ILLEGAL DISCHARGES THAT IMPACT THE UK DANGEROUS SUBSTANCES AND EXPLOSIVE ATMOSPHERES REGULATIONS (DSEAR)
Ashley V. Gray, Martin V. Haddrill, MWH
(free)
MWH reviewed a cost-beneficial technical approach to minimise the risk of explosion(s)
occurring within sewerage systems for one UK Water Company. The review highlighted the
risks of explosion occurring in small pumping stations from small illegal discharges of VOCs,
like petrol. Technical methods to predict petrol vaporisation were reviewed, and one selected
to estimate conditions under which an illegal discharge could reach a small pumping station.
Assuming minimal air movements and taking account of particular factors allowed calculation
of whether or not explosive air / petrol vapour mixtures could be generated. By combining
these identified factors, a simplified DSEAR management procedure was developed. It was
utilised as a first step risk assessment in the design or refurbishment of such small pumping
stations. This approach effectively allowed the de-classifying of some small pumping stations
from Zone 2 (short period hazard) or Zone 1 (occasional explosion hazard) to an unclassified
status with commensurate savings of 10% to15% on capital costs and less onerous
maintenance requirements. However, it also allowed the identification of when potentially
hazardous situation(s) could occur under normal sewerage network operations, and thus
when explosion protection was still required.
KEY WORDS
DSEAR, illegal discharges, petrol, declassifying zoning, pumping stations
