Cambodia | Bakheng Water Production Facilities – PVD/Wick drains

The site presented complex ground conditions, with various challenging layers including backfilled sand, soft saturated clay, and hard sand. Menard’s PVD technology was employed to expedite the consolidation process, overcoming challenging ground conditions and strict timeline.

Project Overview

On November 2019, VINCI Construction Grands Projets signed a contract with the Phnom Penh Water Supply Authority to design and build the Bakheng water treatment plant in the northern outskirts of the Cambodian capital. The first phase of the project covers construction of:

• a first treatment line with a capacity of 195,000 cu. metres per day,
• the intake in the Mekong River with a capacity of 390,000 cu. metres per day,
• two 1.4 metre diameter pipelines with a length of 1.5 km to carry water from the Mekong to the treatment plant,
• a 2 metre diameter pipelines with a length of 7.8 km (including a 630-metre river crossing to be built using a Micro tunnelling machine) to bring drinking water to more than 500,000 inhabitants of the capital city.

The project, co-financed by the French Development Agency, the European Investment Bank, and the Phnom Penh Water Supply Authority, will employ more than 500 local workers and supervisory personnel at the height of activity.

The contract provides for a second conditional works phase. This phase is designed to double the plant’s treatment capacity to 390,000 cu. metres per day. Following handover of the second phase, the project will provide drinking water for a population of one million.

Ground Condition

Considering a 0m elevation equal to the project final level, the sub soil at site area is composed of:

• a first layer down to elevation -2 to -4m composed of sand backfilled material
• a second layer down to elevation -10 to -12m composed of soft saturated clay
• a third layer down to elevation -15 to -18m composed of hard sand
• a fourth layer down to elevation -27 to -44m composed of very soft to medium saturated clay
• the stiff ground

Menard Solution

To avoid deep foundations and speed up consolidation process due to sand back filling operations, PVD technology combined with sandy surcharge has been applied to mitigate long terms settlements. Mesh of PVD has been designed in accordance with the project schedule. Thus, a first grid of PVD has been designed to limit the consolidation period to 3 months under the 1^st phase of the project (critical path). A second grid of PVD, wider than the first one, has been designed to limit the consolidation period to 12 months under the 2nd phase of the project.

3 main challenges have been achieved on the project:

• Installation of PVD through a hard sand layer (3rd layer) without predrilling works
• Installation of PVD down to 37m depth
• Mobilization period in very limited timing and during worldwide Covid Crisis

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