NGWA Presentation - Matrix Environmental Technologies

Remediation of Fractured Bedrock Containing Light
Non-Aqueous Phase Liquid (LNAPL)
Presenter: Sean R. Carter, P.E. Matrix Environmental Technologies Inc.
Coauthors: Craig Zink, P.G., Matrix Environmental Technologies Inc.
D. Robert Gill, C.P.G., Matrix Environmental Technologies Inc.
Kinyorda D. Sliwiak, Sunoco, Inc. (R&M)
Site Location: Niagara Falls, NY
Niagara Escarpment
http://gmt.soest.hawaii.edu/
Dolostone & Limestone, Silurian Age Lockport Group
UST Field Excavation
Site Geology
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Fractured and weathered dolostone
RQD 9-43%
Depth to bedrock 5-8 feet
Overburden is native clay and fill material (bricks)
Depth to groundwater 9-13 feet
Bedrock Contour Map
Groundwater Contour Map
Environmental Conditions
• LNAPL in 7 monitoring wells with average measured
thickness of 1-6 inches
• Groundwater BTEX up to 82 mg/L
• Groundwater MTBE up to 1 mg/L
• LNAPL and dissolved phase plume off site to the west
and south
LNAPL Thickness
Groundwater BTEX (Pre-Remediation)
Remedial Goals
• Recovery of LNAPL
• Containment of the dissolved phase plume
• Reduction in dissolved phase total VOCs, as measured
using EPA Method 8260 STARS, to a maximum of 1
mg/L
Remedial Design – Phase 1
• Routine bailing of LNAPL from monitoring wells
• Low flow pumping of total fluids using top loading
pneumatic pumps set 1 foot below LNAPL/groundwater
interface (0.25-1 GPM per well)
• Pumping wells operated carefully to prevent drawdown
of LNAPL into deeper fractures
• Treatment system includes oil/water separator, air
stripper and carbon filtration
• Treated water discharge to POTW
Phase 1 Layout
Phase 1 Results
• Operated for 4 years
• Treated 600,000 gallons of groundwater
• Hydrocarbon recovery: 432 lbs as LNAPL and 137 lbs in
groundwater
• LNAPL thickness reduced in all on-site wells (max 3 inches)
• Significant reduction in dissolved phase plume
• LNAPL found in new off site well
Groundwater BTEX (Phase 1)
Remedial Design – Phase 2
• Vacuum enhanced pilot test conducted
• Extraction wells increased from 4 to 9
• Pumping enhanced on all wells with vapor extraction
(150 CFM @ 74 inches w.c.)
• Catalytic oxidizer installed for air treatment
Phase 2 Layout
Phase 2 Results
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Operated for 18 months
Pumping rates more than doubled
Treated additional 1.2 million gallons of groundwater
Hydrocarbon recovery to date: 452 lbs as LNAPL, 172
lbs in groundwater and 261 lbs in vapor
• No measurable LNAPL
• BTEX reduced 85-99%
• Dissolved phase plume found further off site to the south
Hydraulic Control Under Pumping Conditions
Groundwater BTEX
(Phase 2)
Remedial Design – Phase 3
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In Situ bioremediation for groundwater polishing
Oxygen injection pilot test conducted
15 bedrock injection wells
1-inch ID PVC with a 12-inch long screen set at 20-foot
depth
• Oxygen gas pulse injected at rate of 2 lbs/day to each well
• Continued operation of vapor extraction system on 9 wells
Phase 3 Layout
Phase 3 Results
• Currently operating for 15 months
• Average groundwater dissolved oxygen of 7 mg/L
• Hydrocarbon recovery to date: 452 lbs as LNAPL, 172
lbs in groundwater and 310 lbs in vapor
• No measurable LNAPL
• BTEX reduced to non-detect in many wells
• Currently only 1 well exceeds closure goal for BTEX
Groundwater BTEX
(Phase 3)
90
VES RECOVERY VS. TIME
350
80
300
Monthly Recovery (lbs)
Cumulative Recovery (lbs)
70
60
200
50
40
150
30
100
20
50
10
0
0
TIME (DAYS)
CUMULATIVE RECOVERY (POUNDS)
MONTHLY RECOVERY (POUNDS)
250
BTEX Concentration and LNAPL Thickness over Time (MW5)
100,000
3
LNAPL
MW5
10,000
2.5
2
100
Thickness (ft)
Concentration (µg/L)
1,000
10
1.5
1
1
0.5
Low‐Flow Pump & Treat
Off ‐upgrades
0
Vacuum Enhanced Pumping
In Situ Bioremediation
0
Date
BTEX Concentration and LNAPL Thickness over Time (MW6)
100,000
2
LNAPL
1.8
MW6
10,000
1.6
1.4
1.2
100
Thickness (ft)
Concentration (µg/L)
1,000
1
0.8
10
0.6
0.4
1
Low‐Flow Pump & Treat
Off ‐upgrades
Vacuum Enhanced Pumping
In Situ Bioremediation
0.2
0
0
Date
BTEX Concentration and LNAPL Thickness over Time (MW11)
100,000
1.5
LNAPL
1.3
MW11
10,000
1.1
1,000
100
Thickness (ft)
Concentration (µg/L)
0.9
0.7
0.5
10
0.3
1
Low‐Flow Pump & Treat
Off ‐upgrades
Vacuum Enhanced Pumping
In Situ Bioremediation
0.1
‐0.1
0
Date
BTEX Concentration and LNAPL Thickness over Time (MW13 – Off Site)
100,000
LNAPL
1.40
MW13
10,000
1.20
1.00
0.80
100
Thickness (ft)
Concentration (µg/L)
1,000
0.60
10
0.40
1
Low‐Flow Pump & Treat
Off ‐upgrades
0
Vacuum Enhanced Pumping
In Situ Bioremediation
0.20
0.00
Date