Sent: Tuesday, November 27, 2001 3:50 PM
Subject: Incident at Islais Creek
Dear Mr. Lynne Brown-
It was good speaking with you yesterday afternoon. Here's what I've been
Able to find out from the Port's Harbor Engineer, Nita Mizushima and through an
Email from Ben Leung of Muni about the recent incident at Islais Creek. I will
forward any additional information to you as it becomes available. In the
meantime, if you need to contact me, please reply by email or call me at
Manager, Public Relations
Yes, it is a muni project. the project manager is Ben Leung and he can
be reached at 554 -2463. The contractor, I believe is Proven Management with
a subcontractor doing the tunnel boring work.
ProVen Management, Inc.
501 Cesar Chavez Blvd, Ste # 204 E
SF, CA, 94124
They are doing 3 ductbanks (I don't recall the diameter, but something in the order of magnitude of 48") called "trenchless technology". It allows them to install ductbanks without excavating a huge area (in order to go so deep). I believe that they were to be 10
meters below the bottom of the creek at the lowest point. The object was to
create a crossing of the creek for power needs. (115kv). MUNI's involvement is
simply because they need traction power crossing the creek for the future
Third Street Light Rail. They had also used the same technology to cross the
Mission Creek with no problems that I'm aware of.
The pavement subsidence (cave-in) at the north and south shore occurred
prior to the week of 11/19. There was a site visit w/ Phil Williamson and George
Roger to examine the subsidence. This subsidence occurred directly adjacent to the Muwekma Ohlone Sanctuary, at Islais Creek,
The SF Muni Third Street Light Rail Duct Bank Drilling site is currently staged at the Pier 80 Yard, and Amador Street on the North Side of Islais Creek.
There were only a few small 1 or 2 foot sinkholes at the sewer leak and quite a few sand spouts of secondary effluent outfall liquids bubbling up into the Muwekma Oholone Sanctuary.
When we excavated down to expose the pipe, for the record, there were no tests conducted to justify or conclude that underneath the outfall pipe, that the drilling of the duct banks were the primary cause of of the collapse of the outfall lines, although, the current analysis and opinions of the SF PUC SF DPW, and many of the Project Managers from the various Agencies associated with the accident, was in fact directly associated with the Muni Third Street Light Rail Duct Bank Drilling Project at Pier 80.
We did find some evidence that the leak at the joint may be due to a weak
joint. We are still examining the evidence and trying to determine the
cause of the leak., although current data does not support this theory.
They realized a bit later that they had ruptured the 60" force main
sewer that runs under the water along the north shoreline. Once they sent
divers down, they found that there was a void underneath the supports for the
main and that when this settled, the main moved and ruptured. They diverted the
flows the outfall end of the main to keep tides from washing back into their work started excavation to expose the area on Wednesday (and i believe they continued
round the clock to arrest the problem). MUNI was aware of the main and had
thought they had taken appropriate measures to avoid it.
The Port has remained on the side to offer assistance and to relocate
Equipment in the corporation yard, etc. The maintenance team has been checking in
with the on-site folks regularly to ensure that there is assistance is
on-the-ready, although no dialogue with the “ folks “ is on the public record at this time.
SF MuniEnvironmental was also asked to investigate the site both due to the sewer
spill as well as to verify that the pipeline that was exposed on the south shore
Was in fact an asbestos wrapped bunker oil line and to determine whether
Abatement measures needed to be taken.
We anticipate that SF MUNI will work with their contractors to remedy the
situation and are awaiting their report.
The community is concerned about the impacts to the Muwekma Ohlone Sanctuary.
The Muwekma Ohlone Sanctuary has received grants with the Port participating in the application process.
The park has not yet recieved a permit to enter, but we will continue to try our
utmost to support the park and enhance it in the long term.
This is also related the discussions being held regarding the Illinois Street Bridge, it's
location and the construction. The Port has been making efforts to work closely with this community as of late to try to resolve their concerns with the future Illinois
Street Intermodal Bridge
Manager, Public Relations
Tel: (415) 274-0488.