Investigation and Remediation at the Presidio of San Francisco

EKI worked for the Presidio Trust, a government corporation established by Congress to manage the reuse of the Presidio of San Francisco in a manner that preserves the scenic beauty and historic character of the area and allow for private financing and self-support of the Presidio as a National Park.

As a former army base, The Presidio was impacted by more than 150 years of military use. EKI worked with the Presidio Trust, National Park Service (NPS), Regional Water Quality Control Board (RWQCB) and Department of Toxic Substances Control (DTSC) to expedite the cleanup of contaminated soil and groundwater at the approximately 1,400-acre site.

The Presidio Trust’s primary concerns for the site centered around the need for site-wide risk-based cleanup levels for residential, recreational, and commercial users as well as for ecological populations, including threatened and endangered species. To address those concerns, EKI performed the following services:

• Prepared a Feasibility Study (FS) for 30 sites within the Presidio, including remediation cost estimates for several firing ranges and multiple landfills
• Investigated, prepared the Remedial Action Plan (RAP), prepared a remedial design and cost estimate, and oversaw the remediation of a former California Highway Patrol pistol range that included excavation along the firing line, backstop, and range floor; including protection of a historic battery structure beneath the backstop. EKI prepared a site-specific Removal Action Work Plan, construction plans and specifications, a preexcavation sampling plan, a completion report, and provided construction observation and management services during the work.
• Worked with a NPS historian and structural engineer to inspect the battery before and after the excavation and backfilling, and repair a steel door to limit vandalism to the internal portion of the historic battery. The construction phase that followed excavation and backfilling required extra coordination and planning to re-route a hiking trail and bike path during the project and to protect the historic battery structure beneath the backstop.
• Coordinated with the Presidio Health and Safety manager to review unexploded ordinance (UXO) procedures, in the event that any UXO was encountered. Because the trail closure duration was limited to specific days, EKI collected confirmation samples prior to excavation, allowing the contractor to dig to the preexcavation confirmation samples so when the excavation was complete, the excavation could be backfilled immediately.
• Investigated and evaluated several historical firing ranges, including a skeet and trap range, machine gun butt, and other ranges in which no significant impacts were identified. The project also included import of a specific sand for vegetation restoration.
• Worked with public information coordinators who kept the public out of the active work zones.

Outcome

Because of the major excavation and backfilling during the construction phase, the exact disposal characteristics were unknown. EKI set up the bid schedule to allow for variable amounts of soil being disposed of at different disposal classifications.  In this manner, the bid schedule allowed flexibility for the encountered soil classification.  Some items included in the bid were not used, providing the client with contingency for the work. The total disposal quantities were 410 tons Resource Conservation and Recovery Act (RCRA) waste requiring stabilization and 150 tons non-RCRA waste.  EKI played an integral role in removing waste from a portion of the Presidio while protecting historic battery structures in the process.