Appendix B - Engineering Letter

(b) Bio basin and detention basin and overland flow path in No.14 Eagle Drive replacing the
house (refer to Plan 1403-15A).

The benefits of the local community are significant for Option B and are listed below:

e Provide a Q100 overland flow path, piped drain path and easement which the existing
catchment outside the development needs.

e Provide 845m2 of additional park which will extend from the existing park to Eagle Drive

e Allow for the existing piped drainage from the Eagle Drive sag to the existing park to be
increased in size and allow an easement for maintenance.

e Removal of the regular flooding issues associated with No.14 Eagle Drive that Council
eventually have to address.

Option A cannot provide the above benefits and so will only provide a minor reduction in flooding at
No.14 Eagle Drive which may lead to the local community believing that the development has made
the situation worse. Option A though would comply with the Planning Scheme requirements of
providing non worsening of runoff quantity and quality. Option A would also not be a forced
engineering design which would require no underground drainage for the new road up till the basin
and also require shallow box culverts under the footpath to direct runoff into the basin. This is
feasible and necessary due to the basin needing to be on the high side of the development road to
drain to Eagle Drive.

We therefore recommend to our Client and Council to attempt to find a way for Option B to be
economically viable in the form of offsetting contributions or a portion of the work being payed for
by Council or another Developer so that this option can be economically viable and so therefore the
benefits to the local community can be realized.

Yours faithfully,
Callaghan & Toth

A D Toth BE Environmental RPEQ (Env) (civil) MIEAust CPEng NPER CPESC
Director

1403 14eagledr