The most common source of hydrocarbon contamination in excavation water is not historical ground pollution but active contamination from plant operating at the excavation edge. Every combustion engine on site, whether a pump, generator, disc cutter, or tower light, produces fuel drips and oil seepage. Those drips fall directly into the standing water below, and by the time dewatering begins, the water is already contaminated.

Placing a Green Rhino EnviroPad under the pump and any nearby plant before work starts intercepts those drips before they reach the water. The EnviroPad uses patented Neutroilize Smart Fabric Technology to convert hydrocarbons into a permanently solid, non-leaching state. Unlike a polypropylene absorbent nappy, which stores oil as liquid and releases it when moved or pressurised, the EnviroPad locks contamination in permanently. It also sheds clean rainwater freely, so it will not overflow in wet conditions.

The S6 Small (610mm x 460mm) is the correct size for a submersible pump, small generator, or tower light. Position it label side up, ensuring the pad extends beyond the drip zone on all sides.

Before connecting the pump, dip a Green Rhino Hydrocarbon Detection Strip into the standing water and move it gently for several seconds. The strip detects hydrocarbons at a concentration of 1ppm (one part per million), well below the threshold visible to the eye. If hydrocarbons are present, the strip changes from light blue to dark blue. Light flecking indicates low-level contamination. A full, immediate transformation indicates a higher concentration.

A clean result means proceed to Step 4 and pump without a filter. A positive result means proceed to Step 6 before dewatering, routing the discharge through a filter to bring the water to a standard appropriate for surface water discharge.

Testing before each dewatering session is best practice. The source and concentration of contamination can vary between sessions at the same excavation, depending on plant activity and ground conditions. At 100 strips per pack, the cost of testing is minimal relative to the cost of an EA enforcement notice.

Connect a layflat discharge hose to the pump outlet stub and secure it with a jubilee clip. Match the hose internal diameter to the pump outlet: 2-inch hose for the 2-inch outlet on PL080001 and PL080003, and 3-inch hose for the 3-inch outlet on PL080002.

The layflat hose lies flat when empty, unrolls quickly across the site without requiring fittings or supports, and firms up to a full round cross-section under water pressure. The polyester yarn construction is rated to 8 bar working pressure, significantly above the output pressure of the MAX submersible range. CMT Group stocks 2-inch hose in 50m (LFH250) and 100m (LFH2100) lengths, and 3-inch hose in 50m (LFH350).

Layflat hose is a discharge-side hose only. Do not use it on the suction side of a surface pump. Route the hose to the confirmed legal discharge point, either the dewatering filter in Step 6 if contamination was detected, or directly to the outfall if the water tested clean.

Once the submersible pump has reduced the water level to its lower operating threshold, a thin layer of water remains on the excavation floor that no standard submersible pump can remove. The MAX 230V puddle pump is built specifically for this final stage. Its flat base design positions the inlet ports as close to the floor surface as physically possible, draining the space to within 1mm of the ground level.

Unlike the 110V submersible pumps, the puddle pump runs on a standard 230V mains supply and does not require a transformer. It has no float switch and runs continuously once connected: connect to power when the submersible pump has reached its limit, and disconnect manually when pumping is complete.

Position the pump flat on the lowest point of the excavation floor. The 1mm drainage capability depends on the flat base sitting flush against the surface. The integrated swing check valve prevents drained water flowing back through the pump when it stops.