United Stap° ~ EnwensnenuJ Protection agency Office o( Emergency and Remedial Response EPA/RODm09-eo/046 June 1990 Superfund Record of Decision: Watkins-Johnson (Stewart Division), CA ------- 50272-101 REPORT DOCUMENTATION 11. REPORTHO. 12. PAGE EPA/ROD/R09-90/046 3. Aedplent8 ~on No. SUPERFUND RECORD OF DECISION Watkins-Johnson (Stewart Division), CA .'.., ZI.,..t-~nn - Fin;:t1 5. AepoI1 Date 06/29/90 4. Title and Subtille &. 7. Authorla) 80 PWfonnInG CrpnIza1Ion A8$IL 110. a. PWforming OrpJnlzdon M8m8 end Addt8M 10. Pro)8ctIT8IIIIWorII u..t No. 11. ConInct(C) or ChnI(O) No. (C) 12. ~ 0rganIuII0n"'" end AddrM8 U.S. Environmental Protection 401 M Street, S.W. Washington, D.C. 20460 (G) 11. TWP8 crI A8por1a PwIod C-.d Agency 800/000 ... 15. Suppl8m8nl.uy NoIM 1&. Aba"act (Umlt: 200 wolda) The Watkins-Johnson site is an active research and development, manufacturing, and industrial complex in Santa Cruz County, five miles north of Santa Cruz, California. The Watkins-Johnson Company has owned and operated the complex since 1963, conducting such activities as: . metal machining, degreasing, metal plating, and photo laboratory activities. During these activities, a variety of organics, inorganics and metals were used. In 1984, Regional authorities found TCE and TCA in the Watkins-Johnson wastewater disposal system. Further investigations revealed soil contamination at the site and ground water contamination in the Santa Margarita aquifer underlying the site. The aquifer has been designated a sole-source aquifer used for drinking water, and is comprised of a perched zone and a regional zone. In addition, the aquifer is easily accessible for drinking water supplies and for contamination from the ground surface. The primary contaminants of concern affecting the soil and ground water are VOCs including PCE and TCE, and metals including silver. (See Attached Sheet) 17. Doc&8MntAn8Jy818 .. D88crIpIore Record of Decision - Watkins-Johnson (Stewart Division), CA First Remedial Action - Final Contaminated Media: soil, qw Key Contaminants: VOCs (PCE, TCE), metals (silver) b. IdIn~T- c.COSAn~ 180 A¥IIII8IIIIty"""" 1.. II8curItr aaa (1N8 AIpor1) None 2D. s.a.ttr aaa (1N8 P8g8) tJnno 2'1. No. crI ..... 50 22. PI1c:8 ~ (See ANSi-Z3I.18) ..~"",..- (fonnllly NTlS-a) 08p8mwnt crI c:aa-c. ------- EPA/ROD/R09/046 Watkins-Johnson, CA First Remedial Action - Final Abstract (Continued) The selected remedial action for this site includes soil vapor (vacuum) extraction with pretreatment of extracted vapors using GAC prior to ambient discharge; capping and grading contaminated soil areas to minimize the potential for mobilization of soil contaminants to the ground water; installing infiltration leach fields to prevent offsite migration of ground water contaminants in the perched zone; installing gravity drains to transfer the contaminated ground water from the perched zone to the regional aquifer zone for subsequent extraction; ground water pumping and onsite treatment to remove contamination from both the perched and regional zones using GAC adsorption with offsite regeneration of spent carbon; discharge of treated water onsite for industrial and consumptive use, offsite to surface water, and onsite to recharge the perched zone; and ground water monitoring. The estimated present worth cost for this remedial action is $2,156,243, which includes an estimated annual O&M cost of $167,820. PERFORMANCE STANDARDS OR GOALS: Ground water treatment standards for both the perched and regional zones were based on chemical-specific SDWA MCLGs or the more stringent of SDWA MCLs or PMCLs and State MCLs, thereby achieving a residual risk of 10-4 to 1~. Chemical-specific goals include PCE 0.005 mg/l (PMCL) and TCE 0.005 mg/l (MCL). Soil remediation will ensure that soil no longer poses a threat to the ground water; however, no chemical-specific goals have been set for the soil. ------- . RECORD OF DECISION WATKINS-JOHNSON SUPERFUND SITE SCOTTS VALLEY, CALIFORNIA \ ,; ------- . RECORD OF DECISION DECLARATION STATEMENT SITE NAME AND LOCATION Watkins-Johnson Superfund site Scotts Valley, California STATEMENT OF BASIS AND PURPOSE This decision document presents the selected remedial action for the Watkins-Johnson Superfund site located in Scotts Valley, California, developed in accordance with the Comprehensive En- vironmental Response, Compensation, and Liability Act of 1980, 42 U.S.C. 19601, (CERCLA) and, the National Oil and Hazardous Sub- stances Pollution Contingency Plan, 40 C.F.R. Part 300, 55 Fed. Reg. 8666 (NCP). This decision is based on the administrative record for this site. The State of California has no objection to the technical aspect. of the selected remedy. , ASSESSMENT OF THE SITE Actual or threatened releases of hazardous substances from this site, if not addressed by implementing the response action selected in this Record of Decision, may present an imminent and substantial endangerment to public health, welfare, or the en- vironment. DESCRIPTION OF THE REMEDY The selected remedy for the Watkins-Johnson site addresses groundwater contamination, in which trichloroethylene is the primary contaminant of concern. Other contaminants detected in groundwater at concentrations exceeding the selected treatment standards include vinyl chloride, tetrachloroethylene, 1,1- dichloroethylene, 1,1-dichloroethane, 1,4-dichlorobenzene, cis- 1,2-dichloroethylene, and silver. The selected remedy also ad- dresses an area of soil contaminated with volatile organic chemi- cals including l,l-dichloroethylene, cis-l,2-dichloroethylene, tetrachloroethylene, methylene chloride, l,l,l-trichloroethane, l,1,2-t~ichloroethane, trichloroethylene and chloroform. This action represents the final remedial action to remove contaminants from groundwater and soil. Several response measures were previously performed at the site by Watkins- Johnson. The major components of the selected remedy will: ------- Table of Contents . Paqe Declaration I. Site Description...................................... 1 II. site History and Enforcement Activities............... 2 III. Community Participation Activities.................... 3 IV. Scope and Role of Response Action..................... 4 V. Summary of Site Characteristics....................... 5 VI. Summary of Site Risks................................. 7 VII. Summary of Alternatives............................... 11 VIII. Comparison of Alternatives............................ 17 IX. The Selected Remedy................................... 19 X. Statutory Determinations.............................. 24 XI. Documentation of Significant Differences.............. 25 XII. Reservation of Record................................. 26 Attachments Response Summary List of Figures Fiqure 1. Site Location Map 2. Hydrogeologic Cross-Sections 3. Detailed Site Map 4. Distribution of TCE in the Regional Aquifer, May 1987 5. Distribution of TCE in the Regional Aquifer, March 1989 List of Tables Table 1. Concentration of Contaminants in Soil and Groundwater 2. Summary of Carcinogenic Risk at the Site 3. Summary of Non-carcinogenic Risk at the Site 4. Remedial Alternatives 5. Summary of Applicable or Relevant and Appropriate Require- ments for the Site 6. Federal and State Groundwater Treatment Standards for the site 7. Summary of Costs of Selected Remedy 8. Estimated Rates of Groundwater Pumping and Discharge ------- DECISION SUMMARY . I. SITE DESCRIPTION The Watkins-Johnson Superf~nd site (the site) is located in Santa Cruz County, approximately 5 miles north of the City of Santa Cruz, in a small valley located west of the city of Scotts Valley, east of Sky Park Airport, and southwest of the Santa Cruz Mountains (Figure 1). This area is considered to be within the California Coast Range and is in close proximity to California's Pacific coastal zone. The elevation at the Watkins-Johnson site is approximately 460 feet above mean sea ~evel (MSL). The area north of the site is comprised of forested mountains that are incised by numerous stream channels. Surface elevations within this mountainous area range from 400 to 1,200 feet above MSL. The area south of the site is comprised predominantly of rolling grassy hills with sur- face elevations ranging from 560 to 800 feet above MSL. Several creeks drain the region. These include Bean Creek, . Carbonera Creek, Lockhart Gulch, Ruins Creek, and Zayante Creek. \ Bean Creek, a tributary to Zayante Creek, crosses north of the site and roughly divides the major aquifer, the Santa Margarita, into northern and southern portions. Both Zayante and Carbonera Creeks drain into the San Lorenzo River, which is west of the site. The San Lorenzo River flows southward and eventually enters the Pacific Ocean at Monterey Bay. The Santa Margarita aquifer which underlies the site, is a major source of groundwater for the Camp Evers, Scotts Valley, and Mission Springs areas. EPA designated the Santa Margarita aquifer as a sole source aquifer, used for drinking water. In the Scotts Valley area, the aquifer is unconfined, and the Santa Margarita Formation crops out over much of the land surface. In the immediate vicinity of the Watkins-Johnson site, the Santa Margarita aquifer is comprised of a perched zone in addition to the regional zone (Figure 2). The perched zone is elevated about 35 feet above the regional zone. The aquitard which supports the perched groundwater and separates the two zones is a moderately cemented conglomerate. The aquifer is accessible for development of drinking water supplies and for contamination by chemicals migrating from the ground surface. 1 ------- F elm) 8"18 ....... IUIn SIR M-48 ..... Q CIISfJ - .... - ~ - i1 I - I - g - I I - . .. - fIllY ~ ...... ..... 0-- ...... Ell -.,...... .& ... ana . ..... .-sIal. .Sf8I5IS >.__t. - 1-'" -- CII8II ..'; .... -.mm t8 - 1-'" 818ft... ......CIUICIC ClOSS SI:CTlCIIS F-F' -5-" 1-- 1-'" WIfICII. Ulll8Mn8 . a ..... 81 ...... - -.... - _1M .-..,.. -. ......- "", ...t ... 0' (UIt' Me F' (IASn Me -~ ; -~ -I -~ ! .. c -; N -~ i1 ... I ~ ,. - II !: c -; ,. ncURI J ------- III. COMMUNITY PARTICIPATION ACTIVITIES EPA has maintained three information repositories containing the Communit, Relations Plan, RI/FS Reports, technical documents, fact sheets, and other reference material. These repositories are located at the Scotts Valley Branch of the Santa Cruz Public Library, the Scotts Valley Wate~ District Office, and the Scotts Valley Wastewater Division Office. In addition, the entire Ad- ministrative Record is available at the Scotts valley Branch . Library. The availability of these documents, as well as the an- nouncement of a public comment period extending from February 14, 1990 until April 14, 1990 was published in the Santa Cruz Sen- tinel on February " 1990 and in the Scotts Valley Banner on February 14, 1990. On February 28, 1990, EPA representatives briefed members of the Scotts Valley Town Council on the Proposed Plan for remedia- tion of the site. In addition, a public meeting was held on March " 1990, at which EPA representatives presented the Proposed Plan for the site and answered questions. A response to comments received during the public comment period is included in the Response Summary, which is part of this Record of Decision (ROD) . \ 3 ------- . . WATKINS-JOHNSON SITE MAP . . GAC WA7£'R TREA Tl/ENT SYSIDI =:: LEACH F7EJ.D A . . . . . .. A BUILDING 6 . .. . . J..EQ£lQ A Groundwoter Extraction WeIll . Groundwater Monitoring Wells .. Grovlty Drain . : tr~-- 'f I fIGURE 3 ------- o o o TCE is the major contaminant of concern in the perched zone. The area consistently containing the highest concentrations is near the former Building 6 dilution tafik. TCE values analyzed from groundwater samples in this area range from 34 to 13,000 ug/l. In addition to TCE, 1,1-dichloroethylene (l,l-DCE) and vinyl chloride are constituents of interest for the perched zone (Table 1). Detection of 1,1-DCE in concentrations equal to or greater than 2 ug/l was limited to test wells on the edge of the TCE plume. Vinyl chloride was detected in three wells in september 1988. o TCE was the major contaminant detected in the regional zone together with lesser concentrations of 1,1,1- trichloroethane (l,l,l-TCA), 1,2-DCE, and 1,1-DCE (Table 1). The concentrations of TCE formed a narrow cigar-shaped plume which extended to the northwest, to Bean Creek in May 1987 (Figure 4). The highest con- centrations of TCE were north of the Building 6 dilu- tion tank area. Data collected since the initiation of aquifer restoration indicate that the contaminant plume, within the regional zone, has steadily diminished and is now contained almost entirely within. the plant area (Figure 5). \ Six private wells have been found north of the Watkins-Johnson site that are considered potential receptors. These wells are located downgradient. from the site in the generally northward flow path of the perched zone. However, not only has the TCE distribu- tion, which is limited to the plant area, not changed in extent over time, but the present aquifer restora- tion control scheme is preventing northward flow of contamination toward these wells. o. The aquifers in the Monterey and Lompico formations un- derlie the contaminated Santa Margarita Formation. There is an apparent upward gradient from the Lompico to the Monterey, which indicates that the potential for contaminants to flow from the Santa Margarita to the Monterey or Lompico in the vicinity of the plume is very small. Bean Creek is directly connected to the perched zone in the area upstream from Ruins Creek extending at least to the point where treated water is discharged to Bean Creek. Downstream from Ruins Creek, Bean Creek is hydraulically connected to the regional aquifer. Although contamination had previously been found in Bean Creek, more recent sampling shows contamination is below detection limits. . 6 ------- ....... - --...:-.. - . =-=:.::-.. .... :.-----.. ..... -- =-:.-.::...-_.. ..... ---- ..-- .--- .... --- - .----==--- ~ -.-.--- :-.--- - ----- ----.--- ------ . -- -------- , , I -----'" ! .~ . -- - . - - lilt Ilmlllf.. . -. fII( .C'1IMl -.- ca._IU.IIE .1 ... a TO ... .. .., nev.. , ------- The third step of the Lisk assessment is the toxicity as- sessment. Chemicals present at this site include both car- cinogens and non-carcinogens. Three contaminants are of concern based on their potential ability to cause cancer: TCE is a Group B-2 agent, probable human carcinogen; 1,1-DCE is a Group C Agent, possible human carcinogen; and vinyl chloride is a Group A Agent, known human carcinogen. These classifications are based on the strength of scientific evidence that these agents may be car- cinogenic. For TCE, there is sufficient evidence of car- cinogenicity in animals, and inadequate evidence that the com- pound is carcinogenic in humans. For 1,1-DCE, there is only limited evidence the compound is carcinogenic in animals and the available evidence on humans is inadequate. For vinyl chloride, there is sufficient evidence of carcinogenicity in animals and humans. Cancer Potency Factors (CPFs) have been developed by the EPA's Carcinogenic Assessment Group (CAG) for estimating excess lifetime cancer risks associated with exposure to potentially carcinogenic chemicals. CPFs, which are expressed in units of mgjkg-day, are multiplied by the estimated intake of a potential carcinogen in milligrams per kilogram per day (mgjkgjday) to provide an upper-bound estimate of the excess lifetime cancer risk associated with exposure at that intake level. The term "upper-bound" reflects the conservative estimate of the risks . calculated from the CPF. Use of this approach makes underestima- . tion of the actual cancer risks highly unlikely. CPFs are derived from the results of human epidemiological studies or chronic animal bioassays to which animal-to-human extrapolation and uncertainty factors have been applied. Several non-carcinogenic chemicals have been identified to be chemicals of concern at this site. Reference doses (RfDs) have been developed by the EPA for indicating the potential for adverse health effects from exposure to chemicals exhibiting non-carcinogenic effects. The RfD is an estimate, with an uncer- tainty of perhaps an order of magnitude, of a lifetime daily ex- posure for the entire population (including sensitive in- dividuals) that is expected to be without appreciable risk of deleterious effects. Estimated intake of chemicals from environ- mental media (e.g., the amount of a chemical ingested from con- taminated drinking water) can be compared to RfDs. RfDs are derived from human epidemiological studies or animal studies to which uncertainty factors have been applied (e.g., to account for the use of animal data to predict effect on humans). These un- certainty factors help ensure that the RFDs will not underes- timate the potential for adverse non-carcinogenic effects to oc- cur. The last step in the risk assessment process is the risk characterization. At this point the information from the proceeding steps is combined to determine if an excess health risk is present a~ the site. Excess lifetime cancer risks are determined by multiplying the intake level with the cancer potency factors. These risks are probabilities that are-6 generally expressed in scientific notaiion (e.g., 1 X 10 ). An excess lifetime cancer risk of.1 X 10- indicates that, as a plausible upper-bound, an individual has a one in one millio~ 8 ------- tial endangerment to wildlife in the vicinity of the site which might occur due to contamination of Bean Creek. Based on the more recent rounds of surface water sampling, no contaminant con- centrations ~ave been detected in Bean Creek. Furthermore, the ongoing aquifer restoration begun in October 1986 has sig- nificantly reduced the extent of the groundwater contaminant plume so that it no longer intercepts or threatens to intercept Bean Creek. There is no evidence, based on the survey, that any fish or wildlife trust resources inhabit the property. The industrial nature of the property and extensive coverage of soil by build- ings and pavement prevent potential exposure of migratory birds to contaminated soil. The failure to detect volatile organic compounds in Bean Creek downstream of where the groundwater in- tercepts the creek suggests that aquatic life in the creek is not presently at risk from site-related contaminants. 10 ------- perched zone gravity drains plus the Building 8 leachfield, gravity drains plus Building 8, 2, and 6 1eachfie1ds and the Test Well (existing well to be used for extraction), and gravity drains plus Building 8, 2, and 6 1eachfie1ds and soil flushing at the former Building 6 dilution tank. Groundwater Extraction: This technology uses a combination of existing and new extraction wells to create a cone of depres- sion to capture and remove the contaminant plume from the regional aquifer. Groundwater extraction from the perched zone has been shown to be difficult due to the local hydraulic charac- teristics and dewatering problems. There is currently one perched zone extraction well on-site that is operated intermit- tently and is considered a part of this option. No Action: The no-action option represents a baseline against which the other alternatives are compared. No effective remedial strategies would be implemented in either the perched or regional zones. Existing gravity drains would be plugged, in- filtration through the existing 1eachfie1d would be discontinued, and existing extraction wells would be abandoned. Contaminated groundwater would be allowed to migrate off-site and into Bean Creek. Perched zone groundwater would migrate northward, leaking into the regional zone and eventually discharging into Bean Creek. This option provides no mitigation of existing risks, and would allow other areas to be impacted. These conditions would persist indefinitely until the contaminant plume had been diluted, completely discharged, or reduced by natural biological and chemical processes. Groundwater Treatment Several processes have been evaluated to remove chlorinated hydrocarbons from extracted groundwater consistent with the ex- isting National Pollution Discharge Elimination System (NPDES) permit and as a requirement for discharge in conjunction with other disposal methods. The treatment technologies described below include granular activated carbon (GAC) adsorption, air stripping, and ultra violet (UV) oxidation. The no-action option is also summarized. Granular Activated Carbon (GAC) Adsorction: This technology uses large volumes of GAC to filter contaminated groundwater. The filtration bed would be replaced with fresh GAC as necessary for the effective removal of contaminants; the spent GAC would be regenerated off-site. The current GAC treatment system on-site consists of two pressurized vessels each containing 20,000 pounds of GAC. The units are operated in a continuous mode with groundwater pumped directly into the distribution system at 20 pounds per square inch gauge (psig). GAC is very effective in removing chlorinated hydrocarbons from water provided that the carbon is replaced periodically. The existing system has been shown to treat groundwater down to 12 ------- Treated Water End Use Watkins-Johnson currently uses treated groundwater in three ways: on-si~e industrial and drinking water, off-site discharge to Bean Creek, and recharge to the perched zone. Concern has been raised that the water currently discharged to Bean Creek could be used as an off-site drinking water supply to offset ex- isting groundwater pumpage. At this time, we estimate that only 25 gallons per minute of treated groundwater will be discharged to Bean Creek; this is the estimated minimum flow necessary to maintain the habitat and support aquatic life. If the estimated volume of the discharge to Bean Creek should increase sig- nificantly, EPA may consider designating other uses for the treated effluent. Such a change may be reflected in an Explana- tion of Significant Difference or other appropriate document. A change in the designated use of the treated effluent may include the off-site domestic use of treated groundwater in conjunction with the Creek discharge. The discharge to Bean Creek is an off-site discharge for which Watkins-Johnson must continue to ob- tain all appropriate permits, including an NPDES permit from the Regional Board, and comply with a1~ applicable State and federal laws. . Source Control The Risk Assessment prepared for this site indicates that existing soi1 contamination poses no significant risk to human health or the environment through direct contact. However, direct exposure may occur as a result of on-site excavation. In addition, existing contamination continues to threaten groundwater quality. contamination has not been identified within the uppermost fifteen feet of soil. Most areas of detected soil contamination are beneath asphalt caps which sig- nificantly reduce the downward mobility of the residuals. The highest concentrations of soil contamination are in the area of the former Building 6 dilution tank. The detailed analysis evaluated four source control options. These were treatment by vapor extraction, by soil flushing, stabilization by capping and grading, and the no action option. A source control option(s) will be required to treat soils to a level that no longer presents a threat to the groundwater. Soil VaDor Extraction: This technology uses a suction to remove organic contaminants from the soil matrix. A vacuum is applied to a dry well screened in the contaminated vadose zone. The vacuum applied is sufficient to cause residual contaminants to partition from the soil matrix into the soil gas and be evacuated from the well. Soil vapor may be treated at the sur- face to remove organic constituents prior to ambient discharge. A pilot system operated at the site of the former Building 6 dilution tank indicated that soil vapor extraction is capable of removing small quantities of residual soil contamination. Ef- fluent from the pilot system contained such small quantities of contaminants that health-based risk from this source would be negligible. However, a full-scale vapor extraction operation 14 ------- groundwater from both the perched and regional zones; GAC adsorp- tion to treat the extracted groundwater; soil vapor extraction to remove VOCs from the soil; capping and grading to minimize the potential foe mobilization of soil contaminants to the groundwater; and on-site industrial and consumptive use of treated water, off-site discharge to Bean Creek, and on-site recharge to the perched zone. The capital cost for this alternative is estimated to be $837,738; the annual operation and maintenance cost (O&M) is es- timated to be $167,820. The present worth of this alternative is estimated to be $2,156,243. Alternative 2: This alternative includes the use of leach- fields to control movement of the perched zone contaminant plume; gravity drainage to transfer perched zone contamination to the regional zone; groundwater extraction to remove contaminated groundwater from both the perched and regional zones; air strip- ping to treat the extracted groundwater with GAC adsorption to treat air emissions; soil vapor extraction to remove VOCs from the soil; capping and grading to minimize the potential for mobi- lization of soil contaminants to the groundwater; and on-site in- dustrial and consumptive use of treated water, off-site discharge to Bean Creek, and on-site recharge to the perched zone. \ The capital cost for this alternative is estimated to be $611,938; the annual operation and maintenance cost (O&M) is es- timated to be $167,820. The present worth of this alternative is estimated to be $1,930,443. Alternative 3: This alternative includes the use of leach- fields to control movement of the perched zone contaminant plume; gravity drainage to transfer perched zone contamination to the regional zone; groundwater extraction to remove contaminated groundwater from both the perched and regional zones; UV oxida- tion to treat the extracted groundwater; soil vapor extraction to remove VOCs from the soil; capping and grading to minimize the potential for mobilization of soil contaminants to the groundwater; and on-site industrial and consumptive use of treated water, off-site discharge to Bean Creek, and on-site recharge to the perched zone. The capital cost for this alternative is estimated to be $703,938; the annual operation and maintenance cost (O&M) is es- timated to be $139,000. The present worth of this alternative is estimated to be $1,796,171. 16 ------- Reduction of Toxicity, MobiJitv, or Volume Throuqh Treatment All three alternatives use treatment to permanently and sig- nificantly r~duce the toxicity, mobility or volume of con- taminants in both the soil and groundwater. Therefore, all three satisfy the statutory preference for remedies utilizing as a principal element treatment that significantly reduces the toxicity, mobility or volume of the hazardous substance. Short Term Effectiveness Alternative 1 performs best under this criterion because it poses the least risk to human health and the environment during implementation. Although Alternative 3 has the potential to be equally effective in the short term, no data is currently avail- able to indicate whether implementation would pose any risk to human health and the environment. Alternative 2, using treatment by air stripping and GAC adsorption, has the potential for posing impacts to human health and the environment during implementa- tion. While air stripping is capable of treating to nondetec- table levels and permanently destroying the removed contaminants, a large influent contaminant concentration could exceed the design capacity of the stripper, allowing effluent discharges in excess of the treatment standards. All the remedial alternatives will achieve their remediation goals within similar time frames. ImDlementabilitv The three alternatives perform equally under this criterion. The administrative and technical feasibility of each of the al- ternatives is comparable. Cost Alternative 3 is the least costly alternative. 1 is the most costly alternative. Alternative State AcceDtance It is believed that the state would accept any of the three alternatives evaluated. Community AcceDtance It is believed that the community would accept any of the three alternatives evaluated. 18 ------- In the case of zinc, the only number available was the Secondary federal MCL, and this number was selected as the treat- ment standard. For several chemicals (1,2-dichlorobenzene, cad- mium and lead), only proposed MCLs or MCLGs exist, and these values were chosen as treatment. standards. In the case where no federal MCLGs, federal MCLs or state MCLs are promulgated or proposed, then the State Action Level or Applied Action Level was selected as the treatment standard. This was the case for 1,1- dichloroethane. In the case of nickel, the only value available was an EPA Health Advisory, and this value was selected as the treatment standard. In the case of vanadium, no values were identified for selection as treatment standards. However, this chemical was only detected in 1 of 21 perched zone samples and 2 of 32 regional zone samples, and was, thus, eliminated from fur- ther consideration. The following compounds were detected in groundwater at con- centrations exceeding their selected treatment standards: trichloroethylene, vinyl chloride, tetrachloroethylene, 1,1- dichloroethylene, 1,1-dichloroethane, 1,4-dichlorobenzene, cis- 1,2-dichloroethylene and silver. Treatment to the specified stand~~ds will result in a residual risk within the range of 10-4 to 10 . \ Health-based ARARs pertaining to soil contamination are not available for the site. The soil contamination will be remediated to a level that no longer poses a threat to the groundwater. This alternative also complies with the Monterey Bay Unified Air.Pollution control District (MBUAPCD) Rule 1000 which is applicable to any air emissions associated with this remedial action. The land disposal restrictions of Subtitle C of the Resource Conservation and recovery Act (RCRA) are not ARAR for this remedial action. The treatment technoloqy used in this alterna- tive will treat the contaminated groundwater to nondetectable levels. Once the groundwater is so treated, it no longer con- tains hazardous waste and no longer is subject to regulation un- der Subtitle C of RCRA. Technical Asnects of the Selected Remedy The selected remedy for the site involves several com- ponents, including containment and removal of contaminated groundwater within the perched and regional zones, treatment of extracted groundwater, and implementation of limited source con- trol measures. The costs for the selected remedy are summarized in Table 8. . At several points during the discussion of the selected remedy, specific remedial designs are referenced including the number and general location of gravity drains, extraction wells, and leachfields: the pumping rates of extraction wells: the dis- charge rate from the GAC system; the method of discharge from the GAC system: etc. EPA recognizes that specific engineering 20 ------- tures a major portion of th~ regional zone contaminant plume. The well on the airport property will be used to capture any por- tion of the contaminant plume that migrates beyond the influences of the on-si~e extraction wells. Groundwater quality monitoring will be necessary to ensure that contaminant levels remain below the treatment standards and to evaluate the progress of the remedy. It is estimated that this system will require 8 years to reach the treatment standards in the regional zone. The total pumping rate for the four extraction wells during the fourth quarter of 1989 was 209 gallons per minute (gpm): however, the total projected pumping rate is estimated to be 110 gpm. The pumping rate is likely to change during the remedial action process. Once the regional zone contaminant plume con- centrations have reached the treatment standards, the extraction wells will be shut down. This will result in the dissipation of the cone of depression and a return to natural flow conditions. continued groundwater quality monitoring on at least a quarterly basis will occur to ensure that contaminant levels remain below the treatment standards. The specific details of the groundwater monitoring program and the long term O&M requirements will be determined during the RD/RA phases. Contaminated groundwater removed by the 5 extraction wells i will be treated using a GAC adsorption system. This system is already on site and operating. The on-site GAC system treats contaminant concentrations to non-detectable levels. Effluent from the GAC system is dis- charged in three manners: on-site use at the Watkins-Johnson plant, on-site recharge through leachfields to maintain the perched zone groundwater mounds, and off-site discharge to Bean Creek. Discharge to Bean Creek is an off-site activity: there- fore, Watkins-Johnson must comply with all applicable laws and obtain all applicable permits for this discharge. Table 8 indicates the current (based on fourth quarter 1989 data) and projected water use rates for effluent from the GAC system. Discharge to Bean Creek is considered a beneficial use of a relatively minimal amount of water. This water assists in maintaining flow within Bean Creek, thereby protecting the as- sociated natural habitat. Based on the Risk Assessment, there is no significant risk posed to human health or the environment by leaving currently documented, residual soil contamination in place. However, by using source control measures and preventing further release of contaminants from soil to groundwater, the overall time for the groundwater remedy will be reduced. This will be accomplished through soil vapor extraction and capping and grading. Using this screened in the plied vacuum is tition from the method, a vacuum is applied to a dry well contaminated portion of the vadose zone. The ap- sufficient to cause residual contaminants to par- soil matrix into the soil gas and be evacuated 22 ------- X. STATUTORY DETERMINATIONS The selected remedial action is protective of human health and the enviconment. For each pathway of exposure at the site, the remedy eliminates, reduces or controls the riski posed. The overall site risk will be reduced to within the 10- to 10-6 range for carcinogens and the Hazard Indices for non-carcinogens will be less than one. Implementation of the remedy will cause no unacceptable short-term risks or cross-media impacts. The selected remedial action complies with all federal and state ARARs. These ARARs are listed on Tables 5 and 6, attached to and incorporated herein by reference. The selected remedial action is cost-effective. The overall effectiveness of the selected remedial action is proportional to its cost, in that it represents a reasonable value for the money to be spent. As discussed in the Comparison of Alternatives Section of this ROD, the selected remedy utilizes permanent solutions and alternative treatment technologies or resource recovery tech- nologies to the maximum extent practicable. The selected remedy. provides the best balance of tradeoffs among the alternatives ~ with respect to the evaluation criteria, especially the five balancing criteria. The selected remedy was superior to the other alternatives under the long-term effectiveness and per- manence and short-term effectiveness criteria. All the remedial alternatives evaluated in the remedy selection process were ac- ceptable to the State and the community. The selected remedial action satisfies the statutory preference for selecting remedies in which treatment that per- manently and significantly reduces the volume, toxicity or mobility of the hazardous substances, pollutants and contaminants is a principal element. The remedial action uses treatment to address the contaminated groundwater, which is the principal threat posed by the site. GAC adsorption will remove volatile organic chemicals from the groundwater and will achieve a per- manent and significant reduction of the toxicity, mobility or volume of the contaminants. Similarly, vacuum extraction fol- lowed by vapor-phase GAC adsorption will remove volatile organic chemicals from contaminated soil, thereby also meeting the statutory preference. 24 ------- XII. RESERVATION OF RECORD The precise identification of long-term operation and main- tenance act~ities and the use of engineering and institutional controls, the details of an ongoing groundwater monitoring program, and the costs of each of these activities will be iden- tified during the RD/RA phase for the site. 26 ------- RESPONSE SUMMARY The Pro~osed Plan for the Watkins-Johnson site was issued to the public and announced that the public comment period would ex- tend from February 14, 1990 through April 14, 1990. The Proposed Plan described EPA's preferred remedial alternatives for con- taminated groundwater and soil at the site. On February 28, 1990, EPA briefed members of the Scotts Valley Town Council on the Proposed Plan, and on March 7, 1990 EPA presented the Proposed Plan at the public meeting. SUMMARY OF COMMENTS RECEIVED During the public comment period, EPA received only two let- ters regarding the Proposed Plan for the site. One comment let- ter, dated February 28, 1990 was provided by a group of residents from a local condominium mobile home park, and second comment letter, dated April 13, 1990, was provided by the Watkins-Johnson Company. The Chairman of the Board of Directors for the same residents group also provided verbal comment during the public meeting. EPA received written comments on the proposed remedy from the California Department of Health Services and the Centra~ Coast Region of the California Regional Water Quality Control \ Board. The substantive comments and EPA's responses are sum- marized below. Residents GrOUD Comment: The residents group requested access to that effluent from the on-site GAC system which is currently being discharged to Bean Creek, in order to help to help satisfy their water supply needs. Based on their calculations, the group estimated that with access to this water they could cut back their demands on the Santa Margarita aquifer, thereby saving approximately 280 aclft per year. The group pointed out that the transfer of this water was a relatively simple matter and that the distance in- . volved was less than 100 yards. EPA ReSDonse: SPA considered, but rejected at this ~ime, ~he residents' proposed option of allowinq ~he ~reated effluent ~o be used as a public wa~er supply source rather ~han discharqinq ~he ~reated effluent into Bean Creek. The residents' calculations were based on a discharqe rate of 187 qpm from the on-site GAC system to Bean Creek. Bowever, the current discharqe rate ~o Bean Creek is 157 gpm, and the projected discharqe rate i. estimated to be 25 qpm. Based on the projected discharqe rate ~o Bean Creek, BPA has determined that continued discharqe to Bean Creek is a beneficial use of this .ater, .s it .ssists in aaintaininq flow within the Creek, thereby protecting the .ssociatea natural habitat. In the event ~hat the actual discharge ~o Bean Creek significantly exceeas the estimatea 25 qpm rate, BPA may consiaer changing the designatea methoa of aisposal of ~he treated ef~ 27 ------- "This section of the ROD remedy selection should mention that some changes may be made to the remedy as a result ~f the the remedial design and construction process. The ROD should include a clear statement that such changes in general, reflect modifications resulting from the engineering design process." EPA ResDonsel EPA acknowledges the comment and has incorporated it into the "Selected Remedy" .ection of the ROD. 'lhe Selected Remedy specifies requirements regarding gravity drains and extractions wells; however, provisions have been included in the event that engineering modifications are required during RD/RA. 4. WJ pointed out that recent computer modeling indicates that the rate of groundwater extraction and the rate of discharge from the GAC system can be decreased, while still allowing for effec- tive containment of the contaminant plume. EPA ReSDonse: EPA has revised the "Selected Remedy" section of the ROD to \ clarify that engineering details such as the rate of groundwater extraction and discharge may be determined during the RD/RA. 5. WJ pointed out that the exposed area of residual soil con- tamination which the Proposed Plan requires to be capped, has al- ready been capped. Therefore, WJ felt that this section of the Proposed Plan was no longer required. EPA ReSDonse: BPA has addressed this change in sit. condition in the "Documentation of Siqnificant Chang.s" ..ction of the ROD. Al- though the cap component of the preferred alternative identified in the Proposed Plan has b.en complet.d, the remedy selected in this ROD maintains a cap as a component of the remedial action. The ROD incorporates 1:he cap component to ensure that the cap is maintained a8 part of the remedial action. 6. WJ proposed groundwater treatment standards consisting of MCLs at the property line with a goal of five times the MCL in- side the property line or until a zero slope occurs on the groundwater concentration vs. time graph for a period of one year. WJ supported this comment with the following statement taken from an October 18, 1989 memorandum from Jonathan Z. Can- non, OSWER Acting Assistant Administrator: "In many cases it may not be possible to determine the ultimate concentration reductions achievable in the groundwater until the groundwater extraction system has been implemented and monitored for some period of time. 29 ------- "Here Watkins-Johnson has already spent over $50,000 on vapor extraction. This effort was cost- effective at the outset -- eight kilograms of con- taminan~ mass were extracted in the first few weeks. However, after that, the effectiveness of the remedy dropped off quickly, to the point where only 20 grams per day were being removed. Therefore, the incremental costs of removing the remaining mass will be proportion- ally high compared with the effectiveness of the process. Unless EPA identifies a soil cleanup goal, it is not possible to perform the cost-effectiveness analysis that the NCP requires. Because EPA has already concluded that seil contamination presents no health hazards, EPA should follow its guidance document en- titled "Determining Soil Response Action Levels Based on Potential Contaminant Migration to Groundwater," EPA/540/2-89/057/, Oct. 1989." EPA ReSDonse: On Kay 8, 1990 representatives from WJ, BPA and DBS met to discuss the issue of whether 8011 vapor extraction is needed as part of the remedial .C~iOD at the site. WJ representatives presented evidence to document that vapor extraction was no longer necessary. EPA and DBS representatives both agreed, however, that existing information is not adequate to document that contamination in the vadose 80ne is Dot a continuing source of contamination of the groundwater. Therefore, BPA has selected a remedial action that includes soil vapor extraction as a com- ponent. Bowever, WJ may provide technical information to EPA during the remedial design stage to show that vapor extraction is no longer necessary. EPA will consider such information and decide whether any change of a component of the selected remedial action is warranted. Such a change would be reflected in an Ex- planation of Significant Differences or other appropriate docu- ment. \ EPA can provide WJ with a numerical 80del developed to ap- proximate the leaching of soil contaminants to the groundwater. This 80del .ay be calibrated aDd used with .ite-.pecific data to aid in determining when residual .oil contamination no longer poses a threat to groundwater. California Regional Water Quality Control Board, Central Coast Reaion (The Reaional Board} Comments: 1. The Regional Board submitted comments to EPA strongly object- ing to any change to the remedial action allowing a cleanup stan- dard less stringent than State or federal drinking water stan- dards. The Regional B08rd referred to the Cleanup and Abatement Order it issued to WJ in 1986 which required the company to at- tain approximately one-half the level of the present MCLs. The Regional Board urged a conservative approach in establishing cleanup levels due to the aquifer's designation as a sole source aquifer. 31 ------- 3. DHS commented that the California Environmental Quality Act (CEQA) should be included as an ARAR for the WJ site. . EPA ResDonse: EPA has determined that the requirements of CEQA are no more strinqent than the requirements for environmental review under CERCLA, as amended by SARA. Pursuant to the provisions of CERCLA, the NCP and other federal requirements, BPA's prescribed procedures for evaluation of environmental impacts, selectinq a remedial action with feasible mitiqation measures, and providinq for public review, are designed to ensure that the proposed ac- tion provides for the short-term and lonq-term protection of the environment and public health and hence perform the same function as and are substantially parallel to the State's requirements un- der CEQA. Since EPA has found that CERCLA, the NCP, and other federal requirements are no less strinqent than the requirements of CEQA, EPA has determined th~t CEQA is not an ARAR for this site. EPA will continue to cooperate with DHS and other State and federal aqencies durinq the desiqn phase of the remedial action i to clarify further environmental review and mitiqation require- ments and ensure that they are fulfilled. 33 ------- 'mi. t 11 Conct8lnlions at ConI."""".. 81 lite Walldu-Jobnson Sile a....I W*'.18IJL ..... z.e Rea'" Zone SaiI... CIIc8iI:II "'." ..... DaeaI' Mui- ~ Dacaa ....... Mc8 Daecu 0rp8Ia CIIIDnIfan8 7J1B.J 1.110' W 2JIE.J 5.2E~ 4/11 6.11.1 5.JE.2 619 1.:I.0iIM.......-. 4.8.' 1.710' 19M 7.sE" 4.8E.. 3181 ..... - NO' 1,4-Did11a1a11cuc88 IJE-' lJE.:J 15m - - NO - - NO I.I.~- 1.8-2 2JI6.:J W1] :J.IIE-J 5.ss.. 11/111 - - NO 1.I.Didlbc lit HI 1.11-2 1.I8.:J 23m 7.sE-J 1.2&" 14181 1".1 UE.2 If) .I.:I.~~ a 1111 T s.3B-2 5.1&-' :11M I.OE-J 'US" 22I1IJ 1...2 UB.2 1/1 _--tlc8e CIIIaridI - - NO ... - NO 1.1&.1 1.9£.0 1200 ~lr!T 2.S-2 4028-:J 13M 2.9E-2 9.1E" 14/11] 1.41.0 U&.I 419 I.I.I-~'_'- 4.36-2 2.18., 9M I.CIE-J 7.26.. 191111 ].1&.1 1.28.1 '4112 I.U.T.;.;Mo. t SJII.' 1.110' .em :J.IIE-' 5-SS.. 1/11] I.IIE.I U8.2 In Tr~-IJI't"_I, 5.5&-1 4.8-2 41M I.IE-I 9..] 42/11] UE.o 1.11.1 1114' V.,. 0IDridD . ......:1 IS' 11M - - NO - - ND ..... AnaIic 1.7&.2 11E.' 2/U _. - NO 1.4E.o I.4E.o 1/16 ..... 8.4&.1 11&.2 2W11 3.4E-2 1.]£.J 24m I.3E.' UE+' 16116 c:.IIai88 4.1&.3 UE.] 5Il1 1.4E-' UE" 3IJ2 6.21:.1 1.2E.1 4/16 ~ r ..&.:J 1:JE.2 11111 '.4E-2 '.2£.] 3IJ2 I.IE.I 6.9£.0 16116 Cana 2.1E.2 7.IIE.] 1111 1.4E-2 5.lE.] 1m 5.116.1 i.2E.' 16116 I..c:8I UE.:J S.2E.. IIU ... ... NO I.:JE+O ..6E.1 14/16 Matw1 2.CE~ 1.1&" 1111 2J1E.. 1.(1E-6 1m ... - NO NictcI :J.'l1-2 1.1&.2 91U 6.9£.2 7.9E.] 2fJ2 6.'lE+1 I.IE.I 14/16 Sma , 11-2 ",e.' 1111' 6.IE-2 9.4E.1 21n2 UE.o 'U£.o 1116 v..-. '.JB.2 2.9E., IIU 6.1E-] 2.1£.' 2/12 I.IE+I UE.o 1J/l6 II Zic 1.7&.0 '.IE.' III I 9.2E-1 I.1E.2 191JZ '.4E.1 U&.I 16116 I ........ .......... 2 TIll (.........,.........,.......... -............ . -nw. one........... 88... .. III I r I ...IJ ~ .".......,.. ....... .... M f ,.!v''''''''' ...... - ....... J """""""'''''''''''''''''''''''''''''''' . ............. . -~ I" :~..-: -::"="-". .~. :, - ~~ :_~, --- ~- >-: "} c_~ --~----~- .-:- ------- . i Tlbt. J \ I I Summary or Estimated Noncarcinogenic Risk at Watkins-Jobnson Site (Maximally Exposed Individual)l Exposed Population Route Medium Subchronic Chronic . Adult Residenrs Ingestion around Wiler 0.036 0.249 (Well in Perched Ingestion SoU 0.000 0.000 Zone)1 Dermal SoU ~ Q.Wl Total' 0.039 0.252 \ Child Residents Ingestion Ground Wasa 0.063 0.435 (Well in Perched Ingestion Soil 0.009 0.011 Zone) Dennal SoU ~ ~ Total 0.078 0.452 Adult Worker Ingestion around Wasa 0.018 0.134 (Well in Perched Ingestion Soil 0.001 0.002 Zone) Dermal SoU gmz 0Jm Total 0.021 0.138 Adult Residenrs Ingestion around War 0.041 0.245 (Well in Regional Ingestion Soil 0.002 0.002 Zone)' Denna1 SoU DJm. ~ Total 0.044 0.248 Child Residems Inpaioa Gmund Wifei' 0.0'72 0.428 (Wel in Regional Ingeslion SoU 0.009 0.011 Zone) Denna1 Soil QJDi QJDi ToW 0.087 0.445 Adult Worker Ingesdon Ground Water 0.021 0.149 (WeD in Regional Ingeaion Soil 0.001 0.002 Zone) Dennal SoU DJm QJm ToW 0.Q24 0.153 1 Bued on the upper.bound concenera6on ClQnwa. 2 Based on a hypothetical drinkinl water weD in &he perdted IDftL 3 All rOUIa. mediL ~ Bued on a hypotheticaJ drinkinl water weD in the nponal zane. ------- . Table 5 APPLICABLE OR RELEVANT AND APPROPRIATE REQUIREMENTS FOR THE WATKINS-JOHNSON SITE Standard, Requirement, Criteria. or Limitation DescriDtion Federal: Safe Drinking Water Act Use of MCLs and MCLGs as treatment standards for current or potential drinking water source. See Table 6. State: Air Resources Act Establishes allowable dis- \ charge standards for point sources within each air pollu- tion control district, and Am- bient air Quality Standards. Establishes state authority to clean up hazardous substance releases and compensate person injured by hazardous substances: es- tablishes state "Superfund". Hazardous Substances Account Act/Hazardous Substances Cleanup Bond Act California Safe Drinking Water Act Regulations and standards for public water systems: sets Maximum Contaminant Levels (HCLs) and Secondary MCLs (SHCLs) which are enforceable in California: requirements for water quality analyses and laboratories. porter-Cologne Water Quality Control Act Establishes authority for State and Regional Water Boards to determine site- specific discharge require- ments and to regulate disposal of waste to land. 1 ------- labl(' 6 FEDERAL AND STATE GROUNDYATER ARARS AND TREATMENT STANDARDS YATKINS-JOHNSON SUPERFUND SITE (expressed in milligrams per liter) Max halll Federal Federal CA-DHS CA-DHS DHS Appl i ed Treatment Chemical Detection ~1 MCl1 MCl Action level Action level Standard Organics 0.1003 ChlorofoMII 0.007 0.006 0.100 . 1,2-Dichlorobenzene 0.004 0.6002 0.6002 0.130 0.600 1,4-Dichlorobenzene* 0.008 0.015 0.015 0.005 0.005 1,1.Dichloroethane* 0.010 0.005 0.005 1,1-Oichloroethylene* 0.011 0.001 0.007 0.006 0.006 cis.1,2.dichloroethylene* 0.053 0.0702 0.0702 0.006 0.016 0.006 Methylene Chloride 0 0.005 0.040 0.005 Tetrachloroethylene* 0.029 0 0.0052 0.005 0.004 0.005 1,1,1.Trichloroethane 0.043 0.200 0.200 0.200 0.200 1,1,2.Trichloroethane 0.003 0.032 0.100 0.032 Trichloroethylene* 0.550 0 0.005 0.005 0.005 0.005 Vinyl Chloride* 0.006 0 0.002 0.0005 0.0005 Metals 0.0502 Arsenic 0.017 0.050 0.050 Sarhlll 0.140 5.0002 5.0002 1.000 1.000 Cachi l1li 0.0048 0.0052 0.0052 0.005 Chrcnillll 0.023 0.050 0.050 0.050 0.050 Copper 0.027 1.300 1.300 1.300 Lead 0.001 02 0.0052 0.005 Mercury 0.0002 0.0022 0.0022 0.002 Nickel 0.069 0.1005 SH ver* 0.061 0.050 0.050 0.050 V8n8di l1li 0.013 Zinc 1.700 5.0004 5.000 NOTES: * . MaxillUl detection exceeded the treatment goal. 1 . Safe Drinking Yater Act (~), 42 U.S.C. Section 3OO(f) 2 . Proposed value (CFR Vol. 54, No. 97, p. 22064, May 22, 1989). 3 . Drinking water ~al ity standard for total trihalomethanes. 4 . Secondary Federal MCl. 5 . EPA Health Advisory. 6 -. Proposed value, State of Cal i fomia. u. No value available. ------- . TABLE 8 WATKINS-JOHNSON WATER OSE RATES Fourth Quarter 1989 t'OTAL GPH EXTRaCTED !'eTAL UK Donn o.-aID TOTAL GPH REINJECTED. TOTAL GPK DISCHARGED TO CREEK . REINJECTING INTO ONE LEACHFIELD POTORE PROJECTED DATA TOTAL GPK EXTRACTED TOTAL GPK REOSED ON-SITE TOTAL GPH REINJECTED. TOTAL GPK DISCHARGED TO CREBK . REINJECTING INTO '1'HREE LBACBPIELD8 15 an aPK = Gallon. per Xinute 101 37 or 18\ 15 or 7\ 157 or 75\ \ 110 37 or 34\ 45 or 42' 25 or 24' ------- |