Dutra Dredging Company
There are unresolved queries regarding valves, the recent discovery that there are two existing pipelines across the channel and the very serious issue of stability at the Union Pacific Intermodal Site. This last issue is the focus of this letter.
Attached you will find copy of the Union Pacific's hired geotechnical firm, Shannon and Wilson, Inc., review of the proposed installation methods and their concern regarding slope stability.
As a result of the S&W report and my own visual examination of the the proposed area at Union Pacific where the pipeline would come up the slope, we engaged a local geotechnical firm to do a preliminary investigation of slope stability and potential solutions. The report from that firm, GEI Consultants, Inc., is also attached.
Our conclusion is that the best solution to the slope stability issue is to move the location of the sewer line at the Union Pacific site some 500 feet east of the present location. There is approximately 50' of open land from the existing rails to the waterline which could allow open cutting of trench without slope stability concerns.
This approach would require about 650 feet of additional pipe. While pipe cost would go up, that will be less costly than trying to solve a slope stability issue at the present planned location.
Because this issue is so sever and complex, we believe that we all need to put together a group involving the Corps, contractor, railroad and Port of Oakland to come up with solutions to the issues as we know them.
The time is rapidly approaching when the pipeline crossing could become a critical item. With that sense of urgency, we request assistance. We are willing to participate in any forum which will expedite resolutions.
If there are questions, please contact us.
Robert D. Johnston
August 8, 1996
Dutra Dredging Company
1000 San Pedro Road
San Rafael, California 94901
Attention: Mr. Bob Johnston, P.E.
Subject: Oakland Harbor Sewer Crossing Installation Alternative Sewer Alignment Commentary
Following our August 5, 1996 meeting with you and your Project Superintendent, Jeffery McWilliams, at the Union Pacific Intermodal Yard on the Oakland bank, we have reviewed the project information that your provided. The data included a copy of a July 24, 1996 letter from Shannon & Wilson to Union Pacific Railroad Company that contained comments on your proposed plan for installing the new sewer pipe under the railroad track and through the adjacent jetty rock fill. The Shannon & Wilson comments included the need for contingency plans because of the potential for undermining/removal of lateral support and loss of ground that could result in instability and/or settlement of the railroad tracks during the installation of the the proposed shoring system. They also questioned what would be done if large jetty rock prevented driving shoring members to required depths.
We agree with the expressed concerns and expect that the subsurface conditions at the site are not compatible with a risk-free installation as presently designed.
We understand that you may submit a proposal to relocate the sewer crossing further to the east, where the railroad track curves away from the waterfront, to avoid the risks of damaging or weakening the railroad track foundation at the design location. This alternative location would eliminate the need for the shoring to be installed in the jetty rock and would probably eliminate the need for any shoring on the waterside of the railroad track. The casing would still need to be jacked under the railroad track from a jacking pit. The jacking pit would be constructed the same as your present design, but oriented and located differently.
The additional space between the jetty and railroad track would allow the waterside excavation to have sloped sides that would not threaten railroad track stability and that would allow the jacked casing to emerge into the sloped excavation. This would eliminate the problems of getting the jacked pipe through a steel bulkhead and the related potential for loss of ground.
A sketch of this scheme is attached. Our sketch is a conceptual plan is not intended as a design or construction drawing. This alternative would add to the length of the pipe and would require a longer jacked section.
Thank you for asking GEI to assist you on this project. Please let us know if you have any questions about this letter or if we can be of further service.
GEI CONSULTANTS, INC.
ROGER FOOTT ASSOCIATES DIVISION
Roy A. Bell, P.E., G.E.
Attachment: Sketch of Alternative Oakland Harbor Sewer Pipe Crossing
SHANNON & WILSON, INC.
Geotechnical and Environmental Consultants
400 North 34th Street, Suite 100 [??]
P.O. Box 300309 [??]
Seattle, Washington 99103 [??]
206 632 6020 [??]
July 24, 1996 Union Pacific Railroad Company Engineering Services Department 1416 Dodge Street, Room 1000 Omaha, Nebraska 68179-1000 Attn: Mr. Kevan Ehrenreich [??] RE: SHORING REVIEW - INSTALLATION OF 20-INCH DIAMETER SEWER LINE, OAKLAND INNER/OUTER HARBOR, OAKLAND, CALIFORNIA We have completed our initial review of the geotechnical aspects of the above referenced shoring system. Documents provided for our review were an Executive Summary (2 sheets), Operation Plan (6 pages), Figure 1 (Oakland Bank Site Plan), figure 2 (Section E-E), and H-Pile/Plate Shoring Design Calculations (11 sheets). These were part of the report "-42-foot Navigation Improvements, Oakland Inner/Outer Harbor, Relocation of Navy Sewer Line, Permit to Construct Documentation for Union Pacific Railroad" prepared by Dutra Dredging Company (undated).
Based on this review, we offer the following comments:
Firstly, Sections A-A and B-B that are located on Figure 1 were not included in the package and secondly the construction sequence of these casings and sleeve(s) particularly with regard to the connection at the shoring wall were not described in the Operation Plan (OP). Section A-A and B-B along the slope are necessary for our review in order to evaluate the potential impacts of the excavation on jetty slope stability. A more detailed description of the construction sequence for installing the sewer line within the jetty slope should be included in the OP. Items to be covered include: excavation slopes, bedding for the 42-inch diameter steel casing, bedding material gradation, telescoping sleeve construction, backfilling the casing and trench, backfill material gradation, and description of the connection between the slope steel casing and the horizontal steel casing beneath the railroad tracks, including the drawings of the connection.
SHANNON & WILSON, INC.
Thomas M. Gurtowski, P.E.
TMG:TEK/dgwEnclosures: Figures 11 - Typical Slope Protection Design Cross-Section Figures 12 - Transition Zone Grain Size Distribution Recommendations Important Information About Your Geotechnical Report