For our November meeting, we were fortunate to have Dr. John Cherry, from the University of Waterloo, speak on "Anatomy of Chlorinated Solvent Plumes in Sandy Aquifers."

Dr. Cherry presented detailed transects illustrating the internal concentration morphology of chlorinated solvent plumes in relatively isotropic and homogeneous sandy aquifers. The plume transects were based on intensive research monitoring and very closely-spaced samples. The general observation was that plumes consist of relatively small, high-concentration cores, and relatively large, low-concentration fringes. Plume cores can have cross-sectional areas as small as a few square feet.

The morphology of plumes has significant implications for the interpretation of typical cost-constrained groundwater contaminant concentration monitoring results. The apparent distribution of chemical concentrations in a plume may be inaccurate due to random sampling of "core" and "fringe" areas within a plume. This random component in reported concentrations results from sampling at a relatively coarse spatial scale relative to the variations in concentration within a plume. An understanding of the morphology of plumes should improve (or at least restrain and qualify) our interpretation of groundwater quality data.

The speakers for our January meeting were Steve Morse and Linda Spencer from the San Francisco Bay Regional Water Quality Control Board. Steve Morse is chief of the SF Board's Toxics Cleanup Division and is responsible for programs for the cleanup of soil and groundwater contaminated by fuel and non-fuel spills and leaks. Linda Spencer is the lead engineering geologist in the SF Board's Planning Division and chairperson of the Groundwater Committee.

For 1997, the SF Board will continue its strong emphasis on closure of fuel leak sites, utilizing draft State Water Resources Control Board fuel leak policy proposed in late October 1996. SF Board staff view the State draft policy as an extension of their current policy. The draft policy is a tiered risk-assessment/management approach, but it is not ASTM RBCA. It is a "stand-alone" policy and is independent of SWRCB Resolutions 68-16 (Statement of Policy with Respect to Maintaining the High Quality of Waters of the State), 88-63 (Sources of Drinking Water), and 92-49 (Policies and Procedures for Investigation and Cleanup and Abatement Under Section 13304 of the Water Code). A key element of the policy is the distinction between "low risk" and "non-low risk" sites. This policy is expected to simplify site assessments, site investigations and tank removal requirements. It should reduce corrective action costs by allowing for natural attenuation of petroleum hydrocarbons. This draft policy is expected to see minor revisions by the SWRCB with public comment on the policy and Functional Equivalent Document beginning early February 1997.

SB562, the Underground Storage Tank Cleanup Fund Program became effective January 1, 1997. This bill makes changes in the way program funds may be used and how fuel tank owners and operators are reimbursed for cleanup costs.

For non-fuel sites, the SF Board will continue with a site-by-site approach and will be receptive to Containment Zone applications for appropriate sites. Innovative approaches, such as "Brownfields," economic resource valuations, and Prospective Purchaser Agreements, also will be considered. The use of risk assessment/management will be encouraged as a basis for better decision making.

The "Containment Zone" policy, an amendment of SWRCB Resolution 92-49 was adopted October 1996 and approved by the Office of Administrative Law on January 13, 1997. In the past, the Regional Board has enforced the investigation and cleanup and abatement of sites under Resoultion 92-49. The Containment Zone policy will require the Board also to manage and contain sites that cannot be cleaned up.

Where appropriate, SF Board staff encourage qualified potential sites to complete a site investigation and risk assessment, evaluate source reduction and corrective action, and submit a partial application for Containment Zone status. After a preliminary screening of initial applications, Board staff will work with the applicants to continue the process (public notice, notice to technical advisory committees, development of site cleanup requirements, negotiate written agreement with property owners, RWQCB SCRs adoption hearing, and submission of site information to the SWRCB).

SF RWQCB projects for 1997 include the following:

An economic analysis of groundwater basins using methods of decision science. Basins to be evaluated and compared include downtown San Francisco, the Niles Cone, and Santa Clara by the airport.

An investigation of beneficial uses of groundwater in the East Bay Plain Basin.

The next San Francisco Bay branch meeting will be held on Tuesday, March 11 and will feature a presentation by Jack Peabody of Regenesis on the injection of Oxygen Release Compound (ORC) for bioremediation.

For our May meeting we have invited Dr. Tanya Atwater to speak on the regional tectonics of California and the formation of groundwater basins. This will be a joint meeting with AIPG. Check the GRA Internet home page or call to confirm speaker and date.

For reservations, contact David Abbott at Todd Engineers in Emeryville: (510) 595-2120.