Terry G. Spragg & Associates first successfully demonstrated the practicality of using water bags in a towing test of a 25 foot diameter, 230-ft. long, 770,000 gallon (2,916m3) waterbag in Port Angeles, WA in 1990 using a modified towing system and bag fabric much weaker than has now been developed. These tests were conducted under contract with leading experts in marine design and industrial textiles at the Massachusetts Institute of Technology for bag fabric development and bag scale-model testing. These consultants have been involved in the project since at least 1989, and have completed mechanical behavior tests on fabrics at MIT (July 1992), towing and longitudinal stress tests on a scale model bag (July 1993), and stress tests of bag fabric with zipper attached (September 1993). Testing of continued design improvements have been in progress through 2001.
In 1996, this team successfully demonstrated the technology with a 100 mile voyage in Washington State that received media coverage around the world (see Media Coverage Track Record). These tests included establishing the efficacy of the "Spragg Bag" zipper system. This system allows multiple waterbags to be transported through the oceans in trains, leading to a more economic modularity of the system. Because of this modularity the success of a 1,000 acre foot (1,233,000 M3) delivery operation in California over the course of a 12 to 24 month test period will confirm the feasibility of delivering hundreds of thousands of acre feet or more to any California location. It will be simply a matter of adding more bags to the system just like railroad boxcars. Currently, there are two non-modular waterbag delivery systems successfully operating in the Mediterranean; one in Greece, and one between Turkey and Northern Cyprus. For the past two years, waterbag technology has been an existing and successfully operating technology, albeit delivering water on a much smaller scale than the "Spragg Bag" system is capable of transporting.
The patented zipper connection system of the "Spragg Bag" is the key to waterbag technology. All other technology needed to implement the"Spragg Bag" system requires only simple off-the-shelf technology. This system is capable of delivering sufficient quantities of water from Humboldt Bay to Monterey Bay by connecting waterbags in long trains using this zipper, just as railroad boxcars are connected in long trains with couplings. A zipper is the strongest, easiest, and quickest way to connect and disconnect fabric to fabric. The world's strongest zipper has been created in order to economically, environmentally, and easily solve the problem of moving large volumes of fresh water long distances through the oceans of the world.
CH2M-Hill, a worldwide engineering firm, has produced five special studies for waterbag loading and off-loading facilities under contract with Spragg & Associates. A water delivery system will consist of the following major parts: (1) shoreside facilities to handle water from the source (i.e., pump stations, water storage structures, etc.) and ocean pipelines to the offshore water-loading platforms; (2) water-loading platforms to fill the bags; (3) bag assembly facility to prepare and deliver empty bags to the water-loading facility; (4) transport system to tow full bags to a marshaling facility; (5) marshaling facility to assemble bags into towing strings for transport to delivery sites; (6) off-loading facility to remove water from the bags; (7) empty bag handling and transport system to rig empty bags for the return trip to the loading facility; (8) mooring and bag handling facilities in the vicinity of the off-loading facility, and (9) ancillary facilities, such as water filtration plants, booster-pump stations, pipelines to municipal reservoirs or wells, and ocean pipelines from the off-loading facilities.
The zipper, fabric, and tow system have all successfully withstood extensive stress and vibration tests of over 1,000 pounds per inch conducted by engineers at the Massachusetts Institute of Technology. The maximum strength of the fabric and zipper connection that has been developed for a bag train of fifty 4,500,000 gallon (approximately 17,000 M3) waterbags is over 10 times greater than the maximum bollard pull from a 4,300 HP tug capable of towing this fifty bag train. The zipper can be operated manually or driven remotely using a pneumatic, or radio controlled slider, both of which have been developed and demonstrated. (A sonar controlled slider is also planned.) This is the only remote controlled zipper ever created and demonstrated in the world. Bags can vary in size, depending on the loading and off-loading requirements, but would average approximately 43 feet in diameter by 500 ft. in length. Each bag of this size will hold approximately 4,500,000 gallons (17,000 M3)of water.
A unique method for linking the bags to one another has been developed and tested, including a revolutionary method for connecting the bags to the towing connection to the tugboat. The bags are connected end to end using a fabric sleeve zippered around the circumference at the ends of each bag. A string of as many as 50 bags in single file, several miles in length, or podded together like logbooms, can be towed by a single vessel. The zipper connection distributes the towing forces around the circumference of the bags. The maximum longitudinal load from the towing forces on a string of 50, 500-foot long bags is 79 pounds per inch around the circumference at the front of the lead bag. For a 43-foot diameter bag filled to 90% capacity, the static circumferential fabric load is 66 pounds per inch. For the same condition, the static longitudinal load is 44 pounds per inch. The fabric load due to towing is greatest at the front bag and is minimal at the rear bag. Coated fabric and a fabric connection system of special design and manufacture to meet the required specifications of a strength of over 1000 pounds per inch in both directions is used for the bags and interconnection skirts. Thus, the minimum strength of the fabric and zipper connection that has been developed for a 50 bag train is over 10 times greater than the maximum bollard pull capacity of the 4,300 H.P. tug. According to Laborde Marine, a 4,300 horsepower tug with a bollard pull of 110,000 pounds can pull a string of fifty bags, weighing 1,300,000 tons, at a speed of 3 knots. Such an arrangement could deliver over 700 acre feet (228 million gallons/850,000M3) of fresh water per trip. The key hydrodynamic fact is that each bag is "drafting" the one ahead of it so that the rear bags each have less than 10% of the drag of one towed alone. In many cases waterbag trains comprised of only five or less waterbags are economically viable.