Controlling water ingress through a leaking dam overflow
In this case study, Oxford Hydrotechnics use advanced resin injection leak sealing techniques, to control significant water ingress, found to be leaking from a public lake, into the dam overflow chamber, through the dam structure itself.
Oxford Hydrotechnics were approached by St Helens Council to propose a solution to water ingress, that was leaking through a dam overflow structure. The dam structure was designed to work as a failsafe to ease periods of high water level within the adjoining lake, however, the dam structure itself was leaking, causing the lake level to remain lower than required. At the time of initial inspection, H2OX engineers estimated the leakage to equate to around 100 litres per minute.
Pedestrian barriers were used to cordon off the working area, enabling the footpath around the lake to remain open for the duration of the works.
In order to locate the source of the leaks within the structure, H2OX utilized a dye testing method, whereby an inert dye was injected into the foreshore plinth, at the face of the dam, through vertical drill holes. The dye was carried through the flow paths, emerging through the dam wall, allowing H2OX engineers to identify which drill holes were connected to the active leaks.
Oxford Hydrotechnics’ engineers’ solution was to then inject the structure with a hydrophobic resin. The resin would flow through the active flow paths, before expanding and curing to create a lightweight, permanently flexible, closed cell, foam. This foam would effectively shut off the leaks within the structure.
During resin injection, the flow of water was continually reduced.
As a result, in other areas of the structure, the leaks became active. This is symptomatic of treating the worst areas of water ingress, forcing the remaining leak water to find the next path of least resistance.
The process of resin injection was continued until all of the leaks had been addressed.
The smaller image above (top left) shows the conditions prior to treatment, with the larger, background image, depicting locations where the resin has emerged at the next exit point of the leaking flow paths, having travelled through the structure, and cured on the face of the dam. The additional cured resin was then simply removed by hand.
The view from the client
“We were delighted at the success of H2OX's work to seal a leak at the overflow structure in Taylor Park Dam.
The path around the lake is well used by visitors to this popular park.
Compared to our "traditional" method to excavate around the structure and use concrete and puddle clay as a seal, their method of drilling and resin injection was much less disruptive, we didn't have to close the footpath, and quicker - only 5 days on site. They were methodical, and the preliminary use of dye in the drill holes to find the leak paths meant the resin sealant was only placed where it was needed - a very economical method. You could see almost instantly the leaks stopping and the structure drying up.”
Brian Malcolm – St Helens Council