UKCG Environmental Training Standard

The UKCG Environmental Training Standard  was published in July 2015, and recognises the leadership role that UK Contractors Group member companies play in driving best practice within the construction sector. It sets down the minimum training expected for individuals to undertake their roles on member’s sites to be able to demonstrate their competency through formal environmental training, including the CITB SEATS course.

This document sets down the standard of environmental training applicable to those who manage, supervise or undertake construction related activities as follows:

Site Managers (including those employed by supply chains):

  1. CITB SEATS+ Course (SEATS plus additional management modules); or
  2. A comparable external course approved by the UKCG Environmental Training Task Group; or
  3. An internally developed course that can demonstrate training outcomes comparable to 1 and 2 above.

The training must last a minimum of TWO DAYS, include a form of assessment, and a completion certificate. Refresher training must be carried out at intervals not exceeding five years.

Site Supervisors (including those employed by supply chains)

  1.  CITB SEATS Course; or
  2. A comparable external course approved by the UKCG Environmental Training Task Group; or
  3. An internally developed course that can demonstrate training outcomes comparable to 1 and 2 above.

The training must last a minimum of ONE DAY, include a form of assessment, and a completion certificate. Refresher training must be carried out at intervals not exceeding five years.

Site Operatives (including those employed by supply chains)

A relevant competency scheme card including the CITB Health Safety & Environment Test where required, and renewed as necessary.

Note – in July 2015, the UKCG and NSCC (National Specialist Contractor’s Council) merged to form Build UK. A list of the members of the new body can be found here

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Polymer flocculation

Discharging turbid water with excessive levels of suspended solids is a serious problem for construction sites, particularly if it enters stormwater drains or a natural water body as it can seriously degrade the habitat of fish and other aquatic life, or cause silting and increase flood risk. As a result, to do so is an offense under UK legislation. However, whilst coarser particles can be readily removed by filtration or sedimentation, finer particles will often remain in suspension with the slightest water movement making them very difficult to remove without treatment.

Turbidity in water is measured using a nephelometer, which passes a light beam through a sample of water, and measuring the scattering at a detector set at 90 degrees to the source, reported as “Nephelometric Turbidity Units” or NTUs.

Flocculation is the process of using chemical agents (flocculants) to bind together small soil particles into larger ones (flocs) that are heavy enough to settle to the bottom of the liquid for removal. Introduction of positively charged (cationic) polymer macromolecules into turbid water attracts the naturally negatively charged clay particles, clumping into a floc having sufficient mass to sink to the bottom of the liquid. However, although cationic flocculants are highly effective in isolated systems, their positive charges make them toxic to aquatic organisms when dissolved in water, and they should NOT be used when runoff could enter stormwater drains or open-water bodies.

Anionic polymer flocHowever, anionic polymers, which carry a negative charge (like clay particles) are not toxic, and if added to stormwater together with positive calcium ions (Ca++) to form ionic bridges, anionic polymer flocculation will take place, reducing the turbidity of the treated water without harming aquatic life. Once the flocs have formed, provided the flow rate is sufficiently low, they should settle to the bottom of the water body ready for removal.

For polymer flocculation to be effective on site, three fundamental process must take place: chemical binding, settlement, and floc removal. To bind particles, polymers can be applied directly to soil surfaces, to water flowing in a collection channel, or into a settling pond, either through impregnated jute mats, hand or mechanical spreading of dry polymers, or direct application of liquid polymers. Following treatment, the objective is then to reduce the velocity and erosive force of the water by allowing it to spread out over a relatively level area, aided by perpendicular wattles, silt fences, and impregnated jute matting. Once settled, the sediment can be removed for reuse or disposal, and the now-clear water discharged to stormwater systems or open-water bodies.

Dirtbags

Dirtbag 1There are times when you have no option but to pump out silty water, leaving you with no alternative but to treat it to remove the silt before you discharge it to a watercourse or sewer (with the relevant consents or permits, of course!). If your need is large enough, you can use settlement lagoons, or pieces of specialist plant, but sometimes what you need to do will be so minor that it doesn’t really warrant the expense and effort. Dirtbags offer a simple filtration solution that takes very little space – a large geotextile envelope that you pump the water through, leaving the suspended solids in the bag. The standard bag is 1.5m square, and according to the manufacturers, it can handle flow rates up to 4600 litres per minute. As the bags are manufactured in the UK, Dirtbags can be custom-made to suit site conditions or flow rates.

In my mind, they are a really useful primary control technique, removing the easily filtered particles, but secondary treatment (settlement, flocculation, etc) may be necessary to improve the water sufficiently to meet any suspended solids requirements of an offsite discharge consent. (The manufacturers have a separate webpage showing Dirtbags in use for primary filtration inside standard settlement tanks) They’re also really useful where you’re discharging to elsewhere on your site as part of a general silt management strategy to help you keep the discharge area clear of mud.

UtilityBagAnd if you’re in the utilities business, and you regularly face the challenge of dewatering ducts full of silty water before you can carry out your work, Dirtbags also make “Utilitybags” – a smaller sausage-shaped Dirtbag to fit over the end of the discharge hose to at least take out the larger solids before discharge to a road gully.

(To visit the Dirtbags website, click on any image)