Filter Materials

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Filter Materials

When building an efficient well for groundwater monitoring or abstraction you should consider the filter material surrounding the well liner.

Filter Materials

Washed, bagged and dried filter material is available as a natural silica sand, ideal for use when building an efficient well for groundwater monitoring or abstraction. This allows largely unrestricted flows of groundwater into the well while simultaneously preventing the ingress of soil particles (other than those during the initial development phase) and supporting the water-bearing formation.

Informed judgment must be made regarding the wellscreen slot sizes, the filter material and the encountered ground conditions to obtain the correct borehole construction. Please enquire for more details.

Silica Filter Sands

These materials from non-sustainable materials are available in graded sizes as in the tables below:

Size	Weight	Part No.
0.5 - 1.0mm sand	x 25 kg	BFS51
1.0mm - 2.0mm sand	x 25 kg	BFS12
2.0mm - 4.0mm	x 25 kg	BFS24
3.0mm - 5.0mm	x 25 kg	BFS35
5-8mm Single Size	x 25 kg	BFG58

Industrial Dried Silica Sands

British Sieve No.	0.5 - 1.0 mm	1.0 - 2.0 mm	2.0 - 4.0 mm
4	-	-	100
5	-	-	99.8
6	-	-	79.3
7	-	-	24.1
8	-	98.3	3.6
10	-	78.6	1.0
12	99.8	52.3	-
14	98.7	27.0	-
16	74.5	6.0	-
18	44.8	0.2	-
22	15.2	-	-
25	4.9	-	-
30	0.6	-	-

Geotextile Filters for Wellscreens

Installation of well liners when all ground conditions are unquantified still presents problems due to fine sands and silts that may be present. There is the risk that these will migrate into the well causing it to silt up with the associated costs of redrilling.

A practical solution to this common problem is the use of geotextiles which are applied over the slotted well liner after machining into a tube. The benefits of the geotextile allow for the unexpected that can be encountered during site investigations.

The geotextiles are highly chemical resistant with a high tensile strength and a high transmissivity.

Available in a range of sizes and manufactured to fit any pipe size from 19mm to 225mm diameter.

Geotextile Filters Specifications

Trade Name	GEOWRAP	GEOSOCK
Pore Size	85	200
Weight g/m2	140	160
Thickness(mm)	0.95	1.00
CBR Test	1335	n/a
Fall Cone Test	32	n/a
Water Permeability	10	48x10
ltrs/second/m2	150	180
Specific Weight	0.90	1.30