Re: On-site Wastewater Management Assessment Lot 7, DP

3 June 2021 5QS Ref: 218022

Julian & Amy Budgeon 25 Blue Hills Lane JEIR NSW 2582 Dear Mr & Mrs Budgeon,

Re: On-site Wastewater Management Assessment Lot 7, DP 845104 25 Blue Hills Lane, Jeir

1 Introduction

An on-site wastewater dispersal geotechnical investigation has been undertaken on the

above property in accordance with AS/NZS1547:2012 ‘On-site Domestic Wastewater

Management’ and the Environment and Health Protection Guideline ‘On-site Sewage

Management for Single Households’.

This report provides details of the investigation and recommendations for on-site dispersal

of treated sewage wastewater at the subject site. A Site and Soil Evaluation and various

dispersal area calculation sheets that address specific matters as required by

AS/NZS1547:2012 ‘On-site Domestic Wastewater Management’ and the Environment and

Health Protection Guideline ‘On-site Sewage Management for Single Households’ have been

attached.

Details of the property and pertinent site features may be seen on the attached drawings

218022/EFD1 and details of the site assessment and dispersal area calculations are set out

in the attached Site and Soil Evaluation and irrigation area calculation sheets.

YASS HARDEN CANBERRA SYDNEY GOSFORD NEWCASTLE PORT MACQUARIE

5QS Consulting Group North is a division of C2F Pty Ltd ABN 48 137 633 124

6226 5598 [email protected] PO Box 645 Yass NSW 2582

TM

5QS Consulting Group 3 June 2021 Consulting Engineers 5QS Ref: 218022

2

On-site Wastewater Management Assessment 25 Blue Hills Lane, Jeir

2 Project Description

The investigation was for the dispersal of aerated wastewater treatment system (AWTS)

treated domestic wastewater via surface irrigation.

The assessment has been based on;

a) A proposed new residence containing 4 bedrooms.

b) The residence connected to tank water.

The surface grades in the vicinity of the proposed available dispersal area were planar with

grades of approximately 3% to 10% downslope to the west.

The proposed spray irrigation area will be located to the north and west of the proposed

residence.

The location of the proposed residence, AWTS and spray irrigation dispersal area and

pertinent site features are set out on the attached drawing 218022/EFD1.

3 Desktop Study

3.1 Soil Landscape

The site lies within the Binalong Soil Landscape as described in the Soil Landscapes of the

Goulburn 1:250,000 Sheet published by the Soil Conservation Service of NSW (1991).

The Binalong Soil Landscape comprises soils that have formed in situ from alluvial – colluvial

material derived from the parent rock in the underlying Douro Volcanics. The Binalong Soil

Landscape landform is typically undulating low hills with slope gradients 3 – 10% on a local

relief between 30m and 90m. There is some gullying of drainage lines and convergent

integrated tributary drainage patterns. Elevations vary between 500 and 630m AHD.

Moderately deep, bright yellowish brown or rarely red, gradational or occasionally duplex

textured, weakly to moderately structured soils occur on crests and sideslopes. A2 horizons

are sometimes present as is mottling of the subsoil. Soil reaction is neutral. The soils are

similar to Yellow Earths whilst the better structured, heavier textured variants could be

considered Xanthozems. Other soil groups likely to occur include Red Earths and Non-calcic

Brown Soils and Solodic Soils on footslopes and in drainage lines. Mottled slightly alkaline

Grey Clays may occur beneath the solum. These have been interpreted as relict or subsolar

features (van Dijk 1959, 1969). Salinity is not normally present in these soils. – [Hird 1991]


3


Summary of Key Features of the Binalong Soil landscape

Lithosols Stoney Earths Colluvial

Podzolic Soils

Dominance Common Common Minor

Landform element Crests,

Sideslopes

Crests,

Sideslopes

Footslopes

Surface condition Loose Loose Loose

Drainage Rapid Well drained Impeded

Soil permeability High High Moderate

Watertable depth None None Seasonal

Depth to bedrock >0.5m 0.5m – 1m > 2m

pH (topsoil) Acid Acid Acid

Known nutrient

deficiencies

N, P, K, S, & most

trace elements

N, P, K, S, & most

trace elements

N, P, K, S, & most

trace elements

Soil salinity Not present Not present Not present

Erodibility

(topsoil/subsoil)

High / High High / High High / Low

USCS (subsoil) GM, GC GC SC, CL

3.2 Groundwater Bore Search

A groundwater bore search was undertaken using the NSW Government’s online search

facility at allwaterdata.water.nsw.gov.au.

The search identified one registered groundwater bore within a 500m radius from the

proposed dispersal area.

Table 1 –Registered groundwater bores within 500m of the site.

Mark Distance Direction Depth to aquifer Purpose

GW400412 300m north 35+m Domestic/Stock

Provided wastewater treatment and dispersal options detailed in this report are

implemented it is believed that the dispersal of treated wastewater on the site does not pose

a risk to groundwater at any registered bore.


4


3.3 Groundwater Vulnerability

Yass Valley Local Environment Plan 2013, cl 6.4 Groundwater Vulnerability, requires the

following matters set out in Table 2 to be addressed:

Table 2 - Groundwater Vulnerability Assessment

2 Is the site within land identified as

“Groundwater vulnerability” on the

Groundwater Vulnerability Map?

No

4 Methodology and Calculations

4.1 Fieldwork

The fieldwork undertaken on 12 May 2021 consisted of a visual assessment of the site and

surrounding area and limited subsurface investigation within the curtilage of the proposed

residence and dispersal area.

All fieldwork was conducted generally in accordance with the methodology outlined in

AS/NZS1547:2012 ‘On-site Domestic Wastewater Management’ and the Environment and

Health Protection Guideline ‘On-site Sewage Management for Single Households’.

4.2 Subsurface Profile

The exposed subsoil profile was typical of the stoney soils of the Binalong Soil Landscape

consisting of:-

Table 3 -Indicative Soil Profile

0 – 100mm Brown LOAM topsoil, moist, well structured.

100 – 300mm Light brown clayey LOAM, moist, trace of roots, moderately structured

300 – 700+mm Yellow brown sandy CLAY, moist, moderately structured.

The above sub-surface profile was anticipated to be representative of the natural sub-

surface soil profile across the proposed wastewater dispersal area. The depth of strata may

be expected to vary across the proposed dispersal area.

Neither groundwater nor surface water were encountered in during the investigation.

4.3 Hydraulic Loading

The hydraulic loading has been estimated using methodology detailed in AS/NZS1547:2012

Table H1. The estimated hydraulic load from the residence using town water is set out in

Table 4, below.


5


Table 4 - Hydraulic loading (future town water)

Residence Maximum Number

People

Hydraulic Loading

per Person

(L/day)

Total Hydraulic

Loading

(L/day)

4 bedrooms 6 persons 120 720

4.4 Design Irrigation Rate

The rate at which the hydraulic load of the treated wastewater can be applied to an area is

the Design Loading Rate (DLR). The Design Loading Rate cannot exceed the Long Term

Acceptance Rate of the soil. The DLR is a function of the soil type, soil permeability, and

other environmental factors such as evaporation and transpiration (if applicable) and ability

for the plants or soil to absorb or bind the nutrients.

Textural assessment of the sandy CLAY subsurface stratum to 500mm below surface level

indicated the following characterisation and recommended DLRs for use in the calculation

of the required dispersal area for surface irrigation for the application of secondary treated

wastewater in accordance with AS/NZS1547:2012 Table 5.2, as shown in Table 5, below.

Table 5– DLR for secondary treated wastewater (ie from an AWTS)

Soil

Category

Soil texture

Structure

Indicative

Permeability (Ksat)(mm/d)

Surface Irrigation

DLR ( mm/d)

5

Sandy Clay

Moderately structured

0.06 – 0.12

3

4.5 Dispersal Area Calculations

The following methods were used to calculate the required dispersal areas for AWTS

treated wastewater. They rely on the Hydraulic Loadings in Table 4 and the Design Loading

Rates in Table 5.

• Nominated Area Method

• Nitrogen Loading Method

• Phosphorus Loading Method

Each method uses different physical and chemical site characteristics to determine the

required wastewater dispersal area. The most suitable dispersal area sizing method will be

determined with consideration to site specific limitations. Typically, the method that

produces the largest area for a particular dispersal mechanism is selected to enable the

most effective on-site dispersal of wastewater. Each of the above methods is described in

Table 6, below.


6


Table 6 – Methodologies Used for Calculating Required Wastewater Dispersal Areas

Method Description

Nominated Area Method

Uses a combination of regional climatic records, design loading rate (ie wastewater volume) and the long-term acceptance rate

to determine, using a water balance, the minimum required surface irrigation dispersal area that will not require wet weather

storage.

Nitrogen Loading Method

Calculations are based upon treated wastewater with a total

nitrogen content of 25mg/L, and an average maximum vegetation uptake rate of 32.9mg/m2/day. The average

maximum uptake rate for the vegetation is based on the ability of the vegetation to use the nutrient before it passes through the

root zone.

Phosphorus Loading Methods

Calculations are based upon treated wastewater with a total phosphorus content of 12mg/L, and an average maximum vegetation uptake rate of 3.3mg/m2/day. The phosphorus absorption capacity of the soil is also used to calculate the

required area with the soil absorption rate based on the ability of the soil to bind the phosphorus and prevent it being washed

through the soil profile (where it can become a source of pollution).

The irrigation areas calculated using the methods in Table 6, are presented as the minimum

required surface irrigation dispersal areas, in Table 7.

Table 7 - Minimum Required Dispersal Area(s) (m2)

Residence

Using tank water

Spray Irrigation or LPED (m2)


Nitrogen (25 mg/l)

Phosphorus (12 mg/l)

6 persons 320 670 460

4.6 Limitations to On-site Wastewater Dispersal

Table 6 of The Environment and Health Protection Guideline On-site Sewage Management for

Single Households and Table K1 of AS/NZS 1547:2012 provide soil assessment rating

systems for on-site wastewater dispersal systems. When the results from the site

investigations and soil analysis are compared with these tables, minor, moderate or major

limitations to the on-site irrigation of treated wastewater on the site can be identified. These

limitations are given in Table 8.


7


Table 8 – Minor, Moderate and Major Limitations to the On-site Dispersal of Treated Wastewater

Soil Feature Limitation

Slope Minor

Depth to bedrock or water table Moderate

Permeability Minor

EAT Minor

pH Minor

Electrical Conductivity (EC) Minor

The dispersal area for the site will not require remedial work to overcome any Major

limitations.

4.6.1 Shallow Depth to Rock

The shallow depth of rock will not adversely impact on the performance of surface spray

irrigation.

4.6.2 Slope Surface spray irrigation should not be applied where slopes exceed 15%.

5 Recommended Treatment and Dispersal Systems

Based on our evaluation of the site and the identified soil profile and site limitations, the site

is suitable for the on-site dispersal of wastewater from an AWTS via surface irrigation over

a minimum area of 670m2,

Examples of suitable AWTS systems include;

• Taylex ABS

• Econocycle ENC10 or ENP10

• Envirocycle NR10

5.1 Surface Spray Irrigation

Treated wastewater may be dispersed via a surface spray irrigation system. It is suggested

that coverage of the required dispersal area be ensured by installing a trunk line across the

proposed dispersal area with several quick release connections being provided along the

trunk line to facilitate management of the irrigation across the dispersal area by the easy

relocation of lateral irrigation lines so that the wastewater is able to be easily irrigated over

the entire design dispersal area. Each lateral irrigation line should incorporate 5 sprinklers.

5.2 Location of Dispersal Area(s)

The suitable wastewater dispersal area and an indicative 1000m2 irrigation area, are shown

on drawing 2180223/EFD1. Sufficient area for a reserve wastewater dispersal area is

available within the suitable surface irrigation area.


8


A reserve wastewater dispersal area is recommended by AS/NZS1547:2012 and should be

of equivalent size to the initial dispersal area(s) noted in Table7. The purpose of the reserve

dispersal area is to rest the initial dispersal area, or for duplication of the dispersal area if

unforeseen circumstances require this at some time in the future. The reserve dispersal

area is not required to be utilised, however, it must be protected from any development that

would prevent its use in the future.

The potential location of the AWTS tank is shown diagrammatically on drawing

218022/EFD1 and may be varied to suit site conditions, owner’s requirements and any

restrictions imposed by Yass Valley Council.

6 Other Considerations

6.1 Buffer Setbacks

The recommended buffer setback distance of the dispersal areas from surface features are

set out in Table 9, below.

Table 9 – Buffer Setback Distance Requirements for Surface Irrigation Dispersal Mechanisms

Feature Buffer Distance

(All distances in metres)

Where Dispersal Area is

Upslope

Where Dispersal Area is

Beside or Downslope

Dwelling 15 15

Driveway 6 3

Intermittent Drainage Line 40 -

Farm dam 40 -

Domestic Groundwater Bore 250 250

Property Boundary 6 3

Permanent waterway/creek 100 -

Potentially applicable buffer situations have been shown in Bold.

Yass Valley Council may relax or impose additional buffer or set back restrictions. Refer to

any conditions of approval for possible additional requirements, restrictions or guidelines.

6.2 Vegetation

The wastewater dispersal area(s) must be vegetated. The existing vegetation across the

suitable irrigation area is adequate and should be maintained. Vegetation should be

regularly mowed and pruned to maintain the rate of evapotranspiration.

6.3 Wastewater Quality

It is important that the occupant makes a consistent effort to reduce the strength of the

treated wastewater.


9


Methods to reduce wastewater strength include:

i. Using the minimum recommended amounts of low phosphate, biodegradable

liquid detergents and cleaning agents;

ii. Avoiding large quantities of bleaches, disinfectants and whiteners;

iii. Minimising the amount of solid waste entering the septic system, especially non-

biodegradable items such as plastics.

6.4 AWTS and Dispersal System Maintenance

The proposed wastewater treatment system and the installed dispersal mechanism and area

should be regularly checked to ensure that they are operating correctly.

Most AWTS systems require to be serviced on a quarterly basis.

Signs of failure include surface ponding, wastewater runoff, erosion, leaching of the soil, poor

vegetation growth including burnt vegetation, odours or the formation of surface crusts.

7 Report Limitations and Site Variations

The extent of testing associated with this assessment is limited to the activities referenced

in the report and variations in ground conditions may occur. 5QS Consulting Group should

be contacted immediately should subsurface conditions be found to differ from those

described in this report.

This On-Site Wastewater Management Assessment was not an investigation of the specific

subsurface profile at the location and is not intended to provide any comment on the

potential excavatability of the subsurface material.

For and on behalf of

5QS Consulting Group

Rob Barker FIE Aust CPEng NER (Civil/Structural)

Attachments

1. Drawing 218022/EFD1

2. Site and Soil Evaluation

3. Dispersal Area Calculation Sheets

5QS Ref:Date:Assessor:

720 L/d L/wk

Climate: Climate Data Source:

mm

mm

Topography:

Groundwater:

m

500 mg/kg 0.00 0.0

dS/m 0.00% 0.0g/cm3 0.0 meq/100g 0.0

YESYES

Onsite Effluent Dispersal Assesment

SITE AND SOIL EVALUATION

Julian & Amy Budgeon25 Blue Hills Lane, Jeir0

21802212-May-21

mid slopePlanar

1273

672.4

Site Information and Assessment

Rob Barker

The following is a Site and Soil Evaluation summary in accordance with AS 1547-2012 "On-site Domestic Wastewater Management" and the Environment & Health Protection Guidelines "On Site Sewerage Management for Single Households"

5040Wastewater Load:

Rainfall:Design Percentile: 50

Yass Valley Region Synthetic Record

Yass Valley Region Synthetic Record

Site Slope:Site Exposure:

Is there sufficient Land Area for Reserve Dispersal:Is there sufficient Land for a Primary Dispersal Area:

Phosphorous Sorption:Emerson Aggregate Test:Electrical Conductivity: 0.07

Dispersal Area

Soil Permeability Category:

6.0

0.0Bulk Density:ESP:

Soil Analysis on Sample BH1 - 100 to 350mm

meq/100g

pH:

Aluminium:

meq/100gmeq/100gmeq/100g

Cation Exchange Capacity:

Sodium:Magnesium:Potassium:3 - 6 (3)

Site Aspect:Site Drainage:

Owner:Site Location:Client:

Site Landform:Landform Shape:Erosion Potential:Surface Rocks:

Intended Water Supply: Tank Water

Annual Rainfall:

Annual Evaporation: Evaporation:

3 - 10%GoodNorth westModerately drained

Lowsome visibleNone within the proposed dispersal area

Soil Texture:

0.06 - 0.12 (Ksat)(m/d)

mm/d

DLR - Trenches (Secondary): 10 mm/d

Soil Assessment

mN/ADepth to bedrock or hardpan: Depth to high soil watertable:

mm/d

mm/d

32.5

5

Run-on and Seepage: Site Filling:some expected

Calcium

DLR - Irrigation:DLR - Trenches (Primary):

DLR - Mound:

Moderately Structuredsandy Clay5

Indicative Permeability:

Groundwater bores in the area and their current purpose:Horizontal distance to groundwater well used for domestic supply:Groundwater vulnerability:

Domestic Stock~300m northNot within GW vulnerability Area

0.5 - 0.9m

Soil Structure:

720 L/d5040 L/wk

0.25 0.7

Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec

31.0 28.0 31.0 30.0 31.0 30.0 31.0 31.0 30.0 31.0 30.0 31.0

50.5 46.1 45.9 38.7 54.0 60.0 64.2 67.5 63.2 62.5 67.4 52.4

220.0 156.0 130.0 76.0 48.0 33.0 35.0 51.0 75.0 114.0 147.0 188.0


37.9 34.5 34.4 29.1 40.5 45.0 48.2 50.7 47.4 46.9 50.6 39.3

69.8 63.0 69.8 67.5 69.8 67.5 69.8 69.8 67.5 69.8 67.5 69.8

107.6 97.5 104.2 96.6 110.3 112.5 117.9 120.4 114.9 116.6 118.1 109.1


154.0 109.2 91.0 53.2 33.6 23.1 24.5 35.7 52.5 79.8 102.9 131.6

93.0 84.0 93.0 90.0 93.0 90.0 93.0 93.0 90.0 93.0 90.0 93.0

247.0 193.2 184.0 143.2 126.6 113.1 117.5 128.7 142.5 172.8 192.9 224.6


-139.4 -95.7 -79.8 -46.7 -16.3 -0.6 0.4 -8.3 -27.6 -56.2 -74.8 -115.6

0.0 0.0 0.0 0.0 0.0 0.0 0.4 0.0 0.0 0.0 0.0 0.0

m2

m3



The following Nominated Area Method Calculation is a water balance which determines the wet weather storage requirement based on a nominated irrigation area.

Storage (mm/month)

Cumulative Storage (mm)

Date:Assessor:

21802212-May-21Rob Barker

Water Storage

Water Inflows (mm/month)

Water outflows (mm/month)

Evapotranspiration

Percolation

Total Water Outputs

Precipitation

Effluent Irrigation

Total Water Inputs

Calculation

Days in Month

Precipitation (mm)

Evaporation (mm)

Tank WaterIntended Water Supply:Design Loading Rate (Irrigation):

Crop Factor:

Wastewater Load (Qd):

Site Location:Client:

Owner: 5QS Ref:

1273.0

Total

365.0

672.4

Climate Data

21 mm/wk

Site Information and Assessment

Julian & Amy Budgeon25 Blue Hills Lane, Jeir

0

Wastewater Load (Qw):Rainfall runoff coefficient

0.1

320Required Wet Weather Storage:

Calculation Results

Total Irrigation Area:

Total

504.3

821.3

1325.6

Total

891.1

1095.0

1986.1

5QS Ref:Date:Assessor:

720 L/d5040 L/wk

includes 20% reduction for denitrificationPerennial pasture

Total Phosphorous Concentration (TPC): mg/LWastewater Load (Qd): L/d

Phosphorus produced:

Phosphorus sorption capacity of the soil:

=

= m2

The Nitrogen Loading Method Calculations are based upon treated effluent with a total nitrogen figure of 25 mg/L, and a maximum vegetation take up rate (Critical loading rate) of 27.1 mg/m²/day.

Phosphorus applied to Dispersal Area over 50 Years

12

Total Nitrogen Concentration (TNC):Critical Loading Rate (LR):

Irrigation Area =

= 664

2527.10

Phosphorous Loading Method

Phosphorus Applied to Dispersal Area

The Phophorous Loading Method Calculations are based upon treated effluent with a Total Phosphorus Content of 12 mg/L, and an average maximum soil absoption rate (Sorption Capacity) of 500 mg/kg, and a plant take up rate (Phosphorous Uptake) of 3 mg/m²/day.

The average maximum take up rate for the soil is based on the ability of the soil to bind the phosphorus and prevent it being washed through the soil profile.

720

0.343

Dispersal Area =

Phosphorus Removed over 50 Years:

459

mg/m2/day

mg/m2 (over 50 years)

kg/m2 (over 50 years)

3

54750

0.055

0.343 kg/m2 (over 50 years)

Dispersal Area Required

kg

kg/m2

Phosphorus Applied kg

Phosphorus Removed kg/m2

157.7

kg (over 50 years)

Phosphorus Uptake by Plants

157.7

Phosphorus Removed = Phosphorus Absorbed by Soil + Used by Plants over 50 Years

Phosphorus uptake:

mg/kgkg/Ha (over 50 years)

kg/m2 (over 50 years)

Phosphorus Adsorbed by Soil5002885

0.288

Owner:


Nitrogen/Phosphorous Loading Method

Julian & Amy Budgeon 218022Site Location:

m2

Nitrogen Loading Method

12-May-21Client: Rob Barker

mg/Lmg/m2/day

Site Information

Intended Water Supply: Tank Water

(TNC x Qd)/LR

25 Blue Hills Lane, Jeir0

Wastewater Load (Qd):Wastewater Load (Qw):

Documents

Re: On-site Wastewater Management Assessment Lot 7, DP