Rehabilitation

REHABILITATING LAC HENEY

When the class action was initiated, the Government engaged Dr. Richard Carignan (Université de Montréal) to undertake a thorough examination of the lake and the impact of the fish farm on water quality.  In his extensive report of 2003 covering the period May 2001 to July 2003, he studied the phosphorus dynamics in the lake and identified the principle sources of phosphorus (P) in addition to the fish farm.  Among his results, he identified the low levels of iron (an important component of the annual P cycle) in the lake and the release of P from the sediments before the water near the sediment became anoxic (lacked oxygen).  He suggested several means of reducing the entry of P into the lake but added that their impacts would be minor in this case and “uncertain”.

The APLH (Association for the Protection of Lake Heney) Environmental Committee (Peter Fitt, Kevin Bell, Graeme Kirby and a few other Board members) met several times with our chief scientist, Dr. Yves Prairie (Université du Québec á Montréal) and Dr. Carignan.  It became clear to us that the excess P added to the lake by the fish farm had lead to increased decomposition of organic matter at the sediment-water interface which used up oxygen and led to a greater release of P from the sediment than would be normal for our lake.  Several approaches to improving the situation were considered including aeration via floating devices and the addition of alum or iron to bind with P and keep it in the sediment.  The Committee also consulted specialists with Golder Associates on the current information on the lake available at the time.

With the settlement of the class action in June, 2004, a joint committee, the Comité paritaire, composed of representatives of the Association and the Quebec government, was established to manage $3,200,000 to be spent on the treatment, rehabilitation and protection of Lake Heney.  All decisions and actions undertaken by this committee were to be agreed to by both the APLH and the government.  Representatives of the Association included Graeme Kirby, Peter Fitt, Kevin Bell and Tom McKenna.  The government was represented by Marc Dubreuil, Direction régionale de l’Outaouais, and Yves Grimard, Direction du suivi de l’état de l’environnement, Ministère de l’environnement.

The Comité paritaire (CP) met regularly from June 2004.  While several options were considered, the CP focused on the addition of iron as a means of interrupting the downward spiral of P release from the sediment, excess algae during the summer, depletion of oxygen at the sediment interface and subsequent release of more P.  In the opinion of our scientists, the best approach would be the addition of iron chloride (FeCl3) in late fall, when phosphorus would be in the appropriate state to bind to the iron and sink to the bottom over the winter.  Two experiments were proposed to determine whether this approach would be effective and what the impact would be on the native flora and fauna in the lake and at the bottom.  Two cylindrical plastic corrals were suspended in the lake but were damaged during installation and did not provide sufficient isolation from the rest of the lake to provide useful results.  However, a trial in the Baie des prêtres in the north end of the lake was more successful.  A curtain was suspended across the mouth of the bay in the Fall of 2004 and approximately 5,000 kg of ferric chloride solution were added to the surface of the bay via a pontoon boat to i) determine the chemical efficiency of the treatment, ii) to determine the settling time of the newly formed iron hydroxide and iii) determine the occurrence of adverse biological effects due to the iron treatment.  The experiment was a success.  It showed that the iron hydroxide (formed when the iron chloride mixed with the lake water) would settle quickly but that the treatment needed to be done later in the year when the autumnal transformation of P would complex more completely with the iron hydroxide.  The experiment also showed a minor but only temporary change in acidity .  In April 2005, chlorophyll levels dropped as expected and no significant impact was detected on microbenthic (bottom dwelling microorganisms) populations and fish mortality.

Meanwhile, toxicological testing undertaken by a division of the Ministry indicated that the addition of iron chloride could impact living organisms such as plankton (algae, on which fish and other small organisms feed) and small species living near the sediment.  The Baie des prêtres test demonstrated clearly that the iron chloride was transformed quickly into iron hydroxide – an innocuous form – and would not have a detrimental effect on lake organisms.  Also, Carignan and Prairie conducted sediment analyses and a hydrodynamic study of the currents in the lake and various methods of spreading the iron chloride were considered: helicopter, barge, several pontoon boats, injection from several points on the shore and spreading on ice.

The Association’s Environmental Committee expressed concerns about the CP plans and wanted to see alternatives to iron considered, as well as a more project management approach including terms of reference, deliverables and timelines.  The need for outside reviewers was also raised.

In early 2005, a local firm, Fondex, was engaged to produce a synopsis of the current technical information and a review of techniques for spreading iron chloride. They also undertook a survey of septic systems around the lake, funded 50% by the CP and 50% by the Foundation.  Carignan was also asked to study the impact that logging in the watershed would have on the lake and his report was used by the Ministry to have Heney designated as a protected area against large-scale logging.

In October 2005, 6 firms were identified and asked to submit proposals for managing the treatment project.  In February 2006, three scientists were identified as external reviewers: Frances Pick (a limnologist at the University of Ottawa), Gertrud Nurnberg (a limnologist with a private environmental company in Dorset, ON) and Peter Campbell (a water chemist with the Institut national de recherche en eau, Québec).

A meeting was held in Montreal in May 2006 with all the key participants to review all of the information available and discuss options.  The conclusion agreed to by all was to proceed with a treatment with iron chloride.  Alum was also considered to be a strong possibility but environmental concerns favoured iron chloride.

After reviewing the submissions from the six  engineering companies, the two most promising were invited to make formal presentations to the CP in June 2006.  Envir-Eau, a division of Water and Earth Sciences Associates, was selected as the project manager.  It proceeded to obtain the appropriate authorizations for use of iron chloride and make plans for carrying out the actual treatment.

That summer, the Association hired a consultant to assist in preparations for two public consultations, one in French and one in English, that were held at Whitefish Lodge in the autumn.  All cottagers as well as the two municipalities were invited and the meetings were well attended.

Since iron chloride itself is highly corrosive, its handling was a key issue, particularly since the treatment would take place just before freeze-up.  It was decided that the best way to deliver it would be on a large barge.  Envir-Eau contracted Marine International Dragage Inc. (MID) of Sorel Quebec to provide the barge, 2 tug boats and the team to operate it, given the anticipated conditions.  The barge was delivered in 6 pieces and assembled at the property of Yvon Bastien Sport at the north end of the lake.  A temporary pier was constructed to facilitate the launching of the equipment and all subsequent moorings.  The assembly of the barge took place in October and was completed and tested on November 19.  Injection of approximately 1 600 metric tonnes of ferric chloride, containing 13% iron, began on November 20th and continued daily to December 6.  The chemical from Kemira of Varennes, QC, was delivered via train to Ottawa and transferred daily via tanker trucks.  Three large trucks were stationed on the barge and filled overnight for spreading during the day.  A pumping and injection system allowed a dilution of the iron chloride prior to being introduced into the water and a GPS system ensured full coverage across the lake.  The injection had to be stopped one day early because of ice conditions in the bay but the goal of 1.3 mg of iron per litre of lake water was achieved as required by Dr. Carignan’s calculations.

As soon as the iron chloride hit the lake water, the iron was transformed into iron hydroxide, which then formed a complex with the active form of phosphorus that occurred after the autumn turnover, i.e. when the water column was uniform.  This complex settled fairly quickly to the bottom of the lake, removing the complexed phosphorus from the water column so that it was not available in the spring when the ice went out and photosynthesis began.

Monitoring of the water quality as well as the impact of the treatment on benthic organisms was conducted over the summer of 2008. The iron treatment caused a marked decrease in total phosphorus (TP), where the weighted average concentration for the lake as a whole went from 22 µg/L (micrograms per litre) before the treatment to about 11 µg/L after the treatment.  No negative effects were observed on organisms living close to the bottom.

Despite a drop of around 50% in total phosphorous and in planktonic chlorophyll, the hypolimnetic  oxygen demand was only reduced by 28% in 2008 in comparison to 2007.  Such a response is normal because in lakes of an intermediate depth such as Lake Heney, an important proportion of the oxygen demand comes from the organic matter accumulated over the years in the sediments.  It would take another several years before an improvement would be seen in the quality of the environment for cold water fish.

The decrease in phytoplankton was also accompanied by an equivalent and normal drop in the amount of zooplankton (small aquatic species).  However, the abundance of benthic (bottom dwelling) invertebrates, which are the principal food source for the majority of fish and their prey, was little changed between 2007 and 2008.  The resilience of the benthic community from the iron chloride treatment and the subsequent improvement in water quality indicated that any toxicity of the treatment was negligible and that these communities, which depend on the resources (primary production and benthic organic carbon), simply needed a certain time to adjust to the new conditions observed in the water column.

Throughout this period, Association member Tom McKenna was a key intermediary with the environmental engineering companies while Kevin Bell interacted closely with the scientists.

“The overall cost of the treatment was $2.1 million, leaving $1.2 million in reserve for ongoing monitoring, rehabilitation of the lake and conservation of its ecosystem, and against the possible need for further treatment.”

Ongoing yearly monitoring showed an upward trend in average total phosphorus in the early spring and late fall from 2009 through 2014, although mid-summer readings were below the target of 15 µg/L agreed to in the settlement.  This was not surprising as there was still a considerable amount of organic material at the sediment that was decomposing, using up oxygen and releasing P back into the water column.  However, by 2014, the upward trend stopped and the lake seems to have stabilized with good water clarity in the summer and limited algal growth until late fall.

Kevin Bell

August 2018