Attachments 11.4 and 11.5 - City of Busselton

ATTACHMENT C - TREATMENT OPTIONS CONSIDERED IN THE COUNCILLOR WORKSHOP OF MAY 2011
ITEM 11.4 COUNCIL 12/10/2011
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River Bank Re-instatement
This option, as detailed on the plan in attachment B, proposes reshaping and
revegetating the last remaining section of riverbank on the northern side of
the river along Peel Terrace.
The Council of the day held off doing this section as there was some
objection to the replanting that was being done along the banks because of
the perceived loss of views of the water. While some sections have been
densely planted (these areas provide good habitat for waterbirds and aquatic
fauna) there are others that were planted with rushes and sedges and these
do not block the views of the water. There is now less objection (anecdotal)
to the idea of planting the remaining section of riverbank. The Geographe
catchment council has discussed the proposal to complete this final section
and were generally supportive of the design proposed.
The design arose from the issue of undercutting of the bank at the eastern
end near the railway bridge. It was suspected that exposure of ASS caused
slumping of the soil structure and subsequent erosion.
The solution proposed is to pack the undercut section with a blend of
organic matter and limestone (to neutralise any subsequent effects of
acidification), and place fill along the edge of the bank to get a more stable
batter of soil to plant into and create beach access points. The design
addresses the undercutting problem, provides a natural edge to the river,
and provides vistas of the water body.
This project will not solve the WQ issues of the river but completes the
objective to get a natural edge to the river and will make this section of the
river much more presentable. The project needs to be properly costed and
funding sought to assist the Shire to carry out this project. Aboriginal
consultation has been done but approval (bed and Banks) will be required
from the Department of Water.
Sewerage in-fill
This is not a treatment option so much as a prevention strategy which helps
to reduce the amount of nutrients getting into the water body. This
recommendation was made strongly at the beginning of the workshop by
the Department of Water staff present. The point was made that there is
enough nutrient coming from any one of the current sources of nutrient
(surface run-off, groundwater and sediments) to produce algal blooms in the
river and that the longer term solution is to cut off the nutrient inputs from
all sources.
Nutrient levels in groundwater around the Lower Vasse River are largely
attributable to the use of septic systems and leach drains in the light
industrial area where the groundwater levels are very high in winter. The
systems are often submerged in groundwater in winter whereas they should
be 1.2m above the watertable to work properly. The preferred solution