Meeting_Body
CONSTRUCTION COMMITTEE
MAY 20, 2021
Subject
SUBJECT: WESTSIDE PURPLE LINE EXTENSION SECTION 1 PROJECT
Action
ACTION: APPROVE RECOMMENDATIONS
Heading
RECOMMENDATION
Title
CONSIDER:
AMENDING the Life-of-Project (LOP) budget by $150,000,000 for the Westside Purple Line Extension Section 1 Project (Project) from $2,978,879,593 to $3,128,879,593 using the fund sources as summarized in Attachment A, consistent with the provisions of the Board-adopted Measure R and Measure M Unified Cost Management Policy (Attachment B).
Issue
ISSUE
As outlined at the August 2020 Board meeting, Section 1 is being constructed in complex and extremely challenging geologic conditions that include subsurface gases (methane and hydrogen sulfide) and asphalt saturated ground, or "tar sands" in the areas surrounding the La Brea Tar Pits. The presence of these soil conditions previously prevented tunneling in this area until more technological advanced tunneling methods were developed. Metro tunneling specialists worked with federal representatives to have legislation changed in 2006, so that subway alternatives could be considered.
In addition to the above natural geologic challenges, Section 1 also faced man made underground obstacles. Old, abandoned oil wells were located along the alignment. Since their precise locations were not known, additional investigations and efforts were implemented to insure there were no incidents involving the Tunnel Boring Machines (TBMs) and these wells. Such an incident could cause damage to the TBMs or an unplanned release from the oil wells. Horizontal Directional Drilling (HDD) in combination with the use of a Magnetometer (a first of its kind of operation) was implemented to search for the abandoned oil wells and any other metal objects (anomalies) that may be in or very close to the tunnel alignment. Section 1 did find both abandoned oil wells and other metal objects that would have impacted the tunneling operation...
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