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A Phase I Environmental Site Assessment in San Francisco

The Phase I Environmental Site Assessment or ESA, known to many as the most essential form of environmental due diligence, can vary in complexity and challenge when conducted in the City known for liberal nature and dynamic history.  San Francisco has historically experienced several great events of great change in regards to its development which increase the complexity in regard to historical research during the Phase I Environmental Report which Environmental Professionals in the Bay Area should be familiar with. The most notable and well known event was likely the 1906 earthquake, and the subsequent rebuilding of much of the city.  During this time, the basic infrastructure in regards to utilities was not quite in place.  Although present, natural gas lines were limited in their access to much of the city.   Additionally, many were somewhat used to the period heating technology of the day, which was comprised mainly of oil burning furnaces or water boilers.  These systems typically included a self-contained source of fuel storage, typically consisting of an underground storage tank (UST).  Although present, above ground storage tanks were likely considered in many cases to be bulky, and in the way of useful interior space.  Therefore many chose to maintain the known reliable source of heating during this period, which necessitated the installation of the heating oil UST.  The UST is always a central item of focus for the environmental consultant conducting a Phase I ESA. 

As in most other cities, conducting a Phase I Environmental Site Assessment in San Francisco typically begins with the Environmental Professional gaining an understanding and search of the Subject address, which can range depending on locale and age from a single number, to an entire range.  Once the address is clarified, a few inquires are made into the local regulatory agencies, most notably the San Francisco Fire Department (SFFD), the San Francisco Department of Building Inspection (SFDBI), and the San Francisco Department of Environmental Management, Local Oversight Program (LOP).  A major intention of this inquiry is not only to find the basics such as building age, size, and history of development, but to find the one and only underground storage tank (UST). 

Environmental Records Search in San Francisco

Finding a UST through a search of records can be hit or miss, however, the most luck from a blind research standpoint has generally been with the a review of records at the San Francisco Fire Department.  I have personally found a dozen or so of these historical USTs from reviewing records at this agency; however, the key is to make sure the records clerk, who may vary from a clerical aide to a light-duty fireman, is providing you with the correct file.  The SFFD is an interesting place to review files, as their research desk doubles as the permit review desk, where random citizens apply and/or attempt to convince officials of the safety of their proposed pyrotechnics.  Additionally, a large soil vapor remediation system is in place within the SFFD lobby, evident by the strong diesel odor when on the way through to a file review.  

The other agencies can be valuable as well, however usually when researching for supporting documentation for the presence or absence of the noted UST.  Subsurface investigation, tank removals and related closure records will typically be on file with the LOP, if ever performed.  However, even at the LOP, there are cases where known records go missing, so at this point its best to talk with a case manager, who are generally helpful.  A search of files at the San Francisco Department of Building Inspection (SFDBI) can beneficial as well, however, can become overwhelming when looking at a high-rise commercial building constructed circa-1900, as the range of available permits can become quite extensive.

Historical USTs can also be researched by a review of available Sanborn Fire Insurance Maps, which can be viewed for free at the University of California, Berkeley Map/Earth Sciences Room, or acquired through EDR.  In addition to finding USTs, Sanborns can be a valuable tool in deciphering the past use of the subject site.  For many sites in downtown San Francisco, Sanborn maps typically depict historical development as beginning with a horse stable and blacksmith/wheel right shop, followed by a large multi-story brick building, and following the 1906 earthquake, larger steel-framed high rise buildings, constructed mostly in the 1920s, which exist to this day.  Generally, a wide range of Sanborn maps are available for central down-town areas of the City, and less so the farther out.

Aerial Photos in San Francisco

Aerial photograph research can vary on usefulness as well, depending on where the site is located.  Within more congested down-town areas, development becomes difficult to decipher from the surroundings.  However in outlying areas, aerial research can be key to identifying a former gas station or industrial development.  A good source of local aerials is Pacific Aerial Survey, in Oakland.

Site Inspection in San Francisco

The actual site inspection can of course reveal many things about the Subject Property’s past.  Key points to looks for when assessing a typical older, post 1906 earthquake San Francisco property are: UST fill ports, generally located in sidewalk or street areas; and vent ports, which can be located along the building exterior, at grade level, or branching form the sidewalk or street surface, usually against the building.  A thorough assessment of the building basement, if present, will also be critical in determining the presence of prior or current UST(s).  Large concrete patches are a good indicator of a removed UST, and supply/vent piping leading to a vaulted feature is a good indication that the UST may potentially remain buried.


While the above may not be all the steps involved in the performance of a Phase I ESA, they are steps critical in conducting a Phase I Environmental Report specific to San Francisco.  Although redevelopment projects are a constant activity throughout San Francisco, and thousands of Phase I ESAs have previously been performed, many historical properties remain with their associated USTs intact, waiting to become discovered.

For more on San Francisco due diligence, check out my colleague Dean Andrews’ blog on engineering due diligence in San Francisco.