MGS geologists presented talks at the 2017 Maryland Water Monitoring Council Annual Conference, December 8, 2017

A novel use of electrical resistivity to investigate the hydrogeology of springs supporting endangered amphipods

Andrew Staley

ABSTRACT

The Maryland Geological Survey conducted geophysical work for the US Fish & Wildlife Service to gain insight into the hydrogeology and to identify the contributing areas of three groundwater seepage springs in Washington DC and Montgomery County Maryland where habitats of threatened and endangered amphipod species have been identified. This project employed a novel use of the direct-current electrical resistivity survey method to collect data from the subsurface without disturbing sensitive amphipod habitat. Processed resistivity data were interpreted, in concert with surficial geological mapping and hand-augered sediment sampling, in order to identify the locations of the water table and solid bedrock, as well as structural anomalies that may be indicative of joints, fractures, or faults. Results of the survey suggest the subsurface around the springs is highly complex. Low-resistivity areas interpreted as saturated zones are often directly beneath surface drainage features that are dry at the land surface, indicating local recharge from surface runs. Interpreted saturated areas are also commonly found in the highly permeable zone of the basal saprolite (weathered bedrock), directly above the crystalline metamorphic bedrock. Resistivity anomalies indicate that there may be fracture zones near all of the springs which could act as preferential flow conduits.

Compiling wellwater quality data from multiple databases in Maryland: Opportunities and challenges

David Bolton (Co-authors: Heather Quinn, David Andreasen, and Johanna Gemperline)

ABSTRACT

Wellwater quality data are routinely collected throughout Maryland by local, state, and federal agencies. The data are collected for varying objectives, and samples are analyzed for different water-quality constituents using different collection protocols, analytical techniques, and detection and reporting levels. County health departments test wells for nitrate and bacteria; some also require testing for arsenic, radioactivity, chloride, iron, cadmium, and other constituents before a Certificate of Potability can be issued. Public-supply wells are tested for constituents that have drinking water standards established by the U.S. Environmental Protection Agency. Groundwater studies have been conducted by federal, state, and local agencies to investigate specific research topics. Compiling and assessing data from multiple data sources into a GISbased data set can help identify trends, suggest causative factors, spot data gaps, and examine data in relation to health issues. Challenges include accuracy of well-location data, transcription errors, different reporting and detection levels, and identifying treated versus untreated water samples. This talk will present the Maryland Geological Survey’s experience with compiling wellwater quality data from multiple sources, focusing on Garrett and Anne Arundel Counties.

Physical monitoring and sediment mapping survey of the Patapsco River near Bloede Dam, Howard and Baltimore Counties, Maryland

Elizabeth Sylvia (Co-authors: Stephen Van Ryswick, Katherine Knipper, Anna Gillmor, and Christopher Connallon)

ABSTRACT

Bloede Dam is located on the Patapsco River between Baltimore County and Howard County, Maryland. The dam was constructed in 1906-1907 for the purpose of hydroelectric power generation, but shortly after its construction, sediment began to accumulate behind the dam and in 1924 hydroelectric generation ceased. American Rivers and other partners wished to have the dam removed to open up this section of the river for fish passage. In order to monitor geomorphology changes throughout the River before and after the dam removal process, Maryland Geological Survey conducted 30 crosssectional surveys (Spring 2016) along the Patapsco River prior to the start of construction. Facies maps were completed for each of the cross-section sites and hand drawn images were digitized with ArcGIS. Sediment samples and pebble count data were collected in the field and taken to be analyzed in a sedimentology lab. GPS Photographs were taken at each of the crosssections to visually capture changes in the river system. Three photographs were taken from both the left bank and the right bank of the river, which included upstream, across stream and downstream. Images were loaded onto ArcGIS Online and images were linked onto a map. A digital elevation model and facies map were produced for the Bloede Dam impoundment. Construction for the removal of the dam is currently in progress at Patapsco State Park.