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Operating Industries, Inc. (OII)
Superfund Site

Monterey Park, California

Site Overview

The Operating Industries, Inc. (OII) Landfill (Site) is a 190-acre former industrial/municipal landfill and Superfund Site, located in Monterey Park, California. The Pomona Freeway divides the Site into two parcels: the South Parcel and North Parcel.  The South Parcel consists of 145 acres while the North Parcel consists of the remaining 45 acres.


The Site is now in Operations, Maintenance and Monitoring (OMM) under the Eight Partial Consent Decree. The Leachate Treatment Plant (LTP) and the Thermal Destruction Facility (TDF) are located on the North Parcel. These two systems are operated and maintained by O&M, Inc. under the supervision of Roberto Puga, Project Coordinator, and his team at PathForward Consulting, Inc. at the direction of New Cure Inc. (NCI), a company created by the Work Defendants to implement Site work on their behalf.

Current Site Status

The current status of the site, as specified by RODs signed by EPA, and provided by consent decrees with EPA, is summarized as follows:

  • Installation and operation of a perimeter liquids control system in areas where contaminants are migrating from the landfill at levels that cause groundwater to exceed performance standards.

  • Reduction of contaminated groundwater beyond the landfill perimeter to below cleanup standards through monitored natural attenuation (MNA).

  • Conveyance of the collected liquids to the on-site treatment plant.

  • On-site treatment of collected liquids using the existing leachate treatment plant, modified as necessary to handle the new liquids, and discharge of the treated liquids to the County Sanitation Districts of Los Angeles County sanitary sewer system.

  • Implementation and operation of a monitoring and evaluation program to ensure that natural attenuation of the contaminated groundwater is progressing as anticipated, to detect future releases of contaminants from the landfill, and to ensure that perimeter liquids control system performance standards.

  • Establishment and management of on-site and off-site institutional controls to ensure appropriate future use of the Site and to restrict groundwater use in the immediate vicinity of Site. Institutional controls are non-engineering methods that federal, state or local governments, or private parties, can use to prevent or limit exposure to contaminants to ensure the effectiveness of remedial actions. The institutional controls supplement the engineering controls at the Site.

Green Initiative Projects

As the Site ages, the PathForward team is identifying resources used at the site that can be reused for beneficial purposes for the operation of the site and the surrounding areas.

  • In the process of identifying the viability to design, engineer, install, and maintain a solar photovoltaics (PV)/battery project located on the “Top Deck” of the South Parcel of the OII Landfill.

    • Systems have potential to generate onsite and provide up to 98% of electrical power needed to operate the Landfill.

    • Potential ability for redundant energy storage for the SCE substation to assist in meeting electrical demands and provide redundancy for ‘black outs’ of surrounding community.

  • Beneficial reuse of treated effluent of the Leachate Treatment Plant for onsite Irrigation for re-vegetation and dust control during routine maintenance:

    • Estimated demand for the Treated LTP effluent for these beneficiary uses include:

      • Onsite Irrigation – Demand on the irrigation system during the “dry” season is estimated to ~180,000 gallons a month.

      • Dust Control during routine maintenance – Although Site conditions vary depending on daily tasks, demand for fugitive dust control averages ~210,000 gallons a month.

  • Use of livestock for cover maintenance and weed abatement to reduce carbon emissions from the Site.

Regulatory Agencies Involved

The Site falls under the jurisdiction of USEPA Region 5 with input from the California DTSC and U.S. Army Corps of Engineers.

Project News

Site History

From 1948 to 1952, the Site was operated as a municipal waste disposal facility by the City of Monterey Park. In January 1952, the Site became a privately owned landfill under the ownership of OII. The Site was formerly permitted by the California Regional Water Quality Control Board (RWQCB) to accept and dispose of certain municipal wastes, and hazardous and non-hazardous, non-sewerable liquid waste in 1976. Disposal of the liquid was confined to a 32-acre area in the western part of the South Parcel. In October 1984, waste disposal at the Site ceased and it has remained inactive. The Site was added to the National Priorities List in May 1986. The partial control measures taken by OII were found by EPA to be insufficient in maintaining site integrity. As a result, EPA conducted emergency response actions, including slope stability and erosion control improvements; surface runoff and drainage improvements; main flare station rehabilitation; site security improvements; placement of vented water meter box covers in residential areas closest to the landfill to prevent accumulation of landfill gas in meter boxes; and installation of control systems for landfill gas in nearby affected residences. The remedy selected by the 1988 Gas Migration Control ROD to address landfill gas migration was an active landfill gas collection and treatment system (USEPA, 1988). After continued settling of onsite landfill wastes and the occurrence of subsurface fires were found to have decreased the integrity of the existing landfill cap, the ROD was amended in 1990 to include an upgraded landfill cap. The amended remedy consisted of capping the landfill; installing landfill gas extraction wells around the perimeter and on the top of the cap; collecting and treating landfill gas by incineration; and dewatering saturated landfill zones (US Corps of Engineers, 2020). In September 1996, EPA signed the Final ROD, which selected a comprehensive site-wide groundwater remedy. The Final ROD also included the requirements for institutional controls. The interim RODs for Site Control and Monitoring and Leachate Management were superseded by the signing of the Final ROD; however, the activities required by them continue as part of the Final ROD. The Final ROD addresses landfill perimeter liquids control, monitoring natural attenuation of contaminated groundwater downgradient of the landfill boundary, clean-up standards, and institutional controls, as well as long-term operation and maintenance of all environmental control facilities at the landfill, excluding those facilities required by the Gas Migration Control and Landfill Cover ROD.

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