2020.11.30 - Response to further RFI - OPW200145

 vi) Section D – what is the batter width behind BOK (face of kerb distance shown) and what is the batter
     angle? Why can’t this biopod be shifted closer to the RP boundary to facilitate a more suitable batter
     given there is no footpath in this verge?
    Stockwell Response
    This basin is now relocated behind the footpath alignment along Hofmann drive and within existing Covenant J.
    The basin position outside the infrastructure service corridors should be referenced from IPWEAQ RS-100 and
    101. Please refer to Barlow Shelley Drawing 1856-SW22E.


vii) Given the steepness and shortness of many of the batters behind back-of-kerb, how is it proposed that
     these batters will be able to be vegetated? It is suggested that a maximum batter of 1 in 2 and minimum
     batter length of 0.5m is required to establish batter planting successfully.
    Stockwell Response
    Batter lengths behind the back-of-kerb are kept at 0.5m long minimum to ensure suitable planting width is
    available for vegetation retention of the shorter slopes. All bioretention devices do not have a greater batter
    angle than 1:2. Please refer to Barlow Shelley drawings 1856-SW19E - SW26E.


viii) Why has Basin 4A now been added and what other alternatives are available? This basin connection
      will be prone to blockage and will in any case receive limited flow due to the piped connection to the
      kerb. It appears there are limited alternative connection options due to the lack of available fall and
      presence of the footpath. An alternative location or increased size of other devices should be
      investigated.
    Stockwell Response

    As discussed with Council’s stormwater engineer, there is insufficient depth to pipe the stormwater runoff
    from the southern side of Hofmann drive treatment device with a vertical filtering mechanism and then
    collect it at the outlet to discharge to surface. This is in line with our discussion and Council’s agreement.




                              Figure 10: Barlow Shelley drawing 1856-SW20 E Section B

    The stormwater access to this treatment device has been amended to provide sufficient room for a
    225mm high reinforced concrete box culvert under the pedestrian footpath to drain the kerb and channel
    to the treatment device.
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