Aim: To design the stormwater drainage system for a retail building and car park.

  • VAC3041 Assignment 1 Semester One 2015
    Aim: To design the stormwater drainage system for a retail building and car park.
    Design Brief:
    The accompanying diagram shows the plan details of a proposed retail building and an adjoining paved car park to be located in Ferntree Gully (37.89°S, 145.30°E) and a profile drawing of the metal roof showing seven box gutters. Each gutter is laid on a slope of 1 in 360 and terminates in a rainwater head with a downpipe that discharges the roof runoff directly to three junction pits. The junction pits convey the roof runoff, via interconnecting pipes, to a SEP labeled Pit 4. The two SEPs labeled 4 and 5 collect surface runoff from the 6.0m wide concrete walkway and paved car park, which is completely surrounded by a concrete kerb and channel. The resulting total runoff from the site is then discharged to an existing junction pit labeled Pit 6 on an existing DN600 RC municipal council stormwater drain. Assume the time of concentration to Pit 1 is 5 minutes.
    Determine:
    1. The design flow for each box gutter and downpipe based on an ARI of 100 years.
    2. Suitable pipe sizes and grades for the car park drainage system based on an ARI of 20 years. Adopt FRC pipes (C=120) with a minimum DN of 225mm and at least 300mm cover. Aim for pipe slopes that minimise excavation where possible but ensure a minimum flow velocity of 0.8 m/s is achievable when running full on the slope adopted. Ensure a minimum pipe cover of 450mm in the road reserve and allow for 75mm obvert drops at each pit. Draw up the longitudinal sections to scale for both pipe runs as the design proceeds. Use the standard pipe sizing tabulation provided and make clear all assumptions made.

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    Page 1
    Report:
    At least the following is to be included in your group report:- Assignment Cover Sheet (signed and dated), title page, brief executive summary, table of contents with sections and page numbers, the project brief, a typical diagram or sketch showing the details of the box gutter-rainwater head-downpipe assembly, all design computations and the drawings of the work including longitudinal sections along the drainage lines from Pit 1 to Pit 6 and Pit 5 to Pit 4. Drawings should be made to scale on A4 or A3 pages and must include a title, a clear border, and have the scale(s) stated. All work is to be performed to a professional standard.
    Students to work in groups of three, share the tasks equally, thoroughly check each other’s work, and take joint responsibility for all the work submitted.
    Example of how to draw up longitudinal sections for drainage lines: (Note: Two different scales are usually adopted)
    Pit 8
    DN300 RCP @ 1 in 114 DN225 RCP @ 1 in 100
    FSL 22.410 22.410 22.620
    Cover 0.535 0.300 0.300
    Obvert 21.875 22.110 22.320
    Invert 21.575 21.885 22.095
    Length 36.0 21
    Page 2

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