In certain parts of England the treated potable water is stored in underground reservoirs prior to being distributed to homes and businesses. These underground tanks are typically constructed of concrete or brick/block with a concrete reinforced roof. The land above these reservoirs is used for purposes such as farming which includes the use of fertilizers and chemicals. Constructed 30 to 40 years ago, the concrete roofs of the reservoirs have become porous potentially allowing dirty rain water and farming chemicals to penetrate the concrete and enter the drinking water. The customer was looking for an effective long term solution of sealing the reservoirs that did not require rebuilding or taking them out of service.