Page 5, 2.4, Draft Report States: “This SAP addresses only outdoor residential and community based recreational activities in OU7 because similar ABS scenarios have been performed for both interior and some exterior activities in OU4. Data from OU4, both interior and some exterior, can be used to assign human health risk in OU7.”
Comment: There are no major sources of LA within OU7, and potential exposure to LA in OU7 results from residential use of vermiculite from the Libby mine, primarily as building insulation and as a soil amendment. In contrast, there are other sources of LA within or in the vicinity of OU4. Indoor Activity-Based Sampling (ABS) in OU4 reported that indoor air concentrations tend to be lower in the winter than summer and may be related to track-in of contaminated soil from outdoor sources in winter than in summer, or to decreased aerial deposition of structures in indoor dust from outdoor ambient air (Activity-Based Sampling Summary Report Operable Unit 4, Libby, Montana, Superfund Site, June 2, 2010). Since a potential source of indoor exposure to LA results from track-in of contaminated soil from outdoor sources and aerial deposition of structures in indoor dust from outdoor ambient air, and since the sources of LA in OU7 are not the same as in OU4, how can data from OU4, both interior and some exterior, be used to assign human health risk in OU7” ?
In addition, to apply indoor data from OU4 to OU7, is it assumed that indoor LA contamination levels are the same in each OU, that home age and construction features are the same in each OU, and that the indoor activities performed in each OU are the same?
DEQ Response to Comment:
DEQ and EPA agreed that collection of indoor ABS data was not necessary for OU7 because (1) LA concentrations in indoor air based on indoor sources and indoor residential activities are not expected to differ between OU4 and OU7, and (2) LA concentrations in indoor air based on outdoor soil sources of LA are unlikely to be higher at OU7 compared with OU4. The primary indoor source of LA at OU7 is the same as OU4 – use of LA-containing vermiculite for indoor insulation in unenclosed spaces such as attic and crawl spaces and in enclosed spaces such as walls. Indoor residential ABS data were collected at OU4 for active and passive behaviors. The specific active indoor behaviors sampled at OU4 include walking around the house, sitting down on and getting up from chairs and couches, simulated play with children and pets, and housecleaning (sweeping, vacuuming, and dusting). The specific passive indoor behaviors sampled at OU4 include sitting, reading, and watching television. These active and passive behaviors are representative of long-term, recurring indoor residential behaviors, and are not expected to differ at OU7.
An additional potential source of indoor LA is LA from outdoor soil that may be tracked indoors or that may become airborne and deposited indoors. Results of the Troy Asbestos Property Investigations (TAPE) have demonstrated lower overall concentrations of LA in outdoor soil at OU7, compared with OU4. Therefore, although LA concentrations in outdoor soil differ between OU4 and OU7, use of indoor ABS data from OU4 to estimate health risks from indoor air exposure at OU 7 is a conservative approach because of the higher overall outdoor source concentrations of LA at OU4.
Page 6, List of data gaps: Data gap 4 lists “Outdoor and Tradesperson exposure to outdoor air near disturbed soil.” The six ABS scenarios planned for the outdoor ABS do not address tradesperson (commercial worker) exposure during residential renovation activities that could disturb soil such as excavation and/or landscaping. Commercial workers would be expected to work longer hours performing more extensive soil disturbing activities.
DEQ Response to Comment:
ABS data collection for worker and tradesperson exposure to LA from soil excavation and landscaping activities is ongoing at OU4; these data will be evaluated to determine if they are appropriate for assessing worker and tradesperson exposure to LA at OU7 or if additional ABS data collection for this scenario is needed at OU7 In addition, property demolitions at OU7 will also be considered for worker and tradesperson ABS sampling for OU7.
Page 9, Table 3.1, Alternative Actions; Page 10, Table 3-2, Use of Input to Resolve Question: LA fibers have been detected in ABS air samples collected in locations where the soil does not appear to be contaminated based on polarized light microscopy (PLM) analysis and visible vermiculite ranking (EPA 2010). It is possible and likely that LA fibers were detected in ABS air samples collected in locations where the soil does not appear to be contaminated because of the semi-quantitative and subjective analytical techniques with relatively low sensitivity (i.e., polarized light microscopy [PLM] and field-based visual vermiculite estimates) used to characterize the soil. Does EPA plan to use sensitive and reliable analytical methods (TEM) to characterize background levels of asbestos in soil in specific use areas and yards as part of “Alternative Actions” and/or “Use of Input to Resolve Question”?
DEQ Response to Comment:
DEQ is monitoring the development of a new analytical method for soil; TEM coupled with fluidized bed. This method appears to afford greater sensitivity than does PLM-VE. However, the method is still under development, and it is not known when it will be available for use. Until analysis using TEM coupled with fluidized bed is approved, DEQ will continue to analyze soil samples using PLM-VE.
Page 11, 3.3.4 Types of Soil Disturbances: While it is recognized that a wide variety of activities may result in outdoor disturbances of LA and it is not feasible to evaluate every type of disturbance, the following activities are not addressed in the outdoor ABS: leaf blowing, weed whacking, walkway/driveway sweeping, tree/scrub pruning. ABS for these activities should be considered.
DEQ Response to Comment:
The specific residential yard work activities identified for ABS sampling at OU7 are considered to be realistic examples of vigorous soil disturbance activities that are likely to recur on a long-term basis. The potential contribution of other residential yard work activities, such as leaf blowing, weed whacking, walkway and driveway sweeping, and tree and shrub pruning, will be qualitatively addressed in the human health risk assessment for OU7.
Page 18, 4.1.1 ABS Scenario 1: Yard Work in Residential Yards: ABS for leaf blowing, weed whacking and tree/scrub pruning should be considered.
DEQ Response to Comment:
Please see the response to the comment above.
Page 23, 4.1.3 ABS Scenario 3: Bicycling and Playing on Unpaved Residential Driveways: For the child biking activity, how will samples be collected to represent a child’s breathing zone while bike riding?
DEQ Response to Comment:
ABS samples for Scenario 3 (Child Bicycling In Driveway) will be collected from the shoulder height of the adult actor (measured at 34-36 inches above the ground), rather than from the typical breathing zone of the adult actor. The shoulder height of the actor is representative of the height of a child’s breathing zone while biking as the ABS tricycle sits lower than a child’s trike which is an appropriate sampling zone to model a child’s exposure.
Page 24, Driving Paved/Unpaved Roads: In the event that LA is detected during this activity, how will it be determined whether the LA fibers originated from outside or inside the vehicle? The vehicles used for this activity are certified as free from LA contamination, then how does this ABS represent potential exposure in vehicles which may be contaminated with LA? Will vehicle traffic during ABS be recorded?
DEQ Response to Comment:
To ensure that any LA detections noted during the driving scenario are from outside the sample vehicle, samples from inside the vehicle are also collected. For the past 4 field seasons, background microvac samples have been collected from the seats, floors, and dashboard areas of the field vehicles before initiation of field activities, monthly, and again before returning them to the rental company. All previous vehicle dust sample results have been non-detect for LA. Additionally, the vehicles are HEPA vacuumed at the end of each work week. This same procedure will be followed for both the spring and summer ABS events.
Also, traffic levels will be documented throughout the driving scenario (as light, moderate, or heavy).
In my opinion, the greatest exposure potential to LA associated with Driving Paved/Unpaved Roads would be to pedestrians traveling on these roadways and exposed to aerosols generated by passing vehicles. Is ABS planned to address this potential exposure pathway to pedestrians? Will other motorized vehicle use on unpaved roads (i.e., ATVs) be evaluated through ABS?
DEQ Response to Comment:
The ABS data collected for scenario will be used to evaluate potential health risks from exposure to vehicle occupants from LA in soil and road surfaces that may be disturbed from the vehicle while moving. Data from ongoing ambient air sampling at OU7, which represents data from multiple outdoor sources including vehicular traffic, can be evaluated in the event that anomalous ABS results for this scenario are reported.
ABS sampling for a pedestrian scenario is not planned for OU7. However, ABS data collected for the driving scenario and ambient air data for OU7 can be used to qualitatively evaluate potential LA exposures to pedestrians.
ABS sampling for the driving scenario will include driving on unpaved roads. Specific sampling for ATV use on unpaved roads is not planned for OU7; however, ABS data collected from the driving scenario and from the bicycling scenario can be used to qualitatively evaluate potential LA exposures to ATV riders.
Page 25, 4.1.5 ABS Scenario 3: Bicycling on Paved and Unpaved Roads, Alleys, and Trails:
In my opinion, the greatest exposure potential to LA associated with Bicycling on Paved and Unpaved Roads would be to aerosols generated by passing vehicles. Will vehicle traffic during ABS be recorded?
DEQ Response to Comment:
Please see the response to the comment above.
Page 31, MET Data: The Draft Report indicated that ABS would be suspended during rain events. Will ABS be suspended during high wind events?
DEQ Response to Comment:
ABS sampling will not be suspended during high wind events since wind erosion is also a potential source of airborne LA concentrations. Data from ongoing ambient air sampling at OU7 (ambient air samples are collected from upwind and downwind locations) and from the DEQ meteorological station at OU7 (measurements are recorded hourly at the station, including measurements of wind speed) can be evaluated if anomalous results for the outdoor ABS scenarios are reported and high winds are suspected.
Page 34, 4.3.5 Air Sample Collection: “During residential ABS Scenarios 1, 2, and 3, one participant will perform the scripted activities and will wear two different air sample pumps calibrated at two flow rates. The primary sample will be collected using battery-powered sampling pumps capable of operating at 4 liters per minute (L/min). The pump flow rate will be adjusted to 4 L/min to obtain sample volumes of at least 240 L. In addition, a battery-powered sampling pump capable of operating at 2 L/min will be used to generate a backup air sample in the event the primary sample is damaged or overloaded.”
Comment: The Activity-Based Sampling Summary Report Operable Unit 4, Libby, Montana, Superfund Site, June 2, 2010, states: “The high volume sample was collected using a pump with a flow rate of 10 L/min (total air volume of 1,200 L), and the low volume sample was collected using a pump with a flow rate of 3 L/min (total air volume of 360 L) (EPA 2007d). The high volume sample was analyzed in preference to the low volume sample because maximizing the total air volume collected reduced the level of effort needed to achieve the target analytical sensitivity.”
DEQ Response to Comment:
Why is the ABS methodology employed for OU7 where the minimum target sample volume is 240 L different than the ABS methodology employed for OU4 where the target sample volume was 1,200 L?
ABS target sample volume of 240 liters for OU7 is consistent with residential scenario sampling presented in the June 18, 2010 OU4 Supplemental Activity-Based Sampling SAP. DEQ chose to follow the sampling time of sixty minutes at a flow rate of 4 liters per minute used in OU4 within OU7 for the following reasons.
· At 1 hour in duration, the residential scenarios are considered representative of actual yard work conditions
· At 240 liters, analytical sensitivity of 0.001 fibers per cc can be met through the counting of a reasonable number of grid openings during analysis(160)
· Counting of 160 grid openings was weighed against longer sampling times (more sample volume and counting of fewer grid openings during analysis) and was determined to be the most efficient use of resources
Sample collection volumes of 240 liters was applied to all residential and community scenarios in OU7, with the exception being the driving scenario where a total sample volume of 600 liters was collected during a 60 minute period at 10 liters per minute.
Will perimeter samples be collected to document migration concurrent with the activity-based sampling? Will background samples be collected, concurrent with and upwind in the same general area as the activity-based sampling?
DEQ Response to Comment: Ambient air sampling is ongoing at OU7; ambient air data will be obtained concurrently with ABS data collection at OU7. The ambient air stations at are located within, upwind, and downwind of OU7. While these stations are not specifically located along the perimeter of the OU7 study area, the stations are located to identify any significant differences in LA levels in ambient air resulting from time or location.
