Horizontal Drainhole Drilling (HDH Drilling) is a unique method of drilling that is commonly used for lowering the pore pressure of slopes particularly in the mining industry. Our specialized rigs are designed to drill into these slopes at a multitude of angles. Commonly the angles are between positive 1 and 7 degrees. These HDH’s are often drilled at depths between 25 and 500m. Once the holes are drilled atmospheric pressure is now brought to all of the internal structures along its path. This immediately starts depressurizing these zones and can be easily monitored with instrumentational holes like piezometers. Any intercepted water in these holes is encouraged to drain out to the surface due to positive angle of the hole. These horizontal wells are very easily maintained since no pumps are need to expel the water which means no utilities need to be run to these holes. The drains function year after year with little to no maintenance required. Often these holes are lined with a perforated PVC to keep from losing the inside annulus of the drill hole caused by sloughing or minor shearing. Surface casing can be installed to protect the collar of the hole from rock fall or damage from passing by equipment. One other common task is grouting off the surface casing. In this application grout is injected between the outside of the PVC and the inside of the steel casing. Historically we have seen volumes of water being drained from these holes in the ranges of 1 lpm to 4500 lpms.
HDH drilling can benefit many different work sites. These drains are commonly found on mine sites and along highways and railways. Even farmers have used these drains as pump free wells to irrigate their pastures.