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103
Environmental Health
Details of the special investigation of the discharge into the River Colne from the surface water
sewer serving the southern portion of Uxbridge Industrial Estate are set out below.
It is proposed to make similar investigations into the discharges into rivers from other industrial
areas in the near future.
Uxbridge Industrial Estate
The cause of oil pollution occurring on the River Colne at the outfall of the twin 24 inch surface
water sewer serving the southern portion of the Uxbridge Industrial Estate was investigated during
1969. The sewer was a private sewer.
The pollution was more severe than from other similar estates and the Council were requested
to prevent the pollution preferably by the provision of an oil interceptor. It was not possible to agree
without investigation for the following reasons:—
(i) there was no apparent cause for the pollution being more severe than from other estates.
(ii) the design of an oil interceptor is based on the estimated amount of water to flow through
it in a given time and to cope with winter rainfall the construction costs for this outfall
would be high.
(iii) the amount of oil pollution does not affect the construction costs but does control the
frequency with which the interceptor must be cleaned.
(iv) an oil interceptor is designed to retain, by checking the flow, matters which have a different
specific gravity to water and which will settle by floating or sinking but it will not retain
chemicals which are in solution in the water.
(v) an interceptor could not cope with oil from a major accident, e.g. a burst storage tank.
(vi) the provision of such an oil interceptor would create a precedent.
There was no obvious source of pollution and swabs were placed in the sewer to isolate sections
of it, but the pollution could not be localised. It was necessary to visit every factory to trace the soil
and surface water drainage and inspect any oil and chemicals stored on the premises. Numerous
unsatisfactory conditions were noted and notices were served, to rectify cross connections between
the foul and surface water systems; to provide bund (retaining) walling around oil storage areas and
around waste materials contaminated by oil, such as metal swarf at engineering factories. At certain
high risk premises known to have previously caused pollution the management was requested to
provide an oil interceptor before discharging into the sewer. Co-operation from the occupiers of the
factories was good and there was an enormous improvement but oil was still being discharged into
the river. Swabs were placed in every individual connection into the sewer. The swabs were checked
weekly and any pollution traced to source and remedial action taken.
AGRICULTURAL (SAFETY, HEALTH AND WELFARE PROVISIONS) ACT, 1956
There are 76 Agricultural holdings within the Borough. These vary from small holdings to
medium sized farms. All were inspected in 1969 and generally the sanitary accommodation was
satisfactory but it was necessary to serve notices in three instances.
FACTORIES ACT, 1961
There are 899 factories within the Borough and 585 inspections were made during the year.
Forty-six notices were served drawing attention to contraventions.
Details of the inspections made and the defects found are set out on page 104.