Thomson Line Construction: Into the Woodland

As promised in this update, we will be sharing more about the area around Woodlands South. The tunnel arrangement here will be one of the most complex along the entire line due to the configuration for reception tracks to the Mandai Depot in the vicinity. As such, the authorities dedicated the entire tunnelling works for both mainline and reception tunnels between Woodlands and SBAB to a sole contract - T206. Contract T206 will further interface with another 4 contracts (T201, T203, T205 and T207)

Aerial view of Mandai Depot

T201
Contract T201 consists of the construction and completion of the at grade Mandai Depot and a Bus depot. The Mandai Depot will include a rail administration building, stabling yard, test track and control room. The administrative building will house the OCC and DCC for the Thomson Line. A 66kV substation will be built to support the operation of the TSL. Presently, earthworks are still going on at the site. 3 reception tunnels will connect the depot to the mainline (1 to Woodlands, 2 to SBAB).

Mandai Depot

T203
Contract T203 is for the construction of TSL Woodlands station and the crossover tunnel that abuts south of the station. Woodlands station will be a 2-level civil defence (CD) station (TOR=104.00m) and will feature 5 new entrances (A,B,E,F,G). As part of the contract scope, the existing NSL station will be underpinned and A&A works will be required to construct the paid elevated linkway.

The site premises is currently undergoing extensive sewer diversion works, prominent to the south of the station where the new entrances will be. The site office has been completed and is situated to the north as mentioned in a previous post. The crossover tunnel will see 3 tunnel breakthroughs from T206.

Area of the existing NSL which will house the future elevated linkway

Overview of the main station box looking south. Crossover tunnel to be located at the junction at the far end.

T205

Contract T205 is for the construction of Woodlands South station. Woodlands South station will be a 2-level station (TOR=101.50m) and have 4 new entrances. Entrance A and C to the south will double up as vent shaft buildings. The site office is almost completed with minor interior fitting works to go. A Kobelco hydraulic crawler crane (painted teal) has actually arrived at the site already together with what look like silos waiting to be hoisted up. The station is possibly leading in progress along Stage 1 at this moment. Altogether, the station will see 4 tunnel breakthroughs from T206.

T206

Contract T206 consists of the construction of 10 bored tunnels from 3 main cut and cover structures - LS1, LS2 and SBAB. The site office is completed and positioned right beside LS2.

Launch Shaft 1 (LS1) will facilitate the 2 TBM launches that will bore Reception Track 3 (RT3) between Woodlands station and Mandai Depot. LS1 will eventually be converted into an escape shaft (ES1) and backfilled when tunnelling works have completed. LS1 is located beneath the existing Woodlands Dr 17. The road diversion is being worked on at the moment.

Launch Shaft 2 (LS2) will facilitate 4 TBM launches that will link the mainline tunnels between Woodlands and Woodlands South station. A cross passage will be integrated into the shaft before it gets backfilled. LS2 is located right beside LS1, on an empty field to the north. An existing Pedestrian Overhead Bridge (POB) along Ave 2 will be demolished to remove the piles that will be in the way of the tunnelling route. There will be 2 cross passages between the mainline tunnels between LS2 and WDL station.

Sembawang Airbase (SBAB) cut & cover houses the main integration between the mainline and reception tracks. The 550m long cut and cover tunnel is located at the south end of the RSAF SBAB, bounded by Woodlands Ave 12 and the SLE. SBAB will facilitate 2 TBM launches for the mainline, and another 2 will bore RT1 and RT2 to the depot. The northern launch shaft at SBAB will be the widest ever constructed in Singapore, surpassing the one at Ubi being constructed under DTL3. T206 will construct and handover the southern launch shaft to T207 for the tunnels to Springleaf. There will be one cross passage between RT1 and RT2 between SBAB and MDD.

A 2-level escape shaft (ES2) will be built west of SBAB along Woodlands Ave 12 to link all 4 tunnels (SB, RT2, RT1, NB)

Reception tunnels highlighted in red. Reception tunnels physically emerge between the mainline tunnels, however illustrated otherwise on the chart for simplicity