KJIPUKTUK (Halifax) - As the Nova Scotia provincial Liberal government pushes forward Bill 89 – the “Boat Harbour Act”, there is a certain merit in contemplating exactly how this government (and perhaps whoever next inherits the clean-up operation) will proceed. Promising that one will 'clean up' Boat Harbour, which since 1967 has been used as an effluent dumping ground for a rotating cast of owners at the Abercrombie Point Pulp and Paper mill - and actually cleaning up Boat Harbour - are two vastly different things.

Remediating a tidal lagoon that has been the recipient of an estimated one trillion litres of effluent, to a relatively pristine condition, is no easy feat.

The provincial Liberals promise that a plan to remediate the site is forthcoming shortly. But for the layperson, who might look upon the 163 fouled acres of Boat Harbour in its current incantation and think that no amount of cleaning will ever put the shine back in the place, that's a certain degree of blind trust to put into politicians.

Indeed, if you've ever looked out at Boat Harbour, without having the requisite mental imagery of how the place once was, perhaps your first inclination was to run from it, if possible, rather than try and clean it up.

Dalhousie University's Dr. Tony Walker, however, says that the clean-up actually can be done. Walker, with nine years experience as an environmental consultant, was the lead scientist in developing the marine Environmental Effects Monitoring (EEM) program in Sydney Harbour, on behalf of the Sydney Tar Ponds Agency. The EEMs, a program of Environment Canada, are a series of measurements put in place to gauge the efficiency of the 'Pulp and Paper Effluent Regulations' and the 'Metal Mining Effluent Regulations', both part of the federal 'Fisheries Act'.

Walker, with the perspective of an academic-turned-industry-consultant, turned back to academia, knows what would be required for a potential clean up. As importantly or more, Walker also knows the strengths and weaknesses of the current monitoring system at Boat Harbour. If the clean up of Boat Harbour is to proceed in good order, Walker has some advice for government – as well as those who would educate themselves towards monitoring the strength of the clean-up plan.

The first order of business, notes Walker, is to ensure that the proper measurement and threshold guidelines are in place.

Canadian Water Quality Guidelines, developed by the Canadian Council of Ministers of the Environment (CCME), are generally the 'go to' series of measurements by which water quality is measured in Canada. The CCME guidelines, however, don't capture the complete picture of what might be in Boat Harbour, says Walker.

“They're missing about seventy percent of the polycyclic aromatic hydrocarbons, PAHs,” says Walker. “The CCME guidelines also only contain about fifty percent of possible metals.”

Overcoming the limitations of the CCME guidelines, potentially by selecting data measurements from other jurisdictions, such as the United States' Environmental Protection Agency, is necessary says Walker, to ensure that the full picture of possible contaminants is captured.

Once a measurement set with expanded parameters is in place, the next step towards cleaning up Boat Harbour is to expand the sediment monitoring that actually occurs at the site.

Decade upon decade of sediment has gathered at Boat Harbour, not all of it at the same depths or concentrations. As it is, Walker notes that there are “about fifty” sediment monitoring stations at Boat Harbour. Using “point data” from these stations, a matrix-style map of Boat Harbour has been created.

The weakness of this matrix, to Walker, is twofold. More data from more stations is required to create a finer map of sediment concentrations, says Walker. Measurements to various depths, not simply “point data”, is also key.

“I would pitch that greater delineation is required, so more sample stations,” says Walker. “But not only that, because those are only point locations. In effect they are two dimensional. You almost need the three dimensional stations, because you've got a historical legacy of accumulation. You need depth profiling too.

“In Boat Harbour, what you have is horizontal horizons of different sediments. So you need to take subsamples every few centimetres of depth, that each represent maybe five or ten years worth of sediment accumulation. Then you could find out if there's any depth delineation that needs remediating, how deep do you go, as well as what's the surface area that you need.”

This enhanced matrix-style mapping of sediment concentrations precedes a process of selective dredging, the end result of which is a Boat Harbour returned to a tidal lagoon free of contaminants.

If the desired end result is a Sydney Tar Ponds-style mixture of concrete and contaminants, solidified to remove further contaminant migration, then Boat Harbour would eventually look like something very much different than what it once did.

Enhanced mapping of Boat Harbour, while time consuming at the initial phase, would inevitably pinpoint eventual dredging activities, and minimize the amount of contaminated sediment to be sent elsewhere for containment. In effect, the “clean up” as it were, is simply a removal of contaminants. The contaminants themselves will live on, just in another, contained, location.

Dredging, transport of contaminants and containment, will be the 'big ticket' expenditures related to the clean up, notes Walker:

“What you have to do then is transfer all that contaminated material to containment cells, which is more expensive. You can't just put it in the regular landfill like we have in HRM. It requires further transportation. Each truckload is of a magnitude more expensive than non-contaminated waste. So there's a big cost associated with that, but still it can be done.”

As for the possibility of phytoremediation, the process of using plants to uptake contaminants, Walker suggests that it is “one tool in the toolbox”. The main process, however, will likely still be large-scale dredging.

All of this, however, precedes the serious conversation of what the mill will use as an effluent dumping ground once it is redirected away from Boat Harbour. We have written earlier about a variety of hypothetical options available, and the price tags attached to each. A 'sludge treatment system' located on site at the mill was estimated to cost, in 2012, $45.9 million, and would take upwards of 36 months to build.

Whether this on site system would become a closed loop for the approximate 70 million litres of fresh water that the mill currently uses per day is unknown.

To Recap on cleaning Boat Harbour:

• Expanded measurement guidelines, with a farther reach than CCME water quality guidelines.

• Finer matrix, three dimensional, sediment testing.

• Selective dredging, removal and managed containment of highly contaminated sediments.

• Some degree of phytoremediation.

• Break down of dams and obstructions that currently impede tidal inflow and outflow.