Engineers Planners Economists Si::ientists

September 17, 1986

W66238.IO

Mr. Jim Peronto Regional Project Manager Region VI Environmental Protection Agency 1201 Elm Street Dallas, Texas 75270

Dear Jim:

Subject: Submittal of Final FS Supporting Documentation Bayou Bonfouca RI /FS

we are pleased to submit the enc_;_osed information in response to your August 29, 1986, request. This information wa., prepared by Black & Veatch and is submitted in letter-form to supplement the FS and respond to specific concerns and issues raised during tt 0 e public comment period.

I believe that, with your ~pproval, we have completed our assignment for the Bayou Bonfcuca RI/FS with this s·1bmi ttal. I will be available to discuss this information or any questions you may hav~.

I look forward to working with you on another project.

Sincerely,

David E. Price

DEP2/041 Enclosure cc: Mike Harris/DFW

Gayle Lytle/WDC Keith Boyd/Black & Veatch

CH2M NILL Montgomery Office 2567 Falflone Or,ve. P 0. Box 230548 Monfgomary. Alabama 36123-0548

205 2711444

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BLACK 8c VEATCH ENGINEERS-ARCHITECTS

Mr. David Price 2567 Fairlane Drive Montgomery, Alabama 36104

Re: Response to Public Comments, Bayou Bonfouca

Dear Mr. Price:

TE~- 19131 339-2000

1500 MEADOW LAKE PARKWAY

MA!UNf.io ADDRESS P.O. BOX NO. 8405

. ANSA.S CITY, 'MISSOURI 64i 14

September 13, 1986

We have reviewed and studied the comments and supporting literature for the technologies identified in y0ur letter of August 29, l986. The following comments are offered for your consideration.

Temporary Bayou Diversion

The Feasibility Study (FS) report identified alternatives that addressed the need to remediate the contaminated sediments. Other than Alternative 1, No-Action, and Alternative 2, Bayou Diversion, all alternatives incorporated a scenario in which the contaminated Bayou reach was isolated from the noncontaminated sections. The isolation and draining of the Bayou wonld allow use of conventional earth moving equipment in excavating the contaminated sediments and placement. of a clay liner to separate the aquifer 2nd the restored Bayou. The liner was deemed nec~ssary to prevent recontami.nation of the Bayou should the artesian head of the aquifer increase relative to the Bayou. In planning the isolation construction sequenc~ provision for providing hydraulic continuity around the cont.aminated section to minimize adverse environmental i.mpacts.

Several methods o( providing this continuity were evaluated using the data available, The methods were:

o A temporary open-channel around the Rayou following the configuration for the new Bayou reach proposed in Alternative 2.

o Use of closed conduits or pipes.

o Physically splitting the Bayou longitudinally aad isolating one-half of the contaminated reach for remediation,

The open-channel method has the advantage of fa~ilitating greater flowb of water without significantly increasing hydraulic heads, (i.e,, the height of water). The channel can be easily and quickly constructed usl.ng conventional earth-moving equipment. Given the nature of the site topography (i.e., little relief with elevations slightly above mean sea level), the channel envisioned would be a shallow trapezoidal earth li:ied

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channel approximately 100 feet wide and 2 feet deep, although detailed design could result in a narrower channel after considering the critical elevations of structures in the area. This channel would be a wide swale with culverts for crossings for the one roadway in the area, The channel would be essentially flat, intersecting the bayou below low water level to allow for transmittal of tidal effects, It would intersect the upper Bayou reach at the low water level. Although tidal impacts on water elevations were slight, it was believed the wetlands area upgradient of the contaminated Bayou section would be negatively impacted if such tidal effects were not allowed to be transmitted.

The second method studied was the use of pipes to hydraulically connect the upper and lower reaches. The pipe(s) woul'.! allow the transmittal of tidal effects but would not as efficiently transmit inflows from precipitation runoff. Closed conduits are subject to clogging due to debris and sedimentation, requiring continuing maintenance. Site topcgraphy also limited the slope allowable for the pipe(s) and, therefore, limiting their capacity.

~he third method, splitting the bayou along its length, would allow cDntinued use of a portion of the Bayou. This method would require the driving of sheet piling to a depth at least twice the fill water depth (or approximately 30 feet) and through the contaminated aquifer. Disadvantage9 perceived with this method included potential for pile driving problems should stiff clay layers be encountered (these are known to be interbedded with fine sands of the aquifer) and the difficulty in sealing the clay layer between the two half sections. Dewatering of the isolated section could also be more difficult as the hydraulic head between the Bayou and the dewatered section would he much higher. The impact of this method on the contaminated artesian aquifer was also unknown. Stage heights (or elevations of the fre 0 water surface) would increase with this option and upgradient flooding would need to be evaluated. The advantages of this method include ease of diversion and elimination of the need for "offsite" land to use for a diversion channel.

Detailed analyJis of (the impact of isolating the Bayou) on the flooding potential and the impact of flooding in the immediate area were beyond the capability of evaluation of the FS, \.:e did attempt to measure the watershed and quantify the volumes of water needed to be managed. 1lut the watershed is quite large and affected by storm water management systems being used hy the City of Slidell. In addition, detailed topographic rr.aps of the watershed would need to be procured as well as existing stage records for the Bayou. Given the uncertainty of being able to dewater the bayou to the degree required for installation of the clay liner, and the need to be conservat<.ve in al lowing for minimal flooding impacts (remember the entire Bayou section under investigation is well below the lOO year flood level), we assumed the open channel method for all alternatives involving removal of the contaminated sediments.

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In subsequent discussions with project personnel, a fourth method involving construction of slurry walls and grout curtains and dewatering the aquifer in addition to the installation of sheet piling down the middle of the Bayou has evolved. This alternative appears feasible and eliminates some of the uncertainty associated with the aquifer - bayou interrelationship, Construction costs would most likely be higher than for the open channel alternative. However, a final recommendation would require a more detailed design of the two methods to identify which is more cost-effective. Either method would not impact the relative costs of any of Alternatives 3 through 6.

Infrared Incineration Technologv

!. review of information received from the developer of the Infrared Incineration System was performed. This technology utilizes infrared radiation to heat wastes to the appropriate temperatures for contaminant destruction. The waste material to be processed is conveyed through the f~rnace on a woven wire belt. Residuals of the process are gaseous products of waste combustion, some entrained particulates, and a solid residue. The inherent advantages of the system include a quiescent combustion zone for low particulate emissions, reduced air flows which reouire s~rubbing, up to SO percent turndown capability, and a high degree of control of waste residence times,

The technology has been used for municipal and industrial sludge incineration. A rilot-test unit is available (the unit has been used to destroy dioxin contaminated soil in a trial hum at Times Beach, Hissouri)and a full size mobile unit is under construction. The technology has been reported to be successful in treating creosote wastes at other facilities, according to the manufacturer, Shirco Infrared Systems.

In June, 1986, the manufacturer stated the first full scale mobile unit, rated at 100 tons per day or !,-5 tons per hour, is due to be "out of the srop" in late August. The unit will be owned by an entity other than Shirco and has been targeted for use at an oil-contamination site in Florida. Capital cost of the unit was estimated at SZ.5 million dollars, Construction times for additional units was estimated at 6 months from receipt of order. Permitting time for the unit was estimated to take hetween 4 and 12 months.

llecause the full scale mobile unit ),as net been demonstrated in the field, data from operating and maintenance (O&M) costs have been estimated by Shirco. using the pilot test unit, Including capi.tal amortization, the per ton O&}< cost is in the range of 5100 to S125 per ton. This cost does not include administrative costs, (e.g., insurance, marketing expenses, etc.) profit ~or allowance for taxes. These costs are d'fficult to predict, for a specific business but assuming a range nf 50 to 65 percent, in the field

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per ton cost approaches $200 per ton. Ancillary facilities required to support the unit include a foundation, an enclosure or building, a treatment system for waste gas liquid stream, a 480-volt, 3 phase power supply, suitable roadways into the site, and a material feed preparation system.,

The feed preparation system of the infrared system is critical as the waste material must be spread uniformly over the belt to a depth of I to 1.5 inches. Thicker layers of waste are not preferred due to the need to expose the particles to the infrared radiation. This is one difference between the infrared system and the rotary kiln units, which are capable of handling larger items such as contaminated vegetation without the need for particl2 size reduction. It is not known what degree of particle size reduction would be required for the heavy or fat clays found on the Bayou Bonfouca site, While rotary kilns are more flexible as to feed requirements, they require larger energy inputs in the form of fossile fuels which in turn create larger gas flows requiring cleaning.

A second concern is moisture content. The contaminated sediments from Bayou Bonfouca will be dewatered to approximately 40 percent solids. The large moisture fraction will increase waste gas quantities and may limit the feed rate (i,e., tons per hour) of sediment through the unit,

Given the data and information available on the infrared and rotary kiln mobile uni ts, it is difficult to assess the merits of each relative to Bayou Bonfouca. We are unaware of any EPA studies which observe either type of svstem as being ineffective in treating waste sludges, solids, or soils as found on Bayou Bonfouca. Vendors of mobile rotary kiln units have Seate~ per ton costs of between S200 to $500 per ton, with similar ancillary equipment and support services for the infrared system being reouired. The capacity of r.iohile rotary kiln units are in the same range as tre Shirco unit.

,le therefore believe the infrared incineration system is appropriate for tre Hayou Ronfouca site if feed sizing concerns can be resolved. As a Superfund Innovative Technology Evaluation (SITE) program participant, the unit has a great deal of potential in effectively managing contaminated soils.

\..'itJ-. respect to Shirco's comments on the on-site landfill alternative, we wish to make the rollowing clarifications:

c With respect to integrity of the cover and liner, it is difficult for us to envision the production of gas and acidic leachate in quantities or concentrations that would jeopardize the liner system, The quantity and '\ature of organics found are much

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different than, for example, the organic loading placed in a sanitarv landfill. The need for "frequent" or periodic inspection and repair at any solid waste disposal facility is paramount to ensuring the environment is indeed threatened against additional releases.

Adverse effects on land uses do include impacts on surrounding residential and commercial properties. What is being overlooked, however, is the need of a ground water control system on the site, using a cap to minimize infiltration. Such a capping system ~ust include controls and restrictions of land use as well as periodic or frequent inspection to ensure the cap's integrity. It is unlikely the property could be developed without extensive land use restrictions and precautions being implemented.

The waste attentuated or absorbed on the soil and sediment particles is largely immobile, based upon absorption analysis discussed in Appendix A of the Feasibility Study.

o Regarding economics and policy consistency, the National Contingency Plan and Superfund guidance documents establish the procedures used to perform the Feasibility Study. It is somewhat misleading to compare the landfilling of soil and sediment, contamin,ted with polynuclear aromatics in the part per billion concent r;,tion range over an isolated, limited aquifer contaminated with the same contaminants, with the landfilling of KOOl wood preserving bottom sediment sludges. These more concentrated and conf1.ned sludges can be effectively managed in ways other than landfilling, and they can represent a much higher threat of release to the environment if landfilled.

Riological and Phvsical/Chemical Treatment

The suggestion of using a liquid-solid biological reactor for treatment of contaminated soil and sediment was added to the list of technologies to be pre-screened, The concept is quite similar to the activated sludge treatment technologv used to treat municipal and industrial sewage. The contaminated solids !soil and Bayou sediment) would be suspended and aerated in liquid-solid contact basins. The aqueous feed would be innoculated with acclimated biological organisms which would treat the contal'linants throug\.-. endogenous respiration. Treated liquor would be ~umped to a clarifier for separation of solids and liquid, and the effluent would he discharged. The solids residue would be returned to the 1 iquid-sol id contact reactor( s) or "wasted" from the process. This would produce a solid waste residual which would require proper environmental

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oanagement (the waste stream could itself be listed as a hazardous waste). ~iterature supplied by vendors of this technology report success in treating creosote sludge with this process.

While this technology is viable and applicable to the treatment of creosote waste, it must still meet the evaluation criteria of technical feasibility, particularly performance and reliability. Biological treatment as presented in this technology is subject to the same constraints and limitations of the landfarming alternative. To prove reliability and performance, and to provide design infonnation to fully evaluate costs and time to achieve beneficial results, a pilot scale testing program would be required. Such a program would produce a model of the biological treatment scheme to be used to decide the appropriate number of reactors, nutrient levels, and waste residue treatment requirements. Perhaps the largest technical issue to be addressed, however, is the method and costs involved in suspending the excavated soil, Unless this question can be answered it would appear this alternative is not feasible for treating contaminated soil.

This issue does not apply to treating the contaminated Bayou sediments, wt,ich already are in a semi-suspended phase. Removing the sediments and pumping into a liquid-solid contact reactor can be achieved. Again, costs for such treatment of the sediments would be dependent on the results of a pilot testing program. Costs savings over landfarming the sediments include the cost for sediment dewatering ($275,000). Additional costs over the landfarm alternative include energy costs (for aeration of the basins) and disposal/management costs for the solids waste stream. Environmental Solutions, 1nc. has stated a cost of S50 per cubic yard of contaminated material, which would result in a treatment cost of ap.,roximately S2.3 "1il lion. The estimated cost for landfarming the sediment is roughly Sl.2 Million for biological treatment and maintenance and dewatering of the sludge (S20 per cubic yard for biological treatment and maintenance, approximately 45,600 cubic yards, plus $275,000 for dewntering). Given these rough approximations and recognizin~ the need for a pilot testing program to refine the S50 per cubic yard unit price, the liquid-solid contact alternative would not pass the preliminary screen and the landfarm (on-~ite) technology would he carried throu~h the Feasibility Study as the preferred biological treat~ent alternative, We must emphasize, however, the viahility of the technology and point out the need to further refine the estimated costs associated with it.

Another technology we re-evaluated for treatment of the contaminated streams was wet air oxidation. As reported in Treatment Technology Briefs (EPA/600/8-86/017, July, 1986), this technology is used to treat aqueous was<e streams with less than 5 percent or~anics and with some pesticides, penolics and organic sulfur, cyanide waste waters. It is not appropriate

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for solids or viscuous liquids, Waste streams from the Bayou Bonfouca site suitable for treatment by this technology would be the liquid waste streams resulting from sediment dewatering or ground water removal, The FS utilized conventional treatment (phasa separating, coagulation and carbon adsorption) in managing these waste streams because they had been reported in the technical literature as being effective in treatment of waste streams from similar creosote·contamination sites. The advantage of the conventional treatment system over the wet air oxidation system include reduced power consumption and demonstrated effectiveness. The spent/contaminated carbon must be managed at an off-site facility (the supplier of the carbon) whereas the wet air oxidation system oxidizes the waste products on-site, A liquid waste stream is produced by the wet-air oxidation pr.~ess which requires additional management. We believe the use of the conventional treatment process as identified in the FS remain as the preferred treatment scheme for the aqueous waste streams.

We hope these comments are of assistance in clarifying the Feasibility Study and in responding to the public comments, Please contact us if we can provide additional assistance.

Very truly yours,

BLACK & VEATCH

~r~ Thomas J. Buechler

vm

cc: '~r. Keith Boyd

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