LOCATION AND PHYSICAL DESCRIPTION
Collingwood Harbour is situated on the south shore of Nottawasaga Bay, which constitutes the southern extension of Lake Hurons Georgian Bay. The harbour covers 0.8 km2, with a maximum depth of 6.4 m and an estimated volume of 28.7 X 10-4 km3. Exchange between the harbour and surrounding waters is limited since the harbour is positioned at the south end of Nottawasaga Bay with only one opening to the bay. The harbour is surrounded by the Town of Collingwood, which has a permanent resident population of 14,685. The harbour includes a wetland complex, a wastewater treatment plant outfall, marinas, grain terminal, and former shipyards.
PROJECT GOALS AND OBJECTIVES
The project goal was to remove and dispose of sediment that failed the biological assessment criteria. This included approximately 8,000 m3 of contaminated sediment from shipyard slips and adjacent areas in the harbour, demonstrating an innovative removal technology for the first time in North America. Project objectives included removing all sediment that resulted in chronic toxicity or impaired benthic community structure, and improve conditions for benthos in support of the Public Advisory Committee's goals for the future quality of the harbour environment.
SEVERITY AND GEOGRAPHIC EXTENT OF PROBLEM
In the 1980s, sediment was found to have metals and PCBs in excess of provincial open water disposal guidelines (Figure 1, Table 1). Sediment testing carried out in 1974, 1983, 1986, 1988 and 1991 showed that sediment quality has generally improved over time (Collingwood Harbour RAP Team and Public Advisory Committee, 1992). Sediment from only a small, localized portion of the harbour was found to be contaminated, mainly due to historical use of the harbour as a center for the repair and construction of Great Lakes vessels. Levels of PCBs, zinc, lead, phosphorus, Kjeldahl nitrogen and several metals in surficial sediment (3 cm depth and above) exceeded the provincial guidelines for open-water disposal of dredged material in 1986. Near the Collingwood Shipyards, sediment contamination was found to be more extensive inside the turning basin than outside the harbour. In 1986, dredging was conducted for navigational purposes. A general decline in contaminant levels was observed in 1987 most likely due to sediment removal. Twelve stations were sampled -- nine within the harbour and three in Nottawasaga Bay. By 1987, only one station remained with zinc, copper and lead levels marginally above the provincial guidelines lowest effect level, which currently replaces the open water disposal guidelines. PCBs were below the detection limit.
Figure 1. Sediment sampling station locations
Table 1. Mean concentrations of metals, PCBs, oil and grease in Collingwood Harbour sediments, pre-(1986) and post-(1987) dredging (All values are in mg/kg or parts per million, except for PCBs which are in g/kg or in parts per billion)
| Station | PCBs | Cd | Cr | Cu | Hg | Ni | Pb | Zn | Fe | Oil & Grease | |
| 19 | (1986) | 66 | .46 | 22 | 25 | .07 | 12 | 34 | 53 | 11,025 | 1,093 |
| (1987) | <43 | .54 | 25 | 25 | .06 | 13 | 30 | 30 | 12,000 | 519 | |
| 20 | (1986) | 65 | .64 | 30 | 41 | .12 | 17 | 58 | 97 | 13,500 | 2,875 |
| (1987) | 93 | .61 | 24 | 31 | .08 | 15 | 45 | 83 | 14,000 | 1,187 | |
| 21 | (1986) | 192 | 13.5 | 36 | 72 | .24 | 19 | 133 | 195 | 17,000 | 3,175 |
| (1987) | 160 | .77 | 31 | 59 | .12 | 17 | 110 | 190 | 16,500 | 2,509 | |
| 22 | (1986) | 55 | .33 | 18 | 26 | .11 | 9 | 48 | 69 | 9,300 | 2,370 |
| (1987) | <20 | <.28 | 17 | 16 | .13 | 6 | 29 | 57 | 7,400 | 9,027/280 | |
| 23 | (1986) | 103 | .62 | 28 | 49 | .23 | 16 | 79 | 115 | 15,000 | 4,700 |
| (1987) | 105 | .60 | 29 | 38 | .13 | 16 | 80 | 120 | 15,000 | 1,162 | |
| 25 | (1986) | 40 | .42 | 18 | 25 | .12 | 10 | 34 | 51 | 10,200 | 2,450 |
| (1987) | <20 | .39 | 19 | 14 | .03 | 6 | 20 | 40 | 8,600 | 2,191 | |
| 28 | (1986) | 33 | .38 | 17 | 22 | .09 | 10 | 25 | 46 | 9,150 | 2,250 |
| (1987) | <20 | .43 | 23 | 24 | .04 | 13 | 32 | 65 | 12,500 | 2,499 | |
| 30 | (1986) | 93 | .61 | 27 | 43 | .14 | 18 | 56 | 94 | 15,500 | 2,018 |
| (1987) | <53 | .71 | 27 | 33 | .08 | 14 | 44 | 76 | 14,000 | 833 | |
| 32 | (1986) | 22 | .22 | 14 | 7 | .03 | 4 | 10 | 19 | 7,156 | 934 |
| (1987) | <20 | .31 | 16 | 10 | .02 | 5 | 13 | 29 | 7,200 | 319 | |
| 387 | (1986) | <20 | .29 | 18 | 19 | .02 | 11 | 10 | 26 | 10,350 | 2,612 |
| (1987) | <20 | .45 | 20 | 15 | .01 | 10 | 10 | 30 | 9,400 | 530 | |
| 388 | (1986) | <20 | .26 | 15 | 9 | .03 | 6 | 5 | 10 | 21,240 | 596 |
| (1987) | <20 | <.30 | 15 | 6 | <.01 | 4 | 6 | 12 | 7,000 | 142 | |
| 393 | (1986) | <20 | .32 | 11 | 11 | .06 | 4 | 14 | 31 | 6,450 | 1,468 |
| (1987) | <20 | <.30 | 16 | 10 | .02 | 6 | 14 | 35 | 7,700 | 487 | |
| Dredging Guideline | 50 | 1.0 | 25 | 25 | 0.3 | 25 | 50 | 100 | 10,000 | 1,500 | |
| Lowest Effect Level | 70 | 0.6 | 26 | 16 | 0.2 | 16 | 31 | 120 | 20,000 | ||
Source: Collingwood Harbour RAP Team and Public Advisory Committee (1992)
Based on multiple lines of evidence proided by laboratory bioassays and field observations of invertebrates and sport fish collected during the late 1980s and early 1990s, it was determined that sediment contamination and impacts were confined to the Canada Steamship Limited (CSL) slips and water lots adjacent to at the shipyard property (Figure 2). Sediment samples collected outside the CSL slips generally met the biological requirement that toxicity was not significantly different from reference values.
DESCRIPTION OF REMEDIAL ACTIONS
Based on sediment chemistry, benthic community structure, and sediment bioassays, Collingwood Harbour was selected as a demonstration site to test an innovative removal technology. By November 1993, approximately 8,000 m3 of sediment from the shipyard slips and adjacent areas in the harbour were removed using the Pneuma airlift pumping system. The pumping system is based on a principal of using static water head and compressed air inside cylinders. Each of three cylinders is rapidly filled with slurry by counter pressure due to a hydrostatic head and induced vacuum. When one cylinder is filled, compressed air acts as a piston and the slurry is then forced through a check valve to the discharge pipeline. The pump has no rotating parts or mechanisms in contact with the sediment, minimizing sediment resuspension problems. Contaminated sediment was removed from the harbour slips and transported through a pipeline to a confined disposal facility (CDF) 1.2 km away. A silt curtain located at the north end of each slip was used to confine any possible particle resuspension due to unforeseen dredging complications. The silt curtain was constructed of geotextile material, with the top connected to a floating boom which was monitored daily for any indications of damage. Turbidity, suspended solids, and total organic carbon concentrations were minimal. Using this technology, a full-scale cleanup of contaminated sediment remaining in the harbour has been completed. The pumping system was found to be most efficient when semi-submerged in sediment. After cleanup, the Pnuema Pump was used by Transport Canada to supply fill and cap material for the CDF with excellent results achieved ahead of schedule. The partners involved in the cleanup were Environment Canada (Great Lakes Cleanup Fund), the Town of Collingwood, Transport Canada, the Ontario Ministry of Environment and Energy, Collingwood Terminals, the Aquateers of Base Borden, and CSL (Canada Steamship Lines) Equity.
COST
The total project cost was approximately $1.36 million for the Collingwood project where $425,000 was contributed by Environment Canada's Cleanup Fund. The remaining costs were divided among the other partners.
REGULATORY CONSIDERATIONS
Concentrations of metals, trace organic contaminants, and nutrients in sediment within the harbour turning basin had to meet Ontario Ministry of Environment guidelines for management of contaminated sediment (i.e. the lowest effect level) if unrestricted dredge disposal was to resume. Due to the fact that there is no expected need to dredge over the next 30 years, then sediment quality should support healthy benthic communities. For areas that had contaminant concentrations in sediment in excess of the lowest effect level, biological tests had to be performed to make a determination on the toxicological properties of these materials.
CLEANUP TARGETS AND ENDPOINTS
Sediment-related targets included:
Site-specific guidelines for benthos are established from a reference site database (i.e. biological attributes and environmental variables) using multivariate techniques, such as cluster and ordination analysis (Reynoldson and Zarull 1993). Reference site benthic communities are grouped using cluster analysis. The site environmental variables, which are not affected or minimally affected by anthropogenic activity, are then used as predictors to group the sites into the appropriate biological clusters. The benthic community structure and the same nine environmental variables (depth, NO3, silt, aluminum, calcium, loss on ignition, alkalinity, sodium, pH) are measure at the test sites. Using the environmental predictors and the discriminant model (derived from the reference site database), each site is assigned to a biological cluster. The benthic invertebrate data are then similarly analyzed. If the site lies outside the reference site cluster, then that site is judged to be impaired.
In the Great Lakes, 335 sites have been sampled and the multivariate "model" developed from this database correctly predicts benthic invertebrate communities with 90% accuracy (Reynoldson et al. 1995). In addition, acute and chronic measures of "toxicity" (including growth and reproduction) performed at these same sites provide measures of background performance for the appropriate, indigenous organisms that are to be used in assessing sediment toxicity.
Ontario Ministry of Environment has also released biologically-based, sediment contaminant concentration guidelines for use in assessing bottom sediments in Areas of Concern, to assess the need for source control and for use in assessing dredged material disposal. These chemical concentration guidelines are also supported through the use of site-specific bioassays (OMOE 1992).
Sediment bioassays, an essential adjunct to chemical guidelines, provide confirmation that sediment is the cause of the impact, rather than the water column or other factors. As with community structure, a reference site (bioassay) database has been established (Reynoldson et al. 1995). Examples of quantitative endpoints for standard sediment bioassays performed at "clean" sites (based on the value at the 5th percentile on the normal distribution curve below which toxicity is indicated) include:
The OMOE restricts open-water disposal based on chemical parameters alone, however the model developed by Environment Canada proposes that if the community criteria (CC) and the bioassay criteria (BC) are met, then open water disposal of sediment is acceptable. The Environment Canada model is strictly a proposal therefore the provincial jurisdiction currently prevails for dredging activities around the Basin.
Chronic low level toxicity problems were found within the shipyard slips and in a smaller zone northwest of the slips (Figures 4 and 5). Reproduction, although reduced, did continue during bioassay exposures. Based on community structure, oligochaetes are abundant at those sites in the harbour that elicited low level toxicity. Part of the reduction in reproduction could be attributed to the higher clay content of these sites, which makes burrowing activity more difficult and food less accessible. However, tubificids have shown sensitivity to metal contamination, therefore a remedial strategy has been implemented.
POST PROJECT EVALUATION OF EFFECTIVENESS
Monitoring data collected after sediment removal was completed show a sharp decline in metal concentrations in the dredged zones. Sediment that resulted in chronic toxicity or impaired benthos was removed from the harbour environment. The site is receiving deposion of clean material and recolonization will be monitored routinely. Since this type of environmental benefit has not been measured in conjunction with known environmental clean-ups elsewhere, no information is available to determine the rate of benthic recolonization. The Collingwood post-project monitoring of this phenomenon will generate valuable data upon which to predict environmental benefits at other locations.
Sediment bioassays conducted by the Collingwood Harbour RAP Team elsewhere in the harbour have confirmed no growth inhibition (Figure 3). The absence of growth inhibition is one line of evidence that indicates sediment is not eliciting toxicity. The 1990 mussel biomonitoring and analysis of native benthic invertebrates support the findings on toxicity and bioaccumulation (Collingwood Harbour RAP Team and Public Advisory Committee, 1992). Benthic community structure is comparable to refrence sites of similar environmental properties and remote from pollutant sources. The presence of mesotrophic indicator species confirms the harbour sediment can support a healthy benthos (Krantzberg 1995). Based on bioassay information, field observation on native benthic invertebrates, young of the year spottail shiners, sport fish and introduced mussels, it was concluded that concentrations of biologically available contaminants Collingwood Harbour outside the clean-up zone are not toxicologically significant and do not impair goals, uses, or Great Lakes Water Quality Agreement beneficial uses. As stated in the RAP stage 3 publication:
"Benthic community structure and biomass resemble control sites of comparable physical and chemical characteristics, and sediment bioassays confirm no toxicity, in accordance with International Joint Commission delisting guidelines and requirements for healthy, self-sustaining fish and wildlife communities."
CONTACT PERSON OR AGENCY
Dr. Gail Krantzberg
Ontario Ministry of Environment
40 St. Clair Ave. W.
Toronto, Ontario M4V 1M2
(416) 314-7973
KEY REFERENCES
Collingwood Harbour Remedial Action Plan Team and Public Advisory Committee. 1992. Collingwood Harbour Remedial Action Plan Stage 2 Report. Ontario Ministry of Environment and Energy, Toronto, Ontario; Environment Canada, Ministry of Natural Resources, and the Collingwood Harbour Public Advisory Committee, 275 First St., Collingwood, Ontario.
Collingwood Harbour Remedial Action Plan Team and Public Advisory Committee. 1994. Collingwood Harbour Remedial Action Plan Stage 3 Document. Ontario Ministry of Environment and Energy, Toronto, Ontario; Environment Canada, Ministry of Natural Resources, and the Collingwood Harbour Public Advisory Committee, 275 First St., Collingwood, Ontario.
Krantzberg, G. 1995. Using the burden of evidence approach for sediment management; Case study: Collingwood Harbour. In: The Lake Huron Ecosystem: Ecology, Fisheries and Management. (Eds. M. Munawar, T. Edsall and J. Leach). pp. 365-395. Academic Publ. Amsterdam.
Ontario Ministry of Environment (OMOE). 1992. Guidelines for the protection and management of aquatic sediment quality in Ontario. Toronto, Ontario, Canada.
Reynoldson, T.B. and M.A. Zarull. 1993. An approach to the development of biological sediment guidelines. In: Ecological Integrity and the Management of Ecosystems. Eds. G. Francis, J. Kay, and S. Woodley. St. Lucie Press, Florida.
Reynoldson, T.B., R.C. Bailey, K.E. Day, and R.H. Norris. 1995. Biological guidelines for freshwater sediment based on BEnthic Assessment of SedimenT (the BEAST) using a multivariate approach for predicting biological state. Aus. J. Ecology. 20: 198-219.