The Practical Application of Geology to the
Mitigation and Regulation of Isolated Wetlands
November 6, 2012Geological Society of America
Charlotte, NC
Amy Keyworth, Rick Bolich and Evan KaneNCDENR, Division of Water Quality
Background
• Geographically isolated from surface water• The Clean Water Act of 1972
does not protect IWs
– 2001 – Solid Waste Agency of Northern Cook County (SWANCC)
– 2006 – Rapanos/Carabell
Background
• Wetland functions– Flood control– Erosion control– Surface water quality– Biodiversity– Unique functions – amphibian reproduction
• NC – regulate IWs since 2001Protect the function, and the presence
Isolated Wetlands Hydrologic Connectivity Study
Multidisciplinary EPA grant-funded study– Biology, Ecology, Hydrology, Water quality
• Our role – hydrologic connectivity to surface water
• Bonus – knowledge we can apply to existing regulatory programs
• Activities that we regulate that might affect the presence and function of IWs– Mine dewatering– Land application of wastewater
• What level of hydrogeologic assessment is necessary?
Today’s objective
Legendnewphysiography83m_regionPHYSIOGRAP
Blue Ridge Province
Inner Coastal Plain
Outer Coastal Plain
Piedmont Province
50 Miles
50 Miles
Blue Ridge Province
Piedmont Province
Coastal Plain
North Carolina
Bladen County Brunswick County
10 Miles
##### #
##
Owens 19891:250,000
2 Miles
##
##
#
#
2 Miles
Weems 20111:100,000
2 Miles
##
##
#
#
2 Miles
Isolated Wetlands Hydrologic Connectivity Study
• Lessons learned– Stratigraphy– Hydrology
• Horizontal flow direction• Vertical gradient
Data Collection
• 44 cores• 72 monitoring wells• 3 pumping wells• 10 stream gaging stations• Water levels
– monthly point-in-time– 32 automatic data-loggers
• 3 Aquifer tests
Stratigraphic Conceptual Models
Isolated wetland Stream
ETP
Isolated wetland Stream
Dark gray clay layer
Sandy layer
Water Level
Sand at Site BL7
Isolated wetland Stream
Silt bodies at BL1
Silt body
Sandy layerWater Level
Dark gray clay layer
Silt confining layer at site BL6 Isolated wetland Stream
Unconfined aquifer
Confined aquiferUnconfined
aquifer
Silt body
Sandy layerWater Level
Dark gray clay layer
Elev
ation
(fe
et)
Distance (feet)0 600200 400
65605550454035302520151050
Interbedded sand and clay
Sandy layer
Clay chips
UnknownWood
Isolated wetland
Connected wetland
Lower K layer at site GS1
250 Feet
250 Ft
Site BL9 – cemented zones
Core siteCemented zone
Isolated Wetland
Hydrology Results
500 ft
Flow direction Site BL7 - topographic control
##
#####
Monitoring wells
Surface Water gaging
Flow direction
500 ft
#
Monitoring wells
Flow direction
Flow directionSite BL17 - radial
10/15
/10
11/4/
10
11/24
/10
12/14
/101/3
/11
1/23/1
1
2/12/1
13/4
/11
3/24/1
1
4/13/1
15/3
/11
5/23/1
1
6/12/1
17/2
/11
7/22/1
1
8/11/1
1
8/31/1
160
61
62
63
64
BL6-MW2 D and S
BL6-MW2dBL6-MW2s
Wat
er T
able
Ele
vatio
n (ft
msl
)
Vertical gradientUpward
10/15
/10
11/4/
10
11/24
/10
12/14
/101/3
/11
1/23/1
1
2/12/1
13/4
/11
3/24/1
1
4/13/1
15/3
/11
5/23/1
1
6/12/1
17/2
/11
7/22/1
1
8/11/1
1
8/31/1
173
74
75
76
77
BL17 - MW1D and S
BL17-MW1dBL17-MW1s
Wat
er T
able
Ele
vatio
n (ft
msl
)
Vertical gradientDownward
10/15
/10
11/4/
10
11/24
/10
12/14
/101/3
/11
1/23/1
1
2/12/1
13/4
/11
3/24/1
1
4/13/1
15/3
/11
5/23/1
1
6/12/1
17/2
/11
7/22/1
1
8/11/1
1
8/31/1
151
52
53
54
55
56
BL1 - MW1d and s
BL1-MW1dBL1-MW1s
Wat
er T
able
Ele
vatio
n (ft
msl
)
Vertical gradientNo vertical gradient
Vertical gradientChanges with conditions
BL7-MW1D BL7-MW1S Precipitation
50
51
52
0
1
2
Aug SepApr May JulJun
Wat
er Ta
ble
Elev
ation
(ft m
sl)
Hour
ly P
reci
pita
tion
(in)
BL7 - MW1D and S
What level of assessment is necessary?
10 Miles
##### #
##
Owen 19892 Miles
##
##
#
#
2 Miles
Weems 20112 Miles
##
##
#
#
2 Miles
Conclusions
• Can’t assume a simple system• Scale matters• Detailed stratigraphic characterization
Sample site plan
Core locationMonitoring well location
Conclusions
• Can’t assume a simple system• Scale matters• Detailed stratigraphic characterization• Think local scale
Acknowledgements• EPA Cooperative Agreement Number
CD 95415809 and CWA Section 106• Bladen Lakes State Forest• Turnbull Creek Educational State Forest• The Nature Conservancy
Top Related