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POLLUTION PREVENTION GUIDELINES

DEWATERING OF UNDERGROUND DUCTS AND CHAMBERS :PPG20


These notes are for guidance only and aim to assist those engaged in the dewatering of underground ducts and inspection chambers. They have been produced by the Environment Agency in England and Wales, the Scottish Environment Protection Agency and the Environment and Heritage Service in Northern Ireland, referred to jointly as the Agency or Agencies. By following this advice, it should be possible to avoid causing pollution. In some instances, however, it may still be necessary to contact the Agency for further advice.

Contact details will be found at the end of these guidelines.

1. GENERAL
The Agencies are responsible for the protection of "controlled waters" from pollution and it is an offence to cause such a pollution, either deliberately or accidentally. "Controlled waters" includes all watercourses, lakes, lochs, coastal waters and water contained in underground strata (groundwater). The formal consent of the Agency is required for many discharges to controlled waters, including both direct discharges to watercourses and  discharges to soakaways. Such consents are granted subject to conditions and are not granted automatically. In the case of underground ducts and chambers, it is generally considered to be impractical to issue a formal consent for dewatering discharges of volume less than 5m 3 , although the Agency reserves the right to do so.

Operators may also be subject to control under waste management regulations. Please also note that dewatering to the foul sewer or to surface water drains requires the prior approval of the local sewerage undertaker or its sewerage agent.

2. INTRODUCTION
It is often necessary for utility companies and their contractors to dewater underground ducts or chambers. Such discharges tend to be of low volume (less than 5m 3 ) and they occur widely. Unfortunately, water that has accumulated within a duct or chamber may be contaminated with substances such as oil, silt and dissolved chemicals, all of which can adversely affect water quality. In order to protect our rivers and groundwater, it is therefore essential to exercise care when pumping out.

3. AVOIDING POLLUTION
a. By design
Ducts and chambers should ideally be designed and constructed so that they are resistant to the ingress of water, thus reducing the need to pump them out periodically. The introduction of a slope to one end and a sump in the construction of chambers will facilitate de-watering.

b. By pumping to foul sewer
Whenever practicable, the operator should dewater the duct or chamber to the foul sewer (subject to the approval of the sewerage undertaker or its sewerage agent) or to a licenced waste disposal site or treatment facility.

c. By controlling quality
If discharge to the foul sewer is not an option, the responsibility lies with the operator to check the quality of the water. If there are any doubts about the quality of the water, it should be contained and removed to a licenced waste disposal site or treatment facility by a licenced waste disposal contractor. Discharging from the duct or chamber to a surface water drain or directly to controlled waters may only proceed subject to the following:

i. The clarity of the water must first be checked by carefully taking a surface sample in a transparent container. The operator should minimise disturbance of the water in the duct or chamber as this may stir up any settled silt. If the sample is obviously contaminated with silt in suspension, is unnaturally discoloured or has an unusual odour it should not be discharged. The water should be pumped to suitable containers, or removed by vacuum tanker, and then taken to a licenced waste disposal site.

ii. Any light contamination by oil can be removed from the surface of the water with absorbent materials. Where the water is heavily contaminated with oil, the entire contents of the duct or chamber should be pumped to suitable containers or removed by vacuum tanker and taken to a licenced waste disposal site. If a duct or chamber is susceptible to oil pollution, absorbent pillows or pads can be left in place and removed at the next visit. Pipelines carrying potentially polluting materials such as oil should be constructed of materials resistant to corrosion or should be double walled or sleeved.

iii. Dewatering should be undertaken carefully in order to minimise silt and other suspended solids in the discharge. The suction end of the pump should be positioned off the bottom of the duct or chamber, as far as possible above the interface between any settled solids and the water. Wherever possible pumped discharges should be directed across grass covered ground to reduce the suspended solids load. If there are any settled solids on the bottom of the duct or chamber, these should be removed and disposed of properly after pumping has been completed.

iv. Automatic dewatering pumps within ducts and chambers are discouraged as there will be no check on water quality prior to discharge. Similarly, ducts and chambers should not be connected into the surface water drainage system.

E M E R G E N C Y HOT L I N E
0800 80 70 60
The 24-hour emergency hotline number for reporting all environmental incidents relating to air, land and water in England, Wales, Scotland and Northern Ireland.

ENVIRONMENT & HERITAGE SERVICE SCOTTISH ENVIRONMENT PROTECTION AGENCY

REGIONAL OFFICES
ANGLIAN
Kingfisher House
Goldhay Way
Orton Goldhay
Peterborough PE2 5ZR
Tel: 01733 371 811
Fax: 01733 231 840

MIDLANDS
Sapphire East
550 Streetsbrook Road
Solihull B91 1QT
Tel: 0121 711 2324
Fax: 0121 711 5824

NORTH EAST
Rivers House
21 Park Square South
Leeds LS1 2QG
Tel: 0113 244 0191
Fax: 0113 246 1889

NORTH WEST
Richard Fairclough House
Knutsford Road
Warrington WA4 1HG
Tel: 01925 653 999
Fax: 01925 415 961

HEAD OFFICE
Erskine Court
The Castle Business Park
Stirling FK9 4TR
Tel: 01786 457 700
Fax: 01786 446 885
World Wide Web: http: // www. sepa. org. uk

NORTH REGION HQ
Graesser House
Fodderty Way
Dingwall Business Park
Dingwall IV15 9XB
Tel: 01349 862 021
Fax: 01349 863 987

WEST REGION HQ
SEPA West
5 Redwood Crescent
Peel Park
East Kilbride G74 5PP
Tel: 01355 574 200
Fax: 01355 574 688

EAST REGION HQ
Clearwater House
Heriot-Watt Research Park
Avenue North
Riccarton
Edinburgh EH14 4AP
Tel: 0131 449 7296
Fax: 0131 449 7277

Calvert House,
23 Castle Place,
Belfast
BT1 1FY
Tel: 028 9025 4868
Fax: 028 9025 4777

ENVIRONMENT AGENCY

REGIONAL OFFICES
HEAD OFFICE
Rio House, Waterside Drive, , Aztec West
Almondsbury, Bristol BS32 4UD.
Tel: 01454 624 400 Fax: 01454 624 409
World Wide Web: http: // www. environment-agency. gov. uk

SOUTHERN
Guildbourne House
Chatsworth Road
Worthing
West Sussex BN11 1LD
Tel: 01903 832 000
Fax: 01903 821 832

SOUTH WEST
Manley House
Kestrel Way
Exeter EX2 7LQ
Tel: 01392 444 000
Fax: 01392 444 238

THAMES
Kings Meadow House
Kings Meadow Road
Reading RG1 8DQ
Tel: 0118 953 5000
Fax: 0118 950 0388

WELSH
Rivers House
St Mellons Business Park
St Mellons
Cardiff CF3 0EY
Tel: 029 2077 0088
Fax: 029 2079 8555

All the Agencies' pollution prevention guidance notes are available on the web sites listed below.

Printed on Cyclus TCF Recycled Paper. HO-03/ 01-10K-C-AUDL

c. By controlling quality
If discharge to the foul sewer is not an option, the responsibility lies with the operator to
check the quality of the water. If there are any doubts about the quality of the water, it should
be contained and removed to a licenced waste disposal site or treatment facility by a licenced
waste disposal contractor. Discharging from the duct or chamber to a surface water drain or
directly to controlled waters may only proceed subject to the following:

i. The clarity of the water must first be checked by carefully taking a surface sample in a
transparent container. The operator should minimise disturbance of the water in the duct or
chamber as this may stir up any settled silt. If the sample is obviously contaminated with silt
in suspension, is unnaturally discoloured or has an unusual odour it should not be
discharged. The water should be pumped to suitable containers, or removed by vacuum
tanker, and then taken to a licenced waste disposal site.

ii. Any light contamination by oil can be removed from the surface of the water with absorbent
materials. Where the water is heavily contaminated with oil, the entire contents of the duct
or chamber should be pumped to suitable containers or removed by vacuum tanker and
taken to a licenced waste disposal site. If a duct or chamber is susceptible to oil pollution,
absorbent pillows or pads can be left in place and removed at the next visit. Pipelines
carrying potentially polluting materials such as oil should be constructed of materials
resistant to corrosion or should be double walled or sleeved.

iii. Dewatering should be undertaken carefully in order to minimise silt and other suspended
solids in the discharge. The suction end of the pump should be positioned off the bottom of
the duct or chamber, as far as possible above the interface between any settled solids and
the water. Wherever possible pumped discharges should be directed across grass covered
ground to reduce the suspended solids load. If there are any settled solids on the bottom of
the duct or chamber, these should be removed and disposed of properly after pumping has
been completed.

iv. Automatic dewatering pumps within ducts and chambers are discouraged as there will be
no check on water quality prior to discharge. Similarly, ducts and chambers should not be
connected into the surface water drainage system. 2

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