Rectification Projects
Addressing Civil Non-Compliance Issues in WSUD Systems
BiOSTREAM RECENT PROJECTS •
BiOSTREAM RECENT PROJECTS •
NON-COMPLIANT CIVIL WORKS | example one
The following WSUD system was made up of three in line biofiltration basins each requiring civil rectifications – we identified two basins as requiring an extensive acid sulphate management program with one requiring significant groundwater and scour management.
All three differing levels of bio media replacement along with bio media de-compaction to reinstate permeability
Step one:
basin with sacrificial layer removed.
Step two: Acid sulphate barrier installed
Progression of acid sulphate through the basin.
The developer engaged a geotechnical company who designed an inspired acid sulphate barrier to neutralise acidity levels. We then, through multiple inspections, insured that barrier was installed to specification. To this day the barrier is still working efficiently protecting the downstream habitat and waterways.
After all treatment and civil rectifications were complete:
Re-constructed - Re-planted and Fully Functional Bio Filtration Asset:
OTHER NON-COMPLIANT CIVIL WORKS
The following examples are from separate projects with significantly non-compliant civil works. Vigilance through asset inspections is essential to ensure these practices are rectified prior to being covered over and are not repeated.
Undetected poor-quality construction practices like these lead to asset failures, costly, unnecessary rectifications, repairs and replacement. In the worst case scenario due to inhibitive rectification costs they are left to never function as an environmental water quality stormwater treatment asset.
OTHER NON-COMPLIANT CIVIL WORKS | example two:
Drainage pipe work – Collector and slotted pipes not primed and glued as a standard industry requirement. Pipes joined with bitumen tape, broken collector end cap had a rag stuffed into it not replaced. The outcome? All previously installed basin infrastructure was removed and replaced prior to the final buildout.
NON-COMPLIANT CIVIL WORKS | example three:
Flow on effects of non compliant civil construction - Floor not constructed to design grade, outlet gully pit stub too high, in turn the basin collector becomes too high at the far end from the gully pit causing the slotted pipe sit approximately .300mm above the basin floor (this asset was not designed as a saturated basin). For some reason builders plastic was laid over the geofabric and joined with duct tape.
Outcome: Pipework, geofabric and plastic removed, floor reconstructed to design levels, geofabric, collector and slotted pipe re-installed with slotted pipe sitting flat on the basin floor as per the approved hydraulic and construction design.
NON-COMPLIANT CIVIL WORKS | example four:
Bio filtration basin with impermeable liner specified, with either a high density poly liner or a bentonite clay liner to be installed, following the supplier specification. In this example, the basin floor was not correctly prepared with multiple obtrusions likely to pierce the liner, however the most significant problem was that builders plastic was installed using duct tape to join and seal the sheets together instead of using one of the above mentioned impermeable liners.
Outcome: Basin batters and floor were not compacted and failing resulting in the total removal of all materials that had been installed, the basin floor was re-excavated with compactible materials imported and recompacted, basins batter material was removed, replaced and re-compacted followed by re-installation of a hi-density poly liner and replacement of previously installed pipework.
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