Upload
others
View
1
Download
0
Embed Size (px)
Citation preview
Free Product (LNAPL) in a Well Debunking the Alarmist Attitude/Stigma
Pertaining to Environmental Risk
Real Property Institute of Canada (RPIC) 2012 Federal Contaminated Sites National Workshop
Allstream Centre, Toronto, Ontario, Canada
Keynote Presentation by: David Cushman, Conestoga-Rovers & Associates
May 2, 2012
Debunking the stigma…
Quarter-Century (25-Year) Evaluation
Evolution of LNAPL science Regulatory approach - LNAPLs Regulatory approach - Non-LNAPLs (i.e., all
other contaminants)
Free Product/LNAPL means:
LNAPL - from right to left: • NAPL – Non-Aqueous Phase Liquid (immiscible
in water; does not dissolve in water) • L – Light (less dense than water; floats on water
in an open environment) • May include pure solvents, but is mostly
recognized as oil or petroleum-related materials (fuels, lubricants, etc.)
…in a Well Means:
LNAPL present in a monitoring or test well (also referred to as an observation well or piezometer)
DOES NOT refer to LNAPL
present in a drinking water or potable water well
LNAPL
Water
Monitoring Well
Why the stigma?
The thought of LNAPL (most often gasoline) in a well is simply “offensive”
It’s explosive - gasoline in a well can lead to explosions or explosive conditions
It’s toxic - one litre of gasoline can contaminate one million litres of water
It can move - if it’s in a well, then it may move somewhere else and cause problems!
But…what would you do if…
Most of what you believed about LNAPL (behaviour, dangers, risks) turned out to be false?
Things that you thought were fact, were fiction?
Perceptions that you had relied on for years turned out to be misperceptions?
Would you…
Continue with the same old beliefs? Continue along the same course? Continue with the status quo?
Knowing that you’re wrong!
Yet that’s exactly what we do when we… Automatically assume that LNAPL in a well
poses an unacceptable risk (to human health and/or the environment)
Spend millions of dollars on unnecessary and unwarranted LNAPL cleanups
Continue to ignore the current LNAPL science and forge ahead with the status quo!
Why is this important?
Because LNAPL is one of the most prevalent, widespread, common pollutants on the planet • Transportation (planes, trains, autos, ships) • Heating and cooling • Manufacturing (hydraulics, lubricants, fuel) • Construction (hydraulics, lubricants) • Etc.
Why is this important?
Because billions of $$$ are spent on LNAPL investigations and remedial operations in North America alone
Because many LNAPL remedial programs
generate more pollution and risk than what’s being mitigated
Why is this important?
Because LNAPL remediation programs often prevent/preclude the beneficial redevelopment or re-use of real property
Because the “perception” of significant risk is most often WRONG!
LNAPL misperceptions…
LNAPL research and science over the past 25 years have taught us that most of what we thought we knew about LNAPL, is incorrect!
For example…
We believed that…
LNAPL floats on top of the water table and cannot penetrate into the water
FALSE! At most sites, the majority of LNAPL is
located beneath the water table!
LNAPL beneath water table…
We believed that…
LNAPL continues to migrate once at the water table, similar to groundwater migration
FALSE! LNAPL bodies are spatially self-limiting, and
stop migrating shortly after the release is terminated!
We believed that…
No LNAPL in wells means no LNAPL at the Site
FALSE! Often times, LNAPL will be at a site and not
show up in wells!
We believed that…
LNAPL disappearing from a well for an extended period of time (years) and then reappearing indicates a new release
FALSE! Submerged LNAPL can remain in the
formation adjacent to a well for years, without appearing in the well!
We believed that…
Decreases in in-well LNAPL thicknesses during active remediation mean that the remedial program is working
FALSE! In-well LNAPL thickness may increase or
decrease in response to a fluctuating water table (with no connection to remedial progress)
In-well LNAPL thickness
changing in response to water table fluctuations
LNAPL
LNAPL
Normal Water Table
High Water Table
LNAPL
Low Water Table
LNAPL and Water Drainage
We believed that…
With the proper technologies, all LNAPL can be hydraulically recovered from the subsurface
FALSE! On average, no more than 50% of LNAPL
can be recovered (no more than 15% in finer soils)
We believed that…
All LNAPLs result in extensive groundwater contamination
FALSE! Middle distillate and heavier LNAPLs (diesel,
fuel oil, lube oil) seldom result in significant dissolved phase impacts
We believed that…
Hydraulic recovery (pumping or skimming) of LNAPL from the subsurface results in groundwater concentrations being remediated
FALSE! Hydraulic recovery of LNAPL has little to no
effect on dissolved phase concentrations!
Knowing what we now know, why do we refuse to change…
Creatures of habit – resistant to change? Don’t believe the science? Don’t trust the science? Don’t understand the science? Blame it on the existing LNAPL laws/regs
(i.e., science has advanced, laws and regulations haven’t)!
Increasing Time (Years)
Evol
utio
n of
Kno
wle
dge
Science
Regs
1987
Regs
Science
Gap
Capillary Pressure Pore Entry Disp. Pressure
Multi-Phase Fluid Flow
Van Genuchten Parameters Saturation/Residual Saturation
Mobility/Stability
Relative Permeability
Transmissivity
From the “LNAPL” beginning… Mid 1980s - retail petroleum facilities were in
a serious state of disrepair across Canada and the U.S.
Estimates indicated that as many as 1/3 of underground storage tank (UST) systems (tank and associated piping) were leaking
Numerous retail petroleum facilities with gasoline-impacted soil and groundwater
From the beginning… Existing UST systems continued to corrode
and deteriorate, leading to additional releases to the environment
Impacts were deemed to present a significant risk to human health and the environment
Some impacts required emergency measures due to severity of risks (i.e., potential explosive situations)
Government response (U.S.)…
Comprehensive federal UST regulations governing UST construction, operation, monitoring and release detection requirements
40 CFR 280 - Technical Standards and Corrective Action Requirements for Owners and Operators of Underground Storage Tanks
Government response (U.S.)…
40CFR280 requirements: • §280.43 Methods of release detection for tanks
— §280.43(f) Ground-water monitoring — §280.43(f)(6) The continuous monitoring device or
manual methods can detect the presence of at least one-eighth of an inch of free product on top of the ground water in the monitoring wells;
“One-eighth of an inch”
Government response…
40CFR280 requirements (Continued): • §280.64 Free product removal
— At sites where investigations under §280.62(a)(6) indicate the presence of free product, owners and operators must remove free product to the maximum extent practicable as determined by the implementing agency while continuing, as necessary, … [underline/bold added].
“Maximum Extent Practicable (MEP)”
These two requirements…
⅛-inch free product (in well) Remove free product to maximum extent
practicable (MEP)
Have been the source of much LNAPL debate for the past 25 years!
Why the debate…
Regulators essentially “connected” the two requirements, and made the assumption that ⅛-inch = MEP
LNAPL in Well = Unacceptable Risk = Corrective Action
Evolving environmental times for non-LNAPL impacts…
1980s – clean to background concentrations 1990s – added risk-based decision-making to
environmental cleanups (Risk-Based Corrective Action or RBCA)
2000s – RBCA with sustainability considerations
Sustainability… Considers risks to human health and the
environment, as well as balance between environmental, economic and social issues/performance
More than “Green”, which just considers environmental benefit after remedy selection
Does the proposed remedial action result in a net benefit, or detriment?
Sustainable performance…
Social Environmental
Economic Sustainable Performance
(balance between all three)
LNAPL in Well…Must Recover/Remediate
Remediate to Background
Concentrations
Risk-Based Corrective Action
(RBCA)
RBCA with Sustainability Considerations
Active Remediation
Monitored Natural Attenuation
(MNA)
1980s
1990s
2000s
LNAPL in A Well?
No Yes
Timeline
Due to the “perceived” threat, LNAPL in a well means that…
Good science is ignored Risk-based evaluations are ignored Sustainability considerations are ignored Costs are ignored
Proceed directly to recovery!
“Interpretation” of existing regs fails to recognize that… All LNAPLs are different (chemical and
physical properties) LNAPL chemical/physical properties,
geologic setting and land use dictate true risks LNAPL chemical/physical properties and
geologic setting dictate migration potential
Carbon Chain Hydrocarbon Ranges for Various LNAPLs
C1 C4 C8 C12 C16 C20 C24 C28 <C30
Gasoline (C4 – C12)
Kerosene / Jet Fuel (C6 – C18)
Diesel / No. 2 (C8 – C21)
Lube Oil (C18 – >C34)
Crude Oil (C1 – >C34)
Gases Liquids Solids @20ºC
Hydraulic Oil (C18 – C30)
LNAPLs are not created equal Light-end LNAPLs pose higher risk/toxicity
than heavier ends Light-ends more soluble than heavy ends Light-ends more volatile than heavy ends Light-ends more combustible than heavy ends
Yet, even light-ends pose less risk than originally anticipated!
Unfortunately, many regulators continue with the belief that…
All LNAPLs are equal The mere presence of LNAPL represents an
unacceptable risk requiring active recovery The absence of LNAPL in wells means the
site is clean!
As a result…
Millions of $$$ are spent on unnecessary LNAPL remediation programs
Non-sustainable LNAPL remediation practices continue to be the norm
Some high-risk sites are closed based on the absence of LNAPL in wells!
Real life non-sustainable LNAPL examples… $6.3M capital cost, $1M annual O&M After 1.5 years:
• 40 million gallons of groundwater extracted • 750,000 kWh of power consumed
— Enough to power 65 average size homes for a year! • 300 gallons LNAPL recovered
— >$25K/gallon LNAPL
WHY?
Real life non-sustainable LNAPL examples… $2.2M spent 1,655,050 kWh power consumed
• Enough to power 140 average size homes for a year!
Over 2 million pounds of CO2 emissions • Thermal oxidizer, not including power generation
3,000 gallons of LNAPL recovered
WHY?
Real life non-sustainable LNAPL examples… Diesel-powered generator to run remediation
system 4,000 gallons of diesel generator fuel
consumed per month Less than 50 gallons of diesel LNAPL
recovered per month
WHY?
Real life non-sustainable LNAPL examples… Extracted gasoline LNAPL from 10 metres
below ground and dispersed untreated gasoline vapours into residential neighbourhood
ARE WE REALLY CREATING A NET BENEFIT?
How do we fix it? It’s not the law/regulation itself, but rather the
“interpretation” of the law/regulation that needs to change
In-well LNAPL thickness should never be used as a trigger to start/stop remediation
Risk-based evaluations and sustainability considerations must be incorporated into the remedial decision-making process
How do we fix it? We must build technically sound LNAPL
Conceptual Site Models (LCSMs) and use the LCSM information as a basis for remedial decision-making (see ITRC TechReg, December 2009)
Maximum Extent Practicable (MEP) must be tied to the LCSM (including risk and sustainability considerations) – not in-well thickness
Where do we go from here… Must first educate ENVIRONMENTAL
CONSULTANTS on current LNAPL science/guidance
Next, educate/inform policymakers, regulators and the public in general about the gap between LNAPL science and regulations and the need to “adjust”
Where do we go from here… Continue to learn, develop, and promote
sustainable LNAPL management and remediation practices that provide a net benefit to all!
Eventually…good science prevails!
THANK YOU!