CIE4491 TU Noord

8/2/2019 CIE4491 TU Noord

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Dr.Ir.J.A.E.

ten

Veldhuis

CIE4491 Fundamentals of Urban Drainage

Design Assignment

TU Noord

February 2012


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Table of Contents

1. The Assignment 41.1. Introduction 41.2. Design requirements 41.3. Preliminary design 41.4. Detailed design 41.5. SOBEK model calculations 51.6. Evaluation of design calculations rational method versus Sobek model calculations 51.6. Final report 5

2. Project Description 72.1 Project Area 72.2 Catchment area and characteristics 82.3 Surface Water 82.4 Ground levels and ground water levels 8

2.5 Pumping station 92.6 Drinking water consumption 92.7 Rainfall data 92.8 Specicdesignrequirements 9 2.9 Additionalspecicdesignrequirements 9

3. Calculations 103.1. Wastewaterproduction(dryweatherow) 10 3.2. Stormwater discharge 103.3. The catchment areas 123.4. Hydraulic calculations 133.5. Designoftheoverowconstruction 14 3.6. Water quality aspects 15

3.7. Cost calculations 15

4. Layout and Design 164.1. The preliminary layout 164.2. Dimensioning of the sewer sections 164.3. Final layout 17

5. Milestones, Objectives and Deliverable Items 195.1. Set-upofgroupassignmentproject(SU) 19 5.2. BaselineReview(BR) 19 5.3. Preliminarydesignreview(PDR) 19 5.4. Finalreview(FR) 19 5.5. Finalpresentation(FP)20

Appendix 21


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CIE4491Fundamentals of Urban Drainage

Design Assignment

Responsible chair: Urban Drainage

Principal tutor: Dr.Ir. J.A.E ten Veldhuis E-Mail: [email protected]: HG 4.65

Case: TU Noord

Design objective: Ensuring a proper urban drainage situation in a new or redevelopmentareabydesigning anefcient and robustsystem for collection and transport of wastewater and stor-mwater and for control of groundwater levels, taking intoaccount environmental, social and economic requirements.

Learning objectives: Aftersuccessfulnishingofthedesignassignmentthestu-dent should be able to:

- apply acquired knowledge and skills to make a prelimi-nary design of an urban drainage system for a new de-velopment area as well as for an existing urban area thatis to be redeveloped;

- know what data are needed for urban drainage system

design, how these data can be obtained, and what datasources can be consulted;

- write a comprehensible report about the design processthatexplainsthechoicesmade,clariesdesigncalcula-tionsandpresentsthenaloutcomes.


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1. The Assignment

1.1. Introduction

This design assignment is an integral part of the lecture series on the Fundamentals of Urban Drainage(CIE4491)whichaimsatprovidingthestudentwiththenecessarytheoreticalbackgroundtodesignanurban drainage system for the collection and transport of wastewater and rainwater in a new develop-ment or a redevelopment area, taking into account environmental, social and economic requirements.

For this assignment, three real cases in and around Delft have been selected: the Westerkwartier resi-dential area, the Poptahof commercial centre and surrounding redevelopment area, and the TU-Noordresidential area. This allows the students to go out and get an impression of the situation on site.

The design assignment is conceived for groups of 3 students and the workload is an estimated 56 hours(2ECTS)perstudent.Thedesignprocessfollowsfourbasicsteps:

- preparation of a detailed list of design requirements for the urban drainage system;

- preliminary design of three system alternatives: draft layouts and calculation of design parameters;

- detaileddesignofthreesystemalternatives:nallayoutanddetaileddesignofmainstormwatertransport line;

- evaluation and discussion of the three system alternatives.

1.2. Design requirements

A detailed list of design requirements must be prepared that will serve as a starting point for the designof the new urban drainage system. Design requirements and criteria stated in this manual should betakenintoconsiderationandchoicesinthedesignshouldbejustiedinthedesignreport.Furthermore,additionalbasicdatarequiredforthedesignmaybecollectedintheeldortakenfromtextbooks.

Therequiredreturnperiodforoodingistobedecideduponbytheteam;thechosenreturnperiodmustbemotivatedinthenaldesignreport.

1.3. Preliminary design

Every group designs three alternatives for the given design situation, one of which must be a combinedsewer system and one should be a sustainable system, taking into account aspects such as restorationofnaturalwaterowsandminimumenergyconsumption.

The preliminary design includes a description of system principles and main components and a draftlay-out on the map of the case study area. The team will develop criteria for the evaluation of the

preliminary design alternatives. Each group then evaluates the pros and cons of the three alternatives;based on this evaluation one alternative is recommended. Possible evaluation criteria are: robustness(ability to cope with unpredictable circumstances, e.g. exceptionally heavy storms, wrong connections,dischargeoftoxicoraggressivesubstances),impactonsurfaceandgroundwaterquality,costsandaesthetics.

The preliminary design alternatives will be discussed with the supervisor in week 3 of the course period(seecourseschedule)

1.4. Detailed design

The group chooses a preferred alternative out of the three preliminary designs. This choice is to be moti-

vatedinthenaldesignreport.Adetaileddesign,includinghydrauliccalculations,mustbepreparedforthe chosen alternative. The design calculations are to be made based on the rational method. The areaistobesplitintoseveralsubareasforwhichtherun-offcoefcientsmustbeestimated.Thedetailed


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Design Assignment TU Noord

design must be made for one of the three alternatives. A cost calculation based on given unit pricesmust be made for the detailed design alternative.

1.5. SOBEK model calculations

Based on the detailed design, a SOBEK model is to be built for the system. A SOBEK workshop willbeorganisedinweek4ofthecourseperiod(seecourseschedule)togetacquaintedwiththemodel.Based on the SOBEK model of the design alternative, the following calculations are to be conducted:

- Rainfall input: design rainfall intensity used in rational method calculations

- Rainfallinput:designstormsT=2yrs(STNBUI08),T=5yrs(STNBUI09)andT=10yrs(STNBUI10)

- Implementatleasttwochangesinthesystemtoincreasethereturnperiodofooding(from2to5yrsor5to10yrs).

- IncasenooodingoccursforSTNBUI10inyourcurrentdesign:implementatleasttwochangestomakethedesignmoreefcientandreduceoverdimensioning(intheend,thesystemshouldbeabletocopewithSTNBUI10)

1.6. Evaluation of design calculations ration method versus Sobek model calculations

IncludeonechapterinthenaldesignreportthatdescribesassumptionsmadewithregardtoRationalmethodcalculationsandSobekmodelinput(inltration,runoffcoefcients,roughnessfactoretc.)andthat presents the results of both calculations.For the Sobek model calculations, comment on the differences between rainfall inputs, at what loca-tionsoodingoccursandwhataretheeffectsofchangestothesystemtoincreasethereturnperiodofooding.

In addition, comment on the differences between results of the calculation methods, what insights canbe gained from each of the methods.The design calculations will be discussed with the supervisor in week 5 or 6 of the course period (see

courseschedule).

1.7. Final report

The end product is one combined design report per group and one presentation per group at the mini-symposium taking place at the end of the period.

Thenalreportshouldatleastincludethefollowingdeliverables:

- list of design requirements and criteria with respect to the future situation;

- motivated choice of a return period to be applied for the hydrodynamic calculations;

- calculation of design parameters that are needed for the design (wastewater production, IDF-curve,

stormwaterdischarge,catchmentareas);- draft layout of the three alternative future sewer systems on the city map including:

the location of a pumping station,

mainsewerpipesandoverowconstructions,

directionofowinthepipes,

indication of the surface areas discharging to the main sewers;

- nallayoutfordetaileddesign:

completesewersystemwithdirectionsofowinthesewers,

mainsewer(s),includingthelocationofmanholes,

catchmentareaswithrespectivesurfaceareaandtherun-offcoefcient,

length,diameterandinvertlevelofeachsectionofthemainsewer(s),- hydrauliccalculationsforthedetaileddesignanddiscussionofpossibleoodingandcapacity

problems;


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- longitudinalsectionofthemainsewer(foraseparateseweragesystem:oftherainwatersystem)(horizontalscale1:2000,verticalscale1:200),whichshouldatleastinclude:

ground level,

top and invert levels of the sewer pipes,

water gradient curve during the discharge of storm water, exact location of the manholes;

- conclusions and recommendations


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2. TU Noord

Design a new sewer system for the Rotterdamseweg Noord and the Zeehelden areas. Scattered parts ofthe sewer system in this area have been replaced in the past; these parts are to remain and are to beincorporated in the design of the new system.

2.1. Project Area

Theprojectareahasbothresidentialasnon-residentialareas(TU-buildingsandsmallindustries)andatotal surface of about 106 ha. It consists of three areas main areas, the Rotterdamseweg Noord area,the Koningsveld area and the Zeehelden area and the area between the Jaffalaan, the Julialaan and theMichiel de Ruiterweg. The Rotterdamseweg Noord area is mainly industrial and has only 29 inhabitants.The Zeehelden area and the Koningsveld area are mainly residential and have 1530 and 750 inhabitantsrespectively.

The exact project area lies in the draining area Zuidplantsoen next to the TU-Delft campus and is en-closed by the Schie on the west and north side, by the Mijnbouwplein, Michiel de Ruyterweg, Jaffalaan

andRotterdamsewegontheeastside(withalltheseroadsincludedinthearea)andtheKruithuiswegviaduct on the south side. The project area is shown in Figure 1 where the project area boundary isdrawn with a red line and the different subareas are separated with grey lines.

Figure 1: Map of the TU Noord area (Source:GoogleMaps)

Figure 2: Target water levels in the project area


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In the current situation of the Rotterdamseweg Noord area the main sewer goes from the southern partof the Rotterdamseweg trough the Cornelis Drebbelweg, the Leeghwaterstraat, the Jaffalaan and theMichiel de Ruyterweg to the pumping station Zuidplantsoen. In this situation the Cornelis Drebbelwegand the Leeghwaterstraat are still part of the general sewer system while in the future this will become

part of the TU-Delft system, the new design has to be adapted to this situation. Furthermore a newresidential area with up to 220 houses will be developed next to the Rotterdamseweg. The area southof the the Julianalaan will also be redeveloped in the future. It can be assumed that an additional 100houseswillbebuilthere.Botharedrawnasgreenareasingure1.

The sewer system in the Koningsveld area has recently been replaced and is to be remain and incorpo-ratedinthedesignofthenewsystem,youcanndthecurrentsystemintheAutocadlesewersystem -Zeehelden.dwg on Blackboard. The sewer system in the Zeehelden area does have to be renewed. Oneof the main problems in this area is the absence of surface water. Furthermore there has often beenproblems with water on the street on the Diamantpad.

In the area of the Mijnbouwplein and Michiel de Ruyterweg there will be a tramway in the future. The

sewer system should give a solution to the pollution of storm water from the tramway. In the past thisareahashadsomeproblemswithoodingafterlargerainfalleventswhichisthedirectmotivationforan investigation of the sewer system in this area. The new design should provide a solution for thisproblem.

2.2. Catchment area and characteristics

Amapwith impervioussurfacesin theTUNoordareacanbefoundon blackboard(lename:Catch-mentTUNoord.pdf).Forthenetyetdevelopedareasitcanbeassumedthat80%willbeimpervious.ThereisoneseweroverowinthecurrentsystematthePrinsBerhardlaan/JaffalaanwithitsweircrestdepthatNAP-1.04mandacrestwidthof1m.Thelocationofthisoverowisindicatedingure1with

an orange dot.

The main sewer in the Rotterdam Noord area also gets three injections from other areas at dry weatherow.TogethertheseinjectionsentertheprojectareaatthesouthendoftheRotterdamseweg,seebluearrowingure1.Theinjectionstogethermakeupfora102m3/h.

2.3. Surface Water

In this area different target water levels are maintained. In the southern part the target water level isNAP -3.02 m and close to the Jaffalaan it is NAP -2 and around the Zuidplantsoen pumping station NAP-1.49m,seegure2.TheSchiehasasurfacewaterlevelofNAP-0.43m.

2.4. Ground levels and ground water levels

The ground levels in the project area can be assumed to be at NAP+0.10 m. In this area groundwaterlevelshavebeenmonitoredondifferentplaces.GraphsshowingthegroundwateructuationscanbefoundonBlackboard.AnexampleoftheRotterdamseweg70isgiveningure3.

Figure 3: 2 years series of groundwater levels at the Rotterdamseweg 70.


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2.5. Pumping station

The combined sewer system in the project area is currently transported to the Zuidplantsoen pumpingstationwhichhasacapacityof2500m3/h.Itcanbeassumedthatthepumpingstationcapacityissuf-cientforthereceivingwaterfromthisarea.

2.6. Drinking water consumption

For the calculation of the wastewater production it can be assumed that the water consumption perinhabitant is 140 litres per day, which are consumed over a period of 10 hours. The water losses amountto 20 litres per day per inhabitant. The total industrial area along the Rotterdamseweg has an annualwater consumption of approximately 47500 m3.

2.7. Rainfall data

Precipitationdatafrom4automaticraingaugesinthevicinityisprovidedina separateleonBlack-board(knmi_rainfalldataforstations210_330_344_348).Giventhedistancebetweentheraingauges,

data from the gauges can be considered independent. Based on these rainfall data partial series canbe derived for 5, 15, 30 and 60 minute intervals by applying a peak over threshold method. The partialseriesaretobeusedtoconstructIntensityDurationFrequencycurves(IDF-curves)forreturnperiodsof 1, 2, 5 and 10 years.

The sewage system needs to be designed for a certain return period of rainfall, for example once everyyear or every two years. Corresponding rainfall intensities are to be derived from the IDF-curves.

2.8. Specic design requirements

- Theavailablestoragecapacityneedstobesufcienttostorestormwaterfromtheareaequivalentto a T=10 years storm: 36 mm.

- Flooding frequency needs to be brought down to at least once per 2 years (or lower,

- Parts of the sewer system that have been replace recently must be maintained and incorporated intothe new design

- RotterdamsewegservesasooddefencestructuretoseparatetheSchieriverfromthepolderareasto the east. This protection function is to be maintained.

- Stormwater runoff from the tramline cannot be directly discharged to surface water; it needs to un-dergo some kind of treatment

- Thesituationoftheexistingsewerwithadiameterof1000mmattheJaffalaan/Rotterdamsewegcrossing and of the pressure main from the Zuidplantsoen pumping station must be taken into ac-countinthedesignofthelongitudinalproleofthesewersystems

- Inltrationintheareaispossibleatalimitednumberoflocations,becauseofthesoilcharacteristics.Ageologicalmapisprovidedthatcanbeusedtoidentifypotentiallocationsforinltration

- There is lack of storage capacity for stormwater in the area; stormwater storage in the area needsto be maximised

2.9. Additional specic design requirements

- The group is required to qualitatively discuss the advantages and drawbacks of reusing or renewingtheexistingsewersystem(i.e.costs,dimensions,existinghouseconnections,sustainabilityetc.);

- The group is required to qualitatively discuss possible solutions for the problem of existing combinedhouse connections (for the design of separate systems, it can be assumed that all houses will haveseparatewastewaterandstormwaterconnections);

- The group is required to qualitatively discuss the potential effects of climate change on the design.


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3. Calculations

3.1. Wastewater production (dry weather ow)

The wastewater production can be calculated based on the number of inhabitants and the drinkingwaterconsumption,takingintoconsiderationwaterlossesandpossibleinltrationofgroundwater.Theurban drinking water consumption comprises both domestic and industrial usage. Water losses occurwhen drinking water does not end up in the sewage system, e.g. water used to wash cars or to waterthe garden. Leakage out of the sewage system is negligible. In sewers with an invert level below thegroundwaterlevel,inltrationofgroundwateroccurs.

Thewastewaterproductionissubjecttoasignicantdiurnalpattern,ascanbeseeninFigure4.Inorderto account for this effect, a so-called peak factor can be estimated as:

av

2.5p 1.5

Q

= + (1)

with:p = peak factorQ

av= averagedailywastewaterproductioninl/s

Qav

Figure 4: Typical diurnal pattern of wastewater production.

Alternatively, it is often assumed that the daily wastewater production takes place within ten hours ofthe day. This is equivalent to a peak factor of p = 2.4.

3.2. Stormwater discharge

Not all water is actually being discharged towards the sewage system. Stormwater that falls on perviousareas,suchaspublicgardens,privategardens,etc.,isassumedtoinltrateintotheground.Waterthatfallsonimperviousareas,suchasroofsandroads,isassumedtofullyowintothesewagesystem.Thepercentageofwaterthatowsintothesewagesystemthereforedependsuponthepercentageofimperviousareainaneighbourhood,oftenexpressedasarun-offcoefcientbetween0and1(0=100%pervious,1=100%impervious).

Rational Method

The discharge of water in a downstream section of a sewage system is the sum of discharges of all

sections situated upstream of this section. This principle of adding values is the basis of the so-calledrational method. The rational method can be used to calculate discharges in a branched sewage system.Formorecomplexsystems,computermodellingsoftwarehasbeendeveloped(e.g.Sobek,Infoworks).


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The following relation between discharge and rain intensity is assumed:

n

n m mm 1

Q i ( F )=

= (2)

with:Q

n= thedischargeinthesystematalocationwithnupstreamsectionsinl/s

i = theprecipitationintensityinl/(sha)

m= therun-offcoefcientofthecatchmentareathatdischargestowardssewersectionm

Fm

= thecatchmentarea(imperviousarea)thatdischargestowardssewersectionminha.

The rational method is based on the following assumptions:

- The rain is spread evenly over the catchment area, in other words the rain intensity is constant overthe catchment area.

- The intensity is constant for the duration of the rainfall.

- ThemaximumdischargeatarandomlocationPinthesewersystem(seeFigure5)isafunctionofthe average precipitation intensity that is associated with the time needed for a rain drop to travelfrom the furthest location in the system to location P, in combination with the time needed for a raindrop to get into the sewer system via the earth surface.

Furthest location

Figure 5: Travel route.

The above-mentioned amount of time is called concentration time (tc):

c 0 dt t t= + (3)

with:t0

= The amount of time it takes a raindrop to get into the sewer system via the surface. For thisassignment it is assumed that to = 5 minutes and remains constant.

td

= The amount of time it takes a drop of rain to travel from the furthest location in a sewer systemtothelocationunderconsideration.Thisamountdependsuponthevelocityofowinthesew-ers and therefore upon the diameters of the pipes. The rain intensity used in the calculations ofthecriticalowdependsupontheconcentrationtime.

Intensity-Duration-Frequency (IDF) Curve

For this assignment it is necessary to know the intensities which occur with a certain return period andfor a certain duration of rainfall. These intensities can be derived from the rainfall data.


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Depending on the function and development of the catchment area, a sewer system is designed foran intensity that occurs with an acceptable return period. A sewer system will never be designed for amaximum expected rainfall, mainly for reasons of cost.

The design intensities can be determined using the rain data by the following steps:

- Determine the desired return period.

- Derivetherainintensityinl/(s.ha)fordifferentrainfalldurationsanddrawagraphforintensityvs.duration.

- Using this intensity-duration-frequency curve, the corresponding design intensity for each concentra-tion time can be determined.

0

40

80

120

160

0 20 40 60 80 100 120

Regenduur, min

Neerslagintens

iteit,

l/(s.ha)

T=1 jaar T=2 jaarT=1 T=2 year

Duration of rainfall, min

Intensity,

l/(s.ha)

Figure 6: Example of two intensity-duration-frequency curves.

3.3. The catchment areas

The amount of stormwater that is discharged into the sewer system depends on the size and charac-teristicsof thecatchment.Stormwaterthatfallson perviousareaslargelyinltratesintotheground,whereasstormwaterthatfallson imperviousareas(streets,side-walks,roofs)runsoff andpredomi-nantly enters the sewer system.

For hydraulic calculations it needs to be known which part of a catchment area runs off towards whichsectionofthesewersystem.Anexampleofamethodofallocatingcatchmentareastoaspecicsewersection is shown in Figure 7.

Figure 7: One method of allocating catchment

areastospecicsewersections.


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3.4. Hydraulic calculations

Hydraulic calculations are useful to understand and evaluate the systems behaviour given the load ap-plied. In this assignment, hydraulic calculations are made for all three design alternatives.

The diameters of sewer pipes in combined sewage systems are actually based on the discharge of stormwatersinceforheavyrainfalltheamountofstormwatersignicantlyexceedsthedryweatherow.IntheNetherlandsitiscommonthatcombinedsewagesystemsandrainwatersystemscompletelyllupduringrainfall.Forthedeterminationofthepipediameters,theprinciplesofhydraulicsofowthroughcompletelyorpartiallylledpipesareused.

TheheadlossforowthroughfullpipescanbedescribedusingtheDarcy-Weisbachformula:

2L uh

D 2g = (4)

with:h= headlossinmwatercolumn = frictionfactor(dimensionless)L = length of pipe, mD = diameter of pipe, mu = velocityofow,m/sg =accelerationofgravity,m/s2

ThefrictionfactorcanbecalculatedusingtheformulaofWhite-Colebrook:

1 2.51 k 2log

3.71DRe

= +

(5)

with:Re= theReynoldsnumber=uD/ = kinematicviscosityk = wall roughness, m

Equation(5)canbeusedforanykindofpipe,thatis,forallwallroughnesses.Thersttermbetweenthe brackets relates to hydraulically smooth pipes, the second one to hydraulically rough pipes. Concretesewerpipes(k=1.5mm)canbeconsideredhydraulicallyrough,sothatthersttermcanbeneglected(themaximumerrorthatisintroducedis2.5%).

Hence, the friction factor for hydraulically rought pipes can be calculated as:

1 3.712log

k / D

=

(6)

RewritingtheformulaofDarcy-Weisbach(4)asfunctionoftheowvelocityyields:

1u 2gDI=

(7)

with:I = thehydraulicgradient=h/L


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SubstitutionofandRe=uD/yieldstheformulaforthevelocityofow:

3.71u 2 2gDI log

k / D

=

(8)

The discharge can be calculated for full pipes using:

214

Q u D= (9)

For each combination of pipe diameter Dand gradient I, the discharge Qandvelocityofowucan becalculatedusingabove-mentionedformulaeforacompletelylledpipe.

Thekinematicviscositydependsonthetemperatureandisdenedas:

6

1.5

497 10

(T 42.5)

=

+(10)

with:T = temperature in C

Based on above-mentioned formulae, pairs of values for Q and u were calculated for a water tempera-ture of 10 C and a wall roughness of 1.5 mm. These values are provided in Appendix H.

With a given discharge Q, designing comes down to determining the right diameter in combination withtherightgradient.Asarstapproachthefollowingruleisoftenused:

1i D=

(11)

with:i = slope or gradientD = pipe diameter in mm

3.5. Design of the overow construction

Anoverowconstructioncanbeimplementedasarectangularoverowweir.Forthisconstructionthefollowing formula applies:

3 / 2Q 1.86Bh= (12)

with:Q = overowingdischarge,m3/sB = width of the weir crest, mh = overowheight,m

Foralternativeformsofanoverowconstruction,pleaserefertoliteratureforthecorrectdischargeformulae.

When designing multiple overow constructions one should realise that a certain part of the totalcatchmentareadischargesthroughaparticularoverowduringrainfall.Moreover,acertainamountof

waterisbeingpumpedtowardsthewastewatertreatmentplant.Thedischargethroughtheoverowconstruction(s)isthereforethetotaldischargeminusthemaximumpumpcapacity.


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3.6. Water quality aspects

Asimpliedandqualitativeevaluationof waterqualityaspects canbemadeby accountingforthreetypes of substances, and the impact of different urban drainage systems on surface and groundwaterbodies.

Organicmatter(COD)cancauseoxygendepletioninsurfacewater.Furthermore,nutrients(nitrogenandphosphorus)andmicro-pollutants(heavymetals,polycarbons,pesticides,etc.)candeterioratewa-ter quality. Finally, bacteria present in the wastewater can be a health-risk.

Table 1: Qualitative evaluation of the impact of different sewer systems on surface and ground water bodies.

Impact on surface water Impactonsoiland/orgroundwater

COD and nutri-ent supply

Heavy metalpollution

Microbialcontamination

COD and nutri-ent supply

Heavy metalpollution

Microbialcontamination

Combined sewer system withcombinedseweroverows(dischargetosurfacewater)

low frequency,high concentrations



none none none

Separate sewer system withdischarge of rainwater to

surface water bodies

high frequency,low concentrations

high frequency,high concentrations

high frequency,low concentrations

none none none

Separate sewer system withrainwaterinltrationfacilities

none none none high frequency, lowconcentrations

high frequency, lowconcentrations

high frequency, lowconcentrations

Separate sewer system withwrong connections(dischargetosurfacewater)




none none none

Separate sewer system withwrong connections(inltrationfacilities)

none none none high frequency,high concentrations



The group is required to discuss the advantages and disadvantages of the three alternatives with re-spect to the water quality aspects listed in Table 1. In case of obvious water quality problems with aspecicalternative,possiblesolutionsshallbesuggestedandtheprosandconsofvariousoptionstoreduce emissions to surface and groundwater, such as end-of-pipe treatment (constructed wetlands,

lters)orfacilitiestoimprovewaterqualityinthesurfacewatersystem,shallbediscussed.Itmustbetakenintoaccountthatsufcientspacemustbeavailableforabove-groundfacilitiesandthatsomefacilities may have aesthetic aspects while others may cause malodour. Heavy constructions on weaksoils are especially costly because proper foundation must be provided. Finally, the problem of faultyconnections and possible solutions needs to be discussed.

3.7. Cost calculations

As a part of the assignment, you are required to make a cost calculation for each of the 3 alternativesthat you have designed. The cost calculation is to be based on the following assumptions:- main sewer line: use pipe dimensions that were calculated- all other sewers in the lay-out: assume dimension of 300mm

Once the costs of every alternative have been calculated: compare total costs per alternative and dis-cuss the differences.

NB: The preferred material, according to the requirements of Delft municipality, is PVC. Cost tables aregiven for concrete pipes, yet price differences between concrete and PVC pipes are small: therefore, inthe assignment cost tables for concrete pipes can be used for cost calculations of PVC pipes.

Appendix C of the assignment manuals provides base prices of sewer system components.


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4. Layout and Design

4.1. The preliminary layout

Wastewaterfromthedevelopmentareaneedstobetransportedtothepumpingstation(s).Fromthereit will be pumped towards a wastewater treatment plant. In this assignment all wastewater has to betransportedtowardsthepumpingstation(s)underfree-owconditions.Thisconditionalsoappliesforthe transport of storm water in a combined sewage system. All pipes, both for wastewater as well as forstorm water, need to be underground.

To be able to design the layout of a sewage system it is essential to acquire a map with contour lines.Secondly, the location to which the system needs to transport the wastewater has to be determined.For a combined sewage system or the wastewater system of a separate sewage system this could bethe wastewater treatment plant or a pumping station that will pump the water towards a wastewatertreatment plant. For a rainwater system, however, the location of an outlet to surface water needs to beselected.Foracombinedsewagesystemoneormultipleoverowconstructionswillhavetobelocated

near surface water.

For this assignment it is mandatory that the sewer system be branched.

Respecting these conditions, a draft layout can be designed using the following procedure:

- Determinethedirectionofowofstormwaterrunoffoverlandusingthecontourlines.Also,deter-minethedirectionofowinthesewerpipesusingthecontourlinesandroughlysketchtheseonthe area map.

- Considerseveraloptionsforthelayoutofthemainsewer(s).

- Choosetwoalternativesandmakeapreliminarylayoutofthemainsewer(s),afterwhichthemostimportantbranchesandnallyallsewerscanbedrawn.

- Indicatethedirectionofowinthesewerpipesonthemap.- Indicate the manholes in the main sewer pipe.

- Determine which surface areas discharge into the which sections of the main sewer.

4.2. Dimensioning of the sewer sections

After the preliminary layout of the system has been drafted, the dimensions of each section of the mainsewer pipe can be calculated starting at the location of the most upstream situated manhole. The fol-lowing steps should be taken into account:

- futuredryweatherow;

- intensity-duration-frequency curve for rainfall;

- catchment area per section, taking into account different wastewater productions per area;- run-offcoefcientsperarea;

- inltrationofgroundwater;

- availablepipediameters(seeAppendixB);

- thegroundcovershouldatleastbe1mtoprotectthesewerpipesagainsttrafcloadsandtoallowfor house connections;

- theaverageowvelocityinthepipescannotexceed3m/s;

ThehydraulictablesinAppendixFshouldbelledoutrowbyrow.Anexamplaryhydrauliccalculationfor the layout in Figure 9 can be found at the end of Appendix F for a storm water system.

The example tables include calculations of the piezometric levels at the upstream and downstream endsof pipe segments. Compare these levels with the ground level at this points and check whether manholeooding(i.e.piezometriclevelabovegroundlevel)occurs.Ifitdoes,thedesignshouldbechangedso


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thatnooodingoccurs.Thepiezometriclevelsalsoindicatewhetherapipeisfullorpartiallylled.Thecorresponding calculation formulas can be used accordingly.

4.3. Final layout

Inthenallayout,alldetailsneededforacompletedesignwillhavetobegiveninthedrawing.

These are:

- Theserialnumbersandsizesofthecatchmentareas,aswellastheirclass/zone.

- Theserialnumbersofthemanholes(onlytheonesthatareconsideredincalculations)includingtheirground level and invert level.

- The lengths and diameters of the calculated sewer sections of the main sewer.

The diameters and invert levels of the sewer sections are the result of hydraulic calculations. Figure 8shows the standard representation of above-mentioned parameters in the layout drawing.

Catchment

charateristicsManhole

charateristicsPipe

charateristics

Figure 8: Standard representation of sewer information.

An example of a layout is given in Figure 9 and an exemplary longitudinal section is shown in Figure 10.


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6,701

8,00

6,232

7,80

5,85 3

7,50

5,504

7,30

5,006

7,00

6,607

8,00

6,308

7,60

5,609

7,10

6,4010

7,80

6,0011

7,50

5,6812

7,30

5,6013

7,00

I A

1 1,48

I C

2 1,44II C

3 0,66

IIIB

4 0,52

IIIC

5 0,40

I B

6 1,85

II A

7 3,00

I A

8 2,00I A

9 2,20

II C

10 0,68

IIIB

11 1,32

IIIB

12 2,65

5

7.10

5.30

5.10

L=200

D=0.4L=200 D=0.5

L=175

D=0.3L=145

D=0.6

L=80

D=0.6

L=80D=0.8

L=60

D=1.0

L=240D=0

.5

L=240D=0.

L=160D=0.4

L=160D=0.4

L=90

L=90D=

0.6

Figure 9: Example of a layout.

Manhole number

Ground level

Invert level

Sewer gradient

Distancesectiontotal

Diameter

Figure 10: Longitudinal section of a storm water system.


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5. Milestones, Objectives and Deliverable Items

5.1. Set-up of group assignment project (SU)

Date: Week 1

- Formassignmentgroups(3students)

- Chooseassignmentproject(1outof3:Poptahof,Rotterdamseweg,Westerkwartier)

- Prepare project planning

- Understand current project area situation and future plans.

5.2. Baseline Review (BR)

Date: Week 2

- Compile design requirements and design choices. Motivate where applicable.

- Choosereturnperiodforooding- Collect data for basic calculations: run-off areas, runoff generation, domestic wastewater production,

industrialwastewaterproduction,groundwaterinow,etc.

Deliverable items:

- List with design requirements.

- Area characteristics: population, land use, allotment, wastewater production, stormwater inow,groundwaterinow,etc.

- Choose three system alternatives

5.3. Preliminary design review (PDR)

Date: Week 3-4

- Preliminary design of three alternatives: type of system, system layout etc.

- Select stormwater and wastewater collection system principles (pipes/inltration zones/storages/greenroofs/etc.)

- Make basic calculations required for the preliminary design: run-off areas, runoff generation, waste-waterproduction,groundwaterinow,connectionsofareastosystemelements,etc.

Assignment meeting 1 with lecturer

- Discuss preliminary design alternatives and selection for detailed design

5.4. Final review (FR)

Date: Week 4-6

- Detailed design of the selected urban drainage system: horizontal alignment, type of system, loca-tion of manholes, etc.

- Hydraulic calculations: expected discharge per pipe section, dimensions and gradients of the pipesections etc.

- Checkthatnooodingoccurs.

Assingment meeting 2:

- discussdesigncalculationsnaldesign


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5.5. Final presentation (FP)

Date: Week 7-8

- Prepare a brief and concise overview of the project, the work done and the results obtained.

Deliverable items:

- Finalpresentation(28March2012)

- Finaldesignreport(deadline5april2012)


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Appendix A. Demands of the future network manager

A.1. General requirements

- Minimal diameter of 315 mm for non-pressurised pipes.

- Minimal diameter of 63 mm for pressurised pipes.

- Note that for PVC pipes nominal diameters are external diameters. For all other pipe types nominaldiameters are internal diameters. This must be taken into account for the hydraulic calculations.

- Maximumowvelocityinpressurisedpipesof2.0m/s.

- Maximumllingofnon-pressurisedpipesof50%.

- Pipe material: PVC.

- Minimal cover of the pipes of 1.00 m for residential streets.

- Minimal cover of the pipes of 1.60 m for main streets.

- Maximal length of pipe section between manholes of 70 m.- Restrictednumberofdifferentpipetypes/diameters.

- Thereturnperiodforoodingshouldbechosenatanacceptablelevel:pleasemotivateyourchoice.

- A reservation should be made for a future installation of a rainwater treatment facility.

- If possible, rain water pipes must be located above waste water pipes.

- No height jumps in the sewer system.

- Minimalgradientof1:250intherstsectionandof1:500inallothersections.

- Sewers that are constructed on piles must be made from reinforced concrete. PVC is not allowed.

A.2. Intersection of wastewater and stormwater pipes

For the intersection of wastewater and stormwater pipes there are two possible design options:

- The rainwater pipe is conducted via an inverted siphon below the wastewater pipe;

- Thewastewater pipecrosses a manhole in the rainwatercollection system: rainwater is owingthrough the manhole whereas the wastewater pipe crosses the manhole.

A.3. Intersection of water collection pipes and surface water bodies

For the intersection of waste- or stormwater pipes with ditches there are two possible design options:

- The whole waste- or storm water collection system is located at least one metre below the groundof the surface water body;

- An inverted siphon is used locally at the intersection with the ditch.

N.B.: In the municipality of Delft there are about 100 inverted siphons in the wastewater collectionsystem and about 200 to 300 inverted siphons in the separate stormwater collection systems.Inverted siphons and pipes crossing manholes, however, are prone to blockage and accumulationof debris.

A.4. Ground water leakage

The pipes in the municipality of Delft are for the most part located below the groundwater table. As aconsequence,thedryweatherowcanconsistofupto50%groundwater.Thisfactmustbetakenintoaccountwhendesigningthewastewatercollectionsystem.Asaroughestimate,groundwaterinltra -tion in this assignment can be assumed to amount to approximately 0.3 litre per second per hectare.


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A.5. Connection of pressurised and non-pressurised pipes

The most important requirement in relation to the connection of a pressurised main to a gravity sewermain is that the pressurised main should always release its discharge under water to avoid odour nui-sance. Wastewater from pressurised mains suffers from oxygen depletion, especially for longer mains.

As a result, hydrogen sulphide and methane gases are formed. These gases are released as the waterenters from the pressurised main into a gravity sewer. Discharging water from the pressurised mainunder water prevents most of the gas from rising to the urban surface, where they would cause odournuisance.

Thisrequirementcanbefullledbyconnectingthepressurisedmaintoamanholethatisalwayslledwith water. This is realised by placing weir in the manhole where it connects to the gravity sewer.


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Appendix B. Cost Estimation of Sewer Pipes

B.1. Cost estimation for the construction of new sewer pipes including manholes

Assumptions

Base price 300 mm sewer pipe 130 /mpipe

Base price 700 mm sewer pipe 470 /mpipe

Base price manhole 800 x 800 mm 1,940 /unit

1 manhole per 40 meter

Base price house connection 230 /unit

1 house connection per 10 meter

Base price rainwater inlet and connection 300 /unit

1 rainwater inlet and connection per 10 meter

pipediameter

pipe costs manholedimensions

manholecosts

manholecosts

houseconnection

rainwaterinlet costs

total costs

[mm] [/m] [mm x mm] [/unit] [/mpipe] [/mpipe] [/mpipe] [/mpipe]

200 100 600 x 600 1,540 39 23 30 190

300 130 800 x 800 1,940 49 23 30 230

400 160 1000 x 1000 2,440 61 23 30 270

500 200 1000 x 1000 3,080 77 23 30 330

600 250 1250 x 1250 3,880 97 23 30 400

700 470 1250 x 1250 4,890 122 23 30 650

800 540 1250 x 1250 6,160 154 23 30 750900 610 1500 x 1500 7,750 194 23 30 860

1000 700 1500 x 1500 9,770 244 23 30 1,000

1250 970 1750 x 1750 17,150 429 23 30 1,450

1500 1,340 2000 x 2000 22,540 564 23 30 1,960

B.2. Cost estimation for the construction of pressurised sewer systems

Assumptions

Base price pressurised pipe

- diameter 63 mm - 100 mm 0.31 /m/mm- diameter 100 mm - 315 mm 0.51 /m/mm

B.3. Cost estimation for demolition works

Demolitionandremovalofrectangularmanholes600/800mm 88,96 permanholeDemolition and removal of rectangular manholes 1000 mm 105,37 per manholeDemolition and removal of round manholes 400-800 mm 75,77 per manholeDemolition and removal of concrete pipes 300-600 mm 15,11 per metreDemolition and removal of concrete pipes 600 - 800 mm 19,62 per metreDemolition and removal of PVC pipes 315- 400 mm 12,01 per metre


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Appendix C. Hydraulic Calculations

1

2

3

4

5

6

7

8

9

10

11

12

13

15

16

17

18

19

Sectio

n

Origin

DRYWEATHERFLOW

RAINFALLRUN

OFF

TOTALDISCH

ARGE

fromman

hole

to

m

an

hole

surface

branch

company

Catchmentarea

Domesticandindustrial

wa

stewater

Infiltration

Peak

discharge

Catchmentarea

Concentration

time

Rainintensity

Discharge

addedA

cum.

A

discharge

q

discharge

qA

cum.

qA

added

cum.

Qp8+10

runoffcoef

added

A

cum.

A

tc

i

Qr=i.A

Qp+Qr

non

o

ha

ha

l/s.ha

l/s

l/s

l/s

l/s

l/s

ha

ha

min

l/s/ha

l/s

l/s

Appendix:Hydrauliccalculation

s

combinedsewagesystem

Page1:Calculationofdischarge


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20

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23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

Section

PROPOSED

CONDUIT

HYDRAULICCONTROL

REM

ARKS

fromman

hole

toman

ho

le

Elevation

Len

gth

Slope

Size

Fullpipe

Peak

d

ryweatherflow

Partiallyfilledpipe

Piezometriclevel

Groundlevel

Invertlevel

Dis.

capacity

VelocityQ

p/Qo

Velocity

Qr/Qo

Velocity

Velocity

h

Upper

end

Lower

end

Actual

concen

tration

time

up

down

up

down

Qo

vo

non

o

mNAP

mNAP

mNAP

mNAP

m

m

l/s

m/s

%

m/s

%

m/s

m/s

m

mNAP

mNAP

min

Appendix:Hydrauliccalcu

lations

combinedsewagesyst

em

Page2:Proposedcond

uit


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1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

S

ection

Origin

DRYWEATHERFLOW

PROPOSEDCO

NDUIT

REMARKS

fro

m

ma

n

ho

le

toman

hole

Catchment

area

Domesticandindustrial

wastewater

Infiltration

Peak

discharge

Elevation

Length

Slope

Size

Fullpipe

Peakdischarge

Groundlevel

Invertlevel

surface

branch

company

addedA

cum.

A

discharge

q

discharge

qA

cum.

qA

added

cum.

Qp

8+10

up

downup

down

L

I

Cap.

Qo

VelocityQp/Qo

Velocity

no

no

ha

ha

l/s.ha

l/s

l/s

l/s

l/s

l/s

mNA

P

mNAP

mNAP

mNAP

m

m

l/s

m/s

%

m/s

Appendix:

Hydrauliccalculations

separatesewagesystem

Wastewatersystem


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1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

2

0

21

22

23

24

25

2

8

29

Section

Origin

RAINFALLRUNOFF

PROPOSEDCONDUIT

HYDRAULICCONTROL

REMARKS

fromman

hole

toman

hole

surface

branch

Catchmentarea

Concen

tration

time

Rain

intensity

Dischar

ge

Elevation

LengthSlope

Size

Fullpipe

Partiallyfilled

pipe

Piezometriclevel

Actual

con

cen

tration

tim

e

area runoff

coef.

added

cum.

tc

i

Qr

Groundlevel

Invert

level

Dis.

capac.

VelocityQr/Qo

VelocityVelocity

h

Upper

end

Lower

end

A

A

A

up

downup

down

Qo

vo

no

no

ha

ha

ha

min

l/s.ha

l/s

mNAPmNAPmNAPmNAP

m

m

l/s

m/s

%

m/s

m/s

m

mNAPmNAP

m

in

Appendix:

Hydraulicca

lculations

separatesewages

ystem

Stormw

atersystem


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Appendix D. Hydraulic Properties of Partially Filled Circu-lar Pipes

D.1. Graphical representation

Figure11showstherelationbetweenwaterdepthinthepipeandtheowvelocityandthedischarge,respectively.

H = water depthD = pipe diameterv = owvelocityinapartiallylledpipeQ = dischargeinapartiallylledpipe

Vfull

= full pipe velocityQ

full= full pipe discharge

Q/Qfull v/vfull

Figure 11:Velocityanddischargeinpartiallylledpipes.


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D.2. Characteristic values for partially lled circular pipes

Q/Qfull h/D V/Vfull R/D Q/Qfull h/D V/Vfull R/D Q/Qfull h/D V/Vfull R/D

0.001 0.023 0.17 0.0152 0.210 0.309 0.80 0.1751 0.805 0.701 1.08 0.2964

0.0020.032 0.21 0.0210

0.2200.316 0.81 0.1784 0.810 0.705 1.08 0.2969

0.003 0.038 0.24 0.0249 0.230 0.324 0.82 0.1820 0.815 0.709 1.08 0.2974

0.004 0.044 0.26 0.0287 0.240 0.331 0.83 0.1851 0.820 0.713 1.08 0.2979

0.005 0.049 0.28 0.0319 0.250 0.339 0.84 0.1887 0.825 0.717 1.08 0.2984

0.006 0.053 0.29 0.0345 0.260 0.346 0.85 0.1918 0.830 0.721 1.08 0.2989

0.007 0.057 0.30 0.0370 0.270 0.353 0.86 0.1948 0.835 0.725 1.08 0.2993

0.008 0.061 0.32 0.0395 0.280 0.360 0.86 0.1978 0.840 0.729 1.07 0.2997

0.009 0.065 0.33 0.0420 0.290 0.367 0.87 0.2007 0.845 0.734 1.07 0.3002

0.010 0.068 0.34 0.0439 0.300 0.374 0.88 0.2037 0.850 0.738 1.07 0.3006

0.011 0.071 0.35 0.0458 0.310 0.381 0.89 0.2066 0.855 0.742 1.07 0.3010

0.012 0.074 0.36 0.0476 0.320 0.387 0.89 0.2090 0.860 0.747 1.07 0.3014

0.013 0.077 0.36 0.0495 0.330 0.394 0.90 0.2118 0.865 0.751 1.07 0.3018

0.014 0.080 0.37 0.0513 0.340 0.401 0.91 0.2146 0.870 0.756 1.07 0.3022

0.015 0.083 0.38 0.0532 0.350 0.407 0.92 0.2170 0.875 0.761 1.07 0.3025

0.016 0.086 0.39 0.0550 0.360 0.414 0.92 0.2197 0.880 0.766 1.07 0.3028

0.017 0.088 0.39 0.0562 0.370 0.420 0.93 0.2221 0.885 0.770 1.07 0.3031

0.018 0.091 0.40 0.0581 0.380 0.426 0.93 0.2243 0.890 0.775 1.07 0.3033

0.019 0.093 0.41 0.0593 0.390 0.433 0.94 0.2269 0.895 0.781 1.07 0.3036

0.020 0.095 0.41 0.0605 0.400 0.439 0.95 0.2291 0.900 0.786 1.07 0.3038

0.022 0.100 0.42 0.0635 0.410 0.445 0.95 0.2313 0.905 0.791 1.07 0.3040

0.024 0.104 0.43 0.0659 0.420 0.451 0.96 0.2334 0.910 0.797 1.07 0.3041

0.026 0.108 0.45 0.0683 0.430 0.458 0.96 0.2359 0.915 0.803 1.06 0.3042

0.028 0.112 0.45 0.0707 0.440 0.464 0.97 0.2380 0.920 0.808 1.06 0.3043

0.030 0.116 0.46 0.0731 0.450 0.470 0.97 0.2401 0.925 0.814 1.06 0.3043

0.032 0.120 0.47 0.0755 0.460 0.476 0.98 0.2420 0.930 0.821 1.06 0.3043

0.034 0.123 0.48 0.0772 0.470 0.482 0.99 0.2441 0.935 0.827 1.06 0.3042

0.036 0.127 0.49 0.0796 0.480 0.488 0.99 0.2461 0.940 0.834 1.05 0.3040

0.038 0.130 0.50 0.0813 0.490 0.494 1.00 0.2481 0.945 0.841 1.05 0.3037

0.040 0.134 0.50 0.0837 0.500 0.500 1.00 0.2500 0.950 0.849 1.05 0.3033

0.045 0.141 0.52 0.0877 0.510 0.506 1.00 0.2519 0.955 0.856 1.05 0.3029

0.050 0.149 0.54 0.0923 0.520 0.512 1.01 0.2538 0.960 0.865 1.04 0.3022

0.055 0.156 0.55 0.0963 0.530 0.519 1.01 0.2559 0.965 0.874 1.04 0.3014

0.060 0.163 0.57 0.1002 0.540 0.525 1.02 0.2577 0.970 0.883 1.04 0.3004

0.065 0.170 0.58 0.1042 0.550 0.531 1.02 0.2595 0.975 0.894 1.03 0.2989

0.070 0.176 0.59 0.1075 0.560 0.537 1.02 0.2612 0.980 0.905 1.03 0.2972

0.075 0.182 0.60 0.1108 0.570 0.543 1.03 0.2629 0.985 0.919 1.02 0.2946

0.080 0.188 0.61 0.1141 0.580 0.550 1.03 0.2649 0.990 0.935 1.02 0.2908

0.085 0.194 0.62 0.1174 0.590 0.556 1.03 0.2665 0.995 0.956 1.01 0.2844

0.090 0.200 0.63 0.1206 0.600 0.562 1.04 0.2681 1.000 1.000 1.00 0.2500

0.095 0.205 0.64 0.1233 0.610 0.568 1.04 0.2697

0.100 0.211 0.65 0.1265 0.620 0.575 1.04 0.2715

0.105 0.216 0.66 0.1291 0.630 0.581 1.05 0.2731

0.110 0.221 0.67 0.1317 0.640 0.587 1.05 0.2745

0.115 0.226 0.68 0.1343 0.650 0.594 1.05 0.2762

0.120 0.231 0.69 0.1369 0.660 0.600 1.05 0.2776

0.125 0.236 0.69 0.1395 0.670 0.607 1.06 0.2793

0.130 0.241 0.70 0.1421 0.680 0.613 1.06 0.2806

0.135 0.245 0.71 0.1441 0.690 0.620 1.06 0.2821

0.140 0.250 0.72 0.1466 0.700 0.626 1.06 0.2834

0.145 0.255 0.72 0.1491 0.710 0.633 1.06 0.2848

0.150 0.259 0.73 0.1511 0.720 0.640 1.07 0.2862

0.155 0.263 0.74 0.1531 0.730 0.646 1.07 0.2874

0.160 0.268 0.74 0.1556 0.740 0.653 1.07 0.2887

0.165 0.272 0.75 0.1575 0.750 0.660 1.07 0.2900

0.170 0.276 0.76 0.1595 0.760 0.667 1.07 0.2912

0.175 0.281 0.76 0.1619 0.770 0.675 1.07 0.2925

0.180 0.285 0.77 0.1638 0.780 0.682 1.07 0.2936

0.190 0.293 0.78 0.1676 0.790 0.689 1.07 0.2947

0.200 0.301 0.79 0.1714 0.800 0.697 1.07 0.2958


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CIE4491 TU Noord

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