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Construction in the coastal zone: A potential use of waste materials
Marine Geology, 18(1975): 1--15 ©Elsevier Scientific Publishing Company, Amsterdam - - P r i n t e d in The Netherlands
CONSTRUCTION IN THE COASTAL WASTE MATERIALS
ZONE: A POTENTIAL
USE OF
S. JEFFRESS WILLIAMS and DAVID B. DUANE
Geology Branclt U.S. Army Coastal Engineering Research Center, Ft. Belvoir, Va (U.S.A.) (Received July 4, 1974; accepted August 21, 1974)
ABSTRACT Williams, S. J. and Duane, D. B., 1975. Construction in the coastal zone: a potential use of waste materials. Mar. Geol., 18: 1--15.
The Inner New York Bight, at the head of the Hudson shelf channel, has been the site for ocean disposal of various waste products since at least 1888. Natural channel-like bathymetry expressed in 1845 is today a series of hills rising to within 12 m (40 ft.) of the water surface superimposed upon a broad lobate mound. This topographic inversion created over the past nine decades is attributable to disposal of materials (soil, sand, and stone) of varying composition generated during construction in the New York metropolitan area. Data indicate approximately 765 ' 106 m 3 (1 • 109 yd 3 ) of waste has been dumped in that region from 1888 to 1934. Isopach maps, sea-floor profiles, seismic records, and vibratory cores show much of the fill has remained in place in spite of b o t t o m currents of approximately 25 cm/sec (0.5 knot) and a wave climate of H s = 0.76 m (2.5 ft.); T = 5--15 sec. Man-made islands proposed for the inner continental shelf for siting power, port, or recreational facilities will use large volumes of stable material for core fill, which could be waste materials such as those described. Effective regional coastal-zone planning should recognize uses for past and future waste material as such practices would conserve sand and gravel resources for other high-volume needs (shoreline nourishment and protection and construction aggregate) and alleviate some of the site-selection problems in land disposal of waste.
INTRODUCTION I n all a r e a s o f t h e U n i t e d S t a t e s t h e r e a r e c o n f l i c t s b e t w e e n p e r s o n s w i s h ing to maintain and preserve remaining wild-natural environments and others w h o s e e c o n t i n u e d e x p a n s i o n a n d d e v e l o p m e n t as a n e c e s s i t y f o r m a i n t a i n i n g a h i g h n a t i o n a l s t a n d a r d o f living. T h i s c o n f l i c t o f d e s i r e s is e s p e c i a l l y a c u t e a l o n g c o a s t a l m a r g i n s w h e r e p o p u l a t i o n d e n s i t y is g r e a t e s t a n d t h e e c o l o g i c a l b a l a n c e is p a r t i c u l a r l y v u l n e r a b l e t o m a n - i n d u c e d c h a n g e . I n addition, increasing development along the shoreline and inner continental s h e l f is f o r e c a s t t o a c c o m m o d a t e p r e d i c t e d i n c r e a s e d u s e o f b u l k s e a b o r n e trade with foreign countries to supplement dwindling domestic resources.
The highly urbanized and densely populated northeast region of the United States has especially been cited as needing new or expanded offshore facilities at present or by the end of the 20th century. The situation in the New York metropolitan area is especially acute concerning the need for such facilities as: (1) a centrally located airport to accommodate predicted increase in air travel and to relieve congestion at the three existing airports where excess noise and air pollution affect large segments of adjacent populations; (2) a mooring and transshipping facility for transfer of crude oil and liquified natural gas from deep draft tankers to area refineries; (3) nuclear power generating plants to supplement supplies of much needed electric power; (4) a desalinization plant to offset dwindling fresh-water resources in New York City and on Long Island; and (5) a central waste processing facility where organic wastes could be reduced and hard wastes processed for recycling. Each of these needed facilities would require large construction sites remote from centers of population. Furthermore, the construction of such facilities might generate considerable c o m m u n i t y opposition because of environmental concern and recent land-use policies intended to control urban growth. In the New York area any of these factors would probably prevent construction of such facilities within existing city limits. However, alternative suggestions have been made to use the shallow-water, nearshore inner-continental shelves as construction sites for such facilities enumerated above. Studies conducted by private industry and government agencies have investigated potential sites and facility configurations needed to satisfy forecast requirements along the Atlantic, Gulf and Pacific coasts of the United States. Kelly (1973) summarizes the recent U.S. Army Corps of Engineers study of deep-water ports to accommodate present and future very large crude petroleum carriers (VLCC's) and notes the New York-northern New Jersey shelf region is deemed to have a high potential as site for such a facility in the North Atlantic region. Lerner (1971) summarized an offshore airport feasibility study which incorporated an artificial-island design for the shelf approximately 7.5 km (4 n.m.) south of Long Beach, Long Island. Also included in the report summarized by Lerner are plans to incorporate other facilities such as a deep-water terminal, a fuel storage depot and a nuclear power plant as future needs require. Nutant (1973) presented results of environmental assessments for offshore floating nuclear power plants intended for use along the Atlantic and Gulf coasts. Many of Nutant's conclusions would still apply if the power systems were fixed to stable islands rather than floating behind protective breakwaters. In any of the technical analyses made on the feasibility of constructing offshore islands the cost and availability of suitable fill material is a major factor in determining the engineering design, which in turn, dictates the project costs. The modern effects of technologies pursued over the last 10,000 years for the advancement of civilization are evident in the peoples and cities of the world as well as in the transportation networks which bind them and
Fig.lA. ERTS-1 satellite imagery (band MSS 5) taken 16 August 1972 showing two slicks resulting from disposal of wastes in New York Bight.
B Fig. lB. Relationship of the two slicks (see Fig. 1A) to the fivecontemporary disposal areas shown by crosses.
TABLE I Time schedule for ocean disposal of wastes in New York Bight for 16 August 1972" Sewersludge (h)
Cellar dirt (h)
Industrialacid (h)
Dredge spoil (h)
0925 1018 1029 1215 1240 1705 1815 1837
0110
0145 1350
0435 0715 0830 09]5 1050 1153 1220 1345 1400 1450 1730 2305
*Data for this table obtained from permit files of the Supervisor of New York Harbor, New York District, Corps of Engineers. Time is Eastern Daylight SavingsTime (EDT). their activities together. These technologies and the activities spawned f r o m t h e m have created problems of environmental pollution as a result of waste disposal. In the New York Bight area waste-disposal activities are n u mer o u s (Table I) and often clearly visible (Fig.l). However, once below the sea surface, the visibility of those activities is lost, and oft en their existence is forgotten. This paper is intended to show that large volumes of waste materials are available f r om the ocean b o t t o m in the New York Bight area for construction purposes. This material may be available at a potentially lower unit cost and with possible environmental benefits. GEOMORPHOLOGY--GEOLOGY The Inner New York Bight (Fig.2) is underlain by Cretaceous and Tertiary Coastal Plain strata which dip and thicken to the southeast. T h e y consist primarily of glauconitic sands and gravel interbeded with silty sands. Most o f the region experienced significant subaerial erosion during Pleistocene times as a result of processes associated with the continental ice sheets which repeatedly covered the terrain to the north. The Hudson Channel (Fig.3) is one of the more p r o m i n e n t features on the shelf in this area and represents one of several major rivers which were drow ned during the Holocene marine transgression. However, unlike ot her channels in the region (McMaster and Ashraf, 1973; Williams, 1974), the Hudson has maintained its characteristic periglacial m o r p h o l o g y and has been only partially filled with outwash sand and gravel which was spread across the shelf by southward flowing melt water streams which issued from the ice fronts. It is also significant t ha t complete filling of the Hudson shelf channel by marine and estuarine sediment has n o t taken place during the past 11,000 years.
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A second prominent geomorphic feature peripheral to the Hudson inner shelf channel is Shrewsbury Rocks (Fig.3) which is an elongate shoal projecting about 15 km (8 n.m.) northeast from the New Jersey coast out to where it is truncated at the 27-m (90-ft) contour by the Hudson Channel. Shrewsbury Rocks is actually a series of shoals exhibiting about 5 m (15 ft.) of relief with the adjacent sea floor and in apparent strike alignment (about N60 ° E) with Coastal Plain strata on land. Collection of field data utilized in this report was made as part of a Coastal Engineering Research Center research program to study the geologic
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(From Williams and Duane, 1974. )
and engineering character of the U.S. inner continental shelf apropos the Corps of Engineers mission. Data include 824 km (445 n.m.) of continuous seismic reflection profiles (CSRP) and 61 vibratory cores (average length: 3.3 m; 10.7 ft.) of the subbottom sediment (Fig.2). CSRP records show that several strong acoustic reflectors, corresponding to Coastal Plain strata, do crop out on the sea floor in the vicinity of Shrewsbury Rocks while on the shelf to the south the strata are covered by variable thicknesses of Pleistocene-Holocene sediments. Cores in the Shrewsbury Rocks shelf region exhibit a relatively thin cover
of clean, medium-to-coarse, sand over either reddish brown silty sand and gravel or compact, glauconitic, sandy gravels (Williams and Duane, 1974). The sand and gravel blanketing this area is interpreted as residual detritus resulting from localized erosion by marine processes of the underlying Coastal Plain strata. The CSRP records and deep-foundation borings show that Pleistocene detritus in excess of 37 m (120 ft.) overlies the deeply eroded Coastal Plain surface of the shelf north from Shrewsbury Rocks to Rockaway Beach; similar data indicate that the inner shelf region south from Shrewsbury Rocks experienced only limited erosion during the Pleistocene. This contrasts with the reported relict nature of the topography and sediments for other parts of the Long Island--New Jersey shelf (McKinney and Friedman, 1970; Milliman et al., 1972; Frank and Friedman, 1973). Evidence is inconclusive regarding erosion of the Coastal Plain surface and subsequent deposition of sand and gravel being the direct result of glacial processes (Williams and Duane, 1974). However, the most significant agents in modifying this terrain were the ancestral Raritan, Passaic, East and Hudson Rivers. These rivers flowed east from New Jersey and south from New York and western Long Island Sound and converged in the Lower Bay (Fig.2). At least five buried channels, which may be Hudson distributaries, have been found to cross western Long Island (Williams, 1974). They predate the morainal formation of Long Island and were apparently significant in downcutting the Coastal Plain surface. The age relationship for these channels agrees with the conclusions of McMaster and Ashraf (1973) for the ages of buried channels underlying the eastern Long Island inner shelf. MATERIALS
The inner New York Bight has been the site for the ocean disposal of assorted wastes from the New York metropolitan area during the past almost nine decades (U.S. Army Corps of Engineers, 1915). The present authors have shown elsewhere (Williams and Duane, 1974} that the major physical evidence of this dumping operation are three circular sea-floor mounds in the Hudson Channel thalweg culminating as Castle Hill and the one mound forming Diamond Hill on the flat sea-floor apron immediately north of the channel (Fig.3). A bathymetric map of the same region based on 1845 survey data is depicted in Fig.4. It clearly shows the contrast between the natural Hudson Channel morphology and the present (modified) morphology shown in Fig.3. In 1845 the channel (Fig.4) was continuous for approximately 22.2 km (12 n.m.) from the shelf seaward of the 40-m (130-ft.) contour toward the Narrows separating Brooklyn and Staten Island. Other changes in shelf morphology between 1845 and 1934 appear to be slight except for the extension of Long Island and New Jersey barrier islands spits (compare Fig.3 and 4). On Long Island, Long Beach has accreted westward approximately 6.3 km (3.4 n.m.} and Rockaway Beach by 7.4 km (4 n.m.) while
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Sandy Hook, New Jersey, has grown north approximately 1.5 km (0.8 n.m.). Further growth of Sandy H o o k has been curtailed by dredging of the navigation channel immediately north of the spit. Net sea-floor changes in elevation within the area subject to ocean disposal, depicted in Fig.5, show that the areas of maximum sediment accumulation correspond to the Castle Hill region southeast of Scotland Light (> 15 m; 50 ft. fill) and to the Diamond Hill region (> 9 m; 30 ft. fill). The Castle Hill b o d y is elongate in a northwest direction parallel to the channel form. Dimensions of the fill b o d y are approximately 14.8 km (8 n.m.) long and 5.6 km (3 n.m.) wide. The protrusion to the southwest in the vicinity of Shrewsbury Rocks is judged not significant to probable
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F ig.5. Isopach m a p of Hudson Channel fillresulting from ocean waste disposal between 1845 and 1934. Isopach interval is 10 ft.,dash line is channel projection, crosses mark contemporary disposal sites. Note the close correspondence of m a x i m u m fillwith designated d u m p sites from 1903 to 1914. (From Williams and Duane, 1974.)
disposal practices as net changes could be attributed to a paucity of sounding data on the 1845 map for that area. Approximate volume estimates indicate that 765 million m 3 (one billion yd 3 ) of material is contained within the isopach boundary limits shown. Core data indicate materials from these sites are waste materials {Williams and Duane, 1974). Examination of historical records (U.S. Army Corps of Engineers, 1915) and use of interim bathymetric charts have provided a
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detailed chronological history of the growth of these morphologic features coincident to waste-disposal operations. Characteristics of CSRP records and sediment vibratory cores have shown that much of the fill is similar to indigenous shelf sediments, being of variable composition consisting mostly of clean sand and gravel and large "one-man and derrick" stones. The light dash lines in Fig.5 projecting east from Old Scotland Light correspond to ship tracks leading to the designated dump sites for the dates shown (U.S. Army Corps of Engineers, 1915). It is clear that the dump sites from 1903 to 1914 closely correspond to areas of maximum channel fill in the vicinity of Castle Hill. Boring-log descriptions (McClelland Engineers, 1963) verify that the Diamond Hill mound is composed of anthropogenic fill, however, no reference was found in official reports (U.S. Army Corps of Engineers, 1915) dating back to 1888 designating that specific region as a d u m p site. We judge the evidence to unequivocably indicate that Diamond and Castle Hills are waste materials accumulated as a result of disposal practices over the past nine decades. These early fill materials were generated by the excavation and construction underway during the growth and development of New York as both a metropolitan area and a major world seaport. A well documented example of one large-scale excavation project where the material was disposed in the ocean was the dredging, from 1900 to 1907, of the Ambrose navigation channel leading into the New York harbor. As a result of this single project approximately 38 • 106 m 3 (50 • 106 yd 3 ) of clean sand and gravel was removed from the sea floor in lower New York Bay and transferred and dumped in the Castle Hill area (Wigmore, 1909). Fig.6 shows three northeast--southwest oriented sea-floor profiles whose locations are shown on Fig.3 and 4. No doubt, some of the disparity between the 1845 and 1934 sea floor could be attributed to lack of accuracy in surveying, however, the net aggradation of the sea floor in profiles A and B is unmistakable. The lack of significant sea-floor change along profile C, which passes seaward of the isopached disposal area reported on here further indicates that at least the sand, gravel and stone fractions of the fill noted along profiles A and B are relatively stable in the present oceanographic environment and have shown minimal movement southward toward the deeper parts of the Hudson Channel. Based on the data presented and discussed above we judge the fill to be reasonably stable and that the material has remained in the immediate d u m p zone. Sea-floor currents in the inner New York Bight at these d u m p sites can exceed 25 cm/sec (0.5 knot) (Cok et al., 1973) and the wave climate (with a 50% probability of occurrence) is H s = 0.76 m (2.5 ft.); T = 5--15 sec (Harris, 1972). These construction waste products similar in character to the natural ocean b o t t o m are considered environmentally neutral. However, the presence of natural fine-grained sediments (very fine sand, silt and clay) mixed with assorted pollutants in the contemporary d u m p areas peripheral to Castle and Diamond Hills has been documented by Gross (1972) and
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Pararas-Carayannis (1973). The effects of these pollutants on the chemical, physical and biological characteristics of the shelf in the immediate d u m p zones are varied; presence of these materials in the construction waste must be considered by any shelf usage. DISCUSSION
Because of the demonstrated need for several new major facilities in the New York area and because of the serendipitous accumulation of an estimated 765 million cubic meters of fill it appears t h a t it may be economically feasible to construct an offshore, multipurpose, man-made island on the sea-floor seaward of the lower New York Bay and use the Hudson Channel fill as a major construction component (considering water depth it is technologically feasible to dredge-up this material). Use of offshore areas is already the subject of study. For example, a comprehensive feasibility study and proposal (Sea Island Project) to build one or more offshore multipurpose islands on the North Sea shelf off the coast of The Netherlands has been completed (Bos Kalis-Westminster Group, 1973). The Sea Island Project involves use of traditional land-reclamation practices applied to a shallow-water marine environment. The island body, with sand as the principal constituent, is to be surrounded by a,protective seawall consisting of concrete blocks or caissons (Fig.7). The Bos Kalis-
12
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/ m Fig.7. Two possible design profiles for a shelf-sited man-made island. (Courtesy of Ocean Industry Magazine, 1973, 4:187--194).
Westminster study concludes that in any case, ultimate island size and final number of component islands would depend on the intended usage, further emphasizing that construction costs per unit are drastically decreased for large islands with areas about 1200 hectares (3000 acres) (note: 1 hectare = i • 104 m 2 ) versus smaller ones with areas about 50 hectares (125 acres). Stigter {1973) has shown that the unit cost per square foot of smaller islands might be $12, with 90% of the cost incident to seawall construction. For an island of 1200 hectares the cost would be $3 per sq. ft. with approximately 50% attributable to seawall costs. Because a significant proportion of the total cost of island construction involves placement of sand fill for side slopes and seawall construction (which are not linearly proportional to island area) the unit area cost reductions for large islands as compared to small islands are dramatic. For the North Sea shelf region artificial island construction is presently feasible (Stigter, 1973); factors dictating the practicality of building such islands in other shelf areas, such as the inner New York Bight will vary based on economic, environmental, legal and engineering considerations.
13
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However, based on preliminary study o f this region (Kelly, 1973; Williams and Duane, 1974) it is judged there are certain advantages in having an island site situated on or south of Shrewsbury Rocks off northern New Jersey (Fig.8). On either the east or the west flank of the Hudson Channel the island proper would fit the following criteria: (1) it would be in approximately 24 m (80 ft.) of water; (2) 11--15 km (6--8 n.m) from the maximum accumulation of fill; (3) the sea floor south of Shrewsbury Rocks, veneered with sand, is underlain at shallow depths by compact Coastal Plain strata thus providing a suitable foundation for construction (U.S. Geol.
14 Surv., 1967); (4) such a site would be near shipping lanes and land-based facilities making transfer of inbound or o u t b o u n d materials more economical; (5) adjacent to the naturally deepened Hudson Channel which in this region is in excess of 37 m {120 ft.) deep and which would a c c o m m o d a t e even the largest predicted vessels with a minimum of initial and periodic maintenance dredging; and (6) the site would be b e y o n d the 3°mile limit of state jurisdiction but within the 12-mile territorial limit. Further, based upon economic and world trade factors this general region has also been indicated as a potential site for a VLCC facility for the mid-Atlantic region (Kelly, 1973). CONCLUSION Construction of a multipurpose island on the shallow shelf off n o r t h e r n New Jersey, to provide space for facilities needed along the North Atlantic coast, could, through proper processing and management, utilize waste materials as building blocks for island construction. Waste materials presently comprising Castle and Diamond Hills could be used for initial construction; similar waste materials, rather than be discarded w i t h o u t plan, could be used for island expansion or new construction. Use of the Hudson Channel fill as a major c o m p o n e n t in an offshore island project would also conserve land-based and offshore sand and gravel resources for other needs, reduce construction costs by reducing transportation costs, and reduce the environmental concern which might result from removal of the large volumes of alternative fill that would be needed if such a project were built using an alternate design. ACKNOWLEDGEMENTS Review o f early drafts of this manuscript by M. Grant Gross (National Science F o u n d a t i o n ) and G. Pararas-Carayannis (CERC) and discussions with colleagues M. E. Field and E. P. Meisburger were helpful and appreciated. Data presented were collected as part of the civil works research program o f the U.S. A r m y Corps of Engineers through the Coastal Engineering Research Center. Permission of the Chief of Engineers to publish this paper is appreciated; however, conclusions of this paper are the authors' and should n o t be construed as official D e p a r t m e n t of the A r m y position unless so designated by o t h e r authorized documents. REFERENCES
Bos Kalis-Westminster Group, 1973. Building a multipurpose island in the sea, Ocean Ind., 4: 187--194. Cok, A. E., Swift, D. J. P., Shepard, E. and Reynolds, R. J., 1973. Sediment unmixing in the New York Bight area, (abs.) Geol. Soc. Am., Progr. Abs., 5(2): 150. Frank, W. M. and Friedman, G. M., 1973. Continental Shelf sediment off New Jersey, J. Sed. Pet., 43: 224--237.
15 Gross, M. G., 1972. Geologic aspects of waste solids and marine waste deposits, New York metropolitan region. Geol. Soc. Am. Bull., 83: 3163--3176. Harris, D. L., 1972. Wave estimates for coastal regions. In: D. J. P. Swift, D. B. Duane and O. H. Pilkey (Editors), Shelf Sediment Transport: Process and Pattern. Dowden, Hutchinson and Ross, Stroudsburg, Pa., pp. 99--125. Kelly, J. L., 1973. Offshore terminals and the national perspective. Mar. Tech. Soe. Proc. 9th Ann. Conf., pp.9--18. Lerner, L., 1971. New York offshore airport feasibility study. (Exec. Brief. Saphier, Lerner, Schindler Environetics, 25 pp., unpublished.) McClelland Engineers, 1963. Fathometer survey and foundation investigation Ambrose Lt. Station New York Harbor Entrance, (Report No. 63-162-1, unpublished.) McKinney, T. F. and Friedman, G. M., 1970. Continental-shelf sediments of Long Island, New York, J. Sed. Pet., 40: 213--248. McMaster, R. L. and Ashraf, A., 1973. Subbottom basement drainage system of Inner Continental Shelf off southern New England. Geol. Soe. Am. Bull., 84: 187--190. Milliman, J. D., Pilkey, O. H. and Ross, D. A., 1972. Sediment of the continental margin off the eastern United States. Geol. Soc. Am. Bull., 83: 1315--1333. Nutant, J. A., 1973. An environmental assessment of floating nuclear plants. Mar. Tech. Soc. Proc. 9th Ann. Conf., pp.367--374. Pararas-Carayannis, G., 1973. Ocean dumping in the New York Bight, an assessment of environmental studies. U.S. Army Coast Eng. Res. Center Tech. Memo., 3 9 : 1 5 9 pp. Stigter, G., 1973. The building of islands in the open sea offers possibilities for the industrial development in the near future. Mar. Tech. Soc. 9th Ann. Conf., Preprint, 7 pp. U.S. Army Corps of Engineers, 1973. North Atlantic Coast Deepwater Port Facilities Study, U.S. Army Corps of Engineers District, Philadelphia. (unpublished). U.S. Army Corps of Engineers, 1915. Annual Report of the Chief of Engineers, 1: 1634--1648. U.S. Geological Survey, 1967. Engineering Geology of the Northeast Corridor, Washington, D.C. to Boston, Massachusetts-Coastal Plain and Surficial Deposits, Folio 1-514 A, B, C, U.S.G.S., Washington, D.C. Wigmore, H. L., 1909. Memorandum on dredging work in Ambrose Channel. U.S. Army Prof. Memo., Engineer Bur., 1: 57--62. Williams, S. J. and Duane, D. B., 1974. Geomorphology and sediments of the Inner New York Bight Continental Shelf. U.S. Army Coast Eng. Res. Center Tech. Memo., 45. Williams, S. J., 1974. Geomorphology and sediments of the Long Island Atlantic Inner Continental Shelf. U.fi Army Coast Eng. Res. Center. Tech. Memo. (in preparation.)
CONSTRUCTION IN THE COASTAL WASTE MATERIALS
ZONE: A POTENTIAL
USE OF
S. JEFFRESS WILLIAMS and DAVID B. DUANE
Geology Branclt U.S. Army Coastal Engineering Research Center, Ft. Belvoir, Va (U.S.A.) (Received July 4, 1974; accepted August 21, 1974)
ABSTRACT Williams, S. J. and Duane, D. B., 1975. Construction in the coastal zone: a potential use of waste materials. Mar. Geol., 18: 1--15.
The Inner New York Bight, at the head of the Hudson shelf channel, has been the site for ocean disposal of various waste products since at least 1888. Natural channel-like bathymetry expressed in 1845 is today a series of hills rising to within 12 m (40 ft.) of the water surface superimposed upon a broad lobate mound. This topographic inversion created over the past nine decades is attributable to disposal of materials (soil, sand, and stone) of varying composition generated during construction in the New York metropolitan area. Data indicate approximately 765 ' 106 m 3 (1 • 109 yd 3 ) of waste has been dumped in that region from 1888 to 1934. Isopach maps, sea-floor profiles, seismic records, and vibratory cores show much of the fill has remained in place in spite of b o t t o m currents of approximately 25 cm/sec (0.5 knot) and a wave climate of H s = 0.76 m (2.5 ft.); T = 5--15 sec. Man-made islands proposed for the inner continental shelf for siting power, port, or recreational facilities will use large volumes of stable material for core fill, which could be waste materials such as those described. Effective regional coastal-zone planning should recognize uses for past and future waste material as such practices would conserve sand and gravel resources for other high-volume needs (shoreline nourishment and protection and construction aggregate) and alleviate some of the site-selection problems in land disposal of waste.
INTRODUCTION I n all a r e a s o f t h e U n i t e d S t a t e s t h e r e a r e c o n f l i c t s b e t w e e n p e r s o n s w i s h ing to maintain and preserve remaining wild-natural environments and others w h o s e e c o n t i n u e d e x p a n s i o n a n d d e v e l o p m e n t as a n e c e s s i t y f o r m a i n t a i n i n g a h i g h n a t i o n a l s t a n d a r d o f living. T h i s c o n f l i c t o f d e s i r e s is e s p e c i a l l y a c u t e a l o n g c o a s t a l m a r g i n s w h e r e p o p u l a t i o n d e n s i t y is g r e a t e s t a n d t h e e c o l o g i c a l b a l a n c e is p a r t i c u l a r l y v u l n e r a b l e t o m a n - i n d u c e d c h a n g e . I n addition, increasing development along the shoreline and inner continental s h e l f is f o r e c a s t t o a c c o m m o d a t e p r e d i c t e d i n c r e a s e d u s e o f b u l k s e a b o r n e trade with foreign countries to supplement dwindling domestic resources.
The highly urbanized and densely populated northeast region of the United States has especially been cited as needing new or expanded offshore facilities at present or by the end of the 20th century. The situation in the New York metropolitan area is especially acute concerning the need for such facilities as: (1) a centrally located airport to accommodate predicted increase in air travel and to relieve congestion at the three existing airports where excess noise and air pollution affect large segments of adjacent populations; (2) a mooring and transshipping facility for transfer of crude oil and liquified natural gas from deep draft tankers to area refineries; (3) nuclear power generating plants to supplement supplies of much needed electric power; (4) a desalinization plant to offset dwindling fresh-water resources in New York City and on Long Island; and (5) a central waste processing facility where organic wastes could be reduced and hard wastes processed for recycling. Each of these needed facilities would require large construction sites remote from centers of population. Furthermore, the construction of such facilities might generate considerable c o m m u n i t y opposition because of environmental concern and recent land-use policies intended to control urban growth. In the New York area any of these factors would probably prevent construction of such facilities within existing city limits. However, alternative suggestions have been made to use the shallow-water, nearshore inner-continental shelves as construction sites for such facilities enumerated above. Studies conducted by private industry and government agencies have investigated potential sites and facility configurations needed to satisfy forecast requirements along the Atlantic, Gulf and Pacific coasts of the United States. Kelly (1973) summarizes the recent U.S. Army Corps of Engineers study of deep-water ports to accommodate present and future very large crude petroleum carriers (VLCC's) and notes the New York-northern New Jersey shelf region is deemed to have a high potential as site for such a facility in the North Atlantic region. Lerner (1971) summarized an offshore airport feasibility study which incorporated an artificial-island design for the shelf approximately 7.5 km (4 n.m.) south of Long Beach, Long Island. Also included in the report summarized by Lerner are plans to incorporate other facilities such as a deep-water terminal, a fuel storage depot and a nuclear power plant as future needs require. Nutant (1973) presented results of environmental assessments for offshore floating nuclear power plants intended for use along the Atlantic and Gulf coasts. Many of Nutant's conclusions would still apply if the power systems were fixed to stable islands rather than floating behind protective breakwaters. In any of the technical analyses made on the feasibility of constructing offshore islands the cost and availability of suitable fill material is a major factor in determining the engineering design, which in turn, dictates the project costs. The modern effects of technologies pursued over the last 10,000 years for the advancement of civilization are evident in the peoples and cities of the world as well as in the transportation networks which bind them and
Fig.lA. ERTS-1 satellite imagery (band MSS 5) taken 16 August 1972 showing two slicks resulting from disposal of wastes in New York Bight.
B Fig. lB. Relationship of the two slicks (see Fig. 1A) to the fivecontemporary disposal areas shown by crosses.
TABLE I Time schedule for ocean disposal of wastes in New York Bight for 16 August 1972" Sewersludge (h)
Cellar dirt (h)
Industrialacid (h)
Dredge spoil (h)
0925 1018 1029 1215 1240 1705 1815 1837
0110
0145 1350
0435 0715 0830 09]5 1050 1153 1220 1345 1400 1450 1730 2305
*Data for this table obtained from permit files of the Supervisor of New York Harbor, New York District, Corps of Engineers. Time is Eastern Daylight SavingsTime (EDT). their activities together. These technologies and the activities spawned f r o m t h e m have created problems of environmental pollution as a result of waste disposal. In the New York Bight area waste-disposal activities are n u mer o u s (Table I) and often clearly visible (Fig.l). However, once below the sea surface, the visibility of those activities is lost, and oft en their existence is forgotten. This paper is intended to show that large volumes of waste materials are available f r om the ocean b o t t o m in the New York Bight area for construction purposes. This material may be available at a potentially lower unit cost and with possible environmental benefits. GEOMORPHOLOGY--GEOLOGY The Inner New York Bight (Fig.2) is underlain by Cretaceous and Tertiary Coastal Plain strata which dip and thicken to the southeast. T h e y consist primarily of glauconitic sands and gravel interbeded with silty sands. Most o f the region experienced significant subaerial erosion during Pleistocene times as a result of processes associated with the continental ice sheets which repeatedly covered the terrain to the north. The Hudson Channel (Fig.3) is one of the more p r o m i n e n t features on the shelf in this area and represents one of several major rivers which were drow ned during the Holocene marine transgression. However, unlike ot her channels in the region (McMaster and Ashraf, 1973; Williams, 1974), the Hudson has maintained its characteristic periglacial m o r p h o l o g y and has been only partially filled with outwash sand and gravel which was spread across the shelf by southward flowing melt water streams which issued from the ice fronts. It is also significant t ha t complete filling of the Hudson shelf channel by marine and estuarine sediment has n o t taken place during the past 11,000 years.
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A second prominent geomorphic feature peripheral to the Hudson inner shelf channel is Shrewsbury Rocks (Fig.3) which is an elongate shoal projecting about 15 km (8 n.m.) northeast from the New Jersey coast out to where it is truncated at the 27-m (90-ft) contour by the Hudson Channel. Shrewsbury Rocks is actually a series of shoals exhibiting about 5 m (15 ft.) of relief with the adjacent sea floor and in apparent strike alignment (about N60 ° E) with Coastal Plain strata on land. Collection of field data utilized in this report was made as part of a Coastal Engineering Research Center research program to study the geologic
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(From Williams and Duane, 1974. )
and engineering character of the U.S. inner continental shelf apropos the Corps of Engineers mission. Data include 824 km (445 n.m.) of continuous seismic reflection profiles (CSRP) and 61 vibratory cores (average length: 3.3 m; 10.7 ft.) of the subbottom sediment (Fig.2). CSRP records show that several strong acoustic reflectors, corresponding to Coastal Plain strata, do crop out on the sea floor in the vicinity of Shrewsbury Rocks while on the shelf to the south the strata are covered by variable thicknesses of Pleistocene-Holocene sediments. Cores in the Shrewsbury Rocks shelf region exhibit a relatively thin cover
of clean, medium-to-coarse, sand over either reddish brown silty sand and gravel or compact, glauconitic, sandy gravels (Williams and Duane, 1974). The sand and gravel blanketing this area is interpreted as residual detritus resulting from localized erosion by marine processes of the underlying Coastal Plain strata. The CSRP records and deep-foundation borings show that Pleistocene detritus in excess of 37 m (120 ft.) overlies the deeply eroded Coastal Plain surface of the shelf north from Shrewsbury Rocks to Rockaway Beach; similar data indicate that the inner shelf region south from Shrewsbury Rocks experienced only limited erosion during the Pleistocene. This contrasts with the reported relict nature of the topography and sediments for other parts of the Long Island--New Jersey shelf (McKinney and Friedman, 1970; Milliman et al., 1972; Frank and Friedman, 1973). Evidence is inconclusive regarding erosion of the Coastal Plain surface and subsequent deposition of sand and gravel being the direct result of glacial processes (Williams and Duane, 1974). However, the most significant agents in modifying this terrain were the ancestral Raritan, Passaic, East and Hudson Rivers. These rivers flowed east from New Jersey and south from New York and western Long Island Sound and converged in the Lower Bay (Fig.2). At least five buried channels, which may be Hudson distributaries, have been found to cross western Long Island (Williams, 1974). They predate the morainal formation of Long Island and were apparently significant in downcutting the Coastal Plain surface. The age relationship for these channels agrees with the conclusions of McMaster and Ashraf (1973) for the ages of buried channels underlying the eastern Long Island inner shelf. MATERIALS
The inner New York Bight has been the site for the ocean disposal of assorted wastes from the New York metropolitan area during the past almost nine decades (U.S. Army Corps of Engineers, 1915). The present authors have shown elsewhere (Williams and Duane, 1974} that the major physical evidence of this dumping operation are three circular sea-floor mounds in the Hudson Channel thalweg culminating as Castle Hill and the one mound forming Diamond Hill on the flat sea-floor apron immediately north of the channel (Fig.3). A bathymetric map of the same region based on 1845 survey data is depicted in Fig.4. It clearly shows the contrast between the natural Hudson Channel morphology and the present (modified) morphology shown in Fig.3. In 1845 the channel (Fig.4) was continuous for approximately 22.2 km (12 n.m.) from the shelf seaward of the 40-m (130-ft.) contour toward the Narrows separating Brooklyn and Staten Island. Other changes in shelf morphology between 1845 and 1934 appear to be slight except for the extension of Long Island and New Jersey barrier islands spits (compare Fig.3 and 4). On Long Island, Long Beach has accreted westward approximately 6.3 km (3.4 n.m.} and Rockaway Beach by 7.4 km (4 n.m.) while
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Sandy Hook, New Jersey, has grown north approximately 1.5 km (0.8 n.m.). Further growth of Sandy H o o k has been curtailed by dredging of the navigation channel immediately north of the spit. Net sea-floor changes in elevation within the area subject to ocean disposal, depicted in Fig.5, show that the areas of maximum sediment accumulation correspond to the Castle Hill region southeast of Scotland Light (> 15 m; 50 ft. fill) and to the Diamond Hill region (> 9 m; 30 ft. fill). The Castle Hill b o d y is elongate in a northwest direction parallel to the channel form. Dimensions of the fill b o d y are approximately 14.8 km (8 n.m.) long and 5.6 km (3 n.m.) wide. The protrusion to the southwest in the vicinity of Shrewsbury Rocks is judged not significant to probable
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F ig.5. Isopach m a p of Hudson Channel fillresulting from ocean waste disposal between 1845 and 1934. Isopach interval is 10 ft.,dash line is channel projection, crosses mark contemporary disposal sites. Note the close correspondence of m a x i m u m fillwith designated d u m p sites from 1903 to 1914. (From Williams and Duane, 1974.)
disposal practices as net changes could be attributed to a paucity of sounding data on the 1845 map for that area. Approximate volume estimates indicate that 765 million m 3 (one billion yd 3 ) of material is contained within the isopach boundary limits shown. Core data indicate materials from these sites are waste materials {Williams and Duane, 1974). Examination of historical records (U.S. Army Corps of Engineers, 1915) and use of interim bathymetric charts have provided a
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detailed chronological history of the growth of these morphologic features coincident to waste-disposal operations. Characteristics of CSRP records and sediment vibratory cores have shown that much of the fill is similar to indigenous shelf sediments, being of variable composition consisting mostly of clean sand and gravel and large "one-man and derrick" stones. The light dash lines in Fig.5 projecting east from Old Scotland Light correspond to ship tracks leading to the designated dump sites for the dates shown (U.S. Army Corps of Engineers, 1915). It is clear that the dump sites from 1903 to 1914 closely correspond to areas of maximum channel fill in the vicinity of Castle Hill. Boring-log descriptions (McClelland Engineers, 1963) verify that the Diamond Hill mound is composed of anthropogenic fill, however, no reference was found in official reports (U.S. Army Corps of Engineers, 1915) dating back to 1888 designating that specific region as a d u m p site. We judge the evidence to unequivocably indicate that Diamond and Castle Hills are waste materials accumulated as a result of disposal practices over the past nine decades. These early fill materials were generated by the excavation and construction underway during the growth and development of New York as both a metropolitan area and a major world seaport. A well documented example of one large-scale excavation project where the material was disposed in the ocean was the dredging, from 1900 to 1907, of the Ambrose navigation channel leading into the New York harbor. As a result of this single project approximately 38 • 106 m 3 (50 • 106 yd 3 ) of clean sand and gravel was removed from the sea floor in lower New York Bay and transferred and dumped in the Castle Hill area (Wigmore, 1909). Fig.6 shows three northeast--southwest oriented sea-floor profiles whose locations are shown on Fig.3 and 4. No doubt, some of the disparity between the 1845 and 1934 sea floor could be attributed to lack of accuracy in surveying, however, the net aggradation of the sea floor in profiles A and B is unmistakable. The lack of significant sea-floor change along profile C, which passes seaward of the isopached disposal area reported on here further indicates that at least the sand, gravel and stone fractions of the fill noted along profiles A and B are relatively stable in the present oceanographic environment and have shown minimal movement southward toward the deeper parts of the Hudson Channel. Based on the data presented and discussed above we judge the fill to be reasonably stable and that the material has remained in the immediate d u m p zone. Sea-floor currents in the inner New York Bight at these d u m p sites can exceed 25 cm/sec (0.5 knot) (Cok et al., 1973) and the wave climate (with a 50% probability of occurrence) is H s = 0.76 m (2.5 ft.); T = 5--15 sec (Harris, 1972). These construction waste products similar in character to the natural ocean b o t t o m are considered environmentally neutral. However, the presence of natural fine-grained sediments (very fine sand, silt and clay) mixed with assorted pollutants in the contemporary d u m p areas peripheral to Castle and Diamond Hills has been documented by Gross (1972) and
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Pararas-Carayannis (1973). The effects of these pollutants on the chemical, physical and biological characteristics of the shelf in the immediate d u m p zones are varied; presence of these materials in the construction waste must be considered by any shelf usage. DISCUSSION
Because of the demonstrated need for several new major facilities in the New York area and because of the serendipitous accumulation of an estimated 765 million cubic meters of fill it appears t h a t it may be economically feasible to construct an offshore, multipurpose, man-made island on the sea-floor seaward of the lower New York Bay and use the Hudson Channel fill as a major construction component (considering water depth it is technologically feasible to dredge-up this material). Use of offshore areas is already the subject of study. For example, a comprehensive feasibility study and proposal (Sea Island Project) to build one or more offshore multipurpose islands on the North Sea shelf off the coast of The Netherlands has been completed (Bos Kalis-Westminster Group, 1973). The Sea Island Project involves use of traditional land-reclamation practices applied to a shallow-water marine environment. The island body, with sand as the principal constituent, is to be surrounded by a,protective seawall consisting of concrete blocks or caissons (Fig.7). The Bos Kalis-
12
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/ m Fig.7. Two possible design profiles for a shelf-sited man-made island. (Courtesy of Ocean Industry Magazine, 1973, 4:187--194).
Westminster study concludes that in any case, ultimate island size and final number of component islands would depend on the intended usage, further emphasizing that construction costs per unit are drastically decreased for large islands with areas about 1200 hectares (3000 acres) (note: 1 hectare = i • 104 m 2 ) versus smaller ones with areas about 50 hectares (125 acres). Stigter {1973) has shown that the unit cost per square foot of smaller islands might be $12, with 90% of the cost incident to seawall construction. For an island of 1200 hectares the cost would be $3 per sq. ft. with approximately 50% attributable to seawall costs. Because a significant proportion of the total cost of island construction involves placement of sand fill for side slopes and seawall construction (which are not linearly proportional to island area) the unit area cost reductions for large islands as compared to small islands are dramatic. For the North Sea shelf region artificial island construction is presently feasible (Stigter, 1973); factors dictating the practicality of building such islands in other shelf areas, such as the inner New York Bight will vary based on economic, environmental, legal and engineering considerations.
13
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However, based on preliminary study o f this region (Kelly, 1973; Williams and Duane, 1974) it is judged there are certain advantages in having an island site situated on or south of Shrewsbury Rocks off northern New Jersey (Fig.8). On either the east or the west flank of the Hudson Channel the island proper would fit the following criteria: (1) it would be in approximately 24 m (80 ft.) of water; (2) 11--15 km (6--8 n.m) from the maximum accumulation of fill; (3) the sea floor south of Shrewsbury Rocks, veneered with sand, is underlain at shallow depths by compact Coastal Plain strata thus providing a suitable foundation for construction (U.S. Geol.
14 Surv., 1967); (4) such a site would be near shipping lanes and land-based facilities making transfer of inbound or o u t b o u n d materials more economical; (5) adjacent to the naturally deepened Hudson Channel which in this region is in excess of 37 m {120 ft.) deep and which would a c c o m m o d a t e even the largest predicted vessels with a minimum of initial and periodic maintenance dredging; and (6) the site would be b e y o n d the 3°mile limit of state jurisdiction but within the 12-mile territorial limit. Further, based upon economic and world trade factors this general region has also been indicated as a potential site for a VLCC facility for the mid-Atlantic region (Kelly, 1973). CONCLUSION Construction of a multipurpose island on the shallow shelf off n o r t h e r n New Jersey, to provide space for facilities needed along the North Atlantic coast, could, through proper processing and management, utilize waste materials as building blocks for island construction. Waste materials presently comprising Castle and Diamond Hills could be used for initial construction; similar waste materials, rather than be discarded w i t h o u t plan, could be used for island expansion or new construction. Use of the Hudson Channel fill as a major c o m p o n e n t in an offshore island project would also conserve land-based and offshore sand and gravel resources for other needs, reduce construction costs by reducing transportation costs, and reduce the environmental concern which might result from removal of the large volumes of alternative fill that would be needed if such a project were built using an alternate design. ACKNOWLEDGEMENTS Review o f early drafts of this manuscript by M. Grant Gross (National Science F o u n d a t i o n ) and G. Pararas-Carayannis (CERC) and discussions with colleagues M. E. Field and E. P. Meisburger were helpful and appreciated. Data presented were collected as part of the civil works research program o f the U.S. A r m y Corps of Engineers through the Coastal Engineering Research Center. Permission of the Chief of Engineers to publish this paper is appreciated; however, conclusions of this paper are the authors' and should n o t be construed as official D e p a r t m e n t of the A r m y position unless so designated by o t h e r authorized documents. REFERENCES
Bos Kalis-Westminster Group, 1973. Building a multipurpose island in the sea, Ocean Ind., 4: 187--194. Cok, A. E., Swift, D. J. P., Shepard, E. and Reynolds, R. J., 1973. Sediment unmixing in the New York Bight area, (abs.) Geol. Soc. Am., Progr. Abs., 5(2): 150. Frank, W. M. and Friedman, G. M., 1973. Continental Shelf sediment off New Jersey, J. Sed. Pet., 43: 224--237.
15 Gross, M. G., 1972. Geologic aspects of waste solids and marine waste deposits, New York metropolitan region. Geol. Soc. Am. Bull., 83: 3163--3176. Harris, D. L., 1972. Wave estimates for coastal regions. In: D. J. P. Swift, D. B. Duane and O. H. Pilkey (Editors), Shelf Sediment Transport: Process and Pattern. Dowden, Hutchinson and Ross, Stroudsburg, Pa., pp. 99--125. Kelly, J. L., 1973. Offshore terminals and the national perspective. Mar. Tech. Soe. Proc. 9th Ann. Conf., pp.9--18. Lerner, L., 1971. New York offshore airport feasibility study. (Exec. Brief. Saphier, Lerner, Schindler Environetics, 25 pp., unpublished.) McClelland Engineers, 1963. Fathometer survey and foundation investigation Ambrose Lt. Station New York Harbor Entrance, (Report No. 63-162-1, unpublished.) McKinney, T. F. and Friedman, G. M., 1970. Continental-shelf sediments of Long Island, New York, J. Sed. Pet., 40: 213--248. McMaster, R. L. and Ashraf, A., 1973. Subbottom basement drainage system of Inner Continental Shelf off southern New England. Geol. Soe. Am. Bull., 84: 187--190. Milliman, J. D., Pilkey, O. H. and Ross, D. A., 1972. Sediment of the continental margin off the eastern United States. Geol. Soc. Am. Bull., 83: 1315--1333. Nutant, J. A., 1973. An environmental assessment of floating nuclear plants. Mar. Tech. Soc. Proc. 9th Ann. Conf., pp.367--374. Pararas-Carayannis, G., 1973. Ocean dumping in the New York Bight, an assessment of environmental studies. U.S. Army Coast Eng. Res. Center Tech. Memo., 3 9 : 1 5 9 pp. Stigter, G., 1973. The building of islands in the open sea offers possibilities for the industrial development in the near future. Mar. Tech. Soc. 9th Ann. Conf., Preprint, 7 pp. U.S. Army Corps of Engineers, 1973. North Atlantic Coast Deepwater Port Facilities Study, U.S. Army Corps of Engineers District, Philadelphia. (unpublished). U.S. Army Corps of Engineers, 1915. Annual Report of the Chief of Engineers, 1: 1634--1648. U.S. Geological Survey, 1967. Engineering Geology of the Northeast Corridor, Washington, D.C. to Boston, Massachusetts-Coastal Plain and Surficial Deposits, Folio 1-514 A, B, C, U.S.G.S., Washington, D.C. Wigmore, H. L., 1909. Memorandum on dredging work in Ambrose Channel. U.S. Army Prof. Memo., Engineer Bur., 1: 57--62. Williams, S. J. and Duane, D. B., 1974. Geomorphology and sediments of the Inner New York Bight Continental Shelf. U.S. Army Coast Eng. Res. Center Tech. Memo., 45. Williams, S. J., 1974. Geomorphology and sediments of the Long Island Atlantic Inner Continental Shelf. U.fi Army Coast Eng. Res. Center. Tech. Memo. (in preparation.)