drainage report-ash disposal area - rev c_sect 3.2

7/29/2019 Drainage Report-Ash Disposal Area - Rev C_sect 3.2

1/10

Drainage Report For Proposed Ash Disposal Area

Originator

HSSIdentification number

MNG/04/P/UEW10D15--/DC/534Rev.

CDate

4-01-2013Lang.

EnSheet

9/10

Use 300mm diameter perforated pipe contained in 20mm to 40mm drainage aggregate wrap

with geotextile is proposed at edge of the ash ponds to evacuate the surface flow faster. The

drainage layout plan for both Ash Pond A and Ash Pond B are presented in Appendix C.

3.2 Detention Ponds

3.2.1 Design Criteria and Standard

Methodology for the detention pond sizing is based on Water Balance Analysis Concept

design which describes the flow of water in and out of a system. Assumptions used in this

report are as follows:

i) Detention pond area allocated in this development layout plan will serve as a dry

detention pond (Pond A & Pond B).

ii) The detention pond will be designed to cater for 1 in 25 year 24 hour storm event and

check for 1 in 100 year 24 hour storm event arising from development discharge from

the ash pond area according to MASMA requirement.

iii) The detention pond sizing is calculated based on the optimal ash deposit in Pond A

and Pond B.

iv) Assumption of 5% void of compacted ash disposal to considered as a storage

capacity.

The water balance calculation for both Ash Ponds has been calculated based on two different

storm events i.e. 25-yr and 100-yr ARI, 24-hrs rainfall. The storage volume is calculated based

from net amount of runoff volume with free board 0.5m at elevation 2.8 mLSD.

Summary of the water balance calculations for Detention Ash Pond A and Ash Pond B are

shown in Table 1 and 2 respectively. The details of the calculations are presented in Appendix

A and B.

3.2.2 Pump

Based from the above calculation, there were no excess volumes for single storm event of 24

hour rainfall. However, it is recommended to provide a 100 m3/hr pump for each ash ponds to

cater excess volume arising from series of storm event which eventually will be accumulated


2/10

Drainage Report For Proposed Ash Disposal Area

Originator

HSSIdentification number

MNG/04/P/UEW10D15--/DC/534Rev.

CDate

4-01-2013Lang.

EnSheet

10/10

storm runoff in the ponds which need to be extracted to waste water treatment plant.

Reference to Ash Disposal Management Procedure, section 13.3 stated that any

contaminated surface flow shall be pumped to waste water treatment plant and the

contaminated water also can be used directly on the disposed ash for dust control (section

13.2).

Table 1: Summary of Water Balance Calculation for Pond A

E vapora tion As hPondAAshDet.Pond

AreaPondStorage, S StorageDepth

Pump

Capacity**

(mm/day) (m2) (m2) (m3) (m) (m3/hr)

1. 24hr 25yrARI 7.42 6,482 1.39

2 . 24hr 100yrARI 8.2 8,250 1.77

Note:

1. Rainfalldata(rainfallintensity)isreferredfromERandHP1 Vol.II IDFCurve,2010

2. AssumeDeadWLat0.5mLSDtohavebetterpumpoperation

3. **Recommendedtoprovidepumpforexcessvolumearisingfromseriesofstormeventandfordustsuppression.

1003.0

No. StormD urat ion R ainfal l

94,485 4,656

Table 2: Summary of Water Balance Calculation for Pond B

EvaporationAshPondArea,

FBA

AshDet.Pond

AreaPondStorage, S StorageDepth

Pump

Capacity**

(mm/day) (m2) (m2) (m3) (m) (m3/hr)

1. 24hr 25yrARI 7.42 3,957 0.89

2 . 24hr 100yrARI 8.2 4,983 1.12

Note:

1. Rainfalldata(rainfallintensity)isreferfromHP1 Vol.II IDFCurve,2010

2.Assume

Dead

WL

at

0.5

mLSD

to

have

better

pump

operation

3. **Recommendedtoprovidepumpforexcessvolumearisingfromseriesofstormeventandfordustsuppression.

1003.0

No. StormD urat ion R ainfal l

54,830 4,446

7.0 Conclusion

Based on the above calculations for detention facilities in the ash ponds, the following

recommendations are made:

1. The freeboard of the detention pond is 0.5m (100-yr ARI) @ elevation 2.8 mLSD and

the proposed stage 1 pump cut in level @ elevation 0.5 mLSD.

2. The excess volume arising from series of storm event shall be discharge to water

treatment system assisted by pumps.

3. The detention pond size is 97m (length) x 48m (width) x 2.3m (effective depth) has

been adopted for Pond A and the Pond B detention pond size is 117m (length) x 38m

(width) x 2.3m (effective depth) has been adopted.


3/10

APPENDIX A

Water Balance Calculation for Pond A


4/10

WaterBalanceCalculation

Evaporation

AshPondA

AshDet.Pond

Area

PondStorage,

SStorageDepth

Pump

Capacity**

(mm/day)

(m2)

(m2)

(m3)

(m)

(m3/hr)

1.

24hr25yrARI

7.42

6,482

1.39

2.

24hr100yrAR

I

8.2

8,250

1.77

Note:

1.

Rainfalldata(rainfallintensity)isreferredfromERandHP1Vol.IIIDFCurve,20

10

2.

AssumeDeadW

Lat0.5mLSDtohavebetterpumpoperation

3.

**Recommendedtoprovidepumpforexcessvolumearisingfromseriesofstorm

eventandfordustsuppression

100

SummaryofWaterBalanceCalculationForDifferentStormEven

tPondA

3.0

No.

StormDuration

Rainfall

94,485

4,656


5/10

WATERBALANCECALCULATION

ASHPOND PONDA(24hrRainfall 25yrARI)

Data:

1. AnnualRainfall,Rf24

I25yr = 7.42 mm/hr

2. Evaporation,Ev = 3 mm/day

3. PFAarea = 94,485 m2

4. AssumeDeadWaterLevel,DWL = 0.5 mLSD

5. AshDetentionPondArea = 97mx48m = 4,656 m2

6. FreeBoard = 0.5 m (RefertoDesignChecklistforSWM,JPS,2010)

@Level = 2.8 mLSD

DesignCalculation

Runoffvolume = [7.42mm/hr x 24hrx 94,485m2]

= 16,826 m3

Evaporationvolume = [ 3.0mm/day x 4656m2

]

= 13.97 m3

StoragevolumefromAshPond = 5%x(PFAarea DetentionPondArea)xLivestorage

(Allowed5%voidofAsh) = 10,330 m3

DepthinADP = SPondArea

= 6,481.59

4,656

= 1.39 m

Livestorageavailabe = 2.3 m (freeboard0.5m)

Hence,noexcessrunoff


6/10


ASHPOND PONDA(24hrRainfall 100yrARI)

Data:

1. AnnualRainfall,

Rf

24

I100yr = 8.2 mm/hr


3. PFAarea = 94,485 m2




@Level = 2.8 mLSD

DesignCalculation

2 = . ,

= 18,595 m3

Evaporationvolume = [3.0mm/day x 4656m2

]

= 13.97 m3



DepthinADP = S

PondArea

= 8,250.35

4,656

= 1.77 m




7/10

APPENDIX B

Water Balance Calculation for Pond B


8/10

WaterBalanceCalculation

Evaporation

AshPondArea,

FBA

AshDet.Pond

Area

PondStorage,

SStorageDepth

Pump

Capacity**

(mm/day)

(m2)

(m2)

(m3)

(m)

(m3/hr)

1.

24hr25yrARI

7.42

3,957

0.89

2.

24hr100yrAR

I

8.2

4,983

1.12

Note:

1.

Rainfalldata(rainfallintensity)isreferfromHP1

Vol.IIIDFCurve,2010

2.

AssumeDeadW

Lat0.5mLSDtohavebetterpumpoperation

3.

**Recommendedtoprovidepumpforexcessvolumearisingfromseriesofstorm

eventandfordustsuppression.

100

SummaryofWaterBalanceCalculationForDifferentStormEven

tPondB

3.0

No.

StormDuration

Rainfall

54,830

4,446


9/10


ASHPOND PONDB(24hrRainfall 25yrARI)

Data:


I25yr = 7.42 mm/hr


3. FBAarea = 54,830 m2




@Level = 2.8 mLSD

DesignCalculation


= 9,764 m3

Evaporationvolume = [3.0mm/day x 4,446m2

]

= 13.34 m3



DepthinADP = SPondArea

= 3,956.63

4,446

= 0.89 m




10/10


ASHPOND PONDB(24hrRainfall 100yrARI)

Data:


I100yr = 8.2 mm/hr


3. FBAarea = 54,830 m2




@Level = 2.8 mLSD

DesignCalculation


= 10,791 m3

Evaporationvolume = [3.0mm/day x 4,446m2

]

= 13.34 m3



DepthinADP = S

PondArea

= 4,983.05

4,446

= 1.12 m



drainage report-ash disposal area - rev c_sect 3.2

Documents