Project Management and Construction Supervision of Turnkey Contract for the Construction of BMA Stage-2 (Yannawa) Water Collection and Treatment Plant Project (Chongnonsee Water Environment Control Plant)

Project Name: Project Management and Construction Supervision of Turnkey Contract for the Construction of BMA Stage-2 (Yannawa) Water Collection and Treatment Plant Project (Chongnonsee Water Environment Control Plant)

Name of Company: Thai Engineering Consultants Company Limited

Name of Associated Firms / Services Performed / Participation Share :

- Thai Engineering Consultants Co., Ltd. Construction Supervision

Supervision of Operation & Maintenance

- Metcalf & Eddy International Project Management &Design Review

Location: Bangkok, Thailand

Client: Department of Drainage & Sewerage, Bangkok Metropolitan Administration

Project Cost: 4,552 Million Baht

Type of Service :

(1) Review of Contractor’s Design and Submittals

(2) Construction Supervision

(3) Supervision of 1 Year Operation and Maintenance

Project Description:

The BMA Stage-2 Project area consists of four districts namely Yannawa, Bangkholaem, Sathorn, and Bangrak, with a total area of approximately 28.5 square kilometers located in the south of Bangkok.

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The Scope of Works for the BMA Stage-2 Project consisted of:

1. Intercept all BMA drains before they discharge to the Khlongs and to construct an interceptor system with a capacity of five time Dry Weather Flow (5 DWF) to convey the collected sewage to the new Yannawa Sewage Treatment Plant (STP)

2. Treat all sewage at the new Yannawa STP, to be constructed on 13.2-hectare site, located on the left bank of the Chao Phraya River.  The STP will provide preliminary treatment for 5 DWF and secondary treatment plus nutrient removal for 1.5 DWF {2000,000 Cubic Meters per Day (DMD)}.  Planned expansions to the STP will double the capacity.  The STOP must also be capable of processing 1,000 CMD of sewage.

3. Perform the first-year operation & maintenance of the Yannawa STP.

The interceptor sewer system portion of the Yannawa Works Project comprises 51 kilometers of sewer pipe with diameters ranging from 150 to 2,250 mm. and three intermediate lift stations. The sewer pipes are laid at the depth of 4 to 17 meters from the existing ground.  Virtually all the sewers have been installed using trenchless construction techniques.  Earth Pressure Balance tunnel boring machines were used for the construction of sewer tunnel.

The wastewater treatment process is the Cyclic Activated Sludge System (CASSTM).  The treatment works is housed in a 4-storey building with the area of 38,000 sq.m. each storey contains 6 reactor compartments with dimension of 17.5 m by 60.0 m x 4.8 m deep.  The CASS System process has been designed to reduce the carbonaceous BOD level and also reduce nitrogen and phosphorus levels in the effluent through the biological nutrient removal (BNR) processes with backup system provided through chemical (alum) additions.

Pretreatment before the CASS System consists of the flow measurement, grit removal and fine screening of the wastewater.

Thickening and dewatering of the sludge from the treatment process is provided by the Combined Belt Filter Presses.

The construction of interceptor sewer system and sewage treatment plant is complete.  The sewage treatment plant is in full operation.

Due to the thick layer of soft soil condition along the bank of Chao Phraya River in the project area, special Ground Improvement Technique was required.  Cement Deep Mixing Method and Jet Grouting Method was chosen to increase in strength and decrease in compressibility of the soft ground resulted from the reaction of the clay with cement through the processes of (on exchange and flocculation as well as pozzolanic reaction.  Cement Slurry was vertically inject with the pressure of 10 ksc into the ground in the soft soil are.