How To Improve Site Yield Through Better Storm Water, Sewer And Water Design

By Matthew Hill
Manager Urban Development, National Group Leader – Water & Environment, Calibre Consulting
matthew.hill@calibreconsulting.co

Master planned developments over large site areas always involve complex access, flooding, storm water, sewerage and water investigations. Often however, developers find themselves either paying more or getting less yield than is possible, simply because their consultants haven’t critically examined a range of pragmatic options and built these into innovative engineering solutions.

If they did, they may find that there is an unrealised potential for additional development density, which for developers equals better yield, hopefully improved margin and reduced risk.

Challenging whether an increase in density is possible through a redesign of civil engineering involves a multitude of considerations but the most obvious include things like:• Have the assumptions above the number of equivalent persons (‘EPs’) been reviewed, based on trunk network master plans?
• Could a reduced number of assumed EPs external to the site be justified?
• Would a reduced EP measure lead to reduced requirements for water reticulation networks and what are the savings that are possible by aiming for this?
• Have Priority Infrastructure Plans (PIPs) been updated, that can increase your yield?
• If so, would submitting a revised an updated Networks Master Plan be beneficial?
• Can you obtain increased capacities from existing pump stations and rising mains? If so, what savings are realistically possible and is it worth submitting an updated Networks Master Plan on this basis?
• Is there the potential to use more efficient storm water quality devices? Are proprietary products available to the same or superior standard at lower cost and can these be recommended as suitable to the relevant authority?
• Will the development benefit from an updated storm water modelling plan like MUSIC? (Model for Urban Stormwater Improvement Conceptualisation).

These are just some of the more obvious questions we ask of the assumptions made in master planned projects. In one recent example, we achieved a 12% increase in density on a 1500 lot subdivision, which translated directly into additional project yield for no extra cost. In other instances, we have saved clients from tens of thousands to hundreds of thousands of dollars on their projects, by reducing the ‘sunk’ costs of water and sewerage infrastructure through better engineered designs.

Developers can’t be expected to know the finer details of civil engineering design but they can nonetheless insist that their consultants are exploring all avenues to contain costs, especially when additional costs are often not necessary to meet regulatory standards.