Supplemental Environmental Impact Report (SEIR)

In March 1998, the County of San Luis Obispo (County) certified an Environmental Impact Report (EIR) that evaluated and determined mitigation measures for remedial actions, including excavation of diluent plumes and treatment methods for the excavated material. Subsequently, the RWQCB issued CAO 98-38, mandating remedial actions such as the excavation of specified plumes and sumps.

Unocal’s preferred treatment method for hydrocarbon-affected soils has been bioremediation in a Land Treatment Unit (LTU). Pilot studies have shown LTU treatment to be effective in reducing hydrocarbon concentrations in diluent-affected soil. The material treated in the pilot LTU has been evaluated to provide information about the potential risk associated with reuse as excavation backfill. The project Team is working with the RWQCB to establish treatment standards and determine the suitability for reuse of LTU-treated material.

Because final treatment levels for LTU-treated material have not yet been established, reuse of LTU-treated material remains questionable. The Project Team and the Multi-Agency Coordination Committee (MACC) agreed that the excavations should be suspended until a treatment/disposal method is determined, permitted and implemented. It was also agreed that the most expedient route for determination of a suitable treatment or disposal method, or combination of methods, was to submit project descriptions for a number of methods and begin the environmental review process as soon as possible, via a Supplemental Environmental Impact Report (SEIR).

Work descriptions developed in coordination with the MACC include a variety of treatment, beneficial reuse and disposal methods. Detailed Project Descriptions were submitted to the agencies as part of an application to amend existing permits to provide information to the County for California Environmental Quality Act (CEQA) review. The Army Corps of Engineers indicated that no National Environmental Policy Act (NEPA) review would be required. The Project Team prefers to treat affected materials onsite and beneficially reuse soils in a fashion that provides for net environmental benefit, and will continue working with the agencies to address issues and necessary modifications as the permitting and review process proceeds.

For CEQA assessment, different quantities, or “Tiers," of affected material are considered, since the final project may involve a combination of treatment/disposal methods, each involving lesser quantities and associated impacts than if a single method were implemented for the entire quantity of hydrocarbon-affected material that will eventually be excavated. To determine the quantities of material that should be considered for each treatment or disposal method, the material has been separated into categories: sump material ("Category A"), previously-excavated affected material ("Category B") and affected material from the future excavations ("Category C").

The following proposed treatment, beneficial reuse and disposal methods were submitted for analysis in the SEIR:

1. Off-Site Trucking
– Affected material is transported via truck to an approved off-site solid waste handling facility for disposal.

2. Engineered Containment Unit (ECU)
– Affected material is hauled from on-site stockpiles and excavation sites to a contained area at TB9. The material is configured into a dune-like formation, capped and restored to resemble the surrounding landscape.

3. Treated Material Land Feature (TMLF) – Treated material, stockpiled at TB9 after treatment, is reconfigured to resemble a dune structure and restored to blend with the surrounding landscape.

4. Slurry Injection – Affected material is mixed with water to create a slurry which is injected approximately 2700 feet underground.

Methods submitted for substantial conformance review:

1. Land Treatment Unit (LTU) – Diluent-affected material is hauled from TB8 and/or ongoing excavations to TB9 for treatment through controlled, enhanced bioremediation.

2. Thermal Desorption Unit (TDU) – Affected material is treated with heat to vaporize hydrocarbons from the soil.

The SEIR evaluated the environmental impacts of these methods and ultimately identified Off-Site Trucking as the environmentally superior alternative, exhibiting no significant impact that could not be fully mitigated to insignificant levels.

The material to be transferred, classified as Non-Hazardous Hydrocarbon-Impacted Soil (NHIS), fits the requirements of the Santa Maria Landfill objective to obtain five million (5,000,000) cubic yards of material needed to provide a foundation layer for the closing of its remaining active cells. The May 2004 SEIR for the Santa Maria Landfill identified no significant impacts associated with the use of NHIS. Thus, the Guadalupe material can be moved to a permitted landfill where it can be contained and controlled.

In approving the use of NHIS from the Guadalupe field, the RWQCB stated:

"We believe the acceptance of additional NHIS material from the GRP (Guadalupe Restoration Project) will expedite final rolling closure activities at the Santa Maria Landfill. The use of the NHIS material as foundation layer material will enable the waste solids to be entombed under a protective cover and will accelerate closure for the unlined active landfill area." (Letter to Mr. Zhao, City of Santa Maria, August 31, 2004.)

TB8 Petroleum Hydrocarbon Affected Soil Stockpile
(~350,000 cu yd)


When the California Coastal Commission denied an appeal by a group of Santa Maria residents, the last remaining hurdle to stockpile removal and commencement of the remaining excavations in the RWQCB Cleanup or Abatement Order was removed.

Project activities resumed in mid-August 2006, and the Guaddunes website will be regularly updated as the work proceeds.



Sitewide Restoration

Restoration of areas disturbed during remediation and decommissioning activities is ongoing throughout the Field. Active restoration is currently underway in foredune habitat (22 acres), dune scrub habitat (18 acres), and dune swale habitat (5 acres). The primary goal of restoration is to establish self-sustaining plant communities that are native to the Guadalupe/Nipomo Dunes Complex and that are similar to habitats found in undisturbed areas of the dunes complex. Restoration sites are meticulously monitored to ensure that restoration is proceeding in accordance with site-specific performance standards. Recently more than 1,000 La Graciosa thistles propagated at the onsite Growing Facility were planted by a wetland near the beach, which will be carefully monitored to determine the best way to expand this listed plant species.

Outplanting La Graciosa thistles near B2 wetland

Beach Restoration:

In January 2001 Unocal began restoration of the beach and dunes that were affected by recent remediation activities at the southwestern area of the site. The purpose of the restoration activity is to restore naturally functioning, self-sustaining dune strand/beach and foredune habitats to the remediated sites. The restoration approach involves providing an environment suitable for the natural recruitment and restoration of disturbed areas. Also, as warranted, the restoration site is augmented with native seeds and plants, managed for erosion control, and weed abatement to facilitate natural restoration.

After remediation activities were completed toward the end of 2000, the beach area excavations were filled with clean sand from other areas of the site and the site returned to its approximate base level. Dune-like structures were created where natural foredunes once existed. The created dunes are smaller than those that existed prior to the excavation. Natural dunes can take up to 50 years to naturally develop and are anchored and reinforced with live and dead plant roots; the newly restored dunes began as only sculpted ridges of loose sand.

To stabilize these new dunes and to reduce the risk of harmful large-scale sand blowouts, clean rice straw plugs (free of weeds) were planted vertically into the sand. The rice straw plugs may also improve seedling establishment and enhance the survival of both seedlings and transplants. The rice straw plugs provide an effective windbreak for the seedling, as well as providing a vertical condensation surface for fog, which will run down the straw, and provide moisture to the seedlings. The use of straw plugs has been applied successfully at other restoration sites in California, including Oso Flaco Lake. However, we believe that this may be first time it has been used so close to the ocean and at such an exposed site.

The newly created dunes have remained stabilized since 2000 and most of the same plants that occurred on the dunes prior to the disturbance are found today at the restoration site. The newly created dunes have also been used by the endangered Western snowy plover during breeding season (March – September). The dunes are also providing habitat for kangaroo rats, which have established several burrows in the dunes.

Snowy plovers on restored beach dunes

Growing Facility

A growing facility has been constructed onsite to facilitate the propagation of plants to be used when restoring areas disturbed during remediation activities. Plants, cuttings and seeds are collected from remediation sites prior to disturbance and taken to the growing facility where they are cared for or germinated. Plants from the growing facility are used to augment seeding of the restoration areas. Research on various propagation techniques is also conducted on sensitive plants.

Weed Abatement

Invasive exotic plants, such as veldt grass and ice plant, are common to the Field, and the disturbance from site characterization, remediation, pilot study implementation, oil field abandonment and related activities may result in the increase of these species if not properly managed and controlled. More importantly, the presence of exotic species is a constraint to successful habitat restoration and management. Therefore, Unocal has implemented a Field-Wide Exotic Species Management and Eradication Program, with a full-time professional crew working to control the invasive exotic plants on site.

The areas of the Field that have been treated are included in the Weed Eradication Locations figure. An example of an area before and after weed abatement is shown below.



Mediation Group

Special studies are currently in progress under a technical mediation process with the goal of building consensus and resolving technical issues. Participants in the mediation process have included:

  • Regional Water Quality Control Board, Central Coast Region
  • California Department of Fish and Game
  • California Environmental Protection Agency, Office of Environmental Health and Hazard Assessment
  • Kreimes Associates (Facilitator)
  • U.S. Fish and Wildlife Service
  • National Oceanic & Atmospheric Administration
  • Consultants LFR Levine Fricke, BBL and Applied Geochemical Strategies
  • San Luis Obispo County and its consultants Morro Group and Marine Research Specialists

This team of agencies, company and consultants is performing studies that include defining treated backfill criteria that are protective of water quality and ecology. They are also performing a detailed study of oil well sumps, natural attenuation sustainability, plume stability, and are refining a groundwater model of the 2,700-acre site. The Site-Wide Screeninig-Level Ecological Risk Assessment was ratified in 2004.

Please refer to the Mediation Group's most recent Summary of Progress and Agreements.

Research and Studies

Research has recently been completed on two sensitive wildlife species present at the site, the western snowy plover and the California red-legged frog. The western snowy plover study was undertaken to determine the factors that influence nesting site selection. The information gleaned from the study was incorporated into the design of restored foredune areas to make them more suitable for nesting plovers. Plover study results indicate that the restored foredunes are providing good nesting habitat for the plovers.

The California red-legged frog study involved placing small radio transmitters on the frogs, relocating them from a drainage pond where they were at risk, and monitoring their movements. The results of this study will be used to better ensure their protection during remediation projects and to facilitate their reintroduction to restored wetlands.