Water Resources Consultant; Hydrogeology; Wellfield Siting, Design and Construction; Geophysical Well Logging and Interpretation; Aquifer Performance and Water Quality Testing; Heat Exchange Cooling System Project; Lynden Pindling International Airport Improvements, New Providence Island, The Bahamas:
The Lynden Pindling International Airport (LPIA) is located in the central part of New Providence Island and provides local and international air travel connections. LPIA is the busiest airport in and main international gateway to The Bahamas. In 2009 the airport was expanded. The airport expansion included the addition of a new building that handles passenger traffic traveling to and from destinations within The United States of America.
Is tourism important to The Bahamas? Absolutely! The economy of The Bahamas is almost entirely dependent on tourism. Tourism provides an estimated 60% of the gross domestic product (GDP) and employs about half the workforce there.
What is Heat-Exchange Cooling?
Energy costs are significantly higher in The Bahamas compared to those in the US. So, alternative sources to traditional energy supply are vital to the viability of projects that would otherwise be cost-prohibitive. This is where heat-exchange cooling comes into play.
The most cost-effective way to cool the towering buildings, like those at LPIA in The Bahamas, is through heat-exchange. This process takes large quantities of groundwater and passes it through a heat exchanger to transfer the cooling capacity of the groundwater to air handlers. The cool air that is then circulated through the building. Pretty cool, right?
Groundwater is generally colder with greater depth below land surface. At this site, the groundwater is a constant temperature of 69 to 70 degrees Fahrenheit at the inlet depth of each water well that provides water for heat-exchange cooling. The colder the water, the better the heat exchanger can work!
Our water resources Services
Sentinel Drilling of The Bahamas, Ltd. subcontracted us as the project water resources consultant to The Nassau Airport Development Company (NAD). We were the Hydrogeologists for the LPIA expansion project from planning and design through implementation.
Our services included assisting with the design and testing of groundwater wells for the heat exchange system. Pump tests were performed on each water supply well at the site to determine their specific capacity. Geophysical well logging was conducted to determine the aquifer and lithologic formation characteristics. Water quality testing was included in our scope of services to verify the water quality would meet the heat-exchange system design parameters.
The wells at the site include two production wells and two return wells. The groundwater production wells remove groundwater at a depth of 320 to 400 feet below land surface and are each 12” in diameter. The groundwater return wells are open from 200 to 300 feet below land surface and are located northeast of the production wells. The return wells are also 12″ in diameter.
The Bahamian Freshwater Lens
Our services included determining if the groundwater withdrawals would have an adverse effect on the surficial Bahamian Freshwater Lens. The freshwater lens is a valuable resource that the local government would like to preserve. It’s a near-surface layer of freshwater that sits on top of the underlying groundwater that’s actually sea water directly connected with the ocean.
The freshwater lens present in the subsurface on New Providence Island is aerially extensive and used locally as a water source tapped by private wells. The freshwater lens is recharged by the infiltration of rainwater, as rainfall at this location exceeds the local evapotranspiration. Infiltration, precipitation and evapotranspiration are components of the hydrologic cycle. The hydrologic cycle, or water cycle, describes the continuous movement of water that flows from the atmosphere to below land surface, including the oceans and other water bodies.
Generally, the geometry of the lens is such that it is thickest in the central part of the island, and thins toward the coast. The freshwater lens is between 20 and 50 feet thick in the area of the airport. The water conductivity analysis performed as a run of the geophysical logging equipment confirmed the thickness.
Results
Large-scale pump tests were performed to assist in determining each well’s specific capacity and if the new groundwater withdrawals at the airport would affect the freshwater lens. Water levels were monitored in the shallow and deep aquifers during the pump tests. Our seasoned professionals complied and analyzed the information. The analysis determined that there does not appear that an impact to the freshwater lens will occur through the use of the groundwater wells at the airport.
The deep aquifer is very porous, and the groundwater wells installed at the site have a large capacity to produce groundwater for the intended use. Additionally, the groundwater return wells installed at the property are designed to assist in eliminating impacts to the shallow freshwater lens. The return wells provide discharge of the heat-exchange discharge water to the aquifer at a shallower depth than the production wells, helping to block effects to the shallow freshwater lens.
closing
It is always a pleasure to work with the people of The Bahamas. This complex project is an excellent example of our capabilities as a water resources consultant. From project design through construction, testing, and implementation, our services helped preserve the natural beauty of New Providence Island.
If you ever fly into The Bahamas think of us as you stroll through the modern Lynden Pindling International Airport!
Please contact us if we can be of assistance on your future water resources project needs.
