BENTON HARBOR POWER PUNT LIMNOLOGICAL STUDIES. PART I. GENERAL STUDIES. November, 196? By: John C. Ayers Joseph C. K. Huang Under Contract With: American Electric Power Service Corporation A. INTRODUCTION AND OUTLINE OF PROGRAM In response to a specific request from Mr. Paul Dragoumis, this report has been prepared prior, to the completion of the studies contracted . On the basis of the results to date, we believe that the study of the relationship of wind to current direction in the alongshore waters in front of the plant site is the only important task yet to be completed. We, therefore, present this report as Part I of the total report of the contract. Part II, consisting of the results of the wind-current relationship in the alongshore waters of the AEPSC site, will be presented at a later date. As a result of the request to report earlier than contracted, there is omitted one item which would have been a part of this report under normal conditions. This item is the preparation of an annual curve of air temperature for 1966. The air temperature curve is needed for comparison to water temperature curves, presented here, in determining seasonal variation in the ability of the local air-water environment to remove thermal load from the plant effluent. Our sincere thanks for assistance rendered are expressed to Messrs. Paul Dragoumis and J. E. Gingold. Especial thanks for assistance rendered at his own inconvenience are given to Mr. John Banyon . Work Plan and Its Status The program of work planned for the limnological surveys relative to the Benton Harbor generating plant consisted of the eight numbered items below. The present status of each item is shown . 1.. Bathymetric survey off site, . including consideration of bottom stability. Complete and reported, including early-spring check on effect of winter ice on the nature and position of the sand bars . 2. Bottom- type survey off site. Complete and reported. 3. Determination of alongshore current direction under various wind directions. Delayed by inability to obtain required instruments and by winter ice. Now under way. 4. Determination, by dye dilution experiments, of the inherent diluting capacity of alongshore currents at the site. Some runs have been made, more can be made if required. 5. Determinations of the locations of local potable water intakes and of the possibility of plant effluent reaching them. Complete and reported. 6. Ecological study of thermal pollution and its effects. Will be handled by Dr. C. F. Powers. As a basic pre- liminary to this study the numbers and distributions of bottom-living organisms off the plant site have been determined and reported. 7. Estimates of dilution and dispersion of thermal effluent from the plant. Completed and reported, but will be amended if work now under way permits better estimates. 8. Studies of unusual conditions. Extraordinary seiches are the only item in this section. Completed and reported. B. PHYSICAL LIMNOLOGY 1. REGIONAL FEATURES The Berrien County power plant site is located on the south- eastern shore of Lake Michigan in a region where land topography and lake-bottom topography both show the effects of glaciation. The lake-bottom topography (bathymetry) has been subject to the smoothing erosional and depositional actions of the lake water since recession of the last glacier. This smoothing action has been last to happen after the gouging and scouring actions of the glacier itself and after the water-laid deposition of sediments released from the glacier ice during melting and recession of the ice. From the sediment-sorting actions of the water there has further followed the development of a much more regular distribution of sediment types than is the case on land. Bathymetry The basin of Lake Michigan as a whole is divided by an in- complete sill of resistant materials extending from the region of Milwaukee, Wise, toward Muskegon, Mich.; this incomplete sill establishes two sub-basins called herein the northern and southern basins. While both basins show the smoothing actions of the lake water, the northern basin is deeper, more elongate and of more irregular bathymetry while the southern basin is shallower, rounder and of more regular bathymetry. Figure 1 is a recent chart of the bathymetry of Lake Michigan. Sediment Types In both basins of Lake Michigan the basic progression of bottom surface-sediment types is from sands or sand and gravel in a relatively wide belt along the beaches, to silty sands in a narrower more irregular belt in shallow intermediate depths, to sandy silts in a variable discontinuous band in deeper intermediate depths, to soft combinations of silts and clays and loam (sandy 68 44* BOTTOM TOPOGRAPHY LAKE MICHIGAN CONTOUR INTERVAL 100 FEET SCALE OF MILES 10 20 30 JOSEPH CHICAGO 88* 87 • 86' 42« 85* The bottom topography of Lake Michigan. (from Hough 19 5^) FIG. 1 silty clay) in the deepest portions. Figure 2 is the best recent chart of sediment types and shows this basic distribution of sediments . Benthos The bottom-living organisms (benthos) of the lake respond, in their degree of abundance, to a combination of sediment type and organic richness of the overlying water. By "organic richness" is meant the presence of decomposing and decomposed "natural" organic materials from the lake's watershed and "artificial" organic materials from man's wastes. These organic materials provide fine organic detritus and support bacterial growths, both of which are utilized as food by the bottom-living organisms. Figure 3 presents our present best knowledge of the distri- bution and abundance of the normal community of bottom-living organisms in the main part of the lake. There is lack of detailed knowledge in many regions, but we know of disrupted normalcy of the benthos at Milwaukee, in the inshore region from Chicago to Michigan City, and at the mouth of the St. Joseph River. Normal communities of benthos are known from studies by the present project to reach to the Michigan shore in the interval between Michigan City and the St. Joseph River. The maximum abundance of normal benthos follows the band of silty sand sediments which underlays the alongshore belt of currents that receives the decomposition products of natural organic materials and of man's wastes. Gross Currents The mass movement of water that is designated as "current" • is the primary distributor of everything inanimate that gets into the lake. Although we do not understand the currents of Lake Michigan in detail, there are certain larger features that have been found with a surprising degree of consistency. The two most firmly established of these features are a general outflow current along the Michigan shore from Little Sable Point northward toward the Straits of Mackinac, and the presence of a large eddy near the eastern shore off Benton Harbor. Both these features were found in the first significant current study, reported by Harrington in 1895. Deason (1932) deduced the presence of something like the Benton Harbor eddy. Ayers ejt aJL (1958) found both the eddy and the outflow current in surveys in 1955. Bellaire (1964) also found them both. Ayers e_t aJ^ and Bellaire disagree with Harrington as to the direction of rotation of the Benton Harbor eddy (Fig. 4) , while Deason shows no figure and speaks only of a "swirling action" in the southeast portion of the lake. While none of these studies were designed to delineate circu- lation immediately close to shore, they agree in the establishment of a major current feature close in to shore in the southeast corner of the lake. Ayers et. al^ (their Fig. 24) tentatively identify a thin elongate counterclockwise eddy close against shore between Michigan City and Benton Harbor (indicated by an X in Fig. 4) . This eddy may be pertinent to the alongshore currents at the plant site. The matter is discussed later. PORT WASHINGTON MILWAUKEE 43-30' Q ee'oo' WHITEHALL E60N GRAND HAVEN WAUKEGAN SOUTH HAVEN ST. JOSEPH 88*00' LAKESIDE CALUMET HSR MICHIGAN CITY GARY CLAY 8ILJY; CLAYEY SILT clay: SILT SCALE IN MILES 10 20 The bottom sediments of Lake Michigan in 1962-1963 • (from Ayers and Hough I964) Figure 2 SHEBOYGAN KACINE ST JOSEPH BENTHOS AVERAGE ASH -FREE WEIGHT AUG-NOV. 1964 GRAMS/METER^ SHEBOYGAN KACINE CHtCAGO JOSEPH AMPHIPOOS lOOO'f/METER^ AUG-NOV 1964 SHEBOYGAN MACINE CHICAGO OLIGOCHAETES lOOO's / METEr2 AUG-NOV 1964 SHEBOYGAN «ACINE CHICAGO ST JOSEPH AVERAGE RATIO NUM8ERAMPHIP0DS NUMBER OLIGOCHAETES AUGUST -NOVEMBER 1964 Distributions of bottom-living organisms in Lake Michigan, (from Pov/ers and Robertson I965) Figure 3 from Bellaire (I964) from Ayers et al (195S) Three concepts of the surface currents of Lake Michigan. FIG. h 2. LOCAL FEATURES Local Bathymetry The local distribution of water depth was surveyed in May, June and July 1966 from north of the mouth of the St. Joseph River to south of the plant site. The region is characterized by gentle and regular bottom topography (Fig. 5) . The 100-foot depth isopleth lies at about six miles from shore. Isobaths less than 40 feet are regular and parallel to the shoreline. Isobaths between 40 and 7 5 feet exhibit some irregularities between St. Joseph and Grand Marais Lakes, becoming regular and essentially parallel to shore south of Grand Marais Lakes. In the whole extent of the survey there were two sand bars close to shore. They have been subject to spot tests between the plant site and St. Joseph, but not in detail sufficient to warrant their charting. Along the front of the plant property and to one mile south of Livingston Road these bars have been surveyed in sufficient detail to chart. They are shown in front of the plant property and to the south boundary of the survey in Figure 5. The inner bar averages about 500 feet from water's edge over the area of detailed survey, but lies slightly nearer to shore off the north edge of the plant property. At the north edge of the site a taut-wire measurement on 13 September showed the inner bar to be about 450 feet from water's edge. The 500-foot distance from the beach edge at the point fell into 11 feet of water out- side the crest of the inner bar. The outer bar lies about 1000 feet from water's edge at the north edge of the plant site. It is situated about 1100 feet off ^Jf BATHYMETRIC CHART raweK PLANT SITE BENTON HARBOR CONTCHW INTERVAL 2 SFCET FIG. 5 FIG.z2:B^3r shore at Livingston Road, but at the south edge of the survey it again lay at 1000 feet off shore. Maximum water depth of 5-6 feet is present between the inner bar and the. shore. Twelve to thirteen feet of depth is the greatest that was measured between the two bars . Outside the crest of the outer bar the bottom falls slowly; 20 feet of depth is attained at about 1700 feet off shore at the north edge of the plant property. Over the rest of the detailed survey about 1800 feet from shore was needed to reach 20 feet of depth . The depth over the crest of the inner bar is about four feet. The outer bar peaks at 8-9 feet beneath water surface. Bottom Stability Our own bathymetric surveys in May, June, and July plus an additional visit to the site on 13 September all showed the two sand bars to be in the same positions and with the same depths of water over their crests and in the troughs. This suggestion of stability of the bottom, insofar as possible migration of sand bars is concerned, is in agreement with the findings of Davis and McGeary (1965) . In June and August of 1963 they carried out detailed underwater studies of the topography and sediment distribution in two sites in Michigan on southeastern Lake Michigan. One of their study sites was in Berrien County, the other in Allegan County. The Berrien County site was between Union Pier and Bridgman, Mich. Davis and McGeary found that no distinction existed between data collected before and after this two-month interval in summer during which the normal summer storms occurred. The offshore bars remained constant in relationship to the shore and showed only • small variations in profile shape. Indices of water depth, mean sediment grain size and of sediment sorting showed little change, all indicating relative stability of the alongshore topography. In addition to the studies above, Davis and McGeary examined aerial photographs of their study sites that had been taken in 1953 and in 1960. As near as they could determine the bars were then in the same position as in 1963. So far as we can determine no one with the possible exception of Evans (1940) has examined the alongshore topography early in the spring to ascertain whether winter storms or ice have produced topographic changes. Evans believed that the bar and trough topography in the alongshore of eastern Lake Michigan was not appreciably changed with time. Evans' studies were carried out in Lake Michigan from the city of New Buffalo to Grand Traverse Bay using five different methods through two years . Over a period of about 14 months he observed that little or no movement of the well-established sand bars occurred. Even after a heavy storm with high winds of more than 35 mph which lasted 36 hours on August 8-9, 1939, there was no general migration of the trough and bars in either direction. Evans' hypothesis was that sand bars are deposited by the plunging type of breaking waves, which stir up sediments from the bottom and move most of them in the windward direction. Oscillation waves which produce plunging breakers of sufficient size to affect the inner bars may pass over the outer bar without breaking. Such waves have little or no effect on the trough and outer bar. If water-level falls, the inner bar will begin migrating toward shore as soon as its top comes within the sphere of action of plunging wave crests . In the southern area of Lake Michigan oscillation waves and small water level fluctuation are common. Therefore, the inner bar which is about 450-500 feet offshore in the site area is subject to slightly more potential migration force than is the outer bar . The Bars on 30 March 1967 On 30 March 1967 the RV MYSIS made a check on the presence and condition of the two sand bars within a few days of breakup of the shore ice. As near as could be determined from sextant fixes on landmarks on shore both the bars were in the same position as in September 1966. Both the bars had the same depth of water over them as in September . Local Sediment Types During July of 19 66 we surveyed the bottom sediments of the local area from the mouth of the St. Joseph River to a mile and a half south of Livingston Road at the south boundary of the plant property. Lines were run to three miles off the beach and were spaced at half-mile intervals. The results are shown in Figure 6. The predominant sediment of the bottom over the area was fine sand, either silty and with visible organic material, or non-silty and with organic material. In several places there was sufficient 10 of a brown mineral (probably hematite) to cause the observer to note "speckled" in his reading of the sands. One sample of coarse sand was taken off Livingston Road, and a couple just below the mouth of the St. Joseph River. Medium sand was taken in a few samples along the beach south of the mouth of the St. Joseph River. It was also taken in a some- what larger area at the outer edge of the survey northwest of Grand Marais Lakes. One sample was also taken off the north edge of the plant property. Soft grey loam (sand-silt-clay) was taken in a few samples west of Grand Marais Lakes, and northwest and north of those lakes. The sand of these loams was fine sand. Except for the predominance of silty and non-silty fine sands, there are only two items of ecological interest: the widespread occurrence of organic material with a local area of abundance southwest of the mouth of the St. Joseph River, and a definite area of sandy silt surrounding the mouth of that river. Cook and Powers (1964) studied the effect of the St. Joseph on the bottom- living organisms. At stations around the river mouth they found these organisms to be dominantly pollution- tolerant forms, and speculated that organic solids contributed by the river should modify .the sediments near the river mouth. We find that modifi- cation to be present. The Local Benthic Organisms On 13 and 15 July 1966, we surveyed the local population of bottom organisms. The survey consisted of collecting samples in a regular fashion in lines perpendicular to the beach. The survey u began at the mouth of the St. Joseph River and extended to a line a mile south of the site property. In each line the inshore samples were taken in 15 feet of water with other samples at 1 mile, 2 miles, and 3 miles off the beach. From the river mouth to the north edge of the plant property sampling lines were one mile apart. In front of the site the interval between lines was reduced to a half-mile. Samples were taken by grab sampler and washed through a sieve of 0.5 mm mesh. Organisms retained by the sieve were preserved in formalin and sorted, counted, and processed in the laboratory. A total of 60 stations were sampled, and samples off the site property were taken in triplicate and averaged. The parameters determined were the same as used by Powers and Robertson (1965) in their surveys of the main body of the lake. The parameters reported here are 1) ashfree dry weight of all organisms (as the best measure of the mass of organic matter of the animals, free of shells, sand, etc.), 2) numbers of amphipods (also commonly called aquatic scuds or freshwater shrimp) in thousands per square meter of bottom surface, 3) numbers of oligochaetes (also called aquatic earthworms, tubificids, or sludgeworms) in thousands per square meter, and 4) the ratio at each station of numbers of amphipods over numbers of oligochaetes. The distributions of these parameters are shown in Figure 7. The distribution of mass of benthic-organism tissue (Fig. 7A) is evidently related in substantial degree to sediment type. Low weights of organism tissue were present in the clean sands of the area immediately next to the beach. Low weights were also found FIGURE 6 ^^mm^^^^^^^^^^^^^^ U> K£) 12 in the sandy silt region extending a mile off the mouth of the St. Joseph River. High quantities of organism-tissue were in most cases corre- lated with bottom areas of silty fine sand. The two areas of maximum biological mass lay in silty fine sand two and three miles off the mouth of the river, and at the second and third miles off- shore south of the property. An area of less organism mass lay in silty medium sand and in loam west of Grand Marais Lakes. Northwest of Grand Marais Lakes there was an extensive region that yielded less than one gram of organisms per square meter and which reached offshore through • the three-mile grid of sampling stations . There was no evident relation between the mass of benthic- organism tissue and the presence of organic material in the surface sediment. In all but one case the presence of speckled sand correlated with low quantities of biological mass. The meaning of this relation is not clear. In general, the' distribution of the quantities of the whole benthic population appears to be typical of the clean-water portions of Lake Michigan. The low population in the first mile off the beach is normal. There is, in the present natural con- dition, no unusual concentration of benthic organisms near shore that would attract fish in unusual numbers. The distribution of the amphipod, Pontoporeia af finis , over the survey area is shown in Figure 7B . High numbers of this organism coincide with areas of silty" 13 sand and of loam. Low numbers were present in the sandy silt area at the mouth of the river and in the belt of wave-washed sands along the shore . In most cases / areas, of speckled sand contained low numbers of amphipods . The presence of Pontoporeia in goodly numbers in the second and third miles from shore is normal for the unpolluted portions of Lake Michigan. This organism is commonly regarded as an indicator of clean water. Its virtual absence near the beach indicates only unfavorable conditions of wave-action, not unclean water . The distribution of oligochaetes is shown in Figure 7C. Some of these organisms are tolerant to organic pollution, and extremely high numbers of them are commonly considered to be an indication of polluted waters . 2 The maximum numbers found, 31,000/m off the river mouth, 2 7 29,700/m in the south edge of the surveyed area, and 14,500/m"' 2 and 14,400/m off the south side of the property, are reflections of organic matter in the sediments and water and of suitable sediment types. These numbers, though large, are not in the 2 hundreds-of-thousands/m that indicate polluted water. Wave action in the belt along the beach is probably the cause for low numbers of oligochaetes there, for they are soft-bodied and wave-caused sand movement is injurious to them. In Figure 7D is presented the distribution of the ratio: numbers of amphipods/n umbers of oligochaetes. This is basically a measure of clean-waterness . High values of the ratio express dominance of the clean-water amphipods; low values indicate 14 dominance of the pollution- tolerant oligochaetes . No suggestion of unclean water should be read from the zero values along the beach. These merely reflect the normal absence of amphipods from wave-swept areas. Three centers of high values are present: southwest of the river mouth, northwest of Grand Marais Lakes, and off the plant property. Lower, but not fractional (less than one), values occur between the centers of high values over nearly all the area surveyed. Only south of Livingston Road do values less than one extend out through the surveyed area. At present we do not inter- pret these low values as indicating unclean water, for there are high numbers of the clean-water-loving amphipods at these stations (see Fig. 7B) . Some factor not now known produces at these stations an unusually high population of the oligochaete worms. In summary, the evidence given by the benthic organisms is that the waters bordering the property are at present predominantly of the clean-water characteristics found over most of Lake Michigan. Local Currents Studies producing estimates of the regional current pattern off the Berrien County shore of Lake Michigan were carried out by Harrington (1895) , Deason (1932) , Ayers et. al (1958) and Bellaire (1964). These have been discussed earlier. They define a large eddy of current, called here the Benton Harbor eddy, lying offshore, but close to shore, and extending from Muskegon or Grand Haven to Michigan City. Interpretations as to the rotation of this eddy have not been consistent. Ayers ejt _al deduced a tentative thin elongate counterclockwise eddy between the larger eddy and the shore 15 between Michigan City and Benton Harbor. The directions and speeds of the local water currents in the area of . the plant site will control the movement and dispersal of the plant effluent. In other alongshore environments that we have studied in the Great Lakes, the currents alongshore are usually established by and controlled by interactions between local winds and any significant regional current pattern. In the alongshore areas previously studied, the local winds have been the dominant factor in the control of the local currents. We have no reason to expect that this will not be true at the present site, but we have not yet collected sufficient evidence to determine whether I — the effect of the regional current pattern will be as minor here as it has been at other sites. Spot- sampling of simultaneous wind and current conditions has been carried on in connection with other portions of the work done off the plant site, but such sampling cannot readily accumulate the very large numbers of observations needed to understand the mechanism controlling the local currents. Especially spot-sampling cannot supply the large series of time-sequence data needed to determine whether present currents are influenced by past winds. Continuously recorded simultaneous wind and current conditions are in progress to obtain the needed data. Although the recording and analysis of these data have been a matter of dominant interest since the beginning of the contract, we have been prevented from getting at it by simple inability to obtain the necessary instruments. Winter storms and winter shore- ice are almost certain to destroy underwater installations that are anything other than massive; installation of the underwater 16 current-sensing gear was consequently postponed until spring of 1967. The little that can be said of the current regime alongshore at the plant site is based upon spot-sampling carried out during summer and fall of 1966. The data presently available are pre- sented in Table 1. Comparison of the actions of drogues to that of dye on 26 October under SSW wind suggests that the drogues may have been in the offshore edge of the counterclockwise Michigan City-Benton Harbor eddy of Ayers et. al 'while the dye was in the shoreward edge of the same eddy. Similar behavior of the dye sets of 27 October under southwest wind also suggests the presence of the postulated onshore counterclockwise eddy, with the dye in its onshore edge. The behaviors of the dye patches and drogues on 24 and 2 5 October under northwest winds are contradictory. Such behaviors might indicate that northwest winds constitute a phase-over condition wherein changeover between two dominant current directions is achieved. Such behaviors might indicate some wind- velocity control of current direction, either in a phase-over direction situation or in a condition in which some critical wind velocity is needed to maintain a current pattern, i.e. the Benton Harbor eddy and associated onshore elongate eddy. The answer cannot be gotten from the data available. The northwest-wind paradox does, however, illustrate why winds and currents are being simultaneously recorded for a long period. 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