WorldWide Drilling Rescource

Environmental Monitoring by Thomas Kwader, Ph.D., P.G. WorldWide Drilling Resource ® Hydrogeologist Hurricanes Also Impact Shallow Water Well Supplies Near Coastlines As I sit here writing my monthly WWDR article, I am listening to the Weather Channel and following as Hurricane Dorian slams the Bahamian Islands on September 3, 2019, (also National Groundwater Protection Day). There is so much devastation occurring to the islands, structures, and most important, human lives. I pray for the best possible outcome, but the next few days will change these peoples’ lives forever as a result of the 180-mile-per-hour winds crawling over the islands at 0 to 7 miles per hour. I can’t help but also wonder about the impacts of the 15- to 20-foot storm surge inundating all of these islands and the im- pact it will have on their main supply of potable water, which is shallow surficial aquifer. There are some reverse osmosis facil- ities, but not enough to supply their needs. (I once helped design a shallow well system on Nassau, to provide a water source to reconstitute hydrated powders brought from the mainland to produce milk and fruit juices.) Geologically, the Bahamas are largely comprised of porous carbonate rock (seashells, coral, etc.). Seawater underlies the surface at a few feet, to less than 100 feet in depth. A storm surge from the ocean will flood the areas overlying this thin freshwater lens and contaminate the aquifer above drinking water standards. For example, the recommended MCL (maximum contaminant level) for chlo- rides in drinking water is 250 mg/L (mil- ligrams per liter) - which is exceeded when freshwater is mixed with 1% of seawater (19,000 mg/L chlorides). The only way for the aquifer to “freshen” or restore itself is from local rainfall over a long period of time, which will accumulate by gently percolating and “floating” on top of the saltwater. Some areas will take years to recover to pre-hurricane conditions. “The true value of our drinking water is real ized when the wel l has run dry” ~ Anonymous Tom Tom Kwader may be contacted via e-mail to michele@ worldwidedrillingresource.com 41 WorldWide Drilling Resource ® OCTOBER 2019 ENV The WorldWide SUPER MART™ has the best rates and coverage for your classified ad . Free online listing included! Contact Kathy (850) 547-0102 Kathy@ worldwidedrillingresource.com