35 OiDuPont EngineeringBarley Mill Plaza-Bldg. 27Lancaster Pike & Rte. 141Wilmington, DE 19805

DuPont Engineering

November 29. 2000

Mr. Randy Sturgeon, 3HS23Remedial Project ManagerU.S. EPA, Region III1650 Arch StreetPhiladelphia, PA 19103-2029

SOUTH LANDFILL - SOUTH JAMES STREET CAP ASSESSMENTNewport Superfund Site, Newport, Delaware

Dear Randy,

Our assessment of the South Landfill - South James Street Cap alternatives is attached.We believe that incorporation of the existing asphalt roadway as part of the cap with a newshoulder overlapping the geosynthetic cap is the most desirable and cost-effective solution. Asdescribed in the attached report, road removal for a continuous cap installation would requiresignificant traffic interruption and extended DelDOT review.

Please contact me at (302) 992-5829 if you or your staff have any questions regarding thisassessment.

JLAipbbcc: K. Olinger, DNREC

C. Clayton, USCOEP. Welsh, DelDOTP. Meitner, Legal

Sincerely,

P.Y J'm L. Aker' Project Director

RR32l*650E I du Pont de Nemours and Company EN-3980 Rev 3/2000

DuPont Newport Superfund Site

SOUTH LANDFILL PROJECT1 SOUTH JAMES STREET ALTERNATIVES

ENGINEERING REPORT

prepared for:

DUPONT CORPORATE REMEDIATION GROUPW1LMINGTON, DELAWARE

submitted by:

URS CORPORATION

November 2000

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ENGINEERING REPORTSOUTH JAMES STREET ALTERNATIVES

SOUTH LANDFILL PROJECT

NEWPORT SUPERFUND SITE

NEWPORT, DELAWARE

Prepared for:DUPONT CORPORATE REMEDIATION GROUP

BARLEY MILL PLAZA 27

P.O. BOX 80027

WILMINGTON, DELAWARE 19880

Prepared by:

URS CORPORATION282 DELAWARE AVENUE

BUFFALO, NEW YORK 14202

(716)856-5636

SUBMITTED ELECTRONICALLY NOVEMBER 29,2000

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TABLE OF CONTENTSPage No.

1.0 INTRODUCTION.................................................................................................... 1-1

2.0 EXISTING CONDITIONS...................................................................................... 2-12.1 Site Inspection............................................................................................. 2-1

2.2 Design Drawings......................................................................................... 2-12.3 Delaware DOT Interview............................................................................ 2-2

3.0 ALTERNATIVE EVALUATION........................................................................... 3-1

3.1 Alternative 1 - Remove and Replace Existing Road................................... 3-1

3.2 Alternative 2 - Cap Over Existing Road/New Road Installation................ 3-23.3 Alternative 3 - Incorporating Existing Road as a Cap Component............ 3-2

3.4 Other Alternatives....................................................................................... 3-33.4.1 Low Permeability Soil Seal Between Asphalt and Geomembrane 3-33.4.2 Relocation of South James Street.................................................. 3-4

3.5 Conclusions and Recommendations........................................................... 3-4

FIGURES(following text)

Figure 1 Site Vicinity Plan

Figure 2 Existing Site Conditions

Figure 3 Remove and Replace South James Street - Typical Section

Figure 4 Cap Over South James Street, Construct New Roadway - Typical SectionFigure 5 Incorporating South James Street as a Cap Component- Typical Section

Figure 6 Geomembrane Overlap Detail

TABLES(following figures)

Table 1 South James Street Alternative Summary

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APPENDICES(following tables)

Appendix A Telecon Memorandum

Appendix B Cost Estimates

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1.0 INTRODUCTION

The Newport Superfund Site in Newport, Delaware encompasses approximately 120acres along the north and south sides of the Christina River. The site includes the North Landfill,

the South Landfill, adjacent wetland areas, a former ballpark, and an operations area consistingof portions of the DuPont Holly Run Plant and the Ciba Newport Plant.

The United States Environmental Protection Agency (USEPA) Region III issued a

Record of Decision (ROD) for this site, dated August 26, 1993. The ROD describes the selectedremedy for the Newport Superfund Site, of which the South Landfill project is one component.

On August 8, 1995, the USEPA issued an Explanation of Significant Differences (ESD) for the

South Landfill portion of the remedy originally called for in the ROD. Dupont presently ispreparing a submittal package to further modify the original ROD and ESD. The modificationproposal intends to provide a more innovative use of available technology, better overallprotection to human health and the environment, and a reduction in project costs.

In summary, this modification proposal will include the installation of a soil-bentonite

barrier wall along the Christina River to act as a hydraulic barrier between the landfill and the

water body and a permeable reactive barrier wall around the remaining portions of the site to

provide treatment of groundwater migrating out of the landfill. In addition, a multilayer cap

consisting of a geosynthetic layer, a protective soil layer, and a topsoil layer will be installed

over the South Landfill and appropriately designed to promote drainage. The intent of the cap isto protect human health and the environment and to minimize infiltration into the landfill,

thereby extending the useful life of the permeable reactive barrier wall.

This report focuses on one portion of the South Landfill remedy. An existing state road

traverses the South Landfill site in a north-south direction in the eastern portion of the landfill.

This road originally was constructed in the early 1970s and is referred to as South James Street(see Figure 1). Waste presently exists under and on both sides of the roadway. The ROD and

ESD indicated that a section of South James Street would be removed, and, following the

capping of the South Landfill, would be reconstructed on top of the cap. This report has been

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prepared to compare this approach to various other alternatives to determine if there is a more

cost effective, potentially less disruptive, and equally effective alternative.

The alternatives proposed focus on incorporating South James Street into the cap design

or constructing a new road on top of the cap in various configurations. The results andinterpretations of the alternative analysis will be incorporated into the development of DuPont's

submittal package noted above.

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2.0 EXISTING CONDITIONS

The existing conditions and construction layout of South James Street were evaluated byvisually inspecting current roadway conditions, reviewing historic design drawings, and

interviewing Delaware Department of Transportation (DOT) personnel.

South James Street extends from the James Street Bridge to Old Airport Road,

paralleling southbound State Route 141 (see Figure 2). Ingress to and egress from southbound

State Route 141 can be made from South James Street. Since many businesses and commutersrely on this roadway, this roadway cannot be eliminated. Approximately 1,000 linear feet of

South James Street traverses the eastern portion of the South Landfill.

2.1 Site Inspection

On November 8, 2000, a site inspection was performed on the South Landfill site and

South James Street. Based on a visual inspection, the existing roadway lanes and shoulders are

asphalt. The asphalt surface in the travel lanes is in fair condition with little deterioration.

Asphalt sealant has been applied to various cracks in the asphalt surface (travel lane andshoulder). Portions of the asphalt surface within the pavement shoulders are deteriorating and

some portions have disintegrated resulting in cracked pavement and potholes.

2.2 Design Drawings

The original design drawings for South James Street (south of the James Street Bridge)

dated 1971/72 were reviewed and evaluated against the visual inspection activities. South JamesStreet originally was referred to as an access road from Basin Road to Old Airport Road, and was

proposed to be constructed of borrow fill. This proposed construction subsequently was

modified to asphalt pavement, although no record drawings were available from the Delaware

DOT, Therefore, the actual pavement cross sections (both course thicknesses and mix types)currently are unknown. The alignment shown on the original design drawings was similar to thatidentified during the site inspection.

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2.3 Delaware DOT Interview

Delaware DOT personnel were interviewed to discuss the history of South James Street

and the proposed alternatives being evaluated. DOT personnel verified that the street originally

was planned to be a fill access road and subsequently was changed to an asphalt pavement road.

The course thicknesses and mix types of the South James Street roadway were unknown to DOT

personnel.

Based on the discussion of the alternatives being evaluated, DOT personnel noted these

concerns:

• Many businesses and commuters currently rely on this road and, therefore, the

roadway should remain active.

• Traffic disturbances should be kept to a minimum during the performance of the

South Landfill project

• The existing roadway should not be permanently removed.

• A removal and replacement alternative may involve/require public participation

Based on these considerations, DOT personnel favored incorporating the existingroadway into the proposed landfill cap. A memorandum of the telephone interview between

URS and Delaware DOT personnel is provided in Appendix A.

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3.0 ALTERNATIVE EVALUATION

Various road alternatives were compared to the ROD/ESD South James Street remedy todetermine if there are more cost effective, potentially less disruptive, and equally effective

approaches. Including the original proposal, three alternatives were evaluated in detail:

• Alternative 1 - Remove and Replace Existing Road (original proposal)

• Alternative 2 - Cap Over Existing Road/New Road Installation

• Alternative 3 - Incorporating Existing Road as a Cap Component

Other alternatives also were considered, but not in detail due to the reasons presented below.

3.1 Alternative 1 - Remove and Replace Existing Road

This alternative was the proposed remedy for South James Street in the 1993 ROD andwas maintained under the 1995 ESD. Under this alternative, a section of South James Street

would be removed and replaced on top of the proposed South Landfill cap. The cross-section of

the new roadway would be comparable in material types, course thicknesses, and vertical profile

to the existing road. A typical section of roadway for this alternative is shown in Figure 3.

For this alternative, a 1,200-linear-foot temporary bypass road would need to beconstructed east of the existing South James Street. Temporary traffic controls would need to be

implemented along this temporary roadway to maintain existing traffic flow in a reliable and safe

manner. After the temporary bypass roadway is constructed and operational, approximately

1,000 linear feet of South James Street would be removed. The subsurface barrier wall proposedto be constructed under the roadway would then be installed. The subgrade under the removed

portion of South James Street would then be over-excavated for cap placement (this would allow

the vertical profile of the new roadway to match that of the original). The landfill cap systemwould then be extended over the original location of South James Street. Following this cap

installation, a new portion of South James Street would be reconstructed on top of the cap system

along the road's previous alignment. This alternative likely would result in a cap low point,

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thereby complicating cap drainage features due to the over-excavation required for the capinstallation.

Advantages, disadvantages, and costs associated with the removal and replacement of the

South James Street roadway alternative are provided in Table 1.

3.2 Alternative 2 - Cap Over Existing Road/New Road Installation

This alternative would consist of installing a landfill cap over the existing South James

Street roadway and installing a new roadway on top of the cap. This alternative is similar toAlternative 1 except that it would not include the removal of the existing section of South James

Street. A typical section of roadway for this alternative is shown in Figure 4.

Advantages, disadvantages, and costs associated with installing a landfill cap over theexisting South James Street roadway and installing a new roadway on top of the cap are provided

in Table 1.

3.3 Alternative 3 - Incorporating Existing Road as a Cap Component

Under this alternative, the existing South James Street roadway would remain in placeand act as a portion of the landfill cap. The proposed geomembrane landfill cap would extend

only under the roadway shoulders and be discontinuous to avoid complete roadway removal and

reconstruction. In this "shingled" approach, the roadway would prevent infiltration where the

geomembrane is made discontinuous. Precipitation would drain towards the adjoining roadsidedrainage channels, away from the shoulder/geomembrane overlap. A typical section of roadway

for this alternative is shown in Figure 5.

Based on the deteriorated conditions of the roadway shoulders, a portion would be

sawcut and removed. The geomembrane component of the proposed landfill cap would then beinstalled and anchored under the location of the removed shoulders. Following the

geomembrane installation, the roadway shoulders would be replaced in-kind. A typical

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geomembrane overlap detail is provided in Figure 6. Considerations would be implemented to

maintain adequate stormwater control.

It is understood that this alternative would have a greater potential for landfill capinfiltration (e.g., future pavement cracking and incidental infiltration between geomembrane and

asphalt shoulder). However, the proposed South Landfill project remedy involves the treatment

of groundwater, not containment, and the impact to the remedy from minor infiltration through

the cap would be insignificant.

Advantages, disadvantages, and costs associated with the South James Street tie-in

alternative are provided in Table 1.

3.4 Other Alternatives

Other road alternatives that were evaluated included:

• Placing a low permeability soil seal between the asphalt and geomembrane

• Relocating South James Street elsewhere on the site

3.4.1 Low Permeability Soil Seal Between Asphalt and Geomembrane

This alternative would include the installation of a low permeability soil layer under theexisting roadway shoulder and terminating the geomembrane cap in the low permeability soil

material. The existing roadway would be upgraded as noted for Alternative 3 with the shoulderpavement being placed on the low permeability soil to provide a seal. The alternative was not

considered further because:

• Low permeability material does not provide a good road subbase, as it lends

itself to frost heave.

• The thermal expansion and contraction of the stiff geomembrane would not

guarantee a reliable seal within the low permeability soil. Thermal expansion

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AR32i»66l

and contraction could result in geomembrane liner ripples that could cause

openings in the liner at critical water flow locations (roadway subbase).

3.4.2 Relocation of South James Street

This alternative would include constructing a new section of roadway in a new alignment

over the completed landfill cap. The new section of roadway would then be tied into the

remaining South James Street pavement beyond the limits of the South Landfill cap. This

alternative has similar advantages and disadvantages to the removal and replacement alternative.

Additional disadvantages would include:

• Potential sight distance concerns

• Construction of a roadway outside the current DOT right-of-way, which would

introduce complex property acquisition/easement issues

• Technically difficult transition from the fixed South James Street Bridge to the

relocated roadway, since the transition area would be close to limits of landfill

• Increased costs based on longer roadway replacement distance

Based on these considerations, this alternative was not considered further.

3.5 Conclusions and Recommendations

Alternative 3, incorporating existing road (South James Street) as a cap component, is

the selected alternative for several reasons. First, this alternative would best address DOT's

requirement to minimize traffic disruptions during construction activities. Second, it would be as

effective as the other alternatives considering the overall remedy being implemented. Third, this

alternative would be the most readily constructed. Fourth, this is also the least expensive

alternative.

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FIGURES

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EXISTING ASPHALTSHOULDER

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STONEAGGREGATE 4DEPTH

GEOMEMBRANE

NOT TO SCALE

?| MAC* I DUPONT NEWPORT SOUTH LANDFILL , rir,IDr RGEOMEMBRANE OVERLAP DETAIL I MbUKL b

TABLES

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TABLE 1

£ET ALTERS

.ANDFILL PI

T SUPERFUI

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DISADVANTAGES

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ficult

. In

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under the road, creating stonn drainage design

concerns.

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required As a result, more

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affic flow.

The DOT indicated p

ublic participation may be

required fo

r this alternative.

This was die most ex

pensive alternative

evaluated

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This disadvantage however, is no

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AR32l*67l

APPENDIX A

TELECON MEMORANDUM

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URS Telecon Memorandum

Date: November 13, 2000

To: Files: 05-00035849.00

From: Michael Azzarella

Subject: Newport South Landfill - Telephone Conversation with Delaware DOT

Today, Rick Hody, a URS roadway designeer, and I spoke with Paul Welsh of the DelawareDepartment of Transportation (DOT) to discuss the proposed South James Street work required forthe South Landfill remedy.

Paul gave us a little background about South James Street over the South Landfill. The street wasoriginally proposed to be an access road that would be constructed with borrow materials.Presently, this road has an asphalt pavement surface and no as-builts are available for the presentroad cross section (course thicknesses and material mixes). Paul indicated that his departmentwould be willing to go out and perform core sampling (if required and with advance notice) toverify materials types and thicknesses.

Paul indicated that this road is probably a secondary or tertiary road, but many businesses andcommuters rely upon this road, especially since it has an ingress to and egress from southboundState Route 141. Paul also indicated that this road should not be permanently eliminated during theSouth Landfill capping activities.

We discussed possible alternatives for integrating the existing roadway into the cap and building anew road over the cap. Paul noted that integrating the roadway into the cap (i.e. roadway tie-in)would result in the least amount of traffic disturbance, which is a very important issue to the DOT.We indicated that this alternative would require roadway shoulder repair and cap tie-in acivities.We inquired about their requirements for this work and Paul indicated that we need to propose theconstruction activities to the DOT based on DuPont's needs to provide a suitable cap for theremedy work. Paul indicated that a tresspass agreement would need to be executed by DuPont andthe DOT to conduct work on the roadway as approved by the DOT.

When the discussion addressed the installation of a new roadway, Paul expressed his hesitation.Paul did not understand the use of the new roadway if the existing road could be incorporated intothe cap system. Paul questioned if there was area available to install a bypass road, and expressedhis concerns about the road installation in a potentially hazardous area. A bypass road would resultalso result in significant disturbances to traffic flow in this area. Paul indicated that a roadwayremove and replacement activity may also require public input.

Paul also expressed concerns about a proposal to put a new road over an old road with the capbetween. Raising the vertical profile may not be possible due to the fixed elevation and requiredapproach distances to the James Street Bridge.

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URS Page 2 of2

Based on our conversations, we feel that if the Paul had to recommend an alternative, he wouldfavor the alternative which incorporates the existing roadway into the cap design (i.e. tie-in). TheDOT is willing to work with DuPont for a solution that would be acceptable to both parties.

APPENDIX B

COST ESTIMATES

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APPENDIX B - COST ESTIMATES

SOUTH JAMES STREET ALTERNATIVES

NEWPORT SUPERFUND SITE SOUTH LANDFILL PROJECT

Cost estimates were developed for:

• Alternative 1 - Removal and replacement of a section of South James Street with

the proposed South Landfill cap system installed under the roadway

• Alternative 2 - Placing the South Landfill cap over a section of the existing

South James Street roadway followed by construction of a new section ofroadway

• Alternative 3 - Incorporating the existing South James Street roadway as a

landfill cap component.

Alternative 1 - Remove and Replace Existing Road

This cost estimate includes removing a section of South James Street, installing theproposed South Landfill cap under the location of the removed roadway, and reinstalling a

section of South James Street over the cap in the previous location. As noted in the Engineering

Report, the actual pavement cross-sections (both course thicknesses and mix types) presently are

unknown. The typical cross-section, as shown in Figure 3, was used as the basis for establishingthe cost of a new roadway to replace a portion of South James Street. The estimated cost for this

alternative is approximately $390,000.

Alternative 2 - Capping Over Existing Road/New Road Installation

This cost estimate includes constructing the proposed South Landfill cap over a sectionof the existing South James Street roadway and constructing a new section of roadway over the

cap. The estimated cost for this alternative is approximately $360,000

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Alternative 3 - Incorporating Existing Road as a Cap Component

This cost estimate includes incorporating South James Street as a landfill cap component

and repairing the existing roadway. The estimated cost for this alternative is approximately

$57,000.

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DUPONT NEWPORT SOUTH LANDFILLSOUTH JAMES STREET TIE-IN ALTERNATIVES

COST ESTIMATE

ALTERNATIVE 1REMOVE AND RECONSTRUCT NEW ROAD

LINER UNDER ROAD

DESCRITION UNIT QUANTITY UNIT TOTALCOST COST

Mobilization/Demobilization US 1 $14,744 $14,744

Temporary Road (Install & Remove) SY 3,200 $13.44 $43,008

Excavation & Disposal of Existing Road CY 6,000 $8.26 $49,560(Disposal of Materials Onsite)

Subbase Fill and Compaction CY 4,000 $15.13 $60,520

Asphallic Pavement___________- Base Course - Shoulders SY 1,950 $5.27 $10,277

- Base Course - Lane SY 3,100 $9.07 $28,117

- Binder Course - Shoulder SY 2,300 $3.57 $8,211

- Binder Course - Lane SY 2,750 $8.38 $23,045

Surveying DAY 10 $1,125 $11,250

Striping LF 3,000 $0.24 $720

Traffic Control LS 1 $37,955 $37,955

Additional Cap Installation* AC 1 $77,255 $77,255

Subtotal $364,662Contingencies - 5% $18,233Total $382,895Say $390,000

* From DuPont North Landfill Cap Cost Estimate

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DUPONT NEWPORT SOUTH LANDFILLSOUTH JAMES STREET TIE-IN ALTERNATIVES

COST ESTIMATE

ALTERNATIVE 2REMOVE AND RECONSTRUCT NEW ROAD

LINER OVER EXISTING ROAD

DESCRITION UNIT QUANTITY UNIT TOTALCOST COST

Mobilization/Demobilization LS 1 $13,092 $13,092

Temporary Road (Install & Remove) SY 3,200 $13.44 $43,008

Protective Fill Over Ext. Roadway CY 1,300 $15 $19,669

Geotextile Cushion Under Cap SY 4,950 $3 $12,375

Fill at Road Slope to Existing Grade CY 2,000 $15 $30,260

Asphaltic Pavement___________- Base Course - Shoulders SY 1,950 $5.27 $10,277

- Base Course - Lane SY 3,100 $9.07 $28,117

- Binder Course - Shoulder SY 2,300 $3.57 $8,211

- Binder Course - Lane SY 2,750 $8.38 $23,045

- Wearing Course SY 5,250 $4.23 $22,208

Surveying DAY 10 $1,125 $11,250

Striping LF 3,000 $0.24 $720

Traffic Control LS 1 $37,955 $37,955

Additional Cap Installation* AC 1 $77,255 $77,255

Subtotal $337,441Contingencies - 5% $16,872Total $354,313Say $360,000

* From DuPont North Landfill Cap Cost Estimate

AR32U679

DUPONT NEWPORT SOUTH LANDFILLSOUTH JAMES ETREET TIE-IN ALTERNATIVES

COST ESTIMATE

ALTERNATIVE 3INCORPORATE EXISTING ROAD AS A CAP COMPONENT

REPLACE SHOULDER

DESCRITION UNIT QUANTITY UNIT TOTALCOST COST

Mobilization/Demobilization LS 1 $3,500 $3.500

Shoulder Repair- shoulder sawcutting LF 2,000 $1.16 $2,320- remove shoulder, 8' width SY 900 $0.60 $540- install bedding stone, 8' width CY 30 $118 $3,540- install asphalt pavement, 2" shoulder SY 900 $3.57 $3,213

Saw Cut Pavement for Barrier Wall LF 268 $5.96 $1,597

Pavement and Base Course Removal CY 25 $65 $1,620

Stone Base Course Installation CY 15 $99 $1,481

Asphalt Pavement - 5" Total Depth SY 60 $20.94 $1,256

Liner Installation Under Shoulder SY 1,000 $6.30 $6,300

Surveying DAY 7 $1,125 $7,875

Traffic Control LS 1 $18,200 $18,200

Subtotal $51,443Contingencies -10% $5,144Total $56,587Say $57,000

Note: For shoulder replacement, sawcut, remove and replace approximately 8' (41 each side)

AR32i*680

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Bartey Mill Plaza, Building 27 flfc 3 ? jj fester Pike & Route 141 . WHmJngton. DE 19805 I