Challenges and Opportunities with Removing a Former Gas Holder in a Residential Neighborhood
Challenges and Opportunities with Removing a Former Gas Holder
in a Residential Neighborhood
Presenter: Gina Plantz (Haley & Aldrich, Inc.)
Author: Gina Plantz and Angela Olguin (Haley & Aldrich, Inc.), Adrienne LaPierre (RPS Iris Environmental)
Since 2010, the Pacific Gas and Electric Company (PG&E), under the oversight of the California Department of Toxic Substances Control, has been conducting a voluntary program for investigating and remediating impacts from three of their former MGP sites in San Francisco. Like many former MGP sites, historical operation records are limited and after the MGPs ceased operating, the land on which they stood underwent significant redevelopment. The former footprints are now densely populated neighborhoods which consist of mainly single and multi-family residential homes. One of the properties within one of the former MGP footprints was previously a retail gasoline station which stopped operating in 2008 and has been vacant since that time. During the operation of the former MGP (1891-1905), this property was home to the subsurface 250,000 cubic foot relief gas holder. This property is in a prime location for residential development and it was purchased by a redevelopment company with plans to build a four-story condo building with underground parking. PG&E’s team worked with the property owner to understand the redevelopment plans to develop the applicable remediation approach. The former gas holder was still present in the subsurface starting at about 2 feet below ground surface (ft bgs) and the slab was present at about 18 ft bgs. This presentation will discuss the challenges and best practices developed during remediation and excavation of a former gas holder in a downtown residential setting, including: • Developing measures to successfully mitigate odors and emissions as close as 20 feet to residential condos. This included solidification of highly impacted soils before excavation; • Compliance with very low ambient air action levels and understanding non-site related sources in the area; • Working with the property owner to meet redevelopment needs and schedule; and • Proactive communication and engagement with the oversight agency and the community.