Clean Water Reservoir Lining with SOLMAX Geomembrane

Background: Why Concrete Is Not Enough

This strategic project is located in the Kalimalang area of East Jakarta. Covering roughly 11,762 m2, its main mission was clear: a clean water reservoir lining that forms an absolute waterproof layer (waterproofing barrier) to safeguard the quality of drinking water for the wider community.

At the start, the reservoir already looked tidy because it was lined with solid concrete. However, by the standards of a modern Water Treatment Plant (WTP), relying on concrete alone is not enough.

Concrete is naturally porous (it has microscopic voids) and prone to hairline cracks caused by ground movement (differential settlement) and thermal expansion. If the reservoir were left with only a concrete layer, the risk of water leaking out (seepage) would be very high, resulting in a loss of clean water volume. Cracks in the concrete also open a path for contaminants or minerals from the ground to enter and degrade the purity of the water in the pond. An additional, 100% impermeable lining system was therefore needed.

Technical Solution: SOLMAX & Geotextile Combined

To meet this challenge, PETRA recommended and installed a double lining system using premium geosynthetic materials.

As the primary waterproof layer, we used 1 mm thick SOLMAX HDPE Geomembrane. Choosing SOLMAX High-Density Polyethylene (HDPE) was no accident. The material has a very dense molecular structure, making it highly resistant to chemicals and UV radiation, with outstanding tensile strength and elongation to withstand water pressure without tearing.

Then, for maximum hydraulic protection, 500 g Non-Woven Geotextile was applied on top of the geomembrane. This heavy geotextile plays a crucial role as a protective cushioning layer. It prevents direct abrasion that could damage the geomembrane, distributes the hydrostatic load of the huge water volume evenly, and protects the liner from mechanical damage caused by elements above it.

Technical Installation Steps on Site

Working on an area of approximately 11,762 m2 requires precision and a systematic method. These are the technical installation steps carried out by PETRA’s expert team in Kalimalang:

1. Surface Preparation (Subgrade Preparation):
   The team made sure the entire concrete surface was completely clean and free of sharp gravel, leftover rebar tie wire and protrusions (spalling) that could puncture the geomembrane.
2. Panel Deployment (Deployment):
   1 mm SOLMAX HDPE rolls were deployed with heavy equipment, very carefully so as not to scratch the material surface. Panels were positioned precisely with a minimum overlap of 10-15 cm at the seams.
3. Automatic Welding (Welding Process):
   This is the heart of any waterproof lining installation. Our technicians used automatic Hot Wedge Welder machines for flat, straight areas. The machine melts both overlap surfaces of the geomembrane at a specific temperature and fuses them permanently under roller pressure. The process produces a double-track seam with an air channel in the middle.
4. Non-Woven Geotextile Installation:
   Once the geomembrane was fully installed, 500 g Non-Woven Geotextile was spread evenly on top. The geotextile seams were then joined by heat-bonding or sewing so they stay locked in place and do not shift when water starts flowing into the reservoir.

Strict Quality Testing

PETRA leaves no room for error (zero tolerance for leakage). Every double-track seam on the SOLMAX HDPE was tested with the Air Pressure Test method. Pressurized air is injected into the channel between the two weld tracks. If the pressure stays stable and does not drop for the specified duration (for example 5 minutes at 30 psi), the seam is declared 100% watertight and passes inspection.

Final Result: Maximum Protection of Water Quality

The combination of world-class SOLMAX geosynthetics and PETRA’s rigorous installation transformed this state-owned enterprise (BUMN) reservoir in Kalimalang into a much safer and more efficient water storage facility.

The tangible results of the project include:

• Water Quality Fully Protected: The risk of cross-contamination from the soil into the clean water pond has been completely eliminated.
• Water Volume Retention: Leakage through porous concrete has stopped, so the clean water volume is maintained without any waste.
• Long-Term Investment: With SOLMAX HDPE durability lasting for decades, the state-owned enterprise can significantly reduce its infrastructure maintenance cost in the future.