Highway Construction or Stream Destruction: A Water Quality Analysis in the Black Warrior Basin, Walker County, Alabama

In 2012, residents along Freeman Branch Creek in Eldridge, Alabama observed unusual orange discoloration along the stream and on stream vegetation; an unprecendented black veneer coating pebbles along the streambed; and life in the stream seemed to have vanished. Freeman Branch Creek is located in Walker County, Alabama, which is known for its production of coal and natural gas from the underlying Pennsylvanian-aged Pottsville Formation, which is the uppermost geologic layer within the the Black Warrior Basin. Concerns for environmental safety related to intensive mining operations include the concern that shallow aquifers will be contaminated by mining in deep reservoir coalbeds and concern that intensive mining will produce acid mine drainage (AMD). Most available evidence in the Black Warrior Basin indicates that contamination of shallow aquifers by mining and mining fluids is unlikely, but no such evidence has been provided to substantiate the lack of formation of AMD in surface waters of the Black Warrior Basin. AMD is an acidic, heavy-metal-containing sulphate solution derived from pyrite oxidation that may render waterways devoid of life for considerable distances, acidify waterways, and cause the precipitation of heavy metals. AMD is formed primarily through the introduction of oxygen to certain minerals, which may occur through mining. Pyrite is ubiquitous in most coal deposits and when oxidized yields ferrous iron (iron vi flocculant), sulphate, acid (in the form of free hydrogen ions), and associated heavy metals—or AMD contaminants. Given the close proximity of Freeman Branch Creek to mining operations and the unprecendented stream characteristics that mimicked those of AMD, it seemed possible that Freeman Branch Creek was impacted by an upstream source of AMD. In an attempt to identify the source of impact on water quality at Freeman Branch Creek, field sampling was conducted in September 2014 and July 2017. Samples were collected from four locations along Freeman Branch Creek during the first sampling event and from seven sampling locations during the second field sampling event. Water samples derivative of the first sampling event were analyzed using alkalinity titrations, inductively coupled plasma mass spectrometry (ICP-MS) for cations, and ion chromatography (IC) for anions. During the second sampling event, water samples were analyzed using alkalinity titrations and an EXO1 100 m depth sonde with temperature, pH, specific conductivity, total dissolved solids, pressure, and depth-measurement capabilities was installed in the creek at the first sampling location. Initial pH, temperature, and specific conductivity were measured on site at each sampling location at the time of sample collection. Results indicate that an upstream source of AMD is in fact not the cause of reduced water quality in Freeman Branch Creek. Instead, it seems likely that lessened water quality is associated with the construction of Highway 22 that intersects Freeman Branch Creek