data support the potential for enhanced vertical

flow between the two aquifers north of the landfill.

Based on a review of the data gathered during the RI, neither surface waters nor sediments were

measurably impacted by discharges of compounds transported by ground water from the landfill or

waste pits. Organic and inorganic results for surface water indicate that this medium has been impacted

by discharges from sources located upstream of the landfill. Sediments have apparently been impacted

by surface runoff from the landfill or other off-site sources.

4.0 REMEDIAL ACTIONS

The following sections discuss the remedies selected, remedy implementation, and system operations.

4.1 REMEDIES SELECTED

As defined in the ROD, signed June 29, 1992, the Site is being handled as one operable unit, at which

both the source of the contamination (the waste pits) and the contaminated ground water present in the

alluvial aquifer are addressed. The remedial objectives established for the MRSL site were to:

• Contain the slight ground water contamination that currently exists within the siteboundaries.

• Implement institutional controls to prevent exposure to on-site contaminants.


• Preserve the current beneficial use of offsite ground water as a potential source ofdrinking water.

• Prevent degradation of the Garber-Wellington aquifer.

• Prevent water infiltration through the landfill that could increase contaminant transportinto the ground water.

• Restore ground water to beneficial use through natural attenuation.

• Prevent direct contact with, and exposure to, landfill contents.

• Prevent inhalation of and explosion of landfill gas.

The remedial actions for the MRSL site are:

• Implement institutional controls including land use restrictions, access restrictions,posting of signs, fencing, and restrictions on the extraction and use of ground waterfrom the site water wells.

• Restore ground water as a potential source of drinking water through the process ofnatural attenuation.

• Continue ground water monitoring to determine if current conditions improve, remainconstant, or worsen.

• Monitor leachate migration via ground water monitoring and periodic sampling.

• Implement a landfill gas monitoring system to prevent explosion and inhalation hazards.

• Repair and improve the existing cap and add a vegetative soil layer to reduce erosionand infiltration.

EPA identified contingency measures in the ROD that may be adopted in the event that additional

remedial action is required to address contamination at the site. They are:

• Install additional monitoring wells to determine if the natural attenuation remedy is failingbased on the contingency measure criteria (see below). If the contingency measurecriteria are exceeded, begin extracting the contaminated water to facilitate or acceleratecleanup of contamination.

• Submit a Remedial Action Plan describing a plan for extraction, treatment, or disposalof contaminated ground water in order to achieve the state and federal standards.


• Begin extracting and treating the ground water until contaminant concentrations arebelow the SDWA standards, or if SDWA standards do not exist, until concentrationsare achieved which do not present an excess cancer risk greater than 1x10-6. Dischargetreated ground water to either a publicly owned treatment works or to surface waters incompliance with ARARs.

The contingency measure criteria are considered indicators that the selected remedy is not performing

as required. They are intended to trigger the aforementioned contingency measures beginning with

confirmation ground water sampling, and potentially resulting in implementation of active ground water

treatment remedies if determined to be necessary by EPA. The criteria are:

1. A statistically significant increase in contamination in the wells established as part of theground water monitoring system. The statistical increases also will be evaluated in termsof the impact on cumulative risk to human health and the environment. For example, if acontaminant exhibits a statistically significant increase, but there is no net increase in riskdue to factors such as decreases in previously detected contaminants or the fact that thenew contaminant is not toxic at the concentrations detected, there will not necessarilybe a presumption that active remediation is required. Exceptions to this presumptionwould include, but not be limited to, situations such as that in which data indicates thatrisk is increased at other locations such as beyond the monitoring point or in theGarber-Wellington due to migration, or if the newly detected contaminant concentrationindicates that an MCL may be exceeded beyond the point of compliance.

2. The appearance in the Garber-Wellington aquifer of any contaminant or combination ofcontaminants that exceed a 1x10-5 (1 in 100,000) excess cancer risk or that have anoncarcinogenic hazard indices greater than 1.0. There shall be a presumption that anincrease in risk in the Garber-Wellington above 1x10-5 excess cancer cases is indicativethat natural attenuation is not working to prevent further degradation of theGarber-Wellington aquifer by the more contaminated overlying alluvial aquifer. Activeremediation of the alluvial aquifer and/or the Garber-Wellington will be required unlessdemonstrated to the EPA to be technically impracticable.

3. Any contamination that creates a risk greater than 1x10-4 excess cancer cases in eitherthe alluvial or Garber-Wellington aquifer at the point of compliance or in off-site wells.There shall be a presumption in such cases that the remedy is not performing asrequired, and that active ground water remediation will be required unlessdemonstrated to the EPA to be technically impracticable.

4. The effectiveness of natural attenuation to reduce contamination in the alluvial aquiferwill be evaluated after each five year review of the remedy. If natural attenuation is notworking to reduce contaminant concentrations-including but not limited toconcentrations of vinyl chloride and/or benzene-in the alluvial aquifer after the initial fiveyear review, or subsequent five year reviews, the EPA may require implementation ofactive ground water remediation measures. Such measures may include newtechnologies, not considered for the 1992 ROD, that are technically practicable. In the


event such technologies are implemented at the Site, the EPA will make appropriatechanges in the ROD.

4.2 REMEDY IMPLEMENTATION

The remedial action for the MRSL site is being undertaken pursuant to the terms of a Unilateral

Administrative Order (UAO) that was issued by the EPA on January 28, 1994, and became effective

February 14, 1994. The UAO required the implementation of the selected remedy as described in the

1992 ROD.

Institutional controls have been implemented by WMO in accordance with the requirements stipulated

in the ROD. On April 1, 1994, WMO filed a covenant with the Oklahoma County Clerk’s (OCC)

Office identifying land use restrictions which would be binding on all current and future owners of the

property. These restrictions prohibit domestic use of extracted water from onsite wells, installation of

ground water wells onsite for other than remedial purposes, and the use of property for residential or

agricultural purposes. WMO also filed a deed notice on May 12, 1994 with the Register of Deeds of

the OCC’s office. The deed notice informs prospective purchasers and users of the property that

institutional controls including land use restrictions, access restrictions, posting of signs, and restrictions

to ground water use are enforced.

Construction of a 14-well ground water monitoring network was completed on February 25, 1995,

subsequent to which WMO initiated a quarterly ground water (and surface water) monitoring program.

Construction of the landfill gas management system (LGMS) commenced on August 24, 1995, and was

substantially complete by February 1996. The LGMS included 43 gas extraction wells, gas collection

headers, a lateral pipe network, extraction wells, pneumatic air lines, an air compressor, gas probes,

and a blower/flare station.

Landfill cover remediation activities began on February 21, 1996, with Phase I of the cover remediation

addressing approximately 25.8 acres of the lower part of the landfill slope and the northeast disposal

area. Phase I activities included (1) ensuring a minimum 2-foot thick clayey soil cover and an

approximate 1-foot thick topsoil cover; (2) seeding and sprigging of the topsoil; (3) construction of an

access road; and (4) construction of surface water drainage features. Phase I was completed on


May 24, 1996. The remaining portion of the landfill (approximately 27 acres) has been receiving

construction and demolition debris to raise existing grades and improve drainage. A new cover system

consisting of 2 feet of re-compacted clay and 1 foot of top soil will be constructed over the 27 acres

after design elevations have been reached. As of February 7, 2000, there are approximately 670,000

cubic yards of air space remaining to be filled with waste before the final elevations are reached.

4.3 SYSTEM OPERATIONS

Operations and maintenance (O&M) activities for the MRSL were described in the O&M plan dated

June 1996. The following is a summary of the requirements:

• Ground water monitoring wells—operate pumps and conduct ground watersampling and water level measurements in accordance with procedures discussed in theRemedial Goal Verification Plan. Inspect wells for signs of damage quarterly and checkfor silt intrusion annually. Take appropriate corrective measures.

• Landfill gas management system—operate gas extraction wells, condensatemanagement system, and flare station. Inspect extraction wells, flare station, gascollection headers, and probes quarterly. Take corrective measures as appropriate.

• Landfill cover system—conduct routine inspections for signs of erosion, settlement,desiccation, and other environmental stresses during quarterly inspections. Generalmaintenance will consist of minor repairs to the cover system, irrigation, and mowing ofvegetative cover.

Operation and maintenance as part of the ongoing remedial action have been consistent with these

requirements.

Monitoring plans required that (1) ground water be monitored quarterly for 8 quarters starting

March 1995, and semi-annually thereafter; (2) surface water and sediment samples from Crutcho

Creek be collected annually; and (3) surface water samples from North Pond be collected on the same

schedule as ground water. Compliance with the monitoring plan schedules has been verified until 1996,

whereupon surface water sampling of Crutcho Creek was inadvertently discontinued, and sampling of

the surface water from the North Pond was conducted on an annual basis. Communications with the

WMO Environmental Manager subsequent to these findings have established that annual sampling

efforts will be renewed in Crutcho Creek, in compliance with the original monitoring plan.


5.0 FIVE-YEAR REVIEW PROCESS

Tetra Tech conducted the MRSL site five-year review for WMO. The five-year review at MRSL

consisted of the following activities: (1) a review of relevant documents (see Appendix A); and (2) a

site visit combined with interviews with representatives of WMO operating the MRSL.

6.0 FIVE-YEAR REVIEW FINDINGS

The following sections present Tetra Tech’s findings during interviews, the site inspection, and a review

of available risk information.

6.1 INTERVIEWS

No domiciles, or inhabitants thereof, were located visually from the top of the active portion of the

landfill approximately 200 feet above the grade of the surrounding area. The interview process was thus

limited to Mr. Jim Meinholz, site superintendent of MRSL. Based on that interview, Tetra Tech learned

that the site is running (and is being run) smoothly and efficiently with no measurable detrimental impact

to the Site or adjacent land.

6.2 SITE INSPECTION

Tetra Tech conducted a site inspection on Thursday, July 27, 2000. Present were Mike Wilson and

Chitranjan Christian from Tetra Tech, and Jim Meinholz with WMO. A summary of the inspection

findings is presented below; Exhibit B in Appendix B contains the site visit report.

Ambient conditions during the inspection were partly cloudy and windy, with temperatures in the

mid-90s. Visually, the landfill cap was found to be in good condition; however, rutting or erosion gullies

were evident on the north face of the cap. The remaining areas of the landfill had excellent vegetative

cover, a fact Mr. Meinholz attributed to their spreading hay over the cap (to reduce erosion and aid in

reestablishing the vegetative cover) in the spring. No noticeable depressions, excessive cracks, leachate

seeps, or other indications of distress were noted.


6.3 ARAR REVIEW

The ROD for the MRSL site was issued in June 1992. The following requirements were identified as

ARARs for the selected remedy:

• National Historical Preservation Act, 16 U.S.C. 469 et seq and 36 CFR 65 and 36CFR 800, pertaining to preservation of historical artifacts

• Endangered Species Act, 16 U.S.C. 1531 et seq, and 50 CFR 200 and 402 and Fishand Wildlife Coordination Act, 16 U.S.C. 1531 et seq and 33 CFR 320 - 330pertaining to the protection of endangered and threatened species.

• Oklahoma Underground Storage Tanks Act OS Title 17 and Oklahoma UndergroundStorage Tank Rules OS Title 17 pertaining to closure of underground storage tanks.

• Safe Drinking Water Act Maximum Contaminant Levels and Oklahoma EffluentLimitations and Water Quality Criteria for Ground Water pertaining to remediation ofground water and discharge of treated ground water to surface water.

• RCRA Rules 40 CFR 24.310 and 40 CFR 264.117 and Oklahoma Solid WasteManagement Act 63 OS 1981 and the Oklahoma Controlled Industrial Waste DisposalAct 63 OS 1981 pertaining to closure and post-closure of the landfill.

Tetra Tech evaluated compliance with ARARs to determine if new requirements have been

promulgated that may affect protectiveness. The Oklahoma Solid Waste Management Act was

amended in 1993 and 1994, but these amendments do not appear to affect the MRSL remedial action,

which was limited to repair of the existing cap installed in accordance with the Oklahoma Solid Waste

Management Act 63 OS 1981. RCRA closure and post-closure regulations have not changed since the

ROD was signed.

Table 20 of the ROD (Table 20) lists chemicals and their associated MCLs and state water quality

criteria. Tetra Tech reviewed Federal and state regulations to determine if there were any newly

promulgated values for the chemicals listed in Table 20. The changes to MCLs for the following

chemicals were noted:

• Chlorobenzene, Chromium, Cyanide, Endrin, Ethyl Benzene, Chlordane,Heptachlor, Methoxychlor, Trichloroethane,1,2-Dichloropropane,Benzo(a)pyrene, and Cadmium—Table 20 lists proposed MCLs. These MCLswere finalized at the concentrations provided in Table 20.


• Chrysene—Table 20 lists 0.0002 as the proposed MCL. No final MCL has beenpromulgated.

• Copper—The copper MCL is a treatment technology that is 1.3 milligrams per liter(mg/L) at the tap.

• Delta BHC—Table 20 lists 0.004 mg/L as the MCL. The final lindane MCL (used fordelta BHC) is 0.0002 mg/L.

• Indeno(1,2,3-cd) pyrene—Table 20 lists 0.0004 as the proposed MCL. Nofinal MCL has been promulgated.

• Lead—The lead MCL is a treatment technology that is 0.015 mg/L at the tap.

• Nickel—Table 20 lists 0.1 mg/L as the proposed MCL. A final MCL waspromulgated but withdrawn by court order in 1995.

• Pentachlorophenol—Table 20 lists 0.2 mg/L as the proposed MCL. The final MCLis 0.001 mg/L.

• 1,2-Dichloroethene—Table 20 lists two values. The final MCL is 0.07 mg/L.

• Alpha—BHC Table 20 lists 0.004 mg/L as the MCL. The final lindane MCL (used foralpha-BHC) is 0.0002 mg/L.

• Barium—Table 20 lists two values for barium. The final MCL is 2 mg/L.

• Benzo(a)anthracene and Benzo(b)fluoranthene—Table 20 lists proposed MCLs.No MCLs have been promulgated for these chemicals.

• Beryllium—Table 20 lists 0.001 mg/L as the proposed MCL. The final MCL is 0.004mg/L.

• Beta-BHC—Table 20 lists 0.004 mg/L as the MCL. The final lindane MCL (used foralpha-BHC) is 0.0002 mg/L.

• Bis(2-ethylhexyl)phthalate—Table 20 lists 0.004 mg/L as the proposed MCL. Thefinal MCL is 0.006 mg/L.

• Selenium—Table 20 lists 0.01 mg/L as the MCL. The final MCL is 0.05 mg/L.

For the state water quality criteria for ground water, the only change concerns phenol. Table 20 lists the

state water quality criteria for phenol as 0.3 mg/L. The state regulations do not currently list a value for

phenol.


6.4 DATA REVIEW

As described in the Ground Water Monitoring Plan for the Site, an intrawell statistical method of

determining constituent concentrations and identifying cumulative increases is being utilized to monitor

the existence of detrimental impact to the ground water from the landfill or the waste pits. A

contaminant concentration baseline was established from data obtained from eight quarterly sampling

events conducted in 1995 and 1996. In order for a contaminant concentration to be considered

significant, or warrant further observation, the constituent must exceed the baseline for two consecutive

sampling events. No statistically significant exceedances of the baseline have occurred in the seven

semiannual ground water sampling events that have occurred since 1997. However, a trend of

increasing concentrations is becoming evident for barium in well MWI2R and manganese in well

MW201.

7.0 ASSESSMENT

The following conclusions support the determination that the remedy at the MRLS site is expected to

be protective of human health and the environment upon completion.

Question A: Is the remedy functioning as intended by the decision documents?

• HASP/Contingency Plan—Both the HASP and the Contingency Plan are in place,sufficient to control risks, and properly implemented.

• Implementation of Institutional Controls and Other Measures—Institutionalcontrols have been implemented.

• Remedial Action Performance—The landfill cover system has been effective inisolating waste and contaminants. Some minor erosion/rutting has occurred on the northside of the cap, but it has not affected the performance or integrity of the cover system.

• System Operations/O&M—System operations have been consistent with therequirements.

• Cost of System Operations/O&M—O&M costs were not available for review.

• Opportunities for Optimization—None were observed or suggested.

• Early Indicators of Potential Remedy Failure—None were observed.

17A:\final 5yr_rev.wpd

Question B: Are the assumptions used at the time of remedy selection still valid?

• Changes in Standards and To Be Considereds—This five-year review identifiednew MCLs for contaminants promulgated after the ROD was signed. However, sinceMCLs for benzene and vinyl chloride (the primary contaminants of concern at MRSL)remain unchanged, it is highly unlikely that the feasibility of this remedy has beenaffected.

• Changes in Exposure Pathways—No changes in exposure pathways have beenobserved.

• Changes in Toxicity and Other Contaminant Characteristics—New toxicityfactors have been released for vinyl chloride. However, this does not call into questionthe protectiveness of the remedy since these changes were either insignificant orworked to reduce the potential risk posed. Changes in MCLs for other compoundslisted in Section 6.3 might have been the result of changes in toxicity or carcinogenicity.However, this was not researched since the potential risk posed at the site is primarilydue to benzene and vinyl chloride.

• Changes in Risk Assessment Methodologies—There have been no changes in riskassessment methodologies since the ROD was signed.

Question C: Has any other information come to light that could call into question theprotectiveness of the remedy?

No additional information has been identified that would call into question the protectiveness of the

remedy.

8.0 DEFICIENCIES

Deficiencies were discovered during the five-year review and noted in Table 2. None of these

deficiencies are sufficient to warrant a finding of the remedy not being effective; but corrective actions

should be undertaken to insure that any change that might jeopardize the protectiveness of the site is

mitigated as soon as possible. The most significant deficiency was minor erosion/rutting that has

occurred on the north side of the cap. However, this does not affect the performance or integrity of the

cover system.


TABLE 2

IDENTIFIED DEFICIENCIES

Deficiencies Currently Affects Protectiveness (Y/N)

Evidence of Site Trespassing

None N

Damage to Landfill Cover

Erosion on north face N

Monitoring Wells Require Maintenance

Minor cap repair is needed on one well N

Security Measures Required

None N

Deed Restictions

None N

Surface Water

Sampling in Crutcho Creek is not in compliance withmonitoring plan

N


9.0 RECOMMENDATIONS AND FOLLOW-UP ACTIONS

Since there have been no findings that warrant a more aggressive approach to remediating the site, the

EPA recommends that remedial action continue in accordance with currently approved plans. Given the

apparent success of establishing a viable ground cover on the south, east, and west faces, the rutting

and erosion occurring on the north face would easily be mitigated by continuing the practice of

spreading hay to that face of the cap. Upon initiation of the next round of semiannual ground water

sampling, surface water samples from both Crutcho Creek and the North Pond should be collected for

analysis. The recommendations and follow up actions are outlined in Table 3.

10.0 PROTECTIVENESS STATEMENTS

The results of the five-year review indicate that the remedy has been protective of human health and the

environment. Since contamination has remained within site boundaries, there is no immediate risk

posed. The remedy for the site is expected to be protective of human health and the environment after

cleanup levels have been achieved.

11.0 NEXT REVIEW

This is a statutory site that requires ongoing five-year reviews. The next review will be conducted within

the next five years but no later than November 6, 2005.

12.0 OTHER COMMENTS

None.


TABLE 3

RECOMMENDATIONS AND FOLLOW-UP ACTIONS

DeficienciesRecommendations/Follow-up Actions

PartyResponsible

OversightAgency

MilestoneDate

Follow-up Actions:Affects Protectivness

(Y/N)

Surface watersampling (CrutchoCreek) not incompliance withmonitoring plan

Initiate samplingprocedures in linewith monitoring planrequirements.

WMO EPA 8/30/00 N

Damage to Landfillcover

Repair or regradeerosion gullies;continue hay seeding

WMO EPA 8/30/00 N

Monitoring wells Repair cap onmonitoring well

WMO EPA 8/30/00 N

Notes:

EPA U.S. Environmental Protection Agency

APPENDIX A

DOCUMENTS REVIEWED

(One Page)

S:\PRIVATE\P1368\REPORT\5YR_REV.WPD

DOCUMENTS REVIEWED

Golder Associates, Inc. 1991. “Final Remedial Investigation Report”. August.

Otter Creek Environmental Services, L.L.C. 2000. “Results of the Statistical Analysis on the GroundWater Data Following the First Semi-Annual Monitoring Event in 2000 at Mosley RoadLandfill.” April.

Rust Lichliter/Jameson (Rust). 1995. “Mosley Road Sanitary Landfill Remedial Action Work Plan.”Prepared for Waste Management of Oklahoma (WMO). March.

Rust. 1997a. “Construction Documentation Report Landfill Gas Management System. Mosley RoadSanitary Landfill. Oklahoma City, Oklahoma.” Prepared for WMO. March.

Rust. 1997b. “Construction Quality Assurance Documentation Report for Phase I Landfill CoverRemediation. Mosley Road Sanitary Landfill. Oklahoma City, Oklahoma.” Prepared forWMO. May.

Rust. 1997c. “Mosley Road Sanitary Landfill Operation and Maintenance Plan, Volume l.” Preparedfor WMO. June.

U.S. Environmental Protection Agency (EPA). 1992. CERCLA Record of Decision for Mosley RoadSanitary Landfill, Oklahoma City, Oklahoma. June

EPA. 1994. Administrative Order for Remedial Design and Remedial Action regarding Mosley RoadSanitary Landfill Superfund Site, Oklahoma City, Oklahoma. January.

EPA. 2000. Integrated, Risk Information System.Available on-line at: http://www.epa.gov/iris/subst/1001.htmLast Updated: August 7, 2000

APPENDIX B

SITE VISIT REPORT

(21 Pages)

S:\PRIVATE\P1368\Report\5YR_REV.WPD

SITE VISIT REPORT

MOSLEY ROAD SANITARY LANDFILLOKLAHOMA CITY, OKLAHOMA

Prepared for

WASTE MANAGEMENT OF OKLAHOMA, INC.

Date Prepared : July 31, 2000Prepared By : Tetra Tech EM Inc.Telephone No. : (214) 754-8765

CONTENTS

Section Page

1.0 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-1

2.0 BACKGROUND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-1

3.0 SITE VISIT ACTIVITIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-3

4.0 FINDINGS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-4

Exhibits

A PHOTOGRAPHS

B SITE INSPECTION CHECKLIST

B-1S:\PRIVATE\P1368\Report\5YR_REV.WPD

1.0 INTRODUCTION

Tetra Tech EM Inc. (Tetra Tech) was tasked by Waste Management of Oklahoma, Inc. (WMO) to

conduct a five-year review of the effectiveness of the remedy they have employed at the Mosley Road

Sanitary Landfill (MRSL or the site) to protect human health and the environment.

Tetra Tech conducted a site visit as part of the requirements for a five-year review, to verify that all

components of the selected remedy are operating in accordance with criteria established in the Record

of Decision (ROD). This report summarizes the results of the site visit at the MRSL.

2.0 BACKGROUND

The site covers approximately 72 acres in a relatively undeveloped area near the boundary of

Oklahoma City and Midwest City, Oklahoma. The site is located at 3300 Mosley Road, between

northeast (NE) 23rd to the south and NE 36th Street to the north (see Figure 1). The site is bounded to

the west by Mosley Road, across from which is the East Oak Recycling and Disposal Facility (currently

in operation); to the north by a shallow surface water body (North Pond); to the east by the Burlington

Northern rail line; and to the south by a shallow, water-filled borrow area (South Swamp) (see Figure

2). Nearby surface water bodies include the North Canadian River, a major perennial stream that flows

from southwest to northeast about 0.5 mile east of the site, and Crutcho Creek, an intermittent stream

that flows from south to north about 0.1 mile east of the site.

The landfill was originally permitted by the Oklahoma State Department of Health (OSDH) in

June 1973. Between February 20, 1976, and August 24, 1976, OSDH authorized the landfill to accept

hazardous industrial wastes. These wastes primarily consisted of liquids and sludges, including industrial

sludge, caustic material, plating sludge, acid solutions, oil emulsions, solvents, and paint sludge. The

hazardous industrial wastes were deposited in three unlined pits, referred to as the “waste pits.” The

waste pits are currently covered by municipal refuse, construction debris, and a clay cover.

The landfill reached its permitted capacity in November 1987 and was closed. Early in 1988, a

compacted clay cover was installed over the landfill in accordance with governing landfill regulations.


On February 6, 1987, the site received a U.S. Environmental Protection Agency (EPA) Hazard

Ranking System score of 38.06, which did not take into account the clay cap installation that occurred

in 1988. On June 24, 1988, the EPA proposed the MRSL for inclusion on the National Priorities List.

The Consent Order requiring remedial investigation (RI) activities at the Site was signed on July 28,

1989. RI activities began in January 1990, and the ROD was signed on June 29, 1992.

Ground water underlying the site occurs in both the alluvial and Garber-Wellington aquifers. The

thickness of alluvial deposits in the site vicinity generally range from 30 to 50 feet, although in some

areas, including the North Pond area and along Crutcho Creek to the east, the alluvium is less than 30

feet thick. A north-south trending flow divide is present in the alluvial aquifer and separates ground

water flowing east toward Crutcho Creek from ground water flowing west toward the North Canadian

River. Bedrock directly underlying the alluvial deposits consists of the Garber-Wellington Formation

existing under semiconfined conditions. The main source of recharge to the aquifer is infiltration of

precipitation and surface water. The North Canadian River is the major discharge area for the

Garber-Wellington Aquifer.

The primary contaminants of concern affecting the soil, debris, and ground water that exceeded

maximum contaminant levels (MCLs), were arsenic, barium, benzene, manganese, trichloroethene, and

vinyl chloride. Contaminated soil was encountered mainly in the waste pits underlying the landfill.

Contaminated ground water was found in the alluvial and bedrock aquifers just north and downgradient

of the landfill.

As described in the ROD, the primary components of the remedial action at the site include the

following:

• Institutional controls including land use restrictions, access restrictions, posting of signs,fencing, and restrictions on the extraction and use of ground water from site water wells

• Restoration of ground water as a potential source of drinking water through the processof natural attenuation

• Continued ground water monitoring to determine if current conditions improve throughtime, remain constant, or worsen

• Monitoring of leachate migration via ground water monitoring and periodic sampling


• Implementation of a landfill gas monitoring system to prevent explosion or inhalationhazards

• Repair and improvement of the existing cap and addition of a vegetative soil layer toreduce erosion and infiltration

EPA also identified contingency measures that would be considered if it was determined that additional

remedial actions were necessary to address potential ground water contamination. The following

response actions were recognized as potential requirements should the EPA determine that additional

remedial action is necessary:

• Install additional monitoring wells to evaluate the effectiveness of the natural attenuationremedy based on contingency criteria. If the contingency measure criteria areexceeded, begin extracting the contaminated water to facilitate or accelerate cleanup ofthe contamination.

• Submit a remedial action plan describing a strategy for the extraction, treatment anddisposal of contaminated ground water in order to achieve State and Federal standards.

• Begin extracting and treating the contaminated ground water until the concentrations arebelow the Safe Drinking Water Act (SDWA) standards; or if SDWA standards do notexist, until concentrations are achieved that do not present an excess cancer risk greaterthan 1x10-6, if technically practicable. Discharge treated ground water to either apublicly owned treatment works or to surface water in compliance with Applicable orRelevant and Appropriate Requirements.

3.0 SITE VISIT ACTIVITIES

Tetra Tech conducted the site visit on July 27, 2000. The objectives were to access site conditions and

interview (1) the nearest residents to the site, and (2) personnel involved with post-closure care.

Photographic documentation of the site visit are presented in Exhibit A. The site visit checklist is

presented in Exhibit B.

The following individuals were present during the site visit:

• Jim Meinholz, WMO

• Mike Wilson, Tetra Tech

• Chitranjan Christian, Tetra Tech


Tetra Tech initially met with Mr. Meinholz to discuss operation and maintenance issues, concerns, and

recommendations relating to maintaining the protectiveness of the remedy. Tetra Tech then walked

around the perimeter of the site, traversed the slopes, and drove along all of the access and perimeter

roads. The landfill slopes, with the exception of the north face, were well vegetated with a thick

protective mat of hay underfoot for supplemental seeding and erosion protection. Mr. Meinholz stated

that operations had not had a chance to continue with the hay spreading operations on the north face,

but they would initiate those activities before the Fall. Erosion gullies were located on the north face of

the cap due to the lack of cover (vegetation and hay). None were severe enough to warrant concern

over the protectiveness of the cap, and could be easily remedied with light earth moving equipment

prior to commencement of the hay sowing operations. No evidence of subsidence or desiccation was

noted anywhere on the Site, and evidence of erosion was limited to the north face. All but one of the

monitoring well risers were intact and in good shape. Fencing surrounding the site was sound, well

posted with warning signs, and had locked access points provided where appropriate. The Site roads,

including Mosley Road, were well graded and without potholes or wash boards. Vehicular activity was

continuous to the crest of the landfill with ongoing construction and demolition waste disposal. Daily

cover was well graded and clean.

The existence of an adjacent residence was suggested in the January 1998 Ground Water Monitoring

Plan; however, no evidence of a domicile was evident from a vantage point 200 feet above the

surrounding area at the crest of the landfill.

4.0 FINDINGS

No significant discrepancies, other than the aforementioned erosion gullies on the north face, were

noted during the Site visit. From what could be discerned during the traversal of the site, the cap and all

monitoring/collection wells appeared to be in excellent condition.

EXHIBIT A

PHOTOGRAPHS

(13 Pages)

five-year review report for the mosley road sanitary landfill oklahoma city, oklahoma ... ·...

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