SEARS ISLAND CARGO TERMINAL
MARINE RESOURCES IMPACT ASSESSMENT
Prepared by Normandeau Associates
SECTION 2. MARINE OPERATIONS AT THE CARGO TERMINAL
Container Ships, Tugboats, Propwash.
SECTION 4. EELGRASS
Primary Impacts: Causeway, Dredging, Jetty
Secondary Impacts: Causeway, Dredging, Jetty Construction, Operation of the Terminal
SECTION 6. FISHERIES RESOURCES
Primary Impacts: Causeway, Dredging, Jetty
Secondary Impacts: Causeway, Dredging, Jetty Construction, Operation of the Terminal.
SECTION 2. MARINE OPERATIONS AT THE CARGO TERMINAL pg 17 of impact assessment section.
2.4. MDOT anticipates the proposed cargo terminal could service 80 to 90 ships per year, about 8 ships per month:
one container ship every 1 1/2 weeks, one breakbulk ship every 2 weeks one woodchip ship every 2 1/2 to four weeks
Container ships remain in port about 1 day, while breakbulk and woodchip ships remain in port about 2¬3 days.
Docking at the facility could be accomplished with or without tug service. As with all other commercial traffic operating in Penobscot Bay, cargoships using the proposed facility would be accompanied by a local pilot. Requirement for tugs would be up to the local harbormaster, weather and sea conditions. When a tug is involved, the ship will use minimum power during approach and departure to the port. Usually the ship will turn around north of the terminal so it can dock heading south. The ship would stop parallel to the wharf and allow the tug to push it broadside into the dock.
To assist the ship in leaving the wharf, the tug would pull the ship off. The tug would be angled, heading seaward. Running at slow prop speed, the ship would deflect most of the current created by the tug propeller, but create its own shoreward current. Unassisted, a ship would likely loosen its bow lines, swing its bow out. With the ship's stern angled toward the wharf, the rudder would partially deflect currents emanating from the propeller.
The magnitude of the propeller generated current heading toward the shore would depend on the ship's angle, propeller shaft power, and the speed and direction of tidal currents. The likelihood that these currents would erode sediments and cause turbidity would depend on the substrate condition, elevation of the propeller, ships draft and tide level.
Containers ships could use bow thrusters, breakbulk ships could use mid ship thrusters to push themselves off the wharf. In this event, currents would be directed nearly perpendicular to the shoreline. Bow thrusters are generally of short duration thrusts of power. The ship would have its main propeller turning at slow speed when using thrusters.
SECTION 4.0 EELGRASS
As indicated in the Sears Island Marine resources baseline report eelgrass beds occur along the northwestern shoreline of SI although densities were not quantified, field observations indicated distribution was not homogeneous in the area examined in 1992. Deepest occurrences of eelgrass was observed at ¬7 ft. Because all substrates within the study area, except ledge supported at least scattered strands of eelgrass, the entire study area between MLW and ¬7 ft was considered as potential eelgrass habitat.
Assessment of direct impacts makes no distinction between documented and potential eelgrass habitat and among areas of apparently different densities. The distinction was made between vegetated and non vegetated eelgrass habitat for the assessment of some secondary effects.
Secondary effects associated with the alternative wharf configurations generally related to water clarity, sediment erosion and deposition, current and wave velocity. These factors could affect primary production and sediment stability. Water clarity would not affect plants that are present, as short duration changes in water quality would have no effect on potential eelgrass habitat. Sedimentation could prevent establishment of eelgrass plants in areas that provide potential habitat. Structure or operation induced current and wave velocities sufficient to erode sediments could affect potential eelgrass habitat, especially if recruitment was dependent on seeds, rather than vegetative reproduction. This distinction will be included in the evaluation of each alternative wharf design.
Section 188.8.131.52 CAUSEWAY Eelgrass occurred in intertidal pools along the natural bar between Kidders Point and Sears Island prior to construction of the causeway. Examination of preconstruction aerial photographs indicated eelgrass occurred in two tidal pools approx 5700 square feet and 580 square feet based on interpretation of aerial photographs... These intertidal eelgrass beds were lost as a result of building the causeway.
Since completion of the causeway in 1989 is has been noted that natural reestablishment of small patches of eelgrass in tidal pools along the east side of the causeway. These patches aren't readily discernable in aerial photographs, but they have been observed from the ground. Robertson & Mann 1984 & Bayer found intertidal zones supported eelgrass as an annual, rather than perennial form Dependence on growth from seeds can result in high variability in bed size and density. Over the years, it seems to have been the case along the causeway.
Section 184.108.40.206 DREDGING The previously dredged area angles out from the Sears Island Shorelines at the north end of the dredged areas closest to the shoreline. (approximately 0.2 acres)
To the near shore dredge area for cell construction? was located shallower than ¬ 7ft Identified in 1992 as a limiting factor for eelgrass locally. This dredging resulting in the direct loss of this eelgrass habitat.
The Rockland disposal site was located in depths greater than ¬221 feet. Well below the zone that eelgrass occurs.
SECTION 220.127.116.11 JETTY The jetty, constructed in 1988, covers an area of 2500 square feet between MLW and ¬7ft mean water Including 6,100 feet squared in the dredged area. The jetty occupies an area of 0.2 acres of eelgrass and potential eelgrass habitat .
SECTION 4.1.2 SECONDARY EFFECTS
18.104.22.168.1 CAUSEWAY Filling operations on the causeway only took place during low tides, minimizing the likelihood of dispersion of fill from the work area. It is unlikely that prolonged turbidity developed as a result of construction. Small tide pools have formed along the eastern toe of the slope of the causeway that have been vegetated with eelgrass to varying degree since the causeway was completed.
22.214.171.124 DREDGING Turbidity induced reduced photosynthesis occurred as a result of the dredging. The extended periods of dredging during seasons when eelgrass growth most typically occurs can be systemized Eelgrass in the present: turbidity from dredging contributed to limited production in an area of 2.5 acres reduced production in 7.6 acres. Eelgrass was not present when dredging occurred. Turbidity Plume could not have impacted potential eelgrass habitat Unless they were highly depositional areas where a high rate of sedimentation prevented successful recruitment.
It is unknown whether it was present in the northwestern shoreline of Sears Island when dredging was initiated. The presence of eelgrass in the study area in August 1992 indicated dredging did not create any permanent impacts deleterious to eelgrass.
126.96.36.199 JETTY Eelgrass was present north and south of the jetty during the 1992 survey though the area adjacent to the south side of the jetty near Mean Low Water MLW appeared to be depositional with soft finegrained sediments predominating. Locally elevated turbidity or deposition could prevent vegetation of eelgrass.
Thus potential eelgrass habitat has been lost. The shallow subtidal area between the jetty and the protrusion of the mean low water contour about 500 feet to the south was characterized as silt cobble substrate with sparse eelgrass during baseline survey. This type of substrate is not indicative of deposition
The relatively sparse vegetation could reflect the combined influences of substrate and back eddy instability. This area is approximately 2.2 acres of potential reduced production.
SUMMARY Section 4.3 Primary impacts to eelgrass and potential eelgrass habitat under each alternative configurationare summarized in Table 4.3 (not shown).
There will be no differences in impacts to eelgrass among the alternatives related to the Earlier Action. Alternative D.1 would have a larger direct effect on eelgrass 11.3 acres) than any of the D¬2 Alternatives.
Differences in "footprint" among the D¬2 alternatives would be small. D¬2b and D¬2(c) have the greatest footprint in eelgrass habitat because of the culverted north areas D¬2(A) and D2(D) having the same footprint on this resource (0.2 acres) and D¬2(E) having the smallest footprint because of its placement of the intertidal structure on the piles (0.01) acres.
SECONDARY EFFECTS OF CONSTRUCTION are most closely linked to turbidity generated during dredging. Because of the larger volume and longer duration of dredging Alternative D1 will have a greater impact, albeit temporary, on eelgrass resources than any of the D2 Alternatives.
Alternative D-2 A, B and C would have greater impacts by the same token than alternatives D-2 D &E. Its relative to the amount of filling and piling would also affect different turbidity generation which could differ among alternatives. These differences are not presently quantifiable.
OPERATION OF THE CARGO TERMINAL could also cause secondary impacts to eelgrass resources. Areas of reduced wave energy, elevated current velocity due to vessel maneuvering, shading and scour at the base of riprap were identified as lost habitat. Alt D¬1 would result in the loss of 7.4 acres of eelgrass habitat resources D¬2 A&D would impact 5.6 acres of eelgrass habitat. D¬2 B& C would affect 5 acres of eelgrass habitat. D2 E would affect 4.5 acres of eelgrass habitat.
Areas affected by increased turbidity or sediment deposition are more difficult to predict, particularly because potential sediment release rate from construction activities and vessel maneuvering needed to estimate suspended sediment concentrations is unknown.
Figures 4¬3 areas are unknown. For alternative D¬1 This represents about 27.4 acres D2D: 29 acres; back eddies from alternative D¬2 A,B or C wharf construction could extend over a 9.9 acre area. Alternative D2E would be unlikely to generate a larger area impact base than undeveloped. No jetty conditions. Loss of eelgrass, potential eelgrass habitat due to filling, erosion, dredging or deposition or reduction in productivity due to turbidity or shading can effect the functions and values of the eelgrass beds along the northwest shores of Sears Island.
Direct loss of the resource would eliminate most functions presently provided by the eelgrass although man made structures could support other types of flora and fauna adapted to hard substrate conditions.
Construction and generated turbidity could affect the functional value of the eelgrass bed within the turbidity plumes. As long as the rhizome system remains intact, the eelgrass beds can continue to stabilize sediments. Under conditions of prolonged high turbidity, plants would die and function would cease. Dredging would create a plume of relatively short duration. Wharf construction would generate turbid conditions intermittently. It would be unlikely these activities would result in complete leaf loss. Thus the bed would maintain its ability to trap sediments.
This, however, could lead to higher than normal rates of deposition, because of a greater source of suspended particles. Reduction of photosynthesis due to reduced light conditions from shading or extensive turbidity would reduce eelgrass productivity and stressed eelgrass ecosystems. Annual production would be lower than without construction.
Effects, if any, of turbidity generated by construction on the ability of the affected eelgrass beds to support fish would be temporary. Fish vary in their response to turbidity. Demersal species are generally more tolerant of turbid conditions than pelagic species. Shoreside fish likely to occur in the area Rainbow smelt, atlantic silverside, alewife, 3 spined stickleback, blueback herring, could avoid the turbid area, thus there could be a temporary reduction in finfish utilization of the affected eelgrass bed.
Filterfeeding invertebrates associated with eelgrass could experience clogging. Motile species such as sand shrimp, crab and lobsters could leave the area or burrow into the substrate to avoid turbidity. Bivalves could temporarily cease feeding. There could be a temporary reduction in abundance or diversity of fish or invertebrates.
The ability of eelgrass to support wildlife is primarily waterfowl-related.
SECTION 6.6 IMPACT REPORT PG 146
SUMMARY OF EFFECTS ON FISHERY
The overall project effects on fishery resources are summarized, based on resource function and values presumed to be affected during the Earlier and Proposed Actions.
Prior to the construction of the causeway, the intertidal bar probably provided some level of functionality for aquatic biodiversity/abundance. (feeding breeding and refuge) and wildlife diversity/ abundance (feeding , breeding and refuge) of fishery resources as described in NAI 1994.
Those benthic and pelagic resources physically displaced by the placement of the causeway are permanently lost. The previous construction of 1.3 acres of mitigated clamflats should provide functional opportunity to replace those functions physically displaced by the causeway.
Stabilizing and armoring the causeway during construction has provided potential intertidal feed/ breeding/refuge habitat for both hard and soft substrate benthic fishery organisms, e.g.,shellfish, crustaceans, worms and sea urchins and some finfish. Changes in area hydrology may allow for the accretion of sediments transported along the post construction shoreline. (Since dredging the basin did not permanently displace subtidal resources, it is anticipated no long term impact to subtidal functions occurred). These functions also include: aquatic diversity/abundance, (feeding, breeding, refuge) and wildlife diversity abundance (feeding/breeding /refuge).
While the stone jetty physically displaces 0.3 acres of intertidal shoreline and 0.2 acres of subtidal resources, it is assumed that functional resource values were modified from benthic habitat function significant to soft substrate organisms to those more significant to hard substrate organisms.
Effects on small surface areas are not easily translated to changes in functional effectiveness or opportunity.
Proposed additional dredging under all proposed alternatives should not permanently displace subtidal resources again,it is anticipated no long term effects to the subtidal fishery or benthic or pelagic fishery functions described above would occur. The previously dredged basin contains a previously offed? condition which has undergone somewhat of restoration through natural recruitment.
In the D¬1 solid wharf configuration direct displacement effects would reduce the water column and benthic habitats of both intertidal and subtidal fishery resources. These impacts would be comparable to those impacts discussed in Section 5.3.
SECONDARY EFFECTS associated with changes in hydrodynamics, turbidity and sediment deposition could also affect several acres of intertidal and subtidal fishery resources and their associated functions and values. The specific concern, regarding secondary effects in all proposed wharf alternatives would be settleable solids and their smothering effect on sessile organisms and locally breeding finfish. what about the eggs, larvae and juveniles? All three are more sensitive to suspended solids than adult fish.
As stated in NAI 1994, any of the area utilized for spawning by Atlantic Herring Winter Flounder american sandlance, rock cunnel, tomcod and sculpins. These species represent potential food stocks for large carnivorous finfish and potentially valuable commercial and recreational stocks.
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