Saipan is an island located in the western Pacific and is part of the Commonwealth of the Northern Mariana Islands. Here, the Commonwealth Utilities Corp. (CUC), in association with the United States Geological Survey (USGS), has been busy developing a plentiful and sustainable water supply for its inhabitants that meets 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 ensuring the vibrancy of the island tourism trade.
For the past 13 years, Numa distributor, Western Well Supply of Aloha, Ore., has been providing drilling tools, supplies and advice to various companies throughout the Pacific Rim. Recently, Western Well introduced Numa DTH products to the CUC for its clean water program. CUC typically has 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, which recommended the use of a Numa DTH hammer and bit in order to provide efficient drilling at an affordable cost. The CUC purchased two Numa 10-inch DTH hammers and two 12-inch bits for the tasks at hand. Numa’s 10-inch hammer is capable of drilling holes from 97⁄8 inches to 12 inches in diameter in vertical and horizontal applications. Developed for long life and fast penetration rates in hard rock conditions, the hammer is designed 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 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 backpressure conditions are very common in this part of the world.
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 1,000 feet, 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 2 hours of brackish water per day.
The main drilling project required the installation of more than 25 water wells throughout the central highland area of the island. Each hole was 12 inches in diameter, and some extended to a depth of 1,100 feet. In some instances, drilling continued through hundreds of feet 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 gallons to 100 gallons of water per minute, and a constant, 24-hour source of clean water.