New Directions for Improvement of Groundwater Quality

Well installation and seal construction techniques that are widely accepted may not be working as designed. The importance of isolating the primary producing aquifer cannot be stated strongly enough - an effective seal above and below the aquifer needs to be established. Without a good seal, water quality may be impacted due to changes of the geochemistry of the aquifer from the mixing of waters from different units; the mixing of surface water and groundwater; or, the introduction of oxygen during the cycling of the irrigation season.

For any new well construction or well rehabilitation, the importance of understanding the complete hydrostratigraphy cannot be understated. Additional factors to consider that impact the groundwater quality from poor well construction include: inadequate seals or long screen intervals that cross-connect water bearing units of different water quality; or long screens intervals or breaches in the casing that result in water cascading and oxygenating the water column.

Case studies will be presented showing the long-term increasing trends of metal concentrations in a municipal water supply well due to cross-contamination between aquifers and how to correct those trends.

The well workover technique includes the incorporation of a thorough evaluation of well construction details, borehole geophysical logs, geochemistry of the aquifers penetrated, and historical well data. Key to this technique, is installing a sufficient volume of grout material without destroying the well which provides a competent seal and appropriate groundwater protection.

Even with the new well construction rules in place in Nebraska, Colorado and other states, or more important historical well construction practices (when the rules weren’t in place), our groundwater quality is susceptible to the same risks, today as yesterday. As a consultant or well driller - What Standard of Care do you apply to your practices – what is your environmental liability?