Land Capability Assessment cost and method
What contains the price of an LCA?
As in most transactions the lowest price does not generally equate to the best quality.
The cost of the LCA should reflect the expertise of the Assessor and the time involved both onsite and in the office writing the LCA report.
How much time should an Assessor spend onsite? That depends on several things. So let’s have an overlook what an assessor should do before and during the site investigation?
Before the onsite survey the Assessor should gather as much of the available information about the site as he or she can. What are these information?
- maps (with property boundaries, contour, watercourses, nearby bores, geology etc)
- aerial photos
- rainfall and evapotranspiration data
- environmental constraints, like Special Water Supply Catchments, flood, bushfire etc.
- the Councils’s specific wastewater treatment plans or strategies
- Land Zoning and planning specifications
Having these data the onsite surveying is much easier and professional. To adequately assess a site it is necessary to have a contour map of the site as well. It can mean extra cost.
What are the methods and tests the Assessor should perform onsite?
The site investigation should start with a roaming to get familiar with the key features of the site, like:
- aspect,
- climate
- erosion and landslip,
- fill,
- flooding,
- groundwater,
- land suitability,
- landform,
- rock outcrops,
- setback distances,
- site drainage,
- stormwater run-on and run-off,
- slope,
- surface waters,
- vegetation.
Some of these information can be gathered during the desktop study but in all occasions the assessor should double check if these information are proper.
Following the roaming it is time for the soil survey. A critical element of the land capability process is to adequately characterize the soil profile in terms of its thickness, permeability (especially of the limiting layer) and ability to attenuate nutrients.
This characterization needs to be determined in detail by boreholes or excavations to a depth of 2 m (or refusal), insitu dispersion tests and insitu permeability testing of the limiting layer (except in the case of dispersive and/or swelling soils and/or if seasonal soil moistures are too high).
If the characterization is not done satisfactorily, your onsite system will be designed by guesswork.
In Victoria you are most likely to encounter a clayey soil horizon over the planned land application area.
This is the limiting layer which requires detailed characterization.
In Victoria many soils are problematic with undesirable characteristics including low permeability, dispersive clays and high swelling clays.
These undesirable soil characteristics can be ameliorated by methods including addition of gypsum and/or lime allowing your onsite system to function satisfactorily.
We recommend that you choose our highly qualified and experienced team for your land capability assessment and onsite wastewater treatment design.