Case Study / Industrial Estate Environmental Control: An industrial estate in the South of England circa 1980.



Problems occasionally arose from oil pollution in the effluent discharges from tenants' factory units of various types. Some occupants' operations included vehicle washing, vehicle repair and maintenance, using paint thinners, lubricating oil for oil changes etc., fuel storage, companies carrying out engineering operations which incorporate the need for cutting oils, cooling oils and lubricating oils, as well as general distribution. This is the general sort of mix one would expect to find on many industrial estates.

Drainage from all the factory units on site, feed into a stream which runs through the full length of the industrial estate, which in turn feeds into a major river. Some of the discharges into the stream contained oil and oil based products, such as those items listed above.

In endeavouring to reduce the potential threat of oil pollution reaching the main river, the stream was diverted into a very large lagoon. The intention was to allow any oil contamination to settle out and be removed at this point. It transpired that this proved to be unsuitable, for two main reasons:

  • Occasionally the lagoon dried out in the summer months and the surface oil contaminated the sludge. When the lagoon refilled some of the oils remained on the bottom, being slowly released and being discharged back into the stream in the water phase as contaminated solids.
  • The cost of removing any surface oil contamination using Gully suckers or waste oil tankers became prohibitive.

    Whilst the site was, in the main, well managed, the water authority insisted that some form of interceptor facility be installed, in order to prevent pollution of the stream and subsequently the main river.


    After making various assessments, the management company in charge of operating and developing the site chose to select the solution put forward by OPEC Ltd.

    Instead of installing costly "state of the art" interceptor tanks, the stream was excavated at a point convenient to the road system on the estate. The stream was widened and made deeper, in order to slow the speed of water flow. Two "quiet water" areas were also introduced, using standard concrete pipes installed vertically and cut to allow inflow of deflected surface water contaminants. This was done by installing OPEC Ltd's HG22 Harbourguard containment boom with end fittings to allow for rise and fall, depending on variation of water levels in the stream due to rainfall etc. A centre post was positioned in mid-stream to provide deployment location for two sections of boom.

    This was done at a fraction of the cost of a standard type interceptor system, which would have been quite large. The installation was completed in November 1980.

    During the following 12 years, up to February 1992, the OPEC mop skimmer systems, together with Harbourguard HG22 solid buoyancy chamber oil containment booms, worked extremely well to the point that the lagoon was drained down, filled in and two new factory units built which are earning considerable additional profits.
    Fig. 6 Upgraded mop skimmer and harbourgard boom in place. Subtle changes have made a big difference in efficiency.

    Due to OPEC Ltd's continuing developments, the original mop skimming equipment and Harbourguard oil containment boom were replaced with more efficient "E" Series mop skimmer systems and an upgraded version of the boom. This work was carried out in February 1992.

    The OPEC mop skimmer systems were selected mainly because they are simple and easy to install, operate, maintain, and not generally affected by floating debris.

    There are many other advantages of OPEC Ltd's mop skimmers when compared with other types of skimmers, which include the fact that OPEC Mop Skimmers:

  • Pick up very little free water even in oil film thicknesses below 5mm
  • Incorporate a special Oil/Water Separator, Oil Collection Tank avoiding the need to store unwanted free water. The small amount of free water picked up is returned immediately to the oil-contaminated area.
  • Do not need pumps, the recovered oil is normally gravity fed away.
  • Can be left running 24 hours per day, 7 days per week if required.
  • Can be left for long periods unattended

    The Harbourguard oil containment boom is well proven and over the years OPEC Ltd., have improved the quality and performance. Even so, the initial installation lasted for 12 years.

    The end fittings - the sliding fixings - of the Harbourguard boom, (see figures 8 and 9) clearly illustrate how well they perform in reducing the amount of floating oil and/or debris from flowing downstream. If figure 8 is studied closely the way in which the seal between the boom and the concrete wall is made, shows how well it performs. The fabric, attached to the extended metal arm has actually cleaned the concrete, without affecting the rise and fall of the boom.

    The general arrangement of this oil removal system is not only efficient, with low maintenance costs, but also is aesthetically acceptable.

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