This document discusses the use of a HAPSITE® GC/MS portable gas chromatograph/mass spectrometer for vapor intrusion investigations at a site with trichloroethene impacts. The HAPSITE® was used to monitor indoor air concentrations in real-time, identify vapor intrusion sources, and evaluate interim remedial actions. Comparisons with standard TO-15 laboratory methods found HAPSITE® results were consistently higher but provided conservative screening. Over 17,000 HAPSITE® analyses were performed in a cost effective and timely manner to thoroughly characterize vapor intrusion. Lessons learned include the importance of capturing variability, battery life limitations, and preventing dust/water in the probe during investigations.
8 hour TWA summa canister sampling is the gold standard methodology for evaluating indoor air concentrations and VI at a project site.
Everybody here is aware of the limitations of summa sampling from both a time and cost perspective.
In Rod’s presentation, you heard about the soil vapor plume that most of the CRREL facility sits over.
CRREL is a very challenging vapor intrusion site and we used the HAPSITE® as a more comprehensive and cost effective tool to investigate the VI pathways and TCE IA concentrations to be protective of human health for Site employees.
Whenever I bring a HAPSITE® to a project, someone invariably asks me what does HAPSITE® stand for.
HAPSITE® is an acronym for Hazardous Air Pollutants On SITE.
The HAPSITE® is a field portable GC/MS equipped with an integrated sample collection system.
The sample collection systems are plug and play and allow you to analyze air, water, or solid matrices.
The HAPSITE® is essentially a miniaturized field portable version of a GC/MS found sitting on the bench in a fixed base laboratory.
Why use the HAPSITE® at CRREL?
IA TCE observed during bi-annual sampling presented concentrations above the 8.8 ug/m3 site specific interim action level, with concentrations ranging as high as 200 ug/m3.
These concentrations were not spatially reproducible from one sampling event to another.
Use of the summa canister sampling protocol, the delay of TO-15 result reporting and the interval between sampling events made it difficult to track down VI pathways and interior sources.
Due to the variability in the data, associated with daily changes in building operations, climatic changes, and emissions, real time assessment of VI and IA conc. was needed and the HAPSITE® fit the bill.
Use of the HAPSITE® provides a more complete and multi faceted data set to support
Monitoring indoor air TCE concs for protection of human health
Identifying VI pathways and investigating VI sources
Monitoring interim actions and pilot tests to evaluate their efficacy
And provide analytical capabilities to support sampling activities such as soil gas plume monitoring
The HAPSITE®s in use at CRREL are owned by the Army. The HAPSITE® can be rented from other vendors however there is typically a high demand and limited supply of rental units available.
The work platform set up pictured here allows us to transport the HAPSITE® around the CRREL facility and collect and analyze upwards of 30 samples during an 8 hour day.
In this configuration, the HAPSITE® can also be easily removed from the platform for access into even more remote locations.
By the way, for any of you who are interested, the work platform configuration that you see here is patent pending at this time
There are multiple HAPSITE® investigation techniques that we used at CRREL and they include……….
Edit this to add time
Here is an example of single point analysis for monitoring interim action effects
An area exhaust fan located in the Main Lab sub-basement was suspected of enhancing conditions to support active VI.
The fan was discovered on and IA conc.’s were measured at a similar location at each of the four floors from the sub-basement up to the second floor.
Differential pressure across the sub-basement slab was measured throughout this test interval and corroborates the VI activity identified by the HAPSITE analyses.
Ventilation fan enhanced VI increased IA TCE conc. in the sub-basement which were then distributed to the floors above.
In this example, HAPSITE analyses were performed every 6 minutes, across multiply locations during a limited 7 hour interval.
Upon completion of the test, CRREL facility operations were informed to leave the fan off.
On a large and complex project Site such as CRREL, there are multiply areas to investigate and interim actions to monitor.
In this example, SSDS bi-monthly samples of influent, mid-fluent, and effluent are analyzed at CRREL to monitor the performance of the SSDS in the MPR area of the Main Lab basement.
The influent data is presented here in reference to the operations of the SVE Pilot to evaluate the effects the SVE Pilot is having on soil vapor concentrations.
In this scenario, the HAPSITE is utilized to analyze monitoring samples collected over a longer term (presently 1 ½ years) and is another example of how the HAPSITE is used at CRRE.
Really couldn’t have done this with a summa.
The tedlar bag and flux chamber sampling techniques are grab samples.
Tedlar bags are used at CRREL to collect IA samples at alternate locations while the HAPSITE is running somewhere else.
We also use tedlar bags to collect large numbers of samples during comprehensive sampling rounds. During the October 2015 comprehensive soil gas sampling round, we collected 247 soil gas samples at CRREL and the abutting properties over the course of three days. Using two HAPSITEs and two operators, one of which was dedicated to sampling during the first two days, we completed HAPSITE analyses of those soil gas samples in four days. HAPSITE analysis began on the second day of sampling.
Flux chambers are an effective tool to isolate a suspected VI pathway and analyze it to evaluate it’s contributions to IA TCE concentrations.
I would like to bring to your attention the flux chambers in place around the roof drain cleanout…….in this particular example, after the flux chamber was installed we observed and immediate reduction to the TCE concentration in indoor air within that area.
At CRREL, we used the HAPSITE to analyze building materials in the Main Lab, such as blueboard insulation and concrete cores to determine whether or not they have been affected by legacy TCE.
Headspace analysis was also used at CRREL to determine whether or not the former TCE brine lines used to supply coolant to the cold rooms area have affected the ethylene glycol used as a heat transfer fluid today.
Recall from the previous slide, the flux chambers around the roof drain cleanouts. The results from those investigations led us to install check valves in the drain pipes to prevent TCE vapors from storm drains entering the building through the old pipes and connections.
Because the HAPSITE is capable to be deployed quickly, we are able to respond to requests for analyses in a very short time. As an example, during a peer review meeting at CRREL, questions arose regarding how well the recently installed check valve was working. We were able to deploy the HAPSITE and analyze an above and below sample and report the results while discussions were still occurring.
In 2013 , a 24 day study was performed using 8-hour summa canisters with TO-15 analysis and co-located 8-hour bottlevacs with HAPSITE analysis.
Results reported around the Site specific action limit of 8.8 ug/m3 were evaluated.
The results were averaged over five days and the BV-HAPSITE data was compared to the summa-TO-15 data. What we found was the BV-HAPSITE results reported higher than the summa-TO-15 results by an average factor of 2 times
This comparison indicates that the BV-HAPSITE data provides a high bias to results that would be reported by the summa-TO-15 methods. This bias adds a conservative understanding of TCE IA concentrations when compared to the site specific interim action level.
In support of the bi-annual sampling program at CRREL, over 1000 IA summa samples have been collected and analyzed from 2010 to date.
At CRREL, from Sept 2012 thru mid- April 2016, over 14,000 IA HAPSITE samples have been analyzed.
The HAPSITE per sample cost is $58 vs a $225 per sample TO-15 cost and provides a 10 minute TAT vs a standard 30 day TO-15 TAT
The HAPSITE is a cost effective tool that provides real time results which we use at CRREL to better understand VI and IA trends, and to effect targeted interim mitigation efforts and monitor the efficacy of their operations.
To the best of my knowledge CRREL may be the third most studied IA/VI site; other Indoor Air data sets more comprehensive than CRREL are Dr. Paul Johnson’s with Arizona State University and Dr Erik Dettenmeiars data set from Hill AFB.
If you know of others I would like to hear about them after this presentation.
The bi-annual TO-15/Summa data in the upper chart does not present the same picture of IA that is presented by the HAPSITE chart.
The story told by the HAPSITE data shows periodic excursions above the interim action level for the CRREL Site and really presents the true variability of VI and IA that is affected by daily climatic changes (barometric changes), building operations, and emissions.
Real time Hapsite data captures the true variability of IA conc and can be more protective of human health when compared to the summa/TO-15 data.
