5. Attachment D - Stormwater Response

23 September, 2016                           -2-
Our File Ref: B16239CL002
Contact: Kym Huddart



Item 5

Issue
The plans propose for the detention tank to be buried beneath the shop. It is unclear
how the tank will be able to be accessed for repair or maintenance if needed.

Information Required
Demonstrate how the detention tank will be able to be accessed for maintenance or
repair purposes.

Lambert & Rehbein Response
Access to the detention tank will be provided at the rear of the proposed buildings.
Stormwater360 were contacted to confirm the vertical clearance requirements for
access/maintenance to the cartridge filters located within the detention tank. As advised
by SW360 a minimum 2.2m vertical clearance is to be provided for maintenance
purposes such as filter cartridge replacement. Refer to Drawing B16239-CSK03 for
sections demonstrating this clearance is achieved.

Item 6

Issue
It is unclear from the provided drawings whether the Stormwater 360 will be sitting within
the detention tank, and whether submersion of the outlet will affect the performance of
the Stormwater 360.

Information Required
Demonstrate how the efficiency of the Stormwater 360 will not be inhibited by its
submersion within the detention tank.

Lambert & Rehbein Response
The StormFilter cartridges are located within the detention tank as shown on Lambert &
Rehbein’s plans B16239-CSK02. The majority of stormwater pollutants are typically in
the “first flush”. The StormFilter cartridges are located at the inlet to the detention tank
within the treatment chamber created by an internal 920mm high wall.

Incoming flows will build up behind the 920mm high inner wall, creating the necessary
head to drive the passive filtration cartridge. Treated stormwater water is discharged
from the treatment chamber to the main detention tank via pipes contained within a false
floor under the filter cartridges. Higher flows overtop this inner wall and fill the detention
storage component of the tank. The cartridges will continue to operate when the tank is
filled above the inner wall height. The cartridges also provide treatment for low flows.