The broken down poly-modular drain. The key problem is that the drain has parted company with the concrete surround and imploded. It appears that several attempts have been made to resurrect the drain, a very expensive and unsuccessful exercise!

Some of the grates were also completely knackered.

A close up view of the broken poly-modular drain where the walls of the drain have imploded. We observe this problem occurring with many of these types of drains and is the reason THUNDAFLO is reinforced with a 5mm thick steel rim.

Breaking out the damaged poly-modular. A saw cut is made down each side of the broken poly-modular drain and then dug out.

The trench is dug to approx 150mm below the channel depth (200mm wide drain) taking into account the built-in-fall. Holes are drilled for the rebar stirrups

Rebar is inserted into the holes and cemented with expoxy resin

Rebar is tied to form stirrups. The bottom of the stirrups need to be about half the distance between the bottom of the channel and the trench bottom. 100mm Width, 50mm from the bottom of the channel & 200mm width, 75mm from the bottom of the channel

The THUNDAFLO is positioned using the Independent Positioning System (IPS) to adjust the height

Torsion springs can be attached to the bottom of the fibreglass rod to form a "foot" where soil conditions are unsuitable (either too soft or rocky) for the fibreglass rods to be hammered into the ground.

Adjustments to the height using the Independent Positioning System

The Fibreglass rods are trimmed to below the surface

The top torsion spring is engaged to prevent the system from floating during the concrete pour.

Poly is inserted into the frame to prevent wet concrete ingress into the channel and assist with screeing

Fibreglass rod is cut to length and the wedged between the frame and the side of the trench to firmly brace the system. A very flexible and effective method to ensure there is no movement while during the concrete pour.

Torsion Springs can be attached to the end of the fibreglass rods form a "foot" to brace against the side of the trench where there is no concrete pad.

Start of the concrete pour

Note how well the poly insert is preventing the ingress of concrete into the channel. A major hassle to clean if this should occur!

A Single concrete pour is made in two stages. The 1st stage is to the bottom of the channel and final stage is to the top. The is to mitigate upward hydraulic pressure (Blame that Archimedes guy for this hassle!) and prevent the system from floating.

Start of the finishing touches

Wet concrete everywhere... Note how well the poly insert prevents the ingress of concrete into the channel

Finishing off: The poly insert greatly assist in screeing the concrete

Poly insert removed, grates are inserted....

An entrance BP can be proud of... rock solid for many years