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.