Customising Wick Trenches to Extreme Victorian Conditions Callum Morrison Benalla Rural City Council

Customising Wick Trenches to Extreme Victorian Conditions Callum Morrison Benalla Rural City Council PAGE 57

1. The Flat Country Rain Test On Dispersive Clay Dry Deep Clays with More Absorption Capacity Recent Dispersive Clays that lose structure and are almost water proof Path 1. Path 2. Path 3.

Newly installed wick trenches not yet in use !

2. Proposed Mounding in Flat Country to Test Rain Management On Dispersive Clay Dry Deep Clays with More Absorption Capacity Recent Dispersive Clays that lose structure and are almost water proof Path 1. Path 2. Path 3. Natural Ground Level

3a. Proposed Mounded Wick with Rain Diversion to Sand Infiltration Dry Deep Clays with More Absorption Capacity Recent Dispersive Clays that lose structure and are almost water proof Path 1. Path 2. Path 3. Natural Ground Level Extreme rain or extreme use peak. Washed Sand infiltration Column or Auger Holes mostly for Stormwater Slight Rise

What is the point of water and Nutrient balance calculations if the vegetation in summer is likely to die or cost too much in precious town water to sustain?

3b. Proposed Optional Manual Diversion from Summer Water Tank Overflow Trapping for Water Conservation Saving on Town Water and Surge Storm Flows Dry Deep Clays with More Absorption Capacity Recent Dispersive Clays that lose structure and are almost water proof Natural Ground Level Mounded 100mm Retention Basin To Recharge Wick & Deep (Between Trenches or across boundary between Trenches) ~ 40,000 litres with auto overflow

4. Proposed Double Wick Mounded Trenches (Reduces length and space required) Dry Deep Clays with More Absorption Capacity 100mm clay Fill So original top Soil can be lifted. Natural Ground Level 100mm Clay Fill Site topsoil reused to cover mound and excavated clays used to form up sides of mound so minimal removal costs. Tilting down the side extensions to the trench would be even more effective than a bund to stop back flow into trench and save soil. Only really centre has steep mounding so reduces imported topsoil necessity. On sides run off not as critical and must not pool. Does the geofabric have to extend under the mound causing potential sealing and blockage? Is down the trench sides and over the top of arching adequate?

These are practical and common sense additions to the conventional wick trench model however they will need to be properly tested and electronically monitored on a few test installations first to fine tune the performance and minimise costs. This will also assist with how to approach repair of old systems.

5. Blocked old trench systems (Side walls blocked and addition of pump needed to obtain elevation and expansion) Dry Deep Clays with More Absorption Capacity

Original Natural Ground Level Dry Deep Clays with More Absorption Capacity 6. Proposed refurbishment of old trench systems using top dress mounding and wick techniques plus sand pick up and dispersal auger holes or narrow washed sand trench.

Please advise if there is EPA support for this proposal. Benalla Rural City Council has just been presented with a Land Capability Assessment for an ecological Convention Centre with peak flows of 3000 litres a day and 300 mitres of Wick trench in some very difficult clay soils on public land with big buffer distances. This could be an ideal test site for trying some of these variations in very uniformly bad soils that should provide good comparisons and low risk test conditions.