Characteristics and Complexities of Fractured Rock Silurian - - PowerPoint PPT Presentation

Characteristics and Complexities

• f Fractured Rock
• Groundwater moves through discrete discontinuities. . .
• Fracturing is not uniform. . .
• Complex connectivity of fractures, joints, vugs, etc., . . .

Granite and Schist, Grafton County, NH Madison Limestone, Rapid City, SD Biscayne Limestone,

• Ft. Lauderdale, FL

Silurian Dolomite, Argonne, IL Lockatong Mudstone, West Trenton, NJ Sykesville Gneiss, Washington, DC Georgetown Intrusive - Tonalite Washington, DC

• Discontinuities in the rock occur at different scales. . .

Characteristics and Complexities

• f Fractured Rock

Madison Limestone, Rapid City, SD Granite and Schist, Grafton County, NH

fault zone

• Hydraulic properties of fractures, conduits,

vugs, etc., vary over orders of magnitude. . .

• Abrupt spatial changes in hydraulic

properties

• Highly transmissive

features aren’t necessarily correlated with fracture density. . .

Characteristics and Complexities

• f Fractured Rock

Elevation (feet above mean sea level) 450 500 550 600 650 700 10-4 10-2 100 Transmissivity (ft2/day) Acoustic Televiewer Log

Detection limit

Granite and Schist, Grafton County, NH

~1m ~5m

Characteristics and Complexities

• f Fractured Rock

Hydraulic conductivity – Comparison between Unconsolidated Porous Media and Fractured Rock

• Physical and chemical characteristics of the contaminant

and void space architecture affect contaminant distribution. . .

Characteristics and Complexities

• f Fractured Rock

Small “pool” heights of DNAPL force DNAPL into small aperture fractures

Sudan IV shake kit – red indicates NAPL Cloth with hydrophobic dye – staining occurs where dye dissolves in NAPL

Former Naval Air Warfare Center, West Trenton, NJ

DNAPL detected during coring in fractured rock

Testing facility for jet engines (1940’s – 1990’s) Operations ceased in mid – 1990’s Pump-and-treat ongoing for ~ 15 years

• Chemical diffusion into and out of primary porosity of the rock.

. .

Characteristics and Complexities

• f Fractured Rock

1 2 3 4 5 6 7 0.000 0.005 0.010 0.015 0.020 0.025 0.030 0.035

Data Porosity

Granite Basalt Schist Pegmatite Count Porosity

Granite and Schist, Grafton County, NH

The “Reality” at Sites of Groundwater Contamination in Fractured Rock

• Anticipate being engaged in long-term stewardship at fractured rock sites having

groundwater contamination. . .

• Develop strategies for deciding if it is financially prudent to implement aggressive

remediation technologies. . .if so, where, when, and for what duration. . .to accomplish specific objectives. . .recognizing contaminant mass will still remain in the subsurface. . .

• Look to reduce long-term operational and monitoring costs. . .

Former Naval Air Warfare Center, West Trenton, NJ

Granite and Schist, Grafton County, NH Madison Limestone, Rapid City, SD Silurian Dolomite, Argonne, IL Lockatong Mudstone, West Trenton, NJ

Managing Sites of Groundwater Contamination in Fractured Rock

• Enhanced characterization to minimize monitoring locations and

reduce long-term costs. . . robust conceptual models. . .

• Better understanding of in situ physical, chemical, thermal, and

microbial processes that affect fate and transport. . .

• Synthesizing lessons learned in different geologic settings and at

different scales. . .

• Develop innovative methods of monitoring biogeochemical

processes to reduce long-term costs. . . In recognition of the “realities” at fractured rock sites. . .

Understanding In Situ Processes

Theoretical interpretation of diffusion and “back”

• diffusion. . .

Improved Understanding of Chemical Transport in Fractured Rock

Addressing the Complexities of Fractured Rock:

• Recognizing our limitations. . .hydrogeologic complexities translate

into the long-term presence of contaminant mass. . . accepting the “reality”

• f long-term stewardship. . .
• Managing long-term commitments through . . .

(1)Advanced hydrogeologic characterization. . . (2)Better understanding of in situ processes. . . (3)Synthesizing lessons learned. . . (4)Innovative monitoring of biogeochemical processes. . .