Chapter 9: Road drainage and the water environment

M1 JUNCTION 19 IMPROVEMENT
ENVIRONMENTAL STATEMENT VOLUME 2
CHAPTER 9 – ROAD DRAINAGE AND THE WATER ENVIRONMENT
Table 9.2: Criteria for Determining Magnitude of Impact
(Based on DMRB, Volume 11, section 3, Part 10, table 5.4) 2
Magnitude Criteria Example
Major
Adverse
Loss of attribute and/or quality
and integrity of attribute
High risk of surface water pollution and potential
failure of total zinc and dissolved copper,
extensive change to a fishery or nature
conservation site, loss of an aquifer or high risk of
groundwater pollution, 100mm increase in flood
Moderate
Adverse
Minor
Adverse
Negligible
Minor
Beneficial
Moderate
Beneficial
Major
Beneficial
Effect on integrity of attribute
or loss of part of attribute
Measurable change in
attribute’s quality or integrity
Effects of insufficient
magnitude to affect the
attribute’s use or integrity
Some beneficial effect or
reduced risk of negative effect
Moderate improvement to
attribute quality
Major improvement to attribute
quality
peak level (1% annual probability)
High risk of surface water pollution and potential
failure of either total zinc or dissolved copper,
partial loss in productivity of a fishery, partial loss
or change to an aquifer, medium risk of
groundwater pollution, greater than 50mm
increase in flood peak level (1% annual
probability)
High risk of surface water pollution but no change
in total zinc and dissolved copper, low risk of
pollution to groundwater, greater than 10mm
increase in flood peak level (1% annual
probability)
Unlikely to affect the integrity of the water
environment
Table 9.3 Criteria for Estimating the Significance of Potential Effects
(Based on DMRB Volume 11, section 3, Part 10, table 5.5) 2
Reduction in spillage risk by 50% or more (where
existing risk is less than 1% per annum), greater
than 10mm reduction in flood peak level (1%
annual probability)
Reduction in spillage risk by 50% or more (where
existing risk is greater than 1% per annum),
greater than 50mm reduction in flood peak level
(1% annual probability)
Removal of existing polluting discharge or of
existing potential polluting discharge, recharge of
an aquifer, greater than 100mm reduction in flood
peak level (1% annual probability)
Criteria for Estimating the Significance of Potential Effects
Magnitude of Importance
potential impact Very High High Medium Low
Major VERY LARGE LARGE / VERY
LARGE
LARGE SLIGHT /
MODERATE
Moderate
LARGE / VERY MODERATE / MODERATE SLIGHT
LARGE LARGE
Minor MODERATE / SLIGHT / SLIGHT NEUTRAL
LARGE MODERATE
Negligible NEUTRAL NEUTRAL NEUTRAL NEUTRAL
B0531000_ID_70-EIA Vol 2 Chap 9 Road Drainage and the Water Environment Final Rev 4.doc Page 6