NATURE OF PROJECT: GROUNDWATER FLOW & TRANSPORT MODELLING TO ASSESS THE HYDROGEOCHEMICAL RESPONSE OF ENGINEERED BUFFER (CONDISOIL-BM) IN GROUNDWATER
CLIENT: INDUSTRY CENTRE OF EXCELLENCE (UNIVERSITY MALAYSIA PAHANG)
DURATION: OCT 2017 – FEB 2018
INTRODUCTION
Groundwater flow and solute transport modelling was conducted on site at FELDA Bukit Goh. The model was used to support an extensive investigation on the applicability of a residue formulation (Condisoil-BM) to be used as an alternative backfill and engineering buffer/soil conditioner for agriculture purposes. There are two main objectives for the groundwater modelling: (i) to provide information on groundwater flow characteristics at the site, (ii) to model the rate and transport of contaminants [Calcium (Ca) and Yttrium (Y)] that may leach from Condisoil-BM.
Figure 1: Aerial photo (Orthophoto) of study area. Red arrow indicates the excavated area for the emplacement of Condisoil -BM.
MODELLING OF THE SITE
Bukit Goh site is considered as hydrostratigraphic unit comprising one aquifer. Layer 1 (sandy clayey SILT/ silty CLAY) is the top layer. Average thickness is 9m. This is the layer of emplaced Condisoil -BM and the layer assumed to be the unit providing rainfall recharge to the underlying aquifer at Layer 2. The area of emplaced Condisoil-BM has dimensions: 25 x 25m, depth is from 0- 4.85 m bgl. Layer 2 (silty SAND) is the aquifer at the Bukit Goh site and 9m thick.
Figure 2: Four main hydrostratigraphic unit at Bukit Goh with one aquifer (Layer 2) and Condisoil-BM at the Layer 1 upper section
RESULT & DISCUSSION
The flow at the site generally trend northwest – southeast towards the direction of a local river located outside the boundary of the study area.
Figure 3: simulated groundwater head contours in the Layer 1 (sandy clayey SILT/ silty CLAY, Scenario II -after Condisoil-BM emplacement)
Figure 4: Transport of Ca contained within the Condisoil-BM location (Layer 1) after 7300 days (20 years).
CONCLUSION
Ca will reach the aquifer after 20 years (7300 days) under an assumption of zero sorption). The emplaced Condisoil–BM is relatively impermeable and able to restrain the movement of contaminants from reaching the groundwater zones.
