Background

Liming the St. Mary's river and its Tributaries:

Since the 1980s, data collected by the US Forest Service and Virginia Department of Game and Inland Fisheries has shown gradual acidification of much of this trout water and a concomitant loss of aquatic life, including fish and aquatic organisms.  Acid deposition from the atmosphere (acid rain) has been cited as the cause of the stream acidification.  The low solubility Antietam rock formation makes up the geology of most of the watershed and provides little buffering capacity to neutralize the acidity.  Recognizing the importance of maintaining the biological integrity of the aquatic ecosystem, the Forest Service decided to introduce limestone to the river system. This was done in March 1999 after an extensive period of public comment and environmental assessment.

Since the late 1980s, the James Madison University Department of Chemistry has cooperated with the Forest Service in developing methodology to treat streams suffering from acidification with a base to temporarily restore water quality.  The neutralizing agent selected for this work is limestone, a natural mineral mined in the Shenandoah Valley. The method, called liming, was successfully used to restore water chemistry in Little Stoney Creek, Shenandoah County, Virginia and Fridley Run, Rockingham County, Virginia and some other streams. The liming is carried out by adding high quality limestone particles to a point in a stream near its headwaters.  The flow of the stream then distributes the particles downstream for 150 to 250 meters and these incorporate into the substrate of the stream bed.  As water flows across the "bed", the limestone slowly dissolves and provides acid neutralizing capacity for several years dependant on the amount added, the stream flow, and the existing stream water chemistry. The main goals of the liming in Virginia were to restore acid neutralizing capacity "lost" due to acid rain, to be cost effective, and to provide treatment for the long periods before re-liming was necessary. Dump trucks or front end loaders were used to introduce the limestone in forest locations where a conveniently located trail or road crossed a stream.  In some locations where there was no road access, a helicopter was used to transport the material to selected sites. The St. Mary's River and its tributaries were treated by helicopter with 140 tons of limestone distributed in six locations on March 20, 1999. The amount of limestone was calculated from stream water quality values collected before the limestone was added, the acid loading from the atmosphere of the watershed and other information to give an anticipated multi-year treatment.  Water chemistry will be monitored closely to determine the effectiveness of the treatment and its longevity