Common Mistakes in Drainage

Submissions to PUB (BPU)

Muhammad Zahid

Centralised Services Department (Building Plan Unit)

2

Agenda

• To highlight commonly made mistakes in Drainage

Submissions

• To share good and bad examples so that QPs can get

their submission right at first attempt

• To recap useful online links on Drainage Submissions

3

Most Commonly made mistakes in

Drainage Submissions

1. No cover letter and wrong CORENET form

2. Wrong classification of drainage works

3. Incomplete submission

4. Submission without referencing to COP

5. Non-checking of plan before submitting

4

1. Submissions without cover letter

Types of Form/Submission Form to be Used

Application for Development Control Clearance (DC)

Application for Detailed Plan Clearance (Minor Drainage Work)

Application for Detailed Plan Clearance (Other Drainage Work)

Application for Drainage Clearance for TOP

Application for Drainage Clearance for CSC

PUB-DCCLR

PUB-DPCLR

PUB-DPCLR

PUB-DRATOP

PUB-DD-CSIDRA

1. Submissions with wrong CORENET form

**ESS-CORR form shall not be used for making new ES submission

Most Commonly Made Mistakes

5

Submission on Amendments to approved DC/DP

QP must highlight area/ scope of

changes in Cover Letter & amendments

shall be clouded on plan

6

2. WRONG CLASSIFICATION

OF DRAINAGE WORKS

7

Recap: Classification of Drainage Works

• Works Affecting Minor Drainage – for internal drainage system within development plot, within HDB estate etc.

• Works Affecting Other Drainage – see definition below

Online/ Offline Detention tank system

Flood barrier or any other alternative flood protection measures

Basement pumped drainage system

within dev. with or without linkage to

underground special facilities

Public Drains to be handed over to PUB, and all works^ affecting

public drains maintained by PUB.

^Bus shelters, covered linkways (with drain below/abutting), and

developments affecting the DR

8

Covered Linkway, Bus shelter within RR –submitted as Works Affecting Minor Drainage

• Should be submitted under Works Affecting Other Drainage –Roadside Drain

9

Infra submission – submitted as Works

Affecting Minor Drainage

• Should be submitted under Works Affecting Other Drainage –

Roadside Drain

10

3. INCOMPLETE SUBMISSION

11

Missing Endorsements -DC

Page 7 of PUB-DCCLR

Form – to be endorsed

on the plans

12

Use of DR Endorsement

Drainage Reserve affecting the site

shall be clearly dimensioned and

indicated on the plans.

13

1. Conditions in endorsement shall be complied with.

2. Clear indication of the clearance on all sections & layout plans.

3. IF proposed supports/ footings < 300mm hor. clearance, QP shall clarify the reasons to justify why the

minimum clearance can’t be met.

CL shall be constructed as independent structure from drainage structures and QP shall confirm that

the foundations shall be stable when excavation up to 1m below the invert of affected drain.

4. IF supports/footings were to be mounted on the top slab of extg. covered rdside drain, PE shall submit

structural analysis report confirming extg. drain structures are in satisfactory cond. and capable to withstand

the intended loadings. Otherwise, the extg. drain shall be reconstructed.

Covered Linkways/ Bus Shelters affecting Public Drainage Endorsement

300mm

14

Other Endorsements

• Park Connector Network (PCN) within DR

• Use of DR as Footpath

• Use of DR as Cycling track

• Taxi stand affecting Public Drain

All necessary endorsements as required by PUB shall be clearly shown in

the Site plans for all DC/ DP/ TOP/ CSC stage

15

Essential details not provided

16

Clause 4.4.3 (page 12) of the COP – Vertical Grating

Prior to discharging any storm water within the

development site to the roadside/outlet drain, vertical

grating(s) shall be installed at the outlet discharge point(s)

o the internal drain(s) located within the development

site.

17

Incomplete discharge point details – DC/DP

Missing:

Proposed discharge point, Top level, IL at last

discharge point, & Road level at discharge point

Vertical grating details & provision at the outlet discharge

point of internal drains to public drain not indicated.

18

Vertical grating or vertical grating incorrectly

positioned

19

On the next resubmission, same error was made.

20

Example of Plan with Insufficient information

21

Comments:

22

Comments (cont’d):

23

Submission without referencing to COP.

24

Submission without referencing to COP (cont’d)

25

Non-checking of plans before submitting.

26

No Indication of Platform levels

27

An example of Clear indication of Crest Levels

For development with basement, crest level and swan neck (if applicable)

level shall be clearly indicated on the 1st sty plan

28

New/ A&A Proposal with affected site area >

0.2ha with Detention tank

** Design calculations for detention tank shall be submitted

29

Recap: Submission Requirements for Development

with Detention tank – Drainage DC/ DP Submission

• Catchment & sub-catchment plans clearly indicating catchment for each tank

(if more than one tank is required) and outlet discharge point of internal

drainage system to the public drain

• Site analysis with corresponding runoff coeffs for controlled/ non-controlled

catchment

• Design calculations or modelling results that will be adopted to control the

peak runoff discharge

• Clear site layout plans indicating location and footprint of the detention tank

(s) or pumping facilities – Effective depth of detention tank, connection point to the internal drainage system, swan neck

crest level at the 1st sty level shall be clearly indicated

For new erection and reconstruction works to commercial, industrial, institutional and residential developments greater

than or equal to 0.2 hectares in size and Additions & Alterations (A&A) works to existing commercial, industrial,

institutional and residential developments where affected area is greater than or equal to 0.2 hectares in size, the

following documents endorsed by a QP shall be submitted:-

30

Basement pump

sump provided

with sump pit

Detention Tank 1

Detention Tank 2

Proposal with Basement Pumped Drainage &

Detention tank

31

Catchment plan – Clear Indication of sub-catchment served by each DT,

controlled/ uncontrolled catchments & outlet discharge points

32

PE Calculation For Online Detention

System

33

• Detention tank can only be assessable from the 1st Storey

• Overflow facilities should be provided for the detention

tank

• Outlet from the Detention tank shall be channeled to a

sump/ the internal drain before discharging to roadside

drain

Good Practices for Design of Detention Tank

34

Preparing Your Drainage Detailed Plan (DP)

Submission

Here are some tips to get your 1st DP submission to PUB right, QP

may wish to refer to our online Newsletter Iusse No. 8 on September

2018 on:

• Works Affecting Roadside Drains

• Covered Linkways / Bus Shelters

35

Things to Take Note for Drainage

• Where an entrance culvert / crossing is proposed at a stretch of

closed drain, gratings / openings shall be provided at the closed

drain sections immediately upstream and downstream of the

proposed entrance culvert /crossing.

• The internal width and clear depth of the roadside drains / culverts

(including entrance culverts) shall be at least 600mm wide or align

with the existing drain size (whichever is wider) or the size given by

PUB.

36

Incomplete Info in As-Built Survey plan – TOP/CSC

• Critical to indicate– Outlet discharge point Top & Invert

level

– Rd level at discharge point

– Details of vertical grating

– Vertical grating @ discharge pt

37

Swan neck crest level at 1st level on As-Built

Drawings (for Basement pumped drainage)

38

Good example of RS endorsed As-Built Survey Plans for TOP submission with Offline DT system

AS-BUILT

Indication

Clear indication

alignment, type,

size, flow direction,

summit point,

outlet discharge

point

• Critical to indicate– Alignment, type, size and flow direction

– Discharge point top & Invert level

RS

endorsement

39

Good example of QP endorsed As-Built Drawings

for TOP submission with Detention tank

Inlet &

Outlet

details of DT

PE

endorsement

DT cross

sectional

details

Mark out

Detention

tank

40

Good example of QP endorsed As-Built

Drawings for TOP submission with Detention

tank

Cross sectional

details of Swan

neck 1st floor i.e.

crest level

Mark out

Stormwater tank

location

AS-BUILT

Indication

41

Recap- Items for Drainage TOP submission (involving DT

and pumped drainage system in particular)

a.1. As-built Survey plans indicating platform levels, crest level, adj. road level, and flood protection

levels etc. (to comply with COP Cl.11)

b.

2. As-built Drawings and Calculations for drains, pumped drainage system (basement and DT),

structural detention and retention features and ABC waters design features

3. Standard Operating Procedures for pumped drainage system (basement and DT) (COP Cl.

10.3)

4. PE endorsed inspection and testing & commissioning certificates of the detention tank and

pumps /ABC waters design features

5. PE written confirmation to declare the following:

• The maximum stormwater discharge from the development is in compliance with the maximum

allowable peak runoff stipulated in the COP and constructed according to approved plans.

• He has liaised with the Developer/Owner to ensure that a Maintenance/Managing Agent has

been established to undertake the SOP of the maintenance, operation and monitoring of the

detention tank system and/or ABC Waters design features.

• He has informed the Developer/Owner/MCST/MA/Town Council to conduct and maintain proper

records of regular tests and inspection of the detention tank system, including regular

preventive maintenance of the system which includes but not limited to pumps, valves, and

cleansing of tank and to submit documents, when requested by PUB.

6. Letter of Undertaking from the Developer/Owner/MCST/MA/Town Council of premises with

detention tank systems to submit the Certificate of Inspection on the pumped drainage system

(for basement/detention tank) endorsed by the PE(Mech/Elect).

For Dev. with Detention

tank or basement

pumped drainage

c.7. Standard Operating Procedures of Flood Barriers (both manual and automatic)

8.. PE endorsed inspection and testing of flood barriers, and on-site leak test reports.

For Dev. with Flood

barrier

42

Recap: Submission for CSC/ DLP Application with

External Drainage Works

• QP to fill up the Handing Over form

as part of CSC submission to

facilitate site inspection

** There shall not be any hardcopy for filling in on site

anymore

43

RECENT NEW CHANGES

44

1. New DC Submissions with effect 1 Dec 18

To indicate all ground and platform levels

using SHD format:

• 104.5mRL (based on Mean sea level of

100.000m) will be shown as 4.0m

(based on SHD = 0.000m)

• QPs are required to endorse on the

plans (DC/DP/TOP/CSC) the following

note: “The reduced levels are based on

the Singapore Height Datum of

0.000m”). This phrase shall be added

to the rest of PUB’s NOTES on the DC

plan.

PUB-DCCLR-NOV2018 Ver 1.3

45

Application for Deviation On

Drainage Matter (PUB-DEV-

DRA)

• To provide a clear channel for

QPs to surface alternative designs

deviating from PUB’s COP and

requirements for management

decision

2. New CORENET FORMS with effect

16 Nov 18

46

Application for PUB Overall

Clearance for CSC (PUB-CSC-

CLR)

• For QPs to obtain PUB’s overall

CSC Clearance (drainage +sew)

before applying for BCA’s CSC

Clearance.

• Email requests to BPU have

ceased since 1st January 2019.

47

Application for PUB Overall

Clearance for TOP (PUB-TOP-CLR/

• For QPs to obtain PUB’s overall TOP

clearance (drainage +sew) before

applying for BCA’s TOP Clearance.

• Email requests to BPU have ceased

since 1st January 2019.

48

USEFUL ONLINE LINKS ON

DRAINAGE SUBMISSIONS

49

Useful Links (found in PUB’s QP Portal)

• Useful drainage design guidelines can be found in the following

www.pub.gov.sg/compliance/qualifiedpersonsportal/cop

COP on Surface Water Drainage (note that 7th edition has taken

effect 1 Dec 18)

Drainage

• Drainage Handbook on Managing Urban Runoff

• Technical Guide on On-site Stormwater Detention Tank

Systems

Alternate Sources of Water

• Rainwater Harvesting

ABC Waters Design Guidelines

Quick submission guides can be found in the following

www.pub.gov.sg/compliance/qualifiedpersonsportal/quicksubmissionguides

50

SUMMARY THE BPU ONLINE NEWSLETTER ISSUED

(FROM NO. 1 TO 8)

51

THANK YOU