River Boyne Water Quality Management Plan - EPA

River Boync Water Quality Managrmcnt PlanCriteria for combined sewer overflows have been evolved by the Department of the Environmentwhich are regarded as complying with the Urban Wastewater Treatment Directive. These criteriainclude the following:-* A minimum overflow seming below which overflows will not occur. This is normallyexpressed as a multiple of the dry weatherflow (DWF) ond is typically in the order of 6-7.Where high strength indzrstriol eflzrents are discharged to the sewer system, the settingswould require to be adjusted accordinglyThe type of storm overflow structure should be such as to ensure eflcient hydraulic controland solids separation. Guidelines for such structures are contained in the WRC Guideline3(UK), ref: ER 304 EThe locations of overflow discharge points should be discreetly located and should haveeflective control offloating debris to avoid aesthetic nuisanceA dilution standardshould be applied which will ensure a maximzrm BOD lir~iif in the river of2Omg/l and ideally IOmg/l. The use of storage and recycli~tg can be used to control spillfrequency and this is particularly appropriate for bathing ~ecreotionol use waters (4, 8 or16 times per year)Consideration should be given topreventing 03 1 spills during 'yrst flush " conditions.This is usually achieved by ensuring that ov&d .... .. ill izof occur withinq\ ,-"the time ofco17centration of the sewer n~&@. During the early period of the storm, sewagestrengths can increase considerably q$@iment and slbne is re-suspended into the flow.Afrerwards, the cortcentrations teIid;l'-&all considernblyC.' ,i:.a\.LSignifcant overflows in the cat!&& should be nronitored tuing alrtotnaric recordingequipment to nieasure spill&$uency and duration and with provision for automaticc'-sampli~igFor inspection purposes only.Consent of copyright owner required for any other use.The foregoing criteria are applied to overflows from combined or partially combined sewer systemsand to similar overflows from pumping stations and at the inlet to treatment plants. Separate stormdrainage systems can also be contaminated to a significant extent due to organic material washed intothe sewers and mis-connections, particularly from dishwasher and washing machine discharges.These issues require policing to ensure that they are satisfactory.Storm drainage systems for petrol stations and other areas where oil spillages are likely, shouldalways be fitted with oil traps. In sensitive receiving waters, provision of oil and grit traps might alsobe considered on the outlets from road drainage systems, etc.EPA Export 26-07-2013:17:27:00