POSITION PAPER OF THE GENERAL ELECTRIC COMPANY ON EPA REGION I'S DRAFT ENGINEERING EVALUATION/COST ANALYSIS

FOR THE V/2 MILE REACH OF THE HOUSATONIC RIVER

Prepared for The National Remedy Review Board

U.S. Environmental Protection Agency

April 14,2000

1.0 INTRODUCTION

The General Electric Company (GE) submits this position paper on EPA Region Is draft Engineering Evaluation/Cost Analysis for the Upper Reach ofthe Housatonic River (EE/CA), dated February 11, 2000. That document discusses and evaluates options for a Removal Action to be implemented by EPA in the 1 Va Mile Reach of the Housatonic River in Pittsfield, Massachusetts (between Lyman Street Bridge and the confluence of the East and West Branches of the River) pursuant to a Consent Decree (CD) executed by GE, EPA, and other governmental entities and lodged in U.S. District Court on October 7, 1999.

The draft EE/CA proposes the removal and replacement of an immense quantity of sediments and riverbank soil in the l'/2 Mile Reach, mainly to address the presence of PCBs in those media. For the following reasons, GE believes that the Region's proposed approach goes far beyond what is necessary to be fully protective of human health and the environment in this Reach.

• The scope of the removal program is based on the use of overly stringent cleanup criteria and an overly conservative approach in applying those criteria.

• The proposed action will cause great disruption to the nearby residents, as well as to recreational and commercial activities in the area, for a considerable period of time, and will have long-term adverse impacts to local communities and the environment.

• The proposal is inconsistent with the removal action adopted by EPA for the Upper '/z Mile Reach (immediately upstream of the EE/CA Reach) and for other areas addressed by the CD - actions that EPA has determined are fully protective - while requiring, without adequate justification, far more removal to address areas with lower PCB concentrations.

• The program will needlessly waste limited resources (e.g., using up consolidation space with relatively clean material), is more costly than necessary to be protective, and will take significantly longer to implement than a more cost-effective, less complex, but equally protective approach.

• Some of the removal technologies retained by the Region for further consideration are, at a minimum, impractical, and at worst, capable of causing significant resuspension and transport of PCB-containing sediments downstream of the EE/CA Reach, which is currently undergoing extensive evaluation by the Region and GE.

These severe impacts are both unnecessary and avoidable. There are several alternatives to the Region's proposed program that have less severe impacts and are fully protective of human health and the environment in thelVz Mile Reach. The draft EE/CA fails to give adequate consideration to these alternatives. EPA has a duty under the National Contingency Plan (NCP) to give further consideration to these alternatives. GE urges the Board to recommend that the Region do so.

2.0 DESCRIPTION AND IMPACTS OF THE REGION'S PROPOSED REMOVAL PROGRAM

The Region proposes a massive sediment and bank soil removal program consisting of approximately 90,000 cubic yards (cy) of material along a stretch of the River that is bounded by both homes and businesses, steep banks and heavily vegetated riparian corridors.

• The entire River bottom in the I'/z Mile Reach will be removed - more than 43,000 cy of sediments in a bank-to-bank excavation to a depth of between 2 and 3.5 feet, resulting in the complete destruction of the existing aquatic habitat.

• The banks of the River will likewise be removed - some 46,500 cy of bank soils will be excavated from the water's edge to the top of the bank along both sides of the l'/2 Mile Reach, largely to a depth of 3 feet.

• All mature trees and other vegetation on the banks of the entire l'/2 Mile Reach will be destroyed, causing lasting devastation of the natural beauty and the habitat of the area.

• These extensive removal actions raise significant practicability issues and will cause substantial disruption and adverse impacts to the community due to the construction of access roads and soil/sediment stockpiles along the banks of most of the 1 Vi Mile Reach that are required to implement the proposed actions.

• The Region's proposal will cause an increase in truck traffic over the life of the project of about 12,000 round trips on residential streets that were not designed to absorb that level and type of use, as well as continuous noise impacts from sheetpile hammers, dump trucks, diesel pumps, backhoes, cranes, and other equipment.

Figures 1A and IB summarize the extent of sediment and bank soil removal that the proposed program will require, and provide an overview of some of the ancillary components (e.g., staging/storage areas and access road construction areas) that the Region has said will be necessary to accomplish this large-scale removal.

Construction Activities Along Both Sides of the Reach will Significantly Disrupt the Bordering Residential and Commercial Communities

• EPA will have to construct access roads and staging/storing areas along both banks of the l'/2 Mile Reach. This will substantially disrupt both the residential community and the bordering commercial establishments (which include car dealerships, restaurants, grocery stores, a welding facility, a car wash, a laundromat, a golf shop, and a multi-use facility that includes the Region's own Pittsfield office/lab space). Delays will also result as some property owners inevitably refuse to grant temporary construction easements causing EPA to modify and/or revisit its construction design to handle such setbacks . As shown on Figures 1A and IB:

More than 10 acres for primary access routes/areas alone will be required if excavation of the entire ll/2 Mile Reach is selected as the base removal alternative. The access routes/areas will be up to 30-feet wide, running along the top of both banks. There are an estimated 40 residential properties that will be affected by these easements. In many cases, construction easements will directly abut homes - some of which GE has already remediated. Four "stabilized staging/storage areas" - areas where excavated material will be dewatered and construction equipment will be stored and decontaminated - will be located directly on residential properties . Residents of those properties will experience significant disruptions associated with the handling of stockpiled PCB-containing soils/sediments on their properties, including noise, dust, vibration impacts from front-end loaders, backhoes, and dump trucks, and overall loss of aesthetic values. Use of a City park as a staging/storage area, as currently proposed by the Region (see Figure IB), will obviously preclude its use for recreational purposes.

• A dry excavation approach would entail the 24 hour a day, 7 day a week use of a water treatment system during dewatering and excavation activities. The Region anticipates that this system will consist of a frac tank, pump, filters, carbon units, and piping. Use of such a system may be inadequate in removing PCBs to an acceptable concentration. The Region states that this system will be set up at each sheetpile cell along the river, and assumes 18 separate setup/teardown events. While the space

DRY EXCAVATION WITH SHEETPILE

DRY EXCAVATION BY BYPASS PUMPING FROM TRANSECT #106 TO TRANSECT #156

SOIL EXCAVATION DEPTHS; SEDIMENT EXCAVATION DEPTHS:

2 FT. SEDIMENT _i Z_ BUILDINGS AND STREETS

2.5 FT. SEDIMENT __ _ _ __ TEMPORARY CONSTRUCTION EASEMENT

— —— — LIMIT OF EE/CA REMOVAL 3.0 FT. SEDIMENT

APPROXIMATE LOCATION OF STABILIZED 3.5 FT. SEDIMENT STAGING/STORAGE AREA

RESIDENTIAL USE

RECREATIONAL USE

COMMERCIAL/INDUSTRIAL USE

AREA TO BE USED AS WORK AREA FOR STAGING EQUIPMENT, STOCKPILING AND STABILIZING EXCAVATED MATERIAL, WATER TREATMENT, ACCESS ROADS, ETC.

1 SITE FEATURES, CONSTRUCTION AND REMOVAL INFORMATION BASED ON FIGURES BY WESTON.

2. THIS FIGURE SHOWS THE LIMITS OF SEDIMENT 300' 600' AND BANK SOIL REMOVAL AS PROPOSED IN THE DRAFT EE/CA. THE CONSTRUCTION APPROACH SHOWN IS BASED GENERALLY ON BASE ALTERNATIVE 2, AS DESCRIBED IN THE GRAPHIC SCALE EE/CA.

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GENERAL ELECTRIC COMPANY PITTSFIELD MASSACHUSETTS

ORIGINAL INCLUDES COLOR CODING. Available at the US EPA New England Superfund Records Genier, Borton, MA

EE/CA REMOVAL/CONSTRUCTIONAPPROACH

FIGURE P: WESTON1 BUSLAND, BOUCK * IK. INC. L ON-*, OFF-REF engineers & scientists 1A 4/3/00 SYR-54-RLP MAD C: /IE*P/WESTON1/tneiC.DWG

DRY EXCAVATION BY BYPASS PUMPING FROM TRANSECT #106 TO TRANSECT #156

DRY EXCAVATION WITH SHEETPILE

SCHL_ EXCAVATION DEPTHS: SEDIMENT EXCAVATION DEPTHS:

2 FT. SEDIMENT NO EXCAVATION

2.5 FT. SEDIMENT 1 FT. SOIL

3.0 FT. SEDIMENT 2 FT. SOIL

3.5 FT. SEDIMENT 3 FT. SOIL

, ——- BUILDINGS AND STREETS

_ _ __ TEMPORARY CONSTRUCTION EASEMENT

—— — LIMIT OF EE/CA REMOVAL

APPROXIMATE LOCATION OF STABILIZED STAGING/STORAGE AREA

TAX PARCEL BOUNDARY

RESIDENTIAL USE

RECREATIONAL USE

| | COMMERCIAL/INDUSTRIAL USE

AREA TO BE USED AS WORK AREA FOR STAGING EQUIPMENT, STOCKPILING AND STABILIZING EXCAVATED MATERIAL, WATER TREATMENT, ACCESS ROADS, ETC.

1. SITE FEATURES, CONSTRUCTION AND REMOVAL INFORMATION BASED ON FIGURES BY WESTON. 300' 600

2. THIS FIGURE SHOWS THE LIMITS OF SEDIMENT AND BANK SOIL REMOVAL AS PROPOSED IN THE DRAFT EE/CA. THE CONSTRUCTION GRAPHIC SCALE APPROACH SHOWN IS BASED GENERALLY ON BASE ALTERNATIVE 2, AS DESCRIBED IN THE EE/CA.

GENERAL ELECTRIC COMPANY PITTSFIELD MASSACHUSETTS

EE/CA REMOVAL/CONSTRUCTIONAPPROACH

ORIGINAL INCLUDES COLOR CODING. FIGURE BLASLAND, BOUCK t LEE, INC.

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requirements to set up and operate such a system are virtually ignored in the EE/CA, the activities required to setup, operate, and teardown this system will inevitably disrupt the local community.

• If the pump bypass technique is used for sediment removal, there will be other substantial impacts to adjacent property owners. The EE/CA describes a pump bypass system designed to handle a flow of 120 cubic feet per second (cfs), which uses 10 diesel-powered pumps and two 36-inch diameter discharge lines. An area approximately 100 feet by 35 feet along the riverbank will be reportedly required for the pumps, while the two discharge lines will be installed along the bank or edges of roadways. To maintain a dry excavation area, the diesel pumps will need to operate 24 hours a day, resulting in the significant disturbance of adjacent residential and commercial owners and patrons with diesel fumes and continuous noise. In addition, the significant activities associated with constructing a pump bypass system may impede use of residential streets and portions of residential properties.

• Nearby residents and commercial owners/patrons will experience increased truck traffic, estimated in the EE/CA at 20 to 40 round trips per day during construction activities, for a total of about 12,000 round trips not counting truck trips for off-site disposal. This extra traffic will increase noise, vibration, dust, and vehicle fumes and will pose an increased risk of accidents, as well as the potential release of contaminated material. As noted in the EE/CA, the existing roads in the vicinity of the removal areas downstream of Elm Street are relatively narrow and were designed for residential use. The local infrastructure (e.g., bridges, roads) is likely inadequate to handle the wear of the anticipated 30-ton trucks.

The Removal Program Described in the EE/CA Will Result in the Complete Destruction of All Adjacent Habitat - The proposed activities will completely destroy the existing habitat along the 1 '/2 Mile Reach. All the existing shoreline vegetation, which includes many mature trees, will have to be cut down, dramatically altering the natural vistas and displacing native wildlife that inhabits these areas. The River will resemble a large drainage channel. It will take decades before the full revegetation of the banks can occur.

Wet Excavation and Pump Bypass Techniques Present a Substantial Risk of PCB Resuspension and Transport

• With wet excavation, resuspension and transport of some PCB-containing sediments will inevitably occur since this technology is an inexact method and crude removal approach relying on traditional construction equipment that is used to blindly remove sediments in a flowing river. Efforts to deflect the main river current through the use of Jersey barriers to minimize PCB transport downstream will be largely ineffective. At sites like the Sheboygan River (WI), the Fox River (WI), the Manistique River (MI) and the Grasse River (NY), where removal of sediment through the water column has occurred, the release of PCBs beyond the work area has been documented in the water column and, in some cases, in biota, even with up to three silt containment barriers (Grasse River) in place.

• With pump bypass, downstream impacts will occur during times when the river flows exceed the limited capacity of the bypass system (120 cfs) and river water flows through the active excavation areas. The EE/CA (p. 5-56) admits that overtopping of the pumping bypass system is likely to occur during the remediation, and (p. 5-45) that flows do not exceed 120 cfs 70% of the time, meaning that flows do exceed the design capacity of the system 30% of the time. In fact, as shown in Figure 2, the percentage of days exceeding 120 cfs range from about 5% in August (approximately 2 days per month) to about 77% in April (approximately 23 days per month).

• The EE/CA fails to account for the significant delays when the river flow will overtop the bypass structure and flood into the excavation area, as well as the project delays associated with dewatering the work area again after the flow rates have decreased below 120 cfs. Each overtopping event will cause several days of project delay. Note that even short-term river flow peaks in excess of 120 cfs will flood

out the excavation, even though the daily average flow as illustrated on Figure 2 will be less than 120 cfs.

• A significant effect of the resuspension and downstream transport of PCB-containing sediments will be a likely increase in PCB concentrations in fish and wildlife below the I'/z Mile Reach - an area that is itself the subject of a massive EPA sampling and analysis program through a process described in the CD.

• The EE/CA admits (p. 5-65) that, with pumping bypass, there would be "heavy use" of diesel fuel near the river, creating a further potential risk of releases.

The Region Grossly Overestimates Excavation Production Rates Resulting in an Unrealistic Project Schedule - The proposed removal actions will almost certainly take longer than the 2-3 years that the Region estimates. The EE/CA estimates excavation rates of 250-300 cy/day. Based on GE's experience on the ongoing Upper Vi Mile Reach Removal Action, more realistic site-specific excavation rates on days when excavation is being conducted are 130 cy/day. This suggests that the excavation portion of the proposed project will likely take twice as long as the Region estimates.

Further, if comparisons to the Upper l/2 Mile Reach project are made from an overall project duration standpoint, EPA's proposed project could take significantly longer. For example, the estimated project duration for the Vi Mile project is approximately 19 months for removal of 12,400 cy; extrapolating this rate to the EE/CA volume of 89,700 cy results in a project duration of at least 5 years. This schedule slippage is even more likely when a comparison with the logistics encountered in the '/z Mile Reach (conducted on property largely owned by GE on both sides of the river with accessible power, water treatment facilities, stockpile and equipment storage areas, and paved work platforms) is made to the conditions associated with the 1 V* Mile Reach (approximately 50 individual property owners with various access concerns, steep, inaccessible banks, and limited areas for stockpiling materials, storing equipment, and setting up water treatment facilities).

In light of these severe impacts, it is incumbent upon EPA, under the NCP, to evaluate other alternatives that can achieve, more quickly and cost-effectively, protection of human health and the environment with less disruption and adverse impacts. A number of such alternatives are available for both bank soils and sediments, as discussed below.

3.0 ALTERNATIVES FOR BANK SOILS

3.1 The PCB Cleanup Criteria Should be Consistent with the Levels Applied to the Upper ¥2 Mile Reach

The Region's selected PCB cleanup criterion of 2 ppm for the banks of residential properties is consistent with the standard that EPA selected in the CD for accessible portions of residential properties. (While GE does not explicitly question this criterion, GE does not believe that many of the residential banks in the l'/2 Mile Reach are accessible and, thus, appropriate candidates for removal.)

However, the Region's recreational-use criterion of 10 ppm in the top 3 feet is inconsistent with the criteria selected by EPA for the banks in the ¥2 Mile Reach, as well as for other recreational areas addressed by the CD where land use restrictions (known as Environmental Restrictions and Easements or EREs) are obtained. Those criteria are 10 ppm in the top foot and 15 ppm in the 1-3 foot depth increment. EPA has determined that, for recreational properties addressed in the CD, Removal Actions achieving these levels are fully protective of human health and the environment. The draft EE/CA presents no reason why these levels are not protective for the recreational banks in the Wi Mile Reach or why a stricter cleanup criterion is necessary. The EE/CA itself states (p. 3-5) that EREs will be obtained in areas where there is a potential for exposures inconsistent with recreational use (e.g., future residential use) or where exposures may occur at depths greater than 3 feet. For

the remaining banks (e.g., those that are sufficiently steep as to be unusable for uses other than recreational), there would be no need for EREs. In these circumstances, there is no reason to depart from the criteria selected for the Upper '/2 Mile Reach banks.

3.2 The Region's Incorrect Application of the Cleanup Criteria Results in Extensive Additional Removal

The Region's use of the 95% UCL/maximum concentration approach for the banks of the \l/i Mile Reach is inappropriate. The Region should have used a spatial averaging technique that EPA approved in the CD for the banks in the l/2 Mile Reach and other areas. That approach uses Thiessen polygons to calculate spatially weighted average concentrations for a given area, which are more representative of the actual concentrations contacted by receptors in the area over time. It then assumes the selective removal and replacement of soils in particular polygons until the spatial average falls below the applicable cleanup criterion. In the CD, EPA determined that Removal Actions using this approach are wholly protective of human health and the environment. Indeed, in the Responsiveness Summary for the l/i Mile Reach, EPA noted specifically that this spatial averaging approach "can be used to determine compliance with cleanup levels," provided that "there is a sufficient sample density within an averaging area." Misapplication of the 95% UCL approach will:

• Distort actual exposure point concentrations and produce concentrations far higher than the true mean. The problems with this technique are described in Attachment A.

• Result in the removal of about 6,700 cy of soils that contain PCB concentrations less than 2 ppm, which is the level deemed acceptable both in the CD and by the Massachusetts Department of Environmental Protection (MDEP) for unrestricted use. Using the 95% UCL approach will mean that these soils will be excavated unnecessarily, wasting valuable space in the on-plant consolidation areas or at an off-site treatment facility.

• Result in the wrongful excavation of about 46,500 cy of bank soils instead of 8,000 cy of bank soils that need to be excavated under the spatial averaging approach that EPA approved and found to be protective for the Upper Vi Mile Reach.1

• Figures 3A and 3B illustrate the extent of bank soil removal to address PCBs using the spatial averaging approach. A comparison of the extent of bank soil removal on Figures 1A and IB (resulting from the misapplication of the 95% UCL approach) compared to Figures 3A and 3B (the spatial averaging approach) illustrates the extensive devastation associated with the Region's application of the cleanup criterion - essentially the complete destruction of all vegetation along both banks of the ll/2 Mile Reach and extensive excavation with the associated impacts to the adjacent residential and commercial owners and patrons.

GE urges the Board to recommend that the Region reexamine the application of the bank soil cleanup criterion and use the spatial averaging approach approved for the '/z Mile Reach.

3.3 Bank Slope Angles

The draft EE/CA proposes deep cuts in bank soils that will flatten the banks beyond existing contours and result in unnecessary soil removal. Based on the bank stability calculations in Appendix N, the Region proposes to

]The 864-foot long west bank in subreach 3-10 was not included in GE's assessment since no data were collected by EPA from that area (see Figure 2.3-3C of the EE/CA). EPA has proposed in the EE/CA to remove soil to 3 feet along the entire 864-foot west bank stretch without data to support such an action. Data should be collected from the west bank in subreach 3-10 before proposing any action within that area.

1. SITE FEATURES BASED OH FIGURES BY WESTON.

2. THIS APPROACH IS BASED ON; (1) FOR SEDIMENTS, AN 1B"-24" REMOVAL/CAPPING APPROACH SUCH AS THAT APPROVED BY THE ERA FOR THE UPPER 1/2 MILE REACH; AND (2) FOR BANK SOILS, A SPATIAL AVERAGING APPROACH SUCH AS THAT APPROVED BY EPA FOR THE UPPER 1/2 MILE REACH.

3. NO REMOVAL IS PROPOSED FOR THE SECTION OF THE WEST BANK THAT EXTENDS 864 + /­FEET UPSTREAM FROM ELM ST. SINCE NO DATA WERE COLLECTED BY EPA.

— —— — LIMIT OF EE/CA REMOVAL

^^ BUILDINGS AND STREETS TAX PARCEL BOUNDARY

RESIDENTIAL USE

[ | RECREATIONAL USE

COMMERCIAL/ INDUSTRIAL USE

SEDIMENT EXCAVATION DEPTHS:

NO EXCAVATION | | NO EXCAVATION

1 FT. SOIL [•••;:.'y ;--| 1.5 FT. SEDIMENT

2 FT. SOIL | | 2 FT. SEDIMENT

3 FT. SOIL

600'

GENERAL ELECTRIC COMPANY PITTSFIELD MASSACHUSETTS

ALTERNATIVE EE/CA APPROACH ORIGINAL INCLUDES COLOR CODING. BASED Available at the US EPA New England Superfund Records Ccn.er, Boston, MA ON UPPER 1/2 MILE APPROACH

FIGURE BUSLAND, BOUCK t LEE, INC. P: WESTON1

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— —— — LIMIT OF EE/CA REMOVAL BUILDINGS AND STREETS TAX PARCEL BOUNDARY

RESIDENTIAL USE

RECREATIONAL USE

COMMERCIAL/ INDUSTRIAL USE

SOIL EXCAVATION DEPTHS: SEDIMENT EXCAVATION DEP1>

NO EXCAVATION | | NO EXCAVATION

1 FT. SOIL [-; 'I 1.5 FT. SEDIMENT

l 2 FT. SOIL | | 2 FT. SEDIMENT

3 FT. SOIL

1. SITE FEATURES BASED ON FIGURES BY WESTON.

2. THIS APPROACH IS BASED ON: (1) FOR SEDIMENTS, AN 18"-24" REMOVAL/CAPPING APPROACH SUCH AS THAT APPROVED BY THE EPA FOR THE UPPER 1/2 MILE REACH;

300' 600' AND (2) FOR BANK SOILS, A SPATIAL AVERAGING APPROACH SUCH AS THAT APPROVED BY EPA FOR THE UPPER 1/2 MILE GRAPHIC SCALE REACH.

GENERAL ELECTRIC COMPANY PITTSFIELD MASSACHUSETTS

ALTERNATIVE EE/CA ORIGINAL INCLUDES COLOR CODING. APPROACH BASED

Available at the US EPA New England Superfiihd Records Corner, Boston, MA ON UPPER 1/2 MILE APPROACH FIGURE

P: WESTON1 BUSLAND, BOUCK t LEE. INC. L ON=*, OFF=REF engineers & scientists 3B 4/3/00 SYR-S4-RLP MAD 20192010/WESTON1 /FIB3A.DWS

achieve final slopes of 2.25H: 1V (or flatter) where possible; and for areas where that final slope cannot be achieved consistent with the objective of maintaining the existing crest of the slope, it proposes use of retaining structures. This approach is unnecessary for several reasons:

• As discussed in Attachment B, this approach would require the excavation of a considerable volume of soil (up to an additional 55,000 cy) that is not necessary to achieve the cleanup criteria. This extra removal could be avoided by the use of steeper temporary and permanent slopes, with use of standard in-situ geotechnical reinforcement techniques and/or temporary shoring where necessary.

• As shown in Attachment B, many of the existing banks in this reach have existing slopes steeper than 2.25H:1V, including 1H:1V slopes up to 20 feet high in some places, and there is no physical evidence that these banks are unstable (as the EE/CA calculates they would be).

• Both for prior interim remedial measures in this reach and in the Upper Vi Mile Reach, steep banks have been successfully excavated without failure (using temporary shoring as needed), and EPA has approved bank restoration to final slopes up to 1H: 1V, with appropriate use of in-situ reinforcing techniques, such as soil nailing, as needed. A similar approach should be used for the IVi Mile Reach banks.

4.0 ALTERNATIVES FOR SEDIMENTS

4.1 The Region's Selection and Application of Cleanup Criteria for PCBs in Sediments Is Wrong

The Region's proposed PCB cleanup criterion of 1 ppm for sediments is based on a memorandum dated February 7, 2000 (in Appendix Q to the EE/CA), which attempts to justify that criterion as necessary to protect ecological receptors that inhabit the river or feed on aquatic life. That conclusion is not scientifically defensible, because:

• It relies exclusively on a comparison of sediment PCB concentrations with a number of generic sediment quality guidelines developed by EPA, the National Oceanic and Atmospheric Administration (NOAA), and the Ontario Ministry of the Environment, and does not take into account any site-specific data regarding actual ecological receptors in the IVz Mile Reach.

• As shown in Attachment C, the sediment guidelines used were not intended to predict adverse effects. Rather, they were developed, using highly conservative assumptions, solely for use as screening-level values, and the guidelines themselves acknowledge that they should be used only for such screening purposes.

• As further shown in Attachment C, EPA's own guidance documents on ecological risk assessments make clear that cleanup decisions should not be based on such screening-level assessments, but rather on site-specific data.

Accordingly, the Region's use of these screening-level sediment quality benchmarks to derive a cleanup criterion for such a large-scale removal action as the one outlined in the draft EE/CA is wrong, misuses the benchmarks, and is inconsistent with the Agency's own guidance.

Instead of selecting any specific cleanup level for sediments at all depths, EPA should adopt an approach such as that specified in the CD to define sediment removal limits for the Upper Vi Mile Reach. As described in the Responsiveness Summary for that Removal Action, "EPA did not explicitly specify a cleanup level for sediment." Rather, to determine the limits of excavation, a "cleanup approach" was used, which relied primarily on reducing the surficial PCB sediment concentrations to less than 1 ppm and excavating sediment to a sufficient depth to allow installation of a cap/backfill configuration that would effectively isolate the residual

sediment PCBs and prevent them from migrating to the surface or water column. This approach is discussed in more detail in Section 4.2.

Even if the Region did adopt a specific PCB cleanup criterion, it should not have applied that criterion to the sediments using the 95% UCL of the data or the maximum concentration for each subreach and depth increment. Use of that approach for sediments is unwarranted for the same reasons discussed in Section 3.2 (see also Attachment A). Even for sediments, spatial averaging would provide a more justifiable and representative approach:

• Spatial averaging, through calculation of a Sediment Weighted Average Concentration (SWAC), has been used previously by EPA at other large PCB sediment sites with a much lower sampling density than collected from the P/2 Mile Reach.

• For example, EPA Region V noted in its February 16, 1999 briefing package to this Board on the Sheboygan River and Harbor Site that the cleanup goal for the Inner Harbor was based on a SWAC. Review of other materials in the Administrative Record in that case shows that this SWAC was calculated from approximately 23 sample locations over the 35-acre Inner Harbor. This corresponds to a density of approximately 1 sample/66,000 square feet, compared to an existing sample density of 1 sample/1,344 square feet for the \Vi Mile Reach of the Housatonic. Spatial averaging has also been used at the Manistique Site, where samples were collected at 53 locations over a 15-acre area, corresponding to a sample density of approximately 1 sample/12,300 square feet.

The Board should recommend that the Region adopt the use of the spatial averaging approach similar to that used for the Upper l/2 Mile Reach that was approved by EPA, rather than using a 95% UCL approach for sediments that is clearly inconsistent with the methodology previously used at this and other PCB sediment sites.

4.2 The Region Should Consider an Alternative Capping Remedy

Rather than specifying a particular cleanup level for sediments,EPA should rely on an approach that incorporates the use of capping, such as that used for the Upper Vi Mile Reach. In the EE/CA, the Region considered a capping alternative, but rejected it on the ground that it will require virtually as much sediment removal to install the cap as would the proposed sediment removal action. That conclusion is wrong.

The Region incorrectly concluded that a 2.5- to 3-foot cap, consisting of a 6- to 12-inch isolation sand layer (between geotextiles), a 6-inch sand and gravel bedding layer, and an 18-inch stone erosion protection layer, is necessary to isolate the residual PCB concentrations and provide adequate erosion protection (see Appendix M to the EE/CA). A cap of that thickness is not needed. In the '/z Mile Reach (where the PCB concentrations in sediments are higher), EPA approved and specified use of a 1.5- to 2-foot thick cap, consisting of a 6- to 12­inch sand isolation layer (between geotextiles), a GeoGrid-layer, and a generally 12-inch-thick stone erosion protection layer. Such a cap is likewise protective for the \Vi Mile Reach. A comparison of these two cap designs is presented on Figure 4.

As shown in Attachment D, the additional elements added in the EE/CA for the IVz Mile Reach cap are based on a number of incorrect and inappropriate assumptions:

• The additional thickness of the stone erosion protection layer is based on the selection of armor stone size, which, in turn, is driven largely by the anticipated velocity of the River during high-flow conditions.

• The flood velocities presented in the EE/CA's Appendix M, however, are grossly overestimated because they are based on: (a) a substantially overstated slope for the river surface during flood

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Erosion Protection Layer Erosion Protection Layer Stone Size D100 = 12" Stone Size D = 9" Isolation Layer

Sand and Gravel Layer Isolation Layer _ _ . . . _ . ... GeoGrid and Geotextile Sediment to Remain

Geotextiles Sediment to Remain Geotextile

CAP CONSIDERED IN EE/CA EPA-APPROVED CAP FOR USE IN UPPER FOR USE IN 1 1/2 MILE REACH 1/2 MILE REACH OF HOUSATONIC RIVER

NOT-TO-SCALE GENERAL ELECTRIC COMPANY PITTSFIELD, MASSACHUSETTS

POSITION PAPER ON DRAFT ENGINEERING EVALUATION/COST ANALYSIS

TYPICAL CAP CROSS SECTIONS

FIGURE BLASLAND, BOUCK & LEE, INC.

03/00 SYR-D54-LBR engineers & scientists20192010/20192g01.CDR BBI

conditions; and (b) an assessment of river cross-section data in isolation, ignoring backwater effects from downstream sections (see Attachment D).

• Correcting for these errors shows that an armor stone size with a median diameter (D50) of approximately 3 inches (rather than the D50 of 6 inches used in Appendix M) is more than adequate to resist erosion forces; this will allow use of a total armor stone layer of 12 inches or less for erosion protection as opposed to the 18-inch thick layer proposed by the Region(see Attachment D).2

Additionally, the 6-inch sand and gravel layer identified in the EE/CA as a bedding layer to protect the underlying geotextile from damage caused by placement of the armor stone layer is unnecessary. Consistent with the cap design approved for the l/2 Mile Reach, a GeoGrid liner can be used instead of the 6-inch sand and gravel layer to provide such protection. In fact, as shown in Attachment D, given the weight of armor stone with a D50 of 3 inches, neither a sand and gravel layer nor a GeoGrid is necessary to protect the underlying geotextile if it is properly selected.

Correcting these two elements in the cap design described in the EE/CA results in a cap with a total thickness of 18 to 24 inches, similar to that approved for the Upper ¥2 Mile Reach. This cap thickness is also appropriate for the P/2 Mile Reach and will be equally protective. Moreover, for stretches where the PCB concentrations are sufficiently low, installation of a cap is not necessary at all, as EPA recognized for the l/2 Mile Reach.

GE has evaluated the application of this capping approach to the \l/2 Mile Reach, using the sand isolation layer thicknesses presented in the EE/CA (i.e., 6 inches for PCBs < 10 ppm and 12 inches for PCBs > 10 ppm). Based on this evaluation (see Figures 3A and 3B), this alternative capping approach will require removal of approximately 21,900 cy of sediment, as opposed to the 43,200 cy proposed in the EE/CA, thereby lessening the disruption, adverse impacts, and delays. If the Region had properly designed the cap system, capping would have been retained as a viable remedy component.

Further, to the extent that the Region, in selecting the thicker cap, has asserted the need to minimize future monitoring and maintenance, that is not an adequate reason. As evidenced by EPA's approval of the l/i Mile cap, such a cap can be readily managed with appropriate monitoring and maintenance (which in any event will be GE's responsibility to conduct under the CD), and any increased costs of such activities will be more than offset by the savings associated with use of such a cap.

4.3 The Region Should Consider the Alternative Remedy of Removal with Partial Backfill Replacement in Select Areas

Even if the Region went forward with its proposed removal approach ~ or for areas where a cap is unnecessary because excavation to a depth of 18-24 inches will remove all sediments that exceed the cleanup criterion — there is no need to backfill the excavation to the original grade. For such areas, EPA should consider an alternative that relies on partial replacement with backfill. This alternative will reduce some of the impacts of the Removal Action, while at the same time providing an opportunity to improve the riverbed habitat. Since less material would be placed in the river, some of the impacts of the project (e.g., truck traffic and the associated noise and dust, time to implement, etc.) will likewise be lessened. Moreover, if properly constructed, partial backfilling in various stretches could improve aquatic habitat conditions by creating more variable water depths and velocities.

4.4 Natural Armoring/Targeted Sediment Removal Is Appropriate in the "Cobble Reach"

"The EE/CA notes (p. M-10) that its armor layer was based on U.S. Army Corps of Engineers guidance (USAGE, 1991/94). In its Responsiveness Summary for the Upper Vi Mile Reach Removal Action, EPA explained that the armor layer design for the V2 Mile cap (12 inches thick) was based on the same Army Corps guidance document.

An additional alternative that should be considered for some River stretches between Elm Street and Dawes Avenue is reliance on natural armoring, with removal of certain exposed sediment pockets where necessary. As described in the EE/CA (p. 2-16), "Subreaches 4-1, 4-2, and 4-3, between Elm Street and Dawes Avenue, are more coarse-grained than the remainder of the river and are characterized by abundant cobbles." These cobbles serve as a natural armoring layer for the underlying sediments, greatly minimizing direct contact with the sediments, as well as sediment scour during periods of high flow. Moreover, this reach contains some stretches with low PCB concentrations, thereby posing no direct contact risk and making no significant contribution to the water column. For example, in the stretch between EPA transects 126 and 138, PCB concentrations range from non-detect to 6.84 ppm, with nearly half the samples showing no detectable PCBs;3 and even the low-PCB concentration sediments are isolated beneath the cobbles.

These conditions, coupled with the fact that this reach is one of the most difficult to access in the entire \Vi Mile Reach due to its steep high banks, make this reach particularly suitable for application of a cleanup approach that relies on the natural armoring characteristics of the reach, with targeted removal of certain exposed sediment pockets where necessary.

5.0 EVALUATION OF TREATMENT ALTERNATIVES

The EE/CA retains on-site ex-situ thermal desorption and solvent extraction as options for handling excavated sediments and soils. Such treatment of excavated sediments/soils prior to consolidation at the On-Plant Consolidation Areas (OPCAs) or off-site disposal is unnecessary. In the CD and the accompanying Action Memorandum for Removal Actions Outside the River (Appendix D to the CD), as well as in the accompanying Responsiveness Summary, EPA has determined that the consolidation of excavated sediments and soils from the l/2 Mile Reach and other areas at the Site within the OPCAs without treatment is fully protective of human health and the environment. Similarly, EPA has frequently approved the off-site disposal of excavated sediments/soils at appropriate disposal facilities without treatment. Consistent with EPA's current policy regarding treatment, EPA noted in the above-mentioned documents that if "principal threat" wastes such as drums of liquid waste containing high PCB concentrations or non-aqueous-phase liquids (NAPLs) are encountered, they will be sent off-site for treatment and disposal, but that the remaining materials will not require treatment and no on-site treatment alternatives need to be considered. The same conclusions apply to the material excavated from the \Vi Mile Reach.

Further, the effectiveness of such treatment technologies in reducing PCB concentrations in the excavated material is not well-established and will have to be assessed through bench-scale testing. For example, moisture content and particle size (e.g., percent silts/clays, percent large debris) may limit or preclude use of either technology. Additionally, the short-term impacts of conducting such treatment at the GE facility, including exposure of the local community, workers, and ecological receptors to emissions and noise, would need to be considered. Given these impacts and the higher costs and lack of need for such treatment technologies, there is no justification for selecting either of the on-site treatment technologies for the P/2 Mile Reach Removal Action.

3These data include results from two "cobble test plots." However, since the cobble test plot sampling method involved separation of the finer grained materials from the coarser grained materials for analysis, the resulting concentrations are not representative of the materials present in the area as a whole. If these data are excluded, the PCB concentrations in this stretch range from non-detect to 4.27 ppm.

6.0 CONCLUSIONS

• The scope of sediment and bank soil removal proposed in the draft EE/CA is based on overly stringent cleanup criteria and an overly conservative approach in applying those criteria. The compounding of these approaches results in massive removals that are much more extensive, complex, costly, and time-consuming than necessary to protect public health and the environment and will produce substantial disruption and negative effects on the local community and environment for significant period of time, with limited incremental benefit.

• Several available removal alternatives and approaches which were not retained for evaluation in the EE/CA can achieve the same degree of protectiveness with far less removal and disruption, more quickly and cost-effectively than some of the removal approaches that were retained. Indeed, some of these approaches were approved by EPA and found to be protective for the Upper l/2 Mile Reach (e.g., spatial averaging for banks, use of an 18-24 inch cap for sediments).

• Under the NCP, EPA is required to evaluate such alternatives further, and the Board should so recommend. For example, when design flaws in the EE/CA are corrected, it is clear that capping is a viable remedy component for the l'/2 Mile Reach.

• The Board should recommend that the ex-situ treatment technologies be dropped from further consideration.

10

Attachment A Assessment of Use of 95% UCL in Environmental Applications

To apply the PCB cleanup criteria to both bank soils and sediments, the draft EE/CA uses the 95% Upper Confidence Limit (UCL) on the mean of the site PCB data (or the maximum concentration if lower) for each reach and depth increment. The 95% UCL was calculated using Land's H-statistic (H-UCL). That statistical technique, however, can result in values that greatly distort actual exposure point concentrations and should not have been used for the 1 Vz Mile Reach.

The H-UCL technique is based on the assumption that the data are lognormally distributed. Small deviations between the assumed lognormal distribution of the data and the actual population distribution can greatly influence the statistical results, yielding a gross misrepresentation of the true mean and associated confidence bound. Even where the data are obtained from a lognormal population, the H-UCL technique can produce concentrations far higher than the true mean. An EPA technical support document entitled The Lognormal Distribution in Environmental Applications (Singh et al., 1998), prepared by EPA's National Exposure Research Laboratory's Technical Support Center for Monitoring and Site Characterization, notes the following in its summary and recommendations:

• "... it is observed that the H-UCL becomes order of magnitudes higher even when the data were obtained from a lognormal population and can lead to incorrect conclusions. This is especially true for samples of smaller sizes (e.g., < 30)."

• "The practical merit of the H-UCL in environmental applications is questionable as it becomes orders of magnitude higher than the largest concentration observed when the [standard deviation] of the log transformed data starts exceeding 1.0."

• "It is therefore, recommended that in environmental applications, the use of the H-UCL to obtain an estimate of the upper confidence limit of the mean should be avoided."

• "Do not use the UCL based on the H-statistic, especially if the number of samples is less than 30." (Emphasis in original text.)

• Even if the lognormal distribution seems to provide a reasonable fit to the data, and if there is evidence of a mixture of two or more subpopulations or if outliers are suspected then using one of the nonparametric methods ... is recommended."

Consistent with these conclusions, a separate analysis of hazardous waste sites in EPA Region 8 notes that the H-statistic "may overestimate the exposure point concentration and may lead to unnecessary cleanup at a hazardous waste site" (Schulz and Griffin, 1999).

Examination of the sampling results presented in the EE/CA indicates that:

• 27 of 45 bank soil sample data sets and 39 of 48 sediment sample data sets had 30 or fewer samples.

• 27 of 45 bank soil sample data sets and 22 of 48 sediment sample data sets had computed 95% UCLs greater than the maximum values observed.

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• Based on a preliminary review of the bank soil and sediment data, the standard deviations of the individual log transformed data sets were consistently greater than 1, usually in the 1.25 to 1.75 range.

• Due to the prior channel straightening and filling of the former oxbows and meanders in this reach of the river, there is a high potential for more than one subpopulation of data.

Given the data variability (log transformed standard deviations of 1.25 to 1.75) and number of samples in each subreach and depth increment, it would not be unusual for the upper 1% of the assumed lognormal population to contribute Vi to % of the total value of the 95% UCL, and the upper 5% to contribute 80 to 90 percent, since in highly skewed data sets with relatively few data points, both the computed mean and 95% UCL are driven by assumptions regarding the upper few percent of the underlying population.

Additionally, the highly variable nature of the data points up the inappropriateness of the Region's decision to remove an entire subreach and depth increment if the 95% UCL (or maximum concentration) exceeds the cleanup criterion. In highly skewed data sets, these values may be driven by pockets of relatively high concentrations intermingled with lower-concentration soils or sediments. In this situation, a more focused removal approach should be used, involving removal of select areas until the cleanup criterion is achieved, and thus leaving intact areas that already meet that criterion.

All these factors indicate that the Region's use and application of the 95% UCL by Land's H-statistic to calculate exposure point concentrations and determine removal limits for the bank soils and sediments in the 1 !/2 Mile Reach was inappropriate and that other statistical techniques should have been used. One such technique, which produces more representative exposure point concentrations and involves more focused removal and which has been approved by EPA for other areas at this same Site, is the use of spatial averaging, as described in the body of this position paper.

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Attachment B Bank Stability Assessment

The EE/CA concludes (see Appendix N) that, to be stable, the bank slopes must be cut back to an angle of 2.25H: 1V or less steep, which is significantly flatter than many of the existing slopes in the 1 Yi Mile Reach. For areas where that slope cannot be achieved consistent with the objective of maintaining the existing crest of the slope, the EE/CA proposes use of retaining structures. These measures would appear to require the excavation of a considerable volume of soil beyond that which is necessary to achieve the cleanup criteria. Based on data in the EE/CA, GE has computed the volume of bank soils that would need to be excavated based strictly on achieving the cleanup criteria; that volume is close to the total volume proposed for removal in the EE/CA. However, such removal would not achieve the bank stability criterion of 2.25H:1V in several areas where retaining structures are not proposed, nor does it take into account the extra removal that would be necessary to install the retaining structures for areas where such structures are proposed (approximately 4,000 linear feet of bank). For example, the EE/CA states (p. L-13) that the reinforced geo-grid retaining structures will be founded 3 feet below the thalweg (deepest point) of the river based on the suppliers' recommendations. This, combined with the typical minimum 6-foot embedded length of geo-grid (Holtz et al., 1997) would force the excavation to be deeper and further back than a simple cut slope. Taken literally, the EE/CA's bank stability conclusions and measures could cause the total excavation volume to double or require the extensive use of temporary shoring, neither of which is included in the EE/CA's volume/cost estimates.

Such extra excavation is unnecessary and could be avoided by using steeper temporary and permanent slopes, with in-situ geotechnical reinforcement techniques and/or temporary shoring on an as-needed basis. There are significant lengths of river bank in this reach that have slopes steeper than 2.25H: 1V, including 1H: 1V slopes up to 20 feet high. These slopes have apparently been acceptable to the government agencies for decades. Although the EE/CA calculates that these slopes should theoretically be unstable, the physical evidence indicates otherwise. For example, the slopes in the straightened sections of the river were designed and constructed by the U.S. Army Corps of Engineers in the 1940s, and GE is unaware of any substantial erosion control measures that have been implemented along this stretch of the river since that time to address potential slope instability. Moreover, for interim remedial measures previously conducted by GE along portions of this reach, EPA and the Massachusetts Department of Environmental Protection have approved plans allowing for slopes of up to 1H:1V, combined with use of in-situ reinforcement techniques (e.g., soil nailing) and temporary shoring as necessary. Similarly, in the Upper Vz Mile Reach, bank slopes of 1H: 1V have been successfully excavated without failure, and restoration of the lower bank to a final maximum slope angle of 1H:1V was approved by EPA.

These factors indicate that EPA should further evaluate the use of steeper slopes for both temporary and permanent conditions. In the limited areas where the existing slopes may show evidence of instability or where slopes steeper than the target slopes would be necessary to avoid impinging on the crest location, use of standard in-situ reinforcement techniques such as previously approved by EPA (e.g., soil nailing) can satisfactorily stabilize the slopes. This approach also has the advantage of not creating any floodway constrictions or requiring flood storage compensation, unlike the EE/CA's proposed use of retaining structures, which would use up existing flood storage capacity and thus require flood storage compensation.

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Attachment C Critique of Region I's Proposed Cleanup Criterion for PCBs in Sediments

The proposed cleanup criterion for PCBs in sediments (1 ppm), which is intended to protect ecological receptors, is based solely on comparisons to generic sediment quality guidelines, rather than site-specific ecological data (see Region I memorandum of 2/7/00 in Appendix Q to EE/CA). This approach is excessively conservative, misuses the guidelines, and conflicts with EPA's own guidance documents.

The NOAA and Ontario Ministry of Environment (OME) sediment quality guidelines cited by Region I as justification for the proposed cleanup criterion are screening values that do not actually predict adverse ecological effects. Both guidelines were derived by correlating measurements of chemical concentrations in sediment with the results of sediment bioassays. They are not based on cause-and­effect relationships (Swartz and DiToro, 1997; Chapman and Mann 1999). Because multiple chemicals are present in nearly all of the tested sediments, it is rarely clear which chemicals are responsible for the observed test results. The developers of the guidelines themselves have warned against using them to define remediation goals. Long et al. (1995), in discussing the NOAA guidelines, stated that: "The numerical guidelines should be used as informal screening tools in environmental assessments. They are not intended to preclude the use of toxicity tests or other measures of environmental effects." Smith et al. (1996), in discussing the OME guidelines, stated that: "The guidelines are intended to be used in Canada as an indication that no adverse effects on aquatic organisms are expected if the measured concentrations of substances in sediments are equal to or lower than the recommended sediment quality guidelines. In contrast, measured concentrations of substances in sediments that are higher than the recommended sediment quality guidelines indicate only that there is the potential for adverse biological effects to occur."

The equilibrium partitioning (EqP) approach, which was also used in the Region I memorandum, involves a number of conservative assumptions. Like the NOAA and OME guidelines, it is intended for identifying sediments that require further investigation rather than for establishing remediation goals. The approach assumes that chemicals present in sediment are fully bioavailable, whereas in reality some fraction is likely to be irreversibly bound to sediment particles. Moreover, the water quality criteria used to derive EqP-based sediment quality guidelines are highly conservative. Concentrations below the criterion values are presumed to cause no adverse effects; concentrations above the values may or may not cause effects depending on site-specific conditions. The Federal Ambient Water Quality Criterion (AWQC) for PCBs, which was used by EPA in its EqP calculations, is not even pertinent to this site. That AWQC was established to protect mink from exposure to contaminated fish, not to protect aquatic biota. The 1 '/•> Mile Reach is heavily urbanized and does not provide suitable habitat for mink.

The Region's use of these screening-level guidelines is inconsistent with EPA's own Ecological Risk Assessment Guidance for Superfund (EPA, 1997) and Ecological Risk Assessment and Risk Management Principles for Superfund Sites (EPA, 1999). The Ecological Risk Assessment Guidance for Superfund states that cleanup decisions should not be based on screening-level assessments, noting (on p. 2-6): "Conservative assumptions have been used for each step of the screening-level ecological risk assessment. Therefore, requiring a cleanup based solely on this information would not be technically defensible." EPA's Risk Management Principles likewise explicitly state (Principle No. 3) that risk managers should "[u]se site-specific ecological risk data to support cleanup decisions," and they note that such site-specific information can include "plant and animal tissue residue data, toxicity test data, bioavailability factors, and population- or community-level effects studies." The generic guidelines used by Region I to support its proposed sediment cleanup goal are screening values and are obviously not "site-specific ecological risk data."

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Attachment D Review of Capping Issue in the EE/CA

In the EE/CA, Region I considered but rejected capping for sediments because the thickness of the cap design prescribed in the EE/CA (Appendix M) ~ 30-36 inches ~ would have required about as much sediment removal as the removal approach proposed in the EE/CA. However, review of the data used in the EE/CA to support that cap design reveals that it was based on a number of inappropriate and incorrect assumptions, resulting in a cap design that is significantly thicker than necessary. Most significantly, the EE/CA has overestimated the required size of the armor stone. As shown below, reassessment of the cap design using more supportable assumptions indicates that a smaller armor stone size ~ e.g., stone with a median diameter (D50) of 3 inches and maximum size (D100) of 6 inches, rather than the D50 of 6 inches and D100 of 12 inches used in the EE/CA ~ would be adequately protective. This would reduce the required armor stone layer from 18 inches to 12 inches or less and eliminate the need for the proposed 6-inch sand and gravel "geotextile protection" layer. These changes would reduce the required total thickness of the cap to 18-24 inches, which is consistent with the cap design specified in the CD for the Upper Vi Mile Reach and determined by EPA to be fully protective. With such a revised cap design, capping should have been evaluated further for the 1 Vi Mile Reach, rather than being screened out from such analysis.

1. Assessment of the Armor Stone Size: The selection of armor stone size is driven largely by the anticipated velocity during high flow conditions. The flood velocities presented in Appendix M have been overestimated, based on: 1) the assumed slope for the river during flood conditions; and 2) the assessment of river cross-section data independently, ignoring backwater effects from downstream sections.

• Slope During Flood Conditions - Based on review of data available in the EE/CA, the slope assumed for the river during flood conditions is too high. The slope selected (0.01 ft/ft) for each cross-section modeled in the EE/CA is six times the average for the 1 Vi Mile Reach (see Figure D-l).1' For comparison, the slope during the 10-year and 50-year flood events, as determined in the FEMA Flood Insurance Study of Pittsfield (FEMA, 1982), are given in the table below. Note that all slopes are below the 0.01 ft/ft used in Appendix M, some significantly less.

Flood Profile Slopes Based Upon WSP2 Model in FEMA (1982)

Water Surface Slope Water Surface During

10-year flood Slope During 50-year flood

Lyman to Elm 0.00029 ft/ft 0.00010 ft/ft Elm to Dawes 0.00356 0.00268 Dawes to Pomeroy 0.00182 0.00152 Pomeroy to Confluence 0.00086 0.00086

When calculating velocity, the computed velocity is proportional to the square root of slope. The computed armor stone D50 size is proportional to velocity raised to the 2.5 power. The effect of changes in slope on velocity and armor stone size (holding all other

- The EE/CA report itself is internally inconsistent with regard to channel slope. On page 2-15 of the text it states "The slope of the riverbed is very gentle, dropping about 10 feet over the 7,550 ft. of the EE/CA Reach. The majority of the 10 foot drop in elevation takes place in the middle third of the reach between Elm Street and Dawes Avenue. The remaining two thirds of the distance accounts for only a 2-foot change in elevation." In a separate appendix on restoration design scenarios (Appendix L), the slope is described as ranging between "flat" and 0.5%. In Appendix M, the maximum slope is mistakenly given as 0.0533 or 5.33%, thus justifying an average of 0.01 ft/ft in subsequent velocity determinations. In Appendix L, three slopes, 0.001, 0.002 and 0.005 ft/ft, are used to determine velocity. In Appendix L, velocity for the 10-year flood ranged from 3.7 to 4.6 ft/sec, less than half the range in Appendix M.

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factors constant) is shown in Figure D-2. As evident on the figure, overestimation of slope leads to a significant overestimation of stone size.

• Backwater effects - During extreme flows, the sections of river controlling flow are those which are least efficient in conveying flow. For example, based on the FEMA (1982) Flood Insurance Report, the three bridges in the 1 !/2 Mile Reach (Elm, Dawes, and Pomeroy) account for approximately 40 percent of the total change in elevation under such conditions, due to their decreased cross-sectional area. This in turn reduces the slope for the remaining, free-flowing sections within the reach. The EE/CA has disregarded the influence of the bridges or other restrictions on flow by performing the calculations of slope for each cross-section in isolation, rather than using a step-backwater model such as HEC-2 or HECRAS. This approach will further overestimate water velocity and thus armor stone size.

GE has calculated the required armor stone size using more realistic flood flow velocities. Based on Figure D-2, actual velocities are expected to be approximately half of those computed in Appendix M, which is consistent with the velocities presented in Appendix L of the EE/CA (Restoration Scenarios). Using the expected range of velocities together with the other factors as given in Appendix M, the required D50 of the armor stone is less than 2 inches, as shown in Figure D-3, as opposed to the D50 of 6 inches used in Appendix M. Even at the unrealistically high velocity of 8 ft/sec, the required armor stone size would have a D50 less than 4 inches (Figure D-3). Thus, it appears that an armor stone size with a minimum DJO of 3 inches would be wholly adequate to resist flood erosion forces.

2. Reassessment of Armor Stone Layer Thickness: Appendix M calculates the thickness of the armor stone layer by using 1 times the D100 of the armor stone (12 inches) and then adding 6 inches to allow for ice and debris flow. The latter allowance is based on a reference (USAGE, 1991/1994) which states that, as a "rule-of-thumb," thickness should be increased by 6-12 inches for "riprap subject to attack by large floating debris." Before immediately applying this rule-of­thumb, it should be recognized that these forces are more of a factor at or near the water line along the bank, where gravity can adversely affect stability, than in the channel bed, where gravity adds to stability. In a discussion of ice damage, the USDOT Design of Riprap Revetment (USDOT, 1989) notes that while moving surface ice can cause shearing forces, "[i]n most instances, ice flows are not of sufficient magnitude to warrant detailed analysis," and that "historic observations of ice flows in New England rivers indicate that riprap sized to resist design flow events will also resist ice flows." In any event, even applying a 6-inch allowance for ice and debris, use of armor stone with a D50 of 3 inches and a D]00 of 6 inches would support an armor stone layer thickness of 12 inches, consistent with the design approved by EPA for the Upper '/•> Mile Reach.

3. Sand and Gravel Layer: The EE/CA cap design utilizes a sand and gravel layer of 6 inches as a bedding layer for the overlying erosion protection layer, to protect the underlying geotextile of the cap from damage. However, such a bedding layer is usually used only when placing rock size significantly larger than that required for armoring the 1 !/2 Mile Reach. The USDOT Design of Riprap Revetment (USDOT, 1989) states that "a 4-inch to 6-inch gravel bedding layer should be placed beneath the riprap layer for riprap gradation having D50 greater than 3.00 ft." The U.S. Army Corps of Engineers' specifications for geotextiles (USAGE, 1995) note: "Geotextile strength requirements vary with intended use and construction procedures. Experience has shown that when a heavier non-woven geotextile is used, the bedding material can often be reduced in thickness or completely eliminated." For the I'/z Mile Reach, use of available high-strength geotextile, together with use of smaller armor stone, would eliminate the need for a bedding layer.

F:\USERS\MCG1\DMNOO\1900ATTD.WPD D-2

Moreover, even if it were determined that some layer is needed to protect the underlying geotextile, a GeoGrid liner could be used in lieu of the 6-inch sand and gravel layer, thereby eliminating the need for the additional 6 inches of excavation prior to installation. EPA approved and specified the use of such a GeoGrid liner (instead of a sand and gravel layer) to protect the geotextile for the Upper !/2 Mile Reach cap. In fact, however, use in the 11/2 Mile Reach of armor stone size with a D50 of 3 inches (the appropriate revised stone size) would eliminate the need for any such protective layer. Such stone has an approximate weight of only 1 pound. With stone weight of only a few pounds or less, neither a sand and gravel layer nor GeoGrid is necessary to protect the underlying geotextile, and due to placement at the channel bottom, buoyancy factors further reduce the stress due to rock mass.

FIGURE D-1

!i*

if SJ-r

I M DISTANCE m «et A»OVE COMFLVCNCE WITH MOU*ATO«>C DIP

Figure D-1

F:\USERS\MCGl\DMNOO\l 900ATTD.WPD D-3

FIGURE D-2 - EFFECT OF SLOPE ON RIVER VELOCITY AND D-30

• A value of 1.0% for the slope represents the value assumed in the EE/CA. 1.6 • The high and low slope areas shown are actually more representative

of 1-1/2 mile reach. • The graph indicates the effect of using an over-estimated value for the

1.4 channel slope when computing velocity. • The decreased velocity then results in a greatly reduced required D30

diameter for the armor stone (DK=D, J1.2). 1.2

0)

0>

0.8

0.6

0.4 ; velocity

0.2 D-30 stone

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

slope (in percent)

FIGURE D3 - DIAMETER AND WEIGHT OF CHANNEL ARMOR STONE AS A FUNCTION OF VELOCITY

For example shown with a velocity of 8 ft/sec, D-50 approx. 3.4 inch and w-50 approx. 2.1 pounds.

= = Probable Velocity

O for Flood Flows m

4 5 6 Flow Velocity (ft/sec)

3/00 SYR-54 YCC, DJH 20192010/20192N06.CDR

References for Text and All Attachments

Chapman, P.M., and G.S. Mann. 1999. Sediment quality values (SQVs) and ecological risk assessment. Marine Pollution Bulletin 38:339-344.

EPA. 1988. Guide to Technical Resources for the Design of Land Disposal Facilities. EP A/625/6­88/018. Risk Reduction Engineering Laboratory and Center for Environmental Research Information, Office of Research and Development, Cincinnati, OH.

EPA. 1993. Technical Manual: Solid Waste Disposal Facility Criteria. EPA/530/R-93/017. USEPA, Office of Solid Waste and Emergency Response. Washington, D.C.

EPA. 1997. Ecological Risk Assessment Guidance for Superfiind. EPA-540-R-97/006. U.S. Environmental Protection Agency, Environmental Response Team, Edison, New Jersey.

EPA. 1999. Ecological Risk Assessment and Risk Management Principles for Superfund Sites. OSWER Directive 9285.7-28P. U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response, Washington, D.C.

Federal Emergency Management Agency (FEMA). 1982. Flood Insurance Study - City of Pittsfield, Massachusetts, Berkshire County.

Holtz, R.D., B.R. Christopher, R.R. Berg. 1997. Geosynthetic Engineering. Bitech Publishers.

Long, E.R., D.D. MacDonald, S.L. Smith, and F.C. Calder. 1995. Incidence of adverse biological effects within ranges of chemical concentrations in marine and estuarine sediments. Environmental Management 19:81-97.

Schulz, T.W. and Griffin, S. 1999. Estimating risk assessment exposure point concentrations when data are not normal or lognormal. Risk Analysis, Vol. 19, November.

Singh, A., A. Singh, and Max Engelhard. 1998. The Lognormal Distribution in Environmental Applications. EPA National Exposure Research Laboratory, Technical Support Center for Monitoring and Site Characterization.

Smith, S.L., D.D. MacDonald, C.G. Keenleyside, C.G. Ingersoll, and J. Field. 1996. A preliminary evaluation of sediment quality assessment for freshwater ecosystems. Journal of Great Lakes Research 22:624-638.

Swartz, R.C., and D.M. DiToro. 1997. Sediments as complex mixtures: An overview of methods to assess ecotoxicological significance. Pp. 255-269 in: Ingersoll, C.G., T. Dillon, and G.R. Biddinger (eds.), Ecological Risk Assessment of Contaminated Sediments. SET AC Press, Pensacola, Florida.

USAGE. 1991/1994. Hydraulic Design of Flood Control Channels: Engineering and Design. U.S. Army Corps of Engineers. Engineering Manual 1110-2-1601. 1 July 1991/30 June 1994.

USAGE. 1995. Guide Specifications for Construction Section 02378 - Geotextiles Used as Filters. U.S. Army Corps of Engineers. May.

USDOT. 1989. Design of Riprap Revetment. Federal Highways Administration Hydraulic Engineering Circular #11. U.S. Dept. of Transportation.

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