geotechnical investigation work plan for cap design ... · the gowanus canal that has identified...

Andrew Prophete Project Manager

287 Maspeth Road, Brooklyn, NY 11211 T: 718.963.5412 ■ F: 718.963.5611 ■ [email protected] ■ www.nationalgrid.com

April 24, 2012 Mr. Christos D. Tsiamis Project Manager United States Environmental Protection Agency New York Remediation Branch 290 Broadway, 20th Floor New York, NY 10007 Re: Geotechnical Investigation Work Plan for Cap Design

Gowanus Canal Superfund Site Brooklyn, New York

EPA Index No.: CERCLA-02-2010-2011 EPA ID No.: NYN000206222 Dear Mr. Tsiamis: The Gowanus Canal sediments contain or have been impacted by non-aqueous phase liquids (NAPLs) that are a complex hydrocarbon mixture including polycyclic aromatic hydrocarbons (PAHs). The NAPL contains both petrogenic and pyrogenic hydrocarbons, as well as other types of chemicals. The oil refineries, petrochemical plants, MGP facilities, fertilizer and glue factories, coal yards, and other industrial and urban discharges along the Canal are all potential sources of NAPL. These industrial land uses and discharges have likely contributed petroleum, heavy metals, pesticides, herbicides, PCBs and/or other chemicals to the sediments. Many of these compounds are the same as or difficult to distinguish from compounds also associated with former MGP operations. In support of the development of a remedial design focused on an effective, sustainable remedy, with overall containment for all sources of contaminants present in the Gowanus Canal, a number of investigative efforts are planned under the general categories as follows: Cap stability and components. In-situ solidification. Upland loading (hydraulic and chemical). Hydrodynamic modeling.

The following work plan addresses a focused geotechnical investigation of the Gowanus Canal related to potential cap stability. The USEPA recently prepared a draft Feasibility Study (FS) for the Gowanus Canal that has identified the dredging of soft sediments and the placement of a protective cap over the subgrade (native sediments) as a potential remedy. Although the shallow sediments are soft, it may also be possible to place a cap on the soft sediments, or on portions of the soft sediments rather than to fully dredge to native sediments. To this end, additional study is needed to evaluate stability of a cap on the soft and native sediments.

Geotechnical Investigation Work Plan for Cap Design Gowanus Canal Superfund Site Brooklyn, New York April 24, 2012


The purpose of this investigation is to obtain geotechnical strength parameters of the soft and native sediments for bearing capacity, slope stability, and settlement evaluations. This work plan is intended to address this data gap and will build upon USEPA’s draft FS for the canal with regard to cap design. The objective of this investigation is to perform test borings and cone penetrometer tests (CPTs) through the canal soft and native sediments to obtain information on the strength of these materials. We will summarize the data in an Investigation Findings Report. A Quality Assurance Project Plan (QAPP) has been prepared and is included as an attachment. The site-specific Health and Safety Plan (HASP) developed and previously approved will be used for field activities, and is not included with this submittal. SCOPE OF WORK The investigation will consist of three primary tasks:

Task 1 – Canal Access and Exploration Layout: Explorations will include CPTs and borings performed within the canal and will require notification of the U.S. Coast Guard.

Task 2 – Subsurface Explorations: We appreciate the potential difficulty in recovering samples from the soft sediments and have elected to include CPTs in this program. We will primarily rely on the CPTs to provide a continuous resistance profile through the sediments if soil samples cannot be collected for laboratory testing after multiple sampling attempts. Five test borings and 19 CPTs ranging from 25 to 30 feet deep will be performed from a barge at the approximate locations along the canal shown in Figures 1 through 3 and summarized in Table 1.

o CPTs provide a continuous profile of strength information and are a relatively rapid exploration technique. The CPTs can be adapted to very soft sediment conditions using a modified cone (T-Bar or spherical ball) in place of the standard cone, and allows measurement of strengths as low as 1 kiloPascal (kPa, 21 lb/ft2). We anticipate using the modified cone to evaluate the strength of very soft sediment, where encountered.

o After completion of the CPTs, the five test borings will be drilled using sonic drilling methods at selected CPT locations where soft sediments were encountered. The purpose of the borings is to obtain undisturbed Shelby Tube samples of soft sediments for laboratory testing. The final locations of test borings will depend on the CPT data and may vary from the locations shown on the attached figure.

Task 3 – Laboratory Testing: Laboratory testing of the soft and native sediments will be conducted to provide additional strength information on the sediments. Laboratory testing will include mechanical grain size distribution (ASTM D422), unit weight (ASTM D7263), moisture content (ASTM D2216), organic content (ASTM D2974), Atterberg



Limits (ASTM D4318), isotropically-consolidated undrained compression (ASTM D4767), and Incremental Consolidation (ASTM D2435).

EXPLORATION PROCEDURES The CPTs will be advanced initially using the standard cone. If sediments are found to be very soft and the standard cone is not adequate to measure the low sediment strength, an additional CPT will be advanced through the soft sediment zone using a modified cone. Test borings will be drilled after completion of the CPTs at selected CPT locations where soft sediments were encountered. The test borings will be advanced using sonic drilling techniques. Soil samples will be collected continuously and Standard Penetration Tests (SPTs) will be performed at standard 5-foot intervals in accordance with the QAPP. Soil samples will be selected for laboratory testing as a function of a visual examination of the different soil types collected from sonic core, split-spoon, and undisturbed tube samples. The soil will be classified in accordance with the Unified Soil Classification System. A photo-ionization detector (PID) will be used to screen all soil samples at 6 to 12-inch intervals at boring locations. Soils with the highest PID reading for each core (5 feet) will be collected and screened with a PID using the jar headspace method. All borings will be backfilled using a tremie pipe from the bottom to the top of the hole with a grout mixture suitable for saltwater. The mixture is intended to prevent platelet flocculation and will be proportioned as follows: 1 pint LIQUI-TROLTM, 16 pounds ZEOGEL®, 5 pounds powdered bentonite, and 40 gallons potable water. During all intrusive subsurface activities, work zone air monitoring will be conducted using a particulate meter to monitor respirable particulate matter and a multiple gas meter to monitor for total volatile organic compounds (VOCs), hydrogen cyanide, hydrogen sulfide, lower explosive limit (LEL), and percent oxygen. Exploration equipment will be decontaminated between each exploration location as described in the QAPP. Sediment cuttings and decontamination fluids will be collected in 55-gallon United States Department of Transportation (USDOT) drums, and will be disposed of by National Grid according to USEPA’s Off-Site Rule. SURVEY Horizontal coordinates will be measured using Differential Global Positioning System (DGPS) survey methods. The depth to mudline will be measured at each exploration location with an accuracy of 0.1 feet, and water level elevations at the time of the mudline sounding will be measured from surveyed tide gauges installed in the canal. Horizontal coordinates and vertical elevations will be referenced to the New York State Plane Eastern Zone of the North American



Datum of 1983 (NAD83) and the North American Vertical Datum of 1988 (NAVD88), respectively. REPORT PREPARATION The results of this investigation will be summarized in an Investigation Findings Report and will include, boring/CPT locations and logs, laboratory test results, and a summary of findings. If you have any questions or require additional information, please feel free to contact me at (718) 963-5412 or by e-mail at [email protected]. Sincerely,

Andrew Prophete Project Manager MZ/jp H:\WPROC\Project\NationalGrid\Gowanus - Confidential\WORK PLANS\2012-04-24 Geotechnical Investigation Cap Work Plan\Gowanus Canal Geotechnical IWP - Cap 042412.docx

Attachments:

Figure 1 – Cap Design, Proposed Geotech Locations, RTA 1

Figure 2 – Cap Design, Proposed Geotech Locations, RTA 2

Figure 3 – Cap Design, Proposed Geotech Locations, RTA 3A & 3B

Table 1 – Proposed Subsurface Explorations - Cap Design

QAPP

XY

XY

XY

XY

XY

XY

GC-CPT-001

GC-CPT-003

GC-CPT-005

GC-CPT-007

GC-B-001/GC-CPT-002

GC-CPT-004

GC-B-002/GC-CPT-006

GC-CPT-008

0 150 30075

SCALE, FEET

SOURCES:

1. AERIAL PHOTOGRAPH BING MAPS

© 2010 MICROSOFT CORP. AND ITS SUPPLIERS ACCESSED VIA ARCGIS ONLINE:

(http://www.arcgis.com)

J:\Projects\National_Grid\Gowanus\Remedial Design\Proposed_Locs_RTA_1_CAP.mxd

LEGEND

XY PROPOSED CPT LOCATIONS

PROPOSED BORING/CPT LOCATIONS

CAP DESIGN

PROPOSED GEOTECH

LOCATIONS RTA 1

GEOTECHNICAL WORK PLANGOWANUS CANAL

BROOKLYN, NEW YORK

April 2012 Figure 1Project 093010-5-1508

ConsultantsConsultants

XY

XY

XY

XY

XY

XY

GC-CPT-009

GC-CPT-011

GC-CPT-013

GC-CPT-015

GC-CPT-008

GC-B-003/GC-CPT-010

GC-CPT-012

GC-B-004/GC-CPT-014

0 200 400100

SCALE, FEET

SOURCES:




J:\Projects\National_Grid\Gowanus\Remedial Design\Proposed_Locs_RTA_2_CAP.mxd

LEGEND



CAP DESIGN

PROPOSED GEOTECH

LOCATIONS RTA 2


BROOKLYN, NEW YORK



XY

XY

XY

XY

GC-CPT-015

GC-CPT-017

GC-CPT-019

GC-B-005/GC-CPT-018

GC-CPT-016

0 150 30075

SCALE, FEET

SOURCES:




J:\Projects\National_Grid\Gowanus\Remedial Design\Proposed_Locs_RTA_3aand3b_CAP.mxd

LEGEND



CAP DESIGN

PROPOSED GEOTECH

LOCATIONS RTA 3A & 3B


BROOKLYN, NEW YORK



Table 1

Proposed Subsurface Explorations - Cap Design

Gowanus Canal Superfund Site

Brooklyn, New York

Grain Size Unit WeightMoisture

Content

Organic

Content

Atterberg

LimitsUUC CIUC

Incremental

Consolidation

ASTM D422 ASTM D7263 ASTM D2216 ASTM D2974 ASTM D4318 ASTM D2850 ASTM D4767 ASTM D24351 CPT GC-CPT-001 673435.1 634317.2 -22.5 25 - - - - - - - -1 Boring GC-B-001 673189.0 634151.6 -22.5 25 4 2 4 3 4 - 2 21 CPT GC-CPT-002 673189.0 634151.6 -22.5 25 - - - - - - - -1 CPT GC-CPT-003 672913.8 634058.8 -22.5 25 - - - - - - - -1 CPT GC-CPT-004 672632.8 633954.0 -22.5 25 - - - - - - - -1 CPT GC-CPT-005 672266.1 633798.1 -22.5 25 - - - - - - - -1 Boring GC-B-002 671991.4 633696.2 -22.5 25 4 2 4 3 4 - 2 21 CPT GC-CPT-006 671991.4 633696.2 -22.5 25 - - - - - - - -1 CPT GC-CPT-007 671807.0 633628.9 -22.5 25 - - - - - - - -2 CPT GC-CPT-008 671510.7 633481.6 -31.5 25 - - - - - - - -2 CPT GC-CPT-009 671501.1 633132.3 -31.5 25 - - - - - - - -2 Boring GC-B-003 671612.1 632411.2 -31.5 25 4 2 2 3 4 - 2 22 CPT GC-CPT-010 671612.1 632411.2 -31.5 25 - - - - - - - -2 CPT GC-CPT-011 671290.0 632054.4 -31.5 25 - - - - - - - -2 CPT GC-CPT-012 670990.9 631902.9 -31.5 25 - - - - - - - -2 CPT GC-CPT-013 670642.5 631629.2 -31.5 25 - - - - - - - -2 Boring GC-B-004 670307.0 631382.2 -31.5 25 4 2 4 3 4 - 2 22 CPT GC-CPT-014 670307.0 631382.2 -31.5 25 - - - - - - - -3a CPT GC-CPT-015 669739.6 631114.2 -36.0 30 - - - - - - - -3b CPT GC-CPT-016 669421.3 631077.5 -48.0 30 - - - - - - - -3b CPT GC-CPT-017 669042.1 630937.8 -48.0 30 - - - - - - - -3b Boring GC-B-005 668909.3 630522.5 -48.0 30 4 2 4 3 4 - 2 23b CPT GC-CPT-018 668914.2 630504.0 -48.0 30 - - - - - - - -3b CPT GC-CPT-019 668526.9 630379.8 -48.0 30 - - - - - - - -

Note: B.O.E = Bottom of Exploration

Estimated Number of Laboratory Tests

Proposed

Depth

(feet)

Target B.O.E

Elevation

(10 feet below

Dredge)

(feet)

RTAExploration

TypeNorthing EastingExploration ID

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