HELCOM RECOMMENDATION 23/5

Superseding HELCOM Recommendations 5/1 and 17/7

Adopted 6 March 2002 having regard to Article 20, Paragraph 1 b) of the Helsinki Convention

REDUCTION OF DISCHARGES FROM URBAN AREAS BY THE PROPER MANAGEMENT OF STORM WATER SYSTEMS

THE COMMISSION,

RECALLING Paragraph 1 of Article 6 of the Convention on the Protection of the Marine Environment of the Baltic Sea Area, 1992 (Helsinki Convention), in which the Contracting Parties undertake to prevent and eliminate pollution of the Baltic Sea Area from land ‑based sources,

HAVING REGARD also to Article 3 of the Helsinki Convention, in which the Contracting Parties shall individually or jointly take all appropriate legislative, administrative or other relevant measures to prevent and abate pollution in order to promote the ecological restoration of the Baltic Sea Area,

RECALLING Article 5 of the Convention on the Protection of the Marine Environment of the Baltic Sea Area, 1992 (Helsinki Convention), in which the Contracting Parties undertake to prevent and eliminate pollution of the marine environment of the Baltic Sea caused by harmful substances,

RECALLING FURTHER that the Ministerial Declaration 1988, of the ninth meeting of the Helsinki Commission calls for a considerable reduction of land‑based pollution,

BEING MINDFUL that a considerable part of oil pollution of the marine environment is caused by oil contaminated waters discharged via storm water systems,

RECOGNIZING a need for limiting oil pollution from storm water systems applying efficient treatment of oil contaminated waters,

RECALLING ALSO HELCOM Recommendation 7/3 concerning the reduction of discharges from urban areas by the development of sewerage systems,

RECOGNIZING the need for limiting the harmful effects caused by the storm water discharges to the Baltic Sea,

RECOGNIZING ALSO the need for development of present sewerage systems,

DESIRING to limit pollution caused by unsuitable sewerage systems,

RECOMMENDS to the Governments of the Contracting Parties to the Helsinki Convention that:

A)   Reduction of discharges of urban areas by proper management of storm waters

1.   measures should be taken already at the source to prevent the deterioration of the quality of storm water (e.g. efficient dry street cleaning and reduction of lead in petrol);

2.   depending on the characteristics of the contamination of the storm water, possible means should be taken to minimize the volume of storm water entering combined and separate sewer systems (minimization of the volume, reached e.g. by local infiltration systems if allowed by geological conditions);

3.   contaminated storm water from heavily polluted industrial areas (loading, unloading, storing) should be treated separately; measures can be based on local research and consideration case by case;

4.   if a storm water in a separate sewer system district is collected from traffic and other areas where the first flush of storm water is highly polluted:

‑ flow equalization units should be provided whenever possible for the first flush of storm water; and

‑ when possible this water should be treated separately in storm water treatment facilities or in a sewage treatment plant, as appropriate;

5.   in areas with combined sewer systems, the aim should be that the overflow should not be allowed more than on the average 10 times per year or limited to 10 per cent of the total load conveyed in the sewer system (several overflow occasions during one single day are regarded as one), which aim may be reached by appropriate design of the sewerage system and by providing retention facilities ^**) ; the aim should further be to catch the first (most polluted) volume of overflow for separate treatment. In order to decrease the amount of overflowing pollutants combined sewer outflows should be equipped with appropriate treatment facilities.

^**) Experience shows that the easiest way to express pollution load caused by combined sewer overflow is to use the indirect figure of frequency, i.e. number of times per year, because thus it is not necessary to undertake the difficult task of determining the quality of the combined sewer outflow in each case.

B. Limitation of oil in storm waters

6.   oily process, cooling and other waters from production plants, service stations, mechanical workshops and other plants as well as storm waters from areas where oil is handled or stored should not without effective water pollution control measures be connected to a storm water system or discharged to the recipient;

7.   oily waters from plants and areas already connected to a storm water system should without delay be investigated and measures taken accordingly, including, for instance:

‑ collection of oily wastes at the source;

‑ collection and separate treatment of oil polluted waters;

‑ limitation of quantity of oil polluted waters discharged to storm water systems; and

‑ connection of, if necessary, pretreated waters to municipal sewers,               

RECOMMENDS that this Recommendation will be in force when adopted, with provisions A.2 - A.5  applying only to new and retrofitted sewerage systems (constructed after 1 January 1998),

RECOMMENDS ALSO that the Contracting Parties report to the Commission every three years starting in 2006 with data from 2004,

DECIDES that this Recommendation should be reconsidered in 2007.