# Presentation: 503936

## In Situ Thermal Approaches to NAPL Remediation for RCRA Corrective Action

*Jim Cummings*
*OSRTI/OSWER/USEPA*

## Why In Situ Treatment?

- Avoid cost/risk of excavation/transportation
- Address contamination not readily amenable to excavation
- Beneath buildings/structure
- Beneath water table
- At Depth

## Beneficial Effects of Increased Temperature

- Increased Volatility
- Reduced Viscosity
- (Slightly) Increased Solubility
- Mixture of Water and Contaminants boil at lower temperature than normal contaminant boiling point
- Increased hydrolysis rates
- Thermal processes less affected by heterogeneity

## Heating Approaches

- Steam Enhanced Extraction (SEE)
- Electrical Resistive Heating (ERH)
- Thermal Conductive Heating/In Situ Thermal Desorption )ISTD

## STEAM ENHANCED EXTRACTION (SEE)

## Steam Injection Cross-Section – Visalia, Ca Pole Yard NPL Site

## Visalia 1995-97: 1.2M lb Creosote Removed

-  A yield equivalent to _3500_ years of pump-and-treat

**204,000 lb**

- Vapor Hydrocarbon

- Burned In Boilers

**210,000 lb**

- In Situ Destruction

- (Removed CO2)

**607,000 lb**

- Free Product

- LNAPL & DNAPL

**195,000 lb**

- Dissolved Hydrocarbon

- Activated Carbon Filtration

**Prior to steam injection**
**the removal rate was **
**approximately **_**10 lb per week**_

**Visalia 1995-97:***** 1.2M lb Creosote Removed***

## ISTDProcesses

-     Thermal Conduction into Soil
-     Vaporization of Fluids and Contaminants within Soil
-     Collection of Vapors
-     In-Situ Oxidation and Pyrolysis - >95-99% In-Situ Destruction
-     Aboveground Treatment of Vapors (may be simpler than illustrated)

## Visalia Progress  Groundwater Quality - Pentachlorophenol & Creosote

- EW-4

- S-9

- S-8

- EW-3

- S-7

- S-14

- EW-1

- S-15

- EW-2

- Groundwater
- Gradient

**Visalia Progress  **Groundwater Quality - Pentachlorophenol & Creosote

- Before Treatment
- Current (4/02)

**PCP**    Creosote
- (ppb)      (ppb)

- 3,890   2,700
- ND       5

**Highest Recorded Concentrations **
**Most Recent Concentrations**

- 1,100   63,000
- ND       752

- 105   10,600
- ND      159

- 1,300   93,400
- ND      2,550

- 189   15,400
- ND      >1

- 371   544
- 3       3

- 0.58   ND

- ND  ND

- ND  ND

## Costs at Visalia

**Total Project Cost ****- $21.5**** million 1996 through mid-2001**
**Unit Cost per Cubic Yard of Soil Treated **
**Actual Costs ****	**** ****	****	****$57**
**With Lessons Learned ****	****$38**
**Comparative Cost per Gallon of Creosote Removed**
**Pump and Treat****	****	****$26,000 **
**Steam****	****	****	****	****$130**
**Estimated Time to Remove 1.2 Million Pounds of Creosote**
**Pump and Treat****	****     ****3,250**** years**
**Steam****	****	****          ****	****     3 years**

## ELECTRICAL RESISTIVE HEATING (ERH)

## Full-Scale ERH Subsurface X-Section

**Courtesy of URS**

## Full-Scale Implementation Multiple Arrays

## ERH - TCE DNAPL RemediationAir Force Plant FourFort Worth, Texas

**Photo Courtesy of URS**

## Full-Scale ERH at AF Plant 4

- 1/2 acre area inside/outside of Bldg. 181 -manufacturing opns 24/7
- 70 electrodes and co-located Vapor Recovery wells in and around existing tanks/ piping/equipment (32° angles)
- Heterogeneous silt, clay and gravel with a highly weathered limestone, competent bedrock at 32 ft bg
- Groundwater at 27 ft bg
- ERH operations May to Aug 2002; reduced – Dec ‘02
- Goal – Avg 90% reduction based on a 95% UCL

## Angled Electrode Boring 

**Courtesy of URS**

## ERH Remediation BeneathAir Force Plant Four

**SVE piping**

**electrical cable**

**electrode**

**SVE well**

**Photo Courtesy of URS**

## Continuous Indoor Air Monitoring

**INNOVA System sampled air for TCE every 5 minutes**

** ****Would shutdown ERH system if TCE >3 ppm**

** ****Online remote monitoring**

** ****Never exceeded background TCE concentrations inside Bldg. 181**

**Courtesy of URS**

## Maximum Subsurface Temperatures Achieved

**Courtesy of URS**

## Pre and Post Soil Data with Depth

**Courtesy of URS**

## Final TCE Concentrations in Groundwater

## Results at AF Plant 4

- Area/Vol. treated:  22,000 sq. ft./27,400 c. yds
- Average weekly power input – 563 kW
- Recovered ~ 1,600 lbs. TCE
- Met GW goal following 4 months of opns - ~ 93% avg reduction in TCE GW conc.
- Met soil goal - 90% average reduction
- TCE levels never exceeded background in indoor breathing space
- No impacts on manufacturing opns
- $57 per cubic yard
- Evidence of heat enhanced biodegradation

## THERMAL CONDUCTIVE HEATING/IN SITU THERMAL DESORPTION (ISTD)

## ISTDProcesses

-     Thermal Conduction into Soil
-     Vaporization of Fluids and Contaminants within Soil
-     Collection of Vapors
-     In-Situ Oxidation and Pyrolysis - >95-99% In-Situ Destruction
-     Aboveground Treatment of Vapors (may be simpler than illustrated)

## ISTD: Simultaneous Application of Heat and Vacuum

**ISTD: Simultaneous Application of Heat and Vacuum**

- Heater-
- Vacuum
- Well

- Hexagonal Well Pattern

## S. Glens Falls, NY Drag Strip (PCBs)

- Waste oil sprayed on soil

- Sharp boundary of ISTD treatment zone

## Adjacent Residences, Portland, IN

**ISTD**
**Well**
**Field**

## ISTD at Former Shell Bulk Storage Terminal, Eugene OR 

## ISTD at Eugene, OR (cont.)

- Maximum soil concentrations of 9,300 mg/kg (DRO), 3,500 mg/kg (gasoline); GW 1,300 g/l (benzene);
- as much as 7.9 ft of free product in monitoring wells.
- Gravel layer 1-4’, over silt to ~11-16’ bgs.
- Project goals:
- Removal of free product and benzene
- Closure of site under Oregon DEQ RBCA UST program

## Eugene, OR ISTD Project Results

- Free phase LNAPL removed from the 1-acre site
- Estimated 200,000 lbs of hydrocarbons removed and treated during 120-day heating
- Post-remediation soil and GW samples below the ODEQ’s Tier 1 Risk-Based Concentrations:
- Benzene concentrations in GW w/in treatment area reduced from 1,300 g/L to 2.50 g/L.
- Post-treatment off-site GW samples below the analytical detection limit (i.e., <0.5 g/L)
- Oregon DEQ issued a “No Further Action” letter for the site on March 14, 2000

## Information Resources

- Jim Cummings
- 703- 603-7197
- cummings.james@epa.gov
- Database: *cluin.org/products/thermal*
- Archived web-based seminar: *cluin.org/studio/napl*