Expert: Robert Cummings, P.E. - 11/14/2008

Question
We live in a rural area on 16 acres of a very rocky hillside. Our neighbours have blasted an extensive driveway right to the top of their 10 acres and have blasted a huge area ready for a house. For the first time in 6 years of living here our well has run dry even though we have had lots of rain and our neighbours on the other side have their well overflowing. Do you think their could be a connection with the extensive blasting that has gone on?

Answer
It would be highly unusual, if not impossible, for blasting to cause a well to "run dry" that was not otherwise predisposed to do so.  When one thinks of a well "running dry" the first thing one thinks of is a lowering of the ground water table.  For blasting to cause this it would be necessary for the ground disturbance to be of such magnitude that aquifer replenishment is diverted, through fault offset or collapse of the aquifer pore structure.  While this has been known to occur through strong earthquake shaking, it is not a realistic possibility for most construction blasting; the breadth of the vibration is more limited and the ground motion frequencies are much higher.

There is some possibility that the aquifer has not changed materially but that a problem has developed that is localized to your particular well.  In that case there may be no change to the ground water table but the water does not reach your pump inside the well casing.  You may want to have your well inspected with a video camera to see if the screened portion has become clogged with debris or mineral deposits.  If so, it is fairly straightforward to re-establish the permeability through the casing.  Again, it is doubtful that vibrations from construction blasting somehow released minerals or fine debris that has clogged your well screen, but it is not impossible.  

In your statement of the problem, you did not mention any problems associated with the surface structures adjoining the blasting areas. Surface structures are subject to the effects of surface waves  emanating from a blasting site.  On the other hand, subsurface facilities such as cisterns, wells, and tunnels are subject to body waves, which generally have much higher vibration frequencies and much lower particle displacements. Blasts generating ground vibration intensities sufficient to damage a water well would be much more capable of damaging surface structures.

There is no way to exactly determine the response of your well and the hydrologic regime without a lot of site-specific analysis -- geological, hydrological, and through review of the blasting records.  You should seriously consider having a hydrologist examine your situation.  It may be that some change in local pumping patterns is responsible for a localized drop or shift in water table.  It may also be that your neighbor with the prolific well taps some other aquifer.