Final Remedial Design Work Plan Carroll Gardens/Public Place Final Remedial Design Work Plan... ·...

Final Remedial Design Work Plan

Carroll Gardens/Public Place Brooklyn, New York VCA Index No. A2-0460-0502 Site No. V00360-2 Submitted to: Submitted by: KeySpan Corporation GEI Consultants, Inc. One MetroTech Center 1 Greenwood Avenue, Suite 210 Brooklyn, NY 11201-3850 Montclair, New Jersey, 973-509-9650 September 12, 2007 061140-19-2801

Michael D. Zukauskas, P.E. Project Manager

D R A F T R E M E D I A L D E S I G N W O R K P L A N C A R R O L L G A R D E N S / P U B L I C P L A C E K E Y S P A N C O R P O R A T I O N S E P T E M B E R 1 2 , 2 0 0 7

i

Table of Contents

Abbreviations and Acronyms iv

Introduction 1

1. Remedial Investigation Summary 2 1.1 Site Description 2 1.2 Site History 3 1.3 Site Geology 3 1.4 Site Hydrogeology 3 1.5 Previous Investigations 4 1.6 Remedial Investigation Findings 5

1.6.1 Summary of Nature and Extent 5 1.6.2 Summary of Risk Characterization 6

2. Standards, Criteria and Guidance 8 2.1 Remedial Goals 8 2.2 Remedial Action Objectives 8

3. Common Remedial Elements 10 3.1 Common Pre-Design Activities 10

3.1.1 Boundary and Topographic Survey 10 3.1.2 Subsurface Utility Location Survey 10 3.1.3 Noise and Vibration Survey 11

3.2 Common Remedial Technologies 12 3.2.1 Air Monitoring 12 3.2.2 Odor Control/Vapor Management 12 3.2.3 Remediation Derived Waste Management 12 3.2.4 Approved Backfill Materials Management 13 3.2.5 Material Transportation Routes 13

4. Parcel I Remedial Design Approach 14 4.1 Parcel I Conceptual Remedy 14 4.2 Pre-Remedial Design Activities 14

4.2.1 Geotechnical Investigation 14 4.2.2 DNAPL Recovery Well Installation and Pilot Study 15 4.2.3 Data Report 16

4.3 Remedial Design Approach 16 4.3.1 Remedial Design Documents (50%-75% Design) 16 4.3.2 Remedial Design Documents (95% Design) 17 4.3.3 Remedial Design Documents (Final Design) 17


ii

4.4 Remedial Technologies 18 4.4.1 Excavation and Shoring 18 4.4.2 Dense Non-Aqueous Phase Liquid Recovery 19

4.5 Engineering and Institutional Controls 19

5. Parcels II & III Remedial Design Approach 20 5.1 Parcels II & III Conceptual Remedy 20 5.2 Pre-Remedial Design Activities 21

5.2.1 Geotechnical Investigation 21 5.2.2 Supplemental Hydrogeologic Assessment 22 5.2.3 Hydraulic Modeling 23 5.2.4 DNAPL Recovery Well Installation and Pilot Study 24 5.2.5 Supplemental Remedial Investigations 25 5.2.6 Subsurface Obstruction Identification 25 5.2.7 Additional Pilot/Treatability Studies 25 5.2.8 Data Report 26

5.3 Remedial Design Approach 26 5.3.1 Remedial Design Documents (50%-75% Design) 26 5.3.2 Remedial Design Documents (95% Design) 27 5.3.3 Remedial Design Documents (Final Design) 27

5.4 Remedial Technologies 28 5.4.1 Excavation and Shoring 28 5.4.2 Subsurface Containment Barrier Wall 29 5.4.3 In-Situ Groundwater Treatment 29 5.4.4 Dense Non-Aqueous Phase Liquid Recovery 30


6. Parcel IV Interim Remedial Measure 31 6.1 Parcel IV Conceptual Remedy 31 6.2 Pre-Interim Remedial Measure Activities 31

6.2.1 Geotechnical Investigation 31 6.2.2 In-Situ Pre-Characterization 32 6.2.3 Data Report 32

6.3 Interim Remedial Measure Approach 33 6.3.1 Draft Interim Remedial Measure Work Plan 33 6.3.2 Final Interim Remedial Measure Work Plan 33

6.4 Remedial Technologies 34 6.4.1 Excavation and Shoring 34


7. Quality Assurance Project Plan 36

8. Permits 37

9. Operations, Monitoring, and Maintenance Plan Outline 39


iii

Table of Contents (cont.) Tables

1. Surface Soil Analytical Results 2. Subsurface Soil Analytical Results 3. Groundwater Analytical Results 4. Sub Slab Soil Vapor Analytical Results 5. Soil Vapor Analytical Results 6. Tar Samples Analytical Results 7. Analytical Data Statistical Summary 8. Summary of Detections (Historical Results)

Figures

1. Site Location Map 2. Site Topography and Surface Flow Paths 3. Lateral Extent of Onsite Impacted Soils 4. Parcel I Conceptual Remedial Action Limits 5. Parcels II & III Conceptual Remedial Action Limits 6. Parcel IV Conceptual IRM Limits

Plates

1. Site Plan, GEI Sample Locations, Previous Sample Locations and Historic Structures 2. Cross sections A-A′ and B-B′ 3. High and Low Tide Shallow, Intermediate, and Deep Aquifer Groundwater Contours

– April 4, 2005 Appendix

A. Quality Assurance Project Plan H:\WPROC\Project\KEYSPAN\Citizen's Gas\RDWP\DRAFT RDWP 060807.doc


iv

Abbreviations and Acronyms

BTEX Benzene, Toluene, Ethylbenzene, Xylene BUG Brooklyn Union Gas CAMP Community Air-Monitoring Plan COCs Contaminants Of Concern CPT Cone Penetration Test DNAPL Dense Non-Aqueous Phase Liquid ELAP Environmental Laboratory Accreditation Program EPA United States Environmental Protection Agency FWRIA Fish and Wildlife Resource Impact Analysis GEI GEI Consultants, Inc. HASP Health and Safety Plan KEYSPAN Keyspan Corporation LIDAR Light Detection and Ranging LNAPL Light Non-Aqueous Phase Liquid MGP Manufactured Gas Plant MTA Metropolitan Transportation Authority NAPL Non-aqueous Phase Liquids NAVD North American Vertical Datum NYC New York City NYSDEC New York State Department of Environmental Conservation NYSDOH New York State Department of Health NYSDOT New York State Department of Transportation OM&M Operation Monitoring Maintenance Plan OSHA Occupational Safety & Health Administration PAH Polycyclic Aromatic Hydrocarbon PCB Polychlorinated Biphenyl PEL Permissable Exposure Limits POTW Publicly Owned Treatment Works PVC Polyvinyl chloride QHHEA Qualitative Human Health Exposure Assessment QAPP Quality Assurance Project Plan RAA Remedial Alternatives Analysis RAO Remedial Action Objectives RI Remedial Investigation RDWP Remedial Design Work Plan SCGs Standards, Criteria, and Guidance SMP Site Management Plan SVOC Semivolatile Organic Compound TAL Target Analyte List TAGM Technical and Administrative Guidance Memorandum VCA Voluntary Cleanup Agreement VOC Volatile Organic Compound


1

Introduction

On behalf of KeySpan Corporation (KeySpan), GEI Consultants, Inc. (GEI) has prepared this Remedial Design Work Plan (RDWP) for the former Citizens Gas Works manufactured gas plant (MGP) site located at the intersection of Smith and Fifth Streets in the Carroll Gardens/Public Place neighborhood of Brooklyn, Kings County, New York. The RDWP was prepared in accordance with the Voluntary Cleanup Agreement (VCA) for the site (Index No. A2-0460-0502) following the requirements outlined in the New York State Department of Environmental Conservation (NYSDEC) DER-10. A Remedial Alternatives Analysis Report (RAA). was submitted to NYSDEC on March 22, 2007. The RAA was approved by NYSDEC on April 23, 2007. The RDWP details investigations to be performed and documents to be prepared in development of the Remedial Design for the approved remedy. Section 1 of this RDWP presents a summary of the site Remedial Investigation (RI), in which data were collected in support of the remedial design. Section 2 presents the remedial objectives for the site and Sections 3 through 7 present the proposed approach to the remedial design for each parcel of the site. Sections 8 and 9 present a Quality Assurance Project Plan (QAPP) and an outline for the Operation, Monitoring and Maintenance Plan (OM&M).


2

1. Remedial Investigation Summary

GEI conducted a Remedial Investigation (RI) for the Site between April 2003 and June 2005. The results of the RI were presented in GEI’s Final RI report dated October 2005, which was approved by the NYSDEC on December 1, 2005. The RI included surface soil, subsurface soil, and groundwater investigations and evaluation of potential risks posed to human and ecological receptors. The remedial investigation addressed the following objectives:

Evaluate the potential presence of MGP-related contaminants in the subsurface Evaluate the extent and possible mobility of Non-aqueous Phase Liquids (NAPL) Assess the extent of off-site migration of site contaminants Evaluate site hydrogeology Assess the potential risk of exposure to contaminants posed to users of the site Assess the potential affects on fish and wildlife resources

During investigations prior to the RI, site contaminants of concern had been identified as tar-related constituents including polycyclic aromatic hydrocarbons (PAHs), benzene, toluene, ethylbenzene, and xylene (BTEX), and dense nonaqueous phase liquid (DNAPL). The RI findings were used to develop remedial objectives and approaches to remedial design as presented in this RDWP. The remainder of this section summarizes the findings of the RI.

1.1 Site Description The former MGP property is located in a densely developed urban area of commercial, industrial, and residential land uses and abuts the Gowanus Canal to the east and southeast (Figure 1). The site is comprised of four parcels:

Parcel I: Vacant lot that formerly housed the majority of the former MGP Parcel II: Active concrete plant Parcel III: Active distribution warehouse Parcel IV: Active truck maintenance facility and commercial truck lot

The four parcels encompass approximately 11.5 acres (Plate 1). Parcels I – IV are fenced and gated. The Gowanus Canal abuts the site to the east and southeast along Parcels III and IV. Gowanus Bay is located approximately 5,200 feet to the southeast of the site and New York Harbor is located approximately 6,400 feet to the west of the site. Elevated Metropolitan Transportation Authority (MTA) train tracks exist south and west of the site across


3

Huntington and Smith Streets, respectively. Detailed descriptions of the parcels are provided in Subsection 1.2.1 of the RI report. Groundwater is not used at any of the four parcels and there are no public or private water supply wells within a 3-mile radius of the property.

1.2 Site History The site and surrounding area were originally a wetland adjacent to Gowanus Creek. The area was filled as part of the construction of the Gowanus Canal in the 1860s. Soon after the completion of the canal, the Citizens Gas Company constructed a coal gasification plant on Parcels I and II, which was ultimately expanded to include each of the four parcels. Brooklyn Union Gas (BUG), a predecessor company of KeySpan, acquired the site in 1895. The plant was converted to an oil gasification plant in 1952 and operated as such until its closure in the early 1960s. BUG sold the MGP properties in 1969 and has not had control of the parcels since that time. Historical structures are shown on Plate 1. Detailed descriptions of site history are provided in Subsection 1.2.2 of the RI report. Recent fill located in the central part of Parcel I may be associated with operation of the concrete plant on Parcel II and illegal dumping, including drums (shown on Figure 2 as the Concrete Wash and Debris Field). The owner of Parcel I, the City of New York, is aware of and responsible for these materials and conducted an investigation within the area of illegal dumping which concluded that there are no environmental conditions associated with drums encountered within the excavation. However, a number of drums were identified outside the excavation area.

1.3 Site Geology Six major stratigraphic units, in order of increasing depth, were identified at the site: (1) fill, (2) alluvial/marsh deposits, (3) glacial deposits, (4) Gardiner’s Clay, (5) Jameco Gravel, and (6) Fordam Gneiss (Plate 2). Site contaminants have been observed or detected in all unconsolidated units but are at minimal or insignificant concentrations in the Gardiner’s Clay and Jameco Gravel. The Fordam Gneiss was not investigated. Detailed descriptions of site geology are provided in Subsection 3.1 of the RI report.

1.4 Site Hydrogeology The site is located in a coastal drainage area. Surface topography slopes downward to the south and southeast, toward the Gowanus Canal. Topographic elevations range from approximately 30 feet North American Vertical Datum (NAVD) along Smith Street to 10 feet NAVD along the Gowanus Canal. Stormwater runoff generally drains to the south and east from the site (Figure 2). Parcel I is covered with debris and generally allows infiltration; whereas, Parcels II, III, and IV are covered by asphalt or concrete and existing structures.


4

Groundwater at the site is present in a shallow unconfined aquifer (Upper Glacial Aquifer), and a confined/semi-confined aquifer (Jameco Aquifer). The Upper Glacial Aquifer has been subdivided into shallow, intermediate, and deep groundwater zones to evaluate the relationships between potentially different flow regimes within the aquifer. Depth to shallow groundwater ranges from 5 to 30 feet below ground surface (deeper in areas of higher surface elevation). The shallow unconfined aquifer is mounded in the eastern portions of Parcel I, potentially due to perched water related to buried structures and utilities and/or a shallow silt lens. Shallow groundwater at the site flows radially from the mound area (Plate 3). Underground utilities or structures may influence shallow groundwater flow. Shallow groundwater is believed to discharge to the Gowanus Canal. Intermediate and deep groundwater flow is generally toward the southwest, and is expected to ultimately discharge into Upper New York Bay. Portions of the Jameco Gravel are confined by the overlying Gardiner’s Clay; however, beneath a portion of Parcel I, the Gardiner’s Clay is absent. Measured hydraulic pressures caused by semi-confining conditions in the Jameco Gravel appear to be causing upward groundwater flow from the Jameco to the overlying deep portion of the Upper Glacial Aquifer. In these areas, the deep groundwater zone and the Jameco Aquifer are interconnected. Tidal study data indicated up to a 5-foot tidal fluctuation in shallow groundwater adjacent to the canal, and less than 1-foot fluctuations deeper and further inland. As shown on Plate 3, groundwater flow patterns do not appear to vary significantly between low and high tide. There may be a localized reverse gradient during high tide near the canal. Detailed descriptions of the site hydrogeology are provided in Section 3.2 of the RI report.

1.5 Previous Investigations Previous environmental investigations are documented in the following reports: Environmental and Engineering Study, Assessing the Suitability of the Gowanus Canal Site for

Public Housing and Recreational Usage, Stone & Webster Engineering Corporation, December 1984

Final Report, Vacant Property Site Assessment, Carroll Gardens, Brooklyn, TRC Environmental Consultants, Inc., October 1985

Engineering Investigation at Inactive Hazardous Waste Sites, Phase I Investigations, Carroll Gardens, Site No: 224012, Borough of Brooklyn, Kings County, Final –June 1987, EA Science and Technology, 1987

Engineering Investigation at Inactive Hazardous Waste Sites, Phase II Investigations, Carroll Gardens, Site No: 224012, Borough of Brooklyn, Kings County, Final –September 1990, Roux Associates, Inc., 1990.


5

Approximate sample locations from previous investigations are shown on Plate 1. Data from the above reports were included in the RI Report.

1.6 Remedial Investigation Findings The RI has addressed the objectives outlined in Section 1 with the exception of offsite contaminant delineation in some locations due to access concerns, as described further below. The vertical extent of tar migration on Parcels I, II, III, and IV has been defined. The deepest observed extent of tar-related impacts was approximately 153 feet below the ground surface.

1.6.1 Summary of Nature and Extent

In the unsaturated soil (elevation 30 ft to –2 ft NAVD), the extent of separate-phase tar is limited to the area adjacent to Holder No. 2 on Parcel I. In shallow zone soil (elevation 16 ft to –24 ft NAVD), tar-saturated soil was observed at Holder No. 3 on Parcel I, and at the northwest and northeast corners of Parcel II. The lateral extent of residual tar (blebs, lenses, grain coatings) in the shallow zone covers much of Parcel I, the western half of Parcel II, and the eastern half of Parcel III. Tar appears to have originated from tar-handling and process areas and migrated downward through the fill and alluvial deposits, until it encountered the glacial till and clay lenses. The DNAPL tar then migrated laterally east and southeast along the top of glacial till and clay lenses. Where the glacial till and clay lenses are absent, the tar continued to migrate downward until the front stagnated. In the intermediate zone soils (elevation –11 ft to –90 ft NAVD), zones of tar-saturation are present throughout the northeastern portion of Parcel I, throughout nearly all of Parcel II, in the southeastern portion of Parcel III, and on Lots 50 and 138 across the Gowanus Canal. The only tar impacts observed in the deep soil zone (elevation –90 ft to –135 ft NAVD) were at the eastern property line of Parcel I. The RI identified tar-saturated soil at depths below the floor of the Gowanus Canal (elevation –11 ft NAVD) but not adjacent to the canal above the floor elevation. The lateral extent of tar migration has been defined on the western side of Parcels I and III (Smith Street), along the north side of Parcel II, along the northwest, northeast, and southeast sides of Parcel IV, and along the northern side of Parcel I (5th Street) except for a finger of tar that appears to have migrated to the southern corner of Parcel IV as shown in Figure 3. Finally, inter-bedded tar was identified to the east-northeast of Parcel II, beneath Bond Street. Five borings proposed for the RI assessment of the extent of off-site contaminant migration have not been completed due to accessibility, right-of-entry, and utility concerns. The eastern and southeastern extent of tar migration from Lots 50 and 138 has not been defined due to the lack of private property access. The interconnection, if any, between the tar located on Parcels II and III and Lots 50 and 138 has not been


6

determined. The southern extent of inter-bedded tar to residual tar from Parcel III, beneath Huntington Street has not been defined due to the lack of private property access. Measurable DNAPL was observed in some monitoring wells on Parcels I, II, and III ranging in thickness from approximately 3.5 to 40 feet. DNAPL was removed from six monitoring wells and the DNAPL recovery rate was measured (Table 7); however, in one well, no drawdown of tar was observed. The potentially mobile tar appears to be perched on low-permeability lenses within the glacial deposits. DNAPL samples collected from the areas of Huntington Avenue and Parcel III were found to have higher viscosity, higher ignitability temperature, and lower BTEX content than tar observed on Parcels I and II. The RI included analytical testing of soil (surface and subsurface), groundwater, and soil vapor for contaminants of concern. The areal distribution of detected site contaminants was consistent with observed contamination described above. Tables 1 through 6 summarize the laboratory analytical results for surface soil, subsurface soil, groundwater, sub slab soil vapor, soil vapor, and DNAPL samples, respectively. Table 7 presents a statistical summary of the analyses performed for each media. For a detailed discussion of analytical results, please refer to Section 4 of the RI report. Based on the distribution of tar and the groundwater flow directions, dissolved phase BTEX and light-end PAHs (e.g., naphthalene) are being transported by groundwater flow into and possibly beneath the Gowanus Canal. Contaminants in soil are expected to dissolve into the groundwater and be transported with groundwater flow as described in Section 1.4. Dissolved phase contaminants that enter the canal will likely be mitigated by processes of biodegradation, volatilization, and dilution. Dissolved phase BTEX and light-end PAHs may migrate to the west and north of the site in the shallow groundwater zone. Dissolved phase contaminants in the intermediate and deep zones will likely migrate to the southwest of the site, although deep groundwater impacts are anticipated to be minimal.

1.6.2 Summary of Risk Characterization

A Qualitative Human Health Exposure Assessment QHHEA of contaminants of concern (COCs) in all media (soil, groundwater, soil vapor) at the site determined that current users of each parcel have a very low potential to be exposed to COCs in excess of the screening values. Only New York City (NYC) employees and possible trespassers at Parcel I may contact COCs in surface soils during routine and intermittent activities on that parcel. Utility and construction workers may be exposed to COCs in subsurface soils and/or shallow groundwater in the course of performing utility repairs or construction projects at all parcels, should such activity occur. While the results of the screening indicated benzene concentrations in soil gas that may impact indoor air at Parcel III, the resulting indoor air concentration of benzene from the infiltration of soil gas would likely be much lower than current Occupational Safety and Health Administration Permissible Exposure Limits (OSHA PEL).


7

Soil gas toluene concentrations above screening criteria to ambient air are also not considered to be of concern for Parcel I. A Step I Fish and Wildlife Resource Impact Analysis (FWRIA) indicated that the habitat observed on site provides limited value to mammalian and avian wildlife species, and additional habitat occurring in the 2-mile project area and vicinity provides substantially greater habitat availability. Most of the wildlife species utilizing the site are transient, highly mobile populations, and a significant negative impact is not expected. Aquatic life occurring within the Gowanus Canal are species tolerant of pollution and high levels of nutrients. A Step II-B FWIRA was performed for the aquatic resources in the Gowanus Canal. Fish survivability was chosen as the most relevant assessment endpoint in determining potential ecological impact. The results indicate that the site has a de minimus contribution to the anoxic conditions (dissolved oxygen was determined to be the most relevant measurement endpoint) in the canal and so does not impact fish survivability.


8

2. Standards, Criteria and Guidance

The following site-specific Remedial Goals and Remedial Action Objectives (RAOs) were proposed as the site specific Standards, Criteria and Guidances (SCGs) in the March 22, 2007 Remedial Alternatives Analysis Report which was approved by NYSDEC on April 23, 2007. The proposed remedy for the site will be developed to meet these SCGs.

2.1 Remedial Goals The NYSDEC’s Draft DER-10 Technical Guidance for Site Investigation and Remediation – Section 4.1(b) puts forth the following remedial goals for the voluntary cleanup program:

A remedy shall be protective of public health and the environment, given the intended use of the site

Where an identifiable source of contamination exists at a site, it should be removed or mitigated, to the extent feasible, regardless of presumed risk or intended use of the site.

These two goals are the Remedial Goals that will be applied to the site as the site-specific SCGs, in accordance with DER-10 Section 4.1 Paragraph e2, 6 NYCRR § 375-1.8(f)(2), and TAGM 4030, for determining success of the final remedy.

2.2 Remedial Action Objectives RAOs are medium-specific or operable-unit specific objectives for the protection of human health and the environment. RAOs are developed based on contaminant-specific SCGs to the extent practicable in a cost-effective manner. The RAOs are presented below. GROUNDWATER

Prevent, to the extent practicable, contact with, or ingestion of contaminated groundwater associated with the site.

Prevent, to the extent practicable, the migration of contaminated groundwater from the site. Remove, to the extent practicable, the source of groundwater contamination.

SOIL

Prevent, to the extent practicable, ingestion/direct contact with contaminated soil. Recover, to the extent practicable, DNAPL tar at the site.


9

INDOOR AIR

Prevent, to the extent practicable, inhalation of contaminants volatilizing from soil or groundwater into closed structures.


10

3. Common Remedial Elements

The approved remedy for the Carroll Gardens/Public Place site consists of the excavation of MGP-impacted soil and MGP-related subsurface structures to a prescribed depth throughout Parcels I through IV, the installation of a barrier wall along the Gowanus Canal on Parcels II and III, and the installation of DNAPL collection points at various locations throughout Parcels I, II and III. These elements are discussed in detail in Sections 4, 5 and 6. However, it is expected that present-use access limitations will cause the remediation of the site to take place in three distinct remedial efforts: Parcel I, Parcels II and III, and Parcel IV. Moreover, although each of these parcels may be remediated separately, there are several common aspects to all of the remedial efforts that will be undertaken at the site. These include pre-design activities that are common to all parcels (and best conducted concurrently) and remedial technologies that will be used at all four Parcels. These common elements are discussed below.

3.1 Common Pre-Design Activities Common pre-design activities include a boundary and topographic survey, a subsurface utility location survey, and a noise and vibration survey.

3.1.1 Boundary and Topographic Survey

A boundary and topographic survey will be prepared for the site and adjacent roads, buildings and the Gowanus Canal. The topographic survey will likely be conducted using Aerial Light Detection and Ranging (LIDAR) methods. LIDAR data are collected with aircraft-mounted lasers capable of recording elevation measurements at a rate of 2,000 to 5,000 pulses per second with a vertical precision of 15 centimeters (6 inches). During this flight, aerial photographs will also be obtained. The topographic survey will be referenced to site control points. Classical air-photo topographic methods or ground survey methods may also be in conjunction with or used as a satisfactory alternative to LIDAR. A boundary survey will be performed to locate property lines. Prior to arriving on the site, a title search will be performed to research any easements on the properties. This survey will be used to develop a base map for the remedial construction drawings. The existing explorations and historical structures will be overlaid on the new base map.

3.1.2 Subsurface Utility Location Survey

A review of available historical utility records for the four Parcels and adjacent streets will be conducted. This will include a review of plans from local private utility companies, Keyspan, and New York City municipal utilities (water, sewer, etc.) as well as applicable county and/or state


11

records. After the records review is complete, KeySpan will attempt to locate on-site utilities using ground penetrating radar. The condition of the on-site 72-inch brick sewer will impact the constructability of the barrier wall and possibly the excavation approach. Details regarding the location and condition of this sewer will be critical to design decisions. A utility markout will be called into the New York City One Call center for the adjacent streets. KeySpan will confirm the location of these off-site utilities marked on adjacent streets using ground penetrating radar or other geophysical methods. Once the utilities are located, KeySpan will survey the horizontal and, (where possible) vertical location of each utility. Site conditions may prevent the location of all utilities without direct excavation. If the location is critical to design activities, then a direct excavation of the utility may be conducted. If the location and condition are not critical to design, then the direct excavation will be deferred to the pre-remedial activities conducted by the contractor to assess and protect adjacent utilities.

3.1.3 Noise and Vibration Survey

A survey will be conducted at the site to measure background noise and vibration levels. The background noise and vibration data will be used to determine if noise and vibration mitigation measures are needed during construction to comply with the New York City Noise Code and other noise and vibration guidelines. Background noise levels will be measured at nearby noise-sensitive receptors (residences). The measurements may be made during two different seasons at the same locations, if required. Background vibration levels will be measured at nearby vibration-sensitive receivers (residences and elevated subway). These data will be used to determine the ground vibration transfer mobility at the site.

The contractor will be required to develop a Noise Mitigation Plan in accordance with §24-219 of the New York City Noise Code. The plan will be posted at the site in accordance with the Rules of the City of New York (RCNY) Title 15 §28-100.

The ground vibration transfer mobility determined during the vibration study will be used to determine areas where pre-construction structural surveys of surrounding buildings will be required. One this area is established, property owners will be contacted to negotiate access for the pre-construction surveys and, if available, structural plans will be obtained from the property owners or the New York City Department of Buildings. The Contractor will be required to conduct the pre-construction survey which will include the following.

A photo/video-documentation of pre-construction conditions of each will be conducted.

The locations of cracks or fractures will be identified, documented, measured, evaluated and the crack gauges installed, if necessary.

Deformation monitoring points will be established, where necessary.


12

The Contractor will be required to provide a report of the pre-construction survey results stamped and sealed by a New York State licensed Professional Engineer(P.E.). Based on the results of the pre-construction survey, a monitoring plan will be established and implemented during construction which may include continuous vibration monitoring, periodic measurements of crack gauges and deformation monitoring points, and a mitigation plan to prevent damage to surrounding structures.

3.2 Common Remedial Technologies Common remedial technologies include perimeter air monitoring, odor control/vapor management, and materials management.

3.2.1 Air Monitoring

Air monitoring consisting of fixed air monitoring stations around the project perimeter and roving monitoring within the workspace will be performed to meet the requirements of the New York State Department of Health (NYSDOH) Community Air Monitoring Plan (CAMP). Preparation of the site specific CAMP will be conducted during the remedial design. Action limits will be established for Volitile Organic Compounds (VOCs), respirable particulates, and odor. The CAMP will be submitted with the 50-75% Remedial Design Documents to NYSDEC for review and approval.

3.2.2 Odor Control/Vapor Management

Odor control and vapor management technologies and processes will be evaluated to mitigate or eliminate potential odors during excavation activities. Technologies considered to mitigate odors and/or control vapors will include the use of foams, water, tarps/poly covers, clean fill covers, vapor absorption equipment or temporary structures. Any odor control/vapor management technologies identified for use at the site will be presented in the Remedial Design Documents.

3.2.3 Remediation Derived Waste Management

All remediation-derived wastes will be properly managed, characterized and disposed of at off-site disposal facilities permitted and licensed to accept the various types of wastes. Anticipated waste streams include impacted soils, concrete and other construction debris, DNAPL from the recovery wells/system, personal protective equipment and debris. The remedial excavations will likely be performed in phases due to the relatively large quantity of soil to be excavated, the areal extent of excavation on Parcels I, II, and III, and the limited stockpile and laydown areas at Parcel IV. Materials may be direct loaded for off-site disposal in some areas of the site or stockpiled in designated temporary locations for sampling and analysis. Temporary staging areas for stockpiles will be constructed with liners and drainage to prevent cross-contamination and control runoff. At a minimum, all stockpiled material designated for disposal will be covered with plastic for dust and odor control.


13

Remnant structures from the remedial excavation that are determined to be inappropriate for excavation backfill material will be disposed off site after cleaning and decontamination, if necessary. This material is anticipated to be disposed of at a construction and demolition material landfill. Most excavated soils will likely be disposed of at a non-hazardous waste landfill and/or a thermal desorption facility. Tar-saturated soil will be identified upon excavation, segregated, and managed separately from other excavated soils. Soil meeting the criteria acceptable for reuse as excavation backfill will be segregated and stockpiled on site for that purpose.

3.2.4 Approved Backfill Materials Management

Imported clean fill will be obtained from either a virgin New York State Department of Transportation (NYSDOT)-approved borrow source or other KeySpan-approved source(s) identified during the design process. Representative confirmatory samples will be collected from each off-site backfill material source at a rate of one per every 1,000 cubic yards. The samples will be analyzed at a NYSDOH-certified Environmental Laboratory Accreditation Program (ELAP)-approved laboratory for total PAHs and total VOCs. In addition, ten (10) percent of the samples collected will be analyzed for Target Analyte List (TAL) parameters and polychlorinated biphenyls (PCBs).

3.2.5 Material Transportation Routes

Specific truck transport routes will be established during the design phase of the project in conjunction with the remediation contractor(s). Proposed routes will be discussed with local officials in order to minimize impacts to local roadways. A Traffic Analysis may be required to optimize the truck transport routes and minimize impacts to the local community.


14

4. Parcel I Remedial Design Approach

4.1 Parcel I Conceptual Remedy Following the removal by the City of New York of the surface debris and concrete wash located on Parcel I, the conceptual remedy for Parcel I will include the excavation of unsaturated soils to a maximum depth of eight feet below the existing street grade. Where accessible, subsurface MGP-era structures and their contents will be removed. This potentially includes the removal of three gas holders, a purifier house, and gas house foundations observed during the Remedial Investigation. The localized deeper excavation at the location of the former holders may be used to create a clean utility corridor to support site redevelopment. The clean utility corridor would extend from Smith Street to the center of the parcel, parallel to 5th Street. A visible excavation barrier will be installed to demarcate the limits of the excavation performed during the remediation and to prevent inadvertent future disturbance of deeper impacted soils. MGP-impacted excavated soils will be transported off site for treatment and/or disposal at an appropriately permitted facility. Uncontaminated soil and uncontaminated masonry debris from the subsurface structures may be returned to the excavation as backfill. The excavation will be brought to final grade using clean backfill meeting NYSDEC requirements. The final grade of the site will match the existing grade of the adjacent streets and properties. A DNAPL recovery system will be designed and installed to address recoverable product. Recovered DNAPL will be collected and transported off site to an appropriately permitted facility for disposal/treatment.

4.2 Pre-Remedial Design Activities The following sections detail the pre-remedial design activities to be performed at Parcel I of the site. The purpose of the pre-remedial design activities is to obtain supplemental site information necessary for the completion of the design of the Parcel I remedy.

4.2.1 Geotechnical Investigation

An investigation will be conducted to acquire geotechnical data through the installation of soil borings, the collection of soil samples and the performance of various field and laboratory testing. The data collected will support the design and construction of the excavation shoring systems to support the excavations on Parcel I.


15

The geotechnical investigation will include the installation of twenty soil borings along the proposed excavation support system alignment at the perimeter of the Parcel I excavation. The general area of the borings coincides with potential shoring alignments (Section 4.4.1) and are depicted on Figure 4. Eight to twelve of the soil borings will be advanced utilizing either hollow-stem auger or mud-rotary drilling methodologies to estimated depths of 40 to 50 feet below ground surface. Standard penetration tests will be performed in each boring. Split barrel samples will be obtained continuously in urban fill materials and at 5-foot intervals in native deposits. If encountered, organic and fine-grained soil will be sampled using a thin-walled sampler. Index tests consisting of grain-size analysis, organic content, Atterberg Limits and moisture content testing will be performed on soil samples. The test borings will be tremie grouted to grade using a Portland cement/bentonite slurry mixture. Eight to twelve cone penetration tests (CPTs) will be performed. Cone penetrometer probes will be advanced to estimated depths of 40 to 50 feet below ground surface. Cone data (tip, skin friction, and water pressure) will be obtained at 5-centimeter intervals from the cone penetrometer probes. The CPTs will be used to evaluate subsurface stratification, soil type, soil density, in-situ stress conditions and shear strength parameters. It is not anticipated that MGP-related impacts will be observed in borings outside of the extent of impacts observed in the RI. If impacted material is observed in the borings, a select number of samples may be collected and submitted to a ELAP-certified laboratory for VOCs via USEPA Method 8260 and semivolatile organic compounds (SVOCs) via USEPA Method 8270. All work will be performed in accordance with the NYSDEC-Approved Health and Safety Plan (HASP) and a QAPP meeting NYSDEC requirements.

4.2.2 DNAPL Recovery Well Installation and Pilot Study

Due to the nature of the DNAPL observed at this site, the PVC monitoring wells installed during the Remedial Investigation had degraded and any monitoring wells that were screened through or within the DNAPL were abandoned to prevent horizontal migration of DNAPL. Therefore, four stainless steel monitoring wells will be installed at Parcel I. The wells will be six inches in diameter, screened in DNAPL zones to depths of no greater than 75 feet below grade, and completed with a two-foot sump at the bottom of each well. The wells will be used to study DNAPL recovery for potential active remediation. The wells will be located in the vicinity of the RI monitoring wells CGMW-02I, CGMW-03S, and CGMW-03I and screened at similar intervals. During the RI, a limited DNAPL recovery test was performed at two of these locations using a down-hole electric whale pump. After drawdown, the DNAPL volume in these monitoring wells recovered at varying rates. In CGMW-02I, the DNAPL


16

volume in the well had recovered to within 66% of the pre-pumping level within 2 months. At CGMW-03S, the DNAPL volume recovery was much slower (2.5% recovery in 6 months). Following installation of the DNAPL recovery wells, additional pumping and recovery measurements will be conducted to measure DNAPL recovery rates. Based on the observed DNAPL recovery rates, a determination will be made on the viability of an active or a passive DNAPL recovery system for Parcel I.

4.2.3 Data Report

Once the geotechnical and environmental subsurface explorations are complete, KeySpan will prepare a Data Report. The Data Report will summarize the available geotechnical data and environmental data (including the RI data related to Parcel I), and the utility location, topographic survey, noise data, and vibration data collect under common pre-design activities. The report will describe the subsurface exploration and soil sampling methods, summarize the geotechnical laboratory testing data, summarize the environmental analytical data, include an exploration location plan, and include subsurface profiles. The report will also summarize the background noise data and vibration data, and include locations of background measurements. The Data Report will be used in the design effort and will be provided to contractors for preparation of bids for Parcel I.

4.3 Remedial Design Approach This section presents the proposed approach to the development of remedial design plans and specifications for the Parcel I remedy. The remedial design process is divided into three distinct submittals as required by DER-10: the 50-75% Remedial Design Documents, the 95% Remedial Design Documents, and the Final Remedial Design Documents. Each of these submittals is described in the following subsections of this RDWP.

4.3.1 Remedial Design Documents (50%-75% Design)

The initial design submittal to the NYSDEC will be the 50% to 75% Remedial Design Documents. This represents the preliminary design and contains draft versions of the remedial construction approach, engineering drawings, and technical specifications. The design documents will include the critical aspects of the remedial design for Parcel I and provide the basis for implementation of the remedial action. The 50-75% Design will include the following components:

Design criteria of the excavation support system Movement criteria and geotechnical monitoring requirements Noise and vibration criteria and monitoring requirements Community air monitoring requirements Pre-Design Data Report


17

Proposed Truck Routes and Traffic Mitigation Plan Technical specifications for the Parcel I remedial action Engineering plans (preliminary design drawings) for the Parcel I remedial action.

Comments from the NYSDEC on the 50% to 75% Remedial Design Documents will be addressed in the 95% Remedial Design Documents.

4.3.2 Remedial Design Documents (95% Design)

Following the NYSDEC review and comment on the 50-75% Remedial Design Documents, a 95% version of the Remedial Design Documents will be submitted to the NYSDEC for review and approval. The submittal will contain the final elements of the Remedial Design. The 95% Remedial Design Document will include the following:

Technical Plans and Specifications for the implementation of the Parcel I remedial action A draft OM&M Plan for ongoing activities to be performed after the completion of the

remedial action at Parcel I. An Opinion of Cost level estimate of construction costs for the implementation of the Parcel I

remedial action. Since the plans and specification will be largely performance based, and the ultimate remedial contractor’s means and methods may vary from the Engineer’s assumptions, the cost estimate may vary from the final remedial contractor’s costs.

A schedule for completion of the Parcel I remedial action Comments from the NYSDEC on the 95% Remedial Design Documents will be addressed in the Final Remedial Design Documents.

4.3.3 Remedial Design Documents (Final Design)

The Final Remedial Design Documents will be prepared after receipt of NYSDEC comments on their review of the 95% Remedial Design Documents. After the comments are addressed, KeySpan will meet with NYSDEC to discuss their responses to the comments. Once all responses are accepted by NYSDEC, the Final Remedial Design Documents will be prepared, signed and stamped by a New York State licensed professional engineer, and submitted to NYSDEC. Procurement of a remedial contractor will proceed following receipt of NYSDEC approval of the Final Remedial Design Documents.


18

4.4 Remedial Technologies

4.4.1 Excavation and Shoring

On Parcel I, the excavation activities will be limited to soil and debris in the unsaturated zone to a depth of eight feet below the elevation of the adjacent streets and remnant MGP structures to the extent practicable. The 8-foot excavation limits and the MGP-structure excavation limits are depicted on Figure 3. The preliminary estimate of soil to be excavated is approximately 100,000 cubic yards. In order to remove soils adjacent to the property boundaries and surface roads, an excavation support system is required. The system will be designed to support excavations to the target depths of eight feet below the elevation of the adjacent streets, to up to approximately 30 feet below grade surface in the vicinity of the former gas holders. If Parcel I is scheduled for remediation first, it may be appropriate to slope the excavation limits to the target depth adjacent to Parcels II & III with the understanding that these side slopes will be excavated in the future as part of the remediation of Parcels II & III. The excavation support system will be designed based on the pre-design geotechnical investigation data to meet a performance criteria based on soil movement outside of the sheeting, settlement outside of the sheeting, and dewatering constraints in the saturated zone. These constraints are as follows:

Excavations on Parcel I to remove remnant MGP structures will require limited construction dewatering. The required pumping rate(s) will be estimated during the remedial design.

It is anticipated that groundwater will be treated (as required) on site and discharged either to the local publicly owned treatment works (POTW) or the Gowanus Canal in accordance with the requirements of a SPDES/NPDES permit. An evaluation of the feasibility of discharge to each location will be made during the remedial design.

The design of the proposed excavation support system will be undertaken after the results of the geotechnical portion of the pre-remedial design activities are available. After the design is complete, the technical feasibility of performing excavation without dewatering to remove the remnant structures will be evaluated.

The remedial excavation will be performed according to the following general sequence:

The surface debris will be removed by the City of New York The Parcel I surface materials will be stripped to the elevation of the adjacent streets and

Parcels II & III. The surface materials will be excavated, any construction debris segregated, and the materials will be stockpiled and tested for off-site disposal.

The excavation support and construction dewatering systems will be installed


19

Subsurface soils will be excavated, stockpiled and tested for off-site disposal. Materials will be transported on approved truck routes in accordance with the Traffic Mitigation Plan.

Excavations will extend to eight feet below the elevation of the adjacent streets/parcels or the depth required to remove subsurface remnant MGP structures

Documentation sampling will be collected at the bottom of dry excavations to establish the concentrations of VOCs and PAHs in the materials below the clean surface cover

A visual demarcation barrier will be installed at the interface between the imported clean fill and the underlying soil. If the demarcation is below the water table and dewatering was not required in the area of excavation (ex., potential remnant MGP structures locations), the barrier will be placed at the water table elevation.

The excavation will be backfilled with uncontaminated soil and masonry debris from the site, as appropriate, and imported clean fill to the elevation of the adjacent streets/parcels.

4.4.2 Dense Non-Aqueous Phase Liquid Recovery

The Parcel I remedy will include DNAPL recovery, where practicable. Based on previous investigations and DNAPL recovery efforts on Parcel I it is anticipated that recovery efforts will be passive in nature, collecting on a periodic basis only free DNAPL which readily enters a recovery well. The locations and screen intervals of the DNAPL recovery wells are described in Section 4.2.2.

4.5 Engineering and Institutional Controls Since the remedy results in contamination above unrestricted levels remaining at depth on the site, a Site Management Plan (SMP) will be developed and implemented under an environmental easement or deed restriction placed on the parcel defining the conditions of usage. The SMP will include the institutional and engineering controls to:

Address residual contaminated soil that may be excavated from the site during future use in accordance with NYSDEC regulations for characterization and potential disposal or reuse, as well as addressing appropriate worker heath and safety requirements

Evaluate the potential for vapor intrusion for any future buildings on the site, including mitigative provisions for any impacts identified

Provide for operation and maintenance of the components of the remedy Monitor groundwater Identify any use restrictions on site development or groundwater use.

A periodic Institutional Control/Engineering Control (IC/EC) certification, as required by the NYSDEC, will be required to confirm that the controls put in place are operable and effective.


20

5. Parcels II & III Remedial Design Approach

5.1 Parcels II & III Conceptual Remedy The conceptual remedy for Parcels II and III will include a barrier wall to mitigate the potential for DNAPL and contaminated groundwater migration into the Gowanus Canal and a DNAPL recovery system. The location, depth, and orientation of the proposed barrier wall will depend on the barrier’s potential effects on groundwater flow conditions. The Gowanus Canal is a tidally influenced water body and the shallow groundwater at the site flows toward and discharges to the canal. Installation of a barrier wall would alter this flow pattern and could exacerbate the mounding that occurs in the shallow zone between Parcels I and II. In the deep and intermediate zones, groundwater flow is parallel to the canal. This may necessitate the installation of wing walls and DNAPL recovery trenches/wells at the edges of the wall to prevent migration of DNAPL parallel to the canal. The existing groundwater flow conditions at the site will be modeled so that an evaluation of the barrier wall can be conducted. The groundwater model will be based on hydraulic conductivity, hydraulic head, and tidal study data collected during the Remedial Investigation. Modeling of the groundwater flow will be used to determine the most efficient orientation of the barrier wall that will effectively mitigate impacted groundwater and DNAPL migration off site. The model evaluation will include an assessment of groundwater mounding behind the barrier wall, dissolved contaminant and DNAPL transport, and the potential mitigation measures, including in-situ/ex-situ groundwater treatment (if necessary), or active DNAPL recovery. Current site usage will have to be considered in developing the plans for constructing the barrier wall if the wall installation were to occur prior to removal of the concrete plant on Parcel II and the warehouse on Parcel III. The wall construction means and methods will have to address these physical structures as well as other subsurface obstructions if the areas cannot be cleared and accessed prior to wall construction. Based on these restrictions, it is preferable that construction of the barrier wall occur after the current usage of these parcels is terminated. The specific mode of DNAPL recovery will depend on the site usage as well as the type and configuration of the barrier wall installed as described above. A DNAPL recovery system may include vertical or horizontal collection wells, passive recovery/active pumping, and a central collection/storage facility. Following a change in site usage of either parcel, further remedial efforts will commence. On Parcel III, additional subsurface investigation will be conducted. This investigation will focus on identifying any additional remnant structures from the former MGP operations and determining the


21

vertical and horizontal extent of MGP-related impacts below the footprint of the existing warehouse. The results of this investigation will be used to further evaluate the configuration of the barrier wall on Parcel III. In addition to the subsurface investigation on Parcel III, following a change in site usage the remedy will include the excavation of unsaturated soils on Parcels II and III to a maximum depth of eight feet below the existing street/parcel grade. Where accessible, subsurface MGP-era structures and their contents will be removed. These localized deeper excavations may be used as a clean utility corridor to support site redevelopment and will likely extend from the intersection of Fifth and Hoyt Streets to the center of Parcel II and from Smith Street to the center of the Parcel III. A visual excavation barrier will be installed to demarcate the limits of the remedial excavation and to prevent future inadvertent contact with deeper soils. MGP-impacted excavated soils will be transported off site for treatment and disposal at an appropriately permitted facility. Uncontaminated soil and uncontaminated masonry debris from the subsurface structures may be returned to the excavation as backfill. The excavation will be brought to final grade using clean backfill meeting NYSDEC requirements. The final grade of the site will match the existing grade of the adjacent streets and properties.

5.2 Pre-Remedial Design Activities The following sections describe the pre-remedial design activities to be performed at Parcels II & III of the site. The purpose of the pre-remedial design activities is to obtain supplemental site information necessary for the completion of the design of the Parcels II & III remedy.


An investigation will be conducted to acquire geotechnical data through the installation of soil borings, the collection of soil samples and the performance of various field and laboratory testing. The data collected will be used in the design and construction of the barrier wall and excavation shoring systems to support the excavations on Parcels II & III. The geotechnical investigation will include the installation of up to 20 soil borings along the proposed barrier wall location and the proposed location of excavation shoring system alignment at the perimeter of the Parcels II and III. The general areas of the borings coincide with the potential shoring and containment wall alignments (Sections 5.4.1 and 5.4.2) and are depicted on Figure 5. The borings will be advanced at approximately 100-foot intervals. The soil borings will be advanced using a combination of rotosonic and either hollow-stem auger or mud-rotary drilling methodologies to estimated depths of 60 to 120 feet below ground surface. Borings will be advanced through the surface debris and obstructions (remnant foundations, concrete wash pits, etc) using rotosonic techniques. The borings will then be completed to depth using


22

hollow-stem auger or mud-rotary drilling methodologies. Standard penetration tests will be performed in each boring. Split barrel samples will be obtained continuously in urban fill materials and at 5-foot intervals in native deposits. If encountered, organic and fine-grained soil will be sampled using a thin-walled sampler. Index tests consisting of grain-size analysis, organic content, Atterberg Limits and moisture content will be performed on soil samples. Upon completion, the test borings will be tremie grouted to grade using a Portland cement/bentonite slurry mixture or completed as DNAPL recovery wells to support DNAPL recovery testing as described in Section 5.2.3. In addition to the soil borings, cone penetration tests (CPTs) will be performed in four to six locations. Cone penetrometer probes will be advanced to estimated depths of 60 feet below ground surface. Some penetrometer probes may be advanced to deeper depths. Cone data (tip, skin friction, and water pressure) will be obtained at 5-centimeter intervals from the cone penetrometer probes. The CPTs will be used to evaluate subsurface stratification, soil type, soil density, in-situ stress conditions and shear strength parameters. If impacted material is observed in the borings, a select number of samples may be collected and submitted to a New York State Environmental Laboratory Approval Program (ELAP)-certified laboratory for volatile organic compounds (VOCs) via USEPA Method 8260 and semivolatile organic compounds (SVOCs) via USEPA Method 8270. All work will be performed in accordance with the NYSDEC-Approved Health and Safety Plan (HASP) and a Quality Assurance Project Plan (QAPP) meeting NYSDEC requirements.

5.2.2 Supplemental Hydrogeologic Assessment

Groundwater mounding and utility influence may be important factors in modeling the effect of the proposed remedy on the water table. A field investigation, consisting of piezometer installation and groundwater elevation monitoring, will be conducted to assess the cause of the groundwater mound observed on Parcel I and the potential influence of the sanitary sewer on groundwater flow. The cause of the mound is not known based on investigations to date but may be related to buried structures, natural recharge, lower-permeability soil, and/or utilities. Seven boring will be advanced on Parcels I and III in the vicinity of Holder No. 2 and the 72-inch sanitary sewer that crosses the site. Soil samples will be collected and logged continuously at each boring location in accordance with the NYSDEC-approved RI work plan. Each of the borings will be completed as a piezometer. On Parcel I, four piezometers will be screened across the water table (10-20 feet below grade), and two will be screened in an underlying sand unit 30-40 feet below grade. ON Parcel III, one piezometer will be installed near CGMW-09 as close as possible to the sanitary sewer and screened across the approximate elevation of the sewer. All piezometers will be installed in accordance with the NYSDEC-approved RI work plan.


23

5.2.3 Hydraulic Modeling

A groundwater model will be created using data collected during the Remedial Investigation and remedial design investigations at the various parcels. This model will be used to evaluate the optimum wall configuration to reduce surface mounding of groundwater behind the wall and prevent discharge of impacted groundwater around the barrier. Based on the findings and sensitivity analysis of the groundwater model, additional transport analyses may be prudent prior to finalization of the conceptual wall configuration. Such analyses may include tracer studies to confirm the model findings and help refine the localized predictions of the model, particularly in the tidally-influenced discharge area of the site. KeySpan will discuss any potential additional groundwater transport analyses with NYSDEC following completion of the groundwater modeling efforts. The model evaluation will include an assessment of groundwater mounding behind the barrier wall, dissolved contaminant and DNAPL transport, and the potential mitigation measures, including in-situ/ex-situ groundwater treatment (if necessary), or active DNAPL recovery. The following potential wall alignments within Parcels II and III will be modeled:

Along canal (approximately 1,000 feet total wall length) Along canal with wing walls inland on one or both sides (approximately 1,400 to 1,800 feet

total wall length) Along the entire perimeter of Parcels I, II and III (approximately 3,500 feet total wall length)

Variations in wall depth, location, and permeability will be modeled as needed to establish a configuration that minimizes alterations to site groundwater flow. Modeled wall depths will be varied within the intermediate and deep sand layers (approximately 40 to 80 feet below ground surface). Wall location may be varied with distance from the canal (approximately 10 to 50 feet from the existing bulkhead). Wall permeability will be based on construction material. The modeled variations will be coordinated with other design criteria. The primary model deliverable will be a matrix of predicted results based on the variable design criteria. Final barrier wall alignment will be based on a configuration that will effectively mitigate impacted groundwater and DNAPL migration off site. The model will be used to establish post-construction performance monitoring criteria. A three-dimensional model is necessary because of the complex stratigraphy and the extent of the proposed remedy. In the shallow zone, installation of a barrier wall could exacerbate the natural mounding that occurs between Parcels I and II. This may necessitate mitigative measures such as drainage or capping. In the deep and intermediate zones, groundwater flow is parallel to the canal. This may require the installation of wing walls and DNAPL recovery trenches/wells at the edges of the wall to prevent migration of DNAPL parallel to the canal. In the deep zone, a slight upward vertical gradient may be associated with a connection with the underlying Jameco Sand.


24

The model will consist of a three-dimensional numerical model developed using Visual MODFLOW(R). The groundwater model will be based on hydraulic conductivity, hydraulic head, and tidal study data collected during the Remedial Investigation (RI), and on regional data. The model will include tidal effects and other influences such as precipitation recharge. The proposed model will include hydraulic flow only. No transport of dissolved contaminants or NAPL will be simulated in the model. The effect of the proposed wall on dissolved contaminant and NAPL transport will be estimated based on the hydraulic flow results and the characteristics of the contaminants and NAPL. The effect on NAPL will be estimated based on relative changes in head, gradient, and velocities in the zones containing NAPL, as well as NAPL density and viscosity, and soil stratigraphy. For design purposes, we will conservatively assume that dissolved contaminant flow occurs at the same rate and direction as the predicted groundwater flow. As discussed above, because the site setting is hydrogeologically complex, KeySpan will conduct a sensitivity analysis on the final model outcome to determine whether additional dissolved phase transport evaluation approaches, such as tracer analyses or additional monitoring points, would be necessary prior to finalization of the wall configuration.

5.2.4 DNAPL Recovery Well Installation and Pilot Study

Due to the nature of the DNAPL observed at this site, the PVC monitoring wells installed during the Remedial Investigation had degraded and any monitoring wells that were screened through or within the DNAPL were abandoned to prevent horizontal migration of DNAPL. Therefore, four to six stainless steel monitoring wells will be installed at Parcels II & III. These wells will be screened in DNAPL zones to depths of no greater than 120 feet below grade. These wells will be used to study DNAPL recovery for potential active remediation. The wells will be located in the vicinity of the former RI monitoring wells CGMW-06I and CGMW-07I, CGMW-07D, and CGMW-08I and screened at similar intervals as the wells they are replacing. During the RI, a limited DNAPL recovery test was performed at these locations using a down-hole electric whale pump. Following removal, DNAPL recovered in these monitoring wells at varying rates (Table 9). In CGMW-06I, the DNAPL volume in the well had recovered to the pre-pumping level within 2 weeks. At CGMW-07I and CGMW-07D, the DNAPL volume did not recover as quickly (60 and 65% recovery in 2 months, respectfully). Finally, at CGMW-08I, the DNAPL volume in the well did not recover significantly following pumping. The initial measurable thickness of 37.33 feet of DNAPL was drawn down to 33.1 feet after pumping and did not recover significantly over the 6-month long study (less than 2% recovery). Following installation of the new DNAPL recovery wells, a pilot study consisting of additional pumping and recovery measurements will be conducted to measure DNAPL recovery rates. Based on the observed DNAPL recovery rates, a determination will be made on the viability of an active DNAPL recovery system or a passive DNAPL recovery program for Parcels II and III.


25

The results of the pilot study and the hydrologic modeling will be used to develop the final design of the DNAPL recovery and collection system.

5.2.5 Supplemental Remedial Investigations

Following a change in site usage on Parcel III, an additional subsurface investigation will be conducted. This investigation will include the advancement of soil borings, installation of monitoring wells, and excavation of test pits. The investigation will be focused on identifying the vertical and horizontal extent of MGP-related impacts below the footprint of the existing warehouse as well as any additional remnant structures from the former MGP operations that will be removed during remediation. The results of this investigation will be used to further evaluate the configuration of the barrier wall on Parcel III.

5.2.6 Subsurface Obstruction Identification

There are significant obstructions along the Gowanus Canal that were observed or documented during the RI. These include, but are not limited to: former MGP structures; two active high pressure natural gas mains; a combined sewer line; tiebacks, deadmen, and bracing for the Gowanus Canal bulkhead; and concrete wash pits on Parcel II. The wash pits may contain up to 18 feet of solidified concrete wash. The locations and extent of these obstructions will impact the type of wall that can be installed in this area and the means of installation, and may force the installation of a barrier along the canal side of the existing bulkhead. A series of test pits will be dug along the Gowanus Canal to identify the depth and extent of these impacts. The locations of the obstructions and the extent of the Gowanus Canal bracing will affect the placement of the barrier and will be addressed in the remedial design.

5.2.7 Additional Pilot/Treatability Studies

Following the completions of the hydraulic model and geotechnical investigations, the material and configuration of the barrier wall will be determined. It is anticipated that based on site constraints, subsurface conditions, and existing utilities, that a combination of multiple barrier technologies may be necessary. Pilot testing of the various technologies that could be implemented at the site may be required for the final determination of the barrier materials. This testing would confirm that the barrier material types can be installed at the site prior to final design. Pilot scale testing could include testing of interlocking sheet piles, a slurry wall, a jet grout wall, or a combination of technologies to establish that the selected method is constructable. Once the specific configuration and materials are determined, additional compatibility testing of the barrier wall materials with site DNAPL may be required. The DNAPL observed during the RI has a low flashpoint (90 degrees Fahrenheit) and high styrene content. The high styrene content contributed to the DNAPL corrupting the integrity of the PVC monitoring wells that were installed at the site. The compromised wells were abandoned to avoid downward migration of shallow DNAPL


26

within the monitoring wells. The shallow DNAPL entered these wells in areas where the PVC well casing was encased in a Portland cement/bentonite grout mixture. It is not known whether the grout failed from the styrene or the DNAPL migrated along cracks or fractures in the grout to contact the PVC wells. Therefore, material compatibility testing is required to determine if the DNAPL at the site could cause a failure of a barrier based on chemical incompatibility. If these studies prove necessary, a separate work plan and schedule modification will be developed and submitted to NYSDEC for review and approval.

5.2.8 Data Report

Once the pre-design investigations are complete, KeySpan will prepare a Data Report. The Data Report will summarize all the available geotechnical data and environmental data (including the RI data related to Parcels II & III), and the utility location, topographic survey, noise data, and vibration data collect under common pre-design activities. The report will describe the subsurface exploration and soil sampling methods, summarize the geotechnical laboratory testing data, summarize the environmental analytical data, include an exploration location plan, and include subsurface profiles. The report will also summarize the hydraulic model and the background noise data and vibration data. The Data Report will be used in the design effort and will be provided to contractors for preparation of bids for Parcels II & III.

5.3 Remedial Design Approach This section presents the proposed approach to the development of remedial design plans and specifications for the Parcels II and III remedy. The remedial design process is divided into three distinct submittals as required by DER-10: the 50-75% Remedial Design Documents, the 95% Remedial Design Documents, and the Final Remedial Design Documents. Each of these submittals is described in the following subsections of this RDWP.

5.3.1 Remedial Design Documents (50%-75% Design)

The initial design submittal to the NYSDEC will be the 50% to 75% Remedial Design Documents. This represents the preliminary design and contains draft versions of the remedial construction approach, engineering drawings, and technical specifications. The design documents will include the critical aspects of the remedial design for Parcels II & III and provide the basis for implementation of the remedial action. The 50-75% Design will include the following components:

Configuration and design criteria for the barrier wall based on the results of the hydraulic model and geotechnical investigation


27

Design criteria of the excavation support system Movement criteria and geotechnical monitoring requirements Design criteria for the active DNAPL recovery system Noise and vibration criteria and monitoring requirements Community air monitoring requirements Pre-Design Data Report Proposed Truck Routes and Traffic Mitigation Plan Technical specifications for the Parcels II & III remedial action Engineering plans (preliminary design drawings) for the Parcels II & III remedial action.

Comments from the NYSDEC on the 50% to 75% Remedial Design Documents will be addressed in the 95% Remedial Design Documents.

5.3.2 Remedial Design Documents (95% Design)

Following the NYSDEC review and comment on the 50-75% Remedial Design Documents, a 95% version of the Remedial Design Documents will be submitted to the NYSDEC for review and approval. The Draft 95% Remedial Design Documents will contain the final elements of the remedy design. The Draft 95% Remedial Design Document will include the following.

Technical Plans and Specifications for the implementation of the Parcels II & III remedial action.

A draft Operations, Maintenance and Monitoring (OM&M) Plan for ongoing activities to be performed after the completion of the remedial action at Parcels II & III

An Opinion of Cost level estimate of construction costs for the implementation of the Parcels II & III remedial action. Since the plans and specification will be largely performance based, and the ultimate remedial contractor’s means and methods may vary from the Engineer’s assumption, the cost estimate may vary from the final remedial contractor’s costs.

A schedule for completion of the Parcels II & III remedial action Comments from the NYSDEC on the 95% Remedial Design Documents will be addressed in the Final Remedial Design Documents.

5.3.3 Remedial Design Documents (Final Design)

The Final Remedial Design Documents will be prepared after receipt of NYSDEC comments on their review of the 95% Remedial Design Documents. After the comments are addressed, KeySpan will meet with NYSDEC to discuss the responses to the comments. Once all responses are accepted by NYSDEC, the Final Remedial Design Documents will be completed, signed and stamped by a New York State licensed professional engineer, and submitted to NYSDEC. Procurement of a remedial


28

contractor will proceed following receipt of NYSDEC approval of the Final Remedial Design Documents.



On Parcels II and III, the excavation activities will be limited to soil and debris in the unsaturated zone to a depth of eight feet below the elevation of the adjacent streets and the bulkhead of the Gowanus Canal, and excavation of remnant MGP structures to the extent practicable. The eight foot excavation limits and the MGP-structure excavation limits are depicted on Figure 5. The preliminary estimate of soil to be excavated is approximately 82,000 cubic yards. In order to remove soils adjacent to the property boundaries and surface roads, an excavation support system is required. The system will be designed to support excavations to the target depths of eight feet below the elevation of the adjacent streets. The design of excavations support system for Parcel III may vary based on the results of any remnant MGP structures identified during supplemental investigations below the warehouse footprint. If Parcel I was remediated prior to the Parcels II and III effort with a sloped excavation along their common boundary, the excavation will extend into Parcel I to remove materials from the slope left in place during the Parcel I excavation. The excavation support system will be designed based on the pre-design geotechnical investigation data to meet a performance criteria based on soil movement outside of the sheeting, settlement outside of the sheeting, and dewatering constraints in the saturated zone. These constraints include the following:

Excavations on Parcels II & III to remove remnant MGP structures may require limited construction dewatering. The required pumping rate(s) will be estimated during the remedial design. Due to the proximity of the Gowanus Canal, excavations requiring dewatering may be limited to after the installation of the barrier wall.

It is anticipated that groundwater will be treated (as required) on site and discharged either to the local publicly owned treatment works (POTW) or to the Gowanus Canal in accordance with the requirements of a SPDES/NPDES permit. An evaluation of the feasibility of discharge to each location will be made during the remedial design.




29

The structures located on Parcels II and III will be removed by the City of New York. The barrier wall will be installed The excavation support and construction dewatering systems (if necessary) will be installed Subsurface soils will be excavated, stockpiled and tested for off-site disposal. Materials will

be transported on approved truck routes in accordance with the Traffic Mitigation Plan. Excavations will extend to eight feet below the elevation of the adjacent streets/parcels or the

depth required to remove subsurface remnant MGP structures. Documentation samples will be collected at the bottom of the excavation to establish the

concentrations of VOCs and PAHs in the materials below the clean surface cover. A visual demarcation barrier will be installed at the interface between the imported clean fill

and the underlying soil. If the demarcation is below the water table and dewatering was not required in the area of excavation (ex., potential remnant MGP structures locations), the barrier will be placed at the water table elevation.


5.4.2 Subsurface Containment Barrier Wall

The specific configuration of the barrier wall will be determined following the completion of pre-design activities. Various barrier materials and methods of installation will be evaluated and tested. It is anticipated that based on site constraints, subsurface conditions, and existing utilities, that a combination of multiple barrier technologies may be necessary. The technologies to be evaluated include interlocking sheet piles, a slurry wall, and a jet grout wall. The configuration and installation technology will be addressed in the remedial design and presented in the 50-75% Remedial Design Documents for NYSDEC review and approval.

5.4.3 In-Situ Groundwater Treatment

Based on the results of the hydrologic model and the final subsurface containment barrier wall configuration, groundwater treatment may be required to address shallow dissolved phased contamination at the site boundaries. As described in Section 5.2.2 above, in the shallow zone, installation of a barrier wall could exacerbate the natural mounding that occurs between Parcels I and II. If the configuration of the barrier wall cannot be adjusted to mitigate these effects then the mounded groundwater will have to be allowed to migrate through or around the containment barrier via perforated sections or treatment windows. In the event that this is necessary, various groundwater treatment technologies will be evaluated and an applicable technology selected. The results of this evaluation will be presented to NYSDEC for review and approval. If bench scale or pilot testing of the groundwater treatment technology is necessary, then an additional work plan will be developed and submitted to NYSDEC for review and approval.


30

5.4.4 Dense Non-Aqueous Phase Liquid Recovery

The Parcels II & III remedy will include DNAPL recovery, where practicable. Based on previous investigations and DNAPL recovery efforts on Parcels II & III it is anticipated that recovery efforts will be active in nature. The locations and screen intervals of the DNAPL recovery wells are described in Section 5.2.2. The specific mode of DNAPL recovery will be dependant on the site usage as well as the type and configuration of the barrier wall installed as described above. A DNAPL recovery system may include vertical or horizontal collection wells, passive recovery with periodic active pumping, and a central collection/storage facility. All components of the system will be designed and constructed to be chemically compatible with the DNAPL observed at the site (including high styrene concentrations, low flashpoint). This may require that components in contact with DNAPL from the site to be stainless steel; electrical systems to be explosive proof; and the collection system be housed in a permanent structure with appropriate heating, ventilation, and air conditioning controls to maintain temperatures well below the 90 degree Fahrenheit flashpoint of the DNAPL.

5.5 Engineering and Institutional Controls Since the remedy results in contamination above unrestricted levels remaining at depth on the site, a Site Management Plan (SMP) will be developed and implemented under environmental easements or deed restrictions placed on the parcels defining the conditions of usage. The SMP will include the institutional and engineering controls to:






31

6. Parcel IV Interim Remedial Measure

6.1 Parcel IV Conceptual Remedy The conceptual remedy for Parcel IV will include excavation of shallow impacted soils at the southeast corner of Parcel IV to a depth of 11 feet below existing grade. MGP-impacted excavated soils will be transported off site for treatment and disposal at an appropriately permitted facility. Uncontaminated soil and uncontaminated masonry debris from subsurface structures may be returned to the excavation as backfill. The excavation will be brought to final grade using clean backfill meeting NYSDEC requirements. Asphalt paving will be replaced to meet pre-existing conditions. The final grade of the site will match the existing grade of the adjacent streets and property. It is anticipated that the remedy on Parcel IV will be undertaken as an Interim Remedial Measure (IRM). As there will be no other shallow MGP-impacted material remaining on the parcel, it is anticipated that this IRM will represent the extent of the remedy for Parcel IV. There is no current negotiated access to the site for the purposes of remediation. Therefore, access to the property may affect the timing and scope of the remedy.

6.2 Pre-Interim Remedial Measure Activities The following sections detail the pre-IRM activities to be performed at Parcel IV of the site. The purpose of the pre-IRM activities is to obtain supplemental site information necessary for the completion of the IRM at Parcel IV.


An investigation will be conducted to acquire geotechnical data through the installation of soil borings, the collection of soil samples and the performance of various field and laboratory testing. The data collected will support the design and construction of the excavation shoring systems to support the excavations on Parcel IV. The geotechnical investigation will include the installation of up to six soil borings along the proposed excavation shoring system alignment at the perimeter of Parcel IV. The general area of the borings coincides with potential shoring alignments (Section 6.4.1) and are depicted on Figure 6. The borings will be advanced at approximately 100-foot intervals. Two to four of the soil borings will be advanced using either hollow-stem auger or mud-rotary drilling methodologies to estimated depths of 40 to 50 feet below ground surface. Standard penetration tests will be performed in each boring. Split barrel samples will be obtained continuously


32

in urban fill materials and at 5-foot intervals in native deposits. If encountered, organic and fine-grained soil will be sampled using a thin-walled sampler. Index tests consisting of grain-size analysis, organic content, Atterberg Limits and moisture content testing will be performed on soil samples. Upon completion, the test borings will be tremie grouted to grade using a Portland cement/bentonite slurry mixture. In addition to the soil borings, cone penetration tests (CPTs) will be performed in two to four locations. Cone penetrometer probes will be advanced to estimated depths of 40 to 50 feet below ground surface. Some penetrometer probes may be advanced to deeper depths. Cone data (tip, skin friction, and water pressure) will be obtained at 5-centimeter intervals from the cone penetrometer probes. The CPTs will be used to evaluate subsurface stratification, soil type, soil density, in-situ stress conditions and shear strength parameters. If impacted material is observed in the borings, a select number of samples may be collected and submitted to a New York State Environmental Laboratory Approval Program (ELAP)-certified laboratory for volatile organic compounds (VOCs) via USEPA Method 8260 and semivolatile organic compounds (SVOCs) via USEPA Method 8270 and additional disposal characterization as discussed in Section 4.2.2. All work will be performed in accordance with the NYSDEC-Approved Health and Safety Plan (HASP) and a Quality Assurance Project Plan (QAPP) meeting NYSDEC requirements.

6.2.2 In-Situ Pre-Characterization

Due to the limited area available for stockpiling material at Parcel IV, it is anticipated that the excavation at Parcel IV will be conducted as a direct load operation. To facilitate a direct load operation for the soils excavated from Parcel IV, a pre-characterization sampling program will be implemented. This program will include the installation of Geoprobe cores at 25 feet grid-points within the excavation area to depths of 12 feet below grade. At each borehole location, a maximum of two soil samples will be collected for VOCs and SVOCs. Up to five composite samples will be collected from the borings for other disposal analyses including total cyanide, metals, and PCBs. The final disposal criteria and sampling frequency will be based on the receiving facility requirements.

6.2.3 Data Report

Once the geotechnical investigations and in-situ pre-characterization sampling are complete, KeySpan will prepare a Data Report. The Data Report will summarize all the available geotechnical data and environmental data (including the RI data related to Parcel IV), and the utility location, topographic survey, noise data, and vibration data collect under common pre-design activities. The report will describe the subsurface exploration and soil sampling methods, summarize the geotechnical laboratory testing data, summarize the environmental analytical data, include an


33

exploration location plan, and include subsurface profiles. The report will also summarize the background noise data and vibration data, and include locations of background measurements. The Data Report will be used in the design effort and provided to contractors for preparation of bids for the Parcel IV IRM.

6.3 Interim Remedial Measure Approach This section presents the proposed approach to the IRM that will be implemented for Parcel IV of the site. The IRM process is divided into two IRM Work Plan deliverables in general accordance with DER-10. Each of these work plans is detailed in the following subsections of this RDWP.

6.3.1 Draft Interim Remedial Measure Work Plan

The initial submittal to the NYSDEC will be the Draft IRM Work Plan. This submittal will contain draft versions of the remedial construction approach, engineering drawings, and technical specifications. The design documents will include the critical aspects of the IRM for Parcel IV and provide the basis for implementation of the IRM. The Draft IRM Work Plan will include the following components:

Design criteria of the excavation support system Movement criteria and geotechnical monitoring requirements Noise and vibration criteria and monitoring requirements Community air monitoring requirements Pre-Design Data Report Proposed Truck Routes and Traffic Mitigation Plan Technical specifications for the Parcel IV IRM Engineering plans (preliminary design drawings) for the Parcel IV IRM.

Comments from the NYSDEC on the Draft IRM Work Plan will be addressed in the Final IRM Work Plan.

6.3.2 Final Interim Remedial Measure Work Plan

The Final IRM Work Plan will be prepared after receipt of NYSDEC comments on their review of the Draft IRM Work Plan. After the comments are addressed, KeySpan will meet with NYSDEC to discuss the responses to the comments. Once all responses are accepted by NYSDEC, the Final IRM Work Plan will be completed, signed and stamped by a New York State licensed professional engineer, and submitted to NYSDEC. Procurement of a remedial contractor will proceed following receipt of NYSDEC approval of the IRM Work Plan.


34

The Final IRM Work Plan will include the following components: Technical Plans and Specifications for the implementation of the Parcel IV IRM A draft Operations, Maintenance and Monitoring (OM&M) Plan for ongoing activities to be

performed after the completion of the IRM at Parcel IV An Opinion of Cost level estimate of construction costs for the implementation of the Parcel

IV IRM. Since the plans and specification will be largely performance based, and the ultimate remedial contractor’s means and methods may vary from the Engineer’s assumption, the cost estimate may vary from the final remedial contractor’s costs.

A schedule for completion of the Parcel IV IRM



On Parcel IV, the excavation activities will be limited to soil and debris in the unsaturated zone to a depth of 11feet below grade and remnant MGP structures to the extent practicable. The 11-foot excavation limit is depicted on Figure 5. The preliminary estimate of soil to be excavated is approximately 9,400 cubic yards. In order to remove soils adjacent to the surface roads, an excavation support system is required. The system will be designed to support excavations to the target depths of eleven feet below grade. The excavation support system will be designed based on the pre-design geotechnical investigation data to meet a performance criteria based on soil movement outside of the sheeting, settlement outside of the sheeting, and dewatering constraints in the saturated zone. These constraints include the following:

Excavations on Parcel IV will require limited construction dewatering. The required pumping rate(s) will be estimated during the remedial design.

It is anticipated that groundwater will be treated (as required) on site and discharged either to the local publicly owned treatment works (POTW) or to the Gowanus Canal in accordance with the requirements of a SPDES/NPDES permit. An evaluation of the feasibility of discharge to each location will be made during the remedial design.



35


The excavation support and construction dewatering systems will be installed Subsurface soils will be excavated and direct loaded for off-site disposal. Materials will be

transported on approved truck routes in accordance with the Traffic Mitigation Plan. Excavations will extend to 11-feet below the existing grade or the depth required to remove

subsurface remnant MGP structures. Documentation sampling will be collected at the bottom of the excavation to establish the

concentrations of VOCs and PAHs in the materials below the clean surface cover A visual demarcation barrier will be installed at the interface between the imported clean fill

and the underlying soil. If the demarcation is below the water table and dewatering was not required in the area of excavation (ex., potentially remnant MGP structures locations), the barrier will be placed at the water table elevation.


6.5 Engineering and Institutional Controls Since the IRM results in contamination above unrestricted levels remaining at depth on the site, a Site Management Plan (SMP) will be developed and implemented under an environmental easement or deed restriction placed on the parcel defining the conditions of usage. The SMP will include the institutional and engineering controls to:






36

7. Quality Assurance Project Plan

A generic construction Quality Assurance Project Plan (QAPP) has been developed to address quality control/quality assurance (QA/QC) issues and ensure the integrity of analytical data obtained during all investigation and remedial activities to be performed at the Carroll Gardens/Public Place site. The generic QAPP, entitled Draft Construction Quality Assurance Project Plan, Carroll Gardens/Public Place, Brooklyn, New York, is included in Appendix A The QAPP is based on projected sample collection activities to be performed during the pre-design and design activities at the Site. This QAPP will supersede the previous NYSDEC-approved QAPP, which was prepared during the RI and was limited to investigation activities and analytical sampling. The QAPP may need to be revised at certain times to include unexpected sampling or construction activities. The QAPP includes:

The organization for the performance of the field activities and the responsibilities of the personnel performing the field work

QA/QC objectives to ensure the integrity of data Procedures for collecting, handing and tracking all environmental sample. Quality Audits Preventive measure procedures to ensure the integrity of the data Corrective action procedures.

Amendments to the QAPP to reflect specific activities related to the pre-design and design work for Parcels I, II, III, & IV will be developed and appended to the QAPP.


37

8. Permits

Summarized below are the potential permits required for the implementation of the major elements of the selected remedy. Final design and approach to the program will dictate the actual permits required. Each permit is listed under the associated element of the remediation. It is recognized that potential consolidation of several of the permits could result in simplifying the permitting effort. In addition, while we recognize that the administrative application for a number of the State permits may officially be waived because the construction will be conducted under NYSDEC supervision; they have been listed as well in that the substantive requirements of such permits must still be met. These permits are noted as such (*). With the above in mind, the elements that are considered requiring permitting are as follows:

1) Installation of a subsurface barrier wall along the Gowanus Canal bulkhead, potentially requiring

barge-supported construction equipment: a. US Army Corps of Engineers (USACE) Permit to work in/on a navigatable waterway b. Borough of Brooklyn Building permit c. US Coast Guard permit to disrupt a navigation canal d. State of New York Department of Marine Resources; Endangered Species Assessment,

Marine Habitat Impact Review e. NYC Harbor Authority permits for working within 100 feet of a waterway or wet land.

2) Excavation of contaminated soils and subsurface MGP-related structures throughout Parcels I through IV, disposal and subsequent backfilling with clean fill:

a. Borough of Brooklyn Building permit b. Soil Erosion and Sediment Control Plan c. NYC Harbor Authority permits for working within 100 feet of a waterway or wet land d. NYSDEC Solid Waste disposal permit e. NYSDEC Air Permit * f. Waste Transport Permit.

3) Maintenance and/or disturbance of 72 inch Sewer Line:

a. Sanitary District Sewer Line Alteration Permit 4) Maintenance or diversion of Borough of Brooklyn streets, surface and subsurface storm drains:

a. Borough of Brooklyn Public Works Department b. Borough of Brooklyn Highway Department.

5) Maintenance or diversion of privately owned surface and subsurface storm drains:

a. Borough of Brooklyn Public Works Department b. Written authorization from property owners/landlord/ etc.


38

6) Maintenance and or diversion of water mains and service connection, and gas mains and

connections in the work area: a. Borough of Brooklyn Water Department (or Operator of system) b. Gas Company.

7) Securing and relocating above and below ground electric utility services:

a. The local Electric Utility will most likely do this work, but it is noted that work requests require several months notice with a written plan.

8) Installation of equipment to transport, treat, and discharge groundwater pumped from the

remediation work site and/or removed from soils and debris during the “construction” phase of this project. This identifies the “short term” water discharges from the construction phase of the project:

a. NYSDEC SPDES permit for direct discharge to canal * b. USACE discharge to navigable waters permit c. Borough of Brooklyn building permit d. NYSDEC Air Emissions Permit*.

9) Installation of equipment to transport, treat, and discharge groundwater potentially pumped from

behind the subsurface barrier wall to minimize the effects of mounding ground water at the site during and after contaminated soils removal. This element includes the discharge of water generated in the DNAPL recovery phase of the project; characterized as “long term” water discharges from the site:

a. NYSDEC SPDES permit for direct discharge to canal * b. USACE discharge to navigable waters permit c. Borough of Brooklyn building permit d. NYSDEC Air Emissions Permit*.

10) Installation of equipment to transport treat, and discharge storm water impacted by the

remediation activities on site:

a. US Environmental Protection Agency (EPA) Storm Water General Permit b. NYSDEC Storm Water Permit*, c. Soil Erosion and Sediment Control Plan d. NYSDEC Air Emissions Permit*.


39

9. Operations, Monitoring, and Maintenance Plan Outline

The OM&M plan will be developed using the draft outline below. The outline is in general compliance with the elements listed in Appendix 6B of the Draft DER-10. The final OM&M plan will be updated to reflect specific aspects of the remedial design. 1.0 Introduction

1.1 Project 1.2 Purpose of OM&M Manual 1.3 Special Site-Specific Safety Warnings 1.4 Records Management

2.0 Site Description 2.1 History 2.2 Geology and Hydrogeology

3.0 Site Remedial Action 3.1 Description of Remedial Action 3.2 Goals of Remedial Action

4.0 Groundwater Monitoring Program 4.1 Monitoring Plan 4.2 Remedy Effectiveness Monitoring 4.3 Analytical Program 4.4 Data Evaluation

5.0 Dense Non-Aqueous Phase Liquid (DNAPL) Recovery 5.1 DNAPL Level Monitoring 5.2 Passive DNAPL Recovery Program 5.3 Active DNAPL Recovery Program 5.4 DNAPL Disposal 5.5 DNAPL System Maintenance Program

6.0 Maintenance Program (includes treatment system, site security, and institutional controls)

6.1 Maintenance Activities 6.2 Inspections and Maintenance 6.3 Preventive Maintenance Schedules

7.0 Reports

7.1 Quarterly Reports 7.2 Annual Reports


40

8.0 Citizen Participation

8.1 OM&M Citizen Participation Plan 8.2 Contact List

9.0 Personnel 9.1 Organization 9.2 Responsibilities and Duties 9.3 Training Requirements

10.0 Health and Safety Plan 11.0 Records and Forms

11.1 Operating/Inspection 11.2 Monitoring 11.3 Maintenance 11.4 Waste Disposal 11.5 Maintenance Parts, Vendors, and Costs

12.0 Emergency Contingency Plan 12.1 Emergency Spill Response 12.2 Fire / Explosion 12.3 Personal Injury 12.4 Toxic Exposures 12.5 Public Notification 12.6 Emergency Telephone Numbers, Map and Directions to Nearest Health Facility

13.0 Record Drawings

Appendix A: Monitoring Well Logs Appendix B: Recovery Well Logs Appendix C: Material Safety Data Sheets

D R A F T R E M E D I A L D E S I G N W O R K P L A N C A R R O L L G A R D E N S / P U B L I C P L A C E K E Y S P A N C O R P O R A T I O N

Tables


Figures


Plates


Appendix A

Quality Assurance Project Plan

Final Remedial Design Work Plan Carroll Gardens/Public Place Final Remedial Design Work Plan... ·...

Documents

Transcript of Final Remedial Design Work Plan Carroll Gardens/Public Place Final Remedial Design Work Plan... ·...