Contributor: Karolyn Sweeting
Location: Lower Mainland, British Columbia
Land Use: Settlement
Habitat Type: Watercourse/Riparian
Project Timeline:
Highlights
A summary of environmental mitigation measures undertaken by the Ministry of Transportation (MoT) during the building of the Alex Fraser Bridge and the Annacis Bridge Crossings to ensure that fish and fish habitat were not adversely affected. The Annacis Crossing Project was the first implementation of the “No Net Loss” objective for a major project in BC.
The Annacis Crossing Project, completed in 1986, was one of the most complex, diverse engineering and environmental challenges undertaken by the Ministry in its history. The study area covers the three low-level bridges crossing the Annacis Channel, and the Alex Fraser Bridge crossing the Annieville Channel located upstream of the mouth of the Fraser River. The Alex Fraser Bridge crossing had one of the greatest potential environmental impacts on the adult migratory fishery resources of the Fraser River. Concern stemmed from the fact that the Fraser River maintains the second largest salmon run in the world and the reduction of the low velocity zones along the margins of the river could impede upstream fish migration during high discharge events. The river supports five species of Pacific salmon; Chinook, Chum, Sockeye, Pink, and Coho, which provide major commercial, sport and native fisheries. Following discussions with Fisheries and Oceans Canada (DFO), there was agreement to implement the “No Net Loss” objective. The goal was to improve habitat development at the crossing sites in the tidal and upper salt wedge area of the Fraser River, an area that greatly influences salmon migration.
Project Objectives
- The Ministry’s primary objective was to have a “No Net Loss” of fish and fish habitat. The Annacis Crossing Project was the first major project in BC to implement the “No Net Loss” objective.
- To develop habitat to assist fry and juvenile salmon in the estuary while they undergo the physiological changes to live in salt water.
- To ensure water velocities in the Annieville Channel facilitates fish passage.
- To assess and ensure the stability and growth of riparian and inter-tidal vegetation along the Annieville and the Annacis Channels.
- Several compensation sites were sought along the Annacis Channel to develop two sites for rearing and feeding juvenile salmon in the area between the east and west bridges and the Patrick Bay Habitat Development area.
- To prevent the future loss of fish and wildlife habitat along the Annacis and Annieville Channels. Back channel holding areas critical for juveniles and fry holding must be preserved as well as future opportunities to construct other fish and wildlife habitat.
- To restrict public access to the compensation habitats in order to avoid contaminating it with the dumping of refuse and off-road vehicle use.
- To maintain the existing Annacis Channel compensation site by monitoring water velocity and food supply, as well as ensuring suitable cover, water quality, and temperature.
The Ministry of Transportation identified and mitigated fisheries concerns for the Annacis Crossing Project in three stages; pre-construction, construction and post construction.
In the pre-construction phase, the Ministry sampled up and down both the Annieville and Annacis Channels looking for suitable locations for bridge construction while minimizing the impact on fish habitat. Habitat sites were selected based on the results of fisheries studies and site inspections. Preliminary data collection was undertaken to monitor fisheries resources, to analyze migration passages and to assess habitat locations. Projected losses of each habitat type were calculated, and mitigation as well as compensation measures were developed. The Ministry engaged in consultation with DFO to ensure crossing designs and bridge construction activities were compliant with the Federal Fisheries Act.
During bridge construction, the Ministry was involved in on-going consultation with DFO about compensation plans for channel encroachments and wetland infilling.
In the post construction phase, habitat losses and gains were assessed, and ongoing monitoring programs were implemented. Site reviews were conducted in three, five and 15-year intervals to observe the long-term effects on the compensation habitats and to follow-up on bank and channel stability in order to determine the success of the riparian transplantation.
Pre-Construction
Prior to the bridge construction, a series of fishery studies were conducted to assess the natural distribution of aquatic habitats for salmon and other resident species along the Annieville and Annacis Channels. Four seasons of data were collected to aid in developing mitigation and compensation design strategies. To estimate the area of fish habitat at each of the bridge sites. The aquatic and near shore habitats were divided into five categories:- Sub-tidal areas submerged under multi-tidal and discharge conditions
- Intertidal mudflats
- Intertidal low marsh
- Intertidal high marsh
- Riparian.
The estimation for the total area of fishery habitat losses along the Fraser River after construction would be 38,000m2. To compensate for these losses, MoT developed a habitat compensation plan.
DFO’s concern was that the sand islands reduced the cross-section of the Annieville Channel by 23% and would affect salmon migration during high discharge events. An extensive modeling study was undertaken to assess velocities at various tidal and discharge conditions. The studies indicated that water velocities could be sufficiently high, that during a period of high discharge, salmonids might be required to utilize lower velocity areas near the banks in order to minimize the energy expenditure required for navigating upstream. The Ministry modified the design of the pier protection structures (sand islands) to include the construction of four large groynes. As a mitigating measure, the groynes were incorporated into the design of the sand islands to create slow velocity eddies along the edge of the sand islands with smaller areas of high velocity at the end of the groyne tips.
Prior to construction, it was assumed that sediment deposition would result in the lee areas of the sand islands and in the upstream section of the structures. The anticipated infilling would result in shallow inter-tidal habitat. Also, because of industrial infilling and refuse disposal, the quality of habitat at the Alex Fraser Bridge site was poor. It was proposed that rather than meet “No Net Loss” on an aerial replacement basis, that assessing impact, mitigation and compensation designs should be on the basis of carrying capacity or productivity.
Construction
Fish habitat was assessed between 1983 and 1989 along with monitoring of land changes as a result of bridge construction. Along the Annacis Channel, new forms of bank protection and crossing sites were introduced to compensate for habitats that were destroyed from municipal sewage output resulting in the lowering of water quality and affecting salmonid rearing capabilities. Other changes along the channel habitat included the creation of new spawning channels, juvenile fish passage structures, excavation of tidal marsh areas and extensive marsh and riparian transplanting (Harder, 1999).In 1984, the Ministry of Transportation excavated South Sand Island due to the lack of available compensation sites along the Annieville Channel. This created an inter-tidal area of 8,000m2. An inter-tidal carex marsh was planted over 70% of the back-channel site.
In 1985, to compensate for channel encroachments and wetland infilling, MoT purchased a former industrial property, Patrick Bay, and excavated 15,000m2 to develop a new habitat area. The estimated compensation habitat gains were 4,400m2 in intertidal mudflats, 1,530m2 in intertidal marsh, 8,200m2 in sub-tidal area and 363m2 in riparian length. In October of that year, 2501 root plugs were transplanted from two donor sites to increase vegetation in the area. The root plugs were Scirpus validus, Carex lyngbyei, Eleocharis palustris and Equisetum fluviatile. As a result, the Patrick Bay Development Habitat was capable of supporting 3,700 Chinook fry, 850 Chinook smelts and 2,400 Chum fry over prolonged use.
Post Construction
A post construction monitoring assessment completed the five categories of aquatic and near shore habitats. It was found that 37,830m2 of habitat was affected. The largest area of impact was a loss of 12,900m2 of intertidal mudflats. Other negatively affected areas were 5,860m2 of intertidal marsh, 8,900m2 of sub-tidal fringe and 10,170m2 of riparian land.Monitoring of velocities and radio telemetry of early Sockeye salmon runs were undertaken from 1984 to 1987 to assess the capacity of the salmon to migrate through the bridge. Water velocity measurements were taken using a boom arm device during the spring freshets and the fall Sockeye migration period. From 1984 to 1990, a salmon migration tracking study was performed to follow the movements of Sockeye salmon. 25 to 30 fish a year were radio-tagged.
In 1992, a 3,400m2 intertidal marsh was developed downstream of the Annacis East Channel Bridge and West Channel Bridge. This created a site adjacent to a small eddy current. High numbers of Chinook smelts have been observed in this area.
Initial Review
After the initial bridge construction, there were unavoidable losses of approximately 38,000m2 of fisheries habitat. That area was further divided into five categories to better estimate the effects on habitat. These were the sub-tidal areas, the intertidal mudflats, the intertidal low marsh, the intertidal high marsh and the riparian. The intertidal mudflat had the most impact, affecting an area of 12,900m2.Three Year Review
The four large groynes incorporated into the design of the sand islands of the Annieville Channel successfully reduced velocities and produced eddies along the edge of the sand islands. The results showed that velocities, on average, were 50% less than those predicted indicating fish passage was not a problem.The Patrick Bay Development Habitat, purchased by MoT, created more sub-tidal and intertidal habitat to compensate for losses. In June 1987, most of the area was vegetated with naturally colonizing plant species rather than the transplanted root plugs because they were better able to establish their root systems.
Five Year Review
Excavations in the South Sand Island and in Patrick Bay resulted in improved fish and habitat quality. South Sand Island resulted in an additional 8,000m2 in compensation habitat. Marsh vegetation was successfully established on 70% of the site. The land itself remained stable with no indication of erosion.3,400m2 of intertidal marsh was developed downstream of the Annacis Channel creating foreshore habitat for juvenile and fry salmonids. The most productive habitat was found at the southern tip of Annacis Island.
The salmon migration tracking study that ran from 1984 to 1990 indicated that a majority of fish went through the central and southern regions of the river. Other fish migrated along the face of the South Sand Island when moderate to high discharge events occurred. This study supported that water velocity at the fish passage through the bridge opening was not a concern. Monitoring the long-term effects of the project will assist MoT with future fish habitat development projects.
Fifteen Year Review
A 15 year review was undertaken to monitor how the habitat compensation sites and their productivity have changed or evolved over time. The Annieville and the Annacis Channels have had net gains in habitat development. The excavations at the South Sand Island and the excavations at the Patrick Bay Habitat Development site have resulted in improved habitat quality and fish productivity in the sub-tidal and intertidal mudflats. Riparian habitat values have increased and showed signs of progressive growth. The net gains of each habitat area were as follows:- Intertidal mudflats: 3,575m2
- Intertidal marsh: 924m2
- Sub-tidal area: 742m2
- Riparian (shoreline) length: 833m2
- Intertidal riprap: 1,442m2.
Changes in water velocity and flow patterns at the North and South Sand Islands resulted in increased sediment deposition. The rock spurs along the face of the South Sand Island resulted in low water velocity areas, providing habitat for rearing fish.
The intertidal section of the South Sand Island remained stable and there was no indication of erosion. There was been some sediment deposition and accumulation in this section, creating an additional 1,500m2 of intertidal mudflats. The intertidal marsh community was well established, including a successful establishment of marsh plants such as Typha latifolia along the southeast shoreline.
In summary, the mitigation and compensation measures have provided for high productivity of salmonids and other species in the lower Fraser River.
In order to continue protecting the habitat in the Annacis and Annieville Channels of the Fraser River, further land enhancement needs to be accomplished to ensure the survival of salmonid species. Marsh and aquatic vegetation have to remain established to stabilize the substrate and to offer protection in minimizing the effects of erosion. If it is found during periodic monitoring of the site that vegetation is not stabilizing, further enhancement has to be done.
Other areas that need to be addressed are bank protection, commercial development and sewage maintenance.
Acknowledgements
1999 nominee for the Transportation Association of Canada (TAC) Environmental Achievement Awards. This award recognizes the outstanding environmental contribution by a TAC member in the provision of transportation services.
Contacts
Ministry of Transportation
Environmental Services, Engineering Branch
Mike Kent
Chief Environmental
940 Blanshard Street
Victoria, BC Canada
V8W 9T5
Phone: (250) 387-7768
Email: Mike.Kent@gems1.gov.bc.ca
Fisheries and Oceans Canada
Land Use Section
Bruce Reid
Section Head
100 – Annacis Parkway, Unit 3
Delta, BC Canada
V3M 6A2
Phone: (604) 666-0514
Email: reidbru@pac.dfo-mpo.gc.ca
Partners
Bruce Reid, Section Head, Land Use Section, F&OC (604) 666-0514 agreed to review the Annacis Case Study. A copy was forwarded to him on August 1st, 2001. Many attempts were made to contact Bruce Reid to obtain his comments; however, as of November 2, he has been unreachable. This case study has been reviewed by Mike Kent and Chris Zacharias for content and consistency and is hereby submitted for review by the Stewardship Centre.
Ministry of Transportation
Environmental Services, Engineering Branch
Mike Kent
Chief Environmental
940 Blanshard Street
Victoria, BC Canada
V8W 9T5
Phone: (250) 387-7768
Email: Mike.Kent@gems1.gov.bc.ca
