Appendix D_Engineering Report

    Maintenance overview                                          Sediment settles to the bottom of the lower chamber
                                                                  by gravity forces. The circular design of the treatment
    To ensure ongoing long-term environmental protection          chamber is critical to prevent turbulent eddy currents,
    HumeCeptor® needs to be maintained (generally                 which inhibit the settling process.
    annually).
                                                                  During high flow conditions, stormwater in the by-pass
    The actual on-going maintenance frequency                     chamber will overtop the weir and be conveyed to the
    requirements will be determined through quarterly             outlet drain directly. Water flowing over the weir creates
    inspections undertaken during the first year. However,        a backwater effect on the outlet decant pipe (ensuring
    only an annual maintenance period is anticipated for          head stabilization between the inlet drop pipe and outlet
    most HumeCeptor® units installed within drainage              decant pipe). This ensures that excessive flow will not be
    infrastructure.                                               forced through the treatment chamber scouring or re-
                                                                  suspending previously settled material.
    Inspection can be performed by anyone, and procedures
    for inspection are provided in this document.                 The by-pass mechanism is an integral part of the
                                                                  HumeCeptor®, since other oil/grit separator designs and
    Generally, comprehensive maintenance is performed             proprietary devices have been noted to scour during high
    from the surface via vacuum truck. Companies capable          flow conditions (Schueler and Shepp, 1993).
    of performing this maintenance can be found in the
    Yellow Pages or online by searching sewer cleaning or
                                                                  Figure 1 – HumeCeptor® system operation during design
    liquid waste removal. If you require a list of contacts for
                                                                             flow conditions
    cleaning your HumeCeptor® please call your nearest
    Humes office.



    HumeCeptor® operation

    A HumeCeptor® unit can be divided into two distinct
    zones comprising:

    1.   A lower treatment chamber
    2.   An upper by-pass chamber


    Stormwater flows into the by-pass chamber via the
    stormwater drainage-pipe, where low flows are diverted        Figure 2 – HumeCeptor® system operation during high
    into the treatment chamber by the weir and drop pipe                     flow conditions

    arrangement.


    Note, the treatment chamber is always full of water
    so water will flow up through the outlet decant pipe
    (based on the head of water behind the inlet weir) to be
    discharged back into the by-pass chamber downstream of
    the weir. The downstream section of the by-pass chamber
    is connected to the outlet drainage pipe.
    Oil and other liquids with a specific gravity less than
    water rise in the treatment chamber and become trapped
    since the inlet of outlet decant pipe is submerged.




3   HumeCeptor® system