The Virginia Ground Water Management Act of 1992 mandates the regulation of large groundwater withdrawals in certain portions of the Commonwealth to prevent adverse impacts due to over utilization of the resource. There are currently two proposed changes to the regulations. It has been proposed to expand the Eastern Virginia Ground Water Management Area to include the Counties of Caroline, King and Queen, Gloucester, Mathews, Middlesex, Essex, King George, Westmoreland, Richmond, Lancaster and Northumberland; parts of Spotsylvania, Stafford, Prince William, Fairfax and Arlington Counties; and the City of Alexandria. This would expand groundwater withdrawals beyond the confines of the Tidewater, west of the fall zone, into another groundwater basin. Currently, this Ground Water Management Area includes every county and city south of the York River and its tributaries and east of I 95, except Gloucester, Mathews, Middlesex Counties. The proposed expansion would bring these three counties on the edge of the Chesapeake Bay, and the corresponding area north of the York and its tributaries, into the regulated area. The boundaries of the Eastern Shore Ground Water Management Area would remain unchanged.
Ground water levels in the Tidewater region of Virginia’s coastal plain are continuing to decline. Impacts from groundwater withdrawals are propagating along the fall zone into the coastal plain and have the potential to interfere with wells in these areas. However, you cannot manage the several groundwater basins as if they were a single basin, but you cannot ignore the interrelation between the basins. The smallest of examples in this area is Bull Run which feeds the Occoquan Reservoir originates in the Piedmont. The coastal plain has been the area of the most intense growth and the area was forecast by Virginia Tech to have inadequate reserves to meet the next drought if not addressed. Given current ground water declines, the entire coastal plain aquifer system must be managed to maintain a sustainable future supply of ground water. Virginia is blessed with what appears to be rich resources of water, but they are not infinite. Surprisingly little hard data on the groundwater has been collected. As a much wiser man than I pointed out, without data there can be no understanding of our resources and our planet. What level of withdrawal does the Agency propose to allow in each basin?
The second proposed change is a little frightening because it both ambiguous and seemingly ambitious in its reach: the Board and DEQ propose “to consider amending the Ground Water Withdrawal Regulation, 9 VAC 25 610 to address the increasing demand on limited groundwater resources, changes to the administrative review process, and regulatory changes necessitated by new information on the coastal plain aquifer system.” Virginia is estimated to use 188 million gallons of groundwater each day to supply public water systems, industry, agriculture, commercial operations and mining. This excludes over 40 million gallons a day that supplies private domestic well in the state including my well. While applaud the agency’s proactive stance, to take action to manage and maintain our water resources before crisis strikes, I wonder how can the DEQ even propose regulations on diverse geology, demand and groundwater basins and do so without data. Though the goal is laudable, what methods are they proposing to manage, control, protect and allocate a resource that is not well understood? The agencies’ reasons for proposing this action echo and elaborate on their explanation of reasons for proposing to expand the Ground Water Management Area, but that is not enough.
Even more ominous, the Board is preparing “to address for which users and for what purposes this finite resource should be allocated” and “to address what constitutes an adequate margin of safety and what technical criteria are defensible for determining whether or not to issue a permit and for what amounts.” All of this appears to signal a readiness and desire to control the most valuable resource in the commonwealth of Virginia. Without water there can be no life, no economy. More importantly, the Agency seems to have determined that allocation of water resources will be performed by government with a strategy or manner of its choosing. The agency proposes to allocate the most valuable resource in the commonwealth of Virginia without answering the question of How should water be allocated. The Agency is determined to proceed to avoid ground water declines. Before the Agency proceeds to manage the groundwater use for Virginia, the people must determine how this resource should be managed.
Showing posts with label Commonwealth of Virginia. Show all posts
Showing posts with label Commonwealth of Virginia. Show all posts
Monday, February 8, 2010
Monday, January 25, 2010
The Geological Regions of Virginia
Loudoun County’s proposed amendments to the zoning ordinances that would create a Limestone Overlay District (LOD) got me thinking of about the geology of the state. I did not grow up in Virginia, but not only is my husband a native son of the Commonwealth, but he comes from a long line of teachers and I have sweet memories of a road trip with his Aunt Louise amusing her great nephew with teachable moments as we drove through the Valley, to the Blue Ridge, to the Piedmont. It was not until years later that I realized that Aunt Louise had been teaching her five year old great nephew (and me) the geological regions of Virginia.
The geological regions of Virginia are (from east to west) the Coastal Plain, the Piedmont, the Blue Ridge, the Valley and Ridge and the (Cumberland) Plateau. Historically, the geology of these regions has determined what the lands can be used for and by implication the nature of the communities that developed in these regions. Post World War II development of the suburbs had disconnected us from the direct ties to geology, but the density of the population and the demand for water, specifically groundwater is bringing us bank to understanding our geological destiny. The natural occurrence of groundwater depends on the geological conditions.
The Costal Plain of Virginia is composed mostly of unconsolidated geologic deposits and extends from the Atlantic coast to the “fall zone” a geological line that runs north-south through Fairfax, Fredericksburg, Richmond, and Petersburg. At its widest portion the Costal Plain is over 100 miles wide. Costal Plain deposits consist of alternating layers of unconsolidated sand, gravel, silt, shell strata and clay and slopes generally southeast. There are two groundwater systems, an unconfined aquifer and a lower artesian aquifer both flow in the general direction of the topography slope towards the ocean. In the 1990’s it was estimated that approximately half of Virginia’s groundwater use was in this region. The principal recharge area for these aquifers is the land around the fall zone where the aquifers outcrop. There is some leakage from the upper to the lower aquifer, but that is relatively insignificant. The Costal Plain’s artesian aquifer has an enormous groundwater storage capacity and Virginia remains a relatively wet location, but pumping (possibly over pumping) has lowered the artesian pressure allowing some salt water intrusion near the coast and overbuilding in the recharge zone has impacted the availability of water. It is projected with little more population growth that during drought years Fairfax and the Norfolk-Virginia Beach area will have inadequate water.
The Piedmont is bordered by the “fall zone” on the east and the Blue Ridge Mountains on the west. The Piedmont is the largest geological region in Virginia and has a diverse geology largely dominated by igneous and metamorphic rocks, with some areas of sedimentary rocks. The area has limited overburden and the fractures and fault lines formed in the rocks store and transmit groundwater. The size and number of water bearing fractures decrease with depth so significant supplies of water are generally located in the first few hundred feet. There is a wide variation in groundwater quality and yield ranging from under 1 gallon to over 50 gallons a minute. The largest yields are obtained where fracture and fault system are extensive (like my neighborhood) along the base of the Blue Ridge Mountains. In other areas of the Piedmont, disintegration of the granite bedrock forms a zone of granular material with slow recharge and relatively high and annoying amounts of iron and sulfur. The fractures and faults offer a route of transport for any contaminants so that the most water rich areas are the most susceptible to contamination.
The Blue Ridge province lies to the west of the Piedmont and is a narrow zone (4-25 miles wide) of mountains that runs from North Carolina to Maryland with the highest elevations in Virginia. The bedrock is near the surface and relatively impervious and contains limited amounts of water in joints, fractures and fault zones. Igneous and metamorphic rocks are most common on the eastern slope (and into the Piedmont) and sedimentary rocks are common on the western slope. Water yields are low and limited and typically very high in iron.
The Valley and Ridge region is to the west of the Blue Ridge Mountains and is underlain by consolidated sedimentary rocks of limestone, dolomite, shale and conglomerate. Limestone and dolomite occur beneath lowlands, such as the Shenandoah Valley (also within the lowlands between the Potomac and the Catoctin Mountains) these deposits consistently form productive aquifers. Karst features such as sinkholes, caves, and large springs are found in the Valley and Ridge province. The ridges in the upland area are typically underlain by sandstone and shale with limited groundwater yield. Limestone frequently contains underground channels that store and transmit groundwater. Rapid movement of water in the limestone area makes the pollution potential high. Aquifers are often recharged directly by streams crossing fault zones giving wells in these areas the highest yields. This direct surface water to groundwater recharge can create serious water quality problems. The groundwater in these zones bypasses any natural filtration the soil might have provided. The quality of the groundwater would reflect the quality of the seasonal streams and surface water.
The final and smallest geological region of Virginia is the Cumberland Plateau also called the Appalachian Plateau which includes the southwester tip of Virginia. This region is underlain by sedimentary rocks, primarily sandstone, shale and the coal. It is the presence of coal that has most determined the fate of this region. The gentle folding of these formations has created domes and basins and faulting has occurred. Groundwater quality is generally best in the bedrock above the stream level. The groundwater in the stream level contains high concentrations of sulfate, sulfite, nitrate, iron and carbon dioxide. The water improves at 150-300 feet below this area. Groundwater is generally used for small domestic purposes and processing coal. The shallow nature of the groundwater allows for relatively easy contamination.
Virginia is rich in water our actions will determine if we remain so. The process by which water from rainfall, snowmelt, streams and rivers flows into water bearing geologic formation is the groundwater recharge process. The climate change models (as limited and faulty as they may be) predict that Virginia will become a bit wetter and warmer (think North Carolina). A failure of the water supply in Virginia will be due to our own actions and decision. The land surface through which groundwater is recharged must remain open and uncontaminated to maintain the quality and quantity of groundwater of the Commonwealth of Virginia.
The geological regions of Virginia are (from east to west) the Coastal Plain, the Piedmont, the Blue Ridge, the Valley and Ridge and the (Cumberland) Plateau. Historically, the geology of these regions has determined what the lands can be used for and by implication the nature of the communities that developed in these regions. Post World War II development of the suburbs had disconnected us from the direct ties to geology, but the density of the population and the demand for water, specifically groundwater is bringing us bank to understanding our geological destiny. The natural occurrence of groundwater depends on the geological conditions.
The Costal Plain of Virginia is composed mostly of unconsolidated geologic deposits and extends from the Atlantic coast to the “fall zone” a geological line that runs north-south through Fairfax, Fredericksburg, Richmond, and Petersburg. At its widest portion the Costal Plain is over 100 miles wide. Costal Plain deposits consist of alternating layers of unconsolidated sand, gravel, silt, shell strata and clay and slopes generally southeast. There are two groundwater systems, an unconfined aquifer and a lower artesian aquifer both flow in the general direction of the topography slope towards the ocean. In the 1990’s it was estimated that approximately half of Virginia’s groundwater use was in this region. The principal recharge area for these aquifers is the land around the fall zone where the aquifers outcrop. There is some leakage from the upper to the lower aquifer, but that is relatively insignificant. The Costal Plain’s artesian aquifer has an enormous groundwater storage capacity and Virginia remains a relatively wet location, but pumping (possibly over pumping) has lowered the artesian pressure allowing some salt water intrusion near the coast and overbuilding in the recharge zone has impacted the availability of water. It is projected with little more population growth that during drought years Fairfax and the Norfolk-Virginia Beach area will have inadequate water.
The Piedmont is bordered by the “fall zone” on the east and the Blue Ridge Mountains on the west. The Piedmont is the largest geological region in Virginia and has a diverse geology largely dominated by igneous and metamorphic rocks, with some areas of sedimentary rocks. The area has limited overburden and the fractures and fault lines formed in the rocks store and transmit groundwater. The size and number of water bearing fractures decrease with depth so significant supplies of water are generally located in the first few hundred feet. There is a wide variation in groundwater quality and yield ranging from under 1 gallon to over 50 gallons a minute. The largest yields are obtained where fracture and fault system are extensive (like my neighborhood) along the base of the Blue Ridge Mountains. In other areas of the Piedmont, disintegration of the granite bedrock forms a zone of granular material with slow recharge and relatively high and annoying amounts of iron and sulfur. The fractures and faults offer a route of transport for any contaminants so that the most water rich areas are the most susceptible to contamination.
The Blue Ridge province lies to the west of the Piedmont and is a narrow zone (4-25 miles wide) of mountains that runs from North Carolina to Maryland with the highest elevations in Virginia. The bedrock is near the surface and relatively impervious and contains limited amounts of water in joints, fractures and fault zones. Igneous and metamorphic rocks are most common on the eastern slope (and into the Piedmont) and sedimentary rocks are common on the western slope. Water yields are low and limited and typically very high in iron.
The Valley and Ridge region is to the west of the Blue Ridge Mountains and is underlain by consolidated sedimentary rocks of limestone, dolomite, shale and conglomerate. Limestone and dolomite occur beneath lowlands, such as the Shenandoah Valley (also within the lowlands between the Potomac and the Catoctin Mountains) these deposits consistently form productive aquifers. Karst features such as sinkholes, caves, and large springs are found in the Valley and Ridge province. The ridges in the upland area are typically underlain by sandstone and shale with limited groundwater yield. Limestone frequently contains underground channels that store and transmit groundwater. Rapid movement of water in the limestone area makes the pollution potential high. Aquifers are often recharged directly by streams crossing fault zones giving wells in these areas the highest yields. This direct surface water to groundwater recharge can create serious water quality problems. The groundwater in these zones bypasses any natural filtration the soil might have provided. The quality of the groundwater would reflect the quality of the seasonal streams and surface water.
The final and smallest geological region of Virginia is the Cumberland Plateau also called the Appalachian Plateau which includes the southwester tip of Virginia. This region is underlain by sedimentary rocks, primarily sandstone, shale and the coal. It is the presence of coal that has most determined the fate of this region. The gentle folding of these formations has created domes and basins and faulting has occurred. Groundwater quality is generally best in the bedrock above the stream level. The groundwater in the stream level contains high concentrations of sulfate, sulfite, nitrate, iron and carbon dioxide. The water improves at 150-300 feet below this area. Groundwater is generally used for small domestic purposes and processing coal. The shallow nature of the groundwater allows for relatively easy contamination.
Virginia is rich in water our actions will determine if we remain so. The process by which water from rainfall, snowmelt, streams and rivers flows into water bearing geologic formation is the groundwater recharge process. The climate change models (as limited and faulty as they may be) predict that Virginia will become a bit wetter and warmer (think North Carolina). A failure of the water supply in Virginia will be due to our own actions and decision. The land surface through which groundwater is recharged must remain open and uncontaminated to maintain the quality and quantity of groundwater of the Commonwealth of Virginia.
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