CORRECTIVE ACTION COMPLETION REPORT ... - City of Park Ridge

R E P O R TCORRECTIVE ACTION COMPLETIONREPORTSHELL OIL PRODUCTS USSHELL SERVICE STATION # 137156900 W. TALCOTT ROADPARK RIDGE, ILLINOISLUST INCIDENT NO. 20051292Property ofShell Oil Products USPrepared forEquilon Enterprises, LLC. dbaShell Oil Products US603 Diehl Road, Suite 103Naperville, IL 60563January 2009100 South Wacker DriveSuite 500Chicago, Illinois 60606(312) 939-1000

Corrective Action Completion Report IEMA No. 20051292Shell Service Station # 137156900 W. Talcott Road, Park Ridge, IllinoisTABLE OF CONTENTSCORRECTIVE ACTION COMPLETION REPORTA. Site Identification…………………………………………….……………………1B. Site Information…………………………………………………………………...1C. Remedial (Corrective) Action……………………………………………………..2D. Signatures………………………………………………………………………...19FIGURES:FIGURE 1:FIGURE 2:FIGURE 3:FIGURE 4:FIGURE 5:FIGURE 6:FIGURE 7:FIGURE 8:SITE LOCATION MAPLAND USE MAPBASE MAP WITH UTILITIESGROUNDWATER EQUIPOTENTIAL AND CONCENTRATION MAPSOIL ANALYTICAL RESULTS MAPAREAS SUBJECT TO INSTITUTIONAL CONTROLMODELED PLUME: MIGRATION TO GROUNDWATER PATHWAYMODELED PLUME: GROUNDWATER INGESTION PATHWAYTABLE:TABLE 1:TABLE 2:GROUNDWATER ELEVATIONS AND ANALYTICAL RESULTSSOIL ANALYTICAL RESULTSAPPENDICES:APPENDIX A: IEPA LETTER DATED DECEMBER 13, 2006APPENDIX B: SOIL BORING LOGS/MONITORING WELL CONSTRUCTIONDIAGRAMSAPPENDIX C: ZIRON MONITORING WELL REPORTSAPPENDIX D: LABORATORY REPORTSAPPENDIX E: ZIRON STANDARD OPERATING PROCEDURESAPPENDIX F: VILLAGE OF PARK RIDGE LIMITED GROUNDWATERORDINANCE (PROPOSED)APPENDIX G: IDOT HIGHWAY AUTHORITY AGREEMENT (PROPOSED)APPENDIX H: PROPERTY OWNER SUMMARY FORMAPPENDIX I: TACO CALCULATIONS

The Agency is authorized to require this information under Section 4 and Title XVI of the Environmental Protection Act (415 ILCS 5/4, 5/57 - 57.17). Failure to disclose this information may result in acivil penalty of not to exceed $50,000.00 for the violation and an additional civil penalty of not to exceed $10,000.00 for each day during which the violation continues (415 ILCS 5/42). Any person whoknowingly makes a false material statement or representation in any label, manifest, record, report, permit, or license, or other document filed, maintained or used for the purpose of compliance with TitleXVI commits a Class 4 felony. Any second or subsequent offense after conviction hereunder is a Class 3 felony (415 ILCS 5/57.17). This form has been approved by the Forms Management Center.A. Site IdentificationIllinois Environmental Protection AgencyLeaking Underground Storage Tank ProgramCorrective Action Completion ReportIEMA Incident # (6-digit) : 20051292 IEPA LPC# (10-digit) : 0312460015Site Name: Shell Service Station # 137156Site Address (Not a P.O. Box) : 900 Talcott RoadCity: Park Ridge County: Cook Zip Code: 60068B. Site Information1. Has a High Priority Corrective Action Planbeen approved? Yes NoDate of approval letter: 12/13/20062. This completion report is being submitted pursuant to:a. 35 Ill. Adm. Code 731.166b. 35 Ill. Adm. Code 732.300(b)c. 35 Ill. Adm. Code 732.404d. 35 Ill. Adm. Code 734.3453. Method of remediation chosen:a. SoilThe method of remediation proposed to address the extent of soil impact remainingat the site is Exposure Pathway Exclusion (Pathway Elimination) based on residentialland use and pursuant to the Tiered Approach to Corrective Action Objectives(TACO) presented in 35 Illinois Administrative Code (IAC) Section 742.b. GroundwaterThe method of remediation selected to address the groundwater impact remaining atthe site is Pathway Elimination pursuant to the TACO presented in 35 IAC Section742.4. Quantity of contaminated media remediated/recovered:a. Soil 0 yds3b. Groundwater 0 galsc. Free Product Free product was not encountered at the site. 0 gals

Corrective Action Completion Report IEMA No. 20051292Shell Service Station # 137156900 W. Talcott Road, Park Ridge, IllinoisC. Remedial (Corrective) Action1. An executive summary that identifies the overall objectives of the corrective actionand the technical approach utilized to meet those objectives. The summary shallcontain the following information:Site Description:a. A brief description of the site, including but not limited to a description ofthe release, the applicable indicator contaminants, the contaminated media,and the extents of soil and groundwater contamination that exceeded themost stringent Tier 1 remediation objectives;The Shell Service Station (site) is located in the in the southeast quarter of the northwestquarter of Section 35, Township 41 North, Range 12 East, of the United States GeologicalSurvey (USGS) 7.5-Minute Series Park Ridge, Illinois Quadrangle. The site is located withina mixed area of commercial and residential properties. The site, located at the northwestcorner of the intersection between Cumberland Avenue and Talcott Road, is bordered to thenorth and west by residential properties. The site is bordered to the east by CumberlandAvenue with commercial properties beyond. Talcott Road borders the south propertyboundary with residential properties located beyond. Figure 1 presents a site location map.Figure 2 presents the surrounding land use.Current site features include three 10,000-gallon gasoline underground storage tanks (USTs),one 1,000-gallon used oil UST, three fuel dispenser islands, and a one-story auto servicebuilding that houses a convenience store. Former site features include one 1,000-gallon usedoil UST (location of the existing used oil UST), which was removed in 1998. Figure 3presents the current and former site features and location of utilities at the site.Description of the Release:On August 12, 2005, Remediation Unlimited, Inc. (RUI), with NESA & Associates, Inc.(NESA) oversight, advanced six soil borings (SB-1 through SB-6) using vacuum excavationand hand auger methods to advance the first five feet below ground level (bgl) of each soilboring to clear possible utilities. The soil borings were then completed to a maximum depthof 16 feet bgl using driven push methods. Soil samples collected during the assessmentactivities were submitted to an Illinois-accredited stationary laboratory for the analysis of thegasoline indicator contaminants consisting of: benzene, toluene, ethylbenzene, total xylenes(BTEX) and methyl tertiary butyl ether (MTBE) using United States EnvironmentalProtection Agency (USEPA) Method SW846-8260B. A soil sample collected from soilboring SB-6, installed in the vicinity of the used oil UST, was submitted to an Illinoisaccreditedstationary laboratory for the analysis of the following used oil indicatorparameters (LUST Priority Pollutants) by using the respective USEPA Methods SW846:volatiles 8260, polynuclear aromatic (PNA) hydrocarbons 8270, base/neutrals 8270, metals3050B and 7471A. Soil sample SB-2 (2) was analyzed for pH using USEPA MethodSW846 9045.Soil borings SB-1 through SB-5 were completed as monitoring wells MW-1 through MW-5using hollow-stem auger methods. The wells were constructed of 2-inch inside diameter (ID)2

Corrective Action Completion Report IEMA No. 20051292Shell Service Station # 137156900 W. Talcott Road, Park Ridge, IllinoisSchedule 40 polyvinyl chloride (PVC) riser and 0.010 slot PVC well screen. A coarse sandfilter pack was placed around the well screen.On August 19, 2005, Ziron Environmental Services, Inc. (Ziron) performed groundwatermonitoring and sampling on monitoring wells MW-1 through MW-5. The depth-to-water ineach monitoring well was measured using an audible electronic interface probe. Monitoringwells MW-2, MW-3, and MW-4 were dry and therefore not sampled. Monitoring wellsMW-1 and MW-5 were then developed by pumping and surging to remove fines that mayhave settled in the well. After a brief stabilization period, approximately three well volumeswere purged from each well using an evacuation pump attached to dedicated tubing.Dedicated disposable polyethylene sampling bailers were then used to collect representativegroundwater samples and to minimize the risk of cross-contamination between wells.Samples were immediately transferred to laboratory-supplied, hydrochloric acid-preserved,40-milliliter vials, packed on ice, and shipped via overnight delivery service, under chain-ofcustodydocumentation, to an Illinois-accredited stationary laboratory for the laboratoryanalysis of BTEX and MTBE using USEPA Method SW846-8260B. Additionally, Zironsurveyed the top of casing elevation of monitoring wells MW-1 through MW-5 relative to anestablished site-specific benchmark.Based on the results of the site investigation activities, compounds of concern (COCs) weredetected in soil and groundwater samples above Illinois Environmental Protection Agency(IEPA) Tier 1 Soil and Groundwater Remediation Objectives (SROs and GROs); therefore, arelease of gasoline was reported to the Illinois Emergency Management Agency (IEMA) onSeptember 13, 2005, and Leaking Underground Storage Tank (LUST) incident number20051292 was assigned.Contaminated Media:1. Soil:Plate 1 of the Illinois State Geological Survey (ISGS), Circular 532 (Berg Circular), wasreferenced to determine the prevalent geology within the area of the site. Circular 532classifies the area with an “E” rating. The description given for an “E” rating depicts the areageology as consisting of uniform, relatively impermeable silty or clayey till or other finegrained material more than 50 feet thick. The fine grained till generally has moderate to highattenuation capacities and low hydraulic conductivities.A soil investigation was conducted at the site in August 2005, May 2006, and May 2008.Based on the geology encountered during the site investigation activities, the geologybeneath the site is generally consistent with the Berg Circular and comprised of thefollowing: fill material containing gravel from below the surface cover to an average depth of1.5 feet below ground level (bgl) across the site. Underlying the fill, a clay formationcontaining minor amounts of silt and gravel to the maximum depth explored of 16 feet bgl wasencountered. Detailed soil boring and monitoring well construction logs are provided inAppendix B.2. Groundwater:On November 24, 2007, February 16, June 16, and October 24, 2008, Ziron performedgauging and sampling activities on the site’s monitoring wells. Depth-to-water3

Corrective Action Completion Report IEMA No. 20051292Shell Service Station # 137156900 W. Talcott Road, Park Ridge, Illinoismeasurements were recorded by a Ziron technician using a standard measuring tape equippedwith an electronic sensor. The depth-to-water measurements on October 24, 2008, rangedfrom 1.38 feet below top of casing (btoc) in monitoring wells MW-1 to 10.44 feet btoc inmonitoring well MW-7. The average depth-to-water measured at the site is 5.08 feet btoc.Based on the groundwater elevation measurements collected at the site on October 24, 2008the generalized direction of groundwater flow across the site is towards the west, under ahydraulic gradient of 0.028 ft/ft. The depth-to-water measurements are tabulated in Table 1,and the groundwater equipotential lines and flow direction (for the most recent event onOctober 24, 2008) are shown on Figure 4. The Ziron monitoring well reports are presentedin Appendix C.An in-situ (bail-down) test was performed by Ziron on November 30, 2005, on monitoringwells MW-1 and MW-5 to measure the hydraulic conductivity of the water-bearingformation beneath the site. The bail-down test data collected in the field from monitoringwells MW-1 and MW-5 was analyzed using the Bouwer-Rice Method for analyzing aquiferparameters, and the resulting hydraulic conductivity measurements from monitoring wellMW-1 and MW-5 are 2.53 x 10 -6 and 1.77 x 10 -6 centimeters per second (cm/s), respectively.The most conservative hydraulic conductivity measurement (MW-1: 2.53 x 10 -6 cm/s) wasthen used to calculate an estimated groundwater yield of 2.53 gallons per day for the site.The bail-down test analysis data and the groundwater yield calculation and parameter valueswere provided to the IEPA in the Site Investigation Completion Report (SICR) dated July 7,2006. A Class II groundwater demonstration was provided in the SICR dated July 7, 2006,and approved by the IEPA in the technical review letter dated July 19, 2006.Extent of Contamination Above Tier 1 Remediation Objectives:Soil Analytical Results (Tier 1 Evaluation):Soil BTEX and MTBE concentrations were compared with the following IEPA Tier I SROsfor Residential Properties:Soil Component of the Groundwater Ingestion Exposure PathwaySoil Inhalation Exposure PathwaySoil Ingestion Exposure PathwaySite investigation results indicate that the extent of soil BTEX and MTBE impact above theTier 1 Migration to Class II Groundwater SROs has been defined by the following soilborings:SB-12, SB-6, and SB-13 on-site to the north;SB-8 and SB-9 off-site to the south;SB-16 and SB-7 off-site to the east; andSB-10, SB-11, and SB-12 on-site to the west.The soil samples collected from soil borings GP-1 (3-4), GP-2 (4-5), GP-3 (4-5), SB-3(4), and SB-4 (5) were collected at or below the static water table as shown by the depth towater measurements collected from monitoring wells MW-3, MW-4, and MW-5. Soil boringGP-1 is located next to MW-5 which had a depth to water measurement of 3.71 feet BTOCnear the time the soil sample from GP-1 was collected from the 3-4 (bgl) foot interval. Soilboring GP-2 is located next to MW-4 which had a depth to water measurement of 4.05 feet4

Corrective Action Completion Report IEMA No. 20051292Shell Service Station # 137156900 W. Talcott Road, Park Ridge, IllinoisBTOC near the time the soil sample from GP-2 was collected from the 4-5 foot (bgl) interval.Soil boring GP-3 is located next to MW-3 which had a depth to water measurement of 3.45feet BTOC near the time the soil sample from GP-3 was collected from the 4-5 foot (bgl)interval. Soil samples SB-3 (4) and SB-4 (5) were collected during the installation ofmonitoring wells MW-3 and MW-4, respectively. The average depth to water measurementsfrom MW-3 (3.8 feet BTOC) and MW-4 (4.8 feet BTOC) demonstrate that the soil samplescollected from SB-3 (4) and SB-4 (5) were collected from below the static water table.Based on the information presented above, the BTEX and MTBE concentrations in soilsamples GP-1, GP-2, GP-3, SB-3, and SB-4 are not representative of the BTEX and MTBEconcentrations within the unsaturated zone. Risk Based Corrective Action (RBCA) will beutilized to determine the furthest extent of potential groundwater impact. The soil analyticalresults for BTEX and MTBE are summarized in Table 2. Soil sampling locations andcorresponding BTEX and MTBE concentrations are presented on Figure 5. Laboratoryreports from the recent site assessment activities are provided in Appendix D.Groundwater Analytical Results (Tier 1 Evaluation):The chemical analytical data for the groundwater samples were compared with the IEPA Tier1 GROs for Class II groundwater. These cleanup objectives are provided in 35 IAC Section742. Appendix B, Table E. The results of the site investigation activities indicate that theextent of groundwater BTEX and MTBE impact above Tier 1 GROs for Class II groundwaterhas been defined by the following monitoring wells:MW-1 and MW-11 to the north;MW-7 and MW-8 to the south;MW-1, MW-2 and MW-3 to the east; andMW-9, MW-10 and MW-11 to the west.Concentrations of BTEX and MTBE in groundwater are summarized in Table 1. Monitoringwell locations and the corresponding BTEX and MTBE concentrations are presented onFigure 4. Laboratory reports for the recent groundwater sampling events are provided inAppendix D.b. The major components (e.g., treatment, containment, removal) of thecorrective action;The major component of the corrective action is Pathway Elimination pursuant to the TACOpresented in 35 IAC Section 742.c. The scope of the problems corrected or mitigated by the corrective action;andSoil and groundwater impact above Tier I SROs remaining at the site are addressed in thecorrective action.d. The anticipated post-corrective action uses of the site and areas immediatelyadjacent to the site;The anticipated post-corrective action use of the site will be to remain as a retail gasolinestation. There are no anticipated changes in the current uses of the areas adjacent to the siteupon the completion of corrective action.5

Corrective Action Completion Report IEMA No. 20051292Shell Service Station # 137156900 W. Talcott Road, Park Ridge, Illinois2. A description of the corrective action activities conducted including:Soil Investigation:a. A narrative description of the field activities conducted as part of correctiveactionOn May 12, 2008, CS Drilling with URS Corporation (URS) oversight, advancedfive soil borings (GP-1 through GP-5) on site as part of a Phase II EnvironmentalSite Assessment (ESA) in preparation for the sale of the property. The soilborings were advanced to a maximum depth of 10 feet bgl using vacuumexcavator, hand auger, and driven push methods. Soil samples collected duringthe assessment activities were submitted to an Illinois-accredited stationarylaboratory (SPL: Houston, TX) for the analysis of BTEX and MTBE usingUSEPA Method SW846-8260B. The analytical laboratory reports are provided inAppendix D.Soil sampling performed by URS was conducted following standard industrypractice and the sampling procedures established in ASTM Method E 1903-97.An air-knife was utilized to advance the first 5 feet of each soil boring to reducethe risk of damaging subsurface utilities that may be present. During the airknifingactivities only, a soil sample was collected at one-foot intervals, utilizing adecontaminated steel hand auger. After reaching a depth of 5 feet, a direct-pushdrilling unit was utilized to collect soil samples. A portion of each soil samplewas placed into a re-sealable plastic bag and allowed to volatilize to screen for thepresence of VOCs utilizing a 10.6 eV photo-ionization detector (PID). The soilsample was logged by a field geologist and recorded on a field boring log alongwith the PID readings and any visual indications of product saturation and/orstaining. At each sampling interval above the water table, a soil sample wascollected in a glass jar and placed into a cooler with ice. The soil intervalexhibiting the highest PID reading and/or visual/olfactory signs of impact wasthen preserved in the field using USEPA Method SW846-5035. Soil sampleswere collected and preserved based on these field observations as well asprofessional knowledge of contaminant migration through soils.Groundwater Investigation:On November 24, 2007, February 16, June 16, and October 24, 2008, Zironperformed gauging and sampling activities on the sites monitoring wells. Zironpersonnel performed groundwater sampling of the sites monitoring wells asreported by the Ziron standard operating procedures provided in Appendix E.The samples collected by Ziron personnel were submitted to an Illinois-accreditedstationary laboratory (Test America: Nashville, TN for samples collected onNovember 24, 2007 and Xenco Laboratories: Houston, TX for samples collectedon February 16, June 16, and October 24, 2008) for the laboratory analysis ofBTEX and MTBE using USEPA Method SW846-8260B. Groundwater analyticalresults are summarized in Table 1 and shown on Figure 4. The laboratorychemical analytical reports for groundwater samples are presented in AppendixD.6

Corrective Action Completion Report IEMA No. 20051292Shell Service Station # 137156900 W. Talcott Road, Park Ridge, IllinoisNot Applicable.b. A narrative description of the remedial actions implemented at the site andthe performance of each remedial technology utilized;c. Documentation of sampling activities;The following list sources of documentation provided for sampling activities:i) Sample Collection Information;Sample collection information is provided in the previously submitted reports and in SectionC.2.a.ii)Sample Preservation and Shipment Information;Sample preservation and shipment information is provided in the previously submittedreports and in Section C.2.a.iii)Analytical Procedure Information;Analytical procedure information is provided in the previously submitted reports and inAppendix D.iv)Analytical Results, Chain of Custody, and Control, and LaboratoryCertification;Analytical results, chain of custody, and control, and laboratory certification are provided inthe previously submitted reports and in Appendix D.v) Field and Lab blanksLab blanks are provided in the previously submitted reports and in Appendix D.vi)Tables comparing analytical results to remediation objectives approvedfor the site;Groundwater and soil analytical results for BTEX/MTBE are summarized and compared tothe remediation objectives in Table 1 and Table 2, respectively.d. Soil boring logs and monitoring well construction diagrams.Soil boring and monitoring well construction diagrams are provided in Appendix B.3. A narrative description of any special conditions relied upon as part ofcorrective action including:a) Engineered barriers utilized;i) type of barrier; andAn asphalt or concrete engineered barrier of at least 3-inches in thickness will be maintainedon site to eliminate the risks associated with soil impact exceeding the soil inhalationexposure route in accordance with 35 IAC Section 742.1100 and will be recorded to the deedof the property.ii)map showing location(s) and dimension(s) of barrier(s);The location and dimension of the engineered barrier is presented on Figure 6.7

Corrective Action Completion Report IEMA No. 20051292Shell Service Station # 137156900 W. Talcott Road, Park Ridge, Illinoisb) Institutional controls utilized:i) copy of fully executed institutional control(s); andThe following institutional controls will be utilized to exclude the Soil Inhalation, SoilComponent of the Groundwater Ingestion, and Groundwater Ingestion Pathways from furtherevaluation:On site:Village of Park Ridge Limited Groundwater Ordinance (proposed)On site: Engineered BarrierOff site: Village of Park Ridge Limited Groundwater Ordinance (proposed)Off site: Illinois Department of Transportation (IDOT) Highway AuthorityAgreement (HAA) (proposed)A copy of the Village of Park Ridge Limited Groundwater Ordinance (proposed) thatprohibits the installation and/or use of wells as a potable water source is provided inAppendix F. A copy of the HAA (proposed) between Shell and the IDOT is provided inAppendix G. The Owner/Operator Property Summary Form, which indicates the propertyowners approval of the institutional controls, is included as Appendix H.ii)map showing location(s) of controls;Figure 6 presents the area subject to the executed institutional controls.c) Other conditions, if any, necessary for protection of human health andsafety and the environment that are related to the issuance of a No FurtherRemediation Letter; andBased on the Tier 2 evaluation presented in Section C.9 and the executed institutionalcontrols, there are no other conditions necessary for the protection of human health andsafety.d) Any information required regarding off-site access;Not applicable.4. An analysis of the effectiveness of the corrective action that compares theconfirmation sampling results to the remediation objectives approved for the site;Concentrations of benzene in soil sample SB-15 are above the calculated Tier 2 SRO (5.98mg/kg) for the Soil Inhalation Exposure Pathway; therefore, an engineered barrier will beutilized to eliminate the Soil Inhalation Exposure Pathway. Concentrations of benzene in soilsamples SB-3, SB-5 and SB-15 are above the calculated Tier 2 SRO (benzene = 1.3 mg/kgfor Class II groundwater) for the Soil Component of the Groundwater Ingestion ExposurePathway. However, the Village of Park Ridge has a limited groundwater ordinance(proposed) which prohibits the use and/or installation of potable water supply wells. TheVillage of Park Ridge limited groundwater ordinance (proposed) will be utilized to eliminatethe Soil Component of the Groundwater Ingestion Exposure Pathway. The RBCA R26equation will be used to determine the extent that potential groundwater impact, fromcontaminated soil leaching to groundwater, may migrate. The TACO Tier 2 evaluation ispresented in Section C.9.8

Corrective Action Completion Report IEMA No. 20051292Shell Service Station # 137156900 W. Talcott Road, Park Ridge, Illinois5. A conclusion that identifies the success in meeting the remediation objectivesapproved for the site;Based on the results of the Tier 2 evaluation and the executed institutional controls, the SoilInhalation, Soil Ingestion, Soil Component of the Groundwater Ingestion, and GroundwaterIngestion Exposure Pathways have been effectively eliminated. The TACO Tier 2 evaluationis presented in section C.9.6. Appendices containing references and data sources;The appendices containing references and data sources are listed in the Table of Contents.7. The water supply well survey:a. Map(s) showing locations of community water supply wells and otherpotable wells and the setback zone for each well;The well search results found that there are no public, private and/or commercial watersupply wells within 2,500 feet of the site. The well search records were provided in theSICR dated July 7, 2006.b. Map(s) showing regulated recharge areas and wellhead protection areas;The IEPA Source Water Assessment Program (SWAP) database indicates that there are noregulated recharge areas within a one-mile radius of the site. The database indicates there areno wellhead protection areas within a one-mile radius of the site. The well search recordswere provided in the SICR dated July 7, 2006.c. Map(s) showing the current extent of groundwater contamination exceedingthe most stringent Tier 1 remediation objectives;Figure 4 shows the current extent of groundwater contamination above the Tier 1 GROs.d. Map(s) showing the modeled extent of groundwater contaminationexceeding the most stringent Tier 1 remediation objectives;Figure 7 and Figure 8 present the source dimensions used for Equation R26. Figure 7 andFigure 8 present the results of Equation R26 for migration to groundwater and groundwateringestion pathways, respectively.e. Table(s) listing the setback zones for each community water supply well andother potable water supply wells;Not applicable. The well search results found that there are no public, private and/orcommercial water supply wells within 2,500 feet of the site. The well search records wereprovided in the SICR dated July 7, 2006.f. A narrative identifying each entity contacted to identify potable water supplywells, the name and title of each person contacted, and any fieldobservations associated with any wells identified; andWell searches were conducted through the Illinois State Water Survey (ISWS), the ISGS, theIEPA Division of Public Water Supply, the DPWS SWAP, and Environmental DataResources, Inc. (EDR) to determine if there are any public, private and/or commercial wellslocated within 2,500 feet of the site. The well search results found that there are no public,9

Corrective Action Completion Report IEMA No. 20051292Shell Service Station # 137156900 W. Talcott Road, Park Ridge, Illinoisprivate and/or commercial water supply wells within 2,500 feet of the site. Based on theabove mentioned information the site is not located within the minimum set back zone of apotable water supply well, pursuant to 35 IAC Section 620.210. Results from the watersupply well search were provided in the SICR dated July 7, 2006.g. A certification from a Licensed Professional Engineer of LicensedProfessional Geologist that the survey was conducted in accordance withthe requirements and that the documentation submitted includes theinformation obtained as a result of the survey (Certification of this reportsatisfies this requirement).A certification from a Licensed Professional Engineer that the survey was conducted inaccordance with the requirements and that documentation submitted includes informationobtained as a result of the survey is provided in Section D.8. Site maps meeting the requirements of 35 Ill. Adm. Code 732.110(a) or 734.440.Figures 1 through Figure 8 meet the requirements of 35 IAC 734.440.9. Development of Tier 2 or 3 remediation objectives, if applicable:a. Equations used;In order to address the Tier 1 exceedances discussed in Section C.1a of this report, sitespecificremediation objectives were developed by using Tier 2 procedures provided inTACO, pursuant to 35 IAC Section 742.710 Appendix C, Table A. The following is asummary of equations used for the development of Tier 2 remediation objectives for the SoilInhalation, Soil Component of the Groundwater Ingestion (Soil Migration to Groundwater),and Groundwater Ingestion Pathways.PathwaySoil InhalationPathwaySoil Migration toGroundwaterPathwayGroundwaterIngestion PathwayScenarioResidentialResidentialClass IGroundwaterContaminantof ConcernBenzeneBenzene andEthylbenzeneBenzene andMTBEEquations UsedSSL Equations S6 andS26SSL Equations S18and S28RBCA Equations R12,R14, R20, R24, and R26RBCA Equation R26b. Discussion of how input variables were determined;The default input variables for the Soil Screening Level (SSL) equations are provided in 35IAC Section 742.710; Appendix C Table B. The default input variables for the RBCAequations are provided in 35 IAC Section 742.710; Appendix C Table D. Site specific inputvariables for the SSL and RBCA equations were collected from the site during the previoussite investigation activities and presented in the SICR dated July 7, 2006 and the CorrectiveAction Plan dated October 17, 2006.10

Corrective Action Completion Report IEMA No. 20051292Shell Service Station # 137156900 W. Talcott Road, Park Ridge, Illinoisc. Map(s) depicting distances used in equation; andThe distances used in the Tier 2 Groundwater Migration evaluation are shown on Figure 7and Figure 8.d. Calculations; andPrior to conducting an exposure pathway exclusion evaluation, the following site-specificphysical soil characteristics were assessed consistent with the requirements of 35 IAC Section742:1. Whether or not the concentration of any organic contaminantsexceeded the attenuation capacity of the soil.The soil samples with the highest sum of concentrations of BTEX in soil from above andbelow three (3) feet of ground surface were compared in the following table to site-specificnatural attenuation capacity values pursuant to 35 IAC Section 742.215.Sample IDSample Depth(in feet)Sum of BTEXConcentrations (mg/kg)Site-SpecificAttenuation Capacity(mg/kg)SB-15 2 149.6 99,900SB-3 4 56.23 33,500mg/kg = milligrams per kilogramSite-Specific attenuation capacities were calculated using foc values of 0.999 g/g (SB-12 at 2) and 0.0335 g/g(SB-12 at 4) and converting them into mg/kg.Based on these results, the site-specific soil attenuation capacity values have not beenexceeded at the site.2. Whether or not the organic contaminants exceeded the soilsaturation limit.The following table compares the default soil saturation limit (C sat ) presented in 35 IACSection 742, Appendix A, Table A, with the highest concentrations of BTEX detected in soilsamples collected at the site.Concentrations are listedin mg/kg.Benzene Toluene Ethylbenzene XylenesC sat * 870 650 400 320Highest IC Concentrationsfor soil samples collected 8.13 15 190 84.7above water table.* C sat values are from 35 IAC Section 742, Appendix A, Table A.These results demonstrate that the maximum concentration for benzene, toluene,ethylbenzene, and total xylenes detected in soil samples collected within the unsaturated zonedo not exceed the default C sat values.11

Corrective Action Completion Report IEMA No. 20051292Shell Service Station # 137156900 W. Talcott Road, Park Ridge, Illinois3. Whether or not the soils exhibited any characteristics of reactivity forhazardous waste.Subsurface soil at the site is impacted with residual amounts of unleaded gasoline; therefore,reactive hazardous waste would not be generated.4. The pH of the soil.Subsurface soil at the site is impacted with residual amounts of unleaded gasoline;therefore, no impact is likely to have occurred which exhibit corrosive or causticcharacteristics.TACO EXPOSURE PATHWAY EXCLUSION EVALUATION:Consistent with the procedures provided in 35 IAC Section 742, the following exposurepathways have been evaluated based on residential land use of the site:Soil Ingestion Exposure PathwaySoil Inhalation Exposure PathwaySoil Component of the Groundwater Ingestion Exposure PathwayGroundwater Ingestion Exposure PathwayTier 2 Soil Ingestion Exposure Pathway EvaluationBased on the Tier 1 evaluation, the concentrations of BTEX from soil samples collected atthe site were not detected above Tier 1 Residential Soil Ingestion Exposure Pathway SROs;therefore, the soil ingestion exposure pathway is excluded from further consideration as anenvironmental concern.Tier 2 Soil Residential Inhalation Exposure Pathway Evaluation (Benzene):Concentrations of benzene in soil samples SB-3, SB-5, and SB-15 are above the ResidentialSoil Inhalation Pathway SRO. Therefore, a site-specific benzene SRO was developed byusing the Tier 2 procedures provided in TACO, pursuant to 35 IAC Section 742.710;Appendix C, Table A. TACO provides the following Equation (S6) to develop site-specificSROs for the residential inhalation pathway:URFdTR ATc 365yrugmg EF ED 11,000VFThe following descriptions are given for each of the parameters in the equation above:VF = Mass Limit Volatilization Factor (m 3 /kg) (Equation S26)TR = Target Cancer Risk (default residential value) = 10 -6URF = Inhalation Unit Risk Factor (benzene: IRIS/HEAST) = 7.8x10 -6 (ug/m 3 ) -1ATc = Averaging Time for Carcinogens = 70 yrsEF = Exposure Frequency (default residential value) = 350 d/yrED = Exposure Duration for Inhalation of Carcinogens (default value) = 30 yrs12

Corrective Action Completion Report IEMA No. 20051292Shell Service Station # 137156900 W. Talcott Road, Park Ridge, IllinoisSSL Equation S26 (Section 742: Appendix C, Table A)VFMLQCTMLb7 s3.15 10yrcm 3d 106 sm 3The following descriptions are given for each of the parameters in the equation above:VF M-L = Mass Limit Volatilization Factor (m 3 /kg)T M-L = Exposure Interval for Mass-Limit Volatilization Factor = 30 yrQ/C = Inverse of the mean concentration at the center of a square sourceDefault value for ½ acre lot = 97.78 (g/m 2 -s)/(kg/m 3 )d S = Depth of Source (default) = 3.048 m (10)b = Dry Soil Bulk Density (Site Specific) = 1.58 g/cm 3Based on the above referenced parameter values and computations, the site-specific Tier 2Soil Residential Inhalation Pathway SRO value calculated for benzene is 5.98 mg/kg. TheTACO equation calculations are provided in Appendix I.The concentrations of benzene in soil sample location SB-15 is above the site-specific Tier 2SRO; therefore, an engineered barrier (i.e. asphalt/concrete cap) will be maintained as aninstitutional control, pursuant to 35 IAC Section 742.1105. A signed Owner/OperatorProperty Summary Form, indicating the property owners approval of the proposedinstitutional control, is provided in Appendix H. To address concentrations of benzene insoil sample SB-15 above the calculated Tier 2 SRO for the Soil Inhalation ExposurePathway, Shell will utilize a HAA with IDOT to eliminate the Soil Inhalation ExposurePathway as an environmental concern. The area covered under the proposed institutionalcontrols is presented on Figure 6.Tier 2 Soil Component of the Groundwater Ingestion Exposure Pathway Evaluation:Concentrations of benzene and ethylbenzene in soil exceed the Tier 1 Migration to Class IGroundwater SRO. To address the concentrations of benzene and ethylbenzene above theTier 1 SRO that will remain beneath the site, a Tier 2 evaluation was conducted to calculate asite-specific Tier 2 SROs for benzene and ethylbenzene using SSL Equation S28 provided in35 IAC Section 742.Appendix C, Table A.SSL Equation S28:C w I M LED M LbdsCw = Target Soil Leachate Concentration (mg/L) (Equation S18)I M-L = Infiltration Rate for Migration to Groundwater Mass-Limit = 0.18 m/yrED M-L = Exposure Duration for Migration to Groundwater Mass-Limit = 70 yrb = Dry Soil Bulk Density: site-specific: 1.58 g/cm 313

Corrective Action Completion Report IEMA No. 20051292Shell Service Station # 137156900 W. Talcott Road, Park Ridge, Illinoisd s= Depth of Source: default: 3.048 mSSL Equation S18 (Section 742: Appendix C, Table A)C wCwDF GWobj= Target Soil Leachate Concentration (Class II Groundwater)BenzeneTolueneEthylbenzeneXylenesMTBE= 0.5 mg/L= 50 mg/L= 20 mg/L= 200 mg/L= 1.4 mg/LDF = Dilution Factor (default) = 20GW obj = GRO (Chemical-Specific - Class II Groundwater)BenzeneTolueneEthylbenzeneXylenesMTBE= 0.025 mg/L= 2.5 mg/L= 1.0 mg/L= 10 mg/L= 0.07 mg/LBased on the SSL equation S28 demonstrations presented above, the site-specific Tier 2Migration to Class II Groundwater SROs are as follows:Benzene = 1.3 mg/kgToluene = 130.8 mg/kgEthylbenzene = 52.3 mg/kgXylenes = 523.3 mg/kgMTBE = 3.7 mg/kgThe SSL equation S28 parameter values and calculations are provided in Appendix I.Concentrations of benzene and ethylbenzene in soil exceed the site-specific Tier 2 SROs. Asa result, an additional Tier 2 evaluation was conducted to determine the potential forconcentrations of benzene and ethylbenzene in soil to leach to groundwater. The Tier 2evaluation was completed for each of the Tier 2 exceedances using the following RBCAequations and parameters.Equation R12 (Section 742: Appendix C, Table B):Equation R12 calculates a value for the maximum potential groundwater concentration as aresult of impacted soil leaching to groundwater (mg/L).GW source = Soil Concentration at the Source * LF swLF sw= Leaching Factor: (mg/L water )/(mg/kg soil ): Calculated value14

Corrective Action Completion Report IEMA No. 20051292Shell Service Station # 137156900 W. Talcott Road, Park Ridge, IllinoisEquation R14 (Section 742: Appendix C, Table B):LFswksHcm kgL gws s s as31UgwI Wgws = Soil bulk density: kg/L: Site Specific value: 1.58ws = Volumetric water content in vadose zone soils: cm 3 water/cm 3 soil: Default value: 0.3k s = Soil-Water Sorption Coefficient: cm 3 water/g soil : calculated value:Benzene = 1.97Ethylbenzene = 12.16H' = Henrys Law Constant: Default value: Benzene: 0.228 Ethylbenzene: 0.323as = Volumetric air content in vadose zone soils: cm 3 air/cm 3 soil: Default value: 0.13U gw = Groundwater Darcy Velocity: cm/yr: Site-specific: 2.23gw = Groundwater Mixing Zone Thickness: cm: Default Value: 200I = Infiltration rate: cm/yr: Default: 30W = Width of source area parallel to direction of groundwater movement: cm:= 3600 cm (measured from SB-1 to SB-10)Equation R20 (Section 742: Appendix C, Table B):K ock K fs oc oc= Organic Carbon Partition Coefficient: cm 3 /g or L/kg: Default valueBenzene = 58.9Ethylbenzene = 363f oc = Fraction of organic carbon: g/g: Site-Specific value: 0.0335Equation R24 (Section 742: Appendix C, Table B):U K igwK = Hydraulic Conductivity: cm/yr: Site-specific: 79.8i = Hydraulic Gradient: cm/cm: Site-specific: 0.028 (from October 2008 samplingevent)Equation R26 (Section 742: Appendix C, Table B):The TACO guidance document provides the following equation (R26) to predict the potentialfuture migration of potentially impacted groundwater as a result of soil concentrationsleaching to groundwater:C( x )C sourceexp2Xx1 14UxerfS werf4 y X 2S dzX15

Corrective Action Completion Report IEMA No. 20051292Shell Service Station # 137156900 W. Talcott Road, Park Ridge, IllinoisThe parameters in the equation presented above are described below.X = Distance from the planar source to the location of concern, along the centerline of theplume: cm:C source = The maximum potential concentration in groundwater that could occur at the sourceof the contamination as a result of soil leaching to groundwater was calculated using theTACO Equation R12. Based on the results of the R12 calculations, the maximum potentialgroundwater concentrations as a result of soil leaching to groundwater equals:x = Longitudinal dispersivity (i.e., Equation R16) = X * 0.10y = Transverse dispersivity (i.e., Equation R17) = x /3z = Vertical dispersivity (i.e., Equation R18) = x /20U = specific discharge (i.e., Equation R19) = (K * I)/ TK = Hydraulic Conductivity = 0.219 cm/day (site-specific measurement)i = Hydraulic Gradient = 0.028 cm/cm (site specific measurement)T = Total Soil Porosity = 0.43 (Default value)= First order degradation constant: (Appendix C, Table E)Benzene = 0.0009Ethylbenzene = 0.003S w = Source width (horizontal) of planar source perpendicular to groundwater flow (cm):= 4572 cm (measured from SB-8 to SB-12)S d= Source width (vertical) depth of planar source in the z direction, perpendicular togroundwater flow = 200 cm (default value)Based on the maximum potential groundwater concentration as calculated using EquationR12, the following parameter values and the R26 calculations are provided:Sample IDPotentialBenzeneConcentration(ug/L)CxX(cm)X(feet)SB-3 (4) 886 4.99 125 4SB-5 (2) 1,041 4.99 130 4.3SB-15 (2) 3,711 4.99 174 6Sample IDPotentialEthylbenzeneConcentration(ug/L)CxX(cm)X(feet)GP-5 (2-3) 15,288 10.4 60 2The following institutional controls will be utilized to exclude the Soil Component of theGroundwater Ingestion Pathway from further evaluation:16

Corrective Action Completion Report IEMA No. 20051292Shell Service Station # 137156900 W. Talcott Road, Park Ridge, IllinoisOn Site: Village of Park Ridge Limited Groundwater Ordinance(proposed)Off Site: Village of Park Ridge Limited Groundwater Ordinance(proposed)The furthest modeled extent of potential groundwater impact from benzene is presented onFigure 7. Based on the R12 and R26 calculations, it is clear that there is no immediate orlong-term threat of benzene concentrations in groundwater migrating past the compliancepoints determined by the furthest extent of the institutional controls. The parameter valuesand results of the TACO analysis are provided in Appendix I. A copy of the Village of ParkRidge Limited Groundwater Ordinance (proposed) that prohibits the installation and/or useof wells as a potable water source is provided in Appendix F.Tier 2 Groundwater Ingestion Exposure Pathway Evaluation:To evaluate the potential future migration of impacted groundwater with benzene andMTBE, a Tier 2 evaluation was performed. The evaluation was conducted to determine thepotential impacts using the following equations in accordance with the TACO procedurespresented in 35 IAC Section 742.710 (d):Equation R26 (Section 742: Appendix C, Table B):The TACO guidance document provides the following equation (R26) to predict the potentialfuture migration of impacted groundwater:C( x )C sourceexp2Xx1 14UxerfS werf4 y X 2S dzXC source = GW source : The maximum concentration in groundwater that is detected at the sourceof the contamination as a result of the release. Based on the results of the R26 calculations,the groundwater concentration detected at the sites potential migration is:C source = Maximum concentrations of benzene and MTBE above Tier 1 GROs from thegroundwater sampling events conductedx = Longitudinal dispersivity (i.e., Equation R16) = X * 0.10y = Transverse dispersivity (i.e., Equation R17) = x /3z = Vertical dispersivity (i.e., Equation R18) = x /20U = specific discharge (i.e., Equation R19) = (K * I)/ TK = Hydraulic Conductivity = 0.219 cm/day (site-specific measurement)i = Hydraulic Gradient = 0.028 cm/cm (site specific measurement)T = Total Soil Porosity = 0.43 (Default value)= First order degradation constant for benzene = 0.0009MTBE = 0.0000S w = Source width (horizontal) of planar source perpendicular to groundwater flow:= 2,408.0 cm (measured from MW-3 to MW-10)17

Corrective Action Completion Report IEMA No. 20051292Shell Service Station # 137156900 W. Talcott Road, Park Ridge, IllinoisS d = Source width (vertical) depth of planar source in the z direction, perpendicularto groundwater flow = 200 cm (default value)Cx = Groundwater remedial objectiveX = Distance to complianceBased on the groundwater concentrations and the above referenced parameter values, theresults of the Equation R26 calculations indicate:Well IDBenzeneConcentration(ug/L)CxX(cm)X(feet)MW-4 2,790 4.99 164 5.4MW-5 1,300 4.99 137 4.5Well IDMTBEConcentration(ug/L)CxX(cm)X(feet)MW-4 760 70.00 7,753 254The following institutional controls will be utilized to exclude the Groundwater IngestionPathway from further evaluation:On Site: Village of Park Ridge Limited Groundwater Ordinance(proposed)Off Site: Village of Park Ridge Limited Groundwater Ordinance(proposed)The furthest modeled extent of groundwater impact from benzene and MTBE is presented inFigure 8. Based on the R26 calculations, it is clear that there is no immediate or long-termthreat of benzene and MTBE concentrations in groundwater migrating past the compliancepoints determined by the furthest extent of the institutional controls. The parameter valuesand results of the TACO analysis are provided in Appendix I. A copy of the Village of ParkRidge Limited Groundwater Ordinance (proposed) that prohibits the installation and/or useof wells as a potable water source is provided in Appendix F.10. Property Owner Summary form.The property owner summary form is provided in Appendix H.18

Corrective Action Completion Report IEMA No. 20051292Shell Service Station # 137156900 W. Talcott Road, Park Ridge, IllinoisD. SignaturesAll plans, budgets, and reports must be signed by the owner or operator and list the owner’sor operator’s full name, address, and telephone number.UST Owner or OperatorName: Shell Oil Products USContact: John R. RobbinsAddress: 603 Diehl Road, Suite 103City: NapervilleState: IllinoisZIP Code: 60540Phone: (630) 276 - 4206Signature:Date:ConsultantCompany: URS Corporation - ChicagoContact: Stephen W. Bates, M.S.Address: 100 South Wacker DriveCity: ChicagoState: IllinoisZIP Code: 60606Phone: (312) 939-1000Signature:Date:I certify under penalty of law that all activities that are the subject of this plan were conducted under mysupervision or were conducted under the supervision of another Licensed Professional Engineer andreviewed by me; that this plan and all attachments were prepared under my supervision; that, to the bestof my knowledge and belief, the work described in this plan has been completed in accordance with theEnvironmental Protection Act [415 ILCS 5], 35 Ill. Adm. Code 734, and generally accepted standardsand practices of my profession; and that the information presented is accurate and complete. I am awarethere are significant penalties for submitting false statements or representations to the Illinois EPA,including but not limited to fines, imprisonment, or both as provided in Sections 44 and 57.17 of theEnvironmental Protection Act [415 ILCS 5/44 and 57.17].Licensed Professional EngineerName:Robin Semer, P.E.Company: URS Corporation - ChicagoAddress:100 South Wacker DriveCity:ChicagoState:IllinoisZIP Code: 60606Phone: (312) 939-1000Ill. Registration No.:License Expiration Date:Signature:Date:L.P.E. Seal19

Corrective Action Completion Report IEMA No. 20051292Shell Service Station # 137156900 W. Talcott Road, Park Ridge, IllinoisFIGURES

Corrective Action Completion Report IEMA No. 20051292Shell Service Station # 137156900 W. Talcott Road, Park Ridge, IllinoisTABLES

Monitoring WellIdentificationDateTop of Well CasingElevation (TOC)(feet)Depth toGroundwater(TOC)(feet)Table 1GROUNDWATER ELEVATIONS AND ANALYTICAL RESULTSShell Service Station # 137156900 Talcott Road, Park Ridge, IllinoisGroundwaterElevation(feet)Benzene(ug/L)Toluene(ug/L)Ethylbenzene(ug/L)Xylenes(ug/L)MTBE(ug/L)Tier 1 GRO forClass I5 1,000 700 10,000 70GroundwaterTier 1 GRO forClass II25 2,500 1,000 10,000 70GroundwaterMW-1 11/30/2005 97.43 3.40 94.03

Monitoring WellIdentificationDateTop of Well CasingElevation (TOC)(feet)Depth toGroundwater(TOC)(feet)Table 1GROUNDWATER ELEVATIONS AND ANALYTICAL RESULTSShell Service Station # 137156900 Talcott Road, Park Ridge, IllinoisGroundwaterElevation(feet)Benzene(ug/L)Toluene(ug/L)Ethylbenzene(ug/L)Xylenes(ug/L)MTBE(ug/L)Tier 1 GRO forClass I5 1,000 700 10,000 70GroundwaterTier 1 GRO forClass IIGroundwater25 2,500 1,000 10,000 70MW-8 6/1/2006 93.09 12.00 81.09 4.93 3.51

Table 2SOIL ANALYTICAL RESULTSShell Service Station #137156900 Talcott Road, Park Ridge, IllinoisBoring #DateDepth(Feet)Benzene(mg/kg)Toluene(mg/kg)Ethylbenzene(mg/kg)Xylenes(mg/kg)MTBE(mg/kg)Tier 1 - SRO - Migrationto Class I GroundwaterTier 1 - SRO - Migrationto Class II GroundwaterTier 1 - SRO - Residential- Inhalation0.03 12 13 150 0.320.17 29 19 150 0.320.8 650 400 320 8800Tier 1 - SRO - Residential- IngestionSB-1SB-2SB-3SB-4SB-5SB-6SB-7SB-8SB-9SB-10SB-11SB-12SB-12SB-13SB-14SB-1512 16,000 7,800 160,000 7808/12/2005 3 0.2 0.124 17.8 1.23

Corrective Action Completion Report IEMA No. 20051292Shell Service Station # 137156900 W. Talcott Road, Park Ridge, IllinoisAPPENDIX AIEPA LETTER DATED DECEMBER 13, 2006

fluorosis at age eight years amongst children in counties Sligo and Leitrim 21 22 . These findingssupport those of international research 23 24 which indicate that early use of fluoride toothpaste ininfants leads to excessive ingestion and absorption of fluoride at a time when the enamel of thepermanent teeth is forming, leading to fluorosis of the permanent incisor teeth. It is importantto disseminate the recommendations of the Forum on Water Fluoridation (2002,www.fluoridationforum.ie) regarding the rational use of fluoride toothpaste. The reportrecommends:• The continued use of fluoride toothpaste in fluoridated and non-fluoridated areas becauseof the additive benefit from the combination of fluoridated water and fluoride toothpaste.• Parents should be advised not to use toothpaste when brushing their children's teeth untilthe age of 2 years. Prior to this age parents can brush their children's teeth with atoothbrush and tap water. Professional advice on the use of fluoride toothpaste should besought where a child below 2 years of age is considered to be at high risk of developingdental decay.• Parents should supervise children aged 2 to 7 years when brushing their teeth and shouldensure that only a small, pea-sized amount of fluoride toothpaste is used and thatswallowing of the paste is avoided.Adherence to these guidelines is expected to minimize the occurrence of dental fluorosis and atthe same time maintain the important caries preventive benefits experienced to date. There is aneed for constant monitoring of dental fluorosis in Ireland. In particular the impact of thereduction in the level of fluoride in public water supplies from the present level (between 0.8and 1.0 ppm) to between 0.6 and 0.8 ppm, with a target value of 0.7 ppm should bemonitored.Developmental Defects of EnamelFluorosis is not the only cause of visual changes in the enamel. There are several types ofdevelopmental defects of enamel. All such defects (including fluorosis) were categorised andmeasured using the Developmental Defects of Enamel Index (DDE index) 25 using natural lightfor the anterior teeth. On posterior teeth the DDE index was recorded using a portable dentallight source. Results are presented here (Table 7). As a general rule of thumb, dental fluorosisusually falls into the ‘diffuse opacities’ category. Over one third of children had at least oneopacity on their permanent teeth. The prevalence was highest among 15-year-olds where 62%,50% and 52% of adolescents in the fluoridated RoI, non fluoridated RoI and NI groupsrespectively had at least one opacity on their teeth. Diffuse opacities were the most commontype found in fluoridated and non fluoridated areas in RoI and in NI. Pairwise statistical analyses(Chi Squared Test for large numbers and Fishers Exact Test for sparse tables) of the difference inthe prevalence of opacities according to type within age group were carried out between:RoI fluoridated groups and RoI non-fluoridated groupsRoI fluoridated groups and NI non-fluoridated groupsRoI non-fluoridated groups and NI non-fluoridated groupsThe statistically significant differences are indicated in Table 7. Based on the work of Dean 26 ahigher prevalence of diffuse opacities is to be expected among children in fluoridated areas.Diffuse opacities were generally more prevalent among children and adolescents with alifetime’s exposure to fluoridated water when compared with the non-fluoridated RoI and NIgroups (p