Q - Is the deep aquifer on the Eastern Shore of Virginia (ESVA) more sensitive to depletion by residential sprawl or other large withdrawal scenarios than buried aquifers in other areas, such as the upper Maryland-and Delaware part of the Delmarva Peninsula?

A - Yes, for two reasons:

1) Typically, a confined (buried) aquifer has an "outcrop" (exposed edge) type recharge zone where a significant portion of rainwater “insoaks” and slowly migrates "sideways", down into the buried part of the formation. However, the Yorktown formation does not "crop out" (reach the ground surface) on the ESVA, so the typical recharge pattern doesn't exist here. Because we lie east of Chesapeake Bay, the outcrop belt source on the mainland is cut off by saltwater saturation in the Yorktown under the Bay.

The only freshwater to reach the Yorktown under the ESVA is what leaks down directly through overlying strata. Because this strata includes "aquicludes", formations that actually block the transport of water, most of the groundwater diverts into the shallower Columbia aquifer. Unfortunately, the Columbia aquifer is polluted with chemicals from 100’s of years of human activity. Luckily though, the shaley "aquiclude" below the Columbia is "leaky", allowing a very small percent of the rain falling on the central axis of the ESVA (“the recharge spine”) to sink down all the way into the Yorktown. Nevertheless, A small percent of rainwater reaching a particular aquifer means less recharge volume.

2) The total area of ground surface that can theoretically replenish rainwater to our aquifers is relatively small on the ESVA due to the narrow width of the land. (Rain falling on a marsh or marine waters can't reach the sea-bottom and therefore can't sink into the subsurface.) Furthermore, due to the underground outward flow path of the water, only the very middle of this narrow peninsula (the “spine” is effectively recharging the Yorktown, our sole clean-water aquifer. Less recharge area equals less recharge volume.

Q - In order to protect seaside bay and Chesapeake Bay surface water quality, we are told it will be necessary to limit development on the necks. But, how can we concentrate future commercial/ light industrial districts and residential districts along Rte.13 which was built along the center of the recharge "spine, yet protect the aquifer?

A - More "dating" of water from deep wells needs to be accomplished in order to find out where the "youngest" water is- that will detail where the greatest renewal is actually taking place.

Of possible significance is the distribution of forestland along the “spine” Most of it is located in large, shallow depressions called Carolina (or Delmarva) "Bays". These natural depressions have poor soil for construction, yet are valuable for timber (selectively cut in dry seasons and dry years). Even more importantly, they trap and retain rainwater, which then sinks to the aquifer(s) instead of running off into streams. If we were to protect these seasonally wetter (but not always wetland) "depressions", by limiting development and chemical release, it would go a long way towards protecting recharge. (Protecting freshwater wetlands helps, but arguably not enough- the entire depression may have to be protected- Maybe farmers or other landowners could receive special consideration for seriously protecting designated "natural recharge areas".) The idea is that “spine” areas that are not Delmarva "Bays" could then be targeted for higher density developments and commerce/industry. The Delmarva Bays are analogous to the holding ponds that have been built on Long Island, which has some similarities to the ESVA with regard to aquifer recharge. Our “natural holding ponds” could become a boon to aquifer recharge if we can work out a plan.

Q - Why is the ESVA so sensitive to saltwater intruding into our aquifer? Also, Is it true that the greatest danger of saltwater intrusion is near the coastlines- and why would that be?

A - In east-west cross-sections through the Yorktown, the freshwater-saturated part of the formation is lens-shaped. (It has been called a “bubble” but you could better describe it as an eye-shaped bubble). The remainder of the formation (under the Chesapeake Bay and the Atlantic) is saltwater-saturated. Also, deeper formations lying below the Yorktown-Eastover beds do not receive any fresh water from above, and are salty all the way across the Peninsula.

So, you can draw up saltwater from below by overpumping even in the center of the peninsula, but at the “corners” of the “eye”, which happen to be positioned directly below the modern shorelines, the underlying saltwater is higher up, and saltwater also lies alongside the freshwater. Overpumping here will readily draw saltwater into the well.

Q - Where can I get more information on groundwater limitations?

A - See the powerpoint presentation that was given to the Planning commission last June by going to the county website and selecting "studies". There is a lot out there from the Feds, the State, and the County (USGS, the VA DEQ, ANPDC,etc). Most of it is technical, but if you read the local papers, the CBES newsletter, and check out the SONs website, you will become informed on this issue. Groundwater here is so limited that it is critically important to a healthy future of the ESVA (Accomack County and Northampton County).

Q - Any other thoughts?

A -It is too bad that we don't have some large lakes or fresh (non-tidal) rivers here as an alternate source of drinking water, but the geology is the geology, and I personally like the maritime climate and geographic isolation of the long, narrow spit of land that "has been dealt to us" here on the ESVA. However, we must take control of our growth by placing reasonable limits on future population levels. Graduated density zones will have to be part of that picture. Some water-poor places have failed to do that and face a future of increasingly severe water shortages, not to mention other problems coming from residential sprawl.