Dredging navigation channels, berthing piers and anchorage areas in the Port of New York and New Jersey is necessary to maintain the New York & New Jersey Harbor and its water dependent facilities (Figure 1). The Harbor requires dredging because fine-grained sediments, transported by rivers and within estuaries, settle and accumulate on the sea floor, causing shoaling which interferes with safe navigation.
The success of ocean commerce within the Port depends on a regular and predictable maintenance and new work dredging program. Existing channel depths must be maintained to allow safe clearance, and deeper navigation channels must be excavated for modern cargo ships if the viability of the Port is to continue.
Using dredged material from the Harbor to cover existing sediments at the Historic Area Remediation Site (HARS) represents an environmentally beneficial use of this resource. Bottom sediments at the HARS which may have the potential to cause adverse effects are being capped with cleaner sediments dredged from the Harbor which meet the criteria of the Ocean Dumping Act and will not cause adverse effects. Placement of this material at the HARS is remediating the site by reducing impacts to acceptable levels and improving habitat conditions for bottom dwelling organisms.
Mud Dump Site History
Historically, most of the material dredged from the Port has been disposed in the Atlantic Ocean, in and around an area known as the New York Bight Dredged Material Disposal Site. Commonly referred to as the Mud Dump Site (MDS), it is located in a region of the inner New York Bight known as the New York Bight Apex (Figure 2). The location of the former MDS is still marked by a surface buoy (Figure 3). The use of this region as an area for the disposal of an assortment of materials dates back to the mid-1800s (Figure 4).
To accommodate the increasing need for the disposal of the assorted material, The Office of Supervisor of New York Harbor was established by an act of Congress in 1888. The Harbor Supervisor, acting through the Office of the Chief of Engineers (of the U.S. Army Corps of Engineers), was responsible for the designation of specific disposal sites and for ensuring that ocean disposal would not be detrimental to navigation or pollute adjacent beaches (Williams and Duane, 1974).
Materials including garbage, city refuse, cellar dirt (natural rock and soil excavated during building construction), floatable materials, and sediments derived from dredging during the maintenance, deepening and construction of new channels in New York Harbor, were dumped at specific locations in the New York Bight Apex. Records indicate that approximately six locations were selected to receive this wide range of materials. As the material accumulated at these locations, the sites were relocated farther seaward where increased water depths alleviated concerns of potential navigation threats posed by accumulation of materials.
Hydrographic data spanning the period from 1845 to 1934 revealed that mounds of material were being formed in the general area of the submerged Hudson Shelf Valley (Christiaensen Basin), the Ambrose Light Station (Diamond Hill), and the Scotland Light Buoy. By 1914, shoaling at one of the sites reserved for dredged material and cellar dirt became a critical factor in the decision of the Supervisor of New York Harbor to separate the site usages and thus segregate the material being disposed at each site.
From 1914 until 1977, when the U.S. Environmental Protection Agency designated an interim ocean dredged material disposal site, the general area reserved specifically for a "mud dumping ground" was defined as a point not less than 7 nautical miles bearing 120° from Sandy Hook Light at Latitude 40° 23'48" N and Longitude 73° 51'21" W (Pararas-Carrayannis, 1973). The boundary coordinates of the interim site that became the MDS, were:
40° 23'48" North Latitude, 73° 51'28" West Longitude
40° 21'48" North Latitude, 73° 50'00" West Longitude
40° 21'48" North Latitude, 73° 51'28" West Longitude
40° 23'48" North Latitude, 73° 50'00" West Longitude
During those sixty-three years of disposal it is estimated that more than 200 million cubic yards of dredged material were deposited there. An analysis of bathymetric change from 1936 to 1995 shows that significant mounding occurred in the area, with a net volume increase of 190 million cubic yards (mcy) (Figure 5). Although open ocean bathymetric surveys are subject to large potential errors, this volume change indicates an average of 3.2 mcy of dredged materials per year were disposed.
The interim site was officially designated as a dredged material ocean disposal site in 1984. From 1976 to 1997, when more reliable disposal volume records were kept, approximately 115 million cubic yards of dredged sediment were disposed within the boundaries of the 2.2 square nautical mile (sq. nmi) MDS. The composition of this material varied from the coarser fraction of "one-man stone" and "derrick stone" to the finer grained material of sand, silt and clay. The wide variety of bottom sediment types supported a diverse ecosystem. Since mid-1991 the larger stones have been directed to artificial reef sites, increasing the life of the site for the sands and silts more commonly disposed at the MDS.
Establishment of the HARS
An effort to expand the MDS was started in September 1994 when the United States Environmental Protection Agency (USEPA) began preparing a Supplemental Environmental Impact Statement (SEIS). The study area was initially comprised of an 18 sq. nmi section that included and surrounded the MDS. The area was enlarged in October 1995 to 23 sq. nmi to encompass areas of the Apex which had been previously impacted by historic dredged material disposal.
Because of concerns about contaminants associated with some dredged materials, many environmental and citizens groups sought an end to ocean dumping of dredged material. To address these concerns, a July 24, 1996 letter (The 3 Party Letter), signed by EPA Administrator Carol Browner, Secretary of Transportation Frederico Pena, and Secretary of the Army Togo D. West, Jr., to several U.S. Congressional Representatives from New Jersey, called for the closing of the MDS and the establishment of a remediation area.
In September 1997, the USEPA de-designated and terminated the use of the MDS and simultaneously redesignated the site and surrounding areas that had been used historically as disposal sites for dredged materials as the HARS (40 CFR Sections 228.15(d)(6); see 62 Fed. Reg. 46142 (August 29, 1997); 62 Fed. Reg. 26267 (May 13, 1997)). The HARS is managed to reduce impacts of historical disposal activities at the site to acceptable levels in accordance with 40 CFR Sections 228.11(c). The need to remediate the HARS is supported by the presence of toxic effects, dioxin bioaccumulation exceeding Category 1 levels in worm tissue, as well as TCDD/PCB contamination in area lobster stocks (proposed dredged sediment is determined to be Category 1 if test results indicate no unacceptable toxicity or bioaccumulation in test systems). Although individual elements of those data did not establish that sediments within the HARS were imminent hazards to the New York Bight Apex ecosystem, living resources, or human health, the collective evidence presented cause for concern, and justified the need for remediation. Further information on the conditions in the Study Area and the surveys performed may be found in the Supplemental Environmental Impact Statement (USEPA, 1997).
The HARS designation identified an area in and around the MDS which had exhibited the potential for adverse ecological impacts. The HARS is being remediated with dredged material that meets current Category 1 standards and does not cause significant undesirable effects including through bioaccumulation. This dredged material is referred to as "Material for Remediation" or "Remediation Material.”
The HARS, which includes the 2.2 square nautical mile area of the MDS, is an approximately 15.7 square nautical mile area located approximately 3.5 nautical miles east of Highlands, New Jersey and 7.7 nautical miles south of Rockaway, New York. When determined by bathymetry that capping is complete, the USEPA will initiate any necessary rulemaking to de-designate the HARS. The HARS includes the following three areas:
Priority Remediation Area (PRA): An approximately 9.2 square nautical mile area (Figure 7) to be remediated with at least 1 meter of Remediation Material. The PRA encompasses the area of degraded sediments as described in greater detail in the SEIS.
Buffer Zone: An approximately 5.7 square nautical mile area (0.27 nautical mile wide band around the PRA) in which no placement of the Material for Remediation will be allowed, but may receive Material for Remediation that incidentally spreads out of the PRA.
No Discharge Zone: An approximately 1.0 square nautical mile area in which no placement or incidental spread of Material for Remediation is allowed.
The designation of the HARS in September 1997 allowed the beginning of remediation of contaminated dredged materials dumped prior to modern environmental regulations. Standardized chemical and biological testing of sediments from proposed dredging projects is conducted to determine suitability of material for HARS remediation. Only sediments classified as Category I are permitted for placement at the HARS. During the period from HARS designation to 31 December 2008, 61 dredging projects involving ~36 million cubic yards (mcy) of dredged material have been used to remediate the HARS. In addition, approximately 2.4 mcy of sand were used to cap the 1997 Category II project at the former MDS from 21 August 1997 to 18 January 1998. A Site Management and Monitoring Plan was developed prior to HARS designation to provide guidelines for monitoring of HARS remediation activities. A revised SMMP is presently being prepared for public review and comment in 2009.
Monitoring Activities at the HARS
The Site Management and Monitoring Plan (SMMP) for the HARS was developed according to the provisions of 40CFR part 228 for management of ocean dredged material disposal sites. The SMMP provides guidelines to monitor placement activities, assess the progress of remediation, analyze environmental conditions, and address potential environmental issues. The SMMP specifies three tiers of monitoring, with different criteria for implementation of monitoring activities associated with each tier. The nine Priority Remediation Areas (PRAs) within the HARS are prioritized based on the perceived degree of sediment degradation; i.e. PRA #1 was considered to pose the greatest potential for environmental impacts, and was slated for remediation first, followed by PRA#2, and so on. An updated SMMP that accounts for technological improvements since 1977, changes in placement procedures, and past remediation activities, is being reviewed for final adoption in 2008. The following sections describe the various systems and methods used to monitor the progress of HARS remediation.
Availability of Monitoring Reports
Table 2 lists reports associated with HARS monitoring activities and allows direct downloading of most reports. A hard copy of the report listed in Table 2 that is not available in PDF format is available by request. Supplemental technical reports indirectly associated with the HARS are listed at the end of this report.
Tracking Dredged Material Placement
Each dredging project approved for HARS remediation is considered a separate remediation project. The estimated volume of dredged material, sediment characteristics, and the status of past and present remediation at the HARS, are used to develop placement grids within one of the nine PRAs within the HARS. Grids are located far enough from the HARS boundaries to ensure that water quality guidelines are not exceeded during placement. Grids are developed to provide from 0.5 to 2.5 feet of cover across the area of the grid. Grids are divided into sequentially numbered cells, with placement scheduled to occur in a manner that will produce uniform coverage, depending on the characteristics of the dredged material (coarser materials do not spread out much on the bottom) (Figure 8). A state-of-the-art electronic monitoring system (ADISS) is used to track the position of dredged material scows being transported to the HARS.
ADISS, Automated DIsposal Surveillance System, is a DGPS (Differential Global Positioning System) based positioning and vessel draft monitoring system developed by Science Applications International Corporation (SAIC) (Figure 9). The heart of the system is a "black box" recorder mounted on each scow used to transport dredged materials to the HARS. The "black box" digitally records the time and position of scows as they are loaded with dredged materials at the dredging site based on the increase in scow draft recorded by a pressure sensor on the scow. Throughout each trip to the HARS, the ADISS system records the time, position, and draft of the scow. During maintenance dredging projects, that usually involve high water content sediments, a scow bin-level sensor is also used to help detect potential leaks of dredged material from the scows. As the HARS is approached, the frequency of data recording increases. At the time of placement, when the scow draft rapidly decreases as dredged materials are emptied, the position and time information is transmitted through a wireless transmission system, which in turn transmits the data to a computer for eventual viewing on a website. The ADISS system continues to record the time, position, and draft data past the initial scow door opening, during placement, and throughout the trip back to the dredging site. ADISS data are downloaded from scows after completion of placement, processed, and eventually input to the Disposal Analysis Network for the New York District (DAN-NY) computer system. DAN-NY is a GIS-based system used to manage HARS placement and monitoring data.
Scow navigation capability aboard towing vessels is another feature of the ADISS system. The ADISSWay component allows USACE certified Dredged Material Inspectors (DMIs) and vessel captains, to view the position of scows on a laptop computer throughout the trip to the HARS. Placement grids designated for each project are projected on a map of the inner New York Bight and NY Harbor region. DMIs can zoom in or out of the map view to observe the position of the scow relative to landmarks, navigation aids, and in particular, the grid cell scheduled for placement. A digital version of the USACE Transportation and Placement Log form is included with the system, which the inspector completes during each trip to the HARS. ADISS locations of placement events associated with the projects are illustrated in (Figure 10).
Although estimation of remediation progress can be made based on the size of each project grid and the volume of material placed, bathymetric surveying is the only quantitative way to document the thickness of cover associated with dredged material placement. Bathymetric surveys conducted since HARS designation have included the entire HARS, and surveys of one or several PRAs. Complete, or nearly complete, HARS surveys were conducted in the fall of 1998 and the winter of 2000, and the summers of 2002, 2004, 2005, 2006, 2007, and 2008. Surveys of individual PRAs have been conducted in 1998, 1999, 2000, 2003, and 2007. The baseline survey used to determine remediation progress at the HARS was conducted in 1995, although the more detailed survey of PRAs 1-3 conducted in 1998 has been used as the “baseline” for comparison with later surveys. Complete HARS surveys conducted in 2000 and 2002 provide baseline data for areas of the HARS that had not received remediation materials pre-dating the surveys. Table 1 lists the bathymetric surveys conducted at the HARS since designation. Reports on the data, if available, may be downloaded from Table 2.
Sidescan Sonar Surveys
Sidescan sonar is analogous to bathymetric surveying in that sound is transmitted from a survey vessel, bounces off the bottom, and returns to a receiver. The time for the sound to make the round trip is proportional to the distance, which equates to water depth. However, sidescan sonar uses sound to obtain the distance and reflective characteristics of bottom features, providing images that look like photographs. Sidescan sonar is considered a qualitative tool, providing the general location and morphology of bottom features, but usually without the precision of bathymetric surveys. When sidescan and multi-beam bathymetric surveys are conducted concurrently, exquisite detail of the bottom may be documented. Past side-scan sonar surveys at the HARS have been used to identify rock outcrops, large sedimentary bedforms, and shipwrecks. Since HARS designation, a side-scan sonar survey has been conducted for PRA1-3 (Table 2).
The REMOTS® (Remote Ecological Monitoring Of The Seafloor) is a trademarked sediment profile imagery (SPI) system. SPI systems utilize a prism that penetrates the seafloor, allowing photography of nearly undisturbed vertical sections of bottom sediments. The REMOTS® apparatus also includes a camera for obtaining plan-view photographs of the bottom at each station analyzed. SPIimages are most useful in delineating the contact between recently placed dredged materials and older bottom sediments. SPI images can also document infaunal organisms, gas bubbles, and sediment grain size. The rapid deployment capability of the SPI systems allow large areas to be surveyed in a relatively short amount of time. SPI imagery has been particularly useful in mapping the dredged material "footprint" associated with past dredged material placement. Twelve SPI (REMOTS®) surveys have been conducted at the HARS (Table 2).
Sediment Coring Surveys
Cores provide a vertical sample of the sediments comprising the ocean bottom. Since sediments are deposited vertically, with the oldest sediments at the bottom, cores provide a record of the sedimentation history at a sampling station. Cores reveal differences in color and grain size that are associated with a sedimentary unit. Deposition of fine-grained dredged material on top of sandy sediments usually produces a well-defined interface; i.e. darker colored dredged materials overlying lighter colored sandy sediments. In addition to color and grain-size characteristics of sediments, cores may be used to determine geotechnical and chemical properties of sediments contained within, and provide calibration and verification data for seismic surveys. Six sediment coring surveys have been conducted at the HARS, all associated with the 1997 and/or 1993 Category II capping projects (Table 2).
Seismic data are used to map the sedimentary units beneath the ocean surface based on the sound reflection and transmission characteristics of the sediments. Although cores provide discrete samples of sub-surface sedimentary information, their time and expense limits the practical number of sample stations. Seismic data allow analysis of large areas of the sub-surface without physically collecting sediment samples, although cores are often used to calibrate and verify seismic data. A seismic survey of the 1997 Category II capping project was conducted in April 1998 (Table 2). Seismic surveys of the 1993 and 1997 capping projects were conducted in 1998 and 2003 (Table 2).
Physical Oceanographic Data Collection
In addition to the more typical monitoring work, usually involving mapping of some kind, physical oceanographic data have been collected at the HARS to provide a better understanding of the waves, currents, and potential for sediment suspension and transport. Instrumented pods developed by SAIC have been deployed on several occasions. The pods are equiped with acoustic doppler current profilers, electromagnetic current meters, optical backscatter sensors (for detecting suspended sediment), and pressure transducers (waves and tides). Some limited data sets have been collected during the testing phases of the equipment. Some of these results are illustrated in (Figure 11) and (Figure 12) A report of physical oceanographic data collected in 2000 and 2001 is available from Table 2.
Prior to designation of the formal HARS boundaries, one of the tools used by EPA to determine areas of degraded sediments requiring remediation was the use of the amphipod toxicity test. This is one of the tests used in our ocean placement testing program when we analyze proposed dredged sediment for use as Remediation Material. Toxicity surveys conducted at the HARS are used to gauge the effectiveness of the remediation effort through comparison to EPA's original toxicity results, as well as to determine what areas may need additional remediation sediment. The first toxicity survey conducted since the EPA survey was initiated in September of 2000. Additional toxicity surveys were conducted in 2002 and 2005. Reports from these surveys are available from Table 3. In general, sediment toxicity at the HARS is lower at almost all stations than was observed at the same stations prior to HARS designation.
By comparing recent bathymetric surveys with past surveys, the depth of remediation material at the HARS can be analyzed. Figure 13 shows the remediation status as of July, 2008, based on a comparison between the 1998 “baseline” survey and the full HARS survey conducted in July of 2008. Almost all of HARS PRA #1 has been capped with at least 1m of clean dredged material. Most of HARS PRA #2 has also achieved the minimum 1m cap thickness, along with areas within PRA #3. Some minor portions of PRA #4 have been covered with at least 1m of clean dredged material.
(Note: The 1998 “baseline” bathymetric survey only covered PRAs 1-3. Remediation status of PRAs 4-9 will be compared with later, full-HARS bathymetric surveys that pre-date remediation activities there.)
Point of Contact
Stephen C. Knowles, Ph.D.
Dredged Material Management Section
U.S. Army Corps of Engineers, NY District
26 Federal Plaza
New York, NY 10278-0090
Phone: (917) 790-8538
Fax: (212) 264-1463