HRS DOCUMENTATION RECORD--REVIEW COVER SHEET

Name of Site: Corozal Well

CERCLIS ID No.: PRN000206452

Date Prepared: September 2011

Contact Persons

Site Investigations: Denise Zeno (212) 637-4319 U.S. Environmental Protection Agency New York, NY

Documentation Record: Ildefonso Acosta (212) 637-4344 U.S. Environmental Protection Agency New York, NY

Pathways, Components, or Threats Not Scored

The surface water, soil exposure, and air pathways were not scored because the listing decision is not significantly affected by those pathways. The site score is suffici ent to list the site on the ground water pathway score.This page has been left blank intentionally.HRS DOCUMENTATION RECORD

Name of Site: Corozal Well

CERCLIS ID No.: PRN000206452 [Ref. 3, p. 1]

EPA Region: 2 Date Prepared: September 2011

Street Address of Site: * [Off of] Carretera 811 Km 3.0 [Ref. 3, p. 1]

County, State, and ZIP Code: Corozal , Puerto Rico 00783 [Ref. 3, p. 1]

General Location in the State: interior, north-central Puerto Rico [Figure 1]

Topographic Map: Corozal, PR [Ref. 4, p. 1]

Latitude: * 18° 17' 44.56" (18.295711°) North Longitude: * 66° 17' 10.34" (-66.286205°) West

[Figure 1; Ref.; 4, p. 1; 5, pp. 1-2]

The site consists of a ground water plume with no identified sour ce(s) of contamination [Figure 1; Ref. 3, p. 1]. The area of observed ground water contamination consists of the Com unidad Santana community supply well, which is the sole source of drinking water for a community of more than 200 peopl e [Figure 1; Ref. 7, pp. 2-18; 11, pp. 58-130; 28, p. 2]. The reference point for the street address and site latitude/longitude coordinates is the Comunidad Santana well [Figure 1; Ref. 1, p. 51595; 5, pp. 1-2]. The Comunidad Santana well does not have a specific street address (i.e., no number), but it is accessible from Carretera 811 (i.e., Route 811); the street address listed here identifies the kilometer marker of the unnamed side road that leads to the well location [Figure 1; Ref. 3, p. 1].

* The street address, coordinates, and contaminant locati ons presented in this HRS documentation record identify the general area 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 fo r 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, placed, or otherwise come to be located.” Generally, HRS scoring and the subsequent lis ting 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 100.00 Surface Water Pathway Not Scored Soil Exposure Pathway Not Scored Air Pathway Not Scored

HRS SITE SCORE 50.00

1WORKSHEET FOR COMPUTING HRS SITE SCORE

Corozal Well

S S 2

1. Ground Water Migration Pathway Score (S gw ) 100.00 10,000 (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 (S

sw ) Not Scored Enter the larger of lines 2a and 2b as the pathway score.

3. Soil Exposure Pathway Score (S

s ) Not Scored (from Table 5-1, line 22)

4. Air Migration Pathway Score (S

a ) Not Scored (from Table 6-1, line 12)

5. Total of S gw 2 + S

sw 2 + S

s 2 + S

a 2 10,000

6. HRS Site Score Divide the value on line 5 by 4 and take the square root 50.00

2GROUND WATER MIGRATION PATHWAY SCORESHEET

Corozal Well

GROUND WATER MIGRATION PATHWAY Factor Categories & Factors MAXIMUM VALUE VALUE ASSIGNED

Likelihood of Release
1. Observed Release 550 550

2. Potential to Release

2a. Containment 10 not scored 2b. Net Precipitation 10 not scored 2c. Depth to Aquifer 5 not scored

2d. Travel Time 35 not scored

2e. Potential to Release [lines 2a(2b+2c+2d)] 500 not scored

3. Likelihood of Release 550 550

Waste Characteristics 4. Toxicity/Mobility * 100 5. Hazardous Waste Quantity * 100

6. Waste Characteristics 100 10

Targets
7. Nearest Well 50 50 8. Population

8a. Level I Concentrations ** 2,170

8b. Level II Concentrations ** 0

8c. Potential Contamination ** not scored 8d. Population (lines 8a+8b+8c) ** 2,170

9. Resources 5 0

10. Wellhead Protection Area 20 0 11. Targets (lines 7+8d+9+10) ** 2,220

12. Aquifer Score (lines 3x6x11 divided by 82,500) 100 100.00

13. Ground Water Migration Pathway Score (Sgw) 100 100.00

* Maximum value applies to waste characteristics category. ** Maximum value not applicable.

3REFERENCES

Reference
Number Description of the Reference

1. U.S. Environmental Protection Agency (EPA). Hazard Ranking System, Final Rule . Federal Register, Volume 55, No. 241, pp. 51532-51667. A comp lete copy of HRS is available at http://www.epa.gov/superfund/sites/ npl/hrsres/index.htm#HRS Rule . December 14, 1990. [138 pages]

2. EPA. Superfund Chemical Data Matrix, SCDM Data Version: 1/27/2004, Appendices B-I (Hazardous Substance Factor Values) and B-II (Hazardous Substa nce Benchmarks); excerpts downloaded on April 6,

2011 . A complete copy of SCDM is available at http://www.epa.gov/superfund/site s/npl/hrsres/tools/scdm.htm . [5 pages]

3. EPA. Superfund Site Information, Corozal Well, Corozal, Puerto Rico: Site Information and Actions

. Downloaded from http://cumulis.epa.gov/supercpa d/cursites/csitinfo.cfm?id=0206452 on March 7, 2011. [2 pages]

4. U.S. Department of the Interior Geological Survey (USGS). Corozal Quadrangle, Puerto Rico, 7.5-Minute Series (Topographic) . 1972. [1 page]

5. Gilliland, Gerry, Weston Solutions, Inc., (WESTON). Project Note to Corozal Well HRS Site File, Subject: Latitude and Longitude Determination . March 25, 2011. [3 pages]

6. Gilliland, Gerry, WESTON. Telecon Note, record of conversations with various employees at PR Department of Health (PRDOH), Subjec t: Contaminated Well in Corozal/Naranjito . February 9, 2011. [1 page]

7. Marrero, Marilyn, PRDOH. Transmittal Memo to Ana Mendoza, Subject: Report of Change in Comunidad Santana System (724147); with translation by WESTON attached . February 25, 2008. [18 pages]

8. Torres, Javier O., PRDOH. Email to Gerry Gilliland, WESTON, S ubject: [Attached] Comunidad Santana
results . February 10, 2011. [15 pages]

9. Aviles Santiago, Edward, Environmental Laboratory, Puerto Rico Environmental Quality Board (PREQB). Memorandum to Roberto Ayala Prado, Re: Envi ronmental Emergency Naranjito, Cedro Abajo Community; with translation by WESTON attached . January 31, 2011. [17 pages]

10. WESTON Removal Support Team 2 (RST 2). Field Logbook, Corozal Well Site . December 2010 – February 2011. [12 pages]

11. Huertas, Carlos L., WESTON RST 2. Sampling Trip Report – Corozal Well Site, Cedro Abajo Ward, Corozal, Puerto Rico . February 28, 2011. [130 pages]

12. Zeno, Denise, EPA. Email to Gerald Gilliland, WESTON, Subj ect: Fw: Attached are the regionally
assessed data for the Corozal Well site under th e CLP Case # 40904, SDG # B8FT1, B8FT2, B8FW2

. February 22, 2011. [13 pages]

13. Huertas, Carlos L., WESTON RST 2. Email to Gerald Gilliland, WESTON, Subject: Corozal Well – January Sampling Event . February 22, 2011. [46 pages]

14. Huertas, Carlos L., WESTON RST 2. Email to Gerald Gilliland, WESTON, Subject: Corozal - Samples collected on February Event . February 22, 2011. [36 pages]

4REFERENCES (continued)

Reference
Number Description of the Reference

15. Munch, J.W., ed., EPA National E xposure Research Laboratory. Method 524.2, Measurement of Purgeable Organic Compounds in Water by Capillary Column Gas Chromatography/Mass Spectrometry,
Revision 4.1 . EPA Office of Research and Development. 1995. [48 pages]

16. Agency for Toxic Substances & Disease Registry (ATSDR). ATSDR ToxFAQs, Tetrachloroethylene,

CAS # 127-18-4 . U.S. Department of Health and Human Services. September 1997. [2 pages]

17. Environmental Data Resources, Inc. (EDR). The EDR Radius MapTM Report with GeoCheck®, Corozal Well, Carretera 811 Km 3.0 Interior, Na ranjito, PR 00719, Inquiry Number: 2999081.2s . February 24, 2011. [41 pages]

18. Puerto Rico Environmental Quality Board (PREQB). Final Wellhead Protection Program . April 1991. [158 pages]

19. WESTON. Field Logbook with Photo Documentation, Corozal Site Discovery Initiative, WO#

20405.012.013.1296.00 . December 6-9, 2010. [21 pages]

20. Gilliland, Gerald, WESTON. Email Message to Denise Zeno, EPA, Subject: Corozal Well Update . March 20, 2011. [1 page]

21. Huertas, Carlos, WESTON/SEA Consulting. Email Message with attachment to Gerald Gilliland, WESTON, Subject: Corozal Well- GAC unit data . May 3, 2011. [2 pages]

22. WESTON. Field Logbooks # 1371-4E-ALNM and 1371-4E-AMN T, with GEOPROBE Soil Boring Logs and Photo Documentation, Corozal Well Site, Corozal/Naranjito, PR . February-March 2011. [88 pages]

23. Gilliland, Gerald V., WESTON. Sampling Trip Report, Corozal Well Site, Document Control No. 1371-

2A-AMJO . April 26, 2011. [27 pages]

24. Arnone, Russell, EPA. Email with attachments to Denise Ze no, EPA and Gerald Gilliland, WESTON, Subject: Attached are the regionally assessed data for the Corozol [ sic ] Well site under the CLP Case # 41136, SDG # B94L4 . April 28, 2011. [41 pages]

25. Arnone, Russell, EPA. Email with attachments to Denise Ze no, EPA and Gerald Gilliland, WESTON, Subject: Attached are the regionally assessed data for the Corozol [ sic ] Well site under the CLP Case # 41136, SDG # B94M0 . April 19, 2011. [73 pages]

26. Arnone, Russell, EPA. Email with attachments forwarded to Gerald Gilliland, WESTON, Subject: Attached are the regionally assessed data for the Corozal Well site under the CLP Case # 41136, SDG #

B94G3 . April 12, 2011. [62 pages]

27. Arnone, Russell, EPA. Email with attachments to Denise Ze no, EPA and Gerald Gilliland, WESTON, Subject: Attached are the regionally assessed data for the Corozol [ sic ] Well site under the CLP Case # 41136, SDG # B94K1, B94H8 . May 6, 2011. [112 pages]

28. Feliciano, Jaime, JFA Geological and Environmental Scie ntists, P.S.C., and Chris Taylor, GeoView, Inc. Report on Geophysical Well Logging Study, Groundwater I nvestigation Site, Municipality of Corozal, PR,
JFA Job No. 397-11 . Prepared for KEMRON Environmental Serv ices, Inc. April 13, 2011. [Excerpt, 16 pages]

56 REFERENCES (continued)

Reference
Number Description of the Reference

29. Nelson, Arthur E., USGS. Cretaceous and Tertiary Rocks in the Corozal Quadrangle, Northern Puerto
Rico . Geological Survey Bulletin 1244-C. Prepared in cooperation with the Economic Development Administration of Puerto Rico. 1966. [24 pages]

30. Rodríguez, José M., USGS. Assessment of Ground-Water Withdrawals at Municipal Industrial Parks in Puerto Rico, 2000; excerpts . Scientific Investigation Report 2004- 5029. Prepared in cooperation with Puerto Rico Industrial Development Co mpany (PRIDCO). 2004. [30 pages]

31. Nelson, Arthur E., USGS. Geologic Map of the Corozal Quadrangle, Puerto Rico . Miscellaneous Geologic Investigations Map I-473. Prepared in cooperation with the Economic Development Administration of Puerto Rico. 1967. [1 sheet]

32. Sumbaly, Smita, WESTON RST 2, Region II. Transmittal Memo to Angel Rodriguez, Caribbean Environmental Protection Branch, EPA Region II, Subject: Corozal Well Site, Data Validation

Assessment . May 19, 2011. [65 pages]SS – Site Summary

SITE SUMMARY

The Corozal Well site (CERCLIS ID No. PRN000206452) consists of a ground water plume with no identified source(s) of contamination, located in Barrio Palos Blancos, Corozal, a rural residential community in interior north-central Puerto Rico [Figure 1; Ref. 3, p. 1; 4, p. 1]. The site straddl es the border between the municipalities of Corozal and Naranjito, and the geographic coordinates of the site are 18  ̊ 17' 44.56" north latitude and 66  ̊ 17' 10.34" west longitude, based on the location of the Comunidad Santana community supply well [Figur e 1; Ref. 4, p. 1; 5, pp. 1-2]. A Site Location Map is presented as Figure 1.

The contamination currently affects the Comunidad Santana we ll, which is the sole source of drinking water for a rural community of more than 200 people (PWSID # PR0724147) [Ref. 6, p. 1; 7, pp. 2-12, 14-18; 11, pp. 6, 11, 58-130]. Ground water contamination in the well was discovered in November 2010, when Puerto Rico Aqueduct and Sewer Authority (PRASA) collected samples from non-PRASA system we lls on behalf of Puerto Rico Department of Health (PRDOH) [Ref. 6, p. 1; 8, pp. 1-15]. Samples collected from the Comunidad Santana well on November 12 and 23, 2010 indicated the presence of tetrachloroethylene (PCE) at concentrations of 17 and 92.5 micrograms per liter (μg/L), above the U.S. Environmental Protection Agency (EPA) Safe Drinking Water Act (SDWA) Maximum Contaminant Level (MCL) of 5 μ g/L [Ref. 2, p. 5; 8, pp. 8, 12]. Upon discovery and confirmation of the MCL exceedance, PRDOH ordered the well to be closed [Ref. 6, p. 1]. The pump was remove d from the well to avoid usage, while PRASA, the National Guard, and subsequently EPA provided an alternate water source for the affected residents [Ref. 19, pp. 7-8, 18-19]. In February-March 2011, EPA installed a gra nular-activated-carbon (GAC) treatment syst em at the site, reinstalled the well pump, and began to pump treated well water into the community water supply for distribution [Ref. 20, p. 1; 21, pp. 1-2; 22, p. 8, 19, 22].

Additional ground water samples collected by Puerto Rico Environmental Quality Board (PREQB) and EPA between November 2010 and March 2011 confirm the presence of PCE in the Comunidad Santana well, at concentrations ranging from 39 to 120 μg/L [Ref. 9, pp. 2, 9, 16; 10, pp. 1-6; 11, pp. 2-3, 7, 10, 13-14, 29, 37, 46; 12, pp. 1, 4; 14, pp. 6, 12; 23, pp. 5, 13, 21; 24, pp. 2, 17-18]. Surf ace water sampling by PREQB and EPA also indicates the presence of PCE in the unnamed creek adjacent to the well, at concentrations ranging fro m an estimated 0.86 μg/L to 23 μg/L [Ref. 9, pp. 2, 4, 9-10, 16-17; 23, pp. 5-6, 13, 15; 25, pp. 4-10, 16, 33-42, 49-50].

Since discovery of the contamination, EPA and PREQB ha ve attempted to identify the source(s) of observed ground
water contamination. Reconnaissance efforts indicate that there are few commercial/industrial operations in the area surrounding the contaminated well, and there is no direct evid ence of PCE use at any nearby facilities [Ref. 19, pp. 4-6, 9-10, 14-16, 19; 22, pp. 3-9]. EPA also performed an envi ronmental database search, which did not identify any known possible source facilities within 1 mile of the site [Ref. 17, pp. 1-14]. Aqueous samples collected by PREQB from the two closest known commercial/industrial facilities (RO Rental E quipment, Inc. and ERC Manufacturing) did not indicate the presence of PCE [Ref. 9, pp. 2-3, 13-14, 17; 19, pp. 4- 5]. In March 2011, EPA collected soil samples from the same two facilities, as well as a ground water sample from an industr ial well at the RO facility [Ref. 22, pp. 21-55, 75-88; 23, pp. 3, 5, 7-9, 13, 21-22, 24, 26]. EPA also collected so il samples from hillsides upstream of the well, including the property of a cabinetmaker [Ref. 22, pp. 13-18, 66-72; 23, pp. 3, 6-7, 13, 17]. The analytical results indicate that PCE is not present in soils upstream of the well, in soils at either of the two industrial facilities, or in the ground water well at the RO facility [Ref. 24, pp. 8, 25-26; 26, pp. 2-20, 24-52; 27, pp. 2-22, 26-63, 70-78, 84-97]. Two other community supply wells located within approximately 0.3 mile of the contaminated well are not yet affected by the PCE contamination [Ref. 23, pp. 3, 5, 13, 21-22; 24, pp. 4-5, 13, 19-22, 31-32]. Based on these considerati ons, there is not sufficient evidence to attribute the ground water contamination in the Comunidad Sa ntana well specifically to sources at any nearby facilities; therefore, there is no identifie d source(s) of contamination.

7

# ! < COMUNIDAD SANTANA WELL

DATE:

FIGUR E #: CLIENT NAM E: PR OJECT: TIT LE:

R 

### @ A @ A

8/17/2011

USEPA COROZAL WELL SITE COROZAL, PUERTO RICO


### SITE LOCATION MAP

1P:\SAT2\Corozal\GIS\MXD\1210_SamplingPlan\09223_Corozal_SiteLocation_v2.mxd Puerto Rico 

# ±

1,500 0 1,500 3,000 750

Graphic Scale in Feet9 SD-Characterization and Containment

Source No.: 1

SOURCE DESCRIPTION

2.2 SOURCE CHARACTERIZATION

Number of the source: 1

Source Type of the source: Other

Name and description of the source: Corozal Well

Source 1 is considered a contaminated ground water plum e of unknown volume without an identified source. The Comunidad Santana community water system (PWSID # PR0724147) consists of a single well that serves a population of 217 people [Ref. 7, pp. 3-4, 14-18; 11, pp. 58-130]. The resu lts for samples collected from the Comunidad Santana well in November 2010 by PRASA on behalf of PRDOH indicated the presence of PCE at concentrations of 17 and 92.5 μ g/L [Ref. 6, p. 1; 8, pp. 8, 12]. PRDOH responded to this analy tical result by ordering the well to be closed because the PCE
concentrations exceeded the MCL of 5 μ g/L [Ref. 2, p. 5; 6, p. 1; 8, pp. 8, 12].

Ground water samples collected by EPA from the Comunidad Santana well in December 2010, February 2011 and March 2011 confirmed the presence of PCE in the well, whereas PCE was not detected in several other potable and non-potable wells in the region [Ref. 10, pp. 2-5; 11, pp. 2-3, 7, 10, 13-14, 29, 37, 46; 12, pp. 1, 4; 13, pp. 1, 4, 25-28; 14, pp. 1, 6, 4, 12, 24]. Section 3.1.1 presents the details of the EPA sampling efforts and results.

As discussed in Section 3.1.1, EPA has not yet identifie d a surface source of the ground water contaminants in the Comunidad Santana well despite extensive disc overy, reconnaissance, and sampling efforts.

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

The ground water plume is identified by c ontamination found in the Comunidad Sant ana supply well. For the purpose of this report, this well represents a minimum of the plume extent . The well is located in interior, north-central Puerto Rico and is shown in Figure 1.

Containment

Release to ground water:

Based on evidence of hazardous substance migration (contamin ation detected in ground water samples collected from the Comunidad Santana well) and due to the fact that there is nothing to prevent the plume from migrating further, a containment factor of 10 is assigned [Ref. 1, p. 51596].10 SD- Hazardous Substances

Source No.: 1

2.4.1 Hazardous Substances

Ground water samples collected by PRASA in 2010 and by EPA in 2010 and 2011 showed the presence of chlorinated solvents in the Comunidad Santana community supply well, as described below. Background sample locations and contaminant levels for comparison to the contamin ated samples are discussed in Section 3.1.1.

PRASA Sampling (on behalf of PRDOH) – Ground Water Samples: November 2010

PRASA collected ground water samples from the Comunidad Sa ntana well on November 12 and 23, 2010 [Ref. 6, p. 1; 8, pp. 8, 12]. The results are presented in the table below (Note: PRASA reported its results and method detection limits [MDL] in mg/L, which EPA has converted to μ g/L for consistency with the EPA data presented in this report) [Ref. 8, pp. 8, 12]. The PRASA samples were collected and analyzed according to EPA Method 524.2 [Ref. 8, pp. 8, 12]. The applicable concentration range of Method 524.2 can be 0.02–200 μ g/L or 0.02–20 μ g/L [Ref. 15, p. 4]. The method requires a number of quality controls, incl uding demonstrations of capability, accuracy , and precision; analysis of blanks and surrogates; and determinations of MDLs for each anal yte [Ref. 15, pp. 16-19]. EPA defines MDL as the “lowest concentration of analyte that a method can detect reliably in either a sample or blank” [Ref. 1, p. 51586]. The PRASA analytical results include MDLs for all parameters [Ref. 8, pp. 1-15].

Hazardous Substance Sample Number Date Sampled Result ( μ g/L) MDL ( μ g/L) Reference

1622998 11/12/2010 17.0 0.5 8, p. 12 PCE

1628221 11/23/2010 92.5 5.0 8, p. 8

EPA Sampling Events – Ground Wat er Samples: December 2010-March 2011

EPA collected ground water samples from the Comunidad Santana well and background ground water samples from nearby wells from December 2010 to March 2011 [Ref. 10, pp. 1-12; 11, pp. 2-3, 7, 10, 13-14, 29, 37, 46, 48; 22, pp. 19- 24, 39, 73-74, 79-81; 23, pp. 3, 5, 13, 19, 21-22; 24, pp. 2-8, 13, 17-26, 31-32; 25, pp. 2, 23, 31-32, 59-60]. Samples collected in December 2010, January 2011, and March 2011 were analyzed for TCL VOCs through EPA’s Contract Laboratory Program (CLP) according to Statement of Work SOM01.2, while the February 2011 samples were analyzed outside CLP according to EPA Method 8260B with preparati on Method 5030B [Ref. 11, pp. 2-3, 13-14, 29, 37, 46-49; 12, pp. 1-13; 13, pp. 1-46; 14, pp. 1-2, 5-7, 11-13, 17-19, 23-25, 27-35; 23, pp. 3- 5, 19, 21-22; 24, pp. 2-8, 13, 17-26, 31- 32; 25, pp. 2, 23, 31-32, 59-60]. The CLP results were valid ated according to SOP HW-33/VOA (Revision 1), the current EPA Region 2 Data Validation SOP for Statement of Work SO M01.2 for evaluating organic data [Ref. 12, pp. 1, 5-13; 13, pp. 42-46; 24, pp. 37-41; 25, pp. 69-73]. PDF printouts of the validated Form I results are presented in the data packages where available [Ref. 13, pp. 2, 25-28; 24, pp. 1, 17-36; 25, pp. 1, 31-32, 59- 60]. The February 2011 results were validated according to EPA Region 2 Data Valida tion SOP No. HW-24 (Revision 2) [Ref. 32, p. 13].

PCE was detected in the Comunidad Santana well sa mples at individual concentrations ranging from 39 μ g/L to 120

μ g/L, but was not detected (ND) in background samples from several other wells, as presented in the table below. Additional information regarding background c onditions is presented in Section 3.1.1.11 SD- Hazardous Substances

Source No.: 1

Hazardous
Substance Sample Number Date Sampled Result ( μ g/L) Detection/ Quantitation Limit* ( μ g/L) Reference

GW-MW01-050-01 12/16/2010 110 5

GW-MW01-100-01 12/16/2010 120 5

GW-MW01-100-02 12/16/2010 120 5 10, pp. 2-3; 11, p. 29; 12, pp. 1, 4-13

GW-MW01-140-001 02/09/2011 63.5 0.3

GW-MW01-140-002 02/09/2011 70.0 0.3 10, p. 10; 11, p 46; 14, pp 6, 12; 32, pp. 1, 12-18, 25, 31

1371-GW01 03/29/2011 39 5 23, p. 21; 24, pp. 2, 17-18, 37-41

GW-MW02-00-001** 01/25/2011 ND 5

GW-MW02-00-002** 01/25/2011 ND 5 10, p. 7; 11, p. 37; 13, pp. 4, 25-28,

42-46

1371-GW02** 03/29/2011 ND 5

1371-GW08** 03/29/2011 ND 5 23, pp. 21-22; 24, pp. 4, 13, 19-20, 31-32, 37-41

1371-GW03** 03/29/2011 ND 5 23, p. 22; 24, pp. 5, 21-22, 37-41

1371-GW04** 03/29/2011 ND 5 23, p. 22; 24, pp. 7, 23-24, 37-41

1371-GW05** 03/29/2011 ND 5 23, p. 22; 24, pp. 8, 25-26, 37-41

1371-GW06** 03/21/2011 ND 5 PCE

1371-GW07** 03/21/2011 ND 5 23, p. 19; 25, pp. 2, 23, 31-32, 59-60,

69-73

*Available detection/quantitation limits are as follows:

• December 2010, January 2011, and March 2011: RDL/QL or Quantitation Limit [Ref. 12, p. 4; 13, p. 4; 24, pp. 2, 4-5, 7-8, 13; 25, pp. 2, 23]; equivalent to SQL described in the HRS [Ref. 1, p. 51589]

• February 2011: Minimum Detection Limit [Ref. 14, pp. 6, 12, 24]; equivalent to detection limit (DL) described in the HRS for non-CLP sample analyses [Ref. 1, p. 51589]

**Background samples (see Section 3.1.1)12 SD-Hazardous Waste Quantity

Source No.: 1

2.4.2 Hazardous Waste Quantity

2.4.2.1.1 Hazardous Constituent Quantity

The information available is not sufficient to evaluate Tier A source hazardous waste quantity; therefore, hazardous constituent quantity is not scored (NS) [Ref. 1, pp. 51590-51591].

Hazardous Constituent Quantity (C) Value: NS

2.4.2.1.2 Hazardous Wastestream Quantity

The information available is not sufficient to evaluate Tier B source hazardous waste quantity; therefore, hazardous wastestream quantity is not scored [Ref. 1, p. 51591].

Hazardous Wastestream Quantity (W) Value: NS

2.4.2.1.3 Volume

Because there is a well with samples showing contamination in the ground water but the volume of the contaminated area has not been determined, the volume of the ground water contam ination is considered to be greater than 0 (>0) cubic yards but unknown [Figure 1; Ref. 12, pp. 1, 4-13; 14, pp. 6, 12; 22, pp. 19-24, 39, 73-74, 79- 81; 23, pp. 3, 5, 13, 19, 21- 22; 24, pp. 2-8, 13, 17-26, 31-32; 26, pp. 2, 23, 31-32, 59-60]. The source type is ‘Other,’ so the volume value is divided by 2.5 to obtain the assigned value, as shown below [Ref. 1, p. 51591, Section 2.4.2.1.3, Table 2-5].

Dimension of source (yd 3 ): >0 yd 3 Volume (V) Assigned Value: (>0)/2.5 = >0

2.4.2.1.4 Area

Tier D is not evaluated for source type “other” [Ref. 1, p. 51591, Table 2-5, Section 2.4.2.1.3].

Area of source (ft 2 ): N/A Area (A) Assigned Value: 0

2.4.2.1.5 Source Hazardous Waste Quantity Value

The source hazardous waste quantity value for Source 1 is >0 for Tier C - Volume [Ref. 1, p. 51591].

Source Hazardous Waste Quantity Value: >0SD-Summary

SITE SUMMARY OF SOURCE DESCRIPTIONS

Containment Source Number Source Hazardous Waste Quantity Value Ground Water Surface

Water Air (Gas) Air (Particulate)

1 >0 10 NS NS NS

NS = Not Scored

13GW-General

3.0 GROUND WATER MIGRATION PATHWAY

3.0.1 General Considerations

The site is located in an area underlain by stratified, highly-fractured bedrock of volcanic origin, specifically the Los Negros Formation of Lower and Upper Cretaceous Age [Ref. 28, pp. 3, 6-9; 29, pp. 6-8, 14-15]. This hydrogeologic unit is considered to be a stratum of limited and local ground wate r resources in Corozal, but it functions as a local source of water through fractures, joints, faults and the weathere d-bedrock mantle [Ref. 30, pp. 12-13, 20-21, 25-27]. A geophysical survey of the Comunidad Santana well and n earby wells showed the presence of numerous, large open fractures and fracture zones within the formation, to depths of almost 500 feet [Ref. 28, pp. 5-9]. The geophysical survey identified a large opening of the borehole wall beneath th e casing of the Comunidad Santana well; the geophysical logging suggests that ground water enters the well from a depth of 18 to 23.5 feet in this opening, which might be from borehole washout [Ref. 28, pp. 7-8]. Ground water was encountered within fracture zones, and static water levels ranged from approximately 10 to 40 feet [Ref. 28, p. 5]. The estim ated hydraulic conductivity of hi ghly-fractured igneous rocks
such as those found at the site is 10 -2 centimeters per second (cm/s) [Ref. 1, p. 51601].

The depth of the Comunidad Santana well is 159 feet, and the depths of nearby wells range from 298 to 496 feet [Ref. 28, p. 5]. The wells nearby are all located in the same topogra phic and geologic setting as the Comunidad Santana well (i.e., Los Negros Formation consisting of volcanic rocks located w ithin the mountainous, interior region of Puerto Rico) [Ref. 28, pp. 3, 6-9; 29, pp. 6-8, 14-15; 31, p. 1]. The Comuni dad Santana well serves a population of 217 people; there are no other wells or surface water intakes contributing to the system [Ref. 6, p. 1; 7, pp. 2-12, 14-18].

Based on these considerations, Los Negros Formation is eval uated as the aquifer under consideration, and only targets
within the immediate site area are included for HRS scori ng purposes [Ref. 1, p. 51595]. The aquifer is described in greater detail below:

Stratum 1/Aquifer

Stratum/Aquifer Name : Los Negros Formation

Description : The Los Negros Formation, which trends eastwar d across the study area, consists predominantly of numerous layers of massive, basaltic tuff and some basalt flow breccia and lapilli tuff [Ref. 29, pp. 8, 14]. The formation is mostly dark-greenish-gray to dark-greenish-black in fre sh exposures, and it typically weathers to light-olive-green; globular masses of basalt are randomly scattered throughout the tu ff [Ref. 29, p. 14; 31, p. 1]. The Los Negros Formation has a maximum thickness of 1,000 meters (approximately 3,300 feet) [Ref. 31, p. 1].

14GW-Observed Release

3.1 LIKELIHOOD OF RELEASE

3.1.1 Observed Release

Aquifer Being Evaluated: Bedrock aquifer (Los Negros Formation)

An observed release is documented for the Corozal Well site . Chemical analyses for ground water samples collected from the Comunidad Santana well in December 2010, Februa ry 2011, and March 2011 show the presence of PCE, as
shown below.

Direct Observation

The aquifer is not evaluated for obs erved release by direct observation.

Chemical Analysis

EPA collected three ground water samples from the Comuni dad Santana well in December 2010 and February 2011, and the results confirmed the presence of PCE at concentrations ranging from 63.5-120 μ g/L [Ref. 10, pp. 2-5; 11, pp. 2-3, 7, 10, 13-14, 29, 37, 46; 12, pp. 1, 4; 14, pp. 1, 6, 12]. Samples collected from background wells showed non-detects for PCE [Ref. 13, pp. 1, 4, 25-28; 14, pp. 1, 4, 24]. Additional samples collected by EPA in March 2011 indicate that the ground water contamination is currently isolated at the Co munidad Santana well, whereas PCE was not detected in several other potable and non-potable wells in the region [Ref . 22, pp. 19-24, 39, 73-74, 79-81; 23, pp. 3, 5, 13, 19, 21- 22; 24, pp. 2-8, 13, 17-26, 31-32; 25, pp. 2, 23, 31-32, 59-60]. The location of each well sampled for chemical analysis is depicted on Reference 23, p. 13.

Background Concentrations

Well Location Elevation (ft AMSL) Casing Depth (ft bgs) Well Depth (ft bgs) Screened*

Interval (ft AMSL) Sample

Station ID Sample

Date Reference(s)

GW-MW02-

00-001 01/25/2011

GW-MW02-

00-002 01/25/2011

1371-GW02 03/29/2011 Nieves Sanchez (active) 1,312 22 496 1,290-816

1371-GW08 03/29/2011 4, p. 1; 10, p. 7; 11, pp. 3, 10, 37; 22, p. 23; 23, pp. 5, 21-22; 28, p. 5

1371-GW06 03/21/2011 Well No. 3 (inactive Nieves Sanchez well) 1,330 Unknown 44 1,330- 1,286 1371-GW07 03/21/2011 4, p. 1; 22, pp. 19-20; 23, pp. 5, 19

Sector La Riviera (a.k.a., Don Antonio) 1,240 67.8 298 1,172.2-

942 1371-GW03 03/29/2011 4, p. 1; 22, p. 22; 23, pp. 5, 22; 28, p. 5 Up Construction Corp. 1,375 Unknown Unknown Unknown 1371-GW04 03/29/2011 4, p. 1; 22, pp. 22-23; 23, pp. 5, 22

RO Rental Equipment, Inc. (a.k.a., Ortega) 1,375 25.2 347 1,349.8- 1,028 1371-GW05 03/29/2011 4, p. 1; 22, p. 23; 23, pp. 5, 22; 28, p. 5
ft AMSL = feet above mean sea level ft bgs = feet below ground surface * = Screened or open

15GW-Observed Release

Background Concentrations (continued)

Sample ID Hazardous Substance Conc. ( μ g/L) Detection/ Quantitation Limit* ( μ g/L) Reference(s)

GW-MW02-00-001 PCE ND 5

GW-MW02-00-002 PCE ND 5 11, p. 37; 13, pp. 4, 25-28, 42-46

1371-GW02 PCE ND 5

1371-GW08 PCE ND 5 23, pp. 21-22; 24, pp. 4, 13, 19-20, 31-32,

37-41

1371-GW06 PCE ND 5

1371-GW07 PCE ND 5 23, p. 19; 25, pp. 2, 23, 31-32, 59-60, 69-

73

1371-GW03 PCE ND 5 23, p. 22; 24, pp. 5, 21-22, 37-41

1371-GW04 PCE ND 5 23, p. 22; 24, pp. 7, 23-24, 37-41

1371-GW05 PCE ND 5 23, p. 22; 24, pp. 8, 25-26, 37-41

*Available detection/quantitation limits are as follows:

• December 2010, January 2011, and March 2011: RDL/QL or Quantitation Limit [Ref. 12, p. 4; 13, p. 4; 24, pp. 2, 4-5, 7-8, 13; 25, pp. 2, 23]; equivalent to SQL described in the HRS [Ref. 1, p. 51589]

• February 2011: Minimum Detection Limit [Ref. 14, pp. 6, 12, 24]; equivalent to detection limit (DL) described in the HRS for non-CLP sample analyses [Ref. 1, p. 51589]

Contaminated Samples

Well
Location Elevation (ft AMSL) Casing Depth (ft bgs) Well Depth (ft bgs) Screened*

Interval (ft AMSL) Sample

Station ID Sample

Date Reference(s)

1622998 11/12/2010

1628221 11/23/2010

GW-MW01-

050-01 12/16/2010

GW-MW01-

100-01 12/16/2010

GW-MW01-

100-02 12/16/2010

GW-MW01-

140-01 02/09/2011

GW-MW01-

140-02 02/09/2011 Comunidad

Santana 1,215 14.2 159 1,200.8- 1,056

1371-GW01 03/29/2011 4, p. 1; 8, pp. 8, 12; 10, pp. 2-3, 10; 11, pp. 3, 10, 29, 46, 51; 23, p. 21; 28, p. 5

ft AMSL = feet above mean sea level ft bgs = feet below ground surface * = Screened or open

16GW-Observed Release

Contaminated Samples (continued)

Sample ID Hazardous Substance Conc. ( μ g/L) Detection/ Quantitation Limit* ( μ g/L) Reference(s)

1622998 PCE 17.0 0.5

1628221 PCE 92.5 5.0 8, pp. 8, 12

GW-MW01-050-01 PCE 110 5

GW-MW01-100-01 PCE 120 5

GW-MW01-100-02 PCE 120 5 11, p. 29; 12, pp. 1,

4-13

GW-MW01-140-01 PCE 63.5 0.3

GW-MW01-140-02 PCE 70.0 0.3 11, p 46; 14, pp 6, 12

1371-GW01 PCE 39 5 23, p. 21; 24, pp. 2, 17-18, 37-41

*Available detection/quantitation limits are as follows:

• November 2010: Method Detection Limit [Ref. 8, pp. 8, 12]; equivalent to detection limit (DL) described in the HRS for non-CLP sample analyses [Ref. 1, p. 51589]

• December 2010, January 2011, and March 2011: RDL/QL or Quantitation Limit [Ref. 12, p. 4; 13, p. 4; 24, pp. 2, 4-5, 7-8, 13; 25, pp. 2, 23]; equivalent to SQL described in the HRS [Ref. 1, p. 51589]

• February 2011: Minimum Detection Limit [Ref. 14, pp. 6, 12, 24]; equivalent to DL described in the HRS for non-CLP sample analyses [Ref. 1, p. 51589]

17GW-Observed Release

Attribution:

EPA has not yet identified a source of the ground water cont aminants in the Comunidad Santana well. PCE does not occur naturally, and non-detect concentrations in nearby wells show that the compound is not ubiquitous in the area (see Section 3.1.1) [Ref. 12, pp. 1-13; 13, pp. 1-46; 14, pp. 1-36; 16, pp. 1-2]. PCE is a man-made chlorinated solvent that is commonly used in commercial/industrial operations such as dry cleaning and metal degreasing [Ref. 16, pp. 1-2].

Since discovery of the contamination, EPA and PREQB ha ve attempted to identify the source(s) of observed ground
water contamination. Reconnaissance efforts indicate that there are few commercial/industrial operations in the area surrounding the contaminated well, and there is no direct evid ence of PCE use at any nearby facilities [Ref. 19, pp. 4-6, 9-10, 14-16, 19: 22, pp. 3-9]. Aqueous samples collected by PREQB from the two closest known commercial/industrial facilities (ERC Manufacturing [ERC] and RO Rental Equipment, Inc. [RO]) did not indicate the presence of PCE [Ref. 9, pp. 2-3, 13-18; 19, pp. 4-5]. Expanded EPA site discovery, reconnaissance, and sampling efforts (i.e., Expanded Site Inspection [ESI] efforts) from December 2010 to March 2011 di d not identify the source(s) of contamination, as
described below.

In December 2010 and February 2011, EPA conducted reconnaissan ce efforts in the vicinity of the Comunidad Santana well to identify possible sources of ground water contamination [Ref. 19, pp. 4-6, 9-10, 14-16, 19; 22, pp. 3-7]. EPA also performed an environmental database search and conducted inte rviews to document site histories and regulatory status of possible source facilities [Ref. 17, pp. 1-14; 19, pp. 4-9; 22, pp. 3-7]. The environmental database search did not identify any known possible source facilities within 1 mile of the site, but did identify 20 “orphan” sites that could not be mapped due to poor or inadequate address information [Ref. 17, pp. 1-14]. Available address information indicates that these facilities are all located along Roads 152, 159, or 164, none of wh ich are located within 1 mile of the Comunidad Santana well [Figure 1; Ref. 4, p. 1; 17, pp. 7-8, 14]. For inst ance, the address for Corozal Coin & Dry Cleaners (Road 159 kilometer 13.4) is located on the outskirts of the Corozal Pueb lo approximately 4 miles northwest of the well [Ref. 4, p. 1; 17, p. 14].

From March 16-31, 2011, EPA collected a total of 8 ground wa ter samples, 9 surface water samples, and 41 soil samples for VOC analysis from the Corozal Well study area [Ref. 23, pp. 3-13]. Ground water samples were collected from the Comunidad Santana well and nearby potable and non-potable wells, and surface water samples were collected from the unnamed stream that flows past the Comunidad Santana well [Ref. 22, pp. 9-12, 19-24, 39, 61-64, 73-74, 79-81; 23, pp. 3, 5-6, 13, 15, 19, 21-22]. EPA collected 15 surface and subs urface soil samples manually fro m hillsides upstream of the contaminated well, including the property of a cabinetmaker [R ef. 22, pp. 13-18, 66-72; 23, pp. 3, 6-7, 13, 17]. Due to their upstream location in the same watershed as the contaminated well, the ERC and RO facilities were investigated using direct-push drilling techniques to collect surface and subsurface soil samples; EPA collected 13 direct-push soil samples from the ERC facility and 13 direct-push soil sample s from the RO facility, as well as a ground water sample from an industrial well at the RO facility [Ref. 22, pp. 21- 55, 75-88; 23, pp. 3, 5, 7-9, 13, 21-22, 24-27]. One ground water sample was additionally collected from the Up Constructi on Corp. facility well used for truck washing and sanitary purposes [Ref. 19, pp. 9, 19; 22, pp. 7, 22-23; 23, pp. 3-5, 13, 22]. The locations of these soil and ground water samples are presented on Reference 23, p. 13. Additional discussion of these facilities and sampling efforts is provided below.

The analytical results for the March 2011 sampling effort indicate that PCE is present only in the Comunidad Santana well and surface water samples in its immediate vicinity, but not in soils uphill of the well and stream, in soils at either of the two industrial facilities, or in any other ground water wells in the area [Ref. 24, pp. 2-8, 13, 17-26, 31-32; 25, pp. 2- 16, 23, 31-50, 59-60; 26, pp. 2-20, 24-53; 27, pp. 2-22, 26-63, 70-78, 84-97]. PCE wa s not detected in the several other potable and non-potable wells in the region, including two ot her community drinking water supply wells located within approximately 0.3 mile of the contaminated well [Ref. 23, pp. 3, 5, 13, 21-22; 24, pp. 4-5, 13, 19-22, 31-32]. In summary, the results of the March 2011 EPA sampling efforts indicate that the ground water contamination is currently isolated to
contamination at the Comunidad Santana well.

Based on these considerations, there is not sufficient ev idence to attribute the ground water contamination in the Comunidad Santana well specifically to sources at any nearby facilities; therefore, there is no identified source(s) of
contamination.

18The facilities sampled by EPA in March 2011 are described below:

1. ERC Manufacturing

The ERC Manufacturing facility is located approximately 0.47 mi le east-southeast of the Comunidad Santana well, and is an HVAC duct manufacturer; it purchases sheet metal and sh apes it into HVAC ducts. Company representative stated that they do not use degreasers, and there was no evidence of solvent use during the EPA investigation. There is a septic tank located on the property [Ref. 19, pp. 5, 15; 23, p. 13]. EPA observed good housekeeping and did not see any spills [Ref. 19, pp. 4-5]. On March 29-30, 2011, EPA completed four test boreholes at the ERC facility. Direct-push refusal at the bedrock surface occurred at depths of 19 to 25 feet below ground surface. Ground water was not encountered in any
boreholes. EPA collected four surface soil and nine subs urface soil samples for TCL VOC analysis through the EPA Contract Laboratory Program (CLP) [Ref. 22, pp. 30-34, 39- 48, 77-78, 82; 23, pp. 1-3, 7-8, 21, 24]. PCE was not detected in any of the samples collected from the ERC Manufacturing facility [R ef. 27, pp. 8-22, 26-37].

2. RO Rental Equipment

Located approximately 0.26 mile east of the Comunidad Santan a well, RO Rental Equipment is a construction contractor; it operates and maintains heavy machinery. The company performs truck maintenance and truck washing at this location. There is a septic tank located on the property [Ref. 23, p. 13; 22, pp. 6, 38]. On March 30-31, 2011, EPA completed five test boreholes at the RO facility. Direct-push refusal at the bedrock surface occurred at depths of 6 to 35 feet below ground surface. Ground water was not encountered in any borehol es. EPA collected five surface soil and eight subsurface soil samples for TCL VOC analysis through the EPA CLP [Ref . 22, pp 40, 49-55, 85-88; 23, pp. 1-3, 8-9, 24-27]. PCE was not detected in any of the samples collected from the RO Rental Equipment facility [Ref. 27, pp. 2-8, 38-63, 70-78, 84-97].

3. Up Construction Corp.

The Up Construction Corp. facility is located on Road 811, approximately 0.75 mile north-northeast of the Comunidad Santana well [Ref. 23, p. 13]. The facility consists of offices and equipment storage, and a well that is used for truck washing and sanitary purposes but not for drinking water s upply [Ref. 19, pp. 9, 19; 22, pp. 7, 22-23]. On March 29, 2011, EPA collected a groundwater sample from the well for TCL VOC analysis through the EPA CLP [Ref. 22, pp. 22- 23; 23, pp. 3-5, 13, 22]. PCE was not detected in the sample collected at the Up Construction Corp. facility [Ref. 24, pp. 7, 23-24].

Hazardous Substances Released:

Tetrachloroethylene (PCE) CAS No. 000127-18-4

Based on the establishment of an observed release to the Comunidad Santana Well as shown above, a value of 550 is assigned to the ground water observed rel ease factor value [Ref. 1, p. 51595].

================================================================================== Ground Water Observed Release Fact or Value: 550 [Ref. 1, p. 51595]

19GW-Waste Characteristics

3.2 WASTE CHARACTERISTICS

3.2.1 Toxicity/Mobility

Hazardous Substance Source

Numbers Toxicity

Factor Value Mobility

Factor Value Toxicity/ Mobility Reference

Tetrachloroethylene 1, OR 100 1.0 100 2, p. 4

OR = Observed Release

3.2.2 Hazardous Waste Quantity

Source Number Source Hazardous Waste Quantity (HWQ) Value (Section 2.4.2.1.5) Is source hazardous constituent quantity data complete? (yes/no)

1 >0 No

Sum of Values: 1 (rounded to 1 as specified in HRS Section 2.4.2.2)

The sum corresponds to a hazardous waste quantity factor va lue of 1 in Table 2-6 of the HRS [Ref. 1, p. 51591]. However, based on the fact that targets are subject to Level I concentrations (see S ection 3.3.2.3), and hazardous constituent quantity is not adequately determined, a hazardous waste quantity factor value of 100 is assigned if it is greater than the hazardous waste quantity value from Ta ble 2-6 (i.e., 1) [Ref. 1, pp 51591-51592]. Therefore, a hazardous waste quantity factor value of 100 is assigne d for the ground water pathway [Ref. 1, pp 51591-51592].

3.2.3 Waste Characteristics Factor Category Value

PCE corresponds to the toxicity/mobility factor value of 100, as shown previously (see Section 3.2.1).

Toxicity/Mobility Factor Value (100) x Hazardous Waste Quantity Factor Value (100): 1 x 10 4

The product (1 x 10 4 ) corresponds to a Waste Characteristics Factor Cate gory Value of 10 in Table 2-7 of the HRS [Ref. 1, p. 51592].

================================================================================== Hazardous Waste Quantity Factor Value: 100 Waste Characteristics Factor Category Value: 10

20GW-Targets

3.3 TARGETS

The Comunidad Santana well is the sole source of drinking wa ter for a community and serves a population of more than 200 people; according to available information, there are no other wells or surface water intakes contributing to the Comunidad Santana system [Ref. 6, p. 1; 7, pp. 2-12, 14-18]. The recorded population of 217 people is subject to Level I concentrations, as presented below:

Well Distance

from Source (mi.)* Population Level I Conc. (Y/N)** Level II
Conc. (Y/N)** Potential Contam. (Y/N) Reference(s)

Comunidad

Santana 0.0 217 Y N N 11, pp. 58-130

* Distance is measured from the center of the area of observed ground water contamination [Figure 1].

** Maximum Contaminant Level/Maximum Contaminant Level Goal (MCL/MCLG), Reference Dose Screen Concentration (RfD), and Cancer Risk Screen Concentration ( CRSC) were used as benchmarks to evaluate the level of contamination [Ref. 1, p. 51593]. Applicable benchmarks for the contaminants detected in the observed release, presented here in μ g/L for consistency with reported data, are as follows:

Substance MCL/MCLG RfD CRSC Reference(s)

PCE 5 360 1.6 2, p. 5

Level I Concentrations

Well Sample Substance Conc. ( μ g/L) Benchmark ( μ g/L) Reference(s)

1622998 17.0

1628221 92.5 2, p. 5; 8, pp. 8,

12 Comunidad

Santana

1371-GW01 PCE

39 1.6 (CRSC)

2, p. 5; 23, p. 21; 24, pp. 2, 17-18

21GW-Nearest Well/Population

3.3.1 Nearest Well

As identified in Section 3.3, the former Comunidad Santan a drinking water well is subject to Level I concentrations. Therefore, a nearest well factor value of 50 is assigned [Ref. 1, pp. 51602-51603].

================================================================================== Nearest Well Factor Value: 50

3.3.2 Population

3.3.2.2 Level I Concentrations

As identified in Section 3.3, the former Comunidad Santana dr inking water well is subject to Level I concentrations. The population assigned to the well is also explained in Section 3.3. The population subject to Level I concentrations is multiplied by 10 to calculate the Level I concentrations factor value [Ref. 1, p. 51603, Sec. 3.3.2.2].

Level I Well Population Reference(s)
Comunidad Santana 217 11, pp. 58-130

================================================================================== Population Served by Level I Wells: 217 Level I Con centrations Factor Value: 2,170 [Ref. 1, p 515603]

3.3.2.3 Level II Concentrations

The people served by the contaminated drinking water well (Comunidad Santana) are already counted under the Level I
concentrations factor. The Level II concentrations factor value is 0 because there are no other points of withdrawal subject to Level II concentrations [Ref. 1, p. 51603].

Level II Well Population Reference(s)
N/A N/A N/A

================================================================================== Population Served by Level II Wells: 0 Level II Concentrations Factor Value: 0

3.3.2.4 Potential Contamination

Due to the fact that the maximum score of 100.00 for the ground water pathway is achieved, potential contamination was
not evaluated.

================================================================================== Potential Contamination Factor Value: 0

2223 GW-Resources/Wellhead Protection Area

3.3.3 Resources

There is no documented resource use of ground water at the site [Ref. 7, pp. 1-12, 14-18]. Therefore, a resources factor value of 0 is assigned [Ref. 1, p. 51604].

================================================================================== Resources Factor Value: 0

3.3.4 Wellhead Protection Area

There are no designated wellhead protection areas at the site or within the target distance limit [Ref. 18]. Based on this information, a wellhead protection area factor value of 0 is assigned [Ref. 1, p. 51604].

================================================================================== Wellhead Protection Area Factor Value: 0