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MEDICAL OFFICER'S ANNUAL REPORT SHEET 10 OF DRAFT.
The chalk from which the water is derived, underlies the London
Clay, and the gathering grounds would be the range of high ground
extending from about Beaconsfield northeasterly to Buntingford and
clearly demonstrated by the cuttings at Tring.
The only possible source of contamination would be through
"Swallow holes" which are openings found at the junction of the chalk
with other geological strata and into which streams sometimes disappear.
Such a swallow hole is found at Water End near North Mymms where
water from nearly 20 square miles of land disappears,
Frequent examinations of the water are made by the Company's
analysts so that contamination may be promptly detected.
The district has a constant and up to the present adequate
supply, but owing to the growth of the population in the Company's
area of supply the Company are seeking additional powers to increase
the sunply by fresh borings in the upper portion of the Lea Valley.
There are still too many badly situated cisterns exposed to rain
and dirt where unless the covers are kept in good repair a good water
may become polluted and Injurious to the health of the users.
Rivers and Streams.
I have already described the principal streams of the district,
they are the natural means of drainage for a considerable area outside
this district and receive the outfalls of many surface water sewers,
consequently in wet weather they are very swollen and cause temporary
flooding of the low-lying area to the north of Friern Barnet Road.
In dry summers there is very little flow and as the inhabitants cannot
be expected to differentiate between the soil and surface water drains
of their houses soap suds frequently get into the surface water sewers
with consequent temporary pollution of the brooks, Several complaints
have been received respecting the soapy condition of the brook north
of Friern Barnet Road, and. this has been more marked since the rapid
development of the North Finchley District. Your Surveyor has had
the course of the brooks properly cleaned and taken steps to prevent
the stagnation in their beds during the summer months.
Sewers & Sewage Disposal.
The district is well sewered, the sewage system being designed
by B. Latham C.E. and constructed in 1884. The main sewers follow
the lines of the valleys the connections being made by tunnelling
under the ridges. These tunnel sewers are situated below the Council's
housing site in the North Ward and from the valley near the Council
Offices into the Colney Hatch Lane. With the exception of a small
area in the Avenue District the sewage is conveyed from houses to
works by gravitation. There is a small ejector station at Ely Place
in the dip near the stream at Oakleigh Road S.
The main purification works are situated in the adjoining district
of Wood Green and originally comprised settling tanks and contact
beds with the accessory machinery for sludge pressing and pumping,
working the lime mixers and providing power for working the hydraulic
pumps at the Ely Place pumping station. The power was obtained from
two Cornish coal fired boilers working two horizontal steam engines
of the mill type, the power being conveyed from them by shafting and
belting to the pumps and lime mixers. This machinery served a useful
purpose for 40 years but owing to excessive cost in working and maintenance
and the inefficiency of the old hydraulic pumps at Ely Place
this machinery is now disused.
Since 1920 a complete new plant has been installed under the
direction of your Engineer & Surveyor. This comprises a modern
magneto fired gas engine working with town gas, the power of this
engine is conveyed by shafting and belting to the lime mixers and