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Delaware Geologic Research Symposium - April 14, 2015

The DGS is again hosting a research symposium with presentations on Delaware Geology. This meeting is targeting geoscience professionals as well as planners, engineers, and others that use geologic data.  Documentation for PG credits will be available for those attending. 

The Delaware DataMIL is Retired

The Delaware DataMIL, an online web mapping application that has provided accurate, up-to-date Delaware Geospatial Framework (basemap layers), current and historic aerial photography, and topographic maps for Delaware since 2002 is retired as of June 30, 2013. Originally built as a state of the art, crowd source editing and map delivery system and pilot project for the US Geological Survey National Map, the DataMIL is being replaced by newer mapping technology through the Department of Technology and Information (DTI) which will have a new system in place shortly.

Delaware Geological Survey Issues Report on Groundwater Monitoring and Water-Quality Impacts of Rapid Infiltration Basin Systems

The Delaware Geological Survey released a new technical report entitled “Groundwater Quality and Monitoring of Rapid Infiltration Basin Systems, Theory and Field Experiments at Cape Henlopen State Park, Delaware” which was prepared by A. Scott Andres and Changming He of the Delaware Geological Survey, Edward Walther of the South Water Management District, Florida, Müserref Türkmen of the Izmir Water and Sewerage Administration, Turkey, and Anastasia Chirnside and William Ritter of the University of Delaware. DGS Bulletin 21C documents the results of a detailed study of groundwater quality at a rapid infiltration basin system.

B21C Groundwater Quality and Monitoring of Rapid Infiltration Basin Systems (RIBS), Theory and Field Experiments at Cape Henlopen State Park, Delaware

B21C Groundwater Quality and Monitoring of Rapid Infiltration Basin Systems (RIBS), Theory and Field Experiments at Cape Henlopen State Park, Delaware

A rapid infiltration basin system (RIBS) consists of several simple and relatively standard technologies; collection and conveyance of wastewater, treatment, and discharge to an unlined excavated or constructed basin. By design, the effluent quickly infiltrates through the unsaturated or vadose zone to the water table. During infiltration, some contaminants may be treated by biological and/or geochemical processes and diluted by dispersion and diffusion. The combination of contaminant attenuation and dilution processes that may occur during infiltration and flow through the aquifer are termed soil-aquifer-treatment, or SAT. In the past decade, RIBS have been proposed more frequently for use in Delaware because they stop the direct discharge of treated effluent to surface water, can accommodate significant flow volumes typical of residential subdivisions, yet require much less land than options such as spray irrigation or sub-surface disposal systems.

Decades of research on the shallow Columbia aquifer of the Delmarva Peninsula have clearly identified the high susceptibility of the aquifer from land- and water-use practices, and the processes that control the fate and transport of contaminants from their origin at or near land surface to points of discharge in creeks, estuaries, and wells. The risk of aquifer contamination is great because it is highly permeable, has little organic matter in the aquifer matrix, and the depth to groundwater is very commonly less than 10 ft below land surface. USEPA guidance documents and several engineering texts that cover RIBS design clearly identify these same factors as increasing risk for groundwater contamination but do not provide much information on means to monitor and mitigate those risks. Further, design criteria are based on a small group of experiments conducted in the 1970s prior to development of current understanding of the processes that control groundwater contaminant transport.

Field and laboratory experiments to characterize the physical, chemical, and biological controls and processes associated with the rapid infiltration of treated sewage effluent through infiltration beds and the vadose zone were undertaken at a RIBS located at Cape Henlopen State Park (CHSP), Delaware. Field experiments to understand the geochemical effects of the long-term operation of a RIBS on ground and surface waters, and to evaluate monitoring systems were also conducted at the site. The CHSP RIBS has been in operation since the early 1980s.

Significant concentrations of nitrogen and phosphorus occur in groundwater from the point of effluent entry at the water table to distances greater than 150 ft from the infiltration beds. The high hydraulic, nitrogen (N), phosporus (P), and organic loading rates associated with the operation of RIBS overwhelm natural attenuation (e.g., sorption and precipitation) processes. Data are not sufficient to indicate whether denitrification is occurring. If there is denitrification, the rate is insufficient to remediate RIBS effluent at the site — despite a 25-ft thick vadose zone, an effluent with enough organic carbon to facilitate anaerobic conditions that permit abiotic denitrification and feed microorganism-driven denitrification processes, and hypoxic to anoxic groundwater.

Significant horizontal and vertical variability of contaminant concentrations were observed within the portion of the aquifer most impacted by effluent disposal. Despite the relatively small spatial extent of the disposal area in our study area, identification of the preferential flow zone and characterization of the vertical and temporal variability in the concentrations of contaminants required a multi-phase subsurface investigation program that included an analysis of data from samples collected at bi-monthly intervals from dozens of monitoring points and high frequency temperature monitoring in several wells. A well-designed monitoring system should be based on experimentally determined site specific evidence collected under conditions that duplicate the flow rates that are expected during full-scale operation of the RIBS. Conservative tracers should be used to determine if the monitoring wells are in locations that intercept flow from the infiltration beds.

B21B Hydrogeology of a Rapid Infiltration Basin System (RIBS) at Cape Henlopen State Park, Delaware

B21B Hydrogeology of a Rapid Infiltration Basin System (RIBS) at Cape Henlopen State Park, Delaware

The hydrogeologic framework of Cape Henlopen State Park (CHSP), Delaware was characterized to document the hydrologic effects of treated wastewater disposal on a rapid infiltration basin system (RIBS). Characterization efforts included installation of test borings and monitoring wells; collection of core samples, geophysical logs, hydraulic test data, groundwater levels and temperatures; testing of grain size distribution; and interpretation of stratigraphic lithofacies, hydraulic test data, groundwater levels, and temperature data. This work was part of a larger effort to assess the potential benefits and risks of using RIBS in Delaware.

The infiltration basins at CHSP are constructed on the Great Dune, an aeolian dune feature composed of relatively uniform, medium-grained quartz sand. The age of the dune, determined by carbon-14 dating of woody material in swamp deposits under the dune, is less than 800 years. Underlying the dune deposits are relatively heterogeneous, areally continuous, coarse-grained spit deposits of the proto-Cape Henlopen spit with interbedded and relatively fine-grained, discontinuous swamp and marsh deposits, and beneath, relatively fine-grained, continuous, near-shore marine deposits. The dune deposits can be 45 ft thick under the crest of the dune and nonexistent at the surface. Spit deposits range from 5 to 15 ft thick. Test drilling determined that the near-shore marine deposits are at least 10 ft thick in the vicinity of the infiltration basins. The complete thickness of these deposits was not determined in this study.

Hydraulic testing and grain-size data indicate that the dune and spit deposits are relatively permeable, with average hydraulic conductivities of 140 ft/day and that the swamp and marsh deposits are more than one order of magnitude less permeable, with average hydraulic conductivity of 25 to 10 ft/day. The water-table aquifer is present in the sandier dune and spit deposits. The swamp, marsh, and near-shore marine deposits form a leaky confining unit. The water-table aquifer is 15 to 20 ft thick under the thickest section of the Great Dune and nonexistent where the dune deposits are absent. The vadose zone is greater than 25 ft thick under the infiltration basins.

High-frequency groundwater level and temperature monitoring during periods of maximum wastewater disposal rates indicates that wastewater disposal causes increases in water-table elevations on the order of 1 ft. Groundwater elevations indicate that the water-table elevation is greatest under the infiltration basins and that most flow is directed southward toward a swampy discharge area.

Maximum disposal rates typically occur in summer months when the numbers of park users and water use are greatest. Coincident with greater disposal rates are higher wastewater temperatures. These higher wastewater temperatures are observed in groundwater and provide a means to track the flow of water from beneath the infiltration beds towards a nearby discharge area. Tracking of the warmer groundwater and modeling two-dimensional particle tracking both indicate that wastewater discharged to the infiltration basins reaches the nearby discharge area within 180 days.

Delaware Geological Survey Issues Report on Wastewater Treatment used for Rapid Infiltration Basin Systems

The Delaware Geological Survey released a new technical report entitled “Evaluation Of Wastewater Treatment Options Used In Rapid Infiltration Basin Systems (RIBS)” which was prepared by Müserref Türkmen of the Izmir Water and Sewearge Administration, Turkey, A. Scott Andres of the Delaware Geological Survey, Edward Walther of the South Water Management District, Florida, and William Ritter and Anastasia Chirnside of the University’s College of Agriculture and Natural Resources. DGS Bulletin 21A documents the results of a detailed study of wastewater treatment plant technologies and effectiveness of treatment types that are used to treat wastewater prior to disposal into the ground by rapid infiltration basin systems.

B21A Evaluation of Wastewater Treatment Options Used in Rapid Infiltration Basin Systems (RIBS)

This technical report evaluates several aspects of potential environmental risks, use, and regulation of rapid infiltration basin systems (RIBS) in Delaware. The report reviews and compares regulations regarding RIBS from Delaware, Florida,North Carolina, New Jersey, Maryland, and Massachusetts. Influent and effluent samples from ten advanced wastewater treatment systems that operate in conjunction with RIBS were collected and analyzed. Effluent data obtained from the Non-Hazardous Waste Sites database provided by the Delaware Department of Natural Resources and Environmental Control and other states were assessed. Performance evaluations of the treatment processes that discharge to RIBS were ascertained from the exceedance of concentrations of regulated pollutants in effluent samples.

Although RIBS technology has the potential to be a beneficial alternative to surface discharge and a means for groundwater recharge, this technology is appropriate only if the adverse environmental impacts are minimized. Overall operation and maintenance practices play important roles in the performance of treatment plants. The most common and serious problems associated with treatment plants located in Delaware and neighboring states are high nutrient and pathogen concentrations in the effluent. In Delaware, the discharge of poorly treated effluent to RIBS creates a risk of nutrient and pathogen contamination in the receiving water body, the shallow Columbia aquifer. Years of application of treated effluent with high nutrient, pathogen, and organic content to RIBS will result in significant risks for the environment and public health.

Drought Conditions Indicators for Delaware

Summary of Water Conditions for Delaware website screen shot for March 2015

The DGS will research past performance of the Water Conditions Index (WCI) for Northern New Castle County, as compared with other established drought indicators, and investigate modifying the WCI, if needed. We will also investigate the feasibility of quantifying water conditions in Kent and Sussex Counties by analyzing factors that are most important to these regions (i.e., precipitation, groundwater for agricultural irrigation, etc….)

Geological research initiatives - Public, private, academic partners gather for Delaware Geologic Research Symposium

-Public, private and academic partners came together on Tuesday, April 14, in the Rodney Room of the University of Delaware’s Perkins Student Center for the second biennial Delaware Geologic Research Symposium, hosted by the Delaware Geological Survey and the College of Earth, Ocean, and Environment.
Over 100 geological researchers, state representatives, industrial partners and University students and faculty shared and observed presentations on the latest geological research initiatives in Delaware, and what they mean for the state, its environment and its citizens.

Celebrate National Fossil Day on October, 15 2014

Belmenoidea americana (belemnite) - Delaware's state fossil, approx 71 to 73 million years old, typically found in the C&D Canal area.

Did you know that Wednesday, October 15 is National Fossil Day? As part of the American Geological Institute's "Earth Science Week", the National Park Service has established "National Fossil Day" to promote public awareness and stewardship of fossils, as well as to foster a greater appreciation of their scientific and educational values.

Well and Water Level Summary for Wells with 4 or More Observations

Well and Water Level Summary for Wells with 4 or More Observations - Well Cb15-04

Groundwater levels are basic information needed for evaluating water conditions and for basic and applied research. For these efforts, water levels are being measured statewide in wells completed in multiple aquifers. Some wells are measured for specific projects, such as the Coastal Aquifers Salinity Project and the Water Conditions program, while other wells are measured so that staff can maintain long-term records of groundwater levels for evaluation of trends.

Table contains summary data from wells having 4 or more water level observations.

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Data and Graphs of Water Level Summaries for Wells with 20+ Years or 100+ Observations

Example Hydrograph for DB24-18 - Water Level Summaries for Wells with 20+ Years or 100+ Observations

Ground-water levels are basic information needed for evaluating water conditions and for basic and applied research. For these efforts, water levels are being measured statewide in wells completed in multiple aquifers. Some wells are measured for specific projects, such as the Coastal Aquifers Salinity Project and the Water Conditions program, while other wells are measured so that staff can maintain long term records of ground-water levels for evaluation of trends. Table contains summary data from wells having 100 or more water level observations.

Water Level Summaries for DGS Index Wells

Locations of DGS Index Wells throughout Delaware

Groundwater levels are basic information needed for evaluating water conditions and for basic and applied research. For these efforts, water levels from various aquifers are being measured statewide. Some wells are measured for specific reasons, such as for the Coastal Aquifers Salinity Project and the Water Conditions Report, while other wells are measured so that staff can maintain long-term records of groundwater levels for evaluation of trends.

From where should beach replenishment sand come?

Delaware, Maryland and Virginia have received funds from the federal Disaster Relief Appropriations Act of 2013 to compile data on sand deposits. The data will give clues to where sand is located for future beach replenishment projects. (Photo: FILE PHOTO )

Delaware, Maryland and Virginia have each partnered with the Bureau of Ocean Energy Management to find new sand sources using existing mapping data. As part of the federal Disaster Relief Appropriations Act of 2013, which allocated $13.6 million to the bureau, all three states will each receive $200,000 for the two-year project.

DataMIL Officially Retired

DataMIL Officially Retired
Date: Jun 2013

The Delaware Data Mapping and Integration Laboratory (DataMIL) officially retires on June 30, 2013.

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OneGeology

DGS participates in OneGeology initiative
Project Contact(s):

OneGeology (http://www.onegeology.org/) is an international effort to make available digital geologic map data from around the world. DGS participates in OneGeology by submitting two web map services, one for 1:100K scale surficial geologic units and one for 1:100K scale surficial geologic contacts. These services are open and interoperable (supporting both WMS and WFS protocols) with data attributes in GeoSciML-Portrayal format.

Geologic Map Day: Celebrate on October 18!

Celebrate the second annual Geologic Map Day! On October 18, as a part of the Earth Science Week 2013 activities, join leading geoscience organizations in promoting awareness of the importance of geologic mapping to society. Earth Science Week 2013 will be celebrated October 13-19.

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Delaware State and County Boundaries

Delaware State and County Boundaries

Three datasets are included: the official state boundary line, the county boundary lines, and the land/shore outline. These geospatial data files comprise the bounding lines relating to the political boundary delineation for the State of Delaware as well as the shoreline taken from the 2002 orthophotos of Delaware.

Integration of multiple geophysical techniques to image a submarine groundwater discharge zone

A. Scott Andres of the Delaware Geological Survey, presented "Integration of multiple geophysical techniques to image a submarine groundwater discharge zone" at the 2013 National Groundwater Association Annual Summit held in San Antonio, TX Apr 28-May 1. Co-authors were Holly Michael, John Madsen, Chris Russoniello, and Cristina Fernandez of the UD Dept of Geological Sciences, John Bratton of NOAA, and VeeAnn Cross of US Geological Survey.

RI78 Subsurface Geology of the Area Between Wrangle Hill and Delaware City, Delaware

RI78 Subsurface Geology of the Area Between Wrangle Hill and Delaware City, Delaware

The geology and hydrology of the area between Wrangle Hill and Delaware City, Delaware, have been the focus of numerous studies since the 1950s because of the importance of the local groundwater supply and the potential environmental impact of industrial activity. In this report, 490 boreholes from six decades of drilling provide dense coverage, allowing detailed characterization of the subsurface geologic framework that controls groundwater occurrence and flow.

The region contains a lower section of tabular Cretaceous strata (Potomac, Merchantville, Englishtown, Marshalltown,and Mount Laurel Formations in ascending order) and a more stratigraphically complex upper section of Pleistocene-to-modern units (Columbia, Lynch Heights, and Scotts Corners Formations, latest Pleistocene and Holocene surficial sediments and estuarine deposits). The lowermost Potomac Formation is a mosaic of alluvial facies and includes fluvial channel sands that function as confined aquifer beds; however, the distribution of aquifer-quality sand within the formation is extremely heterogeneous. The Merchantville Formation serves as the most significant confining layer. The Columbia Formation is predominantly sand and functions as an unconfined aquifer over much of the study area.

To delineate the distribution and character of the subsurface formations, densely spaced structural-stratigraphic cross sections were constructed and structural contour maps were created for the top of the Potomac Formation and base of the Columbia Formation. The Cretaceous formations form a series of relatively parallel strata that dip gently (0.4 degrees) to the southeast. These formations are progressively truncated to the north by more flatly dipping Quaternary sediments, except in a narrow north-south oriented belt on the east side of the study area where the deeply incised Reybold paleochannel eroded into the Potomac Formation.

The Reybold paleochannel is one of the most significant geological features in the study area. It is a relatively narrow sandfilled trough defined by deep incision at the base of the Columbia Formation. It reaches depths of more than 110 ft below sea level with a width as narrow as 1,500 ft. It is interpreted to be the result of scour by the sudden release of powerful floodwaters from the north associated with one or more Pleistocene deglaciations. Where the Reybold paleochannel cuts through the Merchantville confining layer, a potential pathway exists for hydrological communication between Columbia and Potomac aquifer sands.

East of the paleochannel, multiple cut-and-fill units within the Pleistocene to Holocene section create a complex geologic framework. The Lynch Heights and Scotts Corners Formations were deposited along the paleo-Delaware River in the late Pleistocene and are commonly eroded into the older Pleistocene Columbia Formation. They are associated with scarps and terraces that represent several generations of sea-level-driven Pleistocene cut-and-fill. They, in turn, have been locally eroded and covered by Holocene marsh and swamp deposits. The Lynch Heights and Scotts Corners Formations include sands that are unconfined aquifers but complicated geometries and short-distance facies changes make their configuration more complex than that of the Columbia Formation.