FOURTH FIVE-YEAR REVIEW REPORT VEGA AL TA SUPERFUND SITE

VEGA ALTA, PUERTO RICO

Prepared by

U.S. Environmental Protection Agency Region 2

New York, New York

September 2014

y: Date:

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Walter E. Mugdan, Director Emergency and Remedial Response Division

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Table of ContentsExecutive Summary ...................................................................................... iii

Five-Year Review Summary Form ............................................................................................ iv

Introduction....................................................................................................................................1

Site Chronology ..............................................................................................................................1

Background ....................................................................................................................................1

Physical Characteristics .... .............. .. ....... ........ .. .................. ......................... ...... .. ......... ...... .. .... 1

Site Geology/Hydrogeology ...... ......... ........ ... ..... ........... ...... ........ ......... .... .... ......... ...... ........ ........ 2

Land and Resource Use .............................. ..... ......... .... ...... ......... ... ... ...... .. .... ............ ..... ......... ... 1

History ofContamination .................................. ............................ ......................................... .... 1

Initial Response.. ........................ ......... .................. ............... .... .... .......... ........... .... ... .... ............... 2

Basis for Taking Action.............. ........... .................. ..... ................ ............... ............. .................. . 2

Remedial Actions ...........................................................................................................................3

Remedy Selection ... ....... .... .... ... ........... ........ .. ...... ........................... ....................... ........... ....... .... 3

Remedy Implementation ............. ....... ........ ..... ..... ........ ......... .... ...... ............... .... .... ......... ...... ....... 6

Progress Since Last Five-Year Review ........................................................................................8

Five-Year Review Process .............................................................................................................9

Administrative Components ....... ....... .................................................................... ...................... 9

Community Involvement ... ......... ....... .... ....... ......... ......................... ........................................... 10

Document Review .................... ............. .................. ....................... ................... ........ .... ........ .... 10

Data Review................................. ....... ........... ......................................................... .................. 10

Site Inspection ...... .. .... .. ............. .. ...... ....... .. ......... ........ .. ....... .......... ....................... .... ........ ...... .. 12

Institutional Controls Verification ............. ......... ......... ............ ...... ......... .............. .............. .. .... 12

Technical Assessment ..................................................................................................................12

Question A: Is the remedy functioning as intended by the decision documents? ............ ......... 12

Question B: Are the exposure assumptions, toxicity data, cleanup levels, and remedial action objectives used at the time ofthe remedy still valid? ...... ..... ........................... .... ........ ........ ..... 13

Question C: Has any other information come to light that could call into question the protectiveness ofthe remedy? .... ........... .... .. ...... .. ......... .... ....... ........................... ....................... 14

Issues, Recommendations and Follow-Up Actions ...................................................................14

Protectiveness Statement .............................................................................................................14

Next Review ..................................................................................................................................14

Appendix 1: Tables ......................................................................................................................15

Table 1 Chronology ofSite Events ...... ... ........ ..... ......... ............................ ...... .... .... .. ... .. ......... . 16

Table 2 Documents, Data, and Information Reviewed in Completing the Five-Year Review .. 18

Table 3 TCE Concentrations observed in multiport wells/zone monitored annually .... ... ........ 19

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Executive Summary

This is the fourth five-year review (FYR) for the Vega Alta Public Supply Wells Superfund Site located in Vega Alta, Puerto Rico. The purpose of this FYR is to review groundwater data collected in the past five years to determine if the remedy is and will continue to be protective of human health and the environment. The triggering action for this policy review was the completion of the third FYR for the Site on August 19, 2009.

The community drinking water is provided by a public water supply that meets appropriate Federal and State drinking water standards and there is no exposure to contaminated drinking water emanating from this Site. The results ofthis FYR demonstrate that the immediate threats from the Site have been addressed, the remedies are protective of public health and the environment, and the groundwater cleanup goals are expected to be achieved through continued treatment of the contaminated groundwater.

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Five-Year Review Summary Form

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SITE IDEN rl FIC.\TION

Site Name: Vega Alta Public Supply Wells Superfund Site

EPA ID: PRD 980763775

NPL Status: Final

Multiple OUs? Has the Site achieved construction completion? Yes Yes

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RE\'IE\\ STATL1S

Lead agency: EPAe]:

Author name (Federal or State Project Manager): Adalberto Bosque

Author affiliation: EPA

Review period: 8/19/2009 - 7/8/2014

Date of Site inspection: 3/31/2014

Type of review: Policy

Review number: 4

Triggering action date: 8/19/2009

Due date (five years after triggering action date): 8/19/2014

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Protectiveness Statement(s). '

Operable Unit: Protectiveness Determination: Addendum Due Date OU-1 Protective (ifapplicable):

Protectiveness Statement: The OU-1 remedy is protective ofhuman health and the environment.

Sitcwide Protcctivcnes~ Statement

Protectiveness Determination: Addendum Due Date (ifapplicable): Protective

Protectiveness Statement: The remedy is protective ofhuman health and t.'ie environment.

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Introduction

The purpose of a FYR is to evaluate the implementation and performance ofa remedy in order to determine if the remedy is and will continue to be protective ofhuman health and the environment and is functioning as intended by the decision documents. The methods, :findings, and conclusions ofreviews are documented in the FYR. In addition, FYR reports identify issues found during the review, if any, and document recommendations to address them.

This is the fourth FYR for the Vega Alta Public Supply Wells Superfund Site , located in Vega Alta, Puerto Rico. This FYR was conducted by the United States Environmental Protection Agency (EPA) Remedial Project Manager (RPM) Adalberto Bosque. The review was conducted pursuant to Section 12l(c) of the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), as amended, 42 U.S.C. §9601 et seq. and 40 CFR 300.430(f)(4)(ii), and in accordance with the Comprehensive Five-Year Review Guidance, OSWER Directive 9355.7­03B-P (June 2001). This report will become part of the Site file.

The triggering action for this policy review was the completion of the third FYR for the Site on August 19, 2009. A FYR is required at this Site due to the fact that the remedial action will not leave hazardous substances, pollutants or chemicals on Site above levels that allow for unlimited use and unrestricted exposure, but requires five or more years to complete.

The site consists of two Operable Units (OUs). The first operable unit (OU-1) addresses the groundwater contamination at the Site. The second operable unit (OU-2) addresses the sources(s) of the contamination. The soil remedy has been completed and allows for use without restriction and is not the subject ofthis FYR. As such, this review focuses on the OU-1 ongoing groundwater remedy

Site Chronology

Table 1 in the Appendix summarizes the Site-related events from discovery of contamination through the previous FYR for the Site.

Background

Physical Characteristics

The Site is located north of the town of Vega Alta in the municipality of Vega Alta, Puerto Rico (Figure 1). Vega Alta is a municipality ofabout 39,950 people (US Census Bureau 2010) located in the central part of the north coast of Puerto Rico, about 20 miles west of San Juan. The Site does not have specific boundaries; however, most of the data collection activities have been conducted over an area bounded by the Atlantic Ocean to the north and the U.S. Geological Survey (USGS) Vega Alta Quadrangle boundary to the south. The east and west boundaries correspond with longitudes W 66° 15' and W 66°23', respectively. This area is referred to as the Vega Alta Study Area. The Site was previously defined by EPA as the area that serves the public water

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supply well field in the municipality of Vega Alta, Puerto Rico, and includes the Puerto Rico Industrial Development Company (PRIDCO) Industrial Park (the "Industrial Park") and any area to which contamination has migrated. Activities have generally been conducted within a study area bounded by the Atlantic Ocean to the north, Highway 2 to the south, Rio Cibuco to the west, and Rio de la Plata to the east. The Industrial Park, which was the focus ofthe source investigation, is located within the Vega Alta Study Area along Highway 2.

Site Geology / Hydrogeology

The Vega Alta Site study area is part of the North Coast Limestone of Puerto Rico . The surface and subsurface geologic units in this area are Oligocene to Miocene age, sedimentary formations that consist primarily of limestone. These formations are overlain by semi-consolidated to unconsolidated Quaternary deposits. The dip ofthe limestone formations in the study area is about 2 to 4 degrees to the north. The areal distribution and detailed descriptions of these formations are presented on the USGS geologic map of the Vega Alta quadrangle. A significant feature of this area is the formation ofkarst landforms that has developed due to dissolution of the limestone by water.

An unconfined (or water-table) freshwater aquifer is present throughout the Vega Alta Study Area. At the center of the study area, this aquifer is as great as 350 feet thick. According to data obtained from the Puerto Rico Aqueduct and Sewer Authority (PRASA) and USGS files, approximately 6.78 billion gallons of water were extracted from the aquifer by public and private water supply wells in the study area in 1990. This water was pumped at an average rate ofabout 12,900 gallons per minute (gpm) or 18.5 million gallons per day (mgd).

Hydrogeologic units underlying the regional area consist ofan unconfined (or water-table) aquifer, an aquitard, and confined aquifer. The unconfined aquifer is composed primarily of the Aguada and Aymam6n Limestone, but it also occurs in some of the alluvial and blanket sand deposits. The primary groundwater flow through the limestone aquifer occurs within solutionally enlarged primary pores and solution channels. Water occurs in primary pores and in secondary pores formed by dissolution of the limestone. Because of the large size of these secondary pores and the extent to which they are interconnected, these solution features have a significant impact on groundwater flow.

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Figure 1 Site location and Monitoring Wells

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Groundwater withdrawal from wells in the north coast limestone aquifer serves as the primary source ofwater for drinking, agriculture, and industrial use in the Vega Alta Study Area. Prior to the 1960s and the large-scale development in the Vega Alta area, the principal discharge location for groundwater was probably the coastal plain. In 1983, approximately 76 percent ofgroundwater discharge was through pumping water supply wells. The remaining groundwater discharged either to the ocean or to rivers close to the coast. There is no evidence of cave conduits discharging groundwater in the coastal plain nor in the submarine outcrop of the aquifer.

Along the shores ofthe Atlantic Ocean in the coastal plain, the bottom ofthe unconfined freshwater aquifer is delineated by the saltwater interface. In the study area, the saltwater interface starts below the seabed and dips to the south where it terminates at the low-permeability claystones at the top of the Cibao Formation. A confined aquifer occurs below the upper member of the Cibao Formation. This upper member is a claystone with very low permeability that acts as an aquitard.

land and Resource Use

The Site includes the previously mentioned Industrial Park owned by the PRIDCO. A landfill operated by the municipality is located north of the Industrial Park. The area is underlain by an aquifer that is a source of drinking water for residents ofVega Alta and other communities.

Land use can be classified as agricultural, industrial, residential, commercial, and recreational. The main agricultural uses are pasture land, dairy farms, nurseries raising ornamental plants, and growing crops such as rice, bananas, coconuts, and lawn grasses. Various industries are present in the area. Several active quarries in the area use the Aguada and Aymamon Limestone for road and fill materials and for making cement The main residential areas are located in and around the town of Vega Alta, Regadera, Dorado, Vega Baja and Brefi.as. Some of the areas along the southern edge has been designated as a state forest and these areas are managed by the Department ofNatural Resources· (DNR).

The PRIDCO Industrial Park was the focus of the source investigation and is located within the Vega Alta Study Area along Highway 2. PRIDCO has sold and leased properties and buildings to industries for various manufacturing operations. Prior occupants include: General Electric Pilot Devices, Inc. and General Electric Controls, Inc., which merged to form Caribe General Electric Products, Inc. (Caribe GE), Motorola Telcarro de Puerto Rico, Inc. (Motorola), Harman Automotive Puerto Rico, Inc. (Harman), and Remington Rand, to which Unisys Corporation (Unisys) is the corporate successor.

Vega Alta is a municipality of about 39,950 people (U.S. Census Bureau 2010) located in the central part of the north coast of Puerto Rico, about 20 miles west of San Juan. Groundwater is the primary source of water for the public water supply system, as well as for other private (industrial, commercial and agricultural) users. The Vega Alta well field and wells of the nearby municipalities ofVega Baja and Dorado have extracted approximately 18.5 mgd ofwater from the unconfined limestone aquifer.

History of Contamination

The Vega Alta municipal well field became a concern ofthe EPA in June 1983 after the discovery of trichloroethene (TCE) in a groundwater sample collected by the USGS from a public water supply well known as the Ponderosa Well. PRASA shut down the Ponderosa Well in the same

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month. In August 1983, PRASA ceased pumping the supply well GE-1. In June 1983, PRASA constructed supply well Bajura 5(3) (also referred to as either Bajura 3 or Bajura 5). Public water­supply wells Bajura 5(3), Bajura 1, and GE-2 were subsequently shut down in early 1989 after PRASA constructed a pipeline between the Vega Alta distribution system and the Maguayo well field. PRASA completed two new supply wells, Maguayo 6 and 7, in October 1988 and November 1988, respectively.

The Vega Alta Site was listed on the Superfund National Priorities List (NPL) on September 1, 1984.

Initial Response

In September 1983, EPA contracted with NUS Corporation (NUS) to perform the OU-1 Remedial Investigation and Feasibility Study (RI/FS) at the Site to determine the nature and extent of groundwater contamination. NUS, with cooperation from the USGS, conducted a field investigation from April 1984 to March 1985. The investigations were documented in an RI Report. Using the RI data, NUS conducted a Feasibility Study and recommended a groundwater remedy be selected.

Basis for Taking Action

The Remedial Investigation for OU-1 (groundwater) was performed from April 1984 to March 1985. The objectives ofthe RI were to characterize the hydro geologic system, determine the extent and type of hazardous substances in groundwater, make a preliminary assessment of potential contamination sources, and evaluate the migration potential of contaminants from the ground surface to the water table.

As part of the OU-1 RI, groundwater analyses were performed on 168 samples from 23 wells. Volatile Organic Compounds (VOCs) were identified as chemicals of concern that posed a potential public health risk. Analyses ofthe water distribution system indicated that the voe most frequently detected and with the highest concentrations was TCE. Other frequently detected compounds were tetrachloroethene, 1,1, I-trichloroethane, 1,1-dichloroethene, and 1,2­dichloroethene. These results led to the issuance of the OU-1 Record of Decision in 1987 (1987 ROD), discussed in detail below.

While the implementation of OU-1 was proceeding, on September 27, 1990, EPA issued a Unilateral Administrative Order, Index No. II-CERCLA-00301 (1990 Order) to a group of potentially responsible parties (PRPs) which required them to conduct an RI/FS for OU-2 at the Site to identify contaminant source areas. Based on the results of the RI and FS Reports, and after careful consideration ofall reasonable alternatives, EPA issued a ROD for OU-2 (OU-2 ROD) on September 30, 1997.

The baseline human health risk assessment for the Site found ingestion ofgroundwater by future residents had a total cancer risk for children of 2.6 x 10-3 (2.6 in 1,000) and for adults was 1.2 x 10-3 (1.2 in 1,000) and these risks exceed the risk range established under the National Oil and Hazardous Substances Contingency Plan. The primary chemicals contributing to this risk included 1,1-dichloroethene, ethylene dibromide, TCE, arsenic and beryllium. The cancer risks from inhalation while showering for the future Site adult resident was 3. 7 x 104 and the main chemicals contributing to the risks were 1,1-dichloroethene and TCE.

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For non-cancer health effects, the Hazard Index (HI) for adults and children from ingestion of contaminated groundwater were 9.4 and 22, respectively. The non-cancer HI exceeded the goal of protection of an HI = 1. The main chemicals contributing to this risk were TeE and arsenic.

Groundwater was found to pose an unacceptable cancer risk to human health through ingestion for future Site workers and employees. The ingestion route showed a cancer risk for Site workers/employees of 7.8 x 10-4 (7.8 in 10,000). This risk exceeds the upper-bound of the risk range. The chemicals contributing to this risk were: 1,1-dichloroethene, ethylene dibromide, and arsenic. The HI for potential future Site workers/employees from ingestion of groundwater was 3.4, exceeding the goal of protection of an HI = 1. The chemical contributing to the hazard was TeE.

Arsenic was retained as a chemical of concern since it is a known human carcinogen and contributed significantly to the risk as outlined in the Risk Assessment Guidance for Superfund. The risk assessment identified that this chemical was found at concentrations below the MeL and, consequently, was not addressed in the Feasibility Study. The risks and hazards posed by the other metals did not exceed EP A's risk values and their inclusion did not impact the risk assessment. The risks from TeE and other VOes still exceeded EP A's acceptable risk range for both cancer and non-cancer endpoints, supporting the conclusions that further remediation at the Site was warranted.

Based on the existing chemical-analytical data base and hydrogeological conditions no adverse environmental impacts are anticipated as a result of contaminant migration from the Vega Alta Site as indicated in the RODs. EPA is not aware of a specific assessment of environmentally sensitive areas; however, Site-related voes would be unlikely to encounter environmentally sensitive areas, because the water table is well below the base ofsurface water features within the area of groundwater monitoring. The source area, as it pertains to voes in groundwater related to the Site, is located in the Vega Alta Industrial Park. Dissolved VOes in groundwater downgradient from the source area are well below the surface. There are unlikely to be environmentally sensitive areas in the industrial park or at water table depth.

Remedial Actions

Remedy Selection

Remedy Selection for OU-1 (Groundwater)

A. Record ofDecision for OU-1

On September 29, 1987, EPA issued a ROD (1987 ROD) selecting a remedial action for the groundwater contamination. The remedial action objectives for OU-I were: to reduce contamination in groundwater; to protect uncontaminated groundwater for present/future use; and to reduce contaminant levels at the tap to prevent unacceptable human exposure. The major components of the selected remedy were the following:

• Treatment of PRASA wells GE-1, GE-2, and Bajura 3 by individual treatment systems consisting of scaling pretreatment, air stripping and possibly activated carbon. The specifics of the treatment system were to be determined during the Remedial Design.

• Discharge of treated effluent into the PRASA distribution system for public use.

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• Treatment ofPonderosa Well by scaling pretreatment and air stripping. • Discharge of treated effluent from the Ponderosa Well to Honda Creek. • Connection of the users of Monterrey 2 and G&M Cash and Carry private wells to the

PRASA distribution system. • Initiation of an RI/FS to fully assess and evaluate the source(s) ofVOC contamination at

the Site.

On September 30, 1988, EPA issued Administrative Order Index No. II-CERCLA-80217 (1988 Order) to Caribe GE, Motorola, Harman, West, and PRIDCO requiring them to implement the 1987ROD.

B. 1989 Explanation of Significant Differences

The OU-1 remedy was modified by an Explanation of Significant Differences (1989 ESD) issued by EPA on March 22, 1989. The 1989 ESD required surface discharge ofall treated water, instead ofdischarge to the PRASA water supply distribution system. This aspect ofthe ROD was changed in response to a request from the Puerto Rico Environmental Quality Board (EQB). The 1988 Order was superseded by an administrative order issued to the same Respondents on March 2~ 1989, Administrative Order Index No. II-CERCLA-90302 (the 1989 Order). The 1989 Order required implementation of the 1987 ROD, as amended by the 1989 ESD.

C. 1994 Explanation of Significant Differences

On August 30, 1994, EPA issued a second ESD which modified the remedy authorized by the 1987 ROD and the 1989 ESD. On the same date, EPA issued an Amended Order (1994 Order) which required the Respondents to implement the modified remedy. Groundwater investigations at the Site associated with the OU-2 RI/FS showed that, in the six years following the issuance of the 1987 ROD, the plume of groundwater contamination had migrated downgradient of three of the extraction wells (GE-1, GE-2, and Bajura 3) selected in the ROD, and that these wells were no longer capable of effectively remediating the Vega Alta aquifer. The remedial action for OU-1, as amended by the ESDs, included the following:

• Pumping of groundwater from the Ponderosa Well, and from a new extraction well (referred to as Well A) to be constructed at the leading downgradient edge of the contaminant plume, which was approximately 4,000 feet north ofthe Ponderosa Well. The 1994 ESD projected that Well A would withdraw approximately 700 gpm.

• Treatment of the water pumped from the Ponderosa Well and Well A. Such treatment was to be accomplished by construction of a treatment system near the Ponderosa Well and another treatment system near Well A.

• Construction of systems for discharging the treated groundwater to surface water (Honda Creek or the swamps north of the plume of groundwater contamination) or for reintroducing the treated groundwater into the PRASA water distribution system. The treated groundwater would be discharged to surface water unless and until EPA and the Commonwealth of Puerto Rico determined that the treated water should be discharged to the PRASA distribution system.

D. Migration of the Contaminant Plume

In January 1996, the Puerto Rico Department ofHealth informed PRASA that the Maguayo 3 Well (iocated north of the Industrial Park) exceeded the Safe Drinking Water Act Maximum Contaminant Level (MCL) standard for TCE of 5 micrograms per liter (ugll), the primary

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contaminant of concern at the Site. In late 1996, EPA requested that Carib GE and Unisys undertake a supplemental groundwater survey in the vicinity of the Site. This survey of private wells was conducted in the first quarter of 1997. The samples showed that Monterrey Well 1 (located north ofthe Industrial Park and utilized by the Monterrey Farm) also exceeded the MCL standard for TCE. These results indicated that the contaminant plume was continuing to migrate in a northeasterly direction. PRASA also informed EPA of its plans to install a series of large­yield water supply wells a few miles east of the Site, which raised concerns about the continued migration ofthe plume. The new water supply system, known as the Early Water Initiative (EWI), was projected to withdraw as much as 12 mgd from the upper aquifer, in addition to another 10 mgd from the Rio de la Plata (lower aquifer). The EWI was predicted to increase the groundwater flow gradient to the east, significantly reducing the radius of influence (and therefore, the area of capture) of the proposed new extraction well.

E. 1997 Explanation of Significant Differences

EPA further modified the remedy in an ESD dated December 5, 1997 (1997 ESD). EPA made this change to the selected remedy in response to new information discussed above and because additional investigations at the Site during the OU-2 RI/FS enabled EPA to pinpoint more precisely an area of high contaminant concentration within the plume and locate the remaining primary source of contamination. At the same time, EPA amended the 1994 Order. The remedial action for OU-1, as amended by the 1997 ESD, included the following:

•. Pumping and treatment ofgroundwater from a well or a series ofwells which will be known as the Source Area Well(s) (SAW(s)), rather than from "Well A" called for by the 1994 ESD. The SAW(s) would be located in close proximity to the source of contamination, which had been determined to be within the Industrial Park. Once the SAW(s) were fully operational, the Ponderosa Well could be taken out of service if determined by EPA that its continued operation would not be beneficial or would adversely affect the efficiency of the SAW(s).

• Pumping and treatment of water from the SAW(s) at an estimated rate of 300 gpm. The actual pumping rate to be determined during the installation, start-up, and operation of the new extraction well(s). The treated groundwater would be discharged to Honda Creek if not needed for consumption and household use.

• Implementation of a monitoring program to evaluate the performance of the Ponderosa Well including the continuity of its operations and capture zone evaluation.

• Implementation of a long-term monitoring program to evaluate groundwater voe concentrations, natural attenuation ofVOCs in groundwater, and the capture zone(s) ofthe extraction wells being used. Further refinement of groundwater modeling and collecting of additional data in order to identify appropriate remedial measures, if any, to address the downgradient portion of the VOC plume which will not be captured by the SA W(s) or the Ponderosa Well.

F. Remedy Selection for OU-2 (Source Area)

While the implementation of OU-:1 was proceeding, on September 27, 1990, EPA issued a Unilateral Administrative Order, Index No. II-CERCLA-00301 (OU-2 Order) to the PRPs, which required them to conduct an RI/FS for OU-2 at the site to identify contaminant source areas. Based on the results of the RI and FS Reports, and after careful consideration of all reasonable alternatives, EPA issued the OU-2 ROD on September 30, 1997. The remedial objectives for OU­2 were to reduce the concentrations ofVOCs in the areas of the Site known to contain the highest concentration~ in the soil matrix, to the extent technologically feasible, reducing the potential risk

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to human health through exposure to groundwater by reducing the leaching of voes from these soil areas, and, thereby, enhancing the existing OU-1 groundwater remedy. The major components of the remedy were the following:

• Operation of a mobile or permanent soil vapor extraction (SVE) treatment system(s) to remove voes from the contaminated soils until no more voes can be effectively removed. Soil vapors will be treated, ifnecessary, before being emitted to the atmosphere.

• Implementation of a system monitoring program for soil vapor collection and analysis before and after air treatment, iftreatment is determined to be necessary.

• Appropriate environmental monitoring to ensure effectiveness of the remedy.

Remedy Implementation

A. Remedy Implementation for OU-1

The Ponderosa Well Treatment System was completed on December 22, 1993, and groundwater treatment began in July 1994. The Ponderosa System has been shut down since November 16, 2004, with EPA approval. The door to the treatment building is locked and building security is periodically inspected by the PRP's consultant. In an October 31, 2011, letter, EPA provided its approval of the PRP's March 19, 2010, Decommissioning and Demolition Work Plan. In September 2013, the PRPs submitted a permit application for decommissioning of the Ponderosa well to the DNR for review and approval. The approved permit was received in December 2013, and the PRPs have initiated coordination for the decommissioning of the Ponderosa well.

On August 30, 1994, and again on December 5, 1997, EPA modified the remedy authorized by the 1987 OU-1 ROD and 1989 ESD. The specifics of these modifications are discussed above. The Remedial Design Report for the SAWs (selected by the 1997 ESD) was approved in July 2000. The SAW s Groundwater Remedial Action Work Plan was approved in January 2001. Remedial action construction activities were initiated in July 2001. Construction ofthe air stripper unit was completed in November 2001, and EPA' s inspection ofthe unit was conducted in December 2001. Based upon the results of the inspection by EPA, EPA issued a Preliminary Close-Out Report in March 2003 finding that construction for the entire Site was completed.

The users of the G&M Cash and Carry well were connected to the PRASA distribution system on October 28, 1993. The users of the Monterrey 2 Well were not connected to the PRASA distribution system because they began using t.lie Monterrey 1 Well, which is located on their property. Pursuant to a private agreement, the PRPs (Caribe GE and Unisys) have been supplying the users of the Monterrey 2 Well with potable water to meet their current drinking water needs since early 1997.

In December 2002, the SAW Treatment System was placed into continuous operation to hydraulically capture the source area groundwater and remove VOCs. In its August 2004 FYR, EPA documented its approval of the temporary shutdown of the Ponderosa Treatment System, in favor of continued remediation by the SAW Treatment System. Pumping from the Ponderosa Treatment System ceased in November 2004.

The purpose of the SAW Treatment System is to capture and cut off the more highly concentrated portion of the plume emanating from the source area, which is in the immediate vicinity of the GE Controls building. The Source Area remedy design included the selection of two extraction well locations (SA W-1 and SA W-2) to provide the flexibility to pump one or both wells. The wells are located directly downgradient from the source area to maximize capture and remediation at optimum flow rates. The system has been operating continuously since its startup in December

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2002, with occasional shutdowns resulting from regional power outages and necessary system maintenance/repairs.

The SAW Treatment System has generally been operated utilizing one well, primarily SAW-1. The average pumping rate from SAW-1 ranged from approximately 135 to 165 gpm, and from approximately 47 to 54 gpm from SAW-2. Fluctuation in pumping rate results from changes in groundwater level, which is primarily a function of precipitation. A water level displacement analysis conducted by BBL in April 2004 confirmed that the SAW System, operating at 112 gpm, produces a hydraulic capture zone that extends beyond the limits of the VOC Source Area, confirming attainment of hydraulic control of the VOC Source Area. In addition, data observed in monitoring well M22, located in the Source Area, illustrates the effectiveness of the SAW Treatment System in remediation of the Source Area (Figure 2). Since there was a 30 percent decrease in Total VOC concentration during the first year of operation in M22. A review of monitoring data from 2000 to 2013 shows the maximum observed total voe concentrations in well M22 have decreased from 1,745 ug/L (zone 8) to 181.0 ug/L (zone 6). v•----­v...-. ..- ­

r-voc:c;-­-llU-'-1.-'l

3000

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! 2500 g li ~ 20!l0t--~~~~--'l-tt-~--H-t--t--~~~~~~~~~~~~~ ! 8 > 1500

!

500

•MSt. _, .. ___., __._

Figure 2 Well M22 trend line for Total Volatile Organic Compounds

The trend in sampling data collected from M-22 since 2002 has been downward and confirms the remedial action has been effective to date. The multi-level monitoring well is in close proximity to the SAW Treatment System placed into operation in 2002. The purpose of the SAW Treatment System is to capture and cut off the more highly concentrated portion of the plume emanating from the source area. Continued operation of this system and monitoring of M-22 is recommended. A source area investigation is suggested in the future if continued operation of the SAW Treatment System reaches asymptotic levels and there is a cost benefit to potential source removal over continued SAW Treatment System operations.

As of December 30, 2013, the SAW Treatment System has treated approximately 687 million gallons of groundwater since startup in December 2002. The SAW Treatment System has

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achieved, during this period of time, a total voe mass removal of approximately 1,080 pounds. As of November 16, 2004, the date when the Ponderosa System was temporarily shut off, the Ponderosa System had treated approximately 1.9 billion gallons of groundwater and removed approximately 600 pounds of VOCs. At the time that the Ponderosa System was shut down, individual compound concentrations in its pre-treated groundwater bad fallen below the relevant chemical-specific federal MCLs. . . · ·

B. System Operations/Operation ~d Maintenance fo:r: OU-1

The necessary O&M activities for the SAWs treatment systems currently include:

• Continued operation, maintenance, and monitoring of the groundwater extraction and treatment systems;

• Continued security and maintenance inspection of the Ponderosa · Groundwater Treatment System pending EPA approval ofpermanent shutdown; and

• Continued discharge of the treated water to Honda Creek; if such treated water is not needed for consumption arid household use .

• These O&M activities are currently being performed by the PRPs Carib GE and Unisys, with EPA oversight. Recent Site visits indicate that such activities are being conducted in accordance with the approved plans, specifications and protocols.

C. Remedy Implementation for OU-2

The SVE systems were operated from December 2002 until October 1, 2008 in co1I1pliance with the requirement of the EPA-approved SVE Operation and Maintenance Manual (LBG, November

.2001), the 1997 ROD and the OU-2 Order. Closure testing verified that the objectives for the operations of the SVE system were met.

EPA's approval of the Draft Revised Remedial Action Report and the recommendation to permanently shut down the SVE systems was granted· in ,a letter dated September 25, 2008. The SVE systems were shut down on October 1, 2008.

Progress Since Last Five-Year Review

The first, second and third FYR reports found that the remedy is in place and is protective ofhuman health and the environment. ·

The Ponderosa Remediation System was temporarily shut down in 2004 With tJi,e approval ofEPA. EPA has determined that the changes in regional groundwater flow in the area were based primarily on changes in pumping outside ofthe plume area (changes in public supply well pumping locations and volumes). Thus, the shutdown of the Ponderosa extraction well has had no discernible effects on the groundwater flow or the concentrations detected in the overall plume.

In the previous FYR, EPA concluded that resumip.g pumping from the Ponderosa Remediation System was not an effective means ofreducing chemical concentrations at the downgradient edges. qf the current plume. Ponderosa is located near the up gradient· edge of the plume and the concentrations in this vicinity ofthe Ponderosa Remediation System were already approximately · at or below MCLs w~en system, operation was temporarily suspended. Furthermore, the detections

8.

of TCE at the Sabana Hoyos 3 supply well are most likely not Site-related. As per the previous FYR recommendations perimeter wells M-5 and M-17 has been monitored so that an assessment can be made to determine if additional actions are required (Figure 3 and Figure 4). In addition, EPA recommended the permanent shutdown of the Ponderosa Remediation System since it no longer a necessary component of the Remedial Actions for the Site.

Monitoring Well M-5 is located approximately a mile north-northwest of the site property. The monitoring trends for TCE detected at MW-5 increased from 2005 through 2011 but have exhibited subsequent declines. The 5 Year Review states that the suspected source of the TCE detected at these levels is not Site-related. Further monitoring will be used to determine if the recent downward trend continues. If the trend does not decline, additional actions will be considered.

Although not the focus of this FYR, in August 2009, the SVE system decommissioning was completed.

Since the last FYR, additional groundwater monitoring has occurred and the results are discussed in the Data Review section below.

Five-Year Review Process

Administrative Components

The FYR team included Adalberto Bosque (EPA-RPM), Robert Alvey (EPA-Hydrologist), Marian Olsen (EPA-Human Health Risk Assessor), Charles Nace (EPA-Ecological Risk Assessor), Melvin Hauptman (Chief of the Pre-Remedial Section) and Brenda Reyes (EPA-Community Involvement Coordinator). This is a PRP-lead Site.

Y..a AIU - ~W... Silo v... -.P_,.,ltic.,

Toal voe COAC44•...,. w -~-. . -101

~ , - Zone 101 -l ft

:l00 i--~~~~~--1t·~~~~~~~~~~

-e- l,al,. fl .tlftMSI. ,

...._ l.al 1· 1112 UISl •

Figure 3 Monitoring Well MS TCE Concentration Trends

9

v• AA>"~ it s..i.1y- si. v.p llJQ, 1'- lllCe

T-IVOCC... ­...n'Mn lb- , JL, • . ..... •1

100

90 -.-Zone6 1-M nli. 1

80 1.bfW."'4 ( 1Mll J

7mo 11-•!l5•MSl1

Figure 4 Monitoring Well M17 TCE Concentration Trends

Community Involvement

A notice that EPA was performing this FYR was posted on EPA's website. Once the FYR is completed, the results will be made available at the local Site repository, identified as the Vega Alta Digital Library located at the Luis Mufi.oz Rivera Street# 64. In addition, efforts will be made to reach out to local public officials to inform them ofthe results. A notice of this action was posted in EPA's Region 2 website.

Document R

The documents, data and information which were reviewed m completing this FYR are summarized in Table 2.

Data R vie

Groundwater samples from extraction wells and certain monitoring wells are analyzed for VOCs on a monthly basis. The effectiveness of the treatment system is monitored by sampling the influent and effiuent of the air stripper. The analytical data is presented along with historical results and submitted to EPA in monthly progress reports.

Currently, groundwater samples from the SAW wells in operation are analyzed for VOCs on a monthly basis. The effectiveness of the treatment system is monitored by sampling the influent

10

and effluent groundwater passing into and out ofthe air strippers. The analytical data are submitted to EPA in monthly progress reports.

The ongoing groundwater monitoring program, including sampling locations, sampling procedures, sampling frequency, laboratory analytical methods, and supporting information were specified in the EPA-approved Revised Sampling, Analysis and Monitoring Plan (RSAMP), March 2010 (2010 RSAMP), prepared by LBG dated March 16, 2010. The 2010 RSAMP updated sampling locations, sampling frequencies, and reporting format from the 1998 Revised Sampling, Analysis and Monitoring Plan (1998 RSAMP). The chemicals of concern in groundwater are voes, predominantly TeE.

As described in the 2010 RSAMP, groundwater monitoring focuses on multi-port sampling zones and pumping wells situated within the unconfined aquifer in the Aguada Limestone. The groundwater monitoring network consists of 15 multi-port monitoring wells (M2, M3, M4, M5, M6, M8, M9, Ml 1, Ml2, Ml3, Ml5, Ml6, Ml7, M19, and M22), one monitoring well (MW-23), and the OU-1 Source Area extraction wells (SAW-1 and SAW-2). Monitoring well MIO was damaged and permanently lost due to non-site related construction activities in the area and, in agreement with EPA, the PRPs suspended sampling at multiport wells M3 and Ml 1 due primarily to non-site related unsafe physical conditions near the wells as well as a redundancy with data from nearby monitoring wells M6 and M13. VOes are monitored at all 2010 RSAMP-designated multi-port zones and monitoring well locations on an annual basis. In addition, multiport wells MS and M17 continue to be monitored on a quarterly basis in accordance with the 2010 RSAMP. The influent and effluent ofthe SAW System are monitored for voes monthly to verify treatment system effectiveness and confirm that the system meets discharge requirements.

voe monitoring results are presented in quarterly reports and these provide a basis for evaluating ongoing voe reduction. The monitoring results to date have demonstrated voe reduction in the immediate vicinity of the voe Source Area and also in the downgradient plume. Table 3 summarizes TeE concentration trends at zones in monitoring wells included in the routine voe monitoring and sampling program. In general, concentrations in the source area, as monitored by well M22 and at wells M2, M3, M4, M6, M8, M9, Ml l, Ml2, M13, Ml5, Ml 7, and Ml9 exhibit stable or decreasing trends. While concentrations ofTeE continue to fluctuate in well M5, trends in data for well MS remain below peak concentrations and may starting to trend downward. Monitoring data for multiport well Ml 7 has shown an overall downward trend for the last 12 quarters and the PRPs recommended to be moved to annual sampling. Multiport monitoring well M22 is used as a routine sampling location since it is situated nearest to the voe source.

As of December 30, 2013, the SAW Treatment System has treated approximately 687 million gallons of groundwater since startup in December 2002. The SAW Treatment System has achieved, during this period of time, a total voe mass removal of approximately 1,080 pounds. As of November 16, 2004, the date when the Ponderosa System was temporarily shut off, the Ponderosa System had treated approximately 1.9 billion gallons ofgroundwater and had removed approximately 600 pounds of VOes. At the time that the Ponderosa System was shut down, individual compound concentrations in its pre-treated groundwater had fallen below the relevant federal MeLs.

An analysis ofsamples collected from the SAW Treatment System on December 5, 2013 identified the following five compounds in the influent stream: 1,1-dichloroethene (4.1 ug/L); chloroform (2.1 ug/L); cis-1,2-dichloroethene (1.9 ug/L); tetrachloroethene (3.4 ug/L); and TeE (100 ug/L). No compounds were detected in the effluent sample. These analytical results show that the SAW

11

Treatment System is effective in treating the extracted water to below a laboratory detection limit of0.5 ug/L.

Site Inspection

The inspection of the Site was conducted on March 31, 2014. In attendance were Adalberto Bosque, EPA, and Miguel Cedeno, IMMAC Environmental Services as consultant for the PRPs. The purpose of the inspection was to assess the protectiveness ofthe remedy.

During the inspection the RPM assess the operation ofthe treatment systems. Inspection revealed that the system is in good conditions. It was confirmed that the system is functioning as required in the OU-1 ESDs and the OU-1 ROD.

Institutional Controls Verification

There were no institutional controls required pursuant to either of the RODs. At the time the RODs were issued, as well as currently, Commonwealth rules and regulations exist requiring governmental approval prior to the installation of wells. Consequently, there does not appear to be a risk that potable water wells would be installed during the period of remediation. The contaminated groundwater plume has been identified and is under control. Water is provided to the local residents by the public water supply. The Commonwealth requirements involving the installation ofwells remain in effect. The goal of the groundwater remediation is to meet federal drinking water standards and EPA believes it eventually will. There remains no need to include institutional controls as a component of the remedy for this Site since the potential for exposure does not exist and is being controlled through Commonwealth activities and requirements.

Technical Assessment

Question A: Is the remedy functioning as intended by the decision documents?

The remedy is functioning as intended by the decision documents. The primary objectives of the 1987 and 1997 RODs, as modified by the 1989, 1994 and 1997 ESDs, are to control the remaining source of contamination at the Site, to reduce and minimize the contaminants in the groundwater, reduce voes in the groundwater to the level of 1 ug/1 and to minimize any potential human health and ecological impacts resulting from the exposure to contaminants at the Site. A review of the monitoring data indicates that the pump and treat system is functioning as designed.

Human exposure to the contaminated groundwater at the Site has been further prevented by connecting the users ofthe G& M Cash and Carry private wells to the PRASA distribution system. In addition, under a private agreement with the PRPs, users of the Monterrey 2 well have been provided potable water to meet their current drinking water needs since early 1997.

There were no institutional controls required pursuant to either of the RODs. At the time the RODs were issued, as well as currently, Commonwealth rules and regulations exist requiring governmental approval prior to the installation of wells. Consequently, there does not appear to be a risk that potable water wells would be installed during the period of remediation. The contaminated groundwater plume has been identified and is under control. Water is provided to the local residents by the public water supply.

12

Question B: Are the exposure assumptions, toxicity data, cleanup levels, and remedial action objectives used at the time ofthe remedy still valid?

a. Groundwater use at the Site is not expected to change during the next five years. The land use considerations and potential exposure pathways considered in the baseline human health risk assessment are still valid. The federal MCLs identified in the 1987 ROD remain protective ofhuman health.

The groundwater risks identified in the 1987 ROD focused on potential use of the aquifer as a potable or drinking water source with exposures expected to occur through ingestion or other domestic use ofcontaminated groundwater distributed through the PRASA system for children and adults. In addition, users ofMonterrey 2 and G&M Cash and Carry private wells are connected to the PRASA distribution system. Other activities such as the OU-2 installation and operation of the SVE system also reduced soil contamination that contributed to the contaminated groundwater. At the current time, exposures through consumption of groundwater at the Site are interrupted and not a completed exposure pathway. The baseline human health risk assessment identified the following chemicals of concern: 1,1-dichloroethene, ethylene dibromide, TCE, arsenic and beryllium. Since the last FYR the toxicity values for TCE were updated through EPA's Integrated Risk Information System (IRIS) that represents EPA's consensus toxicity information for chemicals. In addition, the IRIS program is currently updating the toxicity values for arsenic and this will need to be re-evaluated in the next FYR.

The property is zoned industrial and there have been no changes in the physical conditions at the Site that would affect the protectiveness of the remedy. The selected cleanup values selected in the 1987 ROD were the federal MCLs for drinking water established under the Safe Drinking Water Act and these values remain valid. The 1989 Unilateral Administrative Order (UAO) for the Vega Alta Site required reduction ofeach contaminant in the treated water and the aquifer to the level of 1 ugi'L.

The contaminated plume does not discharge to any surface water; therefore, there are no completed pathways for ecological receptors. The effluent from the treatment plant is discharged to Honda Creek; however, the effluent is monitored and it meets discharge criteria that are protective ofecological receptors. The remedy and RA Os are still valid and protective of ecological endpoints.

Overall, the exposure assumptions, toxicity data, cleanup levels, and remedial action objectives used at the time ofthe remedy remain valid. There are no changes in the toxicity or exposure assumptions that will change the overall conclusions of the risk assessment.

b. Vapor Intrusion - The conclusions from the previous FYR for vapor intrusion have not changed. Specifically, the depth to groundwater water is close to 100 feet across the Site. The 2001 OSWER Draft Guidance for Evaluating the Vapor Intrusion to Indoor Air Pathway from Groundwater and Soils (Subsurface Vapor Intrusion Guidance) indicates that the evaluation ofvapor intrusion from groundwater contamination is not recommended when the depth to groundwater is 100 feet or greater. Therefore, further evaluation of this pathway is not believed to be necessary. The remedy remains protective.

13

Question C: Has any other information come to light that could call into question the protectiveness ofthe remedy?

There is no information that calls into question the protectiveness of the selected remedies.

Issues, Recommendations and Follow-Up Actions

The selected remedy is fully implemented. It includes ongoing operation, maintenance and monitoring activities as part of the selected remedy. As anticipated by the decision documents, these activities are subject to routine modification and adjustment. EPA will continue to oversee the PRPs to ensure they are carrying out the necessary O&M ofthe groundwater treatment systems.

Protectiveness Statement

. '

Protectiveness Statement(s)

Operable Unit: OU-1

Protectiveness Determination: Protective

Addendum Due Date (ifapplicable):

Protectiveness Statement: The OU-1 remedy is protective ofhuman health and the environment.

. .·. ~it"ewide Protectiv~11ess Statement

Protectiveness Determination: Addendum Due Date (ifapplicable): Protective

Protectiveness Statement: The remedy is protective ofhuman health and the environment.

Next Review

The next FYRw report for the Vega Alta Superfund Site is required five years from the completion date of this review.

14

Appendix 1: Tables

15

T hi e 1 Ch I ventsa rono oe:v ofS"te E Event

The U.S. Geological Survey (USGS) discovered volatile organic compounds (VOCs) in a groundwater sample from the Ponderosa water-supply well located south of the municipal landfill. ­

The Technical Assistance Team (TAT) collected and analyzed samples from the public water distribution system and supply wells on a monthly basis.

Site placed on National Priorities List (NPL).

Remedial Investigation Report (RI) developed by EPA's contractor (NUS Corporation) and reviewed and approved by EPA.

Feasibility Study Report (FS) developed by EPA's contractor (NUS Corporation) and reviewed and approved by EPA.

Record ofDecision for OU-1.

Administrative Order, Index No.11- CERCLA-80217.

Explanation ofSignificant Differences, Vega Alta Public Supply Wells Site (OU-1).

Administrative Order, Index No. II - CERCLA-90302.

Administrative Order, Index No. II-CERCLA-00301.

Completion of Ponderosa Treatment System. Groundwater Treatment System Operation initiated.

Explanation ofSignificant Differences, Vega Alta Public Supply Wells Site (OU-1). Amendment to Administrative Order, Index No. II - CERCLA-90302.

Explanation ofSignificant Differences, Vega Alta Public Supply Wells Site (OU-1).

Amendment to Administrative Order, Index No. II - CERCLA-90302.

Remedial and Supplemental Groundwater Investigation of the Vega Alta Superfund Site, Vega Alta, Puerto Rico, prepared by Geraghty and Miller, Inc. (OU-2).

Record of Decision for OU-2 signed by EPA- Region 2.

Final Remedial Design Work Plan for OU-1 prepared by Blasland, Bouck & Lee, Inc. (BBL), and reviewed and approved by EPA.

Remedial Design Work Plan for OU-2 prepared by by Leggette Brashears & Graham (LBG) and reviewed and approved by EPA.

Preliminary Remedial Design Report for OU-1 prepared by BBL and reviewed and approved by EPA.

Five-Year Review Report for OU-1 prepared by EPA.

Final Remedial Design Report for OU-1 prepared by BBL and reviewed and approved by EPA.

Date

June 1983

Septemberl 983 ­March 1984

September 1984

May 1986

July 1987

September 29, 1987

September 30, 1988

March 22, 1989

March 22, 1989

September 27, 1990

December 1993 July 1994

August 30, 1994

August 30, 1994

December 8, 1997

December 8, 1997

April 1995

September 30, 1997

November 25, 1998

December 18, 1998

February 16, 1999

April1999

January 2000

16

Remedial Design Report (30%) for OU-2 prepared by LBG and reviewed and approved by EPA.

Remedial Design Report (100%) prepared by LBG and reviewed and approved by EPA.

Final RA Work Plan OU-I prepared by BBL and reviewed and approved by EPA.

Initial Testing Plan SVE prepared by LBG.

SVE Operation and Maintenance Manual prepared by LBG and reviewed and approved by EPA.

Completion of SVE System Construction. Completion ofSAW System Construction. SAW Treatment System placed into continuous operation. SVE Treatment System placed into continuous operation. Preliminary Close-Out report prepared by EPA.

Remedial Construction Report for OU-1 prepared by WRS Infrastructure & Environment Inc.

Remedial Construction Report for OU-2 prepared by LBG.

Second Five-Year Review for OU-1 and OU-2 prepared by EPA. Temporary Shutdown of Ponderosa System. Closure testing on individual SVE wells. Draft Revised Remedial Action Report submitted to EPA. EPA's approved the permanent shutdown of the SVE system. Operation of SVE operations ceased. SVE Decommissioning Work Plan for OU-2 prepared by LBG and reviewed and approved by EPA. Monitoring Well MW-23 installed. Third Five-Year Review Report for OU-1 prepared by EPA SA W-2 Pump replaced. Revised Sampling, Analysis, and Monitoring Plan (2010 RSAMP) prepared by LBG Ponderosa Decommissioning and Demolition Work Plan (DDWP) prepared by LBG and reviewed and approved by EPA. EPA approves SVE Decommissioning Work Plan. SVE System Decommissioning completed. OU-2 Final Remedial Action Report submitted to EPA. EP As comments on Ponderosa DDWP provided by EPA. EPA approves implementation of2010 RSAMP. Response to EPA's comments on the DDWP prepared by LBG. EPA approvals of the Ponderosa DDWP and May 3, 2011 Response to EPA' s comments on the DDWP. Final Remedial Action Report for OU-2 approved EP As Certification of Completion of OU-2 Remedial Action.

June 2000

-July 2000

June 2001

August 2001

November 2001

October 2001 November 2001 December 2002 December 2002 March2003

September 2003

September 2003

March2004 November 2004 2004-2005 Seotember 15, 2008 Seotember 25, 2008 October 1, 2008 October 2008

Februarv 2009 August 2009 October 2009 March2010

March2010

March 23, 2010 September 2010 October 2010 January 12, 2011 March 11, 2011 May3, 2011 October 31, 2011

October 31, 2011 October 31, 2011

17

Table 2 Documents, Data, and Information Reviewed in Completing the Five­Year Review

Record ofDecision OU-1, Vega Alta Public Supply Wells, Vega Alta, Puerto Rico, prepared by EPA, Region 2, September 29, 1987.

Administrative Order, Index No. ll - CERCLA-80217, September 30, 1988.

Administrative Order, Index No. II- CERCLA-90302, March 22, 1989. Explanation of Significant Differences, Vega Alta Public Supply Wells Site, March 22, 1989 (OU-I).

Administrative Order, Index No. II-CERCLA-00301, September 27, 1990.

Amendment to Administrative Order, Index No. II - CERCLA-90302, August 30, 1994.

Explanation of Significant Differences, Vega Alta Public Supply Wells Site, August 30, 1994 (OU-1).

Amendment to Administrative Order, Index No. II- CERCLA-90302, December 8, 1997.

Explanation of Significant Differences, Vega Alta Public Supply Wells Site, December 8, 1997 (OU-1).

Record ofDecision OU-2, Vega Alta Public Supply Wells, Vega Alta, Puerto Rico, prepared by EPA, Region 2, September 30, 1997.

First Five-Year Review, August 1999.

Second Five-Year Review, August 2004.

Third Five-Year Review, August 2009.

Final Remedial Action Report, OU-2, October 2010.

Monthly Progress Reports for OU-1 (prepared by the PRPs), 2009-2013.

Quarterly Groundwater Sampling Reports, 2009-2013.

18

-----

-------

Table 3 TCE Concentrations observed in multiport wells/zone monitored annually

Monitoring Event Well ID 1st Quarter

1990 4th Quarter 2000 4th Quarter 2004 4th Quarter 2008 2nd Quarter 2013

M3>-----·-za-ne2_______.. ·---------------ils______...................................................1..60................................................----77-·-·---+-------·-- 11 ns

Zone 4 340 200 67 14 ns M4

Zone 3 ns 16 22 17 16 •MMMM""""'"'"""''-'"N--HHNHMOoOoOoOHHoOoNMHNNMO ONNM--MM•""""'"""''"''"''"""""""""""""""'"" OHHHHHHHHHHHHHNHHHHHHHHHOHHHoOH..HHoOHHoHHH..HOHHOooM ,.,,__,..._....,_..___~M--•HHHNHHHHHH HHHHHHHHHHHHHOHHmo..HOHHHMUM•NOOOONMMMMM..HHHHHHHHH -M--OHHHHHHH-N-MHHHHHHHHHMMHO--MOMOoHHH

Zone 4 ns 13 18 31 16 MS---·----..··-·zon0-·r·----------------.......9~r..--............_ ..-------:rr...·---·-·--- ..·-·--6.6-·---....................................................:,.5·--------..-·---· -·-·-..-....·-40-·-.._...____...._ M6

Zones 45 0.0 0.0 <0.5 <0.5!----·---..--- ­

Zone6 120 6 0.0 1.7 0.89 Zones 26 2.0 1.9 1.2 <0.5

MBlf--------+------+---------1·--------- --------------------llZone 1 32 56 41 35 21 Zones 33 93 86 79 37

M9 Zone3 390 110 130 74 36lf--------+------·.f---------1----- ---·--- ......................._..................------------ --------·-""""""'____Zones 488 130 130 S9 42

11--------+------+---------1----110 60 38Zone? 350 130 M11Zone 1 ----·--sao-----·---..--w---··-- ............-----~-·---..................................................26............__________..___ --·--···-·ns-----·-·

Zone 3 100 18 21 5.6 ns .______Zone 5----..-....----· --·-..·-95·--->------ 14 18 9.3 ns

M12 Zone 4 310 2 1.3 2.0 1.4------+---'-------- -­Zone 6 246 120 8.6 1.7 1.4

M13 Zone 5 ----- -----6.3 0.0 0.0 <O.S <0.5 Zone 8 ns 0.0 0.0 <O.S <0.5

M17 Zone 1 14 -12·---·----····-·--19 37 9.2Zone 4 ns -- ......-........................1..2...........................................................................1.4.............................................................................fg_____..................-­ --·----5~4-···-·-

-----z-o-ne-6---ii----ns-----1·---2-.0-----1·----3.8---- 14 _____....___________3._2_............____ M19

........--·-- zone--6-..____,_____ s.3 2.0 1.1 o.s7 <0.5 11---Z-o_n_e_1_0_-t---O-.O----r----O.-O-·---------------0:0........................__ ..._______..___..<_(fs_______.. ns

M20 Zones o.s 0.0 ns

M22 -- --..--....--....-­Zone4 ....- ....ns-....____ .,.______ 37 31 230 150 Zone6 ns 320 240 250 170_,_____......~~

Zones ns 730 210 0.95 150 Average of observed 157 76 45 36 34

concentrations

19