Last Thursday, the 30th of July, saw the Development Policy Advisory Committee on the Gawler East DPA hold a public hearing. To their credit they allowed everyone who nominated  in their written submission that they wanted to speak, the opportunity to make a presentation. Although the hearing was scheduled to run for two hours, it stretched on for five and a half hours. At the end of the evening everyone was satisfied they had had the opportunity to put their concerns directly to the committee.
It is hoped now that the Committee will take on boad the strong arguements that were presented, and that they will be listened to, especially by the Minister who will make the final decision .

There were over fifty presentations on the evening. One that seemed to resonate with the committee was from Mr Paul Koch. Below is the written version of that presentation.

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Response to Committee by Mr Paul Koch.

I wish to talk about water and native vegetation as it relates to the DPA . These are two areas I have a professional interest in. I have almost 30 years of study and experience in the Horticultural industry.

Water.

The DPA indicated that there is only potable water available for 600 new homes (p49)

To provide water for the other proposed homes there must be the reuse of effluent water to provide for non-potable activities ie watering outdoor landscapes etc.

Although the DPA talks about mixing storm water for increasing the volume of water it misses the point that effluent water must be mixed with fresh water to dilute salts in the water.

Using reclaimed effluent water will contain salts, in particular sodium. (p 265 Growing Media) It can cause the soil to go sodic (as sodium ions replace other ions). Sodic soils tend to waterlog, are either slippery or sticky or like concrete. They erode easy and are hard to manage. (p 48 Growing Media)
Using straight effluent water would destroy the structure and fertility (physical, chemical biological ) of the soil
There is a need to mix effluent water with fresh water. This dilutes the salts so it can be used safely

Source of fresh water.

The site is not suitable for a Aquifer Recovery System (DPA p47). It must be put on anther site if that is to be the solution. This will need to be west of Main North Road.

There has been no identification of a site were ASR can and will occur, just vague references to ongoing investigations etc.

On DPA page 47 there is a reference to using wetland basins as a possible solution to providing fresh water. This statement does not take into consideration the effects of evaporation on water surfaces. In particular evaporation rates are very high in the summer months, for example mean daily pan evaporation rates are : evaporation rates in November 6.6mm , December 7.8mm, January 8.8, February 8.2mm and March 8.2mm ( Climatology Summary for Roseworthy Agriculture College)
This is a high evaporation rate (about 1.2 metres over 5 months) and would quickly evaporate off a free standing source of water.

At the time when you need a large supply of fresh water, say from a retention dam, it’s not available.

To date there has been no solutions to the source of fresh water.

The DPA seem to want to gloss over this issue – apparently a solution will just appear when there has already been over two years of investigations.

P 50 of the DPA states that the Existing Gawler Sewer system is currently operating at or above capacity. A Waste Water Treatment Plant at Gawler is seen as a way of taking the pressure capacity.

This seems like a simple solution to providing more water and reducing the pressure on the existing sewer system

This would divert water that would normally be treated. Where? Bolivar

A problem with this solution is that in winter there will less demand for the effluent water. There is no need to add extra water to already saturated soils.

This would mean instead of diverting waste water it would be adding to the demand on the existing treatment plant. Will this just over stretch the existing sewerage treatment plant.

The DPA gives a ranges of possibilities that may be suitable to solve the problem of providing water to the development.
Many of the solutions have not be fully investigated or have qualifications such a ‘possible’ or ‘may’.

The DPA should not be approved until the different options of obtaining fresh water to mix with mined sewer water are proven to be feasible and workable.

Hydrology of the site.

There has been not been a full hydrological study of the site. There is a section covering water movement across the site, but no details about water movement through the soil.

We do not know how water moves through the soil to feed springs and waterholes in the South Para for example.Will putting hard paving over the site reduce the amount of water naturally moving down into the local water tables ? Are we putting valuable ecological sites on the South Para at threat ? Where does the water that moves into the soil end up in a water table ?
What will be the effect on the bore fields of Bibaringa? People in this area rely on ground water for a range of activities. Are we putting these people’s supply at risk?

There have been no studies to understand this and other long term effects.

The effects of reclaimed effluent water on the site.

There have been no studies to determine how the soil on the site will react to water high in salts.

There needs to be an investigation of how the actual soil on the site will respond to reclaimed effluent water. It is a red brown earth, has a high percentage of clay, slippery when wet, cracking when dry. Detailed investigations need to be carried out on its suitability.

It is not a matter of just simply saying we have a source of water, so we can use it. Is the source of water compatible with the soil type?

As you use water for irrigation, the water pushes salts beyond the root zones. The salt accumulates at the edge of the wetting pattern. In fact you need higher water use than you would normally recommend to deal with the salt load.

You require winter rains to flush out salts. This can be a problem if the soils have gone sodic as the structure has been damaged.

Will using reclaimed effluent water adversely affect the fertility of the soil on this site?

DPA Attachment D. Objective 11- Protect the physical, chemical and biological quality of the soil.

Will the effluent salt eventually simply move into the existing water table and add to the existing salts in the system?

Is the bore field of Bibaringa at threat?

Will the salts move into the South Para and then eventually into the Gawler River affecting the Adelaide plains bore fields and horticultural production?

Without a detailed understanding of the hydrology of the site there is no way we can accurately predict what the outcomes will be.

The DPA should be halted until a detailed understanding of the hydrology of the site is understood and appreciated. We do not want to be creating an environmental disaster.

Native vegetation.
Natural resources Objective 1. Retention, protection and restoration of the natural resources and environment.

The DPA as written, would make it impossible to achieve this objective.

The DPA is looking to have very small allotments, down to 200 square metres or less with very small personal open space.

The offset is providing open space.

The area has previously been used for agriculture. There is some remaining native vegetation.

Page 43 figure 19 highlights areas of biological significance.

From the reading of the DPA it seems that these sites will not be protected but used as part of open space. Areas of biological significance must be protected ie not used for passive or active recreation.

Even simply walking on a site can damage fragile plants, compact the soil etc. The only real way of enhancing native vegetation, especially grasslands is to have a conservation zone around them and control weeds etc. By doing this the grassland will regenerate and be enhanced.

My fear is that land that cannot be developed and has remnant vegetation on it will be designated as open space. With the large number of people,  the pressure will be too great and the vegetation will simply be lost.

By using native vegetation as open space, this object of enhancing native vegetation is not achievable.

People should be aware that to recreate a piece of native vegetation with the suite of plants and animals that occur naturally, can take a minimum of 100 years to achieve, if ever!

The DPA should exclude all identified native vegetation as open space. It would need to be placed in a ‘conservation’ zone. A buffer zone should then be established to limit the ‘edge effect’ on it and then open space should begin.

This would be a way of achieving the stated objective.

The DPA should not be approved until there is strong protection (conservation zone) put in place for the native vegetation on the site.

Summary.

Overall I found the DPA to be written with a bias towards a developer. Serious issues were simply brushed aside with the vague impression that a solution will be found and things roll along.

I believe that solution for these issues should have been found well before the DPA had even been written.

We are required to have a leap of faith that the problems we have all identified will simply evaporate and there will be no negative outcomes.

People are not against development, they are against development that is in the wrong place, too big (with all the consequences) and not thought out.

This DPA should not be approved.
Paul Koch 30 July 2009.