ACT Geotechnical Engineers Pty Ltd 5/9 Beaconsfield St, Fyshwick, ACT, 2600

ACN 063 673 530 PO Box 9225, Deakin, ACT, 2609Ph: (02) 6285 1547

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24 September 2020Our ref: KA/C11049

Tracey EwensVia email: tracey.ewens@gmail.com

ian@swanbuild.com.au

Attention: Tracey Ewens

PROPOSED RESIDENCE11 KINSMAN DRIVE, MURRUMBATEMAN, NSW

EFFLUENT DISPOSAL REPORT – SITE AND SOIL EVALUATION

1 Introduction

At the request of Tracey Ewens, ACT Geotechnical Engineers Pty. Ltd carried out an effluent disposalassessment to AS1547 “On-Site domestic wastewater management”, for a proposed residence at 11 KinsmanDrive, in Murrumbateman, NSW.

It is understood that the new dwelling will have two potential bedrooms, in addition to the one bedroomexisting residence. The lot is legally described as Lot 24 of DP258364. The lot is currently vacant and will be thesite for a new residence. The rectangular shaped lot is approximately 8230 m2 in area. The lot is relatively flatand slopes very gently to the south-west, towards the road.

This Site and Soil Evaluation was conducted in general accordance with AS 1547:2012 - “On-site domesticwastewater management”, “Designing and Installing On-Site Wastewater Systems: A WaterNSW CurrentRecommended Practice: 2019”, and “The Environment & Protection Guidelines 1998 – On-Site SewageManagement for Single Households” (Silver Book).

The site details and assumptions made to assess the requirements of the effluent disposal system are outlined inTable 1 below.

The details of the site and proposed works are summarized in Table 1 below.

TABLE 1 – SITE DETAILS

Area of Lot ~8230 m2

Number of Potential Bedrooms 3

Design Flowrate 600L/day (as per “Designing and Installing On-siteWastewater Systems – WaterNSW”)

Rainfall Station 070344 – Murrumbateman (McIntosh Circuit)

Evaporation Station 070351 – Canberra Airport

2 Effluent Disposal Site Assessment

The proposed site for the effluent disposal system was assessed and the site limitation assessment is addressed

below.

The 1:100,000 Gunning Geology Map documents the area to be underlain by Silurian age Hawkins Volcanics,

comprising residual eluvial saprolite deposits overlying blue-grey biotite and rhyolitic to dacitic ignimbrite.

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2.1 Site Limitation Assessment

Table 2 below is a site assessment of the proposed effluent disposal system, and has been assessed using Table

1 from “On-site Sewage Management for Single Households”. The table used for this assessment is attached to

this report.

TABLE 2 – SITE ASSESSMENT

Site Limitation Assessment

Climate Average rainfall for the Murrumbateman

area is ~726mm per year. The average

monthly rainfall for summer is ~56mm and

~64mm for winter. Average monthly

evapotranspiration for summer is ~175mm

and ~42mm for winter.

The climate in the area is suitable for

disposal of effluent using surface irrigation.

Flood Potential Above 1:20 year flood;

Above 1:100 year flood.

Flood potential is not a limitation.

Slope of Land Slopes <5% southwest <10% (surface and sub-surface irrigation) –

minor constraint

Exposure -

Vegetation (grass,

trees, etc.)

No shelter from topographical features or

existing vegetation.

Site is suitable

Landform Linear planar slope - the disposal site is

downslope from the residence.

Minor Constraint – Site is suitable

Run-on & upslope

seepage

The disposal site is down-gradient from

the proposed residence.

Minor Constraint- Site is suitable

Erosion Potential No signs of erosion potential present Minor Constraint – Site is suitable

Site Drainage No visible signs of surface dampness Minor Constraint – Site is suitable

Soil Disturbance

(Fill)

No fill was present in the area of the site Minor Constraint – site is suitable

Buffer Distance Section 2.3 addresses buffer distances

Land Area Area is available with required buffer

distances (assuming council approval was

given for the current system)

Site is suitable

Rocky Outcrops No rocky outcrops in the area Site is suitable

Groundwater and

Surface Waters

Two groundwater wells within 150m of the

proposed application area:

GW416406 – 75m away

GW416395 – 125m away

Site is suitable – assuming council

approval was given for the current system

3ACT Geotechnical Engineers Pty Ltd

2.2 Subsurface Conditions

To establish the subsurface conditions, one test hole (BH2) was drilled near the proposed land applicationarea. Figure 1 shows the site locality, while Figure 2 is a site plan showing the location of the investigationborehole. The subsurface profile was logged in terms of the Unified Soil Classification System (USCS).

Geological Profile Typical DepthInterval

Description

TOPSOIL 0.0m to 0.15m Silty SAND; fine to medium grained sand, low plasticity silt, darkbrown, dry, with grass rootlets, loose.

ALLUVIUM 0.2m to 0.6m Clayey SAND, Sandy CLAY; fine to coarse sand, low to mediumplasticity clay, brown, orange-brown, dry to moist, loose tomedium dense, stiff.

RESIDUAL 0.6m to 0.8m Clayey SAND and Sandy CLAY; medium plasticity clay, fine tocoarse sand, orange-brown, some grey-brown, trace ferruginousnodules up to 5mm, dry to moist.

EXTREMELYWEATHERED ROCK

0.8m to >1.0m Extremely Weathered (EW) Sandstone; excavates as ClayeySAND; fine to coarse sand, low plasticity clay, some fine gravel,orange-brown, dry, very dense.

Based on the soil encountered and in accordance with AS1547:2012 – “Disposal Systems for Effluent From

Domestic Premises” (Reference 2), the properties of the most limiting material are summarised in Table 2

below.

TABLE 3 – SITE SOIL PROPERTIES

Soil Category 4 – Clay Loams Minor limitation

Depth of Soil Layer 0.8m Moderate Limitation

Depth to high episodic/seasonal

watertable

>1m Minor limitation, groundwater

is not expected within >1m

Soil Structure Weakly Structured Minor Limitation, moderate

permeability

Bulk Density 1.5g/cm3 <1.8g/cm3 Minor Limitation

Phosphorous Sorption Capacity 7,200kg/ha Minor Limitation – more than

6000kg/ha

Indicative Permeability 0.12 – 0.5m/day -

Design Irrigation Rate (DIR) 3.5mm/day -

Design Loading Rate (DLR) - -

Coarse Fragments <20% Minor Limitation

pH 7.23 – Topsoil

7.10 – Residual

Minor limitation

Electrical Conductivity ECe dS/m 0.311 – Topsoil

0.111 – Residual

Minor limitation

Modified Emerson Aggregate Test Class 2 Moderate Limitation

Given the moderate expected permeability of the weakly structured clay loams present at the irrigation area,

a Design Irrigation Rate (DIR) of 3.5mm/day has been adopted.

2.3 Siting of Disposal Areas

Different minimum buffer distances are required for different features on the site, as per AS1547:2012 ‘On-site

Domestic Wastewater Management’. These have been assessed on site and are summarized in Table 4 below.

Figure 3 shows the buffer distances for the effluent disposal system.

4ACT Geotechnical Engineers Pty Ltd

TABLE 4 – BUFFER DISTANCES

Site Constraint Minimum Required

Buffer Distance

Priority Proposed System Buffer

Distance

Permanent Surface Waters (river, creek, lake,

etc.)

100m Low >100m

Domestic groundwater well or bore. 100m High >75m (suitable –

assuming council

approval was given for

previous system)

Other waters (farm dam, intermittent creeks,

drainage channels, etc.)

40m Low >100m

Property Boundaries 12m (uphill)

6m (downhill)

Low >12m

Dwellings, swimming pools & driveways 6m (uphill)

3m (downhill)

Low >3m

2.4 Effluent Disposal System Selection

The current surface irrigation system is still suitable but the application area will need to be moved and

expanded to make way for the new residence.

3 Effluent Disposal System Design

The calculations in determining the size for the application area are outlined below. Using Table H1 in

AS1547:2012 – “Disposal Systems for Effluent From Domestic Premises”, the daily flow was calculated using the

assumptions outlined in Table 1.

Water Balance: A = Q (L/day)/DIR (mm/day);

Where Q = 600L/day

DIR = 3.5mm/day

A = 600/3.5 = 172m2

Nitrogen Balance: A = Q(L/day) x TN (mg/L)/ Ln (critical loading of TN, mg/m2/day)Where Q = 600L/dayTN = 25mg/L

Assume 20% loss by denitrification; 25mg/L – (25 x 0.2) = 20mg/LLn – 15,000mg/m2/year (150kg/ha/year, for imported species)A = 600 x 20 x 365/15,000 = 292m2

Phosphorous Balance: A = P gen/(P uptake + P sorb) [P sorption capacity in upper 50cm & 50 year design period]P sorption capacity in upper 50cmP sorb = 7,200kg/ha = 0.72kg/m2

P uptake for design period of 50 years

P uptake = 4mg/m2/day x 365 x 50 = 0.073kg/m2

P generated over 50 year design period

P gen = 8mg/l x 600 x 365 x 50 = 87.6kg

A = P gen/(P uptake + P sorb) = 131.4/(0.073 + 0.72) = 110m2

The sizing of the irrigation area should be designed to take into account the nitrogen and phosphorousbalance and an area of 292m2 should be allowed for.

5ACT Geotechnical Engineers Pty Ltd

3.1 Treatment System

For surface/spray irrigation, the effluent must be secondary treated effluent, which can be treated in a NSWHealth accredited AWTS system (like the current Super Treat system) and should be installed as per thePlumber’s installation manual. The system shall have adequate capacity to treat the design flow rate(600L/day) for the combined three bedroom lot. The tank should be installed to comply with the local councilrequirements and the standard AS3500.2:2003 – “Plumbing and Drainage Part 2 Sanitary Plumbing andDrainage”, and the manufacturer’s recommendations.

The tanks should be installed so that the lid of the tank is exposed at least 100mm off the ground surface levelto ensure that no stormwater enters the tank.

3.2 Designated Area

A spray irrigation system for the site requires a minimum application area of 292m2. The spray irrigation system

shall be constructed in accordance with the requirements of AS1547:2012 Appendix M.

The area will need to be covered with at least 100mm of fertile topsoil to act as an immediate storage media

for effluent applied to it, and to support the rapid growth of suitable vegetation to maximize evapo-

transpiration. A list of suitable plants is provided in “The Easy Septic Guide” produced by the NSW Department

of Local Government. Multiple irrigation areas may need to be constructed, to allow spray cycling between

the areas.

The slope of the block is a minor constraint for surface spray irrigation systems. The soils have moderate

permeability and spray irrigation is suitable for the site provided it is sited on land with a slope of less than 20%

and outside the required buffer distances.

In the case of system failure, a reserve area is required of the same size of 292m2. This is highlighted in Figure 2

attached.

A fence should be placed around the effluent disposal area if there is a risk of children, animals or vehiclescoming into the area. Signage, complying with AS1319 shall be placed in at least two places at the boundaryof the application area, clearly visible to property uses, with wording such as “Recycled Water – AvoidContact – DO NOT DRINK”.

The treated effluent is not suitable for vegetable gardens or areas where people can come in contact withthe effluent.

The area should not be used for any purposes that compromise the effectiveness of the system or access forfuture maintenance purposes.

Should you require any further information regarding this report, please do not hesitate to contact our office.

Yours faithfullyACT Geotechnical Engineers Pty. Ltd.

Jeremy MurrayDirectorSenior Geotechnical EngineerAttachments: - Figures 1 and 2, Borehole Log

TRACEY EWENSPROPOSED RESIDENCE

11 KINSMAN DRIVE, MURRUMBATEMAN, NSWBUFFER DISTANCES IN RELATION TO GROUNDWATER

ACT Geotechnical Engineers Pty Ltd C11049 FIGURE 1

Farm dam 185m away

Application Area (approx.)

N

Proposed Residence(approx.)

Farm dam 150m away

Farm dam 175m away

100m radius fromGW416395

100m radius fromGW416406

TRACEY EWENSPROPOSED RESIDENCE

11 KINSMAN DRIVE, MURRUMBATEMAN, NSWSITE PLAN

ACT Geotechnical Engineers Pty Ltd C11049 FIGURE 2

N

LEGEND

- - Location of Test Hole

BH1

NOTE: appropriate warning signagecomplying with AS1547:2012

Appendix M and AS1319 must beplaced in at least two places around

the Application Area

Reserve Area(292m2)

Application Area(292m2)

TRACEY EWENSPROPOSED RESIDENCE

11 KINSMAN DRIVE, MURRUMBATEMAN, NSWEXAMPLE LAYOUT OF SPRAY IRRIGATION SYSTEM

ACT Geotechnical Engineers Pty Ltd C11049 FIGURE 3

Silty SAND; fine to medium grained sand, low plasticity silt, dark brown, dry, withgrass rootlets.

Clayey SAND; fine to coarse sand, low plasticity clay, brown, orange-brown, dryto moist.

Sandy CLAY; medium plasticity clay, fine to coarse sand, red-brown,orange-brown, moist (less than plastic limit).

Clayey SAND and Sandy CLAY; medium plasticity clay, fine to coarse sand,orange-brown, some grey-brown, trace ferruginous nodules up to 5mm, dry tomoist.

Extremely Weathered (EW) Sandstone; excavates as Clayey SAND; fine tocoarse sand, low plasticity clay, some fine gravel, orange-brown, dry.

BOREHOLE TERMINATED AT 1mrefusal

LOOSE

LOOSETOMEDIUMDENSE

STIFF

STIFF TOVERYSTIFF

VERYDENSE

SM

SC

CH

SC

SC

TOPSOIL

ALLUVIUM

RESIDUAL

EXTREMELYWEATHEREDROCK

0.15

0.35

0.6

0.8

1

Soil Type: Plasticity or Particle Characteristics,Colour, Secondary and Minor Components,Moisture, Structure

1.2

BH1

FieldTest

Results

Borehole No.

Sheet

Con

sist

ency

orR

elat

ive

Den

sity

Collar Level : Not KnownAngle From Vertical : 0°Bearing : N.A.

Cas

ing

U.S

.C.S

.

GeologicalProfile

1 of 1

Gra

phic

Log

Dep

th

1.0

Dep

th

1.0

Sam

ples

Borehole Log

Equipment Type : PUSH TUBE DRILLHole Diameter : 50mm

Metres

Material Description, Structure

C11049Job No.

CLIENT: TRACEY EWENS

Logged By : KA

Location : SEE REPORT

Date : 16/9/20 Checked By : JM Date : 16/9/20

PROPOSED RESIDENCE11 KINSMAN DRIVE, MURRUMBATEMAN, NSW

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ACT Geotechnical Engineers Pty Lt 5/9 Beaconsfield Street, Fyshwick ACT 2609

ACN 063 673 530 PO Box 9225, Deakin ACT 2600

Ph: (02) 6285 1547

ACT Geotechnical Engineers Pty Ltd

Limitations in the Use and Interpretation

of this Geotechnical Report

Our Professional services were performed, our findings obtained, and our recommendations

prepared in accordance with generally accepted engineering principles and practices. This

warranty is in lieu of all other warranties, either expressed or implied.

The geotechnical report was prepared for the use of the Owner in the design of the subject

development and should be made available to potential contractors and/or the Contractor for

information on factual data only. This report should not be used for contractual purposes as a

warranty of interpreted subsurface conditions such as those indicated by the interpretive

borehole and test pit logs, cross- sections, or discussion of subsurface conditions contained herein.

The analyses, conclusions and recommendations contained in the report are based on site

conditions as they presently exist and assume that the exploratory bore holes, test pits, and/or

probes are representative of the subsurface conditions of the site. If, during construction,

subsurface conditions are found which are significantly different from those observed in the

exploratory bore holes and test pits, or assumed to exist in the excavations, we should be advised

at once so that we can review these conditions and reconsider our recommendations where

necessary. If there is a substantial lapse of time between conducting this investigation and the

start of work at the site, or if conditions have changed due to natural causes or construction

operations at or adjacent to the site, this report should be reviewed to determine the applicability

of the conclusions and the recommendations considering the changed conditions and time

lapse.

The summary bore hole and test pit logs are our opinion of the subsurface conditions revealed by

periodic sampling of the ground as the test holes progressed. The soil descriptions and interfaces

between strata are interpretive and actual changes may be gradual.

The bore hole and test pit logs and related information depict subsurface conditions only at the

specific locations and at the particular time designated on the logs. Soil conditions at the other

locations may differ from conditions occurring at these bore hole and test pit locations. Also, the

passage of time may result in a change in the soil conditions at these test locations.

Groundwater levels often vary seasonally. Groundwater levels reported on the boring logs or in

the body of the report are factual data only for the dates shown.

Unanticipated soil conditions are commonly encountered on construction sites and cannot be

fully anticipated by merely taking soil samples, bore holes or test pits. Such unexpected conditions

frequently require that additional expenditures be made to attain a properly constructed project.

It is recommended that the Owner consider providing a contingency fund to accommodate

such potential extra costs.

This firm cannot be responsible for any deviation from the intent of this report including, but not

restricted to, any changes to the scheduled time of construction, the nature of the project or the

specific construction methods or means indicated in this report: nor can our company be

responsible for any construction activity on sites other than the specific site referred to in this

report.