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HomeMy WebLinkAboutMITIGATION 1997 c;!fqll&(;C§£-Ofld{¿nCtt::-fl1 flncz, ,,, '" 'i Groundwater SCIentists · EnvIronmental Consultants . SITE ASSESSMENT REPORT ADDENDUM BAKERSFIELD MUNICIPAL AIRPORT 2000 South Union Avenue Bakersfield, California Presented To: City of Bakersfield Public Works Department 1501 Truxtun Avenue Bakersfield, California 93301 -. Presented By: AquaGeosciences, Inc. November 1997 Timothy C. Reed, R. G. #5999 Project Geologist Philip Goa in, R.G. #4779 Principal Hydrogeologist Registration Expires 11/30/98 . 6851 McDivitt Drive, Suite D · Bakersfield, Caifornia 93313 (805) 836-8100 · FAX (805) 836-8800 (800) 301-4244 . . . TABLE OF CONTENTS 1.0 INTRODUCTION. ............ ..... .... .......... ..................... .......... ..... ....... ....... 1 2.0 BACKGROUN D.. .................... ........... .................................... ............... 1 3.0 GEOLOGY AND HyDROGEOLOGy............................ ............. ............. 3 4.0 REVISED HEALTH RISK ASSESSMENT............................................. 3 4.1 ASTM RBCA MODEL.. ...........................,................... '............ ............... ..... ........... ........... ........ .....3 4.2 MODEL INPUT PARAMETERS ................... ................., ..... ............... .... ....... ............. ...... ........ ......... ...4 4.3 RESULTS OF RBCA MODEL. ..... .......... '..... ,.......... .....,.. '. .... ....,.... ..,.................................................5 5.0 CONCLUSIONS AND RECOMMENDATIONS .....................................6 5.1 CONCLUSiONS................................................ ............,.................,.,.............................................6 5.2 RECOMMENDATIONS..............................,...................,...................,.......,.,................................ .....7 6.0 LIMITATIONS..... ....... ............ ................. ..................... .........................7 EXHIBITS Exhibit 1 Exhibit 2 Exhibit 3 Exhibit 4 Exhibit 5 Vicinity Map Site Plot Plan Boring Locations Lithologic Cross Section with Benzene Contours Lithologic Cross Section with TPHg Contours APPENDICES Appendix A RBCA Fate/Transport Health Risk Assessment Summary Report II . 1.0 INTRODUCTION This report is an addendum to the July 15, 1997 Site Assessment Report which documented the procedures, findings, conclusions and recommendations from an environmental assessment performed by AquaGeosciences, Inc. (AGI) at the Bakersfield Municipal Airport, located at 2000 South Union Avenue, in Bakersfield (Exhibit 1). This addendum presents the results of a revised risk assessment performed for the site and draws conclusions and makes recommendations based on the revision. 2.0 BACKGROUND On or about November 5, 1996, two (2) 10,000 gallon underground fuel storage tanks (UST's), associated piping and electrical connections were removed from the subject property. Approximately 11 soil samples were analyzed for Total Petroleum Hydrocarbons (TPHg) as aviation fuel and volatile aromatics (BTEX). Additionally, a soil sample collected from the stockpiled soil was analyzed for CAM 17 metals, The analytical results indicated that high concentrations of TPH and BTEX were detected at the southern end of both 10,000 gallon UST's and moderate concentrations of TPH and BTEX were detected in the six foot sample collected beneath the dispenser. The results of the metals analysis indicated that no CAM 17 metals were detected in the samples submitted. . On May 27, 1997, AGI advanced three borings, designated TH-1, TH-2 and TH-3, to depths of 120 feet, 135 feet and 90 feet, respectively (Exhibit 2-3). Elevated field indicators of hydrocarbons were detected from 5 feet 135 feet. Each boring was sampled at five foot intervals. All borings were advanced until field screening indicated that hydrocarbon levels were below detection or at very low levels. The results of the laboratory analyses are presented on Table 1. At this point in time, the vertical extent of gasoline impacted soils have been defined, Gasoline hydrocarbons occur from approximately 5 feet to below grade to approximately 140 feet. The first occurrence of groundwater at the site is documented to be 200 feet below grade. Groundwater is not expected to be impacted at this time, The lateral extent of the gasoline plume in the soil has been estimated to have a radius of approximately 65 feet centered between the south end of the tanks and the dispenser location. A cross section showing the vertical extent of the benzene and TPHg plume are presented on Exhibits 4-5. . A health based risk assessment was completed for the site to determine whether the soil plume would pose a risk to public health and safety. The model used very conservative (tend to over estimate risk) parameters as is customary when using risk assessment screening models. The results of the risk assessment indicated that, based on the input parameters, a potential risk to public health was calculated from air and groundwater exposure. Based on this data, AGI recommended remediation of the soil plume to levels that would no longer pose a risk to public health. 1 . Upon review of the Site Assessment Report, the Bakersfield City Fire Department Office of Environmental Services, requested that the risk assessment be performed using more site specific parameters. This request was made based on the depth to groundwater at the site, relatively low TPHg concentrations and site paving. AGI has agreed to prepare a new risk assessment using more site specific parameters to determine whether the site would pass the risk assessment and provide a margin of confidence that the soil plume would not pose a risk to public health and safety. The results of the revised risk assessment are provided in this addendum. TABLE 1 SOIL SAMPLE ANALYTICAL RESULTS BAKERSFIELD MUNICIPAL AIRPORT Bakersfield, California Ethyl- Total TPH Depth Benzene Toluene benzene Xylene (gasoline) Sample I.D. (feet) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) TH 1-15 15 3.0 5.5 0,9 1.7 5.1 TH 1-30 30 8.3 18.5 1.5 5.7 5.0 TH 1-45 45 18.8 32.1 5.3 15.5 5.0 TH 1-60 60 3.1 0.7 0.2 1.4 6.2 TH 1-75 75 20.6 27.3 17.2 36.8 1204 TH 1-90 90 30 40 22 50 2438 TH1-105 105 5.0 13.0 3,0 11.0 244 TH1-115 115 0.1 3.5 0.3 1.5 f\D . TH1-120 120 0.05 0.05 0.005 0.04 f\D TH2-10 10 2.6 3.7 1.1 1.9 5.0 TH2-25 25 2.3 5.2 1.0 2.3 68.0 TH2-40 40 1,8 4.8 1.0 2.1 46.3 TH2-55 55 1 . 1 2.4 0.6 1.0 8.4 TH2-70 70 8.4 15.7 10.9 27.9 69.7 TH2·85 85 14.8 4.0 0.71 4,9 8.6 TH2-100 100 1 .1 3.2 0.14 0.81 5,6 TH2-120 120 1.2 3.6 f\D 3.6 30,3 TH2-130 130 6.0 14.4 8.0 25.5 339 TH2-135 135 2.9 7.7 0.2 11 .1 130 TH3-20 20 1.2 2,8 f\D 2.0 21.4 TH3-35 35 2.2 6.6 0.23 3.6 113.0 TH3-50 50 1.5 4.7 1.0 2.7 46.0 TH3-65 65 0,86 0.25 0,13 0.57 5.6 TH3-80 80 0.82 0.26 0.10 0.65 5.7 TH3-85 85 1 .1 0.33 0.12 0.61 5.6 TH3-90 90 0.93 0.28 0.11 0.68 5.6 Analytical Method: BTEX - EPA Method 5030/8020, TPHg - Calif. LUFT Manual Results in milligrams per kilogram (mg/kg) = parts per million (ppm) ND= Not Detected - Below laboratory detection limit Detection Limits - BTEX = 0.005 mg/kg; TPHg = 5.0 mg/kg . 2 . . . 3.0 GEOLOGY AND HYDROGEOLOGY According to the Geological Map of California Bakersfield Sheet published by the California Division of Mines and Geology, the unconsolidated soils encountered in the general vicinity of the site are Pleistocene non-marine flood-plain deposits, consisting of brown to reddish brown silty sands and sand, interbedded with scattered sandy silt layers', Soils encountered during drilling and sampling operations consisted primarily of fine to coarse grained, poorly to well sorted sands and silty sands with occasional silt intervals. Published data from the Kern Water Agency show that the average depth to groundwater in the site vicinity approaches 200 feet below the ground surface and has a regional gradient to the south and southeasf, 4.0 REVISED HEALTH RISK ASSESSMENT The following risk assessment, employing a fate/transport and health risk model, was prepared to evaluate whether the soil contaminant plume at the site could pose a threat to public health and safety, 4. 1 ASTM RBCA Model In order to determine whether the soil hydrocarbon plume could pose a threat to public health and safety, a risk assessment employing a fate/transport and health risk model has been prepared. This model utilized Tier 2 of the Risk-Based Corrective Action (RBCA) planning process, as described in ASTM E-1739 "Standard Guide for Risk- based Corrective Action Applied at Petroleum Release Sites." RBCA was chosen because it integrates EPA risk assessment practices with traditional site investigation and remedy selection activities in order to determine cost-effective measures for protection of human health and environmental resources, Consistent with EPA risk assessment protocol, the RBCA Tier 2 evaluation addresses source zone cleanup standards that will protect against chronic health or environmental impacts, i,e. carcinogenic or toxic effects caused by long-term exposure to low levels of contaminants. Upon review of the data collected to date and the guidelines set forth in the RBCA documentation, this site has been classified as Class 3, A Class 3 site ,is described as having a potential long-term (>2 years) threat to human health, safety, or sensitive environmental receptors. This classification is based on the criteria that the soil is impacted and hydrocarbon migration to a potable water supply is greater than two years travel time, I California Division of Mines and Geology, 1964, Geologic Map of California, Bakersfield Sheet. , Kern County Water Agency, 1996, Water Supply Report 3 . . . 4.2 Model Input Parameters Pursuant to a request by the Bakersfield City Fire Department, Environmental Services Department, the input parameters for the RBCA Tier 2 model presented in the July 1997 report have been revised to reflect less conservative and more site specific conditions, The results of the modeling, along with the input parameters, are presented in the Summary Report in Appendix A. As in the original model, the groundwater plume was modeled for benzene, toluene, ethylbenzene and xylene (BTEX). The subsurface soil plume was modeled using the soil boring data collected in May 1997. The results of the soil analysis are presented on Table 1. The model was recalculated using the assumption that the entire plume contains a concentration for each COC equal to the 90% upper confidence limit (UCL) rather than the maximum values of the analyzed samples. This equals a UCL value of 3.3 mg/kg for benzene, 5.2 mg/kg for toluene, 1.1 mg/kg for ethylbenzene, and 4.3 mg/kg for xylene. This represents a slight decrease in estimated plume concentrations from the previous model. Since benzene is classified as a Class A carcinogen, a target risk factor of one in one million (1.0E-6) was selected for this component. The other components are listed as Class D toxins, therefore a target risk factor of 1,OE-5 was selected. Since groundwater velocity can not be directly measured without the performance of a complete aquifer pump test, the hydraulic conductivity of the soil has been estimated using standard hydrogeology references. As in the previous model, a value for the hydraulic conductivity was selected that would represent a medium to coarse sand. A hydraulic conductivity of 10 meters per day is estimated for this soil type3. The groundwater gradient also could not be directly measured, therefor, an estimated gradient of 0.004 ft/ft was used based on the regional gradient. Using these parameters, the groundwater transport velocity was estimated at approximately 126 feet per year. The aerial extent of the soil plume was estimated at 13,300 ft2. . For the air exposure pathway the distance to the nearest receptor was modified from 100 feet to 200 feet, which is the approximate distance from the plume to the nearby restaurant. This distance is used to calculate the dispersion factor. The air pathway was modeled for commercial exposure. All input variables used in the model are presented in Output Table 1 located in the Summary Report in Appendix A. A groundwater production well has been identified in the vicinity of the soil plume. This well is located approximately 500 feet north of the former tank location. However, this well is located upgradient from the soil plume. For the purpose of this model, it will be assumed that there is a well 1500 feet downgradient of the site and screened in the unconfined aquifer. This presents a fairly conservative risk assessment of the site since there are no known groundwater wells downgradient of the site within 2000 feet of the soil plume. Potential groundwater plume transport was modeled using the Domenico analytical model with dispersion and first-order decay coefficients for each constituent. The CAL/EPA recommended Oral Slope Factor of 0.1 kg-day/mg for benzene was used in the model. The Oral Reference Dose for the other constituents are referenced in the Driscoll. F.G., Groundwater and Wells, Johnson Division, 51. Paul, MN. 4 . RBCA Chemical Database section of Appendix A. For a complete list of the model input parameters, refer to Output Table 1 and Input Screen 7, 9.1 and 9.4 of the Summary Report in Appendix A. 4.3 Results of RBCA Model In order to calculate the cancer risk to an off-site receptor, the total carcinogenic and toxicant intake rate was calculated for each exposure pathway. The possible exposure pathways are: vapor and dust inhalation of surface soils, vapor inhalation from subsurface soils, dermal contact from surface soils, ingestion of surface soils, ingestion of groundwater potentially impacted by contaminants leaching from the soil, vapor inhalation from groundwater, and direct ingestion of groundwater. Since the source of the hydrocarbons were leaking underground tanks, soil contamination is estimated to occur a minimum of three feet below grade. Therefore, vapor and dust inhalation and dermal contact from surface soils were not modeled. The primary exposure pathways were modeled using the off-site residential ingestion of groundwater potentially impacted by contaminants leaching from the soil, and commercial on-site inhalation of vapors from the subsurface, . The maximum pathway intake concentrations for each contaminant of concern (COC) were calculated for each exposure pathway, These results are presented on Worksheet 8.1. The intake concentrations were then used to determine the risk from each COC for each pathway modeled. As shown on Worksheet 8.3, the pathway showing a risk factor was from air exposure, The highest calculated risk factor was 1.8E-5 for air exposure to benzene, compared to the target risk of 1.0E-6. The hazard quotient for air exposure from the other constituents was 3,OE-1, an order of magnitude lower than the target risk of 1.0E+O. The calculated risk for groundwater exposure was 2.3E-7 for benzene, which is less than the target risk factor of 1.0E-6, The hazard index for groundwater was 2,3E-8, which is several orders of magnitude less that the hazard limit of 1.0E+O. The output of the model was used to determine the Site-Specific Target Levels (SSTL) for each COCo The SSTL would be the projected cleanup level for the site in order not to exceed the desired target risk factor or regulatory exposure levels. The model was programmed to compare the calculated exposure levels to the regulatory Maximum Contaminate Level (MCL) for groundwater exposure and the Permissible Exposure Limits (PEL) for air exposure. As shown on Worksheet 9.2 in Appendix A, the revised calculated SSTLs, for the subsurface soil would be 1.5E+ 1 mg/kg to meet the 1.0E-6 cancer risk and 8,6E+ 1 mg/kg to meet the MCL for benzene. This is greater than the estimated plume concentration of 3.3 mg/kg, indicating that the cleanup level has been attained to meet both the target risk factor and the MCL. The cleanup levels for the other constituents are above the residual saturation concentration for soil. The SSTL for air exposure is less than the target risk factor of 1.0E-6 but is greater than the PEL. The risk values for the other constituents are greater than the residual concentration for soil in order to meet the PEL at the calculated point of exposure. . 5 5.0 CONCLUSIONS AND RECOMMENDATIONS · 5.1 Conclusions · As shown on Exhibits 3-4, contouring of the TPHg and Benzene soil plumes shows that both plumes are asymmetrical and skewed to the south in the vicinity of TH-2. It appears that the dimensions of the hydrocarbon plume are lithologically controlled. Generally, with the exception of the central portion of the plume, the samples collected in silty sand and silt layers contain higher concentrations of hydrocarbons, Minor amounts of BTEX and TPHg concentrations, in the 135 foot sample in TH-2, indicate that the plume may extend slightly beyond 135 feet, however, the analysis from TH-1, in the center of the plume, indicates a plume depth less than 120 feet. The results from TH-3 exhibited lower overall concentrations and were first detected at a greater depth. This would indicate that TH-3 was at the edge of the soil plume. Although the vertical extent of the plume was not reached at TH-2, it is AGI's opinion that the hydrocarbon plume does not extend significantly past a depth of 135 feet. Assuming that the lateral extent of the plume is relatively symmetrical, the area of soil contamination is estimated at 13,300 square feet. The results of the risk assessment show that, based on California and EPA risk guidelines, the remaining hydrocarbons in the soil may pose a potential health risk from the inhalation of vapors. However, when compared the PEL limits stipulated by OSHA, the projected concentrations for benzene, at the assumed points of exposure for air, have not been exceeded. The risk from groundwater exposure is less than the target risk value of 1.0E-6 and the California MCL for benzene. The toxic effect from the other constituents is minimal. This indicates that although there is a calculated health risk from exposure to vapors, the actual concentrations at the point of exposure will be less than the standard exposure limits stipulated by state or federal regulations. The model does not account for surface vapor barriers such as asphalt paving. Therefore, the actual vapor exposure is expected to be less since the site is entirely paved. The calculations were based on the estimated plume size, the average concentrations determined from the site assessment, and the proximity to a nearby downgradient drinking water well, located at a distance at or greater than 1500 feet from the hydrocarbon plume. Based on the information acquired at the site, the following can be concluded: . The vertical extent of gasoline impacted soils at the site has been assessed. Impacted soils extend from approximately five feet below grade to approximately 140 feet below grade. The highest gasoline concentrations occur in the soil beneath the point of release, the under ground tanks, at a depth of 75 to 100 feet; . The lateral extent of gasoline impacted soil has been assessed with an estimated plume diameter of approximately 130 feet; · 6 . · The depth to groundwater at the site is documented to be 200 feet below grade, Therefore, it is unlikely that groundwater has been impacted at the site; · The results of the RBCA fate/transport and health risk assessment indicate that any possible health risk due to the ingestion of groundwater is less than the target risk of one-in-one million. · The results of the RBCA fate/transport and health risk assessment indicate that a potential risk to public health may exist for exposure to vapors, however, the calculated concentrations for vapor at the calculated point of exposure are less than the PEL for each constituent. In addition, the model does not account for surface paving. Although the risk from vapor exposure cannot be quantified in light of the asphalt cap over the soil plume, the actual risk is expected to be much lower due to the presence of asphalt paving and the conservative nature of the model. The actual risk to public health and safety through exposure to vapors is expected to be negligible, · This model assumes that the direction of flow at the site will remain to the south. Extensive pumping of the municipal well located 500 feet north of the site could affect the direction of groundwater flow at the site. 5.2 Recommendations . Based on the results of the site assessment, no further characterization of the site is recommended. Furthermore, the revised risk assessment indicates that the MCL and PEL will not be exceeded at a calculated point of exposure of 200 feet for vapor and 1500 feet for groundwater exposure. Due to specific site parameters such as depth to water, surface paving, groundwater flow direction, the distance to possible receptors, and the conservative nature of the RBCA model, it is AGI's opinion that the risk to public health and safety is acceptable. Therefore, no further action is recommended for this site. Since the source of hydrocarbons (tanks) have been removed, the soil plume should be allowed to degrade through diffusion and natural microbial action. Natural occurring bacteria will degrade a soil plume with time. 6.0 LIMITATIONS AGI performed this investigation in accordance with the generally accepted standards of care which exist in California at this time. It should be recognized that definition and evaluation of geologic conditions is a difficult and inexact science. Judgments leading to conclusions and recommendations are generally made with limited knowledge of subsurface conditions present. No warranty, expressed or implied, is made. . 7 . EXHIBITS . . . .----.- \f' ... ~~ DRIVE' 385 --- ._~ . . -"..::,',:",,,.~,::,~,, ':::\' .".,.."".,,""'~-:.:~:'- !: "qes '-::~ " \';}'\ : (.' .. =:f3R,eserVOlt'~",~~~Qj} o . G1: ..,}'~ ":/ g --~ :;) ~.. .. ., . Z Q " . '-"/ . e' Ù W~' ~. -..-..--....... :: .~ ~"O -: .. -... ..-- (.). , ~:: ............-. " .~ .. : ~R servorr -- I:: I:: I,;':' ~~~\. -EJ' ",', ".,," .. " " .17 :. ~ii jt ¡Irdl \\ : '~..\\ WHITE , ~NE.... ~~~ ~, '-<:<\ ' ',II', . J'>O ~,c~~{,~ . \Y" ... c _'~~~~,~:,,_,.,_-_._--_.- ,-- ..- I :=" -.----..----. -- ...."' . I . "'~~~:;:" : : ¡ / 0 PACHECO RD "~~~" ReservOIro " ...... ~ - - :.' -...-....- ." ..........- :: '1.~8.:" ;~ - - - / fi65 .. :.. .........:: . . . \\~¡¡ .. .... ... ..-.." ~;I='t . .¡ ~ .: Lß[~, :~~~:::::~ ::~:·H=i=======- 8M j6~ :. o. ....... . ti~ '. I._...t" " " " . ;::~ . "?å k'~' :1;. S \111-:'..-20 H~ ,.. ~ ~H~'I cr¡.....'~.,> CI . . " ."". " -. ......... " ........ " _,11 ~IP¡' LINE " :: . . R.Q;'1 (~n.>tmfìt...j.d . III:;.. Jr High ~l'Ì1 . J '- / / ..]-"0_ Sch j... ) L. ,. J~8 , 1i~ r il." ï u I": ~,,=,,= II 19 ROAD I. Map Scale: 1" = 2000' Map Source: USGS 7.5 min. Topographic Map, Lamont (1973) and Gostord (1973) Quadrangle AquaGeosciences, Inc. 4440 Grisson St., Suite 100 Bakersfield, California 93313 EXHIBIT BAKERSFIELD MUNICIPAL AIRPORT 2000 South Union Avenue Bakersfiled, California 1 Telephone: (805) 836-8100 Fax: (805) 836-8800 VICINITY MAP I --:.'( ~ ---- ----- D ---¡ I I I I I I I I I I I I I I I I I I I I I I ------- ,/ ,/ ,/ Q) > ï: C ( ) - - ro ~ TH,3 ~ FORMER UNDERGROUND STORAGE TANK LOCATIONS . FORMER DISPENSERS 00 () ~J____ d South Union Avenue ** Map Not to Scale AQUA GEOSCIENCES, INC. . 4440 GRISSOM STREET, SUITE 100 BAKERSFIELD, CALIFORNIA 93313 PHONE: (805) 836-8100 FAX: (805) 836-8800 BAKERSFIELD MUNICIPAL AIRPORT 2000 South Union Avenue Bakersfield, California EXHIBIT 2 PLOT PLAN ~ 9{ ~ Estimated TPHg Plume Boundary at 5.0 ppm LEGEND ~ Boring Location A - AI Line of Section i l 1 Former Edge of rmp Island \\ .~ " o 1 0 20 30 r"""'_ I Scale (feet) AI " Estimated Benzene Plume Boundary at 1 .0 ppm BAKERSFIELD MUNICIPAL AIRPORT EXHIBIT 2000 South Union Avenue Bakersfield, California 3 BORING LOCATIONS AQUA GEOSCIENCES, INC. . 4440 GRISSOM STREET, SUITE 100 BAKERSFIELD. CALIFORNIA 93313 PHONE: (805) 836-8100 FAX: (805) 836-8800 70 20,6/1204 . 80 90 A ~~(), Former Dispenser ~~' ~~n;, AI SW Location NE Depth 10 2. /5.0 3.0/5.1 20 ...:.:::: :':.:·:.:·:::·:::·~::·:~·;~·:~~~~:!~!f&&~fJf!~ti8~~1!::~:t\*~ ¡~~t¡.t }P,t~ti}.:~p&¡~!::~:::~~:~::1: 1.5/46.0 110 LEGEND Sand (SP-SW) Silty Sand (SM) Silt (ML) Clay (CL) Benzene/TPHg 5.0/244 Concentrations (ppm) o 5 1 0 20 120 140 - ~ - Scale (feet) Horiz. = Vert. -.?--- . AQUA GEOSCIENCES, INC. 4440 GRISSOM STREET, SUITE 1 00 BAKERSFIELD, CALIFORNIA 93313 PHONE: (805) 836-8100 FAX: (805) 836-8800 BAKERSFIELD MUNICIPAL AIRPORT 2000 South Union Avenue Bakersfield, California EXHIBIT 4 LITHOLOGIC CROSS SECTION WITH BENZENE CONTOURS A -<..~ f\, Former Dispenser -<..~ "- -<..~n;, AI SW Location NE Depth 10 Location 3.0/5.1 20 70 . 80 90 110 D . III Ë3 5.0/244 140 /'1. ';) . . . <1. ~.~ ? - - . 0.86/5. LEGEND Sand (SP-SW) Silty Sand (SM) Silt (ML) Clay (CL) BenzenefTPHg Concentrations (ppm) o 5 10 20 Scale (feet) Horiz. = Vert, EXHIBIT AQUA GEOSCIENCES, INC. 4440 GRISSOM STREET, SUITE 100 . BAKERSFIELD, CALIFORNIA 93313 PHONE: (805) 836-8100 FAX: (805) 836-8800 BAKERSFIELD MUNICIPAL AIRPORT 2000 South Union Avenue Bakersfield, California 5 LITHOLOGIC CROSS SECTION WITH TPHg CONTOURS . APPENDIX A RBCA FatelTransport Health Risk Assessment Summary Report . . . - . . .. ! -" . RBCA S!TE AS!:! . Tier 2 Worksheet 8.1 ___J:>~~ Name: City of Bakersfield Site Location: Bakersfield Muni, Airport Completed By: Tim Reed TIER 2 EXPOSURE CONCENTRATION AND INTAKE CALCULATION Date Completed: 11/10/1997 50F6 ~IUNDWATER EXPOSURE PATHWAYS . (CHECKED IF PATHWAY IS ACTIVE) SOIL: LEACHING TO GROUNDWATERI Exposure Concentration INGESTION 1) Source Medium 2) NAF V',lue ILlka) ~~.~~E.?S,U~~~9.i~r:n\ 4) EXDosure Multiolier 5) Averaqe Dailv Intake Rate .....'~~. "::T~I Ree,·:::ptor (1)/(2) (IR.EF.ED)/(OW.A T) (Ukg·day) (mglkg'day) Constituents of Concern SOIl Conc",nrr,JJ!on ImlJ'KEL- -- Of ,S'le Resldi:nl!aJ CtI·S¡ e Resídelì!¡a) OIl·Site Res¡den ¡aJ OIl-Site Residential Benzene 3,3E+0 I 1,7E+4 1,9E,4 1,2E,2 2,3E,6 Ithylbenze~____~__ 1.1E+0 ¡ 1,6E+7 7,3E,8 2,7E,2 ~.r9__, .-. ~----"- I ---- - ._-~- ---- ~~. n.___ ._~--- Toluene ---S2-Ë 10 ---- I ~E-:'19--· 3,7E~- - '-mn---- 1,OE-20 ~~~;;e( mixedlsomersj'--=:: ---, ---- ._.~--- ----"4:3"E.;.Ü---- .--. ---_..-- I -2:21'.+7 ..-. --.------ ... -- .-..- .-. - Tof:-i-- --- ---~_._-----,- ---2.7E,~ ~-~- ~55E'9 - -~-- --~-- ~-~- [ NOTE: AT = Averaging time (days) BW = Body Weigh! (kg) CF = Units conversion faclor ED = E.p, duration (yrs) EF = Exposure Irequencey (days/yr) IR = Intake rate (Uday) POE = Point 01 exposure Serial: G·249,WHX,220 Software: GS! RBCA Spreadsheet Version: v 1.0 @ Groundwater Services. Inc. (GSI). J 995. AH Rights Reserved. . . 'r!'- , ''''. ~, - SitE: NamE:: Cily of Bakersfield 1 A , " : I ' , , f!BC~ SITE AS~ESSMEN Completed By: Tim Reed ~f\OUNDv'/ATER EXPOSURE PATHWAYS Site Location: Baker:olield Muni. Airport GROUNDWATER: INGESTION Exposure Concentration TIER 2 EXPOSURE CONCENTRATION AND INTAKE CALCULATION . (CHECKED IF PATHWAY IS ACTIVE} 1) Source Medium Groundwater Constituents of Concern Concentration (m9.1:l Benzene O,OE+O !'lhylbenzEJ~_____ __2:º~_ Toluene O,OE+O ~:Yi.Ei.nËij!!!lXe(jTsõ~ñ~~~[~,-:'=-~ w ºöjEº~_'_ ,-- NOTE: AT; Averaging time (days) 2\ NAF Value (dim) Receptor ------ Off,Sile Residential 1,OE+4 4.2E+6 -.--- --- 2.8E~~·~ ", __n23~+~=___- "u_~_ --~- . Tier 2 Worksheet 8,1 60F6 Date Com feted: 11/10/1997 5\ AveraQe Dailv Inlake Rale (mglkg'day) Off,Sile Residential O,OE+O ____~~~+O_ O.OE+O _==_==-~9E+0 BW" Body Weight (kg) CF =: Units conversion factor ED " Exp, duration (yrs) EF; Exposure IreQuencey (days/yr) IR; In/ake rate (Uday or mg/day) MAX, PATHWAY INTAKE (mglkg-day) (Maximum Întake of active pathway:.; soil leaching & groundwater routes.) Off, Site Residential 2,3E'6 2,OE,9 1,OE,20 -s-:5E=9- __ u. ____ n. _ _______n ______ ~_____ ---- ------ _.-'--~._----------'----~-~----~- POE ; Point of exposure © Groundwater Services, Ine, (GSI), 1995, All Rlghls Reserved, 3) Exoosure Medium Gr ,1H1( ·.·..itI8r rOE COliC. (mUlL) (1)f(2) 4) Exoosure Multlo\i"~r IlRx[FxED)/{BWxAT) (lJk J day) ----.---- -. Oft,Sile Oll'Sile Residential Res dential O,OE+O 1,:2E,2 OOE+O 2.7E,2 ~----== ~=]]tg-_~~ .-"u -=~gt;-~ Serial: G,249,WHX,220 - Software: GSI RBCA Spreadsheet Version: v 1.0 . . . , ':' ~BCA SITE ASS~SSME :,¡. . _,',. 'fGlt1:.~{ (If;~ J, ' .,,' I&! #. :r ". ~,.~" - '. I Tier 2 Worksheet 8.2 ____~'!."~ame~_º~ì' of Bakersfield Site Location: IJakersfield Muni. Airport Completed By: Tim Reed TIER 2 PATHWAY RISK CALCULATION Date Com leted: 11/10/1997 30F3 ~NDWATER EXPOSURE PATHWAYS . (CHECKED IF PATHWAYS ARE ACTIVE) CARCINOGENIC RISK TOXIC EFFECTS (2) Total Carcinogenic I (3) Oral (4) Individual COC (5) TNal Toxicant (6) Oral (7) Individual cae (11 EPA Intake Rate (mgikgiday) Slope Factor Risk (2) x (3) Inlake Rilte (mgikgiday) Reference Dose Hazard Quotient (5) I (6) Carcinogeni c Classificat Off, Site Off,Site Off,Site Off,Si!e Constituents of Concern ion Residential lIT! Ika-daY)^-1 Residential Residential (mQ/kq'davl Residential Benzene A 23E,6 1,OE,1 2.3E,7 Ethylbenzene D 2,OE,9 1,OE,1 2,OE,8 Toluene D 1,OE,20 2,OE,1 5,1E,20 ~ylene (mixed isomers) D 5,5E,9 2.0E+O 2,8E-9 Total Pathway Carcinogenic Risk = O,OE+O 2,3E-7 Total Pathway Hazard Index = O.OE+O 2,3E-8 I__~_- -----_._--~-_.- --- ~-~-~~--- Serial: G,249,WHX,220 Soffware: GSI RBCA Spreadsheet Version: v 1.0 © Groundwater Services, InG I(51), 1995. All Rights Reserved. . I~ Site Name: City of Bakersfield Site Location: Bakersfield Muni. Airport BASELINE Individual COC Ris EXPOSURE Maximum Target PATHWAY Value Risk AIR EXPOSURE PATHWAYS Complete: I 1.8E-5 1.0E-6 . . . - ,'~ ¥', "'~,: ~ <#" "'~~ )."H' 'rlftà\., ,~~ \ ~ "'<f' ·MEMT, .' ·ì ; ~ ,,, . , . Tier 2 Worksheet 8.3 Completed By: Tim Reed Date Completed: 11/10/1997 TIER 2 BASELINE RISK SUMMARY TABLE CARCINOGENIC RISK BASELINE TOXIC EFFECTS Risk Limit(s) coe Risk Exceeded? Target Risl< 1 of 1 Toxicity Limit(s) Exceeded? Cumulative Total Value Hazard Quotient Maximum Applicable Value Limit Hazard Index Total ,Applicable Value Limit 1.8E-5 N/A . D 3.0E-1 1.0E+O 3.1E-1, N/A GROUNDWATER EXPOSURE PATHWAYS Complete: I 2.3E-7 1.0E-61 2.3E-7 SOIL EXPOSURE PA THWA YS Complete: O.OE+O 1.0E-6 O.OE+O 1.0E+O N/A I.J I 2.0E-8 2.3E-8 N/A CJ 1.0E+O N/A o N/A o O.OE+O O,OE+O CRITICAL EXPOSURE PATHWAY (Select Maximum Values From Complete Pathways) u" 1 1.8E-5 : 1.0E-611.8E-5 N/A 1- . -I 3,OE-1 I 1.0E+O 1 3.1 E-1 -\'. N/A -';- Serial: G-249-WHX Software: GSI RBCA Spreadsheet Version: v 1,0 © Groundwater Services, Inc. (GSI), 1995. All Rights Reserved. . . Site Narne: City of Bakersfield Site Location: Bakersfield Muni. Airport , ... , ' RBCA S!TE AS~J:SSM . T "'ít,.-;! (". ' , ' <--;: 'J"". . , Jf>" ': SUBSURFACE SOIL SSTL VALUES (> 3 FT BGS) Representative Concentration CONSTITUENTS OF CONCERN I ì I CAS No. ' Name 71-43-2 Benzene 100-41·4 Ethylbenzene 108-88-3 ' Toluene ####### Xylene (mixed isomers) (rng/kg) 3,3E+0 1,1 E+O 5.2E+0 4.3E+0 - Cornpleted By: Tim Reed Date Cornpleted: 11/10/1997 Target Risk (Class A & B) 1,OE,6 Target Risk (Class C) 1,OE,5 Target Hazard Ouotient 1,OE+0 SSTL Results For Complete Exposure Pathways ("x" if Complete) X Soil Leaching to Groundwater Residential: Cornmercial: Regulatory(MCL 1500 feet (on,site) ): 1500 feet 1 .5E+ 1 NA 8.6E+ 1 >Res NA >Res >Res NA >Res >Res NA >Res © Groundwater Services, Inc, (GSf), 1995, All Ri( hts Reserved, . MCL exposure limit? II PEL exposure limit" Soil Volatilization to Indoor Air Residential: (on,site) (on,site) (PEL) NA NA NA NA NA NA NA NA Soil Volatilization to , X , Outdoor Air Residential: (PEL) (on, (on,site) site) NA >Res NA >Res NA >Res NA >Res Software: GSI RBCA Spreadsheet Version: v 1,0 . Tier 2 Worksheet 9.2 1 OF 1 Calculation Option: 2 I SSTL Applicable ,Exceede SSTL d ? Required CRF i (rng/kg) "." If yes, Only if "yes" left~ 8.6E+ 1 U i <1 i I >Res U' <1 >Res U <1 >Res U <1 I ¡ Ii I ' Serial: G,249-WHX,220 OUIPu"able 1 -- Site Name: Clly of Bakersfield Software: GSI RBCA Spreadsheet Job Identification: Site Locat¡on: Bakersfield Munl. Airport Dale Complete'j: 11/10/97 Version: v 1.0 Completed B¡ Tim Reed NOTE: values which differ Irom Tier 1 delault values are shown in bold italics and underlined, DEFAUL T PARAMETERS ExposurE' Residential ,- Commercial/Industrial Surface Commercial/Industrial E~rameter Definition (Units) Adult (1,6yrs) -11-16 yrs) Chronic Constrctn Parameters Definition (Units) Residential Chronic Construction ÄTc Äveraglng time lor carcinogens (yr) 70 t Exposure duration (yr) 30 25 1 ATn Averaging lime for non,carcinogens Iyr) 30 6 16 25 1 A Contaminated soil area (cm^2) 1,2£+07 I,OE+06 BW Body Weight (kg) 70 15 35 70 W Length of affected soil parallel to wind Icm) 4,0£+03 1.0E+03 ED Exposure Duration (yr) 30 6 16 25 1 Wgw Lenqth of affected soil parallel to groundwater (cr 4,0£+03 EF Exposure Frequency Idays/yr) 350 250 180 Uair Aml)ient air velocily in mixing zone (cm/s) 2,3E+02 EFDerm Exposure Frequency for dermal exposure 350 250 dell a Air mixing zone height (cm) 2,OE+02 IRgw Ingestion Rate of Water (Iiday) 2 1 Lss Definition of surficial soils (cm) 1.0E+02 IRs Ingestion Rate of Soil (mg/day) 100 200 50 100 Pe Pallieulate areal emission rate (g/em^2Is) 2.2E'10 IRadj Adjusted soil ing, rate Img'yr/kg'd) 1.1 E+02 94E+Ol IrIfl,in Inhalation rate indoor (m^3/dayj 15 20 Grou~dwat~r [)~fll1itil)l1 (U-"i!~) -- ---~ .- - - -- \la!u~.__ Ina olJI Inhalation rale outdoor (n¡l\3/df'JY) 20 20 10 { Ollü.gw Grcllmdwaler mixing zone depth (em) 2,OE+02 SA SkIn surface area (dermal) (cm^¿) 5.8E+03 2,OE+03 5,8E+03 58E+03 I GrolHldwater infiltration rate (cm/yr) 3.0E+01 SAadj Adjusted dermal area (em^2'yr/kg) 2,lE+03 1.7E+03 Ugw Groundwater Darcy velocity (cm/yr) ~ M Soil 10 Skin adherence faclor 1 Ugw,lr Groundwaler Transport velocity (cm/yr) 3,8E+03 AAFs Age adjustment on soil ingestion FÄLSE FALSE Ks Saturated Hydraulic Conductivity(cm/s) 1,2E,02 AAFd Age adjustment on skin surface area FALSE FALSE grad Groundwater Gradient (em/em) 4.0E,03 tox Use EPA tax data for air (or PEL based) FALSE Sw Wid:h of groundwater source zone (em) 4,OE+03 gwMCL? Use MCL as exposure limít in groundwater? TRUE Sd Depth of groundwater source zone (em) 3,OE+02 BC Bioclegradation Capacity (mglL) BIG? Is Bloattenuation Considered TRUE phi,eff Effective Porosity in Waler-Bearing Unit 3,8E'01 toc.sat Fraction organic carbon in water-bearing unit 1,OE,03 Matrix of Exposed Persons to Residential Commercial/Industrial Complete Exposure Pathways " Chronic Constrctn Soil Definition (Units) Value Groundwater Pathways: he Capillary zone Ihickness (cm) 5,OE+00 GW,i Groundwater Ingestion TRUE FALSE hv Vadose zone thickness (em) ~ GW,v Volatilization 10 Ouldoor Air FALSE FALSE rho Soil density (g/cm^3) 1.7 GW,b Vapor Intrusion to Buildings FALSE FALSE foc Fraction of organic carbon in vadose zone 0,01 Soil Pathways phi Soil porosity in vadose zone 0,38 S.v Volatiles from Subsurface Soils FALSE TRUE Lgw Depth to groundwater (em) ~ SS,v Volatiles and Particulate Inhalation FALSE FALSE FALSE Ls Depth to top of affected soil (em) ~ SS,d Direct Ingestion and Dermal Contact FALSE FALSE FALSE Lsubs Thickness of affected subsurface soils (em) ~ S,I Leaching to Groundwater from all Soils TRUE FALSE pH Soil/groundwater pH 6,5 S,b Intrusion to Buildings' Subsurface Soils FALSE FALSE caoillarv vadose foundation phi,w Vofumetric water content 0,342 0.12 0,12 phi,a Volumetric air conlent 0,038 0,26 0,26 Building Definition (Units) Residential Commercial Lb Building volume/area ratio (cm) 2,OE+02 3,OE+02 Matrix of Receptor Distance Residential CommerciaUlndustrial ER Building air exchange rate (s^,1 ) 1.4E-04 2.3E'04 and Location on, or oll,site Distance On-Site Distance On,Site Lcrk Foundation crack thickness (em) 1,5E+01 eta Foundation crack fraction 0,01 GW Groundwater receptor (em) 4,6E+04 FALSE 4.6E+04 FALSE S Inhalation receptor (em) 6,1 E+03 FALSE TRUE Dispersive Transport Matrix of Parameters Definition (Units) Residential Commercial Target Risks Individual Cumulative Groundwater ax Longitudinal dispersion coefficient (em) 4,6E+03 TRab Target Risk (class A&B carcinogens) 1,OE,06 ay Transverse dispersion coefficient (em) 1.5E+03 TRc Targel Risk (class C carcinogens) 1.0E,05 az Vertical dispersion coefficient (em) 2,3E+02 THQ Target Hazard Quotient l,OE+OO Vapor Opt Calculation Option (1,2, or 3) 2 dcy Transverse dispersion coefficient (cm) Tier RBCA Tier 2 dcz Vertical dispersion coefficienl (em) © Groundwater Services, Inc, (GSI), 1995. All Rights Reserved, · Input Screen 7 REPRESENTATIVE COC CONCENTRATIONS IN SOURCE MEDIA (Complete the following table) enzene Ethylbenzene Toluene Xylene (mixed isomers) Representative COC Concentration in Groundwater in Surface Soil in Subsurface Soil value (mg/L) note value (mg/kg) note value (mg/kg) note 3.3 +0 1 .1 E+O 5.2E+0 4.3E+0 CONSTITUENT UCL UCL UCL Site Name: City of Bakersfield Site Location: Bakersfield Muni. Airport Completed By: Tim Reed Date Completed: 11/10/1997 © Groundwater Services, Inc. (GSI), 1995, All Rights Reserved. . , , ,,' ~ ' ". RP.CA §'T~ A§S.t:§§M~NT'i . CONSTITUENT HALF-LIFE VALUES (Complete the following table) CONSTITUENT Half-Life of Constituent (day) 720 228 28 360 Benzene Ethylbenzene Toluene Xylene (mixed isomers) Site Name: City of Bakersfield Site Location: Bakersfield Muni. Airport Completed By: Tim Reed Date Completed: 11/10/1997 © Groundwater Services, Inc. (GSI), 1995. All Rights Reserved. . . Input Screen 9.4 enzene Ethylbenzene Toluene Xylene (mixed isomers) GROUNDWATER DAF VALUES (Enter OAF values in the grey area of the following table) Dilution Attenuation Factor (OAF) in Groundwater Residential Comm./lnd. Receptor Receptor 5.4 +2 1.0 +0 2.7E+4 1.0E+O 4.2E+ 12 1.0E+O 1.9E+4 1.0E+O CONSTITUENT Site Name: City of Bakersfield Site Location: Bakersfield Muni. Airport Completed By: Tim Reed Date Completed: 11/10/1997 © Groundwater Services, Inc. (GSI), 1995. All Rights Reserved. . . . 'f t ,j if 'II¡ ~'((' or"~. >t-, : R~~A §ITIJ; A&§IE§§MI;N~'" ~ 't· - . ] EXPOSURE LIMITS IN GROUNDWATER AND AIR CONSTITUENT enzene Ethylbenzene Toluene Xylene (mixed isomers) Site Name: City of Bakersfield Site Location: Bakersfield Muni. Airport Exposure Limits Applied to Receptors Groundwater Air (Comm. only) (MCL) (mg/L) (PEUTL V) (mg/m^3) 5.0 -3 3.2 +0 7.0E-1 4.3E+2 1.0E+0 1.5E+2 1.0E+ 1 4.3E+2 Completed By: Tim Reed Date Completed: 11/10/1997 © Groundwater Services, Inc. (GSI), 1995. All Rights Reserved. . - . . R~CA CHEfJlIC~t- P.t\TAß,AS~ , Physical Property Data Vapor CAS NumbE!r Constituent Diffusion log (Koc) or Pressure Molecular Coefficients log(Kd) Henry's Law Constant (@ 20 - 25 C) Solubility Weight in air in water (@ 20 - 25 C) (@ 20 - 25 C) (mm Hg) (@ 20 - 25 C) (g/mole) (cm2ls) (cm2ls) (1/kg) (atm-m3) (unitless) Pure (mg/l) Pure acid base type MW ref Dair rei Dwat rei Koc ref mol re Component ref Component ref pKa pKb ref Refere!nce Number Reference R EPA Region III Risk Based Concentration Table, EPA Region 3, March 7,1995. S USEPA, Test Methods for Evaluating Solid Waste, SW-846, Third Edition, OSWER, November 1986, H Howard, Handbook of Environmental Degradation Rates, Lewis Publishers, Chelsea, MI, 1989 A Emergency Standard Guide for Risk-Based Corrective Action Applied at Petroleum Release Sites, ASTM, ES 38-94. 3 Based on Kow from (2) and DiToro, D. M., 1985:"A Particle Interaction Model of Reversible Organic Chemical Sorption", Chemosphere, 14(10), 1505-1538. 10g(Koc) = 0,00028 + 0.983 10g(Kow) 4 USEPA, 1989: Hazardous Waste Treatment, Storage, and Disposal Facilities (TSDF) - USEPA, OAQPS, Air Emission Models, (EPA-450/3-87-026). 5 Verschueren, Karel, 1983: Handbook of Environmental data on organic Chemicals, Second Ed" (Van nostrand Reinhold Company Inc., New York), ISBN: 0-442-28802-6. 6 Calculated diffusivity using the method of Fuller, Schettler, and Giddings from (9). 7 Calculated diffusivity using the method of Hayduk and Laudie and the reference from (9). 8 Calculated using Kenaga ang Goring Kow/solubility regression equation reference (9) and Kow data from (2), 10g(S, mg/I) = -0.922 log(Kow) + 4,184 9 Handbook of Chemical Property Estimation Methods, 1982, W.J. Lyman, (McGraw-Hili, New York), ISBN -0-07-039175-0, 10 Calculated from (Pv/Patm)/(solubility/mol wt), 11 Back calculated from solubility, Note (8) and (3). 12 Aldrich Chemical Catalog, 1991. 13 Calculated using Modified Watson Correlation from (9) and normal boiling point. 14 USEPA, 1979: Water Related Environmental Fate of 129 Priority Pollutants, VoJ.1, USEPA, OWQPS,(EPA-4404-79-029a), 15 The Agrochemicals Handbook, (The Royal Society of Chemistry, The University, Nottingham, England), ISBN 0-85186-406-6. 16 Vapor pressure specified at elevated temperature, adjustments to 25C using methods presented by (9). 17 Wauchope, R. 0" T. M, Butler, A. G. Hornsby, P. W, M. Augustijn-Beckers, and J.P. Burt, 1992: "The SCS/ARS/CES Pesticide Properties Database for Environmental Decision Making", Reviews of Environmental Contamination and Toxicology, vol 123, 1-155. 18 Farm Chemicals Handbook 91, C. Sine, ed" (Meister Publishing Company, Willoughby, Ohio). 19 Structure and Nomenclature Search System, (Version 7.00/7.03) December, 1992. 20 From Syracuse Research Corporation Calculated Value from pcchem-pcgems, 1988, ref no, 255435 in Enírofate database, Accession no. 105543. 23 NIOSH, 1990: Pocket Guide to Chemical Hazards, (U, S, Dept. of Health & Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health), 24 Buchter, B. et aI., 1989: Correlation of Greundlich Kd and N retention Parameters with Soils and Elements, Soil Science, 148, 370-379. 25 USEPA, 1993: Air/Superfund National Technical Guidance Study series: Estimation of Air Impacts for Thermal Desorption Units Used at Superfund Sites, US Environmental Protection Agency, Office of Air Quality Planning and Standards, EPA-451/R-93-005, NTIS Accession No. PB93-215630, April 1993. 27 Based on salt solubilities in Table 3-120, R, H. Perry and D. W, Green, " Perry's Chemical Engineering Handbook" Sixth Edition, (McGraw-Hili, New York), ~I . . ABC.«\ ~HFM!ÇAI- QATA~ASt: ' Vapor CAS Number Constituent 1973 28 Based on salt solubilities in Table of Physical Constants for Inorganic Compounds, Weast, R. C., CRC Handbook of Chemistry and Physics, 67th edition, (CRC Press, Inc., Boca Raton), 1987. 29 Montgomery and Welkom, "Groundwater Chemicals Desk Reference", Lewis Publishers, Chelsea, MI, 1990, Molecular Weight (g/mole) MW ref Diffusion Coefficients in air in water (cm2/s) (cm2ls) Dair reI Dwat reI log (Koc) or log(Kd) (@ 20 - 25 C) (I/kg) Koc Henry's Law Constant (@ 20-25C) (atm-m3) (unitless) mol re' Pressure (@ 20 - 25 C) (mm Hg) Pure Component ref Solubility (@ 20 - 25 C) (mg/I) Pure acid Component ref pKa base pKb ref type ref