Stage 1 HDPE – High Density Poly Ethylene
Stage 2 LLDP – Low Linear Density Plastic
Cleaning and regeneration of the Kopeopeo canal has been a significant project for the Bay of Plenty that I.S. Dam Lining is proud to be part of.
The Kopeope canal extends from the Rangitāiki Plains to the west of State Highway 30, running east where it joins the Orini Stream and then discharges into the Whakatāne River.
The canal was constructed during the 1920s to convey drainage and floodwaters from low-lying farmlands in the Rangitāiki Plains into the Whakatāne Estuary.
The canal was contaminated between the 1950s and late 1980s as a result of stormwater discharges from a former sawmill, which treated timber using Pentachlorophenol (PCP). While unknown at the time, PCP included a percentage of impurities that contained dioxins.
The canal cleaning and regeneration project will take a staged approach to remove, safely store and treat up to 40,000cu m of contaminated sediment across three sites.
Works were to begin in 2014; however the community raised concerns about the original methodology (excavators and trucks) for removal of the sediment.
After a successful pilot study of a new cutter-suction dredge methodology in October 2015 a consent variation was submitted works were able to commence in May 2016.
The cutter-suction method virtually eliminates the heavy traffic and potential for spillages and associated dust generation. It also brings improvements to the containment site design which reduces potential groundwater and flooding related effects.
The sediment will be placed into geotubes (geotextile bags) which are placed within fully enclosed ‘containment cells’. I.S. Dam Lining has lined these cells using high density polyethylene (HDPE) liner for stage 1 and low linear density plastic for stage 2. Liner eliminates sediment-bound contaminants’ moving into the surrounding soil or groundwater.
Geotube bags are treated with bioremediation which enhances the natural degradation process. Contaminants are broken down naturally using a combination of fungi, bacteria and plants (poplars and natives) to degrade dioxins.
The Bay of Plenty Regional Council has estimated it will take 12 years of regular monitoring to assess progress until completion.