HomeMy WebLinkAboutUtilities 2013-05-20 Item 2A - Update - East Marginal Way South Emergency Storm Pipe RepairCity of Tukwila
Jim Haggerton, Mayor
INFORMATIONAL MEMORANDUM
TO: Mayor Haggerton
Utilities Committee
FROM: Bob Giberson, Public Works Director
BY: Ryan Larson, Senior Engineer
DATE: May 17, 2013
SUBJECT: EMWS Emergency Storm Pipe Repair 11 -19 -12
Project No. 91241206, Contract No. 13 -036
Status Update
ISSUE
Status update of the East Marginal Way South (EMWS) Emergency Storm Repair 11 -19 -12 Project.
BACKGROUND
On November 19, 2012, a large sinkhole was created by a break in a 30 -inch storm water line on
EMWS just south of S 124th St. The pipe conveys surface water from the east fork of Riverton
Creek, as well as local drainage in the area near Group Health. The storm pipe is corrugated metal
(CMP) and is approximately 10' deep.
ANALYSIS
A contract with KPG was issued in April to design a permanent replacement for this failing pipe as
soon as practical. The design contract included potholing to determine the exact location of existing
utilities and a geotechnical investigation to determine soil conditions. These investigations have
revealed additional issues that must be dealt with during design and construction. The issues
include contaminated soils consisting of kiln dust, creosote, and petroleum hydrocarbons, a high
ground water table that will require the installation of dewatering wells during construction, and a
12" water main that will require relocation by Water District 125. KPG is looking at potential options
to reroute the pipe to avoid or minimize the impacts of these issues, but other costs such as traffic
impacts and required utility relocations could make an alternate pipe alignment unfeasible.
Staff had previously recommended that a portion of the EMWS repair occur this year to reduce the
possibility of another pipe failure and potential flooding. With the issues listed above, failure to
adequately address subsurface issues during the design process could lead to significant cost over
runs during construction and possible permit violations. It is now recommended that construction of
the EMWS repair be postponed until 2014 allowing sufficient time to properly design the
improvements, relocate impacted utilities, and ensure construction occurs in the allowed fish
window.
City maintenance crews will continue to monitor the pipe for potential failures until permanent
repairs can be made.
RECOMMENDATION
Information only.
Attachments: Consultant construction delay recommendation
W ,PW Eng,PROJECTS'A- DR Projects.EMWS Emergency Storm Pipe Repair 11 -19 -12 t91241206jIDesignllnfo Memo Status Update.doc
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