08/1491 - MCU - Detached House [As Published] · 132008.1491

4 PROPOSED MANAGEMENT

41 Lime Treatment Strategy

A safety factor of two is recommended for sites regarded as sensitive to acid export. These include areas:
* within 50 metres of a drainage line, stream or other surface water
* where the watertable is within 2 metres of the surface
* where the site is below the 50 year flood line.

A safety factor of 1.8 is recommended where more than 5% of samples have a %S,,, or %S,, greater than
0.03% or TAA greater than 100 moles/ton. A safety factor of 1.6 can be used for samples with tower teveis
of acidity or potential acidity.

The treatment rate is calculated using the average of all samples with a % S,, > 0.03%. The worst case
sample must have a minimum safety factor of 1.2.

In the absence of field bulk density measurement the design in-situ bulk density is 1.65 tons/cubic metre
and the excavated (loose spread, uncompacted) soil bulk density is 1.2 tons/cubic metre.

4.2 Lime Application

It is recommended the disturbed soil is spread across fill areas in jayers with the appropriate quantity of
lime being spread across the surface. The lime is then cultivated through the layer to provide uniform
mixing. The depth of the fil! layer will be affected by compaction requirements, machinery, the physica!
condition of the soil and operator preference. The exact method of mixing is of no consequence provided
lime is mixed uniformly through the placed soil. Itis steessed care should be taken with mixing as validation
samples will subsequently be taken for chemical analysis. if the uniformity of mixing is poor the validation
tests are likely to fail.

4.3 Lime Storage

Agricultural lime and hydrated lime (builders lime, calcium hydroxide) needs to be stored on-site in a
secure manner. It is recommended the hydrated lime (normally supplied in bags) is held in a locked
shipping container or similar site building. It is recommended the agricultural lime is held in a bunded
storage area. If supplied in bulk then the lime should be covered to prevent dust becoming a nuisance.

4.4 Placement of Excavated Soil

itis preferred to retain treated soil on the development area. If off-site placement is required then the
following actions must be undertaken:

the land holder must agree in writing to accept the treated material
the land holder must be provided with copies of soil analysis reports and a written declaration of
the volume and placement location
prior to placement local authority must be provided with copies of soil analysis reports and a
written declaration of the volume and placement location. Check with the focal authority to ensure
the placement complies with any local reguiations.
transport of treated soil should be performed using covered vehicles and no drainage water must
escape onto public access areas
the following areas are regarded as having higher environmental sensitivity for treated soil
placement

* within 50 metres of a drainage line, stream or other surface water

* where the watertable is within 2 metres of the surface

* where the site is below the 50 year flood line.

oe

Should these more sensitive locations be selected for placement then it is recommended the
excavated soil be treated at the source and validation tests be proved successful prior to
placement.

45 Bunding of Excavated Soil

*

It is proposed to bund any area with untreated disturbed soil, either at the excavation site or
placement site.

. It is proposed to size the bund to retain a Q=2, 60 minute storm event plus a 200 mm
freeboard. For relatively flat areas a surrounding bund height of 500 mm is likely to be adequate.

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