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An Investigation of the Contamination Related to the South Hill TCE Spill A class project for: BEE 672 / EAS 471 Professors: Dr. Larry Cathles- Earth and Atmospheric Science Dr. Tammo Steenhuis- Biological and Environmental Engineering
Site History A quick look back at South Hill… Ken Deschere
A BIG part of our Hill …
TCE used for degreasing • Radian Consultants, July 1987:
For more history and references:
TCE Toxicological Profile Jennifer Smith
TCE Background • Legal – typewriter correction fluids, paint removers/strippers, adhesives, rug cleaning fluids, solvent – 1977 FDA ban on use as anesthetic, wound disinfectant, pet food additive Cl Cl C Cl • Ubiquitous in the Environment – 9 -34% drinking water has TCE • Low bioconcentration/biomagnification C H
Exposure • Background levels – 30 mill pounds emitted to atmosphere in US – Urban air 1983: 0. 04 -0. 72, 0. 39, 0. 21 -0. 59 ppb • Exposure Routes – Inhalation: 50% exhaled out • Other exposures – 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) – Breast milk
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 – damage to kidneys and liver • Cancer: liver, kidney, cervical – NOEL 20 ppm
Toxicity • Drinking water – 5 -600 ppb caused increased arthritis, seizure or convulsions, mood disorders; decreased blink reflex, eye closure, choice reaction time, and intelligence test scores – 270 ppb caused increased respiratory infections in children • Co-contaminants (PERC and MC) • Sensitive populations: smoke/drink, children, elderly, breastfed babies
Geology Rachel Shannon
South Hill Site Description Photo by Regina Deschere
Joints Photo by Regina Deschere
South Hill Geology: layered and fractured siltstone Diagram built from information in ESC report received at Thompkins County Library on March 18, 2005 Photo by Regina Deschere
Basic Hydrology Adrian Harpold
Hydrologic Processes on a Hillslope
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.
Hydrology of South Hill • Groundwater moves to the Northwest in most locations. • There is a steep gradient in the groundwater table. • Human induced changes can have a dramatic impact on hydrology: – Pipes – Excavation and fill material – Asphalt and impervious surfaces
Hydrology at South Hill Clear connectivity between soil and bedrock. Water in the bedrock moves through fractures. Shallow soils can lead to saturation and seeps. Vertical movement of groundwater dominates lateral movement.
TCE Properties and Forms M. Ekrem Cakmak
Properties of TCE and Related Transport Processes • Denser than water (1. 46 kg/L > 1. 00 kg/L), pools in the subsurface. • Not easily dissolved and removed by water. • Not easily degraded by microorganisms. • Prefers to be in vapor phase. Russel et al. , 1992, EPA.
Forms of TCE 1. (D)ense (N)on (A)queous (P)hase (L)iquid • moves freely from groundwater movement and forms pools. 2. Dissolved in ground water (max. 1000 mg/L in water) • Solubility of salt in water (360, 000 mg/L) 3. Vapor (highly volatile) (2985 mg/L in air @ 20 °C) • Thought to be responsible for intrusion From: www. dnapl. group. shef. ac. uk
Transport Mechanisms Adrian Harpold
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.
Deep Invasion of TCE is likely • Fire reservoir was built into bedrock • DNAPL sink • Low retardation of TCE • Fractured nature of bedrock at South Hill Reservoir
‘Back-flow’ from Bedrock Fractures Prolongs Contamination Can cause long-term persistence of TCE after ‘free’ TCE has been transported through the system. Very difficult to remediate.
Diffusion of TCE Vapor Diffusion: movement caused by the random (Brownian) motion of molecules. Rates of diffusion depends on material (TCE) and medium (water or air). • Continuous Process • Factor effecting diffusion: – Height of water table – Concentration of TCE vapor – Temperature Groundwater encounters soil contamination and adds to advective transport Capillarity hold some groundwater with VOCs above the water table which increases diffusion
Contaminated water reaching the surface Very little contaminated water can cause air problems. Only a problem when groundwater is high (most probable in the Spring or after long rainstorms).
Degradation of TCE • Controlled by – Oxygen – Carbon – Temperature • Many by-products • Difficult to deduce degradation at South Hill site
Vapor Intrusion Vapor intrusion is the ‘catch-all’ term for the movement of TCE vapor from the subsurface to the surface. ‘Stack-Effect’ Vapor flow along a preferential pathway
Vapor Intrusion Because TCE is heavier than air it can move under its own weight. Steep water table and bedrock gradients make this possible at South Hill. diffusion of vapors off gassing from perched aquifer Groundwater flow direction (not necessarily related to perched aquifer flow direction
Hypothesized Transport Scenario • Confirmed Source: Fire Reservoir • Short-term transport: large fractures in the bedrock, flushing TCE down steep gradients to the bottom of the hill. • Long-term transport: deep bedrock, back diffusion, and deep pools. • Vapor transport: diffusion is dominant in soil, other vapor intrusion pathways may exist • Factor effecting this scenario: degradation and amount and other sources of TCE
Spring Water and Basement Air Sampling Veronica Morales
• There are several different transport mechanisms that in combination determine the fate of DNAPL intrusion into South Hill residences. • Tests conducted would confirm two suspected pathways, determine their dominance and identify the factors that affect TCE behavior.
Purpose of Sampling Team • Formulate a simple and inexpensive method to test some of these pathways and influential environmental factors. • Collect and analyze an extensive series of data from water and air samples.
Spring water sampling • The identification of dissolved TCE or its degradation products in spring water could provide evidence of possible DNAPL sources upstream of the spring. • TCE dissolved in spring water may be indicative of contaminated water and/or vapor intrusion into nearby homes.
Identified Springs and Seeps
• Non detectable concentrations of VOCs in spring water tests in past could be attributed to: – Absence of VOCs in ground water path – Volatization of VOCs as water emerges from springs – Sample collection Given that subsurface conditions are constantly changing, we would like to continue monitoring this potential pathway.
Basement air sampling • If possible, determine optimum sampling conditions for indoor air sampling. • Confirm that the few samples collected are justifiable averages of the indoor conditions.
Collected data should initially be analyzed for the following parameters: –Temporal variations • daily, weekly and seasonal – Ground water trends • increasing/decreasing water levels • temperature changes – Spatial analysis • From house to house
General Sampling Methods Passive diffusion onto sorbent Active sampling with sorbent
Conclusions If the sampling strategy proves effective: • Analysis could increase the comfort level of residents. • Strategy could be employed to screen a broader affected area more quickly and more cost effectively.
Suggestions • With additional investment on equipment, it may be feasible for Cornell students to perform these simple analysis cheaply.
Economic Impact Ian Toevs
Economic Impacts of the South Hill TCE Contamination • Property value • Cost of mitigation system operation • Evaluation of two mitigation strategies
Property Value Selling price over assessed value: South Hill Study area 2003 -2005 38. 9% - 2004 -2005 19. 6% 26% Ithaca 30. 3% 6. 3% • Emerging negative impacts – Houses are on the market longer – Receive fewer bids- less interest
Operation Cost of Mitigation System • Suction fans require energy – Annual cost ranges from <$20 to >$260 – Some systems will require more than one fan • Maintenance – Emerson has agreed to install and maintain From http: //www. infiltec. com/inf-fanr. htm
Mitigation vs. Sampling Costs • Mitigation – Average cost $2500 / house – Follow-up sample(s) • Sampling – Approx. $800 / sample X 3 at each house = $2400 / house – Most houses have been tested 2 - and some even 3 times • Other important factors – Time- unnecessary additional exposure – The benefit of a happy and healthy community