sda trench leachate elevation update2009: sda cover (north of trench 14) was damaged due to wind and...
TRANSCRIPT
April 27, 2016
SDA Trench Leachate
Elevation Update
Citizen Task Force Meeting
2
CTF Update Discussion
• Update the CTF on changes in Trenches 14 and 1.
• Identification of a change in Trench 3 elevation.
• Hydrologic evaluations and field investigation.
• All changes are small, slow increases that do not impact health and
safety, and are not a compliance issue.
3
State-Licensed Disposal Area
Leachate Elevations for Trenches 1, 3 and 14 (ft. AMSL) – 1986 to Current
1357.50
1358.00
1358.50
1359.00
1359.50
1360.00
1360.50
1361.00
1361.50
1362.00
1362.50
1363.00
1363.50
1364.00
1364.50
1365.00
1365.50
1366.00
1366.50
1367.00
1367.50
1368.00
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98
6
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6/1
98
7
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6/1
98
8
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6/1
98
9
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6/1
99
0
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Trench 1 Trench 3 Trench 14
SDA Slurry
Wall
9/18/1992
SDA VLDPE
6/2/1993
SDA Bioeng
Installed
10/12/1993
SDA XR-5
Installed
12/14/1995
SDA Bioeng Removed
XR-5 Installed (TR-9)
10/6/1999
NDA Barrier
Wall Installed
2008
Wind Damage/Repair
North of TR-14 2009
SDA XR-5 over
VLDPE 2010
Open seam /
repair in XR-5
north of TR-14
2014
4
5
Leachate Elevations Relative to Ground Surface for Trenches 1, 3 and 14 (ft. AMSL)
1358.00
1360.00
1362.00
1364.00
1366.00
1368.00
1370.00
1372.00
1374.00
1376.00
1378.00
1380.00
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Trench 1 Trench 3 Trench 14
Ground Surface, 1380 ft
6
Recent Observations in Trench 14
• Leachate elevations have been generally decreasing since
infiltration controls were installed in 1992-1993.
• Increases were noted in early 2011.
• 2011-2015 data show small increases continued.
• 2016 data show stabilization.
• Total increase since 2011 is 0.6 feet (7.2 inches).
• Change does not pose a threat to public health or safety at this
time.
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1365.00
1365.50
1366.00
1366.50
1367.00
1367.50
1368.00
Current increase since 2011: 0.12 ft
per year.
Years before reaching historic high:
11.3 years.
Years before reaching ground
surface: 115.8 years.
Historic High: 1367.46',
10/1992.
Trench 14 Projection – Leachate Elevation (ft. AMSL) 2011 to Current
8
Recent Observations in Trench 1
• Leachate elevation had been generally decreasing since 1996.
• Increases were noted in 2006.
• 2006-2016 data show small increases continue.
• Total increase since 2006 is 0.44 feet (5.28 inches).
• Change does not pose a threat to public health or safety at this
time.
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Trench 1 Projection - Leachate Elevation (ft. AMSL) 2006 to Current
1364
1364.5
1365
1365.5
1366
1366.5
1367
1367.5
1368
Current increase since 2006:
0.045 ft per year.
Years needed before reaching
historic high: 27.1 years.
Years before reaching ground
surface: 313.7 years.
Historic High: 1367.10',
6/1996.
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• Leachate elevations have been generally decreasing since
infiltration controls were installed in 1995-1996.
• Stabilization was noted in early 2014 and continues into 2016.
• Change does not pose a threat to public health or safety at this
time.
Recent Observations in Trench 3
11
1992-1996: NYSERDA installed infiltration controls (i.e., geomembrane covers and slurry
wall) to prevent groundwater from entering the trenches.
2008: Installation of subsurface barrier wall and geomembrane cover at NDA.
2009: SDA cover (north of Trench 14) was damaged due to wind and repaired within
three months.
2010: Installation of new geomembrane XR-5 cover on Trenches 12, 13, and 14 and
drainage system replacement.
2013-on: Continuing to evaluate and investigate potential changes in environmental
conditions.
2014: Identification of 30-ft seam opening in XR-5 near SMW-1, north of Trench 14,
and subsequent repair.
Evaluation of Physical Changes
12
Evaluation of Hydrologic Conditions in the Trenches:
• Ichimura Report (March 2015): Evaluation of the increases in Trenches 14 and 1 as
compared to groundwater elevation and precipitation rates. Report did not identify a
specific pathway or source for the increases.
• GZA Findings and Recommendations Report (October 2015): A more detailed
evaluation to identify areas where additional investigation was warranted for the
increases within both Trenches 14 and 1, and to present findings and
recommendations for mitigation of the increases. Areas where additional investigation
was warranted were identified (as discussed in previous slides).
• GZA Work Plan (est. May 2016): A work plan to implement the findings and
recommendations presented in the October 2015 report. Field activities include
installation of soil probes and piezometers in the perimeter of the SDA (focused
around Trench 14 and east of Trench 1), soil sampling and pumping tests. Soil probes
were also added to evaluate change in leachate elevation in Trench 3.
GZA Proposed Soil Probe and Piezometer Location Plan
14
14
Upcoming Updates
• After evaluation of the data collected from the field activities,
NYSERDA will provide an update to the CTF.