WorldWide Drilling Resource

19 WorldWide Drilling Resource ® JUNE 2015 Environmental Monitoring by Thomas Kwader, Ph.D., P.G. Groundwater Recharge Wells - A Good Solution? Anyone involved with water supply issues knows many areas throughout the U.S. and, for that matter, the world are experiencing historic water level declines in our reservoirs and aquifers. One solution is to take water from lakes, creeks, and rivers during seasonally high rainfall periods and inject this water into declining aquifers. Although this seems a grand idea at first, there are some things to consider. Let’s first define a few methods for recharging an aquifer. 1. Inner Borehole Flow - In some areas it is illegal to construct a long borehole connecting multiple water- bearing zones in an open hole or extended screened interval. Multiple confined aquifers will often have dif- ferent static water levels and possi- bly different water quality. Connecting these zones will decrease the pres- sure in the aquifer of higher head and contaminate the receiving aquifer of higher water quality. There have been many cases where contami- nated shallow aquifers have contami- nated deeper drinking water aquifers through an abandoned well. These wells may continue to contaminate, unknowingly, for years into the future. 2. Surface Water Drainage Wells - These are wells usually in lakes or man-made ponds meant to pre- vent flooding in low lying areas. A half-century ago this was a popular, inexpensive way for city and county road departments to control flooding. These wells are generally illegal because of the uncontrolled, wide variety of contaminants allowed to be directly drained into our pristine aquifers. Surface water contaminants can include stormwater carrying col- iform, petroleum products draining from roads and parking lots, nutri- ents and pesticides from lawn and agricultural chemicals, metals and chlorinated solvents. Once these chemicals reach the aquifer, very little if any degradation of these compounds takes place, traveling very long distances in many cases. 3. Properly Constructed Recharge Wells - Aquifer recharge can be conducted in a sound, safe manner which can help restore groundwater levels in areas where groundwater “overdraft” has occurred. For ground- water recharge to be successful, the mixing waters must be physically, chemically, and biologically (free of organisms) compatible and meet the minimum drinking water standards. If a recharge well is proposed, it is suggested that compatibility tests be conducted to ensure the mixing of the waters will not create a prob- lem which may be too costly to fix or remediate after the recharge sys- tem is up and running. Tom Tom Kwader may be contacted via e-mail at michele@ worldwidedrillingresource.com "0",-" - 0 &' '" &) (*-. -&2"- )! )/( ", *# ' !"- )/( ", *# ' !"- "1 -"! &.- *'" +")",- , $ &.- &)$- ((",- ((", &.- &0",.",- " .&++&)$ . &'&2",- ' 1 &.- &+" &+"- *'. *) "".% / - * &'" &. *&) ,*! %*.( &' *( 111 &. *&) /-