Nandroya Planning Report

leddy sergiacomi &
associates pty. itd.
LSA Ref: 45-021

 

It is noted that an industrial peak hour demand is unlikely to coincide with a residential peak
hour demand. On the basis of the WSA Guidelines, a peak day (maximum day) demand for the
estate is calculated as follows:

10.67ha x 0.25 litres/second/ha x 3600 x 24hrs x 2 (PDF) = 460,944 litres/day

Peak Hour Demand = average hour demand on peak day x peak hour factor (PHF) =

10.67ha x 0.25 litres/second/ha x 3600 x 5 (PHF) = 96,030 litres/hour, or 26.67 litres/second.

Consideration of Council’s water supply headworks calculations indicates that Council has

assumed a demand rate of 3.6 ep/1,000m2, equating to 106,700 square metres/1,000 x 3.6 =
384.12 ep. Assuming a flow rate of 500 litres per equivalent person, this equates to a daily
demand of 192,060 litres using the rationale in Council’s PSP28. Using a coefficient of 2.25 for
calculating maximum day (refer Water Resource Commission Guidelines for Water Supply
Systems which was operational around the time the headworks policy came into effect), a flow
of 432,135 litres/day can be assumed. Peak hourly demand can be calculating by doubling the

average hour, equating to 36,011 litres/hour. This equates to a flow of around 10 litres/second.

Given the above outcomes, the flows derived from the WSA Guidelines have been considered to
be less applicable to the site than those used to calculate Council’s water supply headworks. The

WSA Guidelines are primarily used to size a water distribution system upstream of the balancing

storage. To this end, the following calculations have been adopted for determining water supply
requirements for the proposed six lot subdivision at Cooroy in accordance with Council’s policy
for water supply headworks:

Peak Daily Flow (Maximum Day) = 432,135 litres/day

Peak Hourly Demand (Max Day/12hrs) = 36,011 litres/hour

Peak Instantaneous Demand (PHD/3,600) = 10.0 litres/second

 

14 November 2005 Department of State Development, Trade and Innovation Page: 36
Planning Report