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UNITED STATES ENVIRONMENTAL PROTECTION AGENCYREGION 10

1200 Sixth AvenueSeattle, Washington 98101

FIVE-YEAR REVIEWTACOMA TAR PITS SUPERFUND SITE

TACOMA, WASHINGTON

I. PURPOSE OF THE FIVE-YEAR REVIEW

Region X of the United States Environmental Protection Agency (EPA) has conducted a Five-Year Review of the Tacoma Tar Pits Superfund Site (the Site is actually a separate operableunit of the COMMENCEMENT BAY NEAR SHORE TIDE FLATS) (the Site), and preparedthis report consistent with the requirements of Section 121(c) of the ComprehensiveEnvironmental Response, Compensation, and Liability Act (CERCLA) and in Section300.430(f)(4)(ii) of the National Contingency Plan (NCP).

By definition, this is a Statutory Review. The purpose of a Five-Year Review is to ensure that aremedial action remains protective of public health and the environment and is functioning asdesigned. This review (Type I) is applicable to a site at which considered to have completedconstruction but at which continued ground water monitoring is ongoing quarterly. This Five-Year Review was conducted pursuant to the Office of Solid Waste and Emergency Response(OSWER) Directives 9355.7-02 [May 1991], 9355.7-02A [July 1994], and 9355.7-03A[December 1995]. This Five-Year Review is consistent with these OSWER Guidancedocuments.

II. SITE LOCATION AND DESCRIPTION

The Tacoma Tar Pits is an Operable Unit of the Commencement Bay-Nearshore/TideflatsSuperfund site located within the Tacoma Tideflats industrial area near Commencement Bay(Figure 1). The site comprises approximately 52 acres and is bounded by the Union Pacific andBurlington Northern railroad tracks on the north and south, respectively; a former demolishedmeat packing plant on the west (currently used for temporary stockpiling of demolition debris);and a natural gas regulator station and cardlock service station on the east. A metal recyclercurrently occupies a portion of the site. The site lies over filled tide flats (clay deposits) and wascreated by the placement of a variety of fills. Excavation of the site during remediation indicatedthat the fills generally ranged in thickness from approximately three to twelve feet. The lowerportion of the fill materials were saturated with water.

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Near the turn of the century, imported or dredge fills were placed in the vicinity of the site. Thefills provided foundation support for structures associated with a meat packing plant, a bulk fuelstorage facility, and various railroad tracks (Figure 2). Construction of the railroad tracks, meatpacking plant, and bulk storage facility was completed prior to construction of a manufacturedcoal gasification plant on the eastern portion of the site. The manufactured gas plant (MGP)operated on the site from 1924 through 1956. Some of the materials from the MGP (coal ash,coal tar liquor, and coal tar solids and semisolids) were deposited on-site. Demolition of theMGP was completed in 1966. Demolition debris and below grade structures were left in-place.

In 1967, a metal recycler purchased the site and began construction. As part of construction andoperation of the metal recycling facility, a variety of new fills were placed in a generallysoutherly and westerly direction. These fills, originated from a variety of sources including a fillwhich consisted of metal debris, soil, and shredded car interiors (autofluff). During the earlyoperational history of this facility, metals, largely from automobiles and transformers, wererecycled. When transformers were recycled, the oil typically contained polychlorinatedbiphenyls (PCBs) and PCBs were released to the site. The metal recycler is still operating on thesite. Autofluff and materials containing PCBs are no longer being generated, recycled or releasedat the site.

The site (Commencement Bay Nearshore Tide Flats) was placed on the NPL on September 8,1983.

III. SITE HISTORY

Early Investigations

In 1981, as part of an overall evaluation of the Commencement Bay-Tideflats area, EPAanalyzed aerial photographs. This analysis indicated the presence of ponds which potentiallycontained waste materials from the coal gasification plant. Also in 1981, the Washington StateDepartment of Ecology (Ecology) conducted a site inspection which noted oil runoff into theNorth Pond (Figure 2) and the accumulation of car interior fill (autofluff).

As a follow-up to the work completed in 1981, an EPA Field Investigation Team (FIT)conducted a perimeter inspection of the Tar Pits site. Based on information collected during theinspection and other background data, a Potential Hazardous Waste Preliminary Assessment wascompleted which reported a potential hazard to the environment through contamination ofsurface water.

Surface water (Burlington Northern ditch) and shallow ground water ultimately flow into thePuyallup River which is not used for drinking water purposes in the vicinity of the site. Cleanuplevels for surface and ground waters were primarily developed based on protection of freshwateraquatic life in the river.

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Shallow ground water in the vicinity of the site is not used for drinking water purposes and it isunlikely that wells will be installed in the future because of the industrial nature of the area andthe availability of municipal water. Deeper aquifers (generally deeper than 400 feet) are tappedby wells in the area, however, upward vertical gradients between the deeper and shallow zonesreduce the potential for downward migration of contaminants into the deeper zones.

At the request of EPA, the property owners (Burlington Northern Railroad Company, JosephSimon and Sons, Inc., and the Hygrade Food Products Corporation) conducted a preliminaryinvestigation. A draft report was issued in May 1983. The reported indicated that tar, aby-product of the coal gasification process, PCBs and lead were present on the site.

In September 1983, an EPA contractor (GCA Corporation) submitted a final report entitledTacoma Tar Pit Scope of Work for a Remedial Investigation/Feasibility Study for Enforcement.Based on review of the GCA document, Harding Lawson (HLA), an EPA contractor, prepared aFinal Work Plan for a full Remedial Investigation (RI) and Feasibility Study (FS). HLAmobilized to the site in September 1984 to begin the Field Investigation.

Subsequent to HLA beginning the field work, EPA reached agreement with the PotentiallyResponsible Parties (PRPs) that allowed the PRPs to conduct their own RI/FS. Four companiesjoined in commissioning the RI/FS; Washington Natural Gas Company, Joseph Simon and Sons,Hygrade Food Products Corporation, and Burlington Northern Railroad Company. Thesecompanies contracted Applied Geotechnology Inc. to complete the RI. AGI mobilized to the siteand commenced field operations in November 1984. The same companies contracted with theEnvirosphere Company (now Foster Wheeler) to complete a Feasibility Study and RiskAssessment.

Early Actions and Enforcement activities

After completion of site investigations, including a Remedial Investigation (RI) and FeasibilityStudy (FS), a Record of Decision (ROD) was issued (December 1987) for the site. The selectedremedy anticipated excavation and stabilization of approximately 45,000 cubic yards, on-sitereplacement of the stabilized material, and placing a low permeability cover over the stabilizedmaterial to minimize infiltration of surface water. This work was to be completed in the CAParea shown on Figure 2.

An Administrative Order (EPA Docket No. 1088-09-35-106) for implementation of certainresponse actions at the Tacoma Tar Pits Site, including, treatability studies leading to a remedialdesign, and remedial action was issued by EPA to the Washington Natural Gas Company andJoseph Simon and Sons in September 1988. The companies began the work required by theorder. Amendments to the order, largely associated with schedule modifications and extent ofcontamination studies, were issued by EPA in October and December 1988 and June 1989.

Issues between EPA and the companies named in the Administrative Order and other PotentiallyResponsible Parties as to schedule and allocation arose during 1988 and 1989. Settlementdiscussions were conducted which resolved the issues and a Consent Decree (No. C89-155TB)between. EPA and the Washington Natural Gas Company was lodged with the Court in October1991. The Decree, among other provisions, provided that the Washington Natural Gas Company

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would be responsible for designing and implementing the necessary response actions at the site.

Record-of-Decision (ROD)

On December 31, 1987, the EPA Regional Administrator approved a ROD requiring thefollowing remedial objectives/major cleanup elements: The description of the selected remedy in the ROD is as follows:

1. Excavation and treatment of all contaminated soils considered to be ExtremelyHazardous Wastes (EHW) which is defined for this site as exceeding 1 percent(10,000ppm) total PAH.

2. Excavation and treatment stabilization of all surface soils (less than 3 ft. depth)containing contaminants that exceed 1x10-6 lifetime cancer risk level

3. Reduction of surface water infiltration and human exposure to stabilized soils by cappingwith a low permeability asphalt cap.

4. Reduction of surface water transport of contaminants by channeling and managingsurface water run-on and run-off.

5. Removal and treatment of ponded water to achieve clean up goals.6. Provisions for institutional controls to assure cap integrity and prevention of future use of

contaminated on site groundwater.7. Provisions for continued groundwater monitoring to evaluate the effectiveness of the

remedial action and to evaluate the need for potential groundwater extraction andtreatment.

ROD Clean up Goal Performance Standards

Surface Water @ the Site boundary

Lead - 3.2 ug/lPCBs - 0.2 ug/lROD PAHs (total) - 30 ug/1ROD PAHs (individual) - 5 ug/lBenzene - 53 ug/l

Ground Water (sand and fill aquifers)Lead - 50 ug/lPCBs - 0.2 ug/lROD PAHs (total) - 30 ug/lROD PAHs (individual) - 5 ug/lBenzene - 53 ug/l

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Soil

Lead - 166 mg/kgPCBs - 1 mg/kgROD-PAHs (a) - 1 mg/kg (individual)ROD-PAHs (a) - 5 mg/kg (total)Benzene - 56 mg/kg

(a) ROD PAHs include benzo(a)pyrene, benzo(a)anthracene, benzo(b)fluoranthene,benzo(k)fluoranthene, dibenzo(a,h)anthracene, and indeno(1,2,3-cd) pyrene.

ESD / Framwork for Remediation / SOW /Extent of Contamination Study

As part of settlement discussions between EPA and WNG, a document titled Framework forRemediation was prepared. This document and the ROD formed the basis for the Statement ofWork that was attached to the Consent Decree that formalized the terms of the settlement. TheStatement of Work contains the performance criteria and other information used to prepare andimplement the remedial design.

These documents, as part of the settlement between EPA and the WNG required that a number ofsignificant but not fundamental changes be made to the remedy contained in the original ROD.These changes were documented in an Explanation of Significant Differences documentprepared by EPA. The changes included increasing the volumes excavated and stabilized toapproximately 79,000 cubic yards (from 45,000 cubic yards) and expanding the remediationarea. The ESD also modified how different area of the site would be excavated and treated.Application of the ROD soil criteria was based on soil data collected as part of the RemedialInvestigation and Extent of Contamination Study and varied with area as summarized below.

Ponds and Tarpit/Boil Areas. Soils, sediments and tarry materials to be excavated to a depth of3-feet.

Fluff Area. Fluff (autofluff) to be excavated to a depth of 3-feet.

Operating Area West. Soils which exceed the ROD criteria in Operating Area West of themetal recycling facility to be excavated to a depth of 3-feet.

Peripheral Areas. Surface soils and soils within a depth of 3-feet will not exceed the RODcriteria based on the geometric mean for lead and arithmetic average for PCBs, ROD-PAHs andbenzene. The maximum concentration (of ROD parameters) will not exceed 2-times the MethodA Soil Cleanup Levels - Industrial Soil listed in WAC 173-340-745(2)(a)(i) of the WashingtonState Model Toxics Control Act. The maximum Peripheral Area concentrations are listed below:

Lead -2,000 mg/kg ROD-PAHs -40 mg/kg

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PCBs - 20 mg/kgBenzene - 1 mg/kg

Operating Area East (also termed Area C in the Statement of Work). Soils which exceed thehot-spot soil criteria described in the Framework for Remediation (DOF 1991) will be excavatedto a depth of 3-feet. Hot-spots were defined as soils exceeding the following concentrations:

Lead - >4,000 mg/kgPCBs - >50 mg/kgROD PAHs- >113 mg/kg

Note: > - greater than indicated value.

A hot-spot action level for benzene was not developed for Operating Area East because benzenewas not detected during the Extent of Contamination Field Study.

Excavation of EHW. For all areas of the site, including soil depths greater than 3-feet, therequirement to excavate any material designated as Extremely Hazardous Waste (EHW) was notmodified. The target of the criteria were tarry materials from the historic coal gasification plant.EHW for the site was defined as materials exceeding 1 percent total 4-, 5-, and 6- ringed PAHsbased on Washington State Dangerous Waste Regulations (WAC 173-303-102).

Revised ESD

A revised ESD was issued in 1995 based on field conditions encountered during remediation.These changes included modification of treatability mixes, covers and schedule, and increasingthe excavation volume to approximately 185,000 cubic yards and associated cost.

IV. REMEDY IMPLEMENTATION

Components of the Remedy

The major components of the remediation are described below. A site plan showing the post-remediation site features is presented in Figure 6.

Excavation

Excavation of soil, autofluff and tarry materials containing ROD indicator contaminants abovecleanup levels was completed to remove these materials from the environment. Within the CAParea (Figure 2) identified in the ROD (or stabilization area identified in the Framework forRemediation), all materials above a depth of three feet were excavated. In the JS&S OperatingArea and Peripheral Areas (Figure 4) hot-spots were excavated from depths of 0.5 feet to 3 feet.In some areas where potential Extremely Hazardous Waste (EHW) was encountered, excavationwas completed below a

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depth of three feet.

To facilitate excavation of the North and South Ponds, sheet piling was installed around eachpond. The sheets provided a contained area to accomplish the excavations and, in the case of theNorth Pond, provided temporary storage for excavated tarry materials from the South Pond andother areas of the site.

Screening and Stockpiling

As material was excavated, it was stockpiled to facilitate sampling (for benzene and moisturecontent) and processing. Oversize debris (wire, metal, concrete, wood etc.) was encounteredbeneath much of the site. This material was screened and manually picked to remove oversizematerial prior to treatment. The oversize material was stored in separate stockpiles.

Stabilization and Placement of Excavated Materials

According to the ROD, an estimated 45,000 cubic yards of material would be excavated andstabilized at the site. This estimate assumed that not all soil in the CAP area would requireexcavation and did not account for additional contaminated material in the Peripheral or JS&SOperating Areas. As part of design, the volume was increased to an estimated 78,600 cubic yardsbased on sampling completed after the ROD was issued, which was documented in the originalESD.

During construction, because of expansion of hot-spot excavations, such as the BN ditch, andidentification and excavation of more EHW tarry material than originally estimated, a total ofapproximately 185,170 cubic yards of non-tarry soil, auto fluff and tarry material wereexcavated. Another 14,870 tons (11,336 hazardous and 3,530 non-hazardous) were disposed ofat offsite landfills. These latter materials consisted of over-size debris too large to stabilize andresidual soil from BMP area demobilization.

Excavated materials were stabilized using either a pug mill or a custom designed and built BatchMix Plant (BMP) equipped with a Nikko high intensity mixer. The pug mill was used to stabilizenon-tarry autofluff and nontarry soil excavated through June 1993. The material was stabilized.using a 7.5% to 10% (depending on moisture content) Portland cement mix to produce a rollercompactable material. After mixing, the material was transported, spread and compacted usingconventional construction equipment.

Tarry materials were stabilized in the BMP using a mixture of Portland cement and theproprietary ingredient P-27 manufactured by the Silicate Technology Company (STC). AfterJune 1993, non-tarry materials were also treated in the BMP.

As with the pug mill, the BMP produced a roller compactable material. The mixed material wastransported, spread and compacted in a similar manner as for the pug-mill mixed materials.

During material handling, oversize debris consisting of metal, wire, wood and concrete wasseparated from the materials to be stabilized by screening and picking. These oversize materials

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were disposed of in the following manner.

Oversize non-tarry material (except wood) separated from the autofluff wasentombed in the pile. This was accomplished by creating a bermed area withstabilized material, placing the oversize material in approximately a one-foot lift, andmechanically mixing the metal with a castable grout using a backhoe. After the groutset-up, several lifts of roller compactable materials were placed over the bermed area.

Some non-tarry oversize debris consisting of metal, rock and asphalt separated fromsoil was also entombed in the pile by placing the material in thin lifts and placingroller compactable material around and above the layer.

The remaining non-tarry oversize debris (e.g., wood) and tarry oversize debris wasdisposed of off-site. Non-tarry material was disposed of at the permitted RegionalDisposal Company’s facility located in Roosevelt, Washington. The tarry oversizematerials were disposed of at the Chemical Waste Management facility in Arlington,Oregon.

Cover Materials

Addition of a Multi-Layered Geosynthetic Cover and Concrete Pavement: The RODspecified that a low-permeability asphalt cap be installed over the stabilized waste. However,concerns regarding the ability to meet the Statement of Work permeability requirement of 1E-7centimeters per second (cm/sec.) on the side slopes of the waste pile and the long-term durabilityof asphalt led to the use of a multilayered geosynthetic cover for the waste pile area.

Concerns were also raised about the long-term durability of an asphalt pavement in parts of theJS&S metal recycling area. Based on this concern, a cement concrete pavement was constructedin parts of the operating area. Low-permeability asphalt was placed in other portions of the JS&SOperating Area and around the waste pile perimeter.

Therefore, the remediated site was divided into four areas including the waste pile footprint,metal recycling facility, detention basins, and peripheral areas. The covers vary depending onlocation and area use.

Waste Pile Footprint. The stabilized waste pile (Figure 6) is covered with a low permeabilitycover. The cover is composed of two low permeability geosynthetic layers (two layers of 60-milHDPE on side slopes and 60-mil HDPE over GCL, a bentonite impregnated fabric, on the wastepile top) with associated geosynthetic drainage layers, covered by soil and turf.

Metal Recycling Facility. Asphalt or concrete paving was placed to cover the JS&S metalrecycling area (Figure 6). The asphalt paving consists of at least 1.5-inches of low permeabilityasphalt protected by at least 1.5-inches of a wearing asphalt. Concrete, generally 8-inches inthickness, was placed in the anticipated high wear areas of the metal recycling area.

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Detention Basins. Two detention basins were constructed as part of the remediation. Thedetention basins are lined with low permeability asphalt with a permeability of less than 1E-7cm/sec. The asphalt in each basin has a minimum thickness of three inches.

Peripheral Areas. Hot-spots in the Peripheral Areas (Figure 4) were excavated and generallybackfilled with imported uncontaminated sand and gravel. Portions of Peripheral areas A-1 andD-1 are covered by either asphalt or concrete which were installed as part of construction of thecardlock fuel station. A drainage ditch (known as the BN ditch) lies between the TarPit/Fluff/Ponds Areas and Peripheral area D4 (Figure 4). The ditch was excavated to a depth ofthree feet and reconstructed with filter fabric, imported sand, gravel, and rip-rap.

Stormwater Drainage System

Two stormwater drainage systems were installed as part of the remediation; the waste piledrainage system and the metal recycling drainage system. The systems consist of a series ofcollection facilities which ultimately route water to the BN ditch. Restricting orifices anddetention basins were installed based on the requirements of the City of Tacoma. The detentionbasins were designed to handle a 25-year return period storm.

Waste Pile Drainage System. This system collects stormwater which falls on the coveredstabilized waste pile. Drainage from the pile is collected by box culverts placed at the toe of thepile slopes. The bottoms of the box culverts are sloped to direct stormwater flow to detentionbasin No. 1 via a buried culvert (north side) and asphalt lined ditch (south side). Water whichcollects in detention basin No. 1 flows into the BN ditch via a control manhole equipped with arestricting orifice (maximum 0.5 cubic feet per second).

Metal Recycling Drainage System. A separate drainage system was installed for the metalrecycling facility. The system consists of a series of catch basins and buried pipes which directflow to a control manhole located near the southeast corner of detention basin No. 2. Flow fromthe facility is into the BN ditch and is controlled by a restricting orifice (maximum 1.0 cubic feetper second). If stormwater volumes exceed the flow allowed through the orifice, water backs-upinto detention basin No. 2.

Stormwater Treatment and Discharge

In August 1992, an NPDES Construction Storm Water Substantive Requirements permit foroff-site discharge of storm water during remedial construction activities was issued by theWashington State Department of Ecology. Testing of the plant occurred in March 1993 and thefirst discharge of treated water occurred in June after approval was received from the City ofTacoma. The discharge criteria are listed in Table 2.

For most of the treatment period, water was treated in batches and stored in a detention basin ormodular tank. Water was discharged after an analysis of a sample of the treated water indicatedthat the permit discharge limits had been met.

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In August 1994, EPA approved direct discharge of treated water. This change was made basedon operational experience and the reduced strength of the water being treated (water wasgenerally from paved or covered areas).

Summary of Remedial Quantities

• Excavation and Stabilization Quantities: 185,170 cubic yards• Waste Pile Cover Area: 295,000 square feet• Area Covered by Low-Permeability Asphalt: 118,900 square feet• Area Covered by Concrete: 191,900 square feet• Volume of Water Treated: 7,000,000 gallons

• Off-Site Disposal - Chemical WasteManagement, Arlington, Oregon: 11,336 tons

• Off-site Disposal - Regional DisposalCompany, Roosevelt, Washington: 3,530 tons

Pre-Certification Inspection

A pre-certification inspection was completed on June 14, 1995 as required by the ConsentDecree. The inspection was attended by representatives of EPA, CH2M Hill (an EPAcontractor), Washington State Department of Ecology, and Dalton, Olmsted & Fuglevand, Inc.(representing WNG).

Based on observations made during the inspection, it was concluded that the major elements ofthe remedial action were complete. However, a few minor construction activities remained to becompleted.

Final Inspection

The final inspection for the site was completed on July 26, 1995. Based on the inspection, EPAaccepted the construction as complete and WNG was instructed to proceed with preparation ofthe Remedial Action Report.

Inspection and Maintenance

Consistent with the Consent Decree and Statement of Work, an Inspection and Maintenance Planwas prepared and finalized in July 1995 (Foster Wheeler 1995). The plan calls for periodicinspections of the various components constructed during the remediation. Necessarymaintenance will be conducted, as appropriate, based on the inspections. The first inspectionsunder the plan were completed in September 1995.

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Post-Remediation Water Quality Monitoring

During implementation of the remedy, monitoring was completed to establish the baselinegroundwater quality conditions beneath the Tacoma Tar Pits site. This monitoring wascompleted quarterly in the years 1991 to 1994. Using the baseline monitoring data, a Post-Remediation Water Quality Monitoring Plan was prepared. The first round of sampling wascompleted in January 1995 and has been sampled every quarter since.

Monitoring is being completed in twenty-nine wells and one surface water location. The wellsare distributed around the site and are screened in a shallow water table aquifer and two deeperzones. One of the wells (located on the Hygrade property) is a deep (greater than 500-feet deep),flowing artesian water supply well.

Sampling and analyses of site indicator contaminants are being conducted on a quarterly,semiannual, or annual basis depending on the sampling location and monitoring constituent.Sampling is being conducted in January, March, June, and September.

Samples are being analyzed for the following constituents:

• Field parameters (water level, pH, electrical conductivity, temperature and turbidity);• Benzene, toluene, ethylbenzene, and xylenes;• Polycyclic aromatic hydrocarbons (PAHs);• Polychlorinated Biphenyls (PCBs); and• Dissolved and total lead and cadmium.

The first major evaluation of post-remediation water quality data was scheduled to be completedafter two years of data had been collected in early 1997. The data was compared to the RODcleanup levels using a modified CUSUM approach developed by Johnson of EPA in 1988. Basedon the results of this methodology the need for additional (groundwater) remediation would bedetermined and modifications to the monitoring program would be made, as appropriate.

Summary of Project Costs

The ROD anticipated a capital cost of $3.4 million. Based on additional sampling and designwork, the estimated capital cost rose to between $15 and $18 million prior to the start ofconstruction work. The major components affecting cost included increases in the

• Unit cost of remediation and chemical additives,• Volume of material to be excavated and stabilized,• Size of the capped area,• Associated materials handling effort, and• Scope of engineering and management of the project.

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These changes are documented in the original ESD dated November 1991.

During completion of the Remedial Action the project costs rose to approximately $39 milliondollars as generally summarized below. A more detailed cost summary is presented in Table 3.The changes which resulted in the increased costs are discussed in Section 4.6 and aredocumented in a revised ESD dated May 1995.

Construction $29,804,000 Design, Coordination and Management 4,363,000 Other Costs (pre-decree expenditures, oversight etc.) 5,152.000Total $39,319,000

The increase in cost is primarily the result of extra costs associated with excavation andstabilization of the additional volume of material

V. SUMMARY OF THE FIVE-YEAR REVIEW

The Five-Year Policy Review was conducted according to the procedures in OSWER Directive9355.7-02, Structure and Components of Five Year Reviews. Activities in this review consistedof:

1. Review of site-related documents and agreements;

2. Review of monitoring data;

3. Site visit and inspection (the most recent site visits occurred on July 8, and 22,1998, and included a site walk-through with EPA, WDOE, and Trust personnel);

4. Community relations activities; and

5. Preparation of this Five-Year Report

VII. DOCUMENTS REVIEWED FOR THIS REPORT

AGI (Applied Geotechnology Inc.), 1987, Remedial Investigation, Tacoma Tar Pits, Tacoma,Washington, prepared for Washington Natural Gas Company, Joseph Simon & Sons, Inc.,Hygrade Food Products Corporation, and Burlington Northern Railroad Company, September1987.

Dalton, Olmsted & Fuglevand, Inc., 1991, Framework for Remediation prepared for theWashington Natural Gas Company, September 1991.

Dalton, Olmsted & Fuglevand, Inc., 1995, Post-Remediation Water Quality Monitoring Plan;September 1995.

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Ebasco, 1990a, Bench-Scale Treatability Study, Ebasco Environmental, A Division of EbascoServices, Inc., Bellevue, Washington, January 1990.

Ebasco, 1990c, Extent of Contamination Field Study, Ebasco Environmental, A Division ofEbasco Services, Inc., Bellevue, Washington, November 1990.

EPA (Environmental Protection Agency), 1987, Record of Decision, Decision Summary andResponsiveness Summary for Final Remedial Action, Commencement Bay -Nearshore/Tideflats, Tacoma Tar Pits Site, Tacoma, Washington, December 1987.

EPA, 1988, Administrative Order, EPA Docket No. 1088-09-35-106, September 30, 1988.

EPA, 1988, Administrative Order Amendment (No. 1), EPA Docket No. 1088-09-35-106,October 14, 1988.

EPA, 1988, Administrative Order Second Amendment, EPA Docket No. 1088-09-35-106,December 1, 1988.

EPA, 1989, Administrative Order Third Amendment, EPA Docket No. 1088-09-35-106, June 6,1989.

EPA, 1991, Consent Decree for Settlement Between the United States of America andWashington Natural Gas Company, No. C89-155TB (Consolidated with C89-489TB andC90-5373B), Lodged with U.S. District Court, Western District of Washington at Tacoma onOctober 4, 1991.

EPA, 1991, Explanation of Significant Differences for the Tacoma Tar Pits Site, November 1,1991.

EPA, 1995, Revision of Explanation of Significant Differences for the Tacoma Tar Pits OperableUnit, May 9, 1995.

Envirosphere Company, 1987, Feasibility Study of the Tacoma Historical Coal Gasification Site,Final Report, July 1987.

Foster Wheeler, 1995c, Inspection and Maintenance for the Tacoma Historical Coal GasificationSite, Manual, prepared for the Washington Natural Gas Company, July 1995.

Johnson, B., 1988, Approaches for Long-Term Monitoring of the Groundwater, Surface Waterand Soils at the Tacoma Tar Pits Site. EPA Interoffice Memorandum l7pp.

Dalton, Olmsted & Fuglevand, Inc., 1995THCG, Remedial Action Report prepared for theWashington Natural Gas Company, September 19951.

Dalton, Olmsted & Fuglevand, Inc., 1995-1998, THCG, Water Quality Monitoring Reports,1995-1998 prepared for the Washington Natural Gas Company.

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VII. Community Relations

There has been no recent community involvement from EPA nor have there been interestexpressed from the community. This site is located in a heavily industrialized part of Tacoma.There are no residences for a few miles. Periodic Fact Sheets were mailed out to a substantial listof potentially interested parties including people from the Commencement Bay interest groups.To date no responses, other than from the actual PRP’s have been received. This 5-year reviewwill become part of the site file and be available for public review.

VIII. SITE CONDITIONS

Site Visit

As part of a regular annual inspection, a site visit was made by Lee Marshall, RPM and MatthewDalton (Project Coordinator for Puget Sound Energy). This visit was made in September 1997.An earlier site visit was also made during the summer of 1996. All areas of the site wereobserved including the covered stabilized waste pile, stormwater detention basins and BurlingtonNorthern Ditch, and the metals recycling operation (Joseph Simon & Sons). Overall the siteappeared to be in good condition with no substantial changes from the previous year visit. Averbal report of the 1998 annual inspection indicates conditions are essentially the same (DaltonTelephone Report Sept.1997) as all previous inspections.

Covered Stabilized Waste Pile Area. The vegetative cover is firmly established. The concretebox culverts that surround the pile and receive runoff were clear and free flowing. Fencing, gatesand signs were in good condition. The primary maintenance activity associated with this area isto mow the grass and ensure that the stormwater drainage pathways remain clear and freeflowing.

Stormwater detention basins and Burlington Northern Ditch. Two asphalt lined detentionbasins receive stormwater from the stabilized waste pile and the metal recycling area. Bothbasins flow into the Burlington Northern Ditch. The asphalt surfaces appeared to be in goodcondition with no obvious settlement or deterioration. Vegetation has grown in a portion of theBurlington Northern Ditch and will be removed to ensure that the ditch remains free flowing.

Metal Recycling Area. The features of concern in the metal recycling area are pavements(asphalt and concrete) that restrict the infiltration of water and the drainage system (catch basinsand buried pipes) that receive stormwater runoff. The pavements are in generally good conditionwith not much obvious change from the previous years inspection. Conversations with the siteoperator indicate the drainage system is functioning as intended. As part of the routinemaintenance activities, the catch basins are inspected and any accumulated sediments in the

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basins are removed.

IX. CLEANUP GOAL ATTAINMENT

Cleanup Performance Goals/Standards

All physical work required by the ROD, SOW, The Consent Decree, ESD, The Framework ForRemediation, and the Revised ESD, were completed in a completely satisfactory manner. Allsoils specified were excavated and treated or otherwise removed from availability. The testing ofthe treated soils with respect to physical characteristics such as leachability, comprehensivestrength, permeability, etc. all passed the minimum standards. The covers have been tested andmeet all the standards. The required institutional controls in the form of deed restrictions havebeen implemented and the construction accepted as complete. The I&M program has beensatisfactorily implemented. The water quality monitoring program is functioning as designed andresults from the analysis indicate that the ground water performance goals are not being met inthe sand and fill aquifer as noted in samples from two wells.

Ground water discussion/ non compliance

Recent quarterly water monitoring data for the Tacoma Tar Pits site show increasingconcentrations of contaminants, primarily benzene, in two areas along the site boundary at wellsTTP-18M and TTP-3M. An evaluation of the monitoring data using the CUSUM statisticalmethods indicates that further field investigation of the extent of contamination and need forremediation in those areas is warranted. At the same time, other areas along the site boundarycontinue to show decreases in concentrations indicating that the two problem areas do not appearto be representative of the whole site boundary. Data from 1991-1996 were reviewed as base linealong with the more recent data contained in reports by Dalton, Olmstead & Fuglevand. A briefsummary of the monitoring data received to date follows. Note that the July 1998 results arepreliminary, as the data are not yet validated. Also, it is important to note that the contaminantsobserved are generally associated with coal gasification.

Well TTP-18M - northeast boundary of site.

Quarterly monitoring data for benzene and other BTEX compounds have shown a gradualincrease in concentration in well TTP-18M beginning in early 1996. See Figure 7 for a graph ofbenzene in this well in comparison with other mid-level wells that monitor the sand aquifer. Thebenzene concentration in TTP-18M exceeded the ROD Standard level of 53 ug/L in early 1997and has increased since then to as much as 765 ug/L in the most recent sampling round of July1998.

An evaluation of the data using the CUSUM (Cumulative Summation) procedure established for

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this site shows that the upper bound statistical parameter SH(i) exceeded the reference value of 5in October 1997 and thereafter continued to increase in the next three sampling rounds (lowerpart of Figure 7). The reference value of 5 is the value above which there is an indication of astatistically valid exceedance of a compliance point. In this case, the parameter SH(i) is thestatistical measure designed to provide a decision-making basis and trigger for conductingadditional evaluation of ground water contamination and potential remediation.

In addition to benzene, other BTEX parameters (ethylbenzene and total xylenes) andnoncarcinogenic PAH’s (naphthalene) have shown increasing concentrations in TTP-18M. Thevalues and the increasing trend of benzene concentrations, accompanied by other increasingparameters, clearly establish a need for further action to determine the full extent of contaminantmovement, the direction of travel, the area affected, and the source.

Well TTP-3M - south boundary of site.

Quarterly monitoring data for benzene and other BTEX compounds have shown continued highconcentrations in well TTP-3M throughout the monitoring period. The concentration of benzenereached a peak of 2,600 ug/L in December 1994 and then decreased after completion of soilremediation. The decrease in benzene concentration has not been sufficient to maintain valuesbelow the reference of 53 ug/L, with the most recent concentration reaching 156 ug/L in July1998.

An evaluation of the data using the CUSUM statistical procedure shows that the CUSUMparameter SH(i) exceeded the value of 5 in September 1995. The record of benzeneconcentrations both in TTP-3M, and the adjacent monitoring well to the east (TTP-2M), whichalso exceeded the SH(i) reference value in September 1995, led to further field investigation in1996-97 of the extent of contamination in that area. Subsequent data show that, unlike TTP-2M,concentrations in TTP-3M are remaining at a high enough level to maintain continuedexceedance of the CUSUM SH(i) reference value.

In addition to benzene, other BTEX parameters (ethylbenzene and total xylenes), and non-carcinogenic PAH’s (naphthalene and acenaphthene) have maintained elevated concentrations inwell TTP-3M. The amount and trend of continued elevated benzene concentration, accompaniedby other parameters, establish a need to conduct additional field investigation also in theTTP-3M area to determine the full extent of contaminant movement with reference to thedirection of travel, the area affected, and the source.

Other Monitoring Points

As noted above, concentrations in well TTP-2M on the east boundary of the site have decreasedfollowing soil remediation with concentrations falling below the ROD standard of 53 ug/L inMarch 1997. The most recent measurement for benzene in TTP-2M was 1.12 ug/L in July 1998.

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CUSUM analysis of these data show that values for the SH(i) statistical parameters droppedbelow the reference level of 5 in March 1998.

No other areas monitoring points have shown exceedances of the CUSUM reference parameter.Of those areas that have continued to show fluctuations of contaminants, but at levels belowreference values, the surface water monitoring point near the southeast boundary has had acontinuing decrease in benzene concentration. The most recent measurement in March 1998 wasat the detection limit of 0.2 ug/L.

X. RECOMMENDATIONS

The monitoring data clearly demonstrate exceedances of the standards set forth in the ROD /ESD using the agreed statistical method (CUSUM) for evaluating compliance with thatrequirement. The two-year waiting period, following completion of construction, for dataevaluation has also been satisfied. As set forth in the enforcement documents WNG should beformally notified in writing of the status of our findings, which will set in motion the clock forthe PRP to produce a plan for Additional Response Action. A preliminary meeting with thecompany has already resulted in an identification of the problem and indications of a willingnessto proceed toward implementation of a cleanup strategy. The agreed upon first steps in such aplan would include a further characterization of the ground water to determine the full extent ofcontamination, direction of travel, area affected and the source.

XI. NEXT REVIEW

The next Five-Year Review will be conducted within five years of this review. Quarterly reviewsof the data will also be conducted.

XII. STATEMENT OF PROTECTIVENESS

I certify that the remedy selected for this site remains protective of human health and theenvironment. However, the remedy is not meeting the performance goals in the ROD, therefore,EPA will be implementing the provisions in the Consent Decree to have an additional responseaction initiated. Continued evaluation of the site will be maintained to assure continuedprotectiveness.