Boon Keng MRT station

The NEL, which was first proposed in 1984,^[2] received government approval in January 1996.^[3] Boon Keng station was among the sixteen NEL stations announced that March by communications minister Mah Bow Tan.^[4]

On 23 June 1997, the contract for the design and construction of Potong Pasir and Boon Keng stations and associated tunnels was awarded to a joint venture of Kumagai Gumi, Sembawang Engineering & Construction and Mitsui & Co. for $316.7 million.^[5] The contract included the construction of 1.8 kilometres (1.1 miles) of twin bored tunnels and 280 metres (920 ft) of cut-and-cover tunnels.^[6]

The station excavation required the demolition of 200 parking lots located at carparks serving Block 22 and Block 34.^[7] To mitigate the loss of amenities for residents, new replacement carparks were constructed in the vicinity of the affected blocks. The station's western diaphragm wall was constructed beneath Serangoon Road, necessitating several traffic diversions. Road metal decking was used to maintain overall road capacity during construction. Existing 230 kV electrical cables and cast-iron water pipes located along the site boundary had to be protected from damage and vibration, while pipes crossing the site were relocated by the Land Transport Authority.^[8]

Boon Keng station utilised a semi top-down construction method, whereby the roof slab was cast first, followed by excavation to the concourse level through large openings in the slab. The concourse slab was then constructed, incorporating openings for further excavation to the platform level. The roof and concourse slabs were used to support the diaphragm walls, reducing ground movement and minimising disturbance to nearby HDB blocks. This approach was more cost-effective than the bottom-up method, which would have required extensive steel strutting to support the diaphragm walls.^[9]

On either side of the station, earth pressure balance tunnel boring machines were used in ground geologically classified as Old Aluvium (deposited sediment).^[10]

Tunnelling between Boon Keng and Potong Pasir involved passing beneath shophouses along Serangoon Road, which were closely monitored for ground settlement. To minimise such risks, tunnelling was carried out continuously on a 24-hour basis rather than the original six-day work schedule.^[9] The tunnels also passed beneath Whampoa Canal and the Kallang River. At the request of the Public Utilities Board, a 50-metre section of the 25-metre-wide canal was reconstructed as a reinforced concrete canal above the tunnels.^[11] The station opened on 20 June 2003.^[12]

Boon Keng station serves the NEL and is between the Farrer Park and Potong Pasir stations. The station code is NE9.^[13] Being part of the NEL, the station is operated by SBS Transit.^[14] The station is located underneath Serangoon Road near the junction with Towner Road. Surrounding landmarks include Bendemeer Wet Market & Hawker Centre, Kallang Community Club, Central Sikh Temple, Kallang Neighbourhood Police Post.^[15] The station is named after Lim Boon Keng, a Chinese doctor. ^[16]

Like most NEL stations, Boon Keng is a designated civil defence shelter.^[17][18] It is designed to accommodate at least 7,500 people and can withstand airstrikes and chemical attacks. Equipment essential for the operations in the Civil Defence shelter is mounted on shock absorbers to prevent damage during a bombing. When the electrical supply to the shelter is disrupted, there are backup generators to keep operations going.^[19] The shelter has dedicated built-in decontamination chambers and dry toilets with collection bins that will send human waste out of the shelter.^[20]

The station has accessibility features. A tactile system, consisting of tiles with rounded or elongated raised studs,^[21] guides visually impaired commuters through the station,^[22][23] with dedicated routes that connect the station entrances to the platforms or between the lines.^[24] Wider fare gates allow easier access for wheelchair users into the station.^[25][26]