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FEASIBILITYSTUDY ADDENDUM

SACO TANNERY WASTE PITS SITESACO, MAINE

EPA Work Assignment Number 03-1L26Contract Number 68-W8-0117

NUS Project Number 0215

June 1989

NUSCORPORATION

TABLE OF CONTENTS

Section Title Page No.

1.0 INTRODUCTION l-l

2.0 DETAILED ANALYSIS OF REMEDIAL ALTERNATIVE 2-1

2.1 Alternative SC-3A: Cover System with Monitoring Network and Institutional Controls 2-1

2.2 Alternative Assessment 2-17

3.0 SUMMARY OF OTHER REMEDIAL ALTERNATIVES 3-1

FIGURES

2-1 Waste Pit Cover System 2-9 2-2 Lagoon 1 Cover System 2-11 2-3 Lagoon 2 Cover System 2-12 2-4 Proposed Remediation/Construction Schedule 2-18

TABLES

2-1 Cost Estimate: Alternative SC-3A 2-25 2-2 Evaluation Criteria Summary Alternative SC-3A 2-30 2-3 Summary of Source Control Remedial 2-34

Alternative SC-3A

3-1 Remedial Alternatives Cost Comparison 3-2

1.0 INTRODUCTION

NUS Corporation was requested by the U.S. Environmental Protection Agency (EPA) Region I to prepare a Feasibility Study (FS) Addendum report which develops and presents a detailed analysis of an additional remedial alternative for the Saco Tannery Waste Pits (STWP) Superfund site in Saco, Maine. This FS Addendum supplements the Feasibility Study (FS) report prepared in July 1988, which discussed various remedial alternatives for the remediation of contaminated environmental media. The alternative developed in this report, Alternative SC-3A, is a modification of Alternative SC-3 (the cover system) presented in the July 1988 Feasibility Study. Alternative SC-3A incoporates legislative actions and the installation of an extensive monitoring network with a contingency for treatment should contaminants be detected to be leaching from the sludge. NUS performed all activities for the FS Addendum under Contract No. 68-W8-0117, Work Assignment No. 03-1L26.

This document consists of three major sections. Section 1.0 is the Introduction. Section 2.0 consists of the detailed analysis of Alternative SC-3A which includes the nine factors that address Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) concerns. Section 3.0 consists of the revised cost analyses (using 1989 present worth estimates) for all remedial alternatives.

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2.0 DETAILED ANALYSIS OF REMEDIAL ALTERNATIVE

This section presents the detailed analysis of Source Control (SC) remedial alternative SC-3A for the Feasibility Study (FS) Addendum. The analysis presents the relevant information that allows decision makers to select an appropriate site remedy. The detailed analysis of the remedial alternative includes the following:

o Detailed descriptions of the remedial alternative with emphasis on application of the various technologies as components in the alternative.

o Detailed analysis of the remedial alternative in relation to the nine evaluation criteria established to address CERCLA requirements (Section 121(b)).

Nine evaluation criteria have been developed to address the considerations listed above as well as technical and policy factors likely to be important for selecting remedial alternatives. The nine evaluation criteria encompass technical, cost, and institutional considerations; compliance with specific statutory requirements; and state and community acceptance. These evaluation criteria serve as the basis for conducting the detailed analysis during the Feasibility Study and FS Addendum for the selection of an appropriate remedial action. See Section 7.1 of the Feasibility Study report (Ebasco, July 1988) for a description and discussion of the nine evaluation criteria.

2.1 Alternative SC-3A: Cover System with Monitoring Network and Institutional Controls

Alternative SC-3A consists of covering the waste pits and lagoons with a cover system, utilization of an on-site monitoring network to detect any migration of contamination, the use of institutional controls to prevent disturbance of the soil cover systems, and the establishment of a compensatory wetland. Alternative SC-3A would address principal existing threats associated with ingestion or direct contact with contaminated sludge and sediments. These risks would be controlled and reduced by placing permeable cover soils over contaminated sludge and sediments in the pits, lagoons, seep area, and wet area near Waste Pit 9. Contaminated surface water in pits and lagoons would be pumped and trucked to an off-site treatment facility, assuming that only standing water is removed. Approximately 100,000 cy of sludge likely to fail TCLP or EP Toxicity tests for chromium would remain buried across the site. However, the monitoring network will serve to alert State and Federal agencies of any increases in contaminant migration that may increase risk to public health or the environment. A contingency for treatment of waste material will ensure future action should leaching of contaminants at levels which present a risk to human

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health or the environment occur. The designation of the site as a permanent conservation area will prevent any future use or disturbance of the soil cover systems.

Alternative SC-3A includes the following components:

o Legislation by State of Maine to designate the site as permanent conservation area.

o Wetlands assessment study.

o Mobilization of construction crews.

o Site preparation for remedial action activities.

o Removal and treatment of ponded water from waste pits and lagoons.

o Installation of geotextile fabric.

o Installation of bio-intrusion barriers (gravel and rock layers).

o Covering of waste pits and lagoons with a permeable cover system.

o Covering of wet area near Waste Pit 9 and seep sediments with the prescribed cover system.

o Re-establishment of vegetation at each waste pit and lagoon, the wet area near Waste Pit 9, and any additional disturbed areas.

o Post-closure maintenance on covered areas.

o Establishment of compensatory wetlands area on-site.

o Design and installation of the monitoring network.

o Periodic sampling of the monitoring network to evaluate contaminant migration.

o Five-year review of site status.

Each major component of this remedial alternative is described in further detail in subsequent paragraphs. The components (tasks) are discussed in the order they would be performed during remediation. The anticipated time to implement each component is also discussed. The alternative description concludes with a discussion of health and safety considerations for this alternative

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and an estimated total construction time.

Legislation by State of Maine

The Maine Legislature will designate the site as a conservation area. A mechanism would be established to allow for all remedial and monitoring activities associated with Alternative SC-3A, to prohibit the development of the land and use of groundwater, and to enforce these controls. In addition to the statute, deed restrictions would be required to assure that the institutional controls would be enforceable.

Wetlands Assessment Study

The values of wetlands may be assessed in terms of their various functions, which may vary substantially in importance and type depending on the characteristics of any particular wetland. These various functional attributes include:

o Hydrologic Functions. Based on flood storage, retardation, and desynchronization; groundwater recharge and discharge; and shoreline anchoring and dissipation of erosional forces.

o Water Quality Functions. Evaluated according to potential for sediment trapping; oxygen production; nutrient retention and removal; and contaminant retention and removal.

o Habitat Functions. Evaluated in terms of density and number of vegetation strata; amount of edge (transitional zone of vegetation); food availability and production; and diversity of vegetation.

o Ecosystem Functions. Based on estimates of primary productivity; decomposition; nutrient export; and nutrient transport.

o Socio-economic Functions. Evaluated in terms of aesthetics; recreational functions; educational resources; historic and scientific value.

The baseline evaluation of site wetlands (Wetlands and Floodplain Assessment, NUS, June 1989) and the Ecological Risk Assessment (Ebasco, July 1988) provide only about 25 percent of the necessary information to evaluate the functional attributes of the STWP wetlands. This information includes:

o Identification of plant species.

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o Identification of aquatic biota.

o Identification of terrestrial and avian biota.

In order to consider compensatory wetlands, further data is required for on-site wetlands in the form of the functional attributes listed above. Information from this assessment would be used to accurately assess current functional attributes and assure that compensatory wetlands would provide hydrological, biological, and cultural functions necessary for the STWP site.

Site Preparation.

A conceptual site layout for remediation is shown in Figure 7-1 of the Feasibility Study report (Ebasco, July 1988). For Alternative SC-3A, site preparation would consist of clearing and grubbing to prepare the site for access road improvements; access to waste pit and lagoon areas; soil stockpiling areas; equipment storage/parking areas; vehicle turnaround areas; and site fence-line areas.

Before remedial construction begins on-site, a fence would be installed around the perimeter of the 233-acre site. This chainlink fence, which would extend approximately 12,000 linear feet, would be 6-8 feet high with three-strand barbed wire extending along the top of the chainlink mesh. This type of fence would provide site security during remediation. Site access would be limited to a 20-foot gate and a smaller pedestrian gate adjacent to the large gate. Installation time for the entire fence is approximately 6 to 8 weeks, assuming one crew working 8 hours per day, 5 days a week.

Clearing and grubbing processes would be extensive because of the thickly wooded areas and large trees at the STWP site. Clearing and grubbing would involve cutting trees and brush, and uprooting stumps. It is assumed that brush and stumps would be chipped on-site; however, tree trunks would be hauled off-site as logs. For Alternative SC-3A, approximately 4 acres would require clearing and grubbing. The task would be expected to take approximately 10 to 12 weeks, assuming one crew working 8 hours per day, 5 days per week, or 5 weeks if two crews are used.

After clearing and grubbing, the existing access road (see Figure 7-1 of FS report) would be widened to 30 feet (two 12-foot travel lanes and two 3-foot shoulders) to accommodate two-way traffic. A 2-foot gravel road base would be constructed using a DOT-specified gravel material. This access road material would be necessary to provide adequate support for heavy truck loads and to accommodate anticipated traffic flow. Improvement of the main access road would require approximately 6 to 8 weeks.

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Five designated vehicle turnaround areas would be graded and bedded with 2 feet of road-base gravel. Turnaround areas would be needed to allow trucks to conveniently make U-turns near various waste pit areas when traveling to and from waste pits and lagoons. Turnaround areas would be approximately 50 feet in radius to accommodate the turning radii of larger trucks.

To improve vehicle access to each waste pit and lagoon, an area around the perimeter of the waste pits and lagoons would be cleared and grubbed of trees, brush, stumps, and rocks. Access improvements are necessary around pits to enable vehicles to adequately stockpile, move, and spread the cover soil. This clearing would occur during the initial "clearing and grubbing" stage of site preparation.

After clearing and grubbing, an area for storing cover soils would be graded and prepared (see Figure 7-1 of FS report). A 300 ft x 300 ft area would be large enough to store two 125-fcot-diameter piles, with each pile holding approximately 5,000 cy of soil, gravel or rock material. Initially, the two stockpiles will be used to store gravel and rock piles (for construction of the biological intrusion barriers). The bio-intrusion barriers are necessary to inhibit the impact of burrowing animals into the chrome contaminated waste and minimize the disturbance of the waste sludges. The rock and gravel stockpiles can be replenished on an as-needed basis. After the installation of the gravel and rock layers, the stockpile areas can be used to store additional soil cover materials. One pile would be dedicated for cover material (common till) and the other for vegetative cover material (loam) to be used as the final cover on the waste pits. The stockpile volumes would provide a few days buffer for filling and grading operations if delivery from off-site sources is interrupted.

The stockpile volume would also allow for the acceleration in work activities, if necessary. This area would be sufficiently large to allow truck movement around the rock or soil piles for unloading and loading. To expedite site remediation, the stockpile area would be prepared at the same time the access road is being improved. Reliable material availability and well-planned delivery schedules would be necessary to maintain these piles at full capacity. As illustrated in Figure 7-1 of the FS report (Ebasco, July 1988), an area cleared for storage and parking would be graded and bedded with gravel. This 100 ft x 300 ft area would accommodate heavy equipment used during remediation. This area would also be prepared at the same time the access road is improved.

Required utilities for this alternative include electricity and telephone, which are already connected to the site. Utility cables

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enter near the site access off Flag Pond Road and extend approximately 200 feet to the cleared area where site trailers would be located during remedial activities. Electrical hook-up at the trailer site would only take a few days after site operations trailers have been delivered.

Three site trailers would be located near the site access point (see Figure 7-1 of FS report). One trailer would be dedicated for site engineers, another for construction contractors, and a third for equipment storage. An area for these trailers is presently cleared and graded because these locations were used to house trailers during Phase II RI field activities.

Site preparation work would be accomplished prior to covering waste material in waste pits/lagoons and would require approximately 12 to 16 weeks to complete. This time duration assumes that several site preparation tasks would be performed concurrently during May (after "mud" season) through November.

Removal and Treatment of Ponded Water.

Prior to placing cover material on each waste pit and lagoon, ponded water would be pumped from each pit and lagoon and transported off-site for disposal. This procedure would occur on a pit-by-pit basis. A pump truck would drive to each waste pit or lagoon and pump the ponded water from the surface. After pumping, the water would be transported to an off-site commercial water treatment facility (e.g., the CECOS facility in New Britain, Connecticut).

Alternatively, a local publicly owned treatment works (POTW) may be contracted to treat the pumped water. The ponded water trucked to a local POTW would be more economical provided that available capacity is identified. The City of Saco operates a wastewater treatment facility. The plant is a conventional activated sludge system with one primary clarifier, four mechanical aeration tanks, and three secondary clarifiers. A capacity upgrade to 4.2 million gallons per day (MGD) at this facility was completed during the fall of 1988. The plant is currently receiving approximately 2 MGD average flow. Sludge from the plant is taken to the Old Orchard Treatment Plant where it is composted (mixed with wood chips) and utilized by the municipality. The Saco POTW has an industrial pretreatment program; the only permitted user to date is Saco Defense, Inc. The proximity of this plant to the site and may provide significant cost savings over water treatment at a commercial treatment facility. The cost for the treatment of removed ponded water is based on the use of the Saco POTW. Otherwise, disposal costs may be significantly higher.

Additionally, the wastewater treatment facility system would be

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compatible with the type and concentration of contaminants found in the ponded water. Most of the inorganic constituents in the water would partition to sludge produced in the activated sludge treatment process. Chlorobenzene would be volatilized and potentially biodegraded during treatment. The flow rate of the Saco treatment plant and the anticipated loading of ponded water indicate that the water would not be likely to have an effect on treatment operations.

The amount of standing water to be pumped from the waste pits and lagoons is highly dependent on the amount of precipitation occurring during the time of the year the site is remediated. Visual observations were used to estimate the volume of water contained in waste pits and lagoons. Section 3.4.3 of the FS report (Ebasco, June 1988) discusses assumptions used to calculate the quantity of contaminated ponded water on-site. Quantities are expected to range between 0.5 MG and 2.8 MG depending on the season of the year. This is based on the assumption that groundwater inflow will not prevent the removal of ponded water.

As discussed below, the pits may be re-pumped after the installation of the geotextile and the rock and gravel layers because of consolidation of the waste sludges.

Installation of the Bio-intrusion Barriers.

A geotextile fabric will be installed over the sludge materials prior to the placement of the cover system. Based on the review of sludge characteristics (as presented in Section 7.0 of the FS report), it was determined that either a spunbonded or a non-woven needle-punched geotextile fabric will be used to cover waste sludges in pits and provide for a stable surface for the placement of the rock, gravel and soil layers. The geotextiles are semi-porous and allow the passage of precipitation and prevent any ponding of liquids. The geotextile will also minimize settlement of the rock and gravel layers into the sludge. The fabric serves to demarcate the contaminated sludge from the clean cover materials should future excavation be required.

A one-foot thick rock and a 6-8 inch thick gravel layer will be installed to inhibit the disturbance of the waste sludges. Generally for the pits which have materials situated above the water table, the installation of a bio-intrusion barrier will be necessary to deter the action of burrowing animals. The barrier will also be installed in pits below the water table to prevent burrowing animals from disturbing the sludge materials since seasonal variations may lower the water table. Based on studies sponsored by the Department of Energy, barriers of this nature have proven effective in the reduction of penetration of waste piles by burrowing animals and vegetative root growth (Hakonson et al,

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1982). Similarly, this method may be applied at the STWP site to deter the intrusion of burrowing animals in the sludge. Rock sizes of 5" or greater will be used since the burrowing animals are not likely to move objects greater than themselves. The gravel will help minimize the infiltration of the till layers into the void spaces in the rock layer.

It is estimated that approximately 3 - 4 weeks will be required for the installation of the geotextiles, 16 weeks for the installation of the rock and gravel layers, and an allowance of 2 -3 weeks for the initial consolidation of waste sludges. This estimate is based on the use of a 6-men crew for installing and stitching the seams (or overlapping).

Covering Waste Pits and Lagoons.

The cover system for each pit would consist of 2 feet of till (a mixture of sand, gravel, and silt) material and 18 inches of vegetative loam material placed over a bio-intrusion barrier. Figure 2-1 illustrates a cover system cross-section of a typical waste pit. To build a cover that will promote runoff, maintain grade, establish good vegetative growth, and reduce potential for waste contact, a 5-foot soil thickness (roughly 0.5 ft greater than SC-3 design, as discussed in the FS report, to accommodate the gravel layer) would be necessary. The 2-foot till layer would most likely consist of a variety of silts, sands, and some clays. The amount of fines (ASTM D 422 Specification for sieve analysis) would be approximately 20 to 50 percent. This soil composition would enable the material to hold some moisture and help enhance growth in the overlying vegetative loam material. The till material would also minimize the potential for erosion. The vegetative loam cover (18 inches) would allow for re-establishment of typical vegetation found in a wooded environment like the STWP site. Standard unscreened loam would be used for the top layer in the cover system. Both till and loam would be supplied from a local off-site source; no on-site material would be used for the cover system. Prior to placement of cover material, large vegetative growth (e.g. trees, brush) would be removed from inner-pit areas. This clearing would occur during site preparation work. It is expected that some discrete settlement in the pits and lagoons will occur due to the consolidation of the cover material and compression of the waste sludge. Additional soil cover materials will be added to insure a proper slope of the cover.

Cover material would be trucked from the on-site stockpile area to each waste pit. Thereafter, the cover would be spread, compacted and graded using conventional construction equipment (e.g., a tracked bulldozer). To promote runoff at each waste pit location, the cover would be sloped between 3 to 5 percent. If existing pit berms would be expected to exceed the anticipated elevation of the

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final cover, berms would be cut by bulldozer or backhoe and the benn material would be pushed into the waste pit before the geotextile and cover materials are applied. This procedure would be conducted to bury any waste material contained in pit berms.

Approximately 24,000 cy of till and 17,000 cy of vegetative loam material would be needed to cover all 53 pits. Approximately one extra foot of till for each waste pit would be supplied to fill existing low spots and holes, and replace subsided areas from the consolidation of the sludge, before placing the final cover system. This quantity is estimated to be 12,000 cy of material.

From an operations standpoint, it is assumed that the waste pits can be covered within 28 weeks at a rate of approximately two pits per week. This schedule assumes that three crews will work simultaneously. Each crew would consist of one truck, one backhoe, and one front-end loader for equipment with three operators, two laborers, and one foreman. Chromium Lagoons 1 and 2 would be covered using these same procedures. Because the lagoons are significantly larger and deeper than pits, more cover material will be necessary to fill and cover these areas. The cover system for both lagoons, as illustrated in Figures 2-2 and 2-3, would consist of approximately 5 feet of till (about 40,000 cy) underlying 1.5 feet of vegetative loam (about 12,000 cy) and over the bio-intrusion barrier and the geotextile. An extra foot of till would be supplied to fill low spots and holes (8,000 cy). Cover material would be graded and sloped (i.e., greater than or equal to 3 percent) to promote runoff. As with the pits, existing berms would be cut if their present elevations exceed the anticipated final cover system elevation.

The solid waste area located in the southwestern corner of Chromium Lagoon 2 would be covered with 2 feet of till material (approximately 3,000 cy) and 1.5 feet of loam ( overlying the rock and gravel, and geotextile). Existing berms around the solid waste fill area would not be moved or cut. The solid waste area would also be graded and sloped (see Figure 2-3).

Four crews, each consisting of a truck, backhoe, and bulldozer, would be used to cover the lagoons. Dump trucks would transport cover material from the stockpile area to the lagoons. Chromium Lagoons 1 and 2 would be covered concurrently with the waste pit covering. It is estimated that lagoon-covering would take approximately 21 weeks.

Covering Wet Area and Seep Sediments.

A 28,500-square-foot wet area near Waste Pit 9 contains contaminated sediments. To protect public health and the environment from potential exposure, this area would also be

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covered with soil materials, and the rock and gravel layers. After access improvements and installation of the bio-intrusion barrier, the wet area would be covered with 2 feet of till, (approximately 2,200 cy) and 1.5 feet of vegetative loam (approximately 1,730 cy) . As with the pits, portions of the cover may be expected to settle and consolidate. An extra foot of till (1,200 cy) would also be supplied to fill holes and low spots formed by settlement. Grading and sloping procedure would be similar to the pit covering process. Cover soils in this area would be placed during pit covering, and the estimated time for covering the wet area would be 5 weeks.

Finally, the seep area along the outer perimeter of Chromium Lagoon 2 (near the western berm) would be covered. This area consists of surface leachate believed to be seeping from Chromium Lagoon 2. The 7,000-square-foot seep area would be covered with 1 foot of rock, 6-8 inches of gravel, 2 feet of till and 1.5 feet of vegetative loam, and then graded and sloped to promote runoff.

Design and Installation of Monitoring Network.

The installation of additional monitoring wells is recommended, primarily to serve as a warning system to detect the potential mobilization of site contaminants in groundwater downgradient of the covered lagoons and waste pits. A preliminary monitoring network is summarized below; however, prior to finalizing the number and locations of additional wells, it is recommended that a minimum of one to two sampling rounds be conducted from existing wells. The existing database should be expanded and evaluated prior to locating additional monitoring wells.

Up to twelve additional, double-nested well locations may be required (24 wells) in order to provide an adequate groundwater monitoring network. Based on overburden and shallow bedrock groundwater contour maps and bedrock surface contour maps, additional wells would be located downgradient of waste pits, chromium lagoons, and wells in which contaminants have been previously detected. Previously collected data indicates two bedrock troughs in the area. It is suggested that two to three bedrock wells be screened in the troughs to detect potential contaminant migration along the troughs. (Previously estimated seepage rates in the shallow bedrock are on the average of 35 feet per year.) Since significant contamination has not been detected in the three deep bedrock wells onsite, additional nested monitoring wells would be screened at each location with one well in overburden and one in shallow bedrock. Double-nested wells are also recommended in order to provide vertical gradient information.

Based on existing geologic cross-sections and bedrock contour maps, estimated total footage to be drilled during the monitoring network

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installation is approximately 300 to 450 feet of overburden and approximately 300 to 450 feet of bedrock coring; however, following additional sampling of existing wells and prior to finalizing specific well locations, these estimates should be revised. A careful review of existing depth-to-bedrock data should be conducted prior to finalizing well locations, since bedrock appears to be very shallow to the northwest of the site.

The recommended groundwater monitoring program would include sampling of all newly-installed wells, as well as sampling of previously-installed downgradient wells, including some or all of the following: MW-1; MW-101; MW-3; MW-103; MW-113 A,B; MW-4 A,B,C; MW-112 A,B; MW-7 A,B,C; MW-107; and MW-111 A,B. Initially, groundwater samples would be analyzed for volatile and semi-volatile organic compounds and chromium, arsenic, lead, and antimony (previously detected in groundwater at the site). Sampling will be conducted on a quarterly basis for the first two years, and semi-annually thereafter. Specific parameters, frequency of sampling, and sampling locations would be periodically evaluated (during 5 year reviews) and modified according to sampling and analytical results and observed trends.

Re-establishment of Vegetation at Covered and Disturbed Areas.

A variety of seeding or planting procedures may be used to re-establish vegetation at covered and disturbed areas after remedial activities are complete. Vegetative loam cover soils would support several types of vegetation. Presently, wetlands and upland areas at the site provide habitats that can support diverse wildlife populations. Given the size of the site and its heavily forested nature, it is likely that much of the site will revegetate itself over a period of several years after remediation. A meadow grass such as crown vetch or reed canary grass may be applied to begin the revegetation process. However, it is expected that seeds and nuts from present on-site plant species will gradually re-establish natural vegetation in covered areas. In addition to covered areas, stockpiling areas, equipment storage areas, and vehicle turnaround areas would be revegetated following remediation to prevent further erosion and restore natural habitats.

Post-closure Maintenance.

Post-closure maintenance (operation & maintenance) would be necessary to visually inspect remediated areas and, if necessary, perform additional work or repairs on covered areas. Initially, post-closure maintenance inspections would occur twice a year. Maintenance activities may be required if cover soils have been disturbed by burrowing animals or "off-road" vehicles driven over

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the site. With the addition of the cover over the waste sludge, consolidation and settlement can be expected resulting in the disturbance of continuous slope required for proper surface drainage. Additional cover soils may be applied and graded during post-closure maintenance. Repairs may also be necessary to support erosion control or to revegetate base areas.

Establishment of Compensatory Wetland.

For regulatory purposes, federal agencies define wetlands as "those areas that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs, and similar areas" [40 CFR Section 230.3(t)]. Wetlands provide many valuable functions such as fish and wildlife habitat, groundwater discharge and recharge, and flood storage. Because wetlands provide a wide range of hydrological, biological, and cultural functions, remediation of these areas requires careful analysis of baseline conditions and the functional attributes of on-site wetlands.

In order to re-create wetlands of equal or higher value at the STWP site, the functional attributes of the wetlands presently on-site must be evaluated. In this manner, re-constructed wetlands would serve the necessary functions at the STWP site.

Waste pits and lagoons at the site currently contain elevated levels of chromium and other environmental contaminants that are potentially harmful to aquatic and terrestrial biota. Potentially, a minimum of 5.85 acres of wetlands may be lost as a result of source control remedial activities at the STWP site. Wetland areas may vary in size from season to season and this area would need to be better quantified prior to remedial work. Additional areas may also be lost during site preparation work or during clearing for pit/lagoon access. Unavoidable impacts would be mitigated to the maximum extent possible using silt curtains, hay bales, and check dams.

Wetland areas at the STWP site serve as an important food and habitat resource for indigenous wildlife. Upon preliminary review, it appears that the ratio of cover to water for existing wetlands is 8:1 (cover:water). However, the best habitat for waterfowl and other indigenous wildlife requires a cover to water ratio of 1:1.

At the completion of remedial activities, wetland areas would be re-established with a 1:1 cover to water ratio. The locations for wetlands reconstruction would vary depending on the implemented remedial action. For Alternative SC-3A, present wetland areas

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would be covered. Thus, for this alternative, compensatory wetland areas would likely be established in the central portion of the site between the two branches of the access road.

For conceptual design purposes, reconstruction of approximately 6 acres of wetlands would be performed at the STWP in conjunction with site remediation. Yearly operation and maintenance would also be necessary for several years after construction of wetland areas. The scope of maintenance activities is difficult to predict and generally depends on plant community success in the new wetlands.

A more detailed discussion of site wetlands and the impact of remedial activities on those wetlands is contained in the Wetlands and Floodplain Assessment Report (NUS, 1989). Although the report does not specifically address alternative SC-3A, the impacts associated with the cover system in SC-3 (as discussed in the Wetlands and Floodplain Assessment Report) would be identical.

Health and Safety Considerations.

OSHA requirements (29 CFR 1910.120) require workers performing investigatory or remedial work at a hazardous waste site to be certified in a health and safety monitoring/training program. The following levels of health and safety protection would be anticipated for each of the major tasks for Alternative SC-3A:

o Site preparation - Level D o Dewatering waste pits and lagoons - Level D o Installation of geotextiles and bio-intrusion barriers ­

Level D o Covering waste pits and lagoons and additional areas ­

Level D o Post-closure maintenance of covered areas - Level D

Alternative SC-3A requires minimal invasive activity and respiratory protection would probably not be required because sludge excavation would not be performed. However, workers should be prepared to upgrade personal protection to Levels C and B during remediation. Final health and safety requirements would be established during remedial design.

Estimated Construction Time.

Remedial design activities for this alternative would be relatively basic. A period of 9 to 12 months would be anticipated between the start of the remedial design task and approval of the 100-percent design.

For Alternative SC-3A, site preparation is estimated to take 16 to

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20 weeks, the installation of the geotextile, and the rock and gravel layers may require up to 22 weeks, and the covering of waste pits and lagoons is estimated to be completed in a 27- to 30-week period. It is expected that various activities can occur concurrently, thus reducing the total duration of the remediation. With this schedule, seven trucks would be required to haul fill or loam continuously until covering operations are completed. There would be an opportunity to start covering pits before all preparation is finished. However, potential exists for adverse weather during earthwork construction (e.g., low temperatures, rainstorms, and mud season) . The active construction time for this alternative may be 18 months, but would probably occur over an 20-month period. Figure 2-4 provides a potential construction schedule for this alternative.

2.2 ALTERNATIVE ASSESSMENT

Short-term Effectiveness.

Both pumping ponded water from pits and covering pits, lagoons, and contaminated sediments pose minimal risk to the community and will eliminate the risk of direct contact. Neither of these actions involve invasive activity that would expose significant quantities of waste and potentially cause air quality impacts. The installation of the bio-intrusion barriers will inhibit the activities of burrowing animals and minimize the disturbance of the waste sludges. Similarly, these activities would not pose significant risks to workers during remedial actions. Workers may expose some sludge during site preparation work or pit covering work (i.e., uprooting trees may unearth some sludge), but these risks can be controlled by providing personal protection to minimize dermal contact. General health and safety practices can effectively and reliably address threats posed to workers.

Some precipitation is likely to permeate the soil cover system and percolate to the sludge layer or mix with groundwater. The monitoring network will serve to identify any potential migration that may occur. The type of rock material used in the bio­intrusion barrier must be non-acid producing (eg. limestone) in order to minimize the risk that metals will leach from the waste sludge.

The dewatering and covering of waste pits and lagoons would destroy habitats and resources for aquatic biota. However, because a compensatory wetland area would be created on-site, adverse environmental impacts would be minimized. With time, a properly designed wetland could reliably provide equal or greater

2 - 1 7

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functional value than the current wetland areas. Potential environmental impacts would be limited to the time between dewatering operations and establishment of a functional wetland.

Remedial action objectives related to ponded surface water would be achieved as water is pumped from each waste pit and lagoon. Remedial action objectives related to human health protection from sludge in waste pits and lagoons, the solid waste area, and wet area/seep sediments would be achieved in about a year and a half. Remedial action objectives established to prevent future groundwater contamination by chromium leaching or to reduce the threat of future leaching are addressed by the establishment of an extensive monitoring network to detect any migration and a requirement for treatment of the wastes in the event contaminants leach at significant concentrations.

Long-term Effectiveness and Permanence.

Under Alternative SC-3A, environmental risks associated with contaminated ponded water would be minimized because water would be removed from waste pits and lagoons and treated off-site. Approximately 100,000 cy of sludge, solid waste, and contaminated sediments would remain untreated at the site after covering operations are complete. Constituents in these media, while not presently mobile, have the potential to leach to groundwater under future conditions (i.e., extreme decrease of pH of rainwater). The use of non-acid rocks and gravel (eg. limestone) may reduce this potential. Direct contact/ ingestion risks under the Phase I Baseline Risk Characterization (see Table l-l of the FS report) would be reduced.

Covering the contaminated media on-site is likely to effectively address potential contact risks in the short-term. To effectively prevent the exposure of the wastes, legislation to designate the site as a permanent conservation area would be required. Long-term management to maintain cover soils would be necessary, and some cover material may need to be replaced periodically due to erosion. Site inspections would be conducted twice annually; these inspections would establish operations and maintenance (O&M) schedules for improving cover integrity where necessary. Long-term site-wide groundwater monitoring would be conducted to evaluate future contaminant leaching from sludge to groundwater. No other major O&M functions would be required. The primary uncertainty associated with monitoring is the appropriate duration and frequency. This would be established through re-evaluation of sampling results.

Future contaminant leachability is the major uncertainty associated with leaving wastes untreated at the STWP site.

2 - 1 9

Groundwater monitoring would effectively and reliably assess future leaching. However, as long as wastes remain untreated, site-wide groundwater monitoring would be necessary indefinitely. If constituents in sludge and sediment become mobile in the future, a range of treatment alternatives would be evaluated and a treatment alternative selected and implemented.

Reduction of Mobility, Toxicit,

Principal threats in ponded surface water would be addressed by pumping and off -site treatment. Availability of a local POTW or off-site water treatment facility would be required for treating the pumped water. Covering contaminated sludge and sediments would not constitute a treatment process, but would address threats associated with direct contact and ingest ion. Under this alternative, 0.5 to 2.8 MG of contaminated ponded water would be treated off -site. Pumping and treating this water reduces its on-site volume and toxicity to aquatic organisms.

The estimated 100,000 cy of sludge and contaminated sediments at the STWP site would remain untreated, and no reduction in mobility, toxicity, or volume would be achieved. Chemical constituents in the untreated media would continue to pose a future risk to groundwater through leaching, although neither chromium nor other constituents (i.e., VOCs and SVOCs) in sludge are currently being mobilized. However, if constituents in the sludge and sediment become mobile in the future, a range of treatment alternatives would be evaluated and a treatment alternative selected and implemented.

Imp1 ement abi1i ty«

The implementability evaluation is separated into these categories: site preparation; dewatering pits and lagoons; covering pits and lagoons; installation of monitoring network, and operation and maintenance. This approach succeeds in identifying specific implementability concerns with major site activities throughout the remediation process. It should be noted that this remedial alternative is only implementable if legislation to designate the site as a conservation area which prohibits the development of the land or use of groundwater is established.

o Site Preparation

For site preparation work (i.e., clearing/grubbing, fencing, constructing access roads), no major construction concerns are evident. Although clearing and grubbing heavily wooded areas would be labor-intensive, no unique capabilities or contracting specialists would be required to perform or provide this service.

2 - 2 0

Site preparation activities would be more difficult to implement during winter or early spring months due to adverse weather conditions. Schedule delays may occur if site activities are performed during these months. Site work may be limited to the months where snowfall and accumulation is not anticipated.

The gravel base of the main access road through the site may need periodic reconstruction. This reconstruction, which would basically consist of adding more gravel, would not be difficult to implement and would not be expected to delay the remediation process.

Services required to perform site preparation work are readily available and widely practiced. Necessary equipment and materials used to perform site preparation work (e.g., roadbed soils, clearing equipment) are available in Maine. Contractors who perform site preparation work would be required to demonstrate health and safety training certification for laborers on-site. Many remedial construction contractors employ personnel who have the required health and safety training. However, health and safety requirements would impact remedial costs. Because several firms have familiarity with this type of site preparation work, it is anticipated that several companies would provide a competitive bid.

o Dewaterinc? Pits and Lagoons

Pumping ponded water is a well-established process and would be easy to implement. This process is reliable and has been well-demonstrated. Where possible, pumping would be performed during late spring or early summer months, when there would be no ice in the waste pits and lagoons. However, water quantities would be greater in these months. Schedule constraints may occur because pumping would occur just prior to installation of the geotextile and the rock and gravel layers at each waste pit and lagoon; otherwise, rainfall would fill the pits and necessitate a second pumping. Pumping rates are estimated at about 5,000 gallons per hour. Several local companies can provide these services and would be contracted on a long-term basis, because the necessity and timing of pumping is dependent on rainfall amounts and day-to-day remediation schedules.

Liquid-transport equipment would be readily available, as long as the anticipated disposal rates are known and selected trucking companies are informed of the quantities and types of liquid to be hauled. Many companies use pumping/vacuum units to extract water from waste pits and lagoons. It is anticipated that more than one vendor will be available to provide a competitive bid for pumping and hauling services.

2 - 2 1

Water treatment technologies at off-site facilities have been proven to treat surface water from the STWP site. The reliability of a typical wastewater treatment plant has been demonstrated for many years, and performance goals would be achieved. Coordination between agencies would be necessary to obtain required permits for off-site water treatment. Approvals have been obtained for treating contaminated liquids from Superfund sites at POTWs. Leachate from the Hyde Park Landfill and Love Canal Landfill is presently treated at local POTWs. Contaminated groundwater from the Stringfellow Acid Pits site in California is treated at a POTW, and groundwater from the Western Processing site was sent to a POTW beginning in August 1988. It is anticipated that the required approvals for using the Saco POTW for treating the ponded water would be received given the expected flow rate, anticipated low constituent concentrations, and precedent for using POTWs to treat liquids at other sites.

Several local POTWs have the technology and treatment equipment to accept the type of contaminated water present in the ponded waste pits and lagoons. These plants utilize activated sludge processes, which tend to partition chromium, lead, and other inorganic constituents in sludge ("Fate of Priority Pollutants in Publicly Owned Treatment Works," USEPA, 1982). As mentioned previously, the City of Saco POTW has recently been expanded; the additional capacity is likely to be sufficient to receive water from the site on a periodic basis. Alternatively, more than one plant may be selected for water treatment to reduce the amount of water shipped to one plant.

While ponded water can be treated at a local POTW from a technical perspective, regulatory or political implications may impact the feasibility of this procedure. In this case, an off-site treatment, storage, and disposal (TSD) facility such as the CECOS plant in Connecticut may be contracted to receive and treat the water. However, treatment at a TSD facility several hundred miles from the site will increase costs significantly.

o Covering of Waste Pits and Laaoons

Covering waste material presently buried in waste pits and lagoons is technically feasible. Construction of cover systems has been well-demonstrated and would be technically reliable. It is anticipated a geotextile placed over the sludge would help to support the bio-intrusion barrier and several feet of cover soils. Covering operations would be implemented using standard construction procedures. The placement of the geotextile requires some specialized equipment, but these are readily available to many construction firms. The joining of the geotextile seams is a standardized practice and may be readily implemented. After the placement of the rock and gravel and layers over the geotextile,

2 - 2 2

it may be necessary to allow for time for the consolidation of the sludge due to the bearing pressure exerted by the surcharge. Geotechnical test data of sludge samples presented in the FS report (Ebasco, July 1988) suggest that the sludge has a high moisture content, and is compressible. Equipment and personnel used for the installing the geotextile must be prepared for potential muck-like surface conditions. It is recommended that cover construction be performed during warmer months to reduce potential adverse effects that cold or wet weather might have on the integrity of cover construction and project schedule.

If necessary/ future remedial action could be readily implemented since the soil cover and the gravel and rock layers are physically separated from the wastes by the geotextile. Excavation, waste consolidation or treatment can be performed if the need arose. Groundwater monitoring across the site would be performed to detect contaminant leaching. Periodic replacement of cover material may be necessary, particularly if waste becomes exposed by uprooting trees, burrowing animals, erosion of cover soils, or soil disturbances from digging or off-road vehicle usage.

Equipment and experienced personnel are available to perform the covering work. As mentioned previously, the covering process is well-demonstrated and many construction contractors can perform this task. Many construction and remediation contractors satisfy health and safety training requirements. It is anticipated that several vendors would submit competitive bids for this task.

o Installation of Monitoring Network

A long-term groundwater monitoring program will be established to identify the presence of contaminant migration. The existing on-site monitoring wells will be supplemented by additional nested wells to form the monitoring network. The design and installation of the monitoring wells have been performed at numerous hazardous waste sites throughout the country. Many drilling companies are available in the Northeast who have the experience, the equipment, and personnel to perform the required tasks. Many drilling companies have field crews who meet the 40-hour training and the medical monitoring requirements. Some companies also have had extensive experience at Superfund sites and can readily conduct the field activities.

o Post-Closure Maintenance (Operation and Maintenance)

The operation and maintenance (O & M) of the site after remediation can be performed by the appropriate agency without difficulty. The operation includes the periodic examination of the cover system integrity, evaluation of compensatory wetland functional restoration, and identification of any maintenance requirements.

2 - 2 3

These functions can be performed by personnel with some training. Within the first or second year after the placement of the cover, the soils and sludge can be expected to consolidate and settle heterogeneously. This will result in the formation of depressions in the cover or in the loss of proper slope of the cover. Additional cover materials, regrading and reseeding of the cover should be performed to ensure the proper drainage from the covers. Disturbance by animals or human activity of the covers will also require repairs to prevent any potential contact with the waste sludge. These repair and maintenance functions can be readily performed by a number of landscaping contractors.

Cost.

Table 2-1 presents capital and O&M costs for Alternative SC-3A. The net present worth for Alternative SC-3A is estimated at $9,211,600 - $10,551,400, depending on the groundwater monitoring network implemented. Capital costs total between $6,661,600 and $6,792,600, including direct and indirect capital expenditures. Post-closure annual costs over thirty years are estimated to be between $2,488,500 - $3,962,300 (present worth basis) based on the groundwater monitoring option selected.

ARARs Compliance.

Table 9-2 of the Feasibility Study highlights the potential Applicable or Relevant and Appropriate Requirements (ARARs) for all remedial alternatives. In this section of the F.S. Addendum, requirements specific to Alternative SC-3A will be discussed.

Federal OSHA requirements including the General Industry Standards and the Health and Safety Standards are applicable for all remedial activities conducted at the site would have to be followed during site work. The use of qualified contractors and adherence to site specific work plans should result in the protection of the workers and compliance with these regulations.

ARARs associated with pumping the ponded water in the waste pits and discharging to an off-site treatment facility include the Clean Water Act Pretreatment Standards (40 CFR 403) and the DOT Transport

2 - 2 4

TABLE 2-1 COST ESTIMATE: ALTERNATIVE SC-3A

COVER SYSTEM WITH INSTITUTIONAL CONTROLS SACO TANNERY WASTE PITS SITE

SACO, MAINE

OPTION 1: EIGHT ADDITIONAL MONITORING WELLS

ACTIVITY

CAPITAL COSTS

A INITIATE LEGISLATION FOR CONSERVATION AREA DESIGNATION

B SITE PREPARATION (INCLUDING SITE FENCE)

C REMOVAL AND OFF-SITE TREATMENT OF PONDED WATER

D INSTALLATION OF GEOTEXTILE

E INSTALLATION OF ROCK & GRAVEL FOR BIO-BARRIER

F COVERING PITS, CHROMIUM LAGOONS 1 AND 2, AND WET AREA NEAR WASTE PIT 9

G INSTALL MONITORING WELLS

H REVEGETATE ALL COVERED AREAS AND ADDITIONAL DISTURBED AREAS

I WETLANDS RESTORATION

SUBTOTAL OF ITEMS A

J HEALTH & SAFETY (@ 10%) LEVEL D PROTECTION

K LEGAL, ADMINISTRATION, PERMITTING (@ 5%)

L ENGINEERING (@ 10%)

COST TOTALS

$479,000

$363,000

$123,700

$569,300

$1,440,800

$46,000

$26,500

$1,222,000

­ I

$427,000

$213,500

$427,000

$4,270,300

TABLE 2-1 (Continued) COST ESTIMATE: ALTERNATIVE SC-3A

COVER SYSTEM WITH INSTITUTIONAL CONTROLS SACO TANNERY WASTE PITS SITE

SACO, MAINE

OPTION 1 (Continued)

ACTIVITY COST TOTALS

M SERVICES DURING CONSTRUCTION (@ 5%)

SUBTOTAL OF ITEMS J ­ M

SUBTOTAL

$213,500

$1,281,000

$5,551,300

CONTINGENCY (@ 20% ) $1,110,300

TOTAL CAPITAL $6,661,600

II ANNUAL OPERATING COST (2-YEAR PERIOD DURING REMEDIAL ACTION)

A SECURITY $5,100/YR

PRESENT WORTH OF ANNUAL OPERATING COSTS $9,500

POST-CLOSURE ANNUAL COSTS

A ANNUAL INSPECTIONS (30 YEARS)

B MISCELLANEOUS LAND SURFACE CARE (30 YEARS)

C. SAMPLINGS ANALYSIS (QUARTERLY, YEARS 0-2)(SEMI-ANNUALLY, YEARS 2-30)

PRESENT WORTH OF POST-CLOSURE ANNUAL COST

$7,600/YR

$1,000/YR

$266,800/YR $133,400/YR

$2,483,500

IV FIVE-YEAR REVIEW (FOR 30 YEARS)

PRESENT WORTH OF FIVE-YEAR REVIEW

NET PRESENT WORTH OF ALTERNATIVE (OPTION 1)

$20,400/REVIEW

$57,000

$9,211,600

TABLE 2-1 (Continued) COST ESTIMATE: ALTERNATIVE SC-3A

COVER SYSTEM WITH INSTITUTIONAL CONTROLS SACO TANNERY WASTE PITS SITE

SACO, MAINE

OPTION 2: SIXTEEN ADDITIONAL MONITORING WELLS (REFER TO OPTION 1 FOR BREAKDOWN OF ACTIVITIES)

ACTIVITY TOTALS

TOTAL CAPITAL COSTS $6,725,600

ANNUAL OPERATING COSTS (PRESENT WORTH) $9,500

POST-CLOSURE ANNUAL COSTS (PRESENT WORTH) $3,154,700

IV FIVE-YEAR REVIEW COSTS (PRESENT WORTH) $57,000

NET PRESENT WORTH OF ALTERNATIVE (OPTION 2) $9.946,800

OPTION 3: TWENTY-FOUR ADDITIONAL MONITORING WELLS (REFER TO OPTION 1 FOR BREAKDOWN OF ACTIVITIES)

ACTIVITY TOTALS

I TOTAL CAPITAL COSTS $6,792,600

II. ANNUAL OPERATING COSTS (PRESENT WORTH) $9,500

III. POST-CLOSURE ANNUAL COSTS (PRESENT WORTH) $3,692,300

IV. FIVE-YEAR REVIEW COSTS (PRESENT WORTH) $57,000

NET PRESENT WORTH OF ALTERNATIVE (OPTION 3) $10.551.400

NOTE: DISCOUNT RATE = 5%

Rules (49 CFR 107, 171.1 - 172.558). These requirements would be followed in removing the ponded water from the site.

Federal wetlands protection regulations apply to this alternative. The CWA (Section 404), which governs work in the area of wetlands, would be applicable. In addition, the Fish and Wildlife Coordination Act regulates activity in the vicinity of wetlands, as well as the Maine Freshwater Wetlands Act and the Federal Wetlands Executive Order. The Wetlands Executive Order requirements would be addressed by constructing compensatory wetlands on-site.

The Floodplain Executive Order and the RCRA Location Standards are ARARs. As set forth in the Wetlands and Floodplains Assessment report, this alternative will have a minimal impact on the floodplains because the disposal pits and lagoons do not lie within the floodplain area and because careful construction practices would be used during construction to minimize any potential adverse impact on the floodplains. This alternative would therefore comply with federal requirements.

Alternative SC-3A will attain all RCRA requirements. These requirements include the General Facility Standards, standards for preparedness and emergencies, and general operating requirements. As described in the FS report (Ebasco, July 1988), This alternative would meet the requirements that the final cover (1) functions with minimum maintenance; (2) promotes drainage and minimizes erosion or abrasion of the final cover; and (3) accommodates settling and subsistence so that the integrity of the cover is maintained. Requirements related to long-term minimization of migration of liquids and permeability would not be appropriate for this site for two reasons. First, because most of the disposal pits and lagoons are located within a high water table area, impermeable covers would not provide a successful means of preventing liquids from percolating through the wastes. Second, because chromium is not migrating from the wastes into the groundwater under current conditions, and only low level of organic contamination have been found in the groundwater indicating limited movement of the waste material from the waste pits and chromium lagoons, impermeable covers are not needed or appropriate under this alternative. To address concerns that chromium might begin to leach into the groundwater in the future, long term monitoring of the groundwater would be performed, with a contingency for treatment in the event that significant levels of contaminant migration are detected.

overall Protection of Human Health and the Environment.

This alternative would reduce risk to public health from direct contact with contaminated soil and sediment under the Baseline

2 - 2 7

Exposure scenario. The risk to public health would be eliminated under the Future Residential Use Exposure scenario since future excavation of contaminated soil will be precluded through legislation restricting land use at the site. Potential cancer risks (identified in the Supplemental Risk Assessment) due to dermal absorption and ingestion of excavated soil and sediment contaminated with arsenic would be reduced. Likewise, potential non-carcinogenic risks from sludge and sediment having a Hazard Index greater than 1.0 would be reduced under the Future Residential Use scenario.

The monitoring program and "trigger" for additional remedial measures would detect any future releases of contaminants from sludge that could result in groundwater contamination. Implementation of the alternative would not result in any increased risk to public health, provided dermal contact by workers with contaminated surface water, sludge, and sediment is minimized during remedial operations.

The cover system and bio-intrusion barrier option would reduce the potential for disturbance of the waste sludge. Coupled with the removal of contaminated ponded water from pits and lagoons, this alternative would reduce the potential for direct contact with contaminated wastes at the STWP site by aquatic and terrestrial receptors. Direct contact with contaminated sediments by burrowing animals below the clean cover soil would be reduced or inhibited due to the presence of the bio-intrusion barrier. Macro-benthic invertebrates, which burrow up to 20 cm, would not be as likely to be exposed to contaminated soils and sediments.

Although aquatic and terrestrial ecosystems at the STWP site have undergone perturbations from the chromium contamination, as discussed in the Environmental Risk Assessment, Section 10.0 of the Phase II RI report (E.G. Jordan, 1987) , waste pits and lagoons are being used by aquatic and terrestrial flora and fauna. Therefore, covering contaminated sludge would result in the destruction of habitat and food resources for aquatic and terrestrial biota. Restoration of a comparable wetland may be sufficient to re-establish necessary food and habitat requirements for biota; however, the time lapse between destruction of the existing habitats and restoration of compensatory wetlands could be deleterious to the more sensitive aquatic and terrestrial biota. Use of on-site wetlands by migratory birds and aquatic insects would be hampered by dewatering and covering waste pits and lagoons.

This remedial alternative will be effective in protecting the environment. Burrowing mammals and aquatic insects still may be at risk from direct contact to contaminated sludge below the clean topsoil; however, this is unlikely with 3 to 5 feet of till cover

2 - 2 8

soils and a gravel and rock bio-intrusion barrier. Habitat areas destroyed in this process would have to be replaced based on food and habitat requirements of aquatic and terrestrial organisms at the site. Short-term mitigation of contaminated pits and lagoons, as well as re-construction of wetlands, will probably affect the socio-economic value (aesthetic value) and wildlife value (food and habitat value) of associated environs at the STWP site.

The use of a bio-intrusion barrier, the geotextile, and covering waste pits and lagoons should deter or minimize direct contact by burrowing biota with contaminated sludge. The loss of wetlands from placing cover soils can only be justified by the restoration of wetlands of equal or greater functional value. Therefore, this alternative, provided compensatory wetlands are established, is beneficial in protecting the environment under the conditions outlined herein. Long-term Operation and Maintenance requirements involve monitoring the groundwater for migration of contaminants that pose a risk to public health and the environment, and repair, regrading, and revegetation to maintain the integrity of the soil cover system.

State Acceptance.

No assessment of state acceptance is given at this time. Formal comments will be provided by the state for this alternative during the comment period for this Feasibility Study Addendum report. These comments will be evaluated and discussed in the Record Of Decision (ROD) and the Responsiveness Summary*

For the STWP site, formal public comments will be provided during the 21-day public comment period on the FS Addendum report and Revised Proposed Plan. Specific public concerns or comments will be addressed in the ROD and Responsiveness Summary.

Table 2-2 summarizes the nine evaluation criteria for Alternative SC-3A. For the comparison of Alternative SC-3A to the other remedial alternatives presented in Table 9-1 of the F. S. Report, a summary of Alternative SC-3A is presented in Table 2-3 of the report.

2 - 2 9

TABLE 2-2

EVALUATION CRITERIA SUMMARY ALTERNATIVE SC-3A COVER SYSTEM WITH INSTITUTIONAL CONTROLS

SACO TANNERY WASTE PITS SITE SACO, MAINE

CRITERIA

1 Short Term Effectiveness

Protection of community during remedial actions DG

Protection of workers during remedial actionsDG

• Environmental impacts from remedial actionsG

• Time until remedial action objectives are achieved °

2 Long-term Effectiveness

• Magnitude of residual risk A B c G

• Adequacy of controls to manage treatment residuals or untreated wastes A 8 f G

• Reliability of controls for providing continued protection from residuals A B F G

Reduction of Toxicity, Mobility, or Volume

• Treatment process employed, and type of materials to be treated

ASSESSMENT

No significant risks expected during pumping of ponded water and covering operations

Minimal risk during site preparation, pumping ponded water, or covering pits/lagoons

Pumping ponded water and covering pits/lagoons would destroy wetland habitats However, compensatory wetland area would be reestablished on-site

Remedial action objectives related to ponded water and contaminated sludge and sediment achieved in 1 5 years Objectives established to prevent or reduce the threat of potential groundwater contamination by leaching addressed by establishment of monitoring network and contingency for treatment for as long as the wastes remain untreated

Potential leaching of contaminant to groundwater remain Designation of conservation area restricts future development and groundwater usage

Untreated but covered wastes would be monitored through site inspections and groundwater monitoring Rock and gravel layers inhibit penetration by burrowing animals

Periodic monitoring would effectively and reliably assess future leaching and groundwater contamination Contingency plan exists to address future contaminant migration

Ponded water -- pump and treat off-site Sludge and sediment -- permeable cover soils

3

TABLE 2-2 (Continued)

EVALUATION CRITERIA SUMMARY ALTERNATIVE SC-3A COVER SYSTEM WITH INSTITUTIONAL CONTROLS

SACO TANNERY WASTE PITS SITE SACO. MAINE

Amount of hazardous materials to be destroyed or treated

Degree of expected reduction in toxicity, mobility, or volume, is it permanent or significant7 B

Degree to which treatment will be irreversible

• Type and quantity of residuals remaining after treatment C.Q

4 Implementabihty

• Ability to construct and operate technology

• Reliability of technology

Ability to undertake additional remedial actions, if deemed necessary in the future

Ability to monitor effectiveness of remedy

Ability to obtain approvals from other agencies

Ponded water - 0 5 to 2 8 MG pumped and treated Sludge and sediment - 100,000 cy remain untreated

Ponded water -- permanent reduction in volume Sludge and sediment -- no reduction in mobility, toxicity, or volume

Ponded water -- off-site treatment Sludge and sediment -- not applicable; no treatment processes employed

Ponded water -- removed from site Sludge and sediment - 100,000 cy remain untreated

Ponded water -- pumping easy to implement Sludge and sediment -- covering can be implemented and is technically feasible.

Ponded water -- off-site treatment at POTW or TSD facility reliable Sludge and sediment -­cover reliable if erosion is minimized and wastes are not exposed Bio-intrusion barneis reduce risk of disturbance of sludge

Ponded water - additional pumping could be easily undertaken Sludge and sediment -­additional remedial action could be taken by removing cover soils and excavating wastes

Ponded water -- pumping effectiveness easily monitored Sludge and sediment -- monitor cover by site inspections; monitor potential contaminant leaching by sitewide groundwater sampling

Ponded water -- approvals for treatment at POTW or TSD facility necessary Legislation ­dependent of Maine legislature

TABLE 2-2 (Continued)

EVALUATION CRITERIA SUMMARY ALTERNATIVE SC-3A COVER SYSTEM WITH INSTITUTIONAL CONTROLS

SACO TANNERY WASTE PITS SITE SACO, MAINE

Activit ies needed to coordinate with other Ponded water -- coordination required to offices/agencies obtain permits for off-site water treatment

Sludge and sediment - coordination required for plans to establish compensatory wetlands

• Availability and capacity of off-site treatment, Ponded water - City of Saco POTW has storage, disoosal services expanded and would have adequate capacity

and services TSD facility may be used, but at increased costs Sludge and sediment -- cover system would not require off-site TSD services

• Availability or necessary equipment and soecialists Ponded water -- necessary equipment and services available for pumping, transporting, and treating Sludge and sediment ­equipment and services for cover work readily available

Availability or orospective/mnovative technologies Not applicable, no innovative technologies under consideration employed

5 Cost

• Capital costs Estimated at $6 8 million

• Operation and maintenance costE Post-closure annual cost estimated at $421,800 per year for years 0-2 and $215,200 for years 2-30

• Costs ot five-year review, it required $20,400 each

• Present worth analysis Estimated at $10 5 million

• Potential future remedial action costs F Several million dollars depending on future remedial action

6 Compliance with ARARs

• Chemical-specific ARARs B Compliance achieved

• Location-specific ARARs B Compliance achieved

• Action-specific ARARsb Compliance achieved

• Appropriate criteria, advisories, guidancea Compliance achieved

7

TABLE 2-2 (Continued)

EVALUATION CRITERIA SUMMARY ALTERNATIVE SC-3A COVER SYSTEM WITH INSTITUTIONAL CONTROLS

SACO TANNERY WASTE PITS SITE SACO. MAINE

Overall Protection of Public Health and the Environment

• Protection of public health C.D.G Risks from direct contact significantly reduced by cover.

• Protection of the environment c D G Environmental impacts from ponded water addressed. Contaminated sludge remains, however potential for future migration addressed by contingency plan. Rock and gravel barriers inhibit contact by burrowing biota with residual sludge. Compensatory wetland area to be established.

8 State Acceptance

• Components that the state supports Formal comments will be provided by the state during comment period for this final FS Addendum and will be addressed in the ROD and responsiveness summary.

• Components about which the state has reservations

• Components the state strongly opposes

9. Community Acceptance

• Components the community supports Specific public concerns will be addressed in the ROD and responsiveness summary.

• Components aoout which the community has reservations

• Components the community strongly opposes

NOTE: Footnoted criteria correspond to the following statutory factors in CERCLA as amended, Sections 121(b) (1) (A through G):

A = the long-term uncertainties associated with land disposal B = the goals, objectives, and requirements of the Solid Waste Disposal Act C = the persistence, toxicity, mobility, and propensity to bioaccumulate of the hazardous

substances and their constituents D = short-and long-term potential for adverse health effects from human exposure E - long-term maintenance costs F = the potential for future remedial action costs if the alternative remedial action in question were to fail G = the potential threat to human health and the environment associated with excavation, transportation, and

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3.0 COST SUMMARY OF REMEDIAL ALTERNATIVES

Table 3-1 presents a summary of costs (using 1989 present worth estimates) for each alternative evaluated in the Feasibility Study report and for the preferred alternative SC-3A. A detailed description for each alternative can be found in the FS report.

3 - 1

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