Tunnel Business Magazine

JUN 2018

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Page 40 of 51

TUNNELINGONLINE.COM TBM: TUNNEL BUSINESS MAGAZINE // JUNE 2018 T U N N E L U P D A T E S 4 1 Los Angeles Purple Line Extension – Phase 1 Skanska/Traylor Bros./J.F. Shea JV (STS) The Westside Purple Line Extension Project is a 9-mile long project that consists of three sections that are being planned to be built and opened for revenue service before the end of the next decade. Section 1 is a 3.92- mile long subway alignment with three stations that is being constructed under Wilshire Boulevard in gassy ground and tar sands with prehistoric fossil deposits utilizing the design-build delivery method. TP for the $1.636 million design-build contract was issued on Jan. 12, 2015. Tunneling operations are planned to begin in mid-2018. The tunnel- ing operations will be staged through the shoring box of the Wilshire/La Brea Station excavation. The Revenue Service Date per the Full Funding Grant Agreement is Oct. 31, 2024. The scope of work includes 17,900 ft of twin-bore tunnel: Reach 1 is 9,600 lf between Wilshire/La Brea Station and Wilshire/Western etrieval shaft; Reach 2 is 4,400 lf between Wilshire/La Brea and Wilshire/Fairfax Stations; and Reach 3 is 3,300 lf between Wilshire/ Fair- fax and Wilshire/La Cienega Stations. There is also 600 lf of tail track to the west of Wilshire/ La Cienega Station wher e buried. The tunnel is 18-ft, 10-in. inside diameter with 12-in. thick precast con- crete lining. Depth varies from 40 ft and 100 ft. The alignment includes three stations and the western retrieval shaft and 23 cross passages. Tunnels are planned to be mined by two Herrenkne oss- passages are planned to be mined by the sequential excavation method using variety of localized ground support systems. Anticipated ground conditions include: Soft ground consisting of Pleistocene-age (San-Pedro) and Pliocene-age (Fernando) formations; Some alluvium deposits and arti- ficial fill areas above the tunnel; Tar sands comprise almost 25% of tunnel alignment; Expected water table up to 90 lf above tunnel crown; Presence of methane (CH4) and hydrogen sulfide (H2S) gases (tunnels are deemed "gassy" by OSHA). The project is 34% complete. Production of tunnel precast concrete Liners b ember 2016. er Herrenknecht has completed manufacture of e successfully conducted at the Herrenknecht factory in July. Delivery to STS yard was completed in December cheduled for August. Jet grout- ing of cross-passages b ember 2016. Wilshire/ La Brea Station excavation (tunnel launch point) began in July 2016 and invert concrete is nearly complete. Tunnel Designer: PTG/ WEST JV (Stantec/Jacobs). Engineering/ bcontr er: Herrenknecht; Precast: Traylor precast; Support of Excavation/piles: Con- don Johnson; Jet Grou olm Drilling; Geotechnical instrumenta- tion: Group Delta; Dewa etrench; Standpip en. Key Project Personnel: James Cohen, Executive Officer, Program A; Ashok Kothari, Project Director, WSP/Par- sons Brinckerhof e Smithson; (Traylor) uart, Jim Honeycutt. Los Angeles Regional Connector Transit Project Regional Connector Constructors (Skanska-Traylor JV) The downtown Los Angeles urban location of the Regional Connector provides challenges in the coordination with multiple third parties. The Regional Connector project will be the first tunnel subway project to con- nect three operating rails sy o Blue and Expo Lines on the West and the Gold Line on the East. When complete, transit riders will no longer need multiple transfers and can travel north-south and east-west on the same system. The tunneling portion of the $1.75 billion Regional Connector Transit Project for the L opolitan Transportation Author- ity involves 5,795 ft of twin tunnels with an excavated diameter of 21 ft. TP was issued July 7, 2014, with a forecast completion date of December 2021. The ground conditions range from alluvium soils to siltstone of the Fernando formation, with the potential for methane, hydrogen sulfide gas and boulders. The groundwater table is generally above the tunnel align- ment. Pressure balance tunneling u equired, along with precast concrete segments with double gaskets as the tunnel lining system. The tunnel depth (cover) ranges from 25 ft to approximately 120 ft and crosses b o Red Line heavy rail tunnels with less than 7 ft of clearance. The Regional Connector includes ap- proximately 2,100 ft of cut-and-cover and retained cut guideway, a 300 ft crossover cavern excavate chniques, and three cut-and-cover subway stations. The bored tunnels will be excavated concurrently with the three station construction, requiring coordination of cut-and-cover and tunnel excavation. The Little Tokyo/Arts District Station, located at 1st St. & Alameda St., excavation and invert concrete was completed in December 2016 and tunneling commenced from that location in February 2017. The first tunnel was completed on July 19, 2017. The was moved and relaunched for the second drive on Septemb ember 7, 2017, the tunneling crews set a project tunnel production record of 190 ft in one 24-hour day. The second drive was completed on Jan. 17, 2018, to the Flower Street cut-and-cover section wher - bilized. Excavation of the three cross passages between the two tunnels was complete ch 2018 and cross passage lining and tunnel invert placement is underway. The excavation of the 90 ft deep Historic Broad- way Station, located at 2nd St. and Broadway, is approximately 90% com- plete as preparations are being made for excavation and support of a 300- ft long cross over cavern at the east of the station using excavation techniques in the Fernando forma vern is expected to be complete by December 2019. Structural concrete placement is on-going at the Grand Ave. Arts/Bunker Hill Station, located at 2nd Pl & Hope St. Pile installation, utility relocation and decking are 85% complete on the 1,350 ft cut-and-cover section along Flower Street where hanging of utilities and excavation below the deck is approximately 40% complete.

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