HRS DOCUMENTATION RECORD--REVIEW COVER SHEET

Name of Site: Wolff-Alport Chemical Company

CERCLIS ID No.: NYC200400810

Date Prepared: December 2013

Contact Persons

Site Investigation: Dennis Munhall (212) 637-4343

U.S. Environmental Protection Agency (EPA)

New York, NY

Documentation Record: James Desir (212) 637-4342 

U.S. Environmental Protection Agency (EPA)

New York, NY

Pathways, Components, or Threats Not Scored

The ground water migration, surface water migration, and soil exposure pathways were not scored because the 

listing decision is not affected significantly by those pathways. The site score is sufficient to list the site on the air 

migration pathway score.

The effects on the ground water migration pathway are unknown. During a 2009 investigation, downhole gamma 

logging indicated that soil contamination extends to 20 feet below ground surface (bgs) and possibly deeper; this 

deep contamination is believed to result from soluble thorium that could be highly mobile in the subsurface [Ref. 5, 

pp. 38-43, 47, 57]. Ground water samples could not be collected during the 2009 investigation because ground 

water was not encountered in on-site soil borings or monitoring wells completed to a maximum depth of 37 feet bgs 

[Ref. 5, p. 23; 29, p. 15; 30, pp. 7-10, 18]. Ground water is expected to be present at approximately 50-60 feet 

below ground surface at the site [Ref. 29, pp. 15-16, 61].

The surface water migration and soil exposure pathways are adversely affected, as the information in the HRS 

documentation record indicates. There is observed soil contamination at and around the property formerly occupied 

by Wolff-Alport Chemical Company (WACC) and under neighboring streets and sidewalks where workers, 

customers, and pedestrians have been observed by EPA (see Section 2.2 of this HRS documentation record) [Ref. 

19, pp. 30-33] In addition, WACC discharged its thorium waste to the sewer system until 1947, and recent 

investigations have indicated that residual contamination still exists in or around the sewer lines downstream of the 

facility. During periods of heavy flow such as rainstorms, combined sewer overflows (CSO) discharge from this 

combined sewer system to Newtown Creek west of the subject property [Ref. 5, pp. 6-7, 10; 6, pp. 9-11; 12, pp. 2, 

5]. 

Note: As shown in this HRS documentation record, the Wolff-Alport Chemical Company site contains radioactive 

substances. Therefore, the air migration pathway for the site is evaluated according to HRS Section 6.0, 

supplemented by HRS Section 7.0. The following air migration pathway factors are evaluated differently for this 

site than for sites containing only nonradioactive substances: Observed Release, Toxicity, Hazardous Waste 

Quantity, Nearest Individual, and Population. The difference for the Nearest Individual and Population factors is in 

the determination of Level I and Level II concentrations [Ref. 1, Section 7.0, Table 7-1]. All other air migration 

pathway factors are not evaluated differently and are not addressed in HRS Section 7.0. The HRS documentation 

record cites the appropriate sections and tables of the HRS.
This page has been left blank intentionally.
HRS DOCUMENTATION RECORD

Name of Site: Wolff-Alport Chemical Company Date Prepared: December 2013

CERCLIS ID: NYC200400810

EPA Region: 2 

Street Address of Site: * 1125-1139 Irving Avenue, Ridgewood, NY 11385

County and State: Queens, NY

General Location in the State: border of Brooklyn and Queens Boroughs, New York City

Topographic Map: Brooklyn, NY

Latitude: * 40° 41’ 33.62” North Longitude: * 73° 54’ 7.19” West

Site Reference Point: Sample location WAC-SPUR-02 (GPS measurement within the source area)

[Ref. 3, p. 1; 4, p. 1; 5, p. 5; 19, p. 8; 27, pp. 1, 3; Figures 4, 7 of this HRS documentation record] 

* The street address, coordinates, and contaminant locations presented in this HRS documentation record identify 

the general area in which the site is located. They represent one or more locations EPA considers to be part of the 

site based on the screening information EPA used to evaluate the site for NPL listing. EPA lists national priorities 

among the known “releases or threatened releases” of hazardous substances; thus, the focus is on the release, not 

precisely delineated boundaries. A site is defined as where a hazardous substance has been “deposited, stored, 

disposed or placed, or has otherwise come to be located.” Generally, HRS scoring and the subsequent listing of a 

release merely represent the initial determination that a certain area may need to be addressed under CERCLA. 

Accordingly, EPA contemplates that the preliminary description of facility boundaries at the time of scoring will be 

refined as more information is developed as to where the contamination has come to be located.

 Scores

Ground Water Pathway Not Scored

Surface Water Pathway Not Scored

Soil Exposure Pathway Not Scored

Air Pathway 100.00

HRS SITE SCORE 50.00

1 
2

WORKSHEET FOR COMPUTING HRS SITE SCORE

Wolff-Alport Chemical Company

 S S2

 

1. Ground Water Migration Pathway Score (Sgw) Not Scored

(from Table 3-1, line 13)

2a. Surface Water Overland/Flood Migration Component Not Scored

(from Table 4-1, line 30)

2b. Ground Water to Surface Water Migration Component Not Scored

(from Table 4-25, line 28)

2c. Surface Water Migration Pathway Score (Ssw) Not Scored

Enter the larger of lines 2a and 2b as the pathway score.

3. Soil Exposure Pathway Score (Ss) Not Scored

(from Table 5-1, line 22)

4. Air Migration Pathway Score (Sa) 100.00 10,000.00

(from Table 6-1, line 12)

5. Total of S 2 gw + S 2 sw + S 2

s + S 2a 10,000.00

6. HRS Site Score Divide the value on line 5

 by 4 and take the square root 50.00
3

AIR MIGRATION PATHWAY SCORESHEET

Wolff-Alport Chemical Company

AIR MIGRATION PATHWAY

Factor Categories & Factors

MAXIMUM

VALUE

VALUE

ASSIGNED

Likelihood of Release

1. Observed Release

2. Potential to Release:

 2a. Gas Potential to Release

 2b. Particulate Potential to Release

 2c. Potential to Release (higher of lines 2a and 2b)

3. Likelihood of Release (higher of lines 1 and 2c)

550

500

500

500

550

550

not scored

not scored

not scored

550

Waste Characteristics

4. Toxicity/Mobility

5. Hazardous Waste Quantity

6. Waste Characteristics

 * 

 * 

100

2 

100

3 

Targets

7. Nearest Individual

8. Population

 8a. Level I Concentrations

 8b. Level II Concentrations

 8c. Potential Contamination

 8d. Population (lines 8a+8b+8c)

9. Resources

10. Sensitive Environments:

 10a. Actual Contamination

 10b. Potential Contamination

 10c. Sensitive Environments (lines 10a + 10b)

11. Targets (lines 7+8d+9+10c) 

50

**

**

**

**

 5 

 ***

 ***

 ***

 ***

45

0 

6,870.79

not scored

6,870.79

not scored

not scored

not scored

not scored

not scored

6,915.79

12. AIR PATHWAY SCORE (lines 3 x 6 x 

11)/82,500****

100 100.00

* Maximum value applies to waste characteristics category.

** Maximum value not applicable

*** No specific maximum value applies to factor. However, pathway score based solely on sensitive 

environments is limited to maximum of 60.

**** Do not round to nearest integer.
4

REFERENCES

Reference

Number Description of the Reference

1. U.S. Environmental Protection Agency (EPA). Revised Hazard Ranking System, Final Rule, 40 CFR 

300, Appendix A. Federal Register. December 14, 1990. A complete copy of the rule is available at 

http://www.epa.gov/superfund/sites/npl/hrsres/index.htm#HRS Rule. [137 pages]

2. EPA. Superfund Chemical Data Matrix (SCDM) – excerpts. Accessed and printed from 

http://www.epa.gov/superfund/sites/npl/hrsres/tools/scdm.htm on July 2, 2013. [26 pages]

3. EPA. Search Superfund Site Information, Wolff-Alport Chemical Company. Accessed and printed 

from http://cumulis.epa.gov/supercpad/cursites/csitinfo.cfm?id=0206479 on June 14, 2012. [1 page] 

4. U.S. Department of the Interior Geological Survey (USGS). Brooklyn Quadrangle, New York, 7.5-

Minute Series (Topographic). 2010. [1 page]

5. Louis Berger & Assoc., PC (LBA). Final Draft Radiological Scoping Survey for Former Wolff-Alport 

Chemical Corporation Site, 1125-1139 Irving Avenue, Queens, New York 11385, DDC Project No. 

BEGS 2008007. Prepared for New York City Department of Design and Construction (NYCDDC). 

August 23, 2010. [287 pages]

6. U.S. Department of Health and Human Services, Agency for Toxic Substances and Disease Registry 

(ATSDR). Health Consultation, Former Wolff-Alport Chemical Corporation Site, 1125-1139 Irving 

Avenue, Queens, New York. February 29, 2012. [44 pages]

7. Fiore, James J., Director, Division of Facility and Site Decommissioning Projects, Office of Nuclear 

Energy, U.S. Department of Energy (DOE). Letter to Dr. L. R. Solon, Director, Bureau of Radiation 

Control, New York City Department of Health (NYCDOH), with attachment, RE: Wolff-Alport 

Chemical Corporation. September 29, 1987. [8 pages]

8. Cook, R.W., Director of Production, DOE. Office Memorandum to Jesse C. Johnson, Manger of Raw 

Materials, Operations Office, Subject: Thorium Procurement. March 19, 1951. [1 page]

9. New York State Department of Environmental Conservation (NYSDEC). Former Wolff-Alport 

Chemical Company, Site Visit Report. Site visit date: May 5-6, 2007. [9 pages]

10. Morofsky, Basia and Michael Funaro, Environmental Sciences and Engineering, New York City 

Department of Health and Mental Hygiene (NYCDOHMH). Wolff Alport: Sample Survey Results, 

Interior Limited Gamma Radiation Survey. July 30, 2007. [1 page]

11. NYCDOHMH. Information on Radiation Survey at the Former Wolff-Alport Chemical Corporation, 

1127-1129 Irving Avenue, Queens, NY. September 5, 2007. [3 pages]

12. Magriples, Nick, On-Scene Coordinator, Removal Assessment and Enforcement Section, EPA. 

Memorandum to File, Subject: Removal Site Evaluation for Wolff-Alport Chemical Company, 

Borough of Queens, Queens County, New York. May 4, 2012. [54 pages]

13. Environmental Data Resources, Inc. (EDR). The EDR Radius MapTM Report with GeoCheck®, 

Former Wolff-Alport Chemical Company, 1125 Irving Avenue, Ridgewood, NY 11385, Inquiry 

Number: 3364844.2s. July 11, 2012. [277 pages]
5

REFERENCES (continued)

Reference

Number Description of the Reference

14. EDR. The EDR-City Directory Abstract, Former Wolff-Alport Chemical Company, 1125 Irving 

Avenue, Ridgewood, NY 11385, Inquiry Number: 3364844.6. July 11, 2012. [13 pages]

15. EDR. Certified Sanborn® Map Report, Former Wolff-Alport Chemical Company, 1125 Irving 

Avenue, Ridgewood, NY 11385, Inquiry Number: 3364844.3. July 12, 2012. [53 pages]

16. EDR. The EDR Aerial Photo Decade Package, Former Wolff-Alport Chemical Company, 1125 Irving 

Avenue, Ridgewood, NY 11385, Inquiry Number: 3364844.5. July 12, 2012. [10 pages]

17. EDR. The EDR Chain of Title Report, Former Wolff-Alport Chemical Company, 1125 Irving 

Avenue, Ridgewood, NY 11385, Inquiry Number: 3364844.12. July 24, 2012. [70 pages]

18. Schery, S.D., Associate Professor of Physics, Physics Department and Geophysical Research Center, 

New Mexico Institute of Mining and Technology. Thoron in the Environment. Journal of Air & 

Waste Management Association, Vol. 40, No. 4. April 1990. [5 pages]

19. Weston Solutions, Inc. (WESTON). Field Logbook and Field Data Sheets, Wolff-Alport Chemical 

Company Site, Queens, NY. June 28, 2012 to September 21, 2012. [60 pages]

20. Gilliland, Gerald V., Senior Technical Manager and Nels R. Johnson, Certified Health Physicist, 

WESTON. Trip Report, Wolff-Alport Chemical Company, Document Control No. 1866-2A-BBUS. 

November 5, 2012. [46 pages]

21. Gilliland, Gerald V., Senior Technical Manager, WESTON. Project Note to Wolff-Alport Chemical 

Company file, with attachments, Subject: Population Factor Evaluation. June 25, 2013. [154 pages]

22. Argonne National Laboratory, EVS. Natural Decay Series: Uranium, Radium, and Thorium. Human 

Health Fact Sheet, August 2005. [4 pages]

23. General Electric Company. Fact Sheet, GE Energy, Reuter-Stokes 131 Environmental Radiation 

Monitor. 2004. [2 pages]

24. Durridge Company Inc. RAD7 Radon Detector User Manual, Version 7.1.8. 2012. [69 pages]

25. Gilliland, Gerald V., Senior Technical Manager, WESTON. Project Note to Wolff-Alport Chemical 

Company file, with attachments, Subject: Calculation of Mean Site-Specific Background 

Concentration and Standard Deviation, and Determination of Observed Release. March 11, 2013. [5 

pages]

26. Röttger, A. and A. Honig, Physikalisch-Technische Bundesanstalt (PTB). Recent Developments in 

Radon Metrology: New Aspects in the Calibration of Radon, Thoron and Progeny Devices. Radiation 

Protection Dosimetry (2011), pages 1-7. April 5, 2011. [7 pages]

27. Gilliland, Gerald V., Senior Technical Manager, WESTON. Project Note to Wolff-Alport Chemical 

Company file, with attachment, Subject: Latitude and Longitude Coordinates. May 31, 2013. [3 

pages]
6

REFERENCES (continued)

Reference

Number Description of the Reference

28. WESTON. Sampling and Analysis Quality Assurance Project Plan (SAQAPP), Preliminary 

Assessment/Site Inspection, Wolff-Alport Chemical Company Site, Ridgewood, Queens County, New 

Jersey. September 2012. [34 pages]

29. LBA. Final Phase I Environmental Site Assessment Report for Former Wolff-Alport Chemical 

Corporation Site, 1125-1139 Irving Avenue, Queens, New York 11385, DDC Project No. BEGS 

2008007. Prepared for NYCDDC. May 26, 2010. [720 pages]

30. LBA. Final Phase II Environmental Site Investigation Report for Former Wolff-Alport Chemical 

Corporation Site, 1125-1139 Irving Avenue, Queens, New York 11385, DDC Project No. BEGS 

2008007. Prepared for NYCDDC. August 23, 2010. [373 pages]

31. Environmental Measurements Laboratory (EML), DOE. HASL-300, EML Procedures Manual, 28th

Edition – excerpts. February 1997. Accessed and printed on July 1, 2013 from 

http://www.nbl.doe.gov/htm/EML_Legacy_Website/ProcMan/Start.htm [28 pages]

32. EPA. Soil Screening Guidance for Radionuclides: User’s Guide; excerpts. Office of Solid Waste and 

Emergency Response, publication EPA/540-R-00-007. October 2000. [24 pages]

33. Daly, Eric M., On-Scene Coordinator, EPA. POLREP #8, Pollution/Situation Report, Wolff-Alport 

Radiological Site. June 3, 2013. [6 pages]
7

SS – Site Summary

SITE SUMMARY

The contaminated soil source associated with the Wolff-Alport Chemical Company (WACC) site (CERCLIS ID No. 

NYC200400810) is located at 1125 to 1139 Irving Avenue and 1514 Cooper Avenue in Ridgewood, Queens 

County, New York, at the county border with Brooklyn [Ref. 3, p. 1; 4, p. 1; 5, pp. 11, 41-47]; the location is shown 

in Figure 1. The site includes property contaminated with radioactive thorium-232 and an associated contaminant 

release to the air migration pathway (see Sections 2.2 and 6.1 of this HRS documentation record). WACC operated 

at the property from the 1920s until 1954, importing monazite sand via a rail spur and extracting rare earth metals

from the material [Ref. 5, pp. 141-142, 153-154, 175-181; 17, pp. 9-11]. Monazite contains approximately 6% to 

8% or more of thorium [Ref. 5, p. 142]. Until 1947, WACC disposed of the thorium waste from monazite sand

processing in the sewer (process liquors) and possibly by burial on the property (waste tailings) [Ref. 5, pp. 6-10; 6, 

pp. 8-9; 7, pp. 5, 7]. According to the U.S. Department of Energy (DOE), the Atomic Energy Commission (AEC) 

ordered WACC to halt sewer disposal of thorium waste in the fall of 1947 [Ref. 7, p. 5]. Thereafter, thorium was 

precipitated as thorium oxalate sludge and sold to the AEC [Ref. 5, p. 153, 175-181; 7, p. 5]. Documents indicate 

that WACC sold approximately 53,000 pounds and 238 drums of thorium oxalate sludge to the AEC from 1948 to 

1954, and offered 400 pounds of thorium nitrate for sale to the AEC in 1954 [Ref. 5, pp. 13, 153, 175-181; 7, p. 5; 8, 

p. 1]. The thorium nitrate was reported to be 15 years old when it was offered to the AEC [Ref. 5, p. 176].

During its years of operation, WACC occupied three structures under the address of 1127 Irving Avenue [Ref. 5, pp. 

16-18; 14, p. 12; 15, pp. 48-49; 17, pp. 9-11]. The operation also included two yard areas: one between the former 

company's buildings facing Irving Avenue, and the other on the eastern end of the property at the north end of 

Moffat Street [Ref. 5, pp. 16-18; 15, pp. 48-49; 16, p. 5]. These former yard areas, now occupied primarily by 

structures, were reportedly used as staging areas for monazite sands or waste tailings containing thorium-232 [Ref. 

5, pp. 16-19; 12, p. 4]. WACC did not operate out of 1125 I rving Avenue or 1514 C ooper Avenue, but those 

properties are affected by the radioactive materials at the site [Ref. 5, pp. 16-17, 41-47, 52]. The facility layout circa 

1954 and the current property boundaries (i.e., lot lines) are shown in Figure 2. 

The nearly triangular subject property affected by contamination, which includes Lots 31 (partial), 33, 42, 44, 46, 

and 48 of Queens Borough Block 3725, covers approximately 0.75 acre bound by Irving Avenue to the southwest, 

Cooper Avenue to the northwest, and an active cabinet manufacturer to the east [Ref. 5, p. 11]. Currently, the 

property is covered primarily with contiguous structures, except that the former rail spur along its eastern edge is an 

unpaved, vegetated area where the tracks are no longer present [Ref. 5, p. 19; 19, pp. 3-5, 30-35]. The buildings

contain a delicatessen/grocery, office space, residential apartments, tire shop, and former mini-ATV shop (1125 

Irving Avenue; Lot 46); an auto repair shop and office space (1514 Cooper Avenue; Lot 48); an auto body shop 

(1127 Irving Avenue; Lot 44); and two warehouses (1129 Irving Avenue; Lot 42 and 1133-1139 Irving Avenue; Lot 

33) [Ref. 5, p. 11; 19, pp. 30-35]. The former rail spur (portion of Lot 31) is mostly vegetated and has a fence at both 

ends, but the access gates are damaged and there is graffiti on the backs of the on-source buildings; the area is used 

for storage of large, steel crane equipment [Ref. 12, p. 1; 19, p. 30, 39, 48-51]. The subject property lot boundaries 

and current uses are depicted in Figure 3. 

The site and related thorium-232 gamma radiation and daughter products of the thorium-232 decay chain may pose a 

danger to both the large population in the surrounding area and residents, workers, and students in close proximity to 

the former WACC facility property. Gamma radiation was detected along Irving Avenue where there is pedestrian 

and worker traffic. The neighborhoods surrounding the subject property contain light industry, commercial 

businesses, and residences [Ref. 12, p. 2]. The sidewalk and street along Irving Avenue are typically filled with 

vehicles being serviced by the businesses at the property [Ref. 12, p. 4; 19, pp. 31-33, 37, 40-42]. EPA observed 

workers, customers, and pedestrians on the sidewalks and streets surrounding the subject property, including a 

steady stream of customers to the deli/grocery [Ref. 19, pp. 30-33]. The intersection of Irving Avenue and Moffat 

Street (i.e., the south corner of the subject property) is an active area for trailer parking and unloading [Ref. 12, p. 4; 

19, pp. 38, 44-45]. There are three currently unoccupied apartments over the delicatessen/grocery, and other 

housing begins across the street on both Cooper and Irving Avenues [Ref. 19, p. 30; 21, p. 2]. The residential area is 

densely populated and contains multi-family homes and apartments, and a public elementary school is located 900 

feet to the southwest [Ref. 12, p. 2; 19, pp. 3-5; 21, pp. 2-4, 153-154], . An active rail line passes within 125 feet 

southeast of the subject property, and the Cemetery of the Evergreens is present to the east and south on the opposite 

side of the active rail line [Ref. 4, p. 1; 12, p. 2]. 
8

SS – Site Summary

SITE SUMMARY (continued)

Radiological surveys by City, State, and Federal agencies have identified radioactivity above background levels 

within portions of subject property buildings, in soils beneath and around the former WACC facility and adjacent 

buildings, and above adjacent sidewalks, streets, and sewers [Ref. 5, pp. 5-10, 98-118, 131-136; 9, pp. 1-9; 10, p. 1; 

11, pp. 1-3]. During an investigation by New York City Department of Design and Construction (NYCDDC) in 

2009-1010, waste tailings consisting of black or gray ash-like material were found in a contaminated soil layer 

beneath subject property buildings, beneath sidewalks and asphalt surfaces of Irving Avenue and Moffat Street, and 

within the surface soils of the former rail spur [Ref. 5, pp. 38-43]. The depth of visually-contaminated soil at the 

subject property is typically within the top 1 to 4 feet under the pavement or ground surface, however, a lens was 

reported at 8 to 10 feet beneath the auto body shop [Ref. 5, pp. 43, 56]. Thorium-232 concentrations up to 1,133 

picocuries per gram (pCi/g) were reported for the soil samples containing waste, while background was reported to 

be 0.5 pCi/g to 1.0 pCi/g [Ref. 5, pp. 41-46]. The soil screening concentration for cancer corresponding to that 

concentration that corresponds to the 10-6 individual cancer risk for oral (ingestions) exposures of thorium-232 is 

3.4 pCi/g [Ref. 1, Section 7.3.2; 2, p. 16]. The NYCDDC soil sampling results are depicted in Figure 3. 

The radioactive decay of thorium-232, which has a half-life of 14 billion years, proceeds as follows (radioactive 

half-lives in parentheses): radium-228 (5.8 years), actinium-228 (6.1 hours), thorium-228 (1.9 years), radium-224 

(3.7 days), radon-220 (56 seconds), polonium-216 (0.15 second), lead-212 (11 hours), bismuth-212 (61 minutes), 

polonium-212 (310 nanoseconds) and thallium-208 (3.1 minutes), and lead-208 (stable) [Ref. 22, pp. 1, 4]. Due to 

the length of time since processing of the monazite sands (about 60 years or more), it is reasonable to assume secular 

equilibrium (i.e., the activities of all radionuclides within the series are nearly equal) for these radionuclides in the 

waste materials abandoned at the site [Ref. 22, p. 1]. One of the key components of the thorium-232 decay series is 

radon-220, a radioactive gas commonly and hereinafter referred to as thoron, which emanates from surfaces where 

thorium-232 is present [Ref. 18, p. 1; 22, pp. 1, 4]. One of the hazards associated with airborne thoron comes from 

its radioactive decay products, a large fraction of which remain suspended in the air where they can be inhaled and 

deposited in the lungs; the primary health hazard is lung cancer due to alpha particle radiations from these decay 

products after they have been deposited on the bronchial epithelium of the lung [Ref. 18, p. 3]. During the 

NYCDDC investigation at the WACC subject property, thoron was detected in the deli basement at a concentration 

of 12.7 picocuries per liter (pCi/L) [Ref. 5, p. 52]. 

In September 2012, the U.S. Environmental Protection Agency collected gamma radiation exposure rate

measurements and thoron concentration measurements on and around the perimeter of the source area and at 

background locations [Ref. 19, pp. 5-12; 20, pp. 3-9]. The measurement locations are shown in Figure 4. The 

gamma radiation exposure rate measurements identified hot spots along the former rail spur and in the sidewalks and 

streets adjacent to the former facility, as shown in Figures 5 and 6. The contaminated area (i.e., the source area), 

defined as the extent at which the gamma radiation exposure rates equal or exceed two times the site-specific 

background gamma radiation exposure rate, extends throughout most of the subject property and in some of the 

street and sidewalk areas, as discussed in Section 2.2 of this HRS documentation record and depicted in Figure 6. 

EPA evaluated an observed release for the air migration pathway by collecting real-time thoron gas concentration 

measurements at and in the vicinity of the WACC former facility in September 2012. At selected locations in 

background areas, above the source material, and outside the boundary of the source area, thoron gas concentration 

measurements in pCi/L were collected with RAD7 Radon Detectors [Ref. 19, p. 19; Ref. 20, pp. 5-12, 23-29]. Each 

thoron measurement location coincided with a gamma radiation exposure rate measurement location to identify its 

relative location with respect to the source boundary, as shown in Figure 4. For radionuclides that occur naturally, 

observed release for a migration pathway is established when a measured concentration in units of activity (e.g., 

pCi/L) is at a level that equals or exceeds a value two standard deviations above the mean site-specific background 

concentration for that radionuclide in that type of sample [Ref. 1, Section 7.1.1]. Based on that criterion, thoron gas 

concentrations at levels significantly above the mean site-specific background concentration (0.69 pCi/L) were 

measured in air above the source material and outside the source boundary at the WACC site, as discussed in 

Section 6.1.1 of this HRS documentation record shown in Figure 7. Based on these results, an observed release to 

the air migration pathway is established, as discussed further in Section 6.1.1.
9

SS – Site Summary

SITE SUMMARY (continued)

The population factor evaluation is based on three factors: Level I concentrations, Level II concentrations, and 

potential contamination [Ref. 1, Section 6.3.2]. Level I concentrations are not scored. Level II concentrations are 

assigned to the actual contamination at each sampling location that meets the criteria for observed release of thoron

[Ref. 1, Section 2.5; 2, pp. 20-21]. The single most distant Level II sample location is located within the Greater 

than 0 to 1⁄4 mile distance category of the air migration pathway [Ref. 1, Section 6.3, Table 6-15; Figure 8]. The 

population located anywhere within this furthest Level II distance category is considered as subject to Level II 

concentrations [Ref. 1, Section 6.3]. B ased on these considerations, more than 6,800 residents, students, and 

workers within 1⁄4 mile of the source are considered as subject to Level II concentrations (see Section 6.3.2.3 of this 

HRS documentation record). In addition, there are more than 1.8 million residents within 4 miles of the source at 

the site [Ref. 21, pp. 1-4, 6, 14, 42, 88, 148, 154]. 

Since October 2012, EPA has conducted additional monitoring and mitigation activities at the WACC subject 

property and vicinity. Surveys conducted in October and November 2012 confirmed elevated radiation levels in 

some areas [Ref. 33, pp. 2-3]. In December 2012 and February 2013, radon and thoron monitoring in on-source 

buildings indicated a few elevated readings [Ref. 33, pp. 3-4]. EPA installed fencing at the site and began shielding 

portions of the radioactive soil with rock and clean fill in April 2013 to reduce accessibility of the waste material 

[Ref. 33, p. 4]. The source and exposures are not wholly contained, and EPA is continuing mitigation activities at 

the site [Ref. 33, pp. 2-5]. 
 

 

CLIENT NAME: DATE: FIGURE #: 

PROJECT: 

LEGEND: TITLE: 

Source 1 

0 1,000 2,000 4,000 

Graphic Scale In Feet 

1. National Geographic TOPO! U.S. Geologic Survey (USGS). 7.5 Minute 

Series (Topographic) Quadrangles: Brooklyn, NY 1995. 

2. Ref. 19, pp. 13-22; 27, pp. 1-3 

EPA 

Wolff-Alport Chemical Company Site 

July 2013 1 

Source Location Map 

Wolff-Alport Chemical Company Site 

Ridgewood, Queens County, NY 

P:\SAT2\Wolff_Alport_Chemical\MXD\2013_07_Report\13366_WAC_Site_Loc.mxd

SOURCES: 

Site Area 

"

NJ 

PA 

NY ®

Perimeter of Source 1 
Non-WACC

Commercial Buildings

WACC Storage

Buildings

WACC Yard Areas

 

CLIENT NAME: DATE: FIGURE #: 

PROJECT: 

SOURCES: TITLE: 

COOPER AVE 

COOPER ST 

IRVING AVE 

MOFFAT ST 

Non-WACC 

Commercial Buildings WACC 

Warehouse 

WACC Storage 

Buildings 

WACC Yard Areas 

WACC Kiln-Vat 

Building 

0 75 150 300

Graphic Scale In Feet 

1. 1954 Aerial; EDR Report, Inquiry 3364844.5. 

2. New York City Department of Finance. Digital Tax Map Online;

 http://gis.nyc.gov/taxmap/map.htm. 

3. Ref. 5, pp. 18, 39-42. 

EPA 

Wolff-Alport Chemical Company Site 

July 2013 2 

WACC Facility Layout, 1954 

Wolff-Alport Chemical Company Site 

Ridgewood, Queens County, NY 

P:\SAT2\Wolff_Alport_Chemical\MXD\2013_07_Report\13368_WAC_1954_Aerial.mxd 

®

Legend

Lot & Block Lines 

Approximate Extent of Contaminated Soil (NYCDDC, 2010) 
 

 

CLIENT NAME: DATE: FIGURE #: 

PROJECT: 

SCALE: TITLE: 

0 40 80 160

Graphic Scale In Feet 

EPA 

Wolff-Alport Chemical Company Site 

July 2013 3 

Geographic Representation of Soil Sample Analytical 

Results from NYCDDC Radiological Scoping Survey 

(August 2010) 

Wolff-Alport Chemical Company Site 

Ridgewood, Queens County, NY 

P:\SAT2\Wolff_Alport_Chemical\MXD\2013_07_Report\13367_WAC_DDC_Sample_results.mxd 

®

Legend

!( >55 pCi/g 

!( 5-55 pCi/g 

!( < 5 pCi/g 

!( NO DATA 

Lot & Block Lines 

Approximate Extent of Contaminated Soil (NYCDDC, 2010) 

Sources: 

1. Bing Maps - Aerial - Image courtesy of the IndianaMap

 © 2012 Microsoft Corporation © 2010 NAVTEQ © 

2. New York City Department of Finance. Digital Tax Map Online;

 http://gis.nyc.gov/taxmap/map.htm. 

3. Ref. 5, pp. 39-42; 12, p. 2 
 

 

CLIENT NAME: DATE: FIGURE #: 

PROJECT: 

SOURCES: TITLE: 

0 40 80 160

Graphic Scale In Feet 

EPA 

Wolff-Alport Chemical Company Site 

July 2013 4 

Survey Location Map - September 2012 

Wolff-Alport Chemical Company Site 

Ridgewood, Queens County, NY 

P:\SAT2\Wolff_Alport_Chemical\MXD\2013_07_Report\13369_WAC_09_2012_Sample_loc.mxd 

®

Legend

Pressurized Ion Chamber (PIC) Gamma Survey Point 

") RAD7 Thoron and Radon Gas Survey Point 

Lot & Block Lines 

Approximate Extent of Contaminated Soil (NYCDDC, 2010) 

1. Bing Maps - Aerial - Image courtesy of the IndianaMap

 © 2012 Microsoft Corporation © 2010 NAVTEQ © 

2. New York City Department of Finance. Digital Tax Map Online;

 http://gis.nyc.gov/taxmap/map.htm. 

3. Ref. 5, pp. 39-42; 12, p. 2; 19, pp. 13-26; 27, pp. 1-3. 
 

 

   

 

 

CLIENT NAME: DATE: FIGURE #: 

PROJECT: 

SCALE: TITLE: 

0 40 80 160

Graphic Scale In Feet 

1. Bing Maps - Aerial - Image courtesy of the IndianaMap

 © 2012 Microsoft Corporation © 2010 NAVTEQ © 

2. New York City Department of Finance. Digital Tax Map Online;

 http://gis.nyc.gov/taxmap/map.htm. 

3. Ref. 5, pp. 39-42; 12, p. 2; 19, pp. 13-26; 27, pp. 1-3. 

EPA 

Wolff-Alport Chemical Company Site 

July 2013 5 

Field Gamma Reading (cpm) 

Wolff-Alport Chemical Company Site 

Ridgewood, Queens County, NY 

P:\SAT2\Wolff_Alport_Chemical\MXD\2013_07_Report\13370_WAC_Field_Readings.mxd 

® Location ID

Field Gamma

Reading (cpm)

WAC‐BKG‐01 7307

WAC‐BKG‐02 7723

WAC‐BKG‐03 7213

WAC‐BKG‐04 11579

WAC‐BKG‐05 7704

WAC‐BKG‐06 7949

WAC‐BKG‐07 9513

WAC‐SPUR‐01 145524

WAC‐PER‐01 13607

WAC‐PER‐02 25615

WAC‐PER‐03 15919

WAC‐PER‐04 24289

WAC‐PER‐05 16814

WAC‐PER‐06 36965

WAC‐PER‐07 15155

WAC‐PER‐08 22012

WAC‐PER‐09 22625

WAC‐PER‐10 15742

WAC‐PER‐11 21622

WAC‐PER‐12 23450

WAC‐PER‐13 13341

WAC‐SPUR‐02 147135

WAC‐PER‐14 22090

WAC‐PER‐15 46397

WAC‐PER‐16 18126

WAC‐PER‐17 26291

WAC‐PER‐18 33171

WAC‐PER‐19 15262

WAC‐IRV‐20 12159

WAC‐IRV‐21 19866

WAC‐IRV‐22 15223

WAC‐IRV‐23 22989

WAC‐IRV‐24 14484

WAC‐IRV‐25 39322

WAC‐IRV‐26 20768

WAC‐IRV‐27 24608

WAC‐IRV‐28 14108

WAC‐IRV‐29 15972

WAC‐IRV‐30 27293

WAC‐IRV‐31 38382

WAC‐IRV‐32 23960

WAC‐IRV‐33 15106

WAC‐IRV‐34 36966

WAC‐IRV‐01 19794

WAC‐IRV‐02 65943

WAC‐IRV‐03 40336

WAC‐IRV‐04 27228

WAC‐IRV‐05 22360

WAC‐IRV‐06 15595

WAC‐IRV‐07 19487

WAC‐IRV‐08 9067

WAC‐MOF‐01 18145

WAC‐MOF‐02 35783

WAC‐MOF‐03 25565

WAC‐MOF‐04 33719

WAC‐MOF‐05 26435

WAC‐MOF‐06 49775

WAC‐MOF‐07 38888

WAC‐MOF‐08 19855

WAC‐MOF‐09 19312

WAC‐MOF‐10 15132

WAC‐MOF‐11 13312

WAC‐IRV‐10 437849

WAC‐COP‐01 8827

WAC‐COP‐02 8366

WAC‐COP‐03 11248

WAC‐COP‐04 8554

WAC‐MOF‐12 16006

WAC‐MOF‐13 24764

WAC‐MOF‐14 17159

Legend

Pressurized Ion Chamber (PIC) Gamma Survey Point 

") RAD7 Thoron and Radon Gas Survey Point 

Lot & Block Lines 

Approximate Extent of Contaminated Soil (NYCDDC, 2010) 

Note: 

1. cpm = counts per minute, as measured with Ludlum 

2221/44-10 NaI scintillation detector. 
DATE: FIGURE #:

CLIENT NAME:

PROJECT:

SOURCES: TITLE:

EPA

Wolff-Alport Chemical Company Site

July 2013 6

Gamma Radiation Exposure Rate (μR/hr)

Wolff-Alport Chemical Company Site

Ridgewood, Queens County, NY

P:\SAT2\Wolff_Alport_Chemical\MXD\2013_07_Report\13371_WAC_Gamma_Exposure.mxd

® Location ID

Gamma Radiation

Exposure Rate

(μR/hr)

WAC‐BKG‐01 8.7

WAC‐BKG‐02 9.5

WAC‐BKG‐03 8.4

WAC‐BKG‐04 11.4

WAC‐BKG‐05 9.3

WAC‐BKG‐06 9.1

WAC‐BKG‐07 9.8

WAC‐SPUR‐01 114.5

WAC‐PER‐01 12.3

WAC‐PER‐02 21.8

WAC‐PER‐03 14.8

WAC‐PER‐04 18.3

WAC‐PER‐05 14.3

WAC‐PER‐06 26.7

WAC‐PER‐07 13.7

WAC‐PER‐08 20.3

WAC‐PER‐09 19.8

WAC‐PER‐10 13.9

WAC‐PER‐11 19.2

WAC‐PER‐12 19.8

WAC‐PER‐13 12.9

WAC‐SPUR‐02 119.9

WAC‐PER‐14 18.9

WAC‐PER‐15 33.4

WAC‐PER‐16 16.8

WAC‐PER‐17 22.9

WAC‐PER‐18 25.9

WAC‐PER‐19 14.1

WAC‐IRV‐20 11.3

WAC‐IRV‐21 16.7

WAC‐IRV‐22 12.5

WAC‐IRV‐23 19.8

WAC‐IRV‐24 12

WAC‐IRV‐25 23.9

WAC‐IRV‐26 15.9

WAC‐IRV‐27 17.7

WAC‐IRV‐28 13.1

WAC‐IRV‐29 13.9

WAC‐IRV‐30 22.5

WAC‐IRV‐31 28.4

WAC‐IRV‐32 17.1

WAC‐IRV‐33 12.3

WAC‐IRV‐34 24.2

WAC‐IRV‐01 18.5

WAC‐IRV‐02 49.5

WAC‐IRV‐03 33.7

WAC‐IRV‐04 25

WAC‐IRV‐05 19.1

WAC‐IRV‐06 14.6

WAC‐IRV‐07 16.3

WAC‐IRV‐08 10

WAC‐MOF‐01 15.7

WAC‐MOF‐02 30.9

WAC‐MOF‐03 23.8

WAC‐MOF‐04 28.3

WAC‐MOF‐05 22.3

WAC‐MOF‐06 42.2

WAC‐MOF‐07 29.8

WAC‐MOF‐08 19

WAC‐MOF‐09 17.7

WAC‐MOF‐10 14.6

WAC‐MOF‐11 13

WAC‐IRV‐10 2166.3

WAC‐COP‐01 10

WAC‐COP‐02 9.4

WAC‐COP‐03 11.4

WAC‐COP‐04 9.7

WAC‐MOF‐12 15.1

WAC‐MOF‐13 19

WAC‐MOF‐14 16.3

Legend

 Pressurized Ion Chamber (PIC) Gamma Survey Point

Background Sample Location

Sample Location with Result < 2x Background

Sample Location with Result > 2x Background

") RAD7 Thoron and Radon Gas Survey Point

Lot & Block Lines

Perimeter of Source 1 

(Based on Gamma Exposure Rates, September 2012)

Other Possible Source Area 

(Based on Gamma Exposure Rates, September 2012)

1. Bing Maps - Aerial - Image courtesy of the IndianaMap 

 © 2012 Microsoft Corporation © 2010 NAVTEQ ©

2. New York City Department of Finance. Digital Tax Map Online;

 http://gis.nyc.gov/taxmap/map.htm.

3. Ref. 12, p. 2; 19, pp. 13-22; 27, pp. 1-3.

Note: 

1. μR/hr = microRoentgens per hour, as measured with 

 Reuter-Stokes RSS-131 pressurized ion chamber.

0 40 80 160

Graphic Scale In Feet
   

   

   

   

   

   

   

   

   

   

   

   

   

   

   

   

   

   

   

 

 

 

 

 

CLIENT NAME: DATE: FIGURE #: 

PROJECT: 

SOURCES: TITLE: 

0 40 80 160

Graphic Scale In Feet 

EPA 

Wolff-Alport Chemical Company Site 

July 2013 7 

Thoron Concentrations (pCi/L) 

Wolff-Alport Chemical Company Site 

Ridgewood, Queens County, NY 

P:\SAT2\Wolff_Alport_Chemical\MXD\2013_07_Report\13372_WAC_Thoron_Samples.mxd 

Field ID ® Thoron w/Uncertainty

(pCi/L)

WAC‐BKG‐01 0.00 ± 0.56

WAC‐BKG‐04 0.33 ± 0.90

WAC‐BKG‐05 0.00 ± 0.56

WAC‐BKG‐05A 0.00 ± 0.66

WAC‐BKG‐06 0.17 ± 0.80

WAC‐IRV‐10 0.33 ± 0.90

WAC‐IRV‐31 1.12 ± 1.12

WAC‐PER‐01 2.98 ± 1.77

WAC‐PER‐05 3.94 ± 1.80

WAC‐PER‐07 2.15 ± 1.57

WAC‐PER‐13 3.80 ± 1.77

WAC‐PER‐16 10.3 ± 2.71

WAC‐PER‐18 8.61 ± 2.74

WAC‐PER‐19 2.48 ± 1.65

WAC‐SPUR‐01 61.8 ± 6.19

WAC‐SPUR‐02 366 ± 16.1

WAC‐SPUR‐02‐A 301 ± 13.5

WAC‐SPUR‐02‐ELEV 6.19 ± 2.17

Legend

") RAD7 Thoron and Radon Gas Survey Point 

Lot & Block Lines 

Perimeter of Source 1 

(Based on Gamma Exposure Rates, September 2012) 

Other Possible Source Area 

(Based on Gamma Exposure Rates, September 2012) 

1. Bing Maps - Aerial - Image courtesy of the IndianaMap

 © 2012 Microsoft Corporation © 2010 NAVTEQ © 

2. New York City Department of Finance. Digital Tax Map Online;

 http://gis.nyc.gov/taxmap/map.htm. 

3. Ref. 5, pp. 39-42; 12, p. 2; 19, pp. 13-26; 27, pp. 1-3. 

Note: 

1. pCi/L = picocuries per liter, as measured with RAD7 

Radon Detector. 
 

 

 

 

 

CLIENT NAME: DATE: FIGURE #: 

PROJECT: 

LEGEND: TITLE: 

Source 1 1/4 Mile 

0 250 500 1,000 

Graphic Scale In Feet 

SOURCES: 

1. National Geographic TOPO! U.S. Geologic Survey (USGS). 7.5 Minute

 Series (Topographic) Quadrangles: Brooklyn, NY 1995. 

2. U.S. Department of Commerce, U.S. Census Bureau, Geography Division. 

TIGER/Line Shapefile, 2010, 2010 state, New York, 2010 Census Block 

State-based. http://www.census.gov/geo/www/tiger. Downloaded March 2013. 

3. Ref. 19, pp. 13-22; 21, pp. 1, 154; 27, pp. 1-3. 

EPA 

Wolff-Alport Chemical Company Site 

July 2013 8 

Quarter-Mile Radius Map 

Wolff-Alport Chemical Company Site 

Ridgewood, Queens County, NY 

P:\SAT2\Wolff_Alport_Chemical\MXD\2013_07_Report\13373_WAC_quarter_mile.mxd 

®

Perimeter of Source 1 

2010 Census Blocks 
18

SD-Characterization and Containment

Source No.: 1

SOURCE DESCRIPTION

2.2 SOURCE CHARACTERIZATION

Number of the source: 1 

Source Type of the source: Contaminated Soil

Name and description of the source: Residual Waste Materials

Source 1 is soil contaminated with residual waste materials left behind by facility operations, as identified in the 

results of the 2009-2010 NYCDDC investigation. During the NYCDDC investigation, soil borings, samples, and 

downhole gamma logging were used to identify residual waste materials and soil contamination at the subject 

property [Ref. 5, pp. 6-9]. Waste tailings consisting of black or gray ash-like material were found in a contaminated 

soil layer beneath subject property buildings, beneath sidewalks and asphalt surfaces of Irving Avenue and Moffat 

Street, and within the surface soils of the former rail spur [Ref. 5, pp. 43, 56]. The depth of contaminated soil at the 

subject property is typically within the top 1 to 4 feet under the pavement or ground surface, and a lens was reported 

at 8 to 10 feet beneath the auto body shop [Ref. 5, p. 43]. 

During the 2009-2010 NYCDDC investigation, fourteen subsurface samples were collected under the buildings, 

while 21 surface samples and 14 subsurface samples were collected from exterior areas [Ref. 5, pp. 38-40, 213, 216-

217, 220, 287]. The soil samples were analyzed using HPGe (high purity germanium) gamma spectroscopy at 

CoPhysics Corporation, and the 911 kilo-electron volt (keV) gamma ray line from Actinium-228 was used for 

thorium-232 determination [Ref. 5, pp. 53, 81-84; 31, pp. 10-11, 25-26]. The method used by the laboratory is

equivalent to EPA-approved Method GA-01-R,”Gamma Radioassay” from the DOE HASL-300 Manual dated 1997

[Ref. 5, p. 53; 31, pp. 10-22]. The results were reported in units of pCi/g wet weight (in situ concentration), and 

each analytical result was presented with an associated uncertainty level that represented one standard deviation 

[Ref. 5, pp. 45-46, 53, 81-84]. Detection limits and quantitation limits were not presented with the sample analytical 

results [Ref. 5, pp. 45-46, 81-84]. Quality controls included duplicate, blank, and reference samples [Ref. 5, pp. 53-

54]. The deionized water blank used for quality control showed a thorium-232 result of 0.03 ± 0.01 pCi/g, and the 

reference sample results were below the expected results, possibly indicating low bias for the associated field sample 

results [Ref. 5, pp. 53-54].

Thorium-232 activity concentrations up to 1,133 pCi/g were reported for the soil samples collected from the subject 

property, including a concentration of 477 pCi/g in the deeper lens [Ref. 5, pp. 39-42, 45-46, 81-84]. Site-specific 

background samples were not collected during the investigation [Ref. 5, p. 287]. Based on work at other radiation 

sites in the region, the range of thorium background concentrations in northeastern soil was reported to be 0.5 pCi/g 

to 1.0 pCi/g and the higher value was assumed as the site background level [Ref. 5, pp. 41, 287]. NYCDDC used a 

guideline of 5 pCi/g above this background level to depict contaminated areas at the WACC site, based on EPA’s 

prior use of that guideline as a cleanup level at Superfund sites [Ref. 5, pp. 24-25, 42]. The soil sampling results

from the NYCDDC investigation are presented below in Table 1, and the approximate extent of contamination 

based on these results is depicted in Figure 3. 
19

SD-Characterization and Containment

Source No.: 1

TABLE 1. SOIL SAMPLE RESULTS

Location Depth 

(ft bgs)

Date Lab ID Wet Mass 

(g)

Dry Mass (g) Throrium-232

(pCi/g)*

Reference

A1A 0.5-1.5 12/16/09 725-06 136.1 82.4 21.2 ± 1.1 5, pp. 38-46, 

A2A 8.5 53-54, 81-84 -9 12/16/09 725-04 142.0 123.2 476.9 ± 28.2

A2B 0.5-1 12/16/09 725-01 121.2 101.2 1,133.4 ± 68.4

A3A 0.5-1.5 12/16/09 725-03 169.9 128.8 202.3 ± 11.8

A3B 0.5-1.5 12/16/09 725-05 361.9 329.8 424.7 ± 22.1

A3C 0.5-1.0 12/13/09 725-13 188.9 163.3 73.4 ± 3.9

A4A 0.5-1.5 12/16/09 725-02 281.8 251.2 169.6 ± 9.7

A5A 1-1.5 12/13/09 725-08 323.2 279.4 44.6 ± 2.4

A5B 0.5-1.5 12/16/09 725-11 191.1 170.8 77.4 ± 4.2

A6A 0.5-1.0 12/16/09 725-12 196.7 181.4 13.2 ± 0.8

A6B 0.5-1.5 12/12/09 725-10 410.2 375.6 45.2 ± 2.5

A6C 0.5-1.5 12/12/09 725-07 298.0 275.4 75.9 ± 4.1

B1B 0-0.5 11/12/09 716-05 268.7 250.9 10.4 ± 0.6

B1D 2"-1' 12/12/09 725-16 190.0 184.8 15.2 ± 0.9

B1S2 surface 12/16/09 725-40 422.0 356.5 13.7 ± 0.7

B2A 0-1 12/13/09 725-15 311.3 275.1 28.8 ± 1.5

B2B 0-1 12/12/09 725-17 373.3 312.4 99.5 ± 5.2

B2E 2-2.5 12/12/09 725-20 314.1 268.7 207.8 ± 10.5

B2F 0-0.5 12/12/09 725-19 302.6 255.7 20.7 ± 1.1

B2S10 surface 12/16/09 725-31 293.1 272.0 10.9 ± 0.7

B2S14 surface 12/16/09 725-35 350.8 294.4 8.2 ± 0.5

B2S2 surface 12/16/09 725-23 196.7 125.1 471.8 ± 24.1

B2S3 surface 12/16/09 725-24 202.7 148.3 9.7 ± 0.6

B2S4 surface 12/16/09 725-25 296.1 249.3 25.3 ± 1.3

B2S5 surface 12/16/09 725-26 263.1 198.6 17.9 ± 0.9

B2S6 surface 12/16/09 725-27 257.5 201.5 12 ± 0.7

B2S7 surface 12/16/09 725-28 229.7 172.5 18.3 ± 1

B2S8 surface 12/16/09 725-29 296.3 224.2 17 ± 0.9

B2S9 surface 12/16/09 725-30 283.4 216.7 12.1 ± 0.7

B3B 0-1 11/12/09 716-02 335.3 314.4 143.7 ± 7.2

B3C 0-1 11/12/09 716-03 323.4 302..2 40.6 ± 2.1

B3D 0-0.5 11/12/09 716-07 457.1 416.1 10.2 ± 0.6

B3S1 surface 12/16/09 725-38 531.4 467.7 13.7 ± 0.8

B3S2 surface 12/16/09 725-39 467.9 418.6 7.8 ± 0.4

M-2 0.5 07/24/09 692-1 291.1 273.0 38.2 ± 2.2

pCi/g = Picocuries per gram

* The detection limits and quantitation limits were not presented in the available report or its attachments [Ref. 5, 

pp. 45-46, 81-84, 286-287]. 
20

SD-Characterization and Containment

Source No.: 1

During the NYCDDC investigation, gamma radiation levels above the background range of 6 μR/hr to 10 μR/hr

were recorded throughout most of the subject property [Ref. 5, pp. 34-37]. Interior gamma measurements above 

background were recorded in the auto body shop (formerly the WACC kiln-vat operations building and adjoining 

yard), warehouses (formerly a WACC operations building and adjoining yard), and deli basement, with the highest 

reading (500 μR/hr) in the auto body shop [Ref. 5, pp. 28, 36-37, 63]. The highest exterior gamma measurement 

was recorded near the curb in front of the auto body shop [Ref. 5, pp. 28, 34-35]. Downhole gamma logging also 

indicated the presence of contamination to depths up to 20 feet beneath the auto body shop, and acidic odors were 

reported within those deeper borings; however, waste tailings are absent at these depths and this deeper 

contamination is believed to stem from solubilized thorium that leached down through the pre-existing sandy soil 

[Ref. 5, pp. 43-47].

In September 2012, EPA used a Reuter-Stokes RSS-131 Pressurized Ion Chamber (PIC) to collect gamma radiation 

exposure rate measurements at hot spots within the source area, around the perimeter of Source 1, and at background 

locations [Ref. 19, pp. 5-22; 20, pp. 3-7, 20; 23, pp. 1-2]. Concurrently, EPA measured a one-minute gamma count 

rate at each location with a Ludlum Model 2221/44-10, 2-inch by 2-inch, sodium iodide (2x2 NaI) scintillation 

detector that was configured to mimic the response of the PIC [Ref. 19, pp. 5-22; 20, pp. 3-4]. The PIC and 

scintillation detector systems collected data at a height of one meter above the ground surface [Ref. 20, p. 3]. The 

measurement locations are shown in Figure 4. 

The primary objective of the EPA gamma survey was to delineate the source area by mapping the boundary line 

where gamma radiation exposure rates equal two times the site-specific background gamma radiation exposure rate

[Ref. 20, pp. 3-4; 28, pp. 11-12]. The PIC produces accurate results, measuring true gamma radiation exposure rate 

in μR/hr with an accuracy of ± 5% [Ref. 20, pp. 3, 5; 23, pp. 1-2]. The EPA-owned PIC used at the WACC site 

(serial number 99I08941) had been calibrated by an accredited instrument calibration laboratory in April 2012 [Ref. 

20, pp. 4, 34-41]. The PIC was deployed at each of 70 measurement locations for a minimum of five minutes to 

allow the instrument response to stabilize; data were collected at one-second intervals and stored in the instrument’s 

internal memory for subsequent downloading and review by a Certified Health Physicist (CHP) [Ref. 20, p. 5]. EPA 

read the concurrent gamma count rates directly from the scintillation detector and recorded the readings on field data 

sheets [Ref. 19, pp. 13-22]. The CHP interpreted the one-second PIC data and calculated a one-minute average of 

the gamma radiation exposure rate at each location [Ref. 20, p. 5]. 

From the set of seven possible background locations, the CHP interpreted the measurement at location WAC-BKG04, located along Cooper Avenue at the northwest end of the former rail spur, to have some possible impact from the 

site [Ref. 20, pp. 6, 16, 20]. The CHP selected the six other data points (all collected further from Source 1) as being 

representative of the true, non-impacted gamma radiation exposure rate, and calculated the mean site-specific 

background gamma radiation exposure rate to be 9.1 μR/hr [Ref. 19, p. 13; 20, p. 6]. The source area is delineated 

by gamma radiation exposure rates that equal or exceed two times the site-specific background gamma radiation 

exposure rate (i.e., 18.2 μR/hr), as shown in Figure 6 [Ref. 19, pp. 5-22; 20, pp. 3-7, 20, 24-31]. This delineated 

extent of the source area has a close correlation to the area of contamination delineated by previous soil sample 

analytical results (see Figures 3 and 6). The gamma radiation exposure rates for measurement locations within the 

source area are presented below in Table 2 [Ref. 19, pp. 13-22; 20, pp. 30-31]. Locations that did not equal or 

exceed two times the site-specific background gamma radiation exposure rate are considered to be outside the 

boundary of the source.
21

SD-Characterization and Containment

Source No.: 1

TABLE 2. GAMMA RADIATION EXPOSURE RATES – SOURCE 1

Location ID Date Time

1-Min Interval 

for PIC 

Measurement

Gamma Radiation Exposure Rate References

PIC (μR/hr)* Scintillator (cpm)

WAC-IRV-01 9/19/2012 16:27-16:32 16:30 18.5 19,794 Ref. 19, pp. 

13-22, 36-

51; 20, pp. 

5-7, 24-31; 

Figures 5 

and 6 of 

this HRS 

doc. record

WAC-IRV-02 9/19/2012 16:05-16:26 16:15 49.5 65,943

WAC-IRV-03 9/19/2012 16:32-16:38 16:36 33.7 40,336

WAC-IRV-04 9/19/2012 16:39-16:45 16:43 25.0 27,228

WAC-IRV-05 9/19/2012 16:45-16:50 16:48 19.1 22,360

WAC-IRV-10 9/19/2012 18:21-18:27 18:25 2,166.3 437,849

WAC-SPUR-01 9/20/2012 9:20-9:27 9:24 114.5 145,524

WAC-PER-02 9/20/2012 9:38-9:44 9:41 21.8 25,615

WAC-PER-04 9/20/2012 9:51-9:56 9:53 18.3 24,289

WAC-PER-06 9/20/2012 10:03-10:08 10:06 26.7 36,965

WAC-PER-08 9/20/2012 10:16-10:25 10:21 20.3 22,012

WAC-PER-09 9/20/2012 10:30-10:56 10:40 19.8 22,625

WAC-PER-11 9/20/2012 11:07-11:13 11:11 19.2 21,622

WAC-PER-12 9/20/2012 11:15-11:20 11:18 19.8 23,450

WAC-SPUR-02 9/20/2012 11:35-11:48 11:43 119.9 147,135

WAC-PER-14 9/21/2012 9:25-9:32 9:27 18.9 22,090

WAC-PER-15 9/21/2012 9:33-9:39 9:36 33.4 46,397

WAC-PER-17 9/21/2012 9:53-10:01 9:56 22.9 26,291

WAC-PER-18 9/21/2012 10:01-10:06 10:04 25.9 33,171

WAC-IRV-23 9/20/2012 13:38-13:50 13:42 19.8 22,989

WAC-IRV-25 9/20/2012 14:15-14:21 14:18 23.9 39,322

WAC-IRV-30 9/20/2012 14:55-15:00 14:57 22.5 27,293

WAC-IRV-31 9/20/2012 15:00-15:05 15:03 28.4 38,382

WAC-IRV-34 9/20/2012 15:18-15:23 15:21 24.2 36,966

μR/hr = Microroentgens per hour

cpm = Counts per minute

* The PIC measures gamma radiation within the range of 0 to 10 Roentgens per hour (R/hr) and the zero reading is 

accurate within ± 0.5 μR/hr [Ref. 23, p. 2]. Therefore, the detection limit of the instrument as used in the field for 

each measurement is 0.5 μR/hr [Ref. 1, Section 1.1].
22

SD-Characterization and Containment

Source No.: 1

Location of the source, with reference to a map of the site:

Soil contaminated with residual waste materials are present beneath most of the subject property building footprints, 

beneath sidewalks and asphalt surfaces of Irving Avenue and Moffat Street, and at the ground surface throughout the 

rail spur [Ref. 5, pp. 38-47; 20, pp. 4-7, 20]. The perimeter of Source 1 is shown in Figure 6. 

Containment

Release via air pathway:

HRS requires separate evaluation of gas and particulate containment for each source at the site. Gas containment is 

evaluated for sources that contain gaseous hazardous substances (vapor pressure ≥ 10-9 Torr) and particulate 

containment is evaluated for sources that contain particulate hazardous substances (vapor pressure ≤ 10-1 Torr) [Ref. 

1, Section 6.1.2]. Source 1 contains thorium-232 and by nature all of its radioactive progeny, including thoron, in 

secular equilibrium [Ref. 22, pp. 1, 4]. Thoron, being an isotope of the radioactive element radon, has a vapor 

pressure of 760 Torr [Ref. 2, pp. 20-21, 24]. Thorium-232 is a particulate hazardous substance [Ref. 2, pp. 9, 13]. 

Therefore, Source 1 contains both gaseous and particulate hazardous substances and is evaluated for gas 

containment using HRS Table 6-3 and particulate containment using HRS Table 6-9.

The results of the NYCDDC investigation show that the contaminated soil at the source is at depths within 1 foot of 

the ground surface in the former rail spur, where there are some exposed soil areas [Ref. 5, pp. 8, 41-47]. This 

situation is listed in HRS Tables 6-3 and 6-9 as “Uncontaminated soil cover < 1 foot: Other.” B ased on the 

containment descriptions, Source 1 is assigned a gas containment factor value of 10 and a particulate containment 

factor value of 10 in the air migration pathway [Ref. 1, Section 6.1.2, Tables 6-3 and 6-9].
23

SD-Hazardous Substances

Source No.: 1 

2.4.1 Hazardous Substances

Residual waste materials containing thorium were abandoned at the subject property, and the results of the 

NYCDDC investigation showed that Source 1 contains elevated levels of thorium-232 (see Section 2.2, Table 1 of 

this HRS documentation record). The radioactive decay series for thorium-232 includes several radionuclides, 

including thoron, that are approximately in a state of secular equilibrium (i.e., the activities of all radionuclides 

within the series are nearly equal) [Ref. 22, p. 1]. Therefore, all are considered to be present within the source 

material. 

The decay series for Thorium-232 proceeds as follows (with half-lives in parentheses) [Ref. 22, pp. 1, 4] 

• Thorium-232 (14 billion years)

• Radium-228 (5.8 years)

• Actinium-228 (6.1 hours)

• Thorium-228 (1.9 years)

• Radium-224 (3.7 days)

• Radon-220 aka Thoron (56 seconds)

• Polonium-216 (0.15 second)

• Lead-212 (11 hours)

• Bismuth-212 (61 minutes)

• Polonium-212 (310 nanoseconds) and Thallium-208 (3.1 minutes)

• Lead-208 (stable).

One of the key components of the thorium-232 decay series is thoron, which emanates from surfaces where thorium232 is present [Ref. 18, p. 1]. A hazard associated with airborne thoron comes from its radioactive decay products, a 

large fraction of which remain suspended in the air, where they can be inhaled and deposited in the lungs; the 

primary health hazard is lung cancer due to alpha particle radiations from these decay products after they have been 

deposited on the bronchial epithelium of the lung [Ref. 18, p. 3]. 
24

SD-Hazardous Waste Quantity

Source No.: 1 

7.2.5 Hazardous Waste Quantity

Source 1 contains radioactive substances and, therefore, it is evaluated for radionuclide constituent quantity (Tier A)

and radionuclide wastestream quantity (Tier B) in accordance with HRS Section 7.2.5 and its subsections.

7.2.5.1.1 Radionuclide Constituent Quantity (Tier A)

The historical documentation and sampling data are insufficient to determine with confidence either the activity 

concentration above background for the radionuclides in Source 1 or the volume of the source itself. Therefore, the 

net activity content in the source cannot be estimated in curies or converted to equivalent pounds of nonradioactive 

hazardous substances [Ref. 1, Section 7.2.5.1.1]. Source 1 is known to contain radioactive substances with activity 

concentrations above background [Ref. 5, pp. 45-47; 20, pp. 4-10, 30-33], so radionuclide constituent quantity (Tier 

A) is assigned a value of unknown but greater than 0 equivalent pounds. 

Radionuclide Constituent Quantity (Tier A) Assigned Value: unknown but >0 

Since the radionuclide constituent quantity is not adequately determined, radionuclide wastestream quantity (Tier B) 

is evaluated [Ref. 1, Section 7.2.5.1.1].

7.2.5.1.2 Radionuclide Wastestream Quantity (Tier B)

Although Source 1 is known to contain radioactive substances, the historical documentation and sampling data are 

insufficient to estimate the total volume of wastestreams containing radionuclides allocated to the source. 

Therefore, the activity content of radionuclide wastestreams allocated to the source expressed in terms of equivalent 

pounds of nonradioactive hazardous substances, and radionuclide wastestream quantity (Tier B) is assigned a value 

of unknown but greater than 0 equivalent pounds [Ref. 1, Section 7.2.5.1.2]. 

Radionuclide Wastestream Quantity (Tier B) Assigned Value: unknown but >0

7.2.5.1.3 Source Hazardous Waste Quantity Value for Radionuclides

The source hazardous waste quantity value for Source 1 is unknown but >0 for radionuclide wastestream quantity

(Tier B) [Ref. 1, Section 7.2.5.1.3].

Source Hazardous Waste Quantity Value: unknown but >0
25

SD-Summary

SITE SUMMARY OF SOURCE DESCRIPTIONS

 

TABLE 3. HAZARDOUS WASTE QUANTITY AND CONTAINMENT

Source Number Source Hazardous 

Waste Quantity Value

Containment

Ground Water Surface Water Air

Gas Particulate

1 >0 NS NS 10 10

NS = Not Scored

Other Possible Sources

Moffat Street: 

During the 2009-2010 NYCDDC investigation, gamma radiation levels above the background range (6-10 μR/hr)

were recorded along Moffat Street south of the former WACC facility [Ref. 5, pp. 34-35]. Based on these surface 

gamma readings, the impact to Moffat Street appeared to extend as much as 300 feet from Irving Avenue [Ref. 5, 

pp. 34-35]. During the September 2012 investigation, EPA identified an area along the same portion of Moffat 

Street where gamma radiation exposure rates equal or exceed two times the site-specific background gamma 

radiation exposure rate as summarized in Table 4 [Ref. 19, pp. 5-16, 22; 20, pp. 4-7, 20, 30-31]. As shown in 

Figure 6, the area is separated from Source 1 by measurement locations that did not exceed two times the sitespecific background gamma radiation exposure rate [Ref. 20, pp. 20, 30-31]. 

TABLE 4. GAMMA RADIATION EXPOSURE RATES – MOFFAT STREET

Location ID Date Time

1-Min Interval 

for PIC 

Measurement

Gamma Radiation Exposure Rate References

PIC (μR/hr)* Scintillator (cpm)

WAC-MOF-02 9/19/2012 17:21-17:26 17:24 30.9 35,783 Ref. 19, pp. 

13-22, 36-

51; 20, pp. 

5-7, 24-31; 

Figures 5 

and 6 of 

this HRS 

doc. record

WAC-MOF-03 9/19/2012 17:26-17:32 17:29 23.8 25,565

WAC-MOF-04 9/19/2012 17:32-17:37 17:35 28.3 33,719

WAC-MOF-05 9/19/2012 17:37-17:42 17:40 22.3 26,435

WAC-MOF-06 9/19/2012 17:42-17:47 17:45 42.2 49,775

WAC-MOF-07 9/19/2012 17:48-17:55 17:52 29.8 38,888

WAC-MOF-08 9/19/2012 17:55-18:00 17:57 19.0 19,855

WAC-MOF-13 9/21/2012 11:45-11:50 11:48 19.0 24,764

μR/hr = Microroentgens per hour

cpm = Counts per minute

* The PIC measures gamma radiation within the range of 0 to 10 R/hr and the zero reading is accurate within ± 0.5 

μR/hr [Ref. 23, p. 2]. Therefore, the detection limit of the instrument as used in the field for each measurement is 

0.5 μR/hr [Ref. 1, Section 1.1].

Sewer disposal:

WACC disposed of its thorium-rich process liquors in the sewer until 1947, when the AEC ordered WACC to halt 

sewer disposal of thorium waste [Ref. 6, p. 8; 7, p. 5]. Investigations conducted in 2007 and 2009 suggest that 

residual contamination still exists in the sewer lines downstream of the facility [Ref. 5, pp. 30-34, 45]. 

 
26

Air-Observed Release

6.1 LIKELIHOOD OF RELEASE

6.1.1 Observed Release

Real-time thoron gas concentration measurements collected by EPA in September 2012 form the basis for observed 

release. At selected locations in background areas, above the source material, and outside the source area, thoron 

(radon-220) gas concentration measurements in pCi/L were collected with RAD7 Radon Detectors [Ref. 19, pp. 5-

12, 23-29]. Thoron is a radioactive gas that is part of the decay chain for the thorium-232 in the waste material at 

the WACC subject property; the half-life of thoron is 56 seconds [Ref. 22, pp. 1, 4]. Each thoron measurement 

location coincided with a gamma radiation exposure rate measurement location to identify its relative location with 

respect to the source boundary, as shown in Figures 4 and 7. Based on the results of the investigation, the thoron 

concentrations indicate that this hazardous gas is emanating from Source 1 and entering the ambient air above and 

outside the delineated source area.

Direct Observation

Observed release by direct observation is not scored. 

Chemical Analysis

EPA rented two RAD7 Radon Detectors, serial numbers 2813 and 3076, from the instrument manufacturer, 

Durridge Company, Inc., for use at the WACC subject property [Ref. 20, p. 8; 24, pp. 1, 8]. The instruments were 

pre-calibrated for thoron by the manufacturer, as shown on the calibration certificates [Ref. 20, pp. 8, 43-46; 25, p. 

4; 26, pp. 1-7]. EPA used the RAD7 meters to collect thoron concentration measurements at 15 selected locations in 

background areas, above the source material, and outside the source area [Ref. 19, pp. 5-12; 20, p. 16]. Based on the 

manufacturer’s recommendation, EPA used a shortened tube length (1’) and small drying tubes to capture maximum 

thoron readings, and the pump was running continuously in SNIFF mode [Ref. 19, pp. 5-12; 20, pp. 8-9]. The 

measurements were collected at heights of 1.5 to 6 inches above the ground surface, except that WAC-SPUR-02-

ELEV was collected at a height of 38 inches above the ground surface within the source area [Ref. 19, pp. 23-26; 20, 

pp. 8-9]. For each location, the field team operated the RAD7 meter for a 15-minute test purge followed by a 1-hour 

test [Ref. 19, pp. 23-26; 20, pp. 8-9]. Upon completion of each test, the thoron results were printed directly from the 

RAD7 meter [Ref. 19, pp. 27-29; 20, p. 9]. Each printout included results for thoron in pCi/L, as well as date/time, 

temperature (°C), relative humidity (%), and battery voltage [Ref. 19, pp. 27-29; 20, p. 9]. Duplicate measurements 

were collected at locations WAC-BKG-05 and WAC-SPUR-02, where both meters were deployed simultaneously

[Ref. 19, pp. 6-8, 23-24]. 

The thoron concentrations for each measurement location are presented in Tables 5 and 6 below, and the thoron 

concentration measurements are also shown in Figure 7. Each thoron measurement included a standard deviation 

value calculated and reported by the RAD7 meters, reflecting the two-sigma level of uncertainty associated with the 

reported concentration [Ref. 19, pp. 27-29; 20, p. 33; 25, p. 4]. These result-specific uncertainty levels are 

considered in evaluating background and contaminated sample concentrations [Ref. 25, pp. 1-3].

The background and contaminated samples are considered to be similar and therefore comparable for observed 

release determination. The background and contaminated samples were all collected during the same time period, 

September 19-21, 2012 (in some cases, concurrently); at similar physical locations (above exposed soil areas); and 

under similar weather conditions (clear with light [< 5 miles per hour], variable winds) [Ref. 19, pp. 6-12, 23-29; 20, 

pp. 8-9]. Based on gamma readings and position with respect to the source (the extent of which is known), the CHP 

interpreted the background sample locations (WAC-BKG-01, WAC-BKG-05, and WAC-BKG-06) as representative 

of true, non-impacted locations [Ref. 20, pp. 6, 9]. Duplicate measurements were collected at location WAC-BKG05, where both RAD7 meters were deployed simultaneously [Ref. 19, pp. 6, 23-24]. The sample locations are 

shown in Figure 7. 
27

Air-Observed Release

Background Concentrations

TABLE 5. BACKGROUND CONCENTRATIONS

Sample ID Date Time Height Hazardous 

Substance

Concentration

(pCi/L)

Uncertainty 

(pCi/L)

Projected 

Maximum (pCi/L)

Lower Limit of

Detection (pCi/L)

Location

WAC-BKG-01 9/19/12 1515 6 in. Thoron 0.00 0.56 0.56 0.4 60’ west of 

Source 1

WAC-BKG-05 9/19/12 1641 6 in. Thoron 0.00 0.66 0.66 0.4 180’ NE of 

WAC-BKG-05 9/19/12 1641 6 in. Thoron 0.00 0.56 0.56 0.4 Source 1

WAC-BKG-06 9/21/12 0954 2 in. Thoron 0.17 0.80 0.97 0.4 85’ west of 

Source 1

pCi/L = Picocuries per liter

NE = Northeast

[Ref. 19, pp. 12, 23-29, 52-54, 58; 20, pp. 8-9; 25, pp. 1, 3-4; Figure 7 of this HRS documentation record]

Based on these four projected maximum background concentrations with consideration of the level of uncertainty (WAC-BKG-01, duplicate readings at WACBKG-05, and WAC-BKG-06), the mean site-specific background concentration is calculated as follows [Ref. 25, pp. 1, 3]: 

Mean site-specific background (x) = (0.56 + 0.66 + 0.56 + 0.97)/4 pCi/L = 0.69 pCi/L
28

Air-Observed Release

Contaminated Samples

For radionuclides that occur naturally such as thoron, observed release is established when a measured concentration 

in units of activity (such as pCi/L) are at a level that equals or exceeds a value two standard deviations above the 

mean site-specific background concentration for that radionuclide in that type of sample [Ref. 1, Section 7.1.1]. The 

equation for standard deviation (s) of the sample set is as follows [Ref. 25, p. 2]: 

s = 

2

)(*) 1

1 ( ∑ − − xx

n

i

where n = number of background measurements (4) 

xi = each measured background concentration

x = mean site-specific background concentration (0.69 pCi/L)

Based on the projected maximum background concentrations and the calculated mean site-specific background 

concentration of 0.69 pCi/L, the standard deviation (s) of the background sample set is calculated below [Ref. 25, p. 

2]: 

s = ])69.097.0()69.056.0()69.066.0()69.056.0[(*) 14

1 ( 2 2 2 2 −+−+−+− −

s = 0.19 pCi/L

Based on the calculation, the standard deviation (s) of the site-specific background thoron concentration 

measurements is 0.19 pCi/L, and two times the standard deviation is 0.38 pCi/L [Ref. 25, p. 2]. As stated above, 

concentrations that equal or exceed a value two standard deviations above the mean site-specific background 

concentration establish the observed release. Therefore, for the WACC site, concentrations that equal or exceed 

1.07 pCi/L (i.e., 0.69 pCi/L + 0.38 pCi/L) establish the observed release [Ref. 1, Section 7.1.1; 25, pp. 2-3]. As 

shown in Table 6 below, nine samples from seven locations meet this criterion for observed release [Ref. 25, p. 3]. 

Duplicate samples WAC-SPUR-02 and WAC-SPUR-02-A were collected simultaneously at location WAC-SPUR02 with two RAD7 meters, and WAC-SPUR-02-ELEV was collected from a 38-inch height at the same location

[Ref. 19, p. 24].
29

Air-Observed Release

Contaminated Samples (continued)

TABLE 6. CONTAMINATED SAMPLES

Sample ID Date Time Height Hazardous 

Substance

Concentration

(pCi/L)

Uncertainty 

(pCi/L)

Projected 

Minimum (pCi/L)

Lower Limit of 

Detection (pCi/L)

Location

WAC-SPUR-01 9/20/12 1015 1.5 in. Thoron 61.8 6.19 55.61 0.4 On source

WAC-SPUR-02 9/20/12 1209 2 in. Thoron 366 16.1 349.9 0.4 On source

WAC-SPUR-02A 9/20/12 1209 2 in. Thoron 301 13.5 287.5 0.4 On source

WAC-SPUR-02-ELEV 9/20/12 1344 38 in. Thoron 6.19 2.17 4.02 0.4 On source

WAC-PER-01 9/20/12 1343 2 in. Thoron 2.98 1.77 1.21 0.4 5’ east of

Source 1 

WAC-PER-05 9/20/12 1518 2 in. Thoron 3.94 1.80 2.14 0.4 5’ east of

Source 1

WAC-PER-13 9/21/12 1259 1.5 in. Thoron 3.80 1.77 2.03 0.4 20’ south 

of Source 1

WAC-PER-16 9/21/12 1126 2 in. Thoron 10.3 2.71 7.59 0.4 5’ south of

Source 1

WAC-PER-18 9/21/12 1129 2 in. Thoron 8.61 2.74 5.87 0.4 On source

pCi/L = Picocuries per liter

[Ref. 19, pp. 23-29; 20, pp. 8-9; 25, pp. 1, 3-4; Figure 7 of this HRS documentation record]
30

Air-Observed Release

Level I Samples

There are no benchmarks for thoron; therefore, there are no Level I samples [Ref. 1, Section 2.5; 2, pp. 20-21, 24].

Hazardous Substances Released:

Thoron (a.k.a. Radon-220)

Attribution

During its operation, WACC processed monazite sands at the subject property [Ref. 5, pp. 142, 153-154; 7, pp. 4-5]. 

Monazite contains approximately 6-8% thorium, and residues at the WACC facility property were enriched to about 

30% thorium [Ref. 5, pp. 142, 153-154]. The NYCDDC investigation showed that Source 1 contains these 

abandoned radioactive residues, including elevated levels of thorium-232 [Ref. 5, pp. 41-47, 81-84]. The 

radioactive decay of thorium-232, which has a half-life of 14 billion years, proceeds as follows (radioactive halflives in parentheses): radium-228 (5.8 years), actinium-228 (6.1 hours), thorium-228 (1.9 years), radium-224 (3.7 

days), radon-220 (56 seconds), polonium-216 (0.15 second), lead-212 (11 hours), bismuth-212 (61 minutes), 

polonium-212 (310 nanoseconds) and thallium-208 (3.1 minutes), and lead-208 (stable) [Ref. 22, pp. 1, 4]. Due to 

the length of time since processing of the monazite sands (about 60 years or more), it is reasonable to assume secular 

equilibrium (i.e., the activities of all radionuclides within the series are nearly equal) for these radionuclides in 

Source 1 [Ref. 22, p. 1]. The radioactive gas thoron is solely produced from the thorium-232 decay series, and it 

emanates from surfaces where thorium-232 is present [Ref. 18, p. 1; 22, pp. 1, 4]. One of the hazards associated 

with airborne thoron comes from its radioactive decay products, a large fraction of which remain suspended in the 

air where they can be inhaled and deposited in the lungs [Ref. 18, p. 3]. There are no other known sources of thoron 

in the site vicinity [Ref. 13, pp. 15-228]. 

The results of the NYCDDC investigation show that the contaminated soil at the source is at depths within 1 foot of 

the ground surface in the former rail spur, where there are exposed soil areas [Ref. 5, pp. 8, 41-47]. This situation 

indicates that Source 1 is not contained for particulate or gaseous releases to the air migration pathway [Ref. 1, 

Section 6.1.2, Tables 6-3 and 6-9].

Based on these considerations, the radioactive substances associated with Source 1 are considered to have caused the 

significant increase of thoron and the observed release is considered to be attributable to Source 1.

==================================================================================

Air Observed Release Factor Value: 550
31

Air-Toxicity/Mobility

6.2 WASTE CHARACTERISTICS

6.2.1 Toxicity/Mobility

TABLE 7. TOXICITY/MOBILITY

Hazardous 

Substance

Source 

Nos.

Toxicity 

Factor 

Value

Gas Mobility 

Factor Value 

(1) 

Particulate 

Mobility Factor 

Value (HRS Figure 

6-3) (1)

Toxicity/Mobility 

Factor Value 

(HRS Table 6-

13)

References

Thorium-232 1 10,000 N/A 0.0002 2 Ref. 1, Sec.

6.2.1; 2, p. 10

Radium-228 1 10,000 N/A 0.0002 2 Ref. 1, Sec. 

6.2.1; 2, p. 13

Actinium-228 1 (2) N/A 0.0002 (2) Ref. 1, Sec. 

6.2.1; 2, p. 13

Thorium-228 1 10,000 N/A 0.0002 2 Ref. 1, Sec. 

6.2.1; 2, p. 13

Radium-224 1 (2) N/A 0.0002 (2) Ref. 1, Sec. 

6.2.1; 2, p. 13

Thoron

(Radon-220) 

1, OR (2) 1 N/A (2) Ref. 1, Sec. 

6.2.1; 2, p. 13; 

22, pp. 1, 4

Polonium-216 1 (2) N/A 0.0002 (2) Ref. 1, Sec. 

6.2.1; 2, p. 13

Lead-212 1 (2) N/A 0.0002 (2) Ref. 1, Sec. 

6.2.1; 2, p. 13

Bismuth-212 1 (2) N/A 0.0002 (2) Ref. 1, Sec. 

6.2.1; 2, p. 13

Polonium-212 1 (2) N/A 0.0002 (2) Ref. 1, Sec. 

6.2.1; 2, p. 13

Thallium-208 1 (2) N/A 0.0002 (2) Ref. 1, Sec. 

6.2.1; 2, p. 13

Lead-208 (3) 1 10,000 N/A 0.0002 2 Ref. 1, Sec. 

6.2.1; 2, p. 11

OR = Observed Release

N/A = Not applicable (see Note 1 below)

Notes:

(1) Mobility factor values are assigned according to the type of hazardous substance (i.e., gaseous, particulate, or 

gaseous and particulate) [Ref. 1, Section 6.2.1.2]. A mobility factor value of 1 is assigned to each gaseous 

hazardous substance that meets criteria for observed release [Ref. 1, Section 6.2.1.2].

(2) Radium-228 and thorium-228 toxicity factor values listed (which are based on cancer risk estimates for these 

radionuclides) include the contributions from their short-lived decay products, assuming equal activity 

concentrations (i.e., secular equilibrium) with the principal or parent nuclide in the environment. For radium-228, 

the toxicity factor value includes consideration of its decay product actinium-228. For thorium-228, the toxicity 

factor value includes consideration of its decay products radium-224, radon-220, polonium-216, lead-212, bismuth212, polonium-212, and thallium-208 [Ref. 2, p. 13; 32, pp. 11, 18-19].

(3) Lead-208 is the final, stable product of the thorium-232 decay series [Ref. 22, p. 4]; therefore, the toxicity and 

mobility factor values for non-radioactive lead metal are presented [Ref. 2, p. 11]. 

==================================================================================

Toxicity/Mobility Factor Value: 2 
32

Air-Waste Quantity/Characteristics

6.2.2 Hazardous Waste Quantity

TABLE 8. HAZARDOUS WASTE QUANTITY

Source Number Source Hazardous Waste Quantity Is source hazardous constituent 

(HWQ) Value (HRS Section 7.2.5.1.3) quantity data complete? (yes/no)

1 Unknown but >0 No

Sum of Values: 1 (rounded to 1 as specified in HRS Section 7.2.5.2)

The sum corresponds to a hazardous waste quantity factor value of 1 in HRS Table 2-6 [Ref. 1, Sections 2.4.2.2 and 

7.2.5.2]. As shown previously, the radionuclide constituent quantity is not adequately determined for Source 1 (see 

Section 7.2.5.1.1 of this HRS documentation record) and targets for the air migration pathway are subject to Level II 

concentrations (see Section 6.3.2.3 of this HRS documentation record). The HRS states that if the radionuclide 

constituent quantity is not adequately determined for one or more sources and if any target for the migration 

pathway is subject to Level I or Level II concentrations, then the value from Table 2-6 or a value of 100, whichever 

is greater, is assigned as the hazardous waste quantity factor value for that pathway [Ref. 1, Section 7.2.5.2]. 

Therefore, a hazardous waste quantity factor value of 100 is assigned for the air migration pathway. 

6.2.3 Waste Characteristics Factor Category Value

Four hazardous substances (thorium-232, radium-228, thorium-228, and lead-208) correspond to a toxicity/mobility 

factor value of 2, as shown previously (see Section 6.2.1 of this HRS documentation record). 

Toxicity/Mobility Factor Value (2) x Hazardous

Hazardous Waste Quantity Factor Value (100): 2 x 102

The waste characteristics product of 2 x 102 corresponds to a Waste Characteristics Factor Category Value of 3 in 

HRS Table 2-7 [Ref. 1, Section 2.4.3.1].

==================================================================================

Hazardous Waste Quantity Factor Value: 100

Waste Characteristics Factor Category Value: 3 
33

Air-Targets

6.3 TARGETS

The documented observed release extends 20 feet (0.0034 mile) south of Source 1 [Figure 6; Ref. 20, pp. 22, 33]. 

There are no available benchmarks for thoron (i.e., radon-220), so there are no Level I targets [Ref. 1, Section 2.5; 2, 

pp. 20-21, 24]. Therefore, populations within the On-Source and Greater than 0 to 1⁄4 mile distance categories (more 

than 6,800 residents, workers, and students) are considered as subject to Level II concentrations (see Section 6.3.2.3

of this HS documentation record). The Potential Contamination factor value for populations outside the 1⁄4-mile 

radius is not scored because it is not expected to change the overall HRS site score and the listing decision is not 

significantly affected by this factor [Ref. 21, pp. 2, 5-148; 154]. 

EPA obtained residential population data for the target distance limit from the U.S. Census Bureau website, in the 

form of 2010 Census block population data and geographic information system (GIS) coverage; assigned 

populations to specific distance categories based on the percent of the area of each Census block within each 

distance category; and calculated total residential populations for each distance category [Ref. 21, pp. 1-2]. Other 

populations within 1⁄4 mile of the source and considered here include 704 students enrolled at the Frances E. Carter 

public school (K384) and 7 on-source workers [Ref. 19, pp. 30-33; 21, pp. 1-2, 149-153]. Workers within the 

Greater than 0 to 1⁄4 mile distance category are not considered for the population factor because the exact number is 

unknown; the inclusion of these targets is not expected to change the overall HRS site score because the air 

migration pathway score achieves the maximum value of 100.00 based on the populations already evaluated (see 

pages 1-3 of this HRS documentation record).

Level I Distance Categories

Distance categories subject to Level I concentrations: 

No Level I concentrations (there are no available benchmarks for thoron)

Level II Distance Categories

Farthest Sample

Sample ID: WAC-PER-13

Location: vacant land at south end of former rail spur

Reference: Figure 7; Ref. 19, pp. 11, 26, 29; Ref. 20, pp. 22, 26, 33

Nearest Source: Source 1 (Waste Tailings) 

Distance from the source in miles: 0.0034

Reference: Figure 7

Distance categories subject to Level II concentrations:

On-source

Greater than 0 to 1⁄4 mile

Actual Contamination Distance Categories

On-source

Greater than 0 to 1⁄4 mile

Potential Contamination Distance Categories

Greater than 1⁄4 to 1⁄2 mile

Greater than 1⁄2 to 1 mile

Greater than 1 to 2 miles

Greater than 2 to 3 miles

Greater than 3 to 4 miles
34

Air-Nearest Individual

6.3.1 Nearest Individual Factor

There are no residences or regularly occupied buildings or areas that are subject to Level I concentrations because 

there are no available benchmarks for thoron (i.e., radon-220) [Ref. 1, Section 2.5; 2, pp. 20-21, 24]. There are 

multiple regularly occupied buildings that are subject to Level II concentrations (see Section 6.3.2 of this HRS 

documentation record). Therefore, a nearest individual factor value of 45 is assigned [Ref. 1, Sections 2.5 and 

6.3.1].

Nearest Individual - Level II Concentrations

Residence, building or area subject to Level II concentrations:

Due to the observed release to the air migration pathway on the source and 20 feet outside the source boundary at 

the WACC site, the populations within the On-source and Greater than 0 to 1⁄4 mile distance categories are

considered as subject to Level II concentrations [Ref. 1, Sections 2.5, 6.1.1, and 6.3]. The buildings on Source 1

where the air release has occurred are regularly occupied by workers [Ref. 5, pp. 13-19; 19, pp. 4-5, 30-33]. 

Location: 1127-1139 Irving Avenue (on-source) 

Nearest Source: Source 1

Distance from the nearest source in miles: 0.00 

References: Figures 6, 7; Ref. 12, p. 2; 19, pp. 13-26, 30-33; 20, p. 20; 27, pp. 1-3 

==================================================================================

Nearest Individual Factor Value: 45
35

Air-Level I/Level II Populations

6.3.2 Population

6.3.2.2 Level I Concentrations

The Level I concentrations factor value is 0 because there are no available benchmarks for thoron (i.e., radon-220), 

so there are no people subject to Level I concentrations [Ref. 1, Sections 6.3.2.2 and 7.3.2; 2, pp. 20-21, 24].

6.3.2.3 Level II Concentrations

Due to the observed release to the air migration pathway on the source and 20 feet outside the source boundary at 

the WACC site, and given that there are no available benchmarks for thoron (i.e., radon-220), the populations within 

the On-source and Greater than 0 to 1⁄4 mile distance categories are considered as subject to Level II concentrations

[Ref. 1, Sections 2.5, 6.1.1, and 6.3; 20, p. 20]. Based on 2010 Census data for Kings County and Queens County, 

there are a total of approximately 6,159.79 residents within 1⁄4 mile of the source; these populations are considered as 

subject to Level II concentrations [Ref. 21, pp. 1-4, 154]. Other populations considered as subject to Level II 

concentrations include 7 on-source workers and 704 students enrolled at the Frances E. Carter public school (K384), 

which is located within 1⁄4 mile of the source on Kings County Tract 409, Block 2002 [Ref. 19, pp. 3-5, 30-33; 21, 

pp. 1-2, 149-153]. Based on this assessment, the total population considered as subject to Level II concentrations 

within the On-source and Greater than 0 to 1⁄4 mile distance categories is 6,870.79, which is assigned as the Level II 

concentrations factor value for the air migration pathway [Ref. 1, Section 6.3.2.3]. 

TABLE 9. LEVEL II CONCENTRATIONS

Distance Category Population Reference(s)

On-source (workers) 7.00 Ref. 19, pp. 30-33; 21, pp. 1-2

Greater than 0 to 1⁄4 mile (residents) 6,159.79 Ref. 21, pp. 1-2, 4, 154

Greater than 0 to 1⁄4 mile (students) 704.00 Ref. 21, pp. 1-2, 149-153

Total Level II 6,870.79

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Population Exposed to Level I Concentrations: 0

Level I Concentrations Factor Value: 0

Level II Concentrations Factor Value: 6,870.79
36

Air-Potential Contamination Population

6.3.2.4 Potential Contamination

The Potential Contamination factor value is not scored because the listing decision is not significantly affected by 

this factor.

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Distance-weighted Population Subject to Potential Contamination: NS

Potential Contamination Factor Value: NS
37

Air-Resources/Sensitive Environments

6.3.3 Resources

The Resources factor value is not scored because the listing decision is not significantly affected by this factor.

6.3.4 Sensitive Environments

The Sensitive Environments factor values are not scored because the listing decision is not significantly affected by 

those factors.

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Resources Factor Value: NS

Sensitive Environment Actual Contamination Factor Value: NS

Sensitive Environments Potential Contamination Factor Value: NS