The procedure for submitting public questions in writing no later than 12:00 two working days before the meetingis available upon request from Democratic Services (the contact details for which appear on the front page of this agenda).
Minutes:
The following question was submitted fromRoySeabrook:
Headroomestablishedby MWHfor ThornhamWwTWfor 2009/10,was554 dwellings.Throughoutthe subsequentdecade,ithasbeenconsistentlyestimated at 1,700 dwellings,despitethe buildingofwell over1,000 dwellingsduring thisperiod. The sole exception to thiswas the AMEC report (August2018)for ChichesterDistrictCouncilgiving the headroomas zero.During thisdecade,no significantupdatesto theThornhamWwTW have been undertaken.Thedefinition of DryWeatherFlowand itsuse incalculating headroomneedsto be examined in carefuldetail.
Please askSouthernWaterto makeavailable:-
1) Both10%and20%iles of measuredflowrates forthe lastthree years.
2) DailyFlowrates forthe lastyear.
3) TheEnvironmentAgency licence certificatetogetherwith anyamendmentsrelating tothe use of20%ile of flowrates.
The following answer was provided from Southern Water:
1) Both10%and 20%iles ofmeasured flowratesfor thelastthree years.
DryWeather Flow(DWF)Datafor2018to 2020 is as follows (mcd– metrescubed per day):
|
|
Q80(20%ile)mcd |
Q90(10%ile)mcd |
|
|
|
|
|
2018 |
5680 |
5260 |
|
2019 |
5722 |
5221 |
|
2020 |
5888 |
5273 |
The currentpermitted DWF forThornhamWWTWis 6565mcd.
2) DailyFlowrates for the lastyear.
We have notprovided the dailyflowsrates for2020.As partof ourflowverification systemdailyflowdatawhichdoes notmeet validationcriteriais notsubmittedas part ofourannualreturnto the EnvironmentAgency.Our experience hasshownthere wheresuch data hasbeen madepublicallyavailablein the pastit can bemis- interpreted.
The figures above are those submittedto theEAas partofourannualreturnas requiredby the relevantconditionin the EnvironmentalPermit/ Consentfor the site.
3) The EnvironmentAgencylicence certificatetogetherwithanyamendmentsrelating to the useof 20%ileof flowrates.
A copyof theenvironmentalpermit/ consentforThornhamWWTWwas provided asan attachment.Usingthe pagenumbersas given inthe PDF viewermenu page 10 states theconsented DWFand pages14,15 and16 coverthe definitionof DWF andflowmeasurementcriteria.