Saipan is an island located in the Western Pacific and is part of the Commonwealth of the Northern Mariana Islands. Here, the Commonwealth Utilities Corporation, (CUC) in association with the United States Geological Survey (USGS) has been busy developing a plentiful and sustainable water supply for its inhabitants that meet the Federal Clean Water Act. The goal of the program is to develop a sound water supply that is critical for the well being of the inhabitants as well as insuring the vibrancy of the island tourism trade.
For the past 13 years, Numa distributor, Western Well, has been providing drilling tools, supplies and advice to various companies throughout the Pacific Rim. Recently, they introduced Numa DTH products to the CUC for their clean water program. CUC has typically used tricones over the years to drill water wells but has encountered very poor performance when faced with ground conditions consisting of rock and other hard formations.
The CUC consulted Western Well who recommended the use of a Numa DTH hammer and bit in order to provide extremely efficient drilling at an affordable cost. The CUC purchased two Numa 10″ (254 mm) DTH hammer and two 12-inch (305 mm) bits for the tasks at hand. Numa’s 10″ hammer is capable of drilling holes from 9-7/8 to 12 inches (251 – 305 mm) in diameter in vertical and horizontal applications. Designed for long life and fast penetration rates in hard rock conditions, the hammer is perfectly suited for completing water wells, rock sockets, caissons, foundation holes, elevator shafts, exploration drilling, blast holes or any other rock drilling project.
The CUC used Gefco Speedstar 25K and 30K drill rigs with on-board 900/350 (425 l/sec / 24 bar) compressors for the drilling of the water wells throughout the island. The ground condition in much of Saipan consists of formations of clay, limestone and volcanic materials. In addition, difficult high back pressure conditions are very common in this part of the world. On many occasions in the Pacific Rim, competitive hammers could not drill against the tremendous back pressures that were commonly encountered. With this in mind, the contractors selected the Numa hammers due to its reputation for handling the most demanding drilling situations including very high back pressures and based opon the outstanding service and support Western Well had provided.
In advance of the main project, the Numa hammers were used to drill deep exploratory holes in the central highlands on the island to see if significant water sources existed. Many of these holes were drilled to depths of more than 1000 feet (305 m) which are the deepest ever drilled in the Mariana Islands, including Guam. More importantly, however, the test holes indicated that a significant saturated thickness existed that may prove to be an important new fresh water source for west coast villages that presently receive only two hours of brackish water per day.
The main drilling project required the installation of over 25 water wells throughout the central highland area of the island. Each hole was 12 inches (305 mm) in diameter and some extended to a depth of 1100 feet (336 m). In some instances, drilling continued through hundreds of feet (metres) of water. This proved to be no challenge for the Numa DTH hammers and bits as they quickly drilled each hole with no incidence of downtime due to product issues. Once complete, the wells produced from 80 to 100 gallons of water per minute (303-379 litres/minute) and a constant 24 hour source of clean water.
From the very start of this project, the CUC quickly realized the benefits of the DTH method as they achieved significant increases in their production. The Numa hammers were able to triple the output typically provided by tricone methods and at a much lower cost per foot. The choice was clear to the CUC that the Numa hammers were the right product for their needs as the hammers and bits were able to drill faster and longer than the tricone method previously used. Based upon this success, the Numa hammers are now considered an indispensable part of the cooperative CUC/USGS exploratory drilling program.
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