preliminary design of waste water treatment system …

AGR GEOSCIENCES PTY LTD

AGR GeoSciences Pty Ltd ABN: 32 601 372 632 ACN: 601 372 632

P PO Box 178 Mount Clear VIC 3350 M 03 5332 2917 E [email protected] W agrgeo.com.au

PRELIMINARY DESIGN

OF

WASTE WATER TREATMENT SYSTEM

FOR

39 KARINGAL DRIVE, WYE RIVER

Prepared for: Fraser and Anne Gibson

Prepared by:

David J Horwood Senior Engineering Geologist

BAppSc (Geology); MAusIMM CP(Geo)

Approved by:

Reference No.

18G285LCA

Date:

11/7/2018

Revised:

mailto:[email protected]

39 Karingal Drive Wye River

REPORT REF. 18G285LCA

1. Project Summary Site Address 39 Karingal Drive Wye River

Council Area Colac-Otway Shire (COS)

Allotment Size 927m2

Water Supply Tank water

Development New residential dwelling

Bedrooms/Occupants 3 bedrooms / max. 4 occupants @150L/per/day

Daily Flow Rate 600 L/day

Tenancy Permanent

Constraints Steep slopes

Low permeable clay soil (Category 5 Light Clay)

LCA Report 2020 Engineering Solutions (2020), Doc. No. ES1734.6,

2017

Architectural Design Kris Thomas Building Design

2. Design Summary Treatment level Advanced Secondary

Disposal system Pressure compensated sub-surface drip irrigation

Proposed disposal area

location

Upslope of proposed dwelling

System design and sizing Hydraulic loading and water balance

Design Daily Flow Rate 600 L/day

Minimum disposal area 276m2

Maximum application rate 2.65mm/day – 1.6mm/day

Setbacks and buffer distances Minimum 3.0m from dwelling to effluent field;

Minimum 0.5m from west boundary to effluent field;

Minimum 0.5m from east boundary to effluent field;

Minimum 0.5m from north boundary to effluent field

Construction type Split installation of irrigation lines; part irrigation direct to

natural slope of land aligned parallel to the contour; part

irrigation into low terraces with 200-400mm high sleeper

walls spaced 800-1800mm apart.

Installation depth 100-150mm into 200-250mm of topsoil.

Line spacing 0.8m - 1.0m

Surface Preparation None specified

Drainage measures Surface drainage (spoon drain or similar) across northern

boundary.

Cut off drain up to 1m deep (or above weathered rock is

shallower) across allotment down slope of effluent field.

Installation requirements Final detailed design and installation of irrigation system

by licensed plumber/irrigation specialist experienced with

irrigation systems on steep slopes.

Post Installation requirements Revegetation of slopes with high biomass, high

transpiration, dense ground covering grasses and shrubs.

Biannual application of 2L of liquid gypsum to dispersed

via pump well of irrigation system.



3. Waste Water Treatment Design

Secondary treatment of ‘All Waste’ effluent (20/30/10) via AWTS treatment plant, followed by tertiary treatment using UV or chlorine disinfection (10/10/10).

4. Disposal System Design

4.1. DESIGN PHILOSOPHY

The preferred system is pressure compensating subsurface drip irrigation. Subsurface irrigation will provide even and widespread dispersal of the treated

effluent within the root-zone of plants, does not require a reserve area and can be installed on slopes up to 30% (17o) before requiring a specialised irrigation design. It will also ensure that the risk of effluent being transported off-site will be negligible

and is the most accepted method of onsite waste disposal for minimising the risk of slope instability.

Aim of design options to minimise disposal footprint and invasive impact to the land

while also mitigating down slope subsurface migration, controlling surface run off and avoiding concentrated absorption and the need for winter storage.

Irrigation fields sized by water balance adopting the principle of deep seepage based on measured saturated hydraulic conductivity (ksat) in accordance with

recommendations of the peer reviewed guidelines of the Tennessee Valley Authority (2004).

Design Irrigation Rate (or application rate) reduced in accordance with Section M9.3 and Table M2 of AS1547:2012 for sloping sites to avoid or minimize slope

modification and terracing. Application rate is reduced by increasing application area to ensure effluent migration is taken up within topsoil and plant root system.

4.2. DESIGN PARAMETERS

Application soil: clayey SILT (Category 4 CLAY LOAM); measured ksat of 0.55m/day.

Limiting layer: sandy CLAY (Category 4-5, CLAY LOAM to LIGHT CLAY); measured ksat of 0.07m/day.

Measured ksat for soil layers derived from constant head test data conducted by

2020.

Proposed irrigation areas sized by water balance using climate data from COS

Domestic Waste Water Management Plan.

Crop factors applied in water balance taken form MAV Guidelines, 2014.



The retained rainfall factor used in the water balance derived using the Rational Equation to calculate a weighted run off coefficient based on published run off coefficients for different land uses and surfaces and total catchment size.

A 40% reduction in the application rate (DIR) has been adopted in accordance with

the recommendations in Table M2 of AS1547:2012 for irrigation applied direct to the natural contour of the land.

4.3. DESIGN DESCRIPTION

Split Disposal with Low Terracing

Pressure compensated sub-surface drip irrigation implementing two methods of

disposal; partial irrigation to low terraces and partial direct irrigation to the natural contour of the land.

The overall disposal area is separated into two areas, the first area sized according to

a portion of the total daily wastewater load being disposed via irrigation lines in low

terraces.

The part terraced disposal strategy involves constructing low terraces parallel to the natural contour.

Terraced portion of the disposal system to be located on a section of the slope with an average gradient of 15o. It is acknowledged that topographical variation is likely

and slope angles up to 20o may occur within the terraced area.

Where the slope angle is around 15o, low retaining walls up to 200mm high would be

constructed across the width of the slope spaced approximately 1400mm apart (horizontal). An example design is provided as Appendix IV.

The aim of this design is to reduce the slope angle of the application area from a

25% gradient (15o) to a 10% gradient (6o). In doing so, the final application rate for

disposal to the low terrace section does not require reduction in accordance with Table M2, AS1547:2012 and keeps the terrace wall as low as practicable.

Where topographical variation occurs (up to 20o), low retaining walls may be up to

400mm high, spaced up to 1800mm apart, or alternatively 200mm high and spaced

up to 800mm apart. Alternate designs for 20o slope variations are provided in Appendix V.

Wall positions, heights and spacing’s should be at the discretion of the installer based

on the actual topography.

Low terraces may be constructed by hand using 200-400mm high sleepers and star

pickets with terraces filled with topsoil. Simply constructed low terraces are less invasive, utilize low impact construction methods and cost less than standard

terraces.



The second disposal area is sized according to the remaining portion of the total daily wastewater load being disposed of via irrigation lines installed directly to the natural contour of the slope at a significantly reduced application rate in order to minimize

terracing.

Remaining effluent is dispersed widely and evenly allowing for a 40% reduction in the application rate to accommodate for down slope linear hydraulic flow and maximum absorption/evapotranspiration. Reduced application rate is effectively achieved by

increasing the disposal area beyond the minimum.

Direct application irrigation is low impact and can be installed by hand with minimal disturbance.

The combined effluent disposal area would be 276m2.

The following table provides the areas and application rates required in order to implement this strategy:

Table 1: Area Sizing for Split Disposal Strategy

Disposal Method

Maximum

Wastewater Loading

Minimum Disposal Area

Maximum Application

Rate

Reduction in

Minimum Application

rate

Low Terracing 400L/day 151m2 2.65mm/day -

Direct Application 200L/day 125m2 1.6mm/day 40%

600L/day 276m2



5. Considerations for Irrigation System

Irrigation lines to contain pressure compensating emitters (drippers) that employ a biocide to prevent build-up of slimes and inhibit root penetration.

Irrigation pump sized properly to ensure adequate pressure and delivery rate to the

irrigation network.

Irrigation system design must allow for differential loading to terraced and non-

terraced disposal.

Positioning of the low terraces should utilize the shallowest part of the slope. The

Irrigation plan in Appendix I indicates the part of the slope with a measured 15o slope angle. Topographical variation is expected and alternate low terrace designs are

provided in Appendix V.

Filter installed in the main line to remove fine particulates that could block the emitters cleaned regularly (typically monthly) following manufacturer’s instructions.

Vacuum breakers installed at the high point/s in the system to prevent air and soil being sucked back into the drippers when the pump shuts off.

Installation of flushing valves to allow periodic flushing of the lines, which should be

done at six monthly intervals. Flush water should be returned to the treatment

system via a return line.

All trenching used to install the pipes to be backfilled properly to prevent preferential subsurface flows along trench lines.

DAVID J HORWOOD BAppSc (Geology)

C.E.T. ACCREDITED



APPENDIX I: Split Disposal Waste Water Plan

Proposed Spoon drain

Maintain a minimum 3.0m setback to buildings below effluent field

>3.0m to building

0.5m setback to east boundary

125m2

0.5m setback to west boundary

Recommended cut of drain

151m2

0.5m setback to north-west boundary



APPENDIX II: Constant Head Test Data and Ksat Calculations

COMPUTATION SHEET

Project: Job No.: 18E285LCA

Comp: DH

Date: 4/07/18

Client: Attendee:

Subject: Review: DH

SOIL PERMEABILITY CALCULATIONS

Refer Site Investigation Plan for locations of test sites

Refer Borehole Profiles for soil types and depths encountered

Test Number: 1 2 3 4 5 6 7 8

Time Step (min): 1 1 1 1 1

Hole Depth(mm): 300 300 300 300

Hole Dia. (mm) 100 100 100 100

Tube Inside Dia. (mm): 66 66 66 66

Lim. Layer Depth(mm):

Lim. Layer Material:

Tube Insert. Depth: 50 50 50

Tube Number:

Test Liquid: Tap Water Tap Water Tap Water Tap Water Tap Water Tap Water Tap Water Tap Water

Soil Moisture:

Time

Time 0 207 288 180 273

Reading: 1 344 304 216 284

Drop: 137 16 36 11

Reading: 2 389 316 250 294

Drop: 45 12 34 10

Reading: 3 414 328 283 308

Drop: 25 12 33 14

Reading: 4 338 310 321

Drop: 10 27 13

Reading: 5 348 340 339

Drop: 10 30 18

Reading: 6 359 357

Drop: 11 18

Reading: 7 369 376

Drop: 10 19

Reading: 8 379 396

Drop: 10 20

Reading: 9 388 416

Drop: 9 20

Reading: 10 398 441

Drop: 10 25

Reading: 11 466

Drop: 25

Reading: 12 491

Drop: 25

Reading: 13 516

Drop:

Reading: 14

Drop:

Reading: 15

Drop:

Reading: 16

Drop:

Reading: 17

Drop:

Reading: 18

Drop:

Assumed Clay Loam Test Data

39 Karingal DriveWye River

Fraser and Anne GibsonSoil Permeability Calculations - 1 min step

1of2

COMPUTATION SHEET


Comp: DH

Date: 4/07/18

Client: Attendee:

Subject: Review: DH

Assumed Clay Loam Test Data



1 2 3 4 5 6 7 8

Starts uniform drop 2 4 1 5

Stops uniform drop 3 10 5 9

Time elapsed(min) 1 6 4 4

Total Drop (cm) 2.5 6.0 12.4 7.7

z 2.5 3.0 2.5 2.5

Flow, Q (cm3/min) 85.5 34.2 106.1 65.9

Ksat (cm/min) 0.0465 0.0146 0.0576 0.0358

Ksat (m/day) 0.669 0.210 0.830 0.515

Average Ksat (m/day) 0.5563

0

20

40

60

80

100

120

140

160

0 5 10 15 20

∆H

eig

ht

(per

5 m

in in

cre

men

t),

mm

Time Elapsed, min

Test No. 1

Test No. 2

Test No. 3

Test No. 4

Test No. 5

Test No. 6

Test No. 7

Test No. 8

2of2

COMPUTATION SHEET


Comp: DH

Date: 4/07/18

Client: Attendee:

Subject: Review: DH

SOIL PERMEABILITY CALCULATIONS

Refer Site Investigation Plan for locations of test sites

Refer Borehole Profiles for soil types and depths encountered

Test Number: 1 2 3 4 5 6 7 8

Time Step (min): 5 5

Hole Depth(mm): 300 300

Hole Dia. (mm) 100 100

Tube Inside Dia. (mm): 66 66

Lim. Layer Depth(mm):

Lim. Layer Material: SC SC

Tube Insert. Depth: 50 50

Tube Number:

Test Liquid: Tap Water Tap Water Tap Water Tap Water Tap Water Tap Water Tap Water Tap Water

Soil Moisture:

Time

Time 0 288 222

Reading: 5 334 264

Drop: 46 42

Reading: 10 347 271

Drop: 13 7

Reading: 15 356 294

Drop: 9 23

Reading: 20 369

Drop: 13

Reading: 25 380

Drop: 11

Reading: 30 393

Drop: 13

Reading: 35 405

Drop: 12

Reading: 40 415

Drop: 10

Reading: 45

Drop:

Reading: 50

Drop:

Reading: 55

Drop:

Reading: 60

Drop:

Reading: 65

Drop:

Reading: 70

Drop:

Reading: 75

Drop:

Reading: 80

Drop:

Reading: 85

Drop:

Reading: 90

Drop:



1of2

COMPUTATION SHEET


Comp: DH

Date: 4/07/18

Client: Attendee:

Subject: Review: DH



1 2 3 4 5 6 7 8

Starts uniform drop 10 5

Stops uniform drop 40 15

Time elapsed(min) 30 10

Total Drop (cm) 6.8 3.0

z 2.5 2.5

Flow, Q (cm3/min) 7.8 10.3

Ksat (cm/min) 0.0042 0.0056

Ksat (m/day) 0.061 0.080

Average Ksat (m/day) 0.0705

0

5

10

15

20

25

30

35

40

45

50

0 10 20 30 40 50 60 70 80 90 100

∆H

eig

ht

(per

5 m

in in

cre

men

t),

mm

Time Elapsed, min

Test No. 1

Test No. 2

Test No. 3

Test No. 4

Test No. 5

Test No. 6

Test No. 7

Test No. 8

2of2



APPENDIX III: Water Balance

Project: Job No.:

Comp: DH

Date: 5/07/2018

Client: Attendee:

Subject: Review:

INPUT DATA

Design Wastewater Flow Q 400 L/day

Design Seepage Rate DSR 4.9 mm/day

Trial Land Application Area LAA 151 m2

Crop Factor C MAV unitless

Rainfall Runoff Factor RF 0.75 untiless

Effective Void Ratio N 0.3 unitless

Minimum Freeboard Topsoil Layer F 100 mm

Mean Monthly Pan Evaporation Data Kennett River SILO Data Colac-Otway DWMP

Mean Monthly Rainfall Data Kennett River SILO Data Colac-Otway DWMP

Parameter Symbol Formula Units Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total

Days in month D days 31 28 31 30 31 30 31 31 30 31 30 31 365

Evaporation E mm/month 129 106 90 58 39 28 32 44 61 87 102 121 897.0

Rainfall R mm/month 43 45 57 71 99 105 112 128 108 94 65 54 981.0

Crop Factor C unitless 0.80 0.80 0.70 0.70 0.60 0.60 0.60 0.60 0.70 0.80 0.80 0.80

OUTPUTS

Evapotranspiration ET E x C mm/month 103.2 84.8 63.0 40.6 23.4 16.8 19.2 26.4 42.7 69.6 81.6 96.8 668

Seepage S DIR x D mm/month 151.9 137.2 151.9 147.0 151.9 147.0 151.9 151.9 147.0 151.9 147.0 151.9 1788.5

Total Outputs ET+S mm/month 255.1 222.0 214.9 187.6 175.3 163.8 171.1 178.3 189.7 221.5 228.6 248.7 2456.6

INPUTS

Retained Rainfall RR R x RF mm/month 32.3 33.8 42.8 53.3 74.3 78.8 84.0 96.0 81.0 70.5 48.8 40.5 735.8

Applied Effluent W QxD L/month 12400 11200 12400 12000 12400 12000 12400 12400 12000 12400 12000 12400 146000

Total Inputs RR+W mm/month 44.7 45.0 55.2 65.3 86.7 90.8 96.4 108.4 93.0 82.9 60.8 52.9 881.8

DISPOSAL RATE

Disposal Rate DR (ET+S)-RR mm/month 222.9 188.3 172.2 134.4 101.1 85.1 87.1 82.3 108.7 151.0 179.9 208.2

LAND AREA REQUIRED FOR ZERO STORAGE m2

56 59 72 89 123 141 142 151 110 82 67 60

MINIMUM AREA REQUIRED FOR ZERO STORAGE: 151 m2

ADOPTED LAND APPLICATION AREA: 151 m2

DESIGN APPLICATION RATE: 2.65 mm/day

STORAGE CALCULATIONApplication Rate AR Q/LAA mm/month 82.1 74.2 82.1 79.5 82.1 79.5 82.1 82.1 79.5 82.1 79.5 82.1

Storage For The Month ST AR-DR mm/month -140.7 -114.1 -90.0 -54.9 -18.9 -5.6 -5.0 -0.2 -29.2 -68.9 -100.4 -126.1

Increase In Depth Of Stored Effluent ΔH ST/N mm/month -469.1 -380.3 -300.1 -182.9 -63.1 -18.6 -16.6 -0.6 -97.4 -229.6 -334.6 -420.3

Storage Remaining From Previous Month mm/month 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Cumulative Storage At End Of Month CS mm 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Cumulative Storage From Previous Year CS mm 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Maximum Storage Depth for Nominated Area MS 0 mm

Fraser and Anne Gibson

Split Disposal - Part Low Terrace

WATER BALANCE COMPUTATION SHEET

39 Karingal Drive 18G285LCA

Wye River



Project: Job No.:

Comp: DH

Date: 5/07/2018

Client: Attendee:

Subject: Review:

INPUT DATA

Design Wastewater Flow Q 200 L/day

Design Seepage Rate DSR 4.9 mm/day

Trial Land Application Area LAA 125 m2

Crop Factor C MAV unitless

Rainfall Runoff Factor RF 0.75 untiless

Effective Void Ratio N 0.3 unitless

Minimum Freeboard Topsoil Layer F 100 mm

Mean Monthly Pan Evaporation Data Kennett River SILO Data Colac-Otway DWMP

Mean Monthly Rainfall Data Kennett River SILO Data Colac-Otway DWMP

Parameter Symbol Formula Units Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total

Days in month D days 31 28 31 30 31 30 31 31 30 31 30 31 365

Evaporation E mm/month 129 106 90 58 39 28 32 44 61 87 102 121 897.0

Rainfall R mm/month 43 45 57 71 99 105 112 128 108 94 65 54 981.0

Crop Factor C unitless 0.80 0.80 0.70 0.70 0.60 0.60 0.60 0.60 0.70 0.80 0.80 0.80

OUTPUTS

Evapotranspiration ET E x C mm/month 103.2 84.8 63.0 40.6 23.4 16.8 19.2 26.4 42.7 69.6 81.6 96.8 668

Seepage S DIR x D mm/month 151.9 137.2 151.9 147.0 151.9 147.0 151.9 151.9 147.0 151.9 147.0 151.9 1788.5

Total Outputs ET+S mm/month 255.1 222.0 214.9 187.6 175.3 163.8 171.1 178.3 189.7 221.5 228.6 248.7 2456.6

INPUTS

Retained Rainfall RR R x RF mm/month 32.3 33.8 42.8 53.3 74.3 78.8 84.0 96.0 81.0 70.5 48.8 40.5 735.8

Applied Effluent W QxD L/month 6200 5600 6200 6000 6200 6000 6200 6200 6000 6200 6000 6200 73000

Total Inputs RR+W mm/month 38.5 39.4 49.0 59.3 80.5 84.8 90.2 102.2 87.0 76.7 54.8 46.7 808.8

DISPOSAL RATE

Disposal Rate DR (ET+S)-RR mm/month 222.9 188.3 172.2 134.4 101.1 85.1 87.1 82.3 108.7 151.0 179.9 208.2

LAND AREA REQUIRED FOR ZERO STORAGE m2

28 30 36 45 61 71 71 75 55 41 33 30

MINIMUM AREA REQUIRED FOR ZERO STORAGE: 75 m2

ADOPTED LAND APPLICATION AREA: 125 m2

DESIGN APPLICATION RATE: 1.60 mm/day

STORAGE CALCULATIONApplication Rate AR Q/LAA mm/month 49.6 44.8 49.6 48.0 49.6 48.0 49.6 49.6 48.0 49.6 48.0 49.6

Storage For The Month ST AR-DR mm/month -173.3 -143.5 -122.6 -86.4 -51.5 -37.1 -37.5 -32.7 -60.7 -101.4 -131.9 -158.6

Increase In Depth Of Stored Effluent ΔH ST/N mm/month -577.5 -478.2 -408.5 -287.8 -171.5 -123.5 -125.0 -109.0 -202.3 -338.0 -439.5 -528.7

Storage Remaining From Previous Month mm/month 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Cumulative Storage At End Of Month CS mm 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Cumulative Storage From Previous Year CS mm 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Maximum Storage Depth for Nominated Area MS 0 mm


Split Disposal - Part Direct Irrigation

WATER BALANCE COMPUTATION SHEET

39 Karingal Drive 18G285LCA

Wye River



APPENDIX IV: Run Off Calculations

Project: Job No.: 18G285LCA

Comp: DH

Date: 4/07/2018

Client: Attendee:

Subject: Review:

Total area km2

960 m2

Prop. Of Land Ai Ci

1 0.25

Atotal 1.0

0.250 Weighted C = CiAi /Atotal

Run off Coefficient

NOTE: Runoff Factor used in

LCA water balance

calculations is the inverse of

the Runoff Coefficient. Ie the

proportion of water retained

or that infiltrates the soil as

apposed to water runs off. If

C = 0.3 then RF = 0.7

Runoff coefficient for total area (Weighted C)

Steep, forrest, clayey soils

Land Use

Proportional Land Use Zones areas of Total Catchment Area


39 Karingal Drive

Wye River

Runoff Computations



APPENDIX IV: Suggested Low Terrace Design (15o slope)



APPENDIX V: Alternate Low Terrace Designs (20o slope)

preliminary design of waste water treatment system …

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