Terraphase supported the National Park Service in developing a Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) Engineering Evaluation/Cost Analysis (EE/CA) for a historical military installation located within a recreational area and national park overlooking the Golden Gate Bridge. The site, an important and sensitive research and recreational area in California, had been impacted by legacy military operations and structural deterioration and required careful evaluation of risks to human health and ecological receptors in order to determine the degree to which remedial action would be warranted to facilitate restoration.
Scope of Services
Deterioration of on-site structures, as well as former military operations, resulted in the release of hazardous substances to the environment. Terraphase conducted a comprehensive EE/CA that included both human health and ecological risk assessments. The human health risk assessment evaluated potential exposures for recreational users, possible future park residents, and construction or maintenance workers through contact with impacted soil.
The potential for adverse impacts to wildlife was evaluated using food chain modeling for birds and mammals representing different feeding guilds (e.g., herbivore or carnivore) and food web trophic levels (e.g., primary, secondary, or tertiary consumers). The ecological risk assessment accounted for the fraction of different dietary components and the receptor’s home range. A database search of threatened and endangered species identified the possible presence of the California red-legged frog (Rana aurora draytonii) in the vicinity of the site. A literature search revealed that the site does not provide the breeding and foraging requirements for the frog (i.e., a permanent water source, the presence of emergent vegetation, and a shrubby riparian zone). As a result, we determined the exposure pathway was incomplete and a quantitative assessment of potential risk to the frog was not warranted.
The EE/CA included several remedial alternatives including no action and excavation and off-site disposal of soil (with and without land use restrictions). The EE/CA formed the basis of an Action Memorandum for the selection and authorization of removal action. An important component of the remedial alternatives was to ensure habitat protection for the endangered mission blue butterfly (Icaricia icarioides missionensis). The site supports several stands of the silver lupine (Lupinus albifrons), upon which the butterfly depends on laying its eggs and which provides a source of leaves, shoots, and flowers for larval consumption during a critical stage in the butterfly’s lifecycle. Remedial alternatives were designed to avoid this unique habitat and to schedule remediation activities outside of the butterfly’s flight period.
Notable Accomplishments
- Completed EE/CA for a sensitive site within a national park
- Performed human health and ecological risk assessments
- Conducted food chain modeling to assess impacts to birds and mammals
- Determined the lack of suitable habitat for the California red-legged frog, avoiding unnecessary quantitative assessment
- Protected endangered mission blue butterfly habitat
- Developed remediation alternatives that balanced environmental cleanup with species and habitat conservation
