RFI - Stormwater Mgm Plan 20169 - SBSMP - Rev 4 (2)

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1 INTRODUCTION
The water quality treatment for the proposed development includes a proposed bio-retention
basin. This document provides an overview of the maintenance requirements for the bio-
retention water quality device(s) on site to ensure that they are properly maintained.


2 GENERAL
Bio-retention basins are vegetated areas where runoff is filtered through a filter media layer
(e.g. sandy loam) as it percolates downwards. It is then collected via perforated underground
drains and flows to downstream waterways or to storages for reuse. Bio-retention basins
operate by filtering stormwater runoff through densely planted surface vegetation and then
percolating runoff through a prescribed filter media. During percolation, pollutants are
retained through fine filtration, adsorption and some biological uptake. The vegetation in a bio-
retention system is a vital functional element of the system providing a substrate for biofilm
growth within the upper layer of the filter media. The proposed bio-retention basin within the
site will do much of the same. It has been designed to reduce the impact of the development
on the downstream waterway environment.


3 RESPONSIBILITY FOR INSPECTION
The principal involved consultancy will be required to appoint an appropriately qualified
consultant maintenance contractor to carry out the inspections of the bio-retention basin
during the construction and on-maintenance period. At the completion of the maintenance
period the responsibility to undertake the inspections and generally maintain the basin will be
shifted to Body Corporate.


4 DATA COLLECTION / STORAGE REQUIREMENTS
Inspection records will be required for comparison of the performance of the system. In order
to assist this process it is proposed that the Bio-retention Basin Maintenance Checklist prepared
by Healthy Waterways (2006) be adopted for the site. Refer Appendix A for a copy of the
checklist.

Copies of the completed checklist are to be forwarded to the Morgan Consulting Engineers (or
other consultant nominated by the Principal) and to be provided to Council at the expiry of the
maintenance period and on request thereafter.


5 MAINTENANCE PROCEDURE
5.1     General
Vegetation plays a key role in maintaining the porosity of the filter media of a bio-retention
basin and a strong healthy growth of vegetation is critical to its performance. Therefore the
most intensive period of maintenance is during the plant establishment period (i.e. first two
years) when weed removal and replanting may be required.



Bio-Retention Basin Operational Management and Maintenance Guideline