History of the Site

Mud Creek is located along the Alouette River and is excluded from public access due to it being on a BC Hydro road up to the Alouette Dam. This project seeked to address the issue of the Mud Creek sediment pond which collects debris (e.g. fines, and small gravels etc) from Mud Creek which flows down from west-facing side of Blue Mountain and into the South Alouette River. Numerous monitoring studies take place on the South Alouette River including the Alouette Sockeye Adult Enumeration, Kokanee Out-migration, and Substrate Quality. The operation of these monitors could potentially be at risk if there is a failure of the Mud Creek sediment pond to capture debris from the high flows down the hillside and creek. In addition to this, the Allco Fish Hatchery is located approximately 4 kilometres downstream from the creek and could be at risk of its river pumps silting up if large amounts of fines were deposited in the South Alouette at the mouth of Mud Creek and subsequently washed downstream.

Figure 1. Aerial view of the Mud Creek Area

Goals and Objectives

The Mud Creek Sediment Pond project plan identified five strategic objectives to reduce sedimentation entering the Alouette River:

  1. Excavate up to approximately 1,500m3 of fill from Mud Creek sediment ponds during the dry season
  2. Replace/refurbish the wooden weir at the base of the sediment pond and deflection structures within the sediment pond
  3. Conduct water quality and turbidity monitoring
  4. Trial of soil erosion control methods with bioengineering
  5. Increase public awareness around benefits of minimizing pollutants, sediments and other deleterious amounts of materials from waterways.

Methods of Project

Direct coordination with an onsite project coordinator and environmental management began in early spring to ascertain the appropriate worksite practices, timing of the work to be completed, the removal of the spoils and any mitigation measures around sediment or Species at Risk as necessary.  Engaging the contractor to excavate approximately 5 years’ worth of fill from Mud Creek including fines, gravels and other materials will commenced on June 8th, 2015.

Pre-excavation turbidity monitoring using volunteers commenced during May downstream from Mud Creek and at the Allco Hatchery to gather data relating to the amount of instream sediment flows from Mud Creek in the spring.  The early surveying was responsible for the decision to start as early as June 8th due to the severe drought conditions.  Because of this drought water diversion and moving aquatic species became unnecessary saving a lot of time. 

The Alouette Watershed Species at Risk (AWSARS) team came out on three separate occasions to view the site for presence/absence of species at risk.  The team visited before the excavation, during excavation, and upon completion.  Since the spring and summer of 2015 were extremely dry, there was very little to any water in the sediment ponds.  Therefore, we did not need to remove any tadpoles or frogs from the site during excavation. During the week of June 8th-12th, Mission Contractors was engaged to remove sediment from the Mud Creed ponds.  Mission moved 150 loads x 11m3/load for a total of1650 mᶟ via a John Deere 250 D Rock Truck and another 100 loads x 7mᶟ/load for a total of 700 mᶟ by Volvo dump truck.  The total amount of total sediment removed was 2350m3.

Figure 2. Mud Creek before excavation
Figure 3. Mud Creek before excavation
Figure 4. Mud Creek after excavation

Mud Creek sediment ponds are temporary basins built on the bottom of an eroded slope side to capture disturbed soils and silt that is washed downward during rain events. This design is put in place to protect the water quality of nearby rivers, streams or lakes, in this case the South Alouette River, and subsequent impacts of multiple species spawning and rearing habitat. At the base of last sediment pond, before entering the South Alouette River, there is a weir which acts as a dam, pooling water behind it while also allowing water to flow steadily over the top. Mud Creek sediment ponds have been maintained for over 20 years. However because the ponds are constantly filtering and being filled with sediment they must be excavated every six to seven years. In June of 2015 there was a total of 2350 cubic meters of sediment removed from the site as shown in the before and after pictures.

Water quality was taken during the excavation process in 2015. Each of the days surveyed were tested directly off of the slope where the excavation took place. This location has a high canopy coverage and therefore the temperatures on both dates have remained fairly consistent, noting the consistency of the time of day as well. Dissolved oxygen levels show a
stable and healthy condition to support diverse aquatic life. Conductivity was recorded at 10.3µs/cm which is low however is consistent throughout the Alouette River as the dam holds back much of the sediment that travels down from the head waters. pH is at a prime level and turbidity is low, which is great, but did slightly increase after the excavation
process.

Species at Risk

A Species at Risk assessment was done in order to see what species would be impacted from the excavation. There were three species found, the Western Chorus frog, the Tailed Frog and Pacific Water Shrew.

The Western Chorus frog is a part of the tree frog family and its various species are found across Canada. They predominantly inhabit woodland ponds, similar to that of Mud Creek. The average length of an adult is 2.5cm and weighs approximately 1gram. The Pacific Tailed frog is unique to British Columbia. The most remarkable feature of this frog is the “tail” which is actually a copulatory organ used to fertilize the eggs the female internally. Chorus Frogs were found spawning at Mud Creek. Egg clusters were found densely spread all over the sediment pond area. Tadpoles were also found in May, and the creek dried up quickly so they were cut off and had nowhere to go. Many were safely relocated up to the stream area.

Tailed Frog Tadpoles were found mostly directly under the culvert and throughout the stream until it exited into the sediment retention area. They cling to the rocks located in the stream. They were also found above the culvert upstream from the excavation area.

The Pacific Water Shrew was not seen, but the location of Mud Creek is within its sensitive habitat. They can be found along the Pacific coast from Northern California to Southern British Columbia. They are in fact, only found in the lower Fraser Valley in BC and are a threatened species in British Columbia due to habitat destruction.  This makes them one of the rarest small mammals and have probably always been uncommon. They have been classified as a threatened species since 1994, in Canada.

Figure 5. Western Chorus Frog
Figure 6. Pacific Tailed Frog Tadpole
Figure 7. Chorus Frog Mating

Trial of soil erosion control methods on the upper hillside of Mud Creek completed

Bioengineering can be defined as the use of living plant materials to perform engineering functions, from simple erosion control with grass and legume seeding to more complex slope stabilization with willows and other plants. Soil bioengineering techniques can be used to revegetate steep slopes, to treat seepage zones, to control surface erosion, and to mitigate riverbank erosion. For many restoration practitioners, this is a welcome change to the typical rip rap, and hard-engineered solutions we see. This slope is a pilot project, where we are investigating the use of vegetation to reduce sediment and erosion issues in Mud Creek. It is our hope that the willow stakes will grow into established shrubs over time, thus binding the soil and halting slope erosion processes.

One bioengineering class was led by Dan Stewart, BSc., Dipl. Tech. Restoration Ecologist, on bioengineering erosion control at hillside east of Mud Creek . This workshop was intended to demonstrate the principals of bioengineering for soil retention and to act as a trial for erosion control in the area.  Eleven volunteers attended the day class and a trial bioengineer erosion control method was installed on the cliff above the sediment control ponds using willow stakes.   

Figure 8. Bioengineering workshop with Dan Stewart, BSc., Dipl. Tech. Restoration Ecologist
Figure 9. Completed wattle fences made from willow to prevent soil erosion and increase slope stabilization

This project was supported and funded by: The Alouette River Management Society, BC Corrections, Fish Wildlife Compensation Project, BC Hydro, Department of Fisheries and Oceans Canada, Province of British Columbia, Pacific Salmon Foundation.