06/1354 - MCU - Dwelling House & Lot Recon [As Published] · 132006.1354

Ref: 3436 D

6. ELLUENT DISPOSAL AREA DESIGN TYPE AND SIZE
From clause 4.2A7.3.2 of ASNZ1547-2000, disposal area size is
determined from the formula:
L = QADLR x W) or Area = Q/DLR

Where: L=Length in metres
We=Width in metres
Q=Daily design flow in Liday — 840L/day
DLR=Design Load Rate in mm/day — 15mm/day

Area = 840/15 = 56m

7. CONCLUSIONS

Therefore it can surmised that, conservatively, the area required for
secondary treated effluent disposal via beds on any of the proposed
subdivided residential lots, will be 56m? and that all the proposed lots
will have adequate area ta support the required size.

However it is the opinion of Bowler Geotechnical and recommended as
such, that a minimum area of 65m’ of conventional absorption bed,
disposing of secondary treated effluent, will be required for effective
effluent disposa! in all of the proposed residential lots. This area is a
conservative rounded up figure, based on the calculations detailed in
this report and Bowler Geotechnical’s experience in similar soil profiles
and conditions.

It was seen in the results that proposed Lot 8 had a significantly lower
rate of permeability than all of the other proposed residential lots. This
has no bearing on the subdivision's effluent disposal as Lot 8 shall
remain undeveloped. In observing the soil profiles from PBHA (in Lot
8), PBHB (in Lot 3) & PBHC (in Lot 1), there appeared to be no major
difference in material or any significantly shallow rock to account for
the discrepancy. There is a rock shelf that can be seen in a cutting on
the corner of Laguna St and Boreen Rd (Lot 8), but this shelf was not
encountered during drilling of PBHA.

Effluent Disposal - Pyweil