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BUDGET GUIDE FOR ESTIMATING AND PLANNING FOR WOVEN MESH PRODUCTS

1. Estimating and Planning for Gabion Works

The cost of gabion and mattress work will depend on the physical conditions on site. Costs will varybetween a river wall, where some underwater work may be required, and a dry land retaining wall with goodaccess. Also labour, plant hire and stone costs tend to vary with geographical location. Thefollowing rates are based on a 4 man gang assisted by a 360 o slew tracked excavator working a sevenhour day with good site access. Strict adherence to Hy-Ten Installation Guidelines is assumed.

2. Materials

a. Gabions : An up-to-date quotation should be obtained. The major differences in price will be betweengalvanised units and galvanised units with additional HDPE coating.

b. Stone : From practical experience, figures of 1.6 to 1.7 Tonnes per m 3 for gabion works and 2.0Tonnes per m 3 for mattress work will allow for slight over filling and normal wastage on site. Stoneshould be placed as close to the works as practical, double handling may have to be considered.(The grading for use in box gabions should be between 100 and 150mm, and between 75 and150mm for Reno Mattress units).

3. Site Preparation

Excavation and grading of the ground cannot be determined here and should be assessed on site andaccording to site conditions.

4. Mechanical Plant

Use a loading shovel on structures not exceeding 2m in height with free access along the whole length.Use 360 o excavator similar to a 15-18 Ton Kamatsu/Hitachi on high structures where access is restricted.

N.B. There are conditions where other types of machinery are required, e.g. long reach booms,cranes etc, but this is not very common.

5. Labour

3-4 men plus a machine operator are suggested as the ideal Gabion gang. For large contracts or if highproduction is required, the figures should be 8 men plus 2 machine operators. For economical working thenumber of men should match the output of the machine.

6. Production

6.1. Dry Land Gabion Retaining Walls

1. Based on a 3m high gabion retaining wall with three 1m deep courses, 2m, 1.5m and 1m widerespectively. Average production: 20-25 m 3 per day per gang.

2. Based on a 1.5m high retaining wall with two courses, each 1m wide with the second coursestepped back 0.5m. Average Production: 15-20m 3 per day per gang.

6.2. Reno Mattresses

Based upon a total square metreage of 1,000m 2 or more.

Average production: 100-150m 2 per day per gang.

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6.3. Working in Water

(i) Water less than 0.5m deep: Gabions can be placed in the normal manner with production only reduced by approximately10-15% if lacing is done above water only.

Mattresses placed in this depth can still be filled in-situ, but the men are lacing with theirhands under water and production can be slowed by 30%. This can be countered by

increasing the gang size by two men to help place empty units under water and lace up thefilled ones.

(ii) Water greater than 0.5m deepDepending on the scheme, this usually means prefilling the gabions on dry land, transportingthem to site and then lifting them by crane into position. Divers may be required to lace underwater. This is an expensive operation and very difficult to quantify, but production is unlikely toexceed 10m 3 /12m 3 per day. Tidal conditions will decrease this.Mattresses have to be laid by crane in the same manner. Again, positioning and lacing underwater by divers is expensive. Production can be estimated at 20m 2 /40m 2 per day.

7. Aesthetic AppearanceThe above figures for gabion walls assumes that all the outer vertical faces have been hand-placed orpitched to present a neat coursed finish.

8. Installation Tools , although not essential are available for hire/purchase:

Pneumatic Fixing Tool. For contracts >200m 3 of gabions a pneumatic tool produces a saving.

9. Packaging

For ease of handling and transportation the gabions are supplied folded flat and tied in compressedbundles.The maximum weight of a bundle is about 700kgs.

Gabions Standardsizes

Volume Mattresses Standardsizes

Volume

* HDPE only

2x1x1m2x1x0.5m3x1x1m3x1x0.5m1.5x1x1m2x0.5x0.5*

2m 3 1m 3 3m 3 1.5m 3 1.5m 3 0.5m 3

6x2x0.170m6x2x0.230m6x2x0.300m3x2c0.170m3x2x0.230m3x2x0.300m

2.04m 3 2.76m 3 3.60m 3 1.02m 3 1.38m 3 1.80m 3

ALL IN COST OF GABION WORK

The question is invariably asked Please can you give us an all in budget price cost per m 3 for gabion work?Hopefully the following examples will assist in Planning and Estimating for gabion works:-

EXAMPLE 1: The following assumptions are made:

(i) The gabions shall be the HDPE coated type generally in accordance with the 1987 Department of TransportSpecification.(ii) The cost of stone delivered to the working area is 12.50 per Tonne.(iii) A360o excavator including driver will cost 1,000 per week to hire.(iv) Labour will cost on average 65.00 per man day.(v) The whole gang will produce on average 20m 3 of finished gabion work per day.

GABIONS Cost Per m 3 1a 2m x 1m x 1m HDPE coated gabions complete with tying wire @ 41.50 each (2m 3) 20.75 20.75

STONE 1b 1.6 Tonnes per m 3 @ 12.50 per Tonne 20.00MECHANICAL PLANT

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1c. Typical 15-18 Tonne Kamatsu/Hitachi plus driver @ 200.00 per day with output of 20m 3 per day10.00

LABOUR 1d. 3 men @ 65.00 per day total 195.00 with output of 20m 3 per day 9.75

Basic cost per m 3 60.50Add say 15% for Contractors OH & P

TOTAL per m 3 69.58 EXAMPLE 2MATTRESSES Cost Per m 2 2a 3mx2x0.3m deep HDPE coated mattresses complete with tying wire @ 55 each (12m 2) 9.16m2

STONE 2b 2.0 Tonnes per m 2 @ 12.50 per Tonne (6x2x0.170 = 2.04m 2) (2.04x2.0x12.50) 12 4.25

MECHANICAL PLANT 2c. Typical 15-18 Tonne Kamatsu/Hitachi plus driver @ 200.00 per day with output of 100m 2 per day 2.00LABOUR2d. 3 men @ 65.00 per day total 195.00 with output of 100m 3 per day 1.95

Basic cost per m 2 18.03Add say 15% for Contractors OH & P

All information is given in good faith but without warranty!