South Hill TCE Project

1. South Hill TCE Project

2. TCE Toxicological Profile Jen Smith

3. Cl Cl C C H Cl TCE Background • Legal • typewriter correction fluids, paint removers/ strippers, adhesives, rug cleaning fluids • 1977 FDA ban – anesthetic, wound disinfectant, pet food additive • Ubiquitous in the Environment • 9-34% drinking water has TCE • Most common organic groundwater contaminant • Clear odorless liquid • DNAPL/ low soil sorption • Highly Volatile/persistent • Low bioconcentration/biomagnification

4. Exposure • Background levels • 30 mill pounds emitted to atmospheres in US • Urban air 1983: 0.04-0.72, 0.39, 0.21-0.59 ppb • Exposure Routes • Inhalation: 50% breathed out • Oral • Food/Breast milk • milk, cheese and butter (0.3-10 ppb); oils and fats (0-19 ppb); canned fruit drinks, ale, instant coffee, tea, and wine (0.02-60 ppb); fruits and vegetables (0-5 ppb); and bread (7 ppb)

5. Toxicity • Well studied at higher concentrations • Central nervous system damage [dizziness (100 ppm), headache (27 ppm), nausea (81 ppm), and confusion], eye and respiratory irritation, and damage to kidneys and liver • Cancer: liver, kidney, cervical (NOEL 20 ppm)

6. Toxicity • Drinking water with 5-600 ppb caused increased arthritis, seizure or convulsions, mood disorders; decreased blink reflex, eye closure, choice reaction time, and intelligence test scores • Co-contaminants (PERC and MC) • Sensitive populations: smoke/drink, children, elderly, breastfed babies

7. Economic Impacts of the South Hill TCE Contamination • Property value • Cost of mitigation system operation • Evaluation of two mitigation strategies Photo by Regina Deschere

8. Property Value • Examined selling price vs. assessment value • 22 sales in current study area • Average increase of 26% from the assessed value • Undocumented negative impacts • Houses are on the market longer • Receive fewer bids- less interest

9. Operation Cost of Mitigation System • Suction fans require energy, energy costs money- who will pay? • Annual cost ranges from <$20 to >$260 • Some systems will require more than one fan • Maintenance? • So far Emerson has agreed to install and maintain... From http://www.infiltec.com/inf-fanr.htm

10. Area of Interest • Expand from the current 104 to approximately 380 property parcels • Bounded by: • East- Aurora St. • West- Meadow St. • North- Six Mile Creek • South- elevation of Emerson

11. Cost and Benefit Analysis of Mitigation Approach

12. South Hill Geology Photo by Regina Deschere

13. South Hill Geology Photos by Regina Deschere

14. Joints

15. Hydrology Water Transport Through Subsurface

16. Water Transport Mechanisms: Diagram

17. Water Transport Mechanisms: Quantification • Evaporation + Transpiration = Evapotranspiration (ET) determined by atmospheric and plant properties as well as soil saturation • Overland Flow occurs with saturation of soil surface • Interflow is a function of slope, saturation, and conductivity • Base Flow moves in direction of lower hydraulic head (combination of pressure and elevation of water table)

18. Water Balance • Water storage in system is equivalent to water flowing into system minus water flowing out of system • eg: water balance on area of soil spanning from the ground level to the top of the water table: Storage = P – ET + Iin – Iout – R

19. Water Transport: Seeps and Springs • Seeps occur when an impermeable layer in the soil blocks recharge and causes formation of a perched water table; the water can flow sideways out of the soil • Springs occur when the water table is higher than the ground surface

20. Water Transport: Seeps and Springs Diagram

21. Spring water sampling • The identification of dissolved TCE or its degradation daughter products in spring water could provide evidence of possible DNAPL sources upstream of the spring. • NEMI Method 524.2 - VOCs in Water Using GC/MS. (VOC range 0.02-200 ug/L)

22. Identified Springs and Weepy Outcroppings

23. Basement air sampling • It is important to determine how well a single sample represents the long-term air concentration of TCE in the basements of the community members. • Collected data will initially be analyzed for the following parameters: • Time variations • Spatial analysis • Ground water level variations

24. Selected homes for basement air sampling

25. General Sampling Methods • Vacuum tube • Passive diffusion onto sorbent • Active sampling with sorbent

26. Conclusions • Ask the DEC to reconsider working with students to analyze spring water samples. • Equipment available at CU not sensitive enough, therefore possible solutions: • Purchase/rent ECD or thermal desorber instruments • Solicit official laboratories to analyze samples. • Try again with next year’s budget.

27. (D)ense (N)on (A)queous (P)hase (L)iquid • moves freely from groundwaterand forms pools. Forms of TCE • Dissolved in ground water (max. 1100 mg/L) • Vapor (highly volatile) Vadose GW Table Saturated www.dnapl.group.shef.ac.uk

28. Transport Processes Vaporization Unsaturated (vadose) zone Adsorption Has little effect Dissolution in Ground Water Advection Dispersion: Negligible Biodegradation Aerobic Can degrade to some extent, due to less resistance to toxic chemicals Anaerobic Needs moderate temperatures (20-30 °C)

29. So What? • In our case, TCE is in fractured bedrock and moves horizontally and diffuses out of the fractures to the ground surface by volatilization. And transported by ground water movement.

30. What’s needed to be done? • More sampling points • To know more about what is going on all over the area • Frequent sampling • Learn more about what is happening to TCEover time • Finding microbial flora of the soil and ground water • Natural attenuation capacity of the area

31. Transport Mechanisms • Several different transport pathways are possible. • Distinguishing between different transport pathways is difficult. • Identification of transport pathways is critical for determining optimum remediation strategies.

32. Deep Percolation of TCE • Likely scenario because: • Location of fire reservoir • DNAPL transport • Low retardation of TCE • Fractured nature of bedrock at South Hill

33. ‘Back-diffusion’ from Bedrock Fractures Can cause long-term persistence of TCE after ‘free’ TCE has been transported through. Very difficult to remediate.

34. Contaminated water reaching the surface

35. Degradation of TCE • Controlled by • Oxygen • Carbon • Temperature

36. Capillarity hold some groundwater with VOCs above the water table which increases diffusion Groundwater encounters soil contamination and adds to advective transport Diffusion of TCE Vapor • Continous Process • Factor effecting diffusion: • Height of water table • Concentration of TCE vapor • Temperature

37. Vapor Intrusion ‘Stack-Effect’

38. diffusion of vapors off gassing from perched aquifer Groundwater flow direction (not necessarily related to perched aquifer flow direction Vapor Intrusion

39. Hypothesized Transport Scenario • Source: Fire Reservoir • Short-term transport: large fractures in the fractured bedrock. • Long-term transport: deep bedrock, back diffusion, and deep pools. • Vapor transport: diffusion is dominant, other vapor intrusion pathways may exist • Other considerations: degradation and amount and other sources of TCE

40. Conclusions

41. Recommendations • Data collection • Defining contaminated area • Seasonal variations • Distinguishing transport mechanisms • Importance of degradation (mınor poınt) • Economic Analysis • Remediation Analysis