a b
c
Figure 3.3 : ( a ) Drainage module ( b ) Drainage Cell ( c ) Subsurface modules enclosed with geotextile and surrounded by clean river sand ( d ) Topsoil and close turfing .
d
Procurement and Construction of BIOECODS
Prime Cost Sum ( PCS ) is defined as a sum provided for specialist works or services to be executed by a nominated sub-contractor , a Government or a statutory authority , or for materials and goods to be obtained from a nominated supplier . The negotiation of an acceptable and agreed price for this specialist works is expected to be a lengthy and tedious process . For conventional contracts , the Superintending Officer may decide to change the execution of specialist works from Provisional Sum to PCS ( PWD , 2014 ). The procurement method for BIOECODS construction for both IPD Pasir Mas dan PULAPAS was placed under Provisional Sum .
The construction progress of this green technology drainage has been deterred by construction issues not normally encountered when dealing with typical drainage construction . The modification to the design , supervision
and construction sequence monitoring warrant expertise and experience in the supervision team . Therefore , the item ‘ BIOECODS construction ’ is recommended to be listed as PCS . Clash mapping is proposed to be the output during the final design stage of BIOECODS .
The construction of ecological swale is very simple and does not require highly skilled labour . The trench containing the enclosed module is backfilled with river sand up to the desired invert level . It is then topped up with a thin layer of topsoil to sustain vegetation growth . Finally , cow grass is turfed onto the depression to create the surface drainage , i . e . swale . The entire process involves very minimal machinery ( using a backhoe for digging of the trenches to lay a subsurface drainage conduit ). On a daily average , a team of four semi-skilled labourers can easily construct 60 to 80m length of the swale ( Chang et al ., 2018 ). The excavated trenches for drainage alignment may also serve as temporary drainage ( earth drain ) during the preparation of erosion
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