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Midshipman Fish with Yolk sac Porichthys notatus Keyhole Limpet Diadora aspera Midshipman Fish Embryos Porichthys notatus

Purple sea stars Pisaster ochraceus


Howe Sound

Map of Howe Sound

Seven Howe Sound Quadrat plots were surveyed in June from 1990 to 1993 and 2004. These sites are as follows with the distance from the mill.

Changes In Howe Sound Sites Over a Decade

Over the past decade the effluent quality at Port Mellon, Howe sound has improved. (See Figure 1) Species richness at Howe Sound sites over the same time period have increased. (See Figure 2.)

Effluent Quality in Howe Sound

Figure 1: Annual Average Effluent Quality for Howe Sound Pulp and Paper Partnership mill in Port Mellon, Howe Sound. (BOD=Biochemical Oxygen Demand, TSS=Total Suspended Solids, AOX = Adsorbable Organic Halides). Data kindly provided by Environment Canada, Pacific and Yukon Region, Environmental Protection Branch and Hatfield Consultants Ltd., 2004.

Howe Sound Intertidal Species Richness

Figure 2: Howe Sound Intertidal Species Richness. Mean species richness was significantly greater in 2004 compared to 1990-1993 for Howe Sound Z(6) = 0.02, p<0.05 ( Chaster Beach excluded). (*) indicates a significant linear increase in species richness from 1990 to 2004 at individual sites ( p<0.05). (Bard, Shannon, De Raedemaecker, Fien and Willems, Wouter. (2005 Submitted) "A Decade Later: Intertidal diversity is increased as pulp mill pollution is decreased." Water Environmental Research Journal.)

The Howe Sound Mills


The Western Pulp Limited Partnership mill (hereafter called the “Woodfibre mill”) is located in Woodfibre, on the western shore ofupper Howe Sound, just within SquamishHarbor. Pulp was first produced in 1912 through the calcium sulphate cooking process. In 1938, pulp bleaching started, using elemental chlorine and calcium hypochlorite. During a shutdown in 1958, conversion to the Kraft process and installation of a chlorine dioxide generator took place. In the Kraft process, pulp is produced by cooking wood at high pressure and temperature with the use of sodium salts in an alkaline medium. Production resumed in 1961 and the recycling of cooking chemicals lowered pollution loads. Until January 1986, the effluent was discharged at the surface, thereafter effluent was disposed of through four diffusers spaced at intervals of 25 m and extending 27 m from the shore at a depth of 22.5 m. Since 1986, a primary clarifier removed settleable solids, greatly reducing TSS. Since 1988, 30 % of elemental chlorine was replaced by chlorine dioxide in response to organochlorine concerns. Recovery systems for fiber and process chemicals were improved in 1989, leading to a further decrease in TSS. A major decrease in the use of chlorine took place in 1987. From 1990 onwards the level of chlorine dioxide substitution was increased to 50% and only residual chips from off-site sawmills were used, putting an end to the presence of log booms in waters adjacent to the mill. After treatment in the primary clarifier, effluent is cooled and neutralized by adding lime slurry. pH of the primary effluent can be adjusted using caustic (NaOH) or sulphuric acid, as well as nutrients such as anhydrous ammonia and phosphoric acid can be added to sustain the biota within the biobasin. Installation in December 1992 of the Oxygen Activated Sludge (UNOX) biological effluent treatment system, reduced BOD drastically. In the UNOX system, effluent enters the biobasin where biological treatment takes place. After the biosolids (soil-like residue of materials) are removed in two 55 m diameter secondary clarifiers, effluent is discharged through the diffuser. During the time of the intertidal study (1990-1993) effluent volume was approx. 70000 m 3 /day. In the Woodfibre mill twenty spills occurred in 1988, releasing at least 40000 liters of fluid of varying consistency and toxicity, directly into the surface water near the mill (Hatfield 1994). Fourteen spills happened in 1989 (total of >30000 l), seven spills in 1989 (total > 7000 l), five in 1991 andtwo in 1992 and in 1993 (Hatfield, 1994). Additionally, a spill of 20000 liters of sodium chlorate occurred in 1989 and a similar spill of 2000 liters occurred in 1990 (Hatfield, 1994). The impact of these spills is unclear, but as they are released directly in the

surface water, contact with intertidal biota can be expected.

Port Mellon

The Howe Sound Pulp and Paper Ltd. mill (hereafter called the “Port Mellon mill”) is located at Port Mellon, on the western shore of the Thornborough Channel (Fig. 7). In 1908 it commenced as a soda pulping operation, and was converted to Kraft in 1916. The production of semi-bleached pulp took effect in 1954, while fully and semi-bleached pulp production commenced from 1962 onwards (Hatfield, 1994). As a consequence, the discharge of AOX and dioxins/furans probably began around 1962. This is confirmed by MacDonald et al. (1992), as 2,3,7,8-TCDF, a known product of chlorine bleaching has been found in a sediment core near the Port Mellon mill as from 1965. Chlorine dioxide substitution of elemental chlorine increased to 50% in 1989 and as a consequence AOX levels dropped. Primary and secondary effluent treatments were installed in September 1990, reducing the BOD, TSS and AOX dramatically. The production of newsprint started in 1990 with the addition of a thermomechanical pulp machine, which mechanically grounds chips to pulp, instead of the chemical digestion in the Kraft process. No chlorine is used in the newsprint production. In 1991 a first run of Total Chlorine Free (TFC) pulp was produced, the first in North America . During the intertidal sampling, only residual chips from sawmills in the Vancouver area were used. The effluent treatment system is very similar to the one used in the Woodfibre mill, including a primary clarifier, a UNOX biobasin and two secondary clarifiers. Similar effluent cooling and pH adjustments also take place. Effluent, 65000-70000 m 3 /day on average, was discharged through two surface outfalls (acidic and alkaline) into a small bay west of the mill until November 1982, when a submarine diffuser was installed. The diffuser extends 277 m into the Sound and effluent is released through six diffuser ports at depths ranging from 30 to 115 m. Spills of process chemicals and untreated effluent to the surface water near the mill also occurred in the Port Mellon mill (1989: 2 spills, 25000 l; 1990: 5 spills, > 505600 l, 1991: 3 spills, >250000 l; 1992: single spill of 400000 l) (Hatfield, 1994). A major spill of 45000 l sodium chlorate occurred in 1993, while no further spills were reported in that year (Hatfield, 1994).

This text is an excerpt from Wouter Willem's 2004 master's thesis "A GIS-approach to assess the impact of two pulp mills (Woodfibre and Port Mellon) on intertidal biodiversity in the Howe Sound region (British Columbia, Canada)". Click here for the entire document and to view sources.


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Midshipman Fish with Yolk sac Porichthys notatus Keyhole Limpet Diadora aspera Midshipman Fish Embryos Porichthys notatus

Purple sea stars Pisaster ochraceus

All images ©2004 Shannon Bard. Use of images is prohibited without permission.