florida remediation conference
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Florida Remediation Conference
Site Remediation Using Horizontal Air Sparge (AS)/ Soil Vapor Extraction (SVE), and Multiphase Extraction (MPE) Wells
Narayanan Raghupathi, P.E. (MACTEC)Angela Finney (MACTEC)
Country Corner ShellTallahassee, FloridaThis paper has been
forwarded to you by:
Site Location
Site Map
Site History• Active gas station• Located at intersection of Hwy 319 and
Hwy-27 in Tallahassee, Florida• 1986- Approximately 1,000 gallons of
premium unleaded gas leaked from an UST• Cleanup being conducted under FDEP
Preapproval Program (Robert Brown, FDEP Site Manager)
• 1995- Installed groundwater recovery and AS/SVE systems (Delta, Inc.)
Site Assessment
• Site Geology consists of sandy clay to clayey sand and grading to fine silty sand at 40 ft bls.
• Depth to water – 41 feet bls• Soil plume – 9,620 square feet (15 to 30 ft bls)• Groundwater plume – 46,722 square feet• COCs – VOCs, PAHs and TRPH• Highest Total BTEX – 11,720 (MW-20R2)• Downgradient contamination migration
Baseline Groundwater Plume
Baseline Soil Plume
Remedial Design Challenges• Remediating contamination beneath Hwy 319
and Hwy 27 and large downgradient groundwater plume (residential area)
• Conduct construction activities without closing the store
• Deep groundwater plume (41 feet bls)• Community relations• Cleanup goals – SCTLs and GCTLs per 62-
777, F.A.C
Remedial Design
• Downgradient - Install two horizontal AS and SVE wells, 800 feet long w/ 450 feet of screen
• Upgradient - Install two horizontal AS and SVE wells, 400 feet long w/200 feet of screen
• Horizontal AS Wells – 48 feet bls• Horizontal SVE Wells – 35 feet bls• Source – Install vertical AS (15) and MPE (9)
wells, and use 15 previously installed MPE wells
Engineering Design Challenges
• Determining horizontal well layout, screen depths, entry and exit locations
• Design of horizontal AS and SVE well screens to have even distribution of air flow through the length of the screen
• Remediate large BTEX and MTBE plume• Develop a complete zone of influence• Optimal equipment sizing• Develop system O&M program
Down gradient Horizontal AS and SVE Well Layout
Upgradient Horizontal AS and SVE Well Layout
Vertical AS and MPE Well Locations
29.70
29.75
29.80
29.85
29.90
29.95
30.00
0 50 100 150 200 250 300 350 400
Distance Along the Screen (ft)
Pressure Along the Screen (psig) in Well HAS-1
OPEN AREA 0.28 %
Pressure Drop in Air Sparge Screen
Head loss along screen is less than 1%
0.7900
0.7950
0.8000
0.8050
0.8100
0 50 100 150 200 250 300 350 400
Distance Along the Screen (ft)
Injection Rate (SCFM / foot of screen) in Well HAS-1
OPEN AREA 0.28 %
Injection Rate in Air Sparge Screen
Slot distribution designed to distribute flow
-6.80
-6.70
-6.60
-6.50
-6.40
-6.30
- 6.20
0 50 100 150 200 250 300 350 400
Distance Along the Screen (ft)
Pressure Along the Screen (psig) in Well HVE-1-
OPEN AREA 0.97 %
Loss of Vacuum in SVE Screen
Head loss along screen is less than 5%
Extraction Rate in SVE Screen
1.4900
1.4950
1.5000
1.5050
1.5100
1.5150
1.5200
0 50 100 150 200 250 300 350 400
Distance Along the Screen (ft)
Extraction Rate (SCFM / foot of screen) in Well HVE-1
OPEN AREA 0.97 %
Screen designed to minimize drop in flow rate
Drilling FluidsManagement
• Mud recycler separates sand/silt cuttings from fluid returns
• Flowing sands produced high volume of solid returns
Horizontal Drilling
Air Sparge Screen
• Longitudinally slotted• 0.27% average open area • 1.0” average slot length• 0.1” slot width
Soil Vapor Extraction Screen
• Longitudinally slotted• 1.01% average open area• 3.7” average slot length• 0.1” slot width
-60
-50
-40
-30
-20
-10
00 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900
Ver
tica
l D
epth
in
Fe
et f
rom
Gro
un
d S
urf
ace
at R
ig Distance in Feet from Entry Point
Well HAS-1 Pitch Profile
Markers DenoteEnd-of-RodLocations
4-inchSDR-11 HDPE Screen
Horizontal Air Sparge Well Profile
-60
-50
-40
-30
-20
-10
00 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850
Ver
tica
l D
epth
in
Fe
et f
rom
Gro
un
d S
urf
ace
at R
ig
Distance in Feet from Entry Point
Well HVE-1 Pitch Profile
Markers DenoteEnd-of-RodLocations
4-inchSDR-11 HDPE Screen
Horizontal SVE Well Profile
AS/SVE and MPE System
• AS Compressor – 717 scfm @ 30 psi• SVE Blower - 2624 acfm @ 14 In. Hg• MPE LRP- 2531 acfm @ 16 In. Hg.• Air Treatment – Two, 1,600 pound carbon
vessels• GW Stripper – Air Stripper
AS/SVE and MPE System
System Operation Cycle
• Vertical AS – 8:00 AM to 8:00 PM• HAS1 – 8:00 AM to 2:00 PM• HAS-2 – 2:00 PM to 8:00 PM• HAS-3 – 8:00 PM to 2:00 AM• HAS-4 – 2:00 AM to 8:00 AM• MPE wells – 24 hours• SVE wells – 24 hours
Cleanup Progress EvaluationMonitoring Well ID Designation Baseline BTEX (µg/l)
Nov 2008Year 2, 1st Qtrly
BTEX (µg/l) July 2010% Reduction from
Baseline
MW-16 Down gradient 2,114 0.99 99.99
MW-20R2 Source area 11,720 107 99.08
MW-22 Source area 11,000 0.32 99.99
MW-28 Source area 583 BDL 99.99
Totals 25,417 108.31 99.57
Monitoring Well ID Designation Baseline MTBE (µg/l) Nov 2008
Year 2, 1st Qtrly MTBE (µg/l) July 2010
% Reduction from Baseline
MW-16 Down gradient 37 4.2 92.7
MW-20R2 Source area 590 87 76.27
MW-22 Source area 260 13 81.53
MW-28 Source area 140 2 98.71
Totals 1,027 106.2 89.65
Current Groundwater Plume
Cleanup Summary
• Target Contaminant concentrations below NAM
• PAHs below GCTLs• BTEX Plume Area – 6,500 sq. ft• MTBE Plume Area – 7,000 sq. ft• BTEX – 99 percent reduction• MTBE – 90 percent reduction
Project Summary
• Successfully installed horizontal AS and SVE wells (Mike Sequino, Directional Technologies)
• Horizontal AS/SVE wells are effective in reducing contaminant concentrations.
• Achieved even air flow through the length of the horizontal well screens.
• MACTEC Project Manager, Angela Finney, successfully worked with FDEP, property owners, and merchants.
• Completed project on time and budget.
QUESTIONS
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