Words, maps, and photographs which might identify the site …...The property covers about a hectare, is mainly cleared to gardens, lawns and native grasses, and is mostly flat, with

William C. Cromer Pty. Ltd. – 74A Channel Highway Ta roona, Tasmania 7053 Australia Mob. 0408 122 127 – Fax 03 6227 9456 – www.billcrom er.com.au – email [email protected]

UPGRADE OF EXISTING WASTEWATER SYSTEM 9 RICHARDSONS ROAD

SANDFORD

SITE AND SOIL EVALUATION REPORT

AND SYSTEM DESIGN FOR

WASTEWATER MANAGEMENT In general accordance with AS/NZS 1547 (2000) On-site domestic-wastewater management,

and supported by Trench®3.0

Municipality Client Location Development Upgrade of existing wastewater system Date of inspection

WILLIAM C. CROMER PTY. LTD. ACN 009 531 613 ABN 48 009 531 613

ENVIRONMENTAL, ENGINEERING AND GROUNDWATER GEOLOGISTS C C W

Words, maps, and photographs which might identify the site of this report have been deleted

CLIENT AND ADDRESS

Site and Soil Evaluation for domestic wastewater management DATE

William C. Cromer Pty. Ltd. – 74A Channel Highway Taroona, Tasmania 7053 Australia email [email protected]

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Refer to this report as Cromer, W. C. (date). Site and Soil Evaluation Report, and System Design for Wastewater Management, proposed upgrade of existing wastewater system. (Unpublished report for (client) by William C. Cromer Pty. Ltd.). William C Cromer Pty Ltd may submit hard or electro nic copies of this report to Mineral Resources Tasmania to enhance the geotechnical data base of Tasmania. Important Note Permission is hereby given by William C. Cromer as author, and the client, for this report to be copied and distributed to interested parties, but only if it is reproduced in colour, and only distributed in full. No responsibility is otherwise taken for the contents.

IMPORTANT

APPOINTMENT OF DESIGNER A completed Form 59 separately accompanies this report and appoints William C Cromer Pty Ltd as the designer of the system described here. The designer is required to make as many site inspections as is necessary to be able to certify to Council and the client that

the system conforms with the approved design

the system, as installed, conforms with AS/NZS 1547:2000, and

the dwelling constructed or being constructed has the required level of water saving fixtures installed Certification is required before the dwelling can be occupied and the wastewater disposal system used.

INSPECTION ARRANGEMENTS It is the responsibility of the client or the client’s agent to contact the designer before construction starts on the wastewater disposal system, in order to establish the stages of construction required to be inspected by the designer. The designer will also be required to inspect water saving fixtures (if any) he has specified for the dwelling. Depending on the relative stages of construction of the disposal system and dwelling, this may necessitate a separate inspection.

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SUMMARY

The existing wastewater system for the 5-bedroom equivalent house and unit at 9 Richardsons Road comprises two septic tanks and two 23m x 1m x 0.7m deep absorption trenches. The tanks and trenches are undersized for the assumed wastewater loading. Au upgrade is proposed, with an additional Primary Disposal Area (PDA) and new 4,000L septic tank. Rain water tanks are used. Standard water saving fixtures are specified. A total daily wastewater volume of 1,150L has been adopted. The existing trenches in PDA#1 can accept about a third of this volume. At PDA#2, soils are Category 4 fine sands averaging 0.8m thick. A Design Loading Rate of 12mm/day has been adopted. For a daily wastewater volume of about 800L, a wetted area of at least 70m2 is required. This is readily available, as is a secondary area. Disposal in a conventional bed is recommended. Design details are provided. A setback of 5m is recommended to downgradient sensitive features.

1 BACKGROUND In a letter to A. Sheehan and B. Wilson dated 2 August 2012, Clarence City Council requested a report from an environmental consultant which, in relation to 9 Richardsons Road, Sandford (Attachment 1), should include: a description of the existing wastewater system, whether it was adequate for recent building additions, and if not, what upgrades or modifications would be appropriate. The current report addresses these issues (which constitute the first dot point of Council’s letter).

2 EXISTING WASTEWATER SYSTEM 2.1 Description The existing wastewater system is described in Attachment 2, and parts of it are shown in Plates 1 and 2 in Attachment 4. It serves a four-bedroom equivalent house and adjoining one-bedroom unit, both of which are on rainwater tanks. Its components are a concrete, dual purpose 2,350L septic tank for the house a concrete, dual purpose 2,000L (or thereabouts1) septic tank for the unit, a 500L (or thereabouts) pit with float-operated submersible pump which receives gravity flow from both septic tanks, and two absorption-evapotranspiration beds, each 23m long, 1m wide and approximately 0.7mm deep, with plastic arches and gravel backfill. In this report, the rectangular area of about 25m x 7m enclosing the two trenches is called Primary Disposal Area 1 (PDA#1; see Attachment 3). 2.2 Adequacy of the existing system As shown later in this report, PDA#1 is located in light coloured fine-grained, medium dense sandy soils to depths of around 0.7m. The sand overlies orange brown clayey sand, sandy clay and clay. Ordinarily, the site would be classified as Category 5 (locally Category 6) but the sand 1 This septic tank could not be inspected, as a near ground-level timber deck covered it.

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permits lateral adsorption of wastewater and the overall result is better described as Category 4 with a Design Loading Rate of about 8mm/day. The trenches nominally provide about 45m2 of wetted area, adequate for the disposal of about 360L/day of wastewater – about 1.5 bedrooms on standard water saving fixtures, or about a third of the total. On this basis, the existing system is undersized for the 5-bedroom equivalent house and unit. Additional wetted area is required. Also, the existing 2,350L septic tank for the house is undersized (3,500L is required for 4 bedrooms), the existing 2,000L (or thereabouts) septic tank for the unit is undersized (the minimum size for a dual purpose septic tank is 3,000L), and the septic tank for the unit should not be covered with a near ground level timber deck The balance of this report comprises a Site and Soil Evaluation of part of the property south west of PDA#1 (the new site has thicker soils and no groundwater), and a recommended system design for the additional wetted area requirements in what is called PDA#2.

3 SITE AND SOIL EVALUATION 3.1 Topography, drainage and vegetation The property covers about a hectare, is mainly cleared to gardens, lawns and native grasses, and is mostly flat, with maximum slope angles to the east less than about 20 east (Attachment 3) 3.2 Land use Rural residential 3.3 Water and power supply Rain water tanks. Electrical power available. 3.4 Assumed daily wastewater Five bedroom equivalent (house and unit); standard water saving fixtures; 115L/day/person; total 1,150L/day. 3.5 Geology and soils The property is underlain by Quaternary-age sediments including sand, clayey sand, sandy clay and clay (Attachments 1, 3 and 4). Soils comprise uniform profiles of: 0 – 0.3m SAND (SP): dark grey; fine grained; loose to medium dense 0.3+ – nom. 0.5 to 1.1m As above; light grey; medium dense In 17 auger holes, the thickness of sand ranged from 0.4 to 1.1m (average near PDA#2 in Attachment 3 was 0.8m) 3.6 Soil selected for wastewater disposal

Texture SAND: AS/NZS1547:2000 Soil Category 4

Thickness Range near PDA#2 is 0.6 – 1.2m (average is 0.8m)

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Modified Emerson Test Not done. Soils are not dispersive. Measured and adopted soil permeability Permeability measured in two holes D and E in Attachment 3 was 0.15 and 0.2m/day; 0.2m/day adopted. Long Term Acceptance Rate (LTAR) Calculated at 16L/m2/day based on adopted permeability, and Trench®3.02. Design Loading Rate (DLR) Adopted as 12mm/day (Category 4 soils) and a full water balance conducted, in accordance with AS/NZS1547:2000 and using Trench3.0.

3.7 Groundwater Expected at depths of 1 – 2m; water in some auger holes is interpreted as mainly originally wastewater moving laterally from existing trenches. 3.8 Site capability issues for on-site wastewater m anagement The Trench3.0 Site Capability Report (Attachment 4) flags no sensitive issues.. 3.9 Environmental Sensitivity issues for on-site wa stewater management The Trench3.0 Environmental Sensitivity Report (Attachment 5) flags two sensitive issues. Default rankings of High or Very High for these factors have either been left unchanged, or have been amended for this site, for the reasons summarised in Table 1. Table 1. Environmental Sensitivity issues

Factor Trench ®3.0

default rank

Amended rank for this

site Reason for amendment

Cation exchange capacity

Very high Moderate Not an issue. Soils are clay free.

Phosphorus Adsorption Capacity

High Moderate Adequate P sorption and attenuation expected within the property boundaries

3.10 Existing wastewater management system See Section 2.

2 See Cromer, W. C. (1999). TrenchTM3.0: An AIEH computer software application for managing on-site wastewater disposal. Environmental Health Review, May 1999, pp 23-25, and Cromer, W. C. (1999). TrenchTM3.0: A computer application for site assessment and system sizing, in Patterson, R. A. (Ed.) On-site ’99 – Proceedings of the On-Site ’99 Conference: Making on-site wastewater systems work. Univ. of New England, Armidale, 13-15 Jul 1999, pp 85-88.

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4 IMPLICATIONS FOR WASTEWATER MANAGEMENT There are no significant environmental issues that cannot be adequately addressed in the disposal of wastewater on the property. The suggested minimum wetted area requirement for the disposal of an adopted 1,150L/day of primary treated wastewater into Category 4 soils is as follows: one third of the wastewater to be directed to PDA#1, and two thirds of wastewater to be directed to PDA#2 The division is to be accomplished by gate valves in the discharge line from the pump. The recommended setback distance to downgradient sensitive features (ie property boundaries) is 5m.

5 SUMMARY OF ASSUMPTIONS It is emphasised to regulatory authorities, designers, installers and owners of on-site wastewater systems that the three pages of the Trench3.0 computer assessment attached to this report summarise the site and environmental factors relevant to the sizing and location of an on-site wastewater disposal system for this site or sites. Other assumptions are listed in the text of this report.

System performance may be affected by site, operational or climatic factors which differ from those assumed.

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6 SYSTEM DESIGN One acceptable disposal system for wastewater management for the house and unit is summarised below. Approval for the chosen design rests with local council. System designs other than the following suggestion may also be environmentally acceptable. Option 1 Wastewater to existing trenches in PDA#1; and to one or more

conventional beds in PDA#2 (latter described here) Method Standard conventional (in-ground) bed Septic tank Upgrade existing two tanks to provide 4,000L in total Lint filter Not required Grease trap Not essential, but recommended in kitchen line from house and unit; min

40L in each case Pump and pit Existing. Plumber to check existing duty is adequate for PDA#1 and

PDA32 operating together. In-ground details Wetted Area (PDA#2) Min. 70m2 Standard water saving fixtures are assumed in the house and unit. Standard fixtures are ticked below: Reduced flush 3/6L or similar toilet cistern Low flow shower head Aerator taps Low water use washing machine (eg front-loading machine) Flow/pressure control valves on all water-use outlets Primary Disposal Area With no requirement for a protective perimeter, this is the same as the

wetted area (70m2). Second. Disposal Area Available if required. Cut-off drain(s) Not required. Setback(s) 5m to downgradient sensitive features. See Attachment 3. Notes See below.

7 GENERAL NOTES Depending on the type of wastewater disposal system installed, owners may be required by Council to satisfy all or some of the following, which would usually form a set of conditions of approval for a Special Plumbing Permit. 1. The system shall comply with AS/NZS1547:2000. 2. All tank and system openings shall be accessible at finished surface level for inspection and servicing, and adequately sealed to prevent stormwater infiltration. 3. Where pumps are fitted and power is required for system operation, a hard-wired audible and visible (indicator light) alarm shall be installed to warn of pump failure, blower failure and power failure. 4. Where an existing disposal system is being added to or altered and the existing septic tank is going to be used, a filter will need to be retro-fitted to the existing septic tank. Owners will need to advise their plumber to ensure that this matter is taken into consideration when purchasing a new septic tank or where the filter is to be retro-fitted. 5. The minimum wetted area requirement for wastewater disposal must be installed and maintained in the approved locations as per the design by the Designer and lodged with the application for a Special Plumbing Permit.

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√ √ √ X

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6. All wastewater disposal (including irrigation) areas shall be completed, approved and formally signed off by the Designer as complying with AS/NZS1547:2000 prior to commissioning of the system. Certification, in a format approved by Council; may include a site plan to scale showing the wastewater disposal locations and areas, property boundaries, infrastructure, GPS grid coordinates. 7. All pipes, pipe sleeves, identification tapes, and outlets on an irrigation system shall be coloured lilac (P23), in accordance with AS2700. 8. If one or more wastewater irrigation systems are proposed, they shall be constructed and installed in accordance with approved plans accompanying the Special Plumbing Permit, and the following:

Spray Irrigation Systems: The sprinklers used for distributing the wastewater must of a type that minimise formation of small droplets and aerosols. Impact and pencil type sprays shall not be used. A flush valve is to be installed on each irrigation area so that the lines can be flushed. The discharge from the flush valve must discharge either onto the irrigation area or piped back to a suitable chamber of the treatment system, having regard to whether the wastewater is chlorinated or not, so that the efficacy of the treatment plant is not compromised by the introduction of the flush water. Flush valves are to be installed in valve boxes to enable inspection and service.

Drip and Sub-surface Irrigation Systems: Only pressure compensated drip line shall be used. Vacuum breaker valves are to be provided at the high point(s) of all irrigation fields. Such valves are to be installed in valve boxes to enable inspection and service. A flush valve is to be installed on the low point of each irrigation field with piping discharging the flush water to a suitable chamber of the treatment system, having regard to whether the wastewater is chlorinated or not, so that the efficacy of the treatment plant is not compromised by the introduction of the flush water. Flush valves are to be installed in valve boxes to enable inspection and service.

9. Unless specifically advised by the Designer as unnecessary or inappropriate, an effective surface water diversion drain or mound shall be provided and maintained on the high side of wastewater disposal (including irrigation) areas. Note that all concentrated stormwater must be retained on the property. 10. Weed matting, plastic or other materials that impede water penetration into the soil shall not be used between the irrigation system and the soil surface. 11. All wastewater irrigation areas shall be maintained in good order at all times. Such maintenance includes but may not be restricted to weeding, mowing, and replacement of mulch or plants. 12. Council shall be provided with an amended plan if the location of the irrigation area is altered or changed from the "as installed” plan. The owner shall ensure that any altered wastewater disposal (including irrigation) areas meet minimum setback distances from boundaries and buildings and any other conditions contained within this permit. 13. The wastewater treatment system shall be regularly maintained in accordance with the conditions of accreditation issued under the Tasmanian Plumbing Code. 14. Any septic tank associated with the disposal system shall be desludged at least once every three years. 15. Where required, the owner shall enter into and maintain an on-going service maintenance agreement with a person with appropriate qualifications and experience to maintain the wastewater disposal system in accordance with the Plumbing Regulations 2004 and the Tasmanian Plumbing Code. A copy of the signed agreement shall be submitted to Council before commissioning of the system.

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16. Where required, effluent quality for land application shall meet the criteria specified in the installed system's certificate of accreditation or, if not specified, as follows (from AS/NZS1547:2000):

5-day Biological Oxygen Demand (BOD5) 20mg/L Suspended Solids (SS) 30mg/L Thermotolerant coliforms 10 per 100mL Free chlorine residual 0.5mg/L

17. Only when these tests indicate compliance will the unit be regarded as being commissioned. A NATA approved laboratory should conduct such tests. Testing shall be conducted as follows:

a) Commissioning phase: Mandatory testing after three months from the final installation inspection (to coincide with the normal on-going scheduled maintenance visits) but fortnightly in the event of failure to comply b) On going operational phase: Mandatory testing for a free chlorine residue is required every three months. Remedial works should be undertaken when the minimum fire chlorine residual is not met. Random surveillance for BOD5, SS and thermotolerant coliforms shall be done at no less than once each 4 years. An authorised person may require sampling for BOD5, SS and thermotolerant coliforms or to undertake other chemical analyses to help identify operational problems.

18. Where required, monitoring details for individual on-site waste water management systems are to be recorded on a standardised form and lodged with the Council each quarter. 19. A final inspection of all installations may be conducted by a Council Environmental Health Officer following receipt of the written certification from the system designer. Plumbers and owners should be made aware that a minimum number of working days notice is required for such inspections and the building will need to be open for inspection as required.

W. C. Cromer Principal This report is and must remain accompanied by the f ollowing Attachments Attachment 1. Location, aerial photography and published geology (2 pages) Attachment 2. Schematic of existing wastewater system (1 page) Attachment 3. Sketch map showing locations of auger holes, permeability tests, recommended ADA

(dashed red line) for wastewater management, and suggested location of PDA#2 (2 pages) Attachment 4. Site photographs (2 pages) Attachment 5. The three Summary Report pages from a Trench3.0 assessment for the site (3 pages) Attachment 6. Design notes for and examples of conventional and nonconventional beds (13 pages)

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IMPORTANT NOTES

The evaluator/assessor

William C. Cromer Pty. Ltd. is a site evaluator/soil assessor in terms of Clause 3.5.4 of AS/NZS1547:2000. Evaluators/assessors "may include appropriately trained soil

scientists, geotechnical engineers, civil and environmental engineers, land surveyors or other experienced people who undertake land-capability evaluations."

In addition to presenting assessment advice, this Site and Soil Evaluation Report

(SSER) also includes a schematic System Design. The schematic is provided as a service to clients, and as an aid to Designers and Installers with recommendations about the sizing, selection, and location of wastewater disposal systems (but not

necessarily their detailed design).

This SSER does not constitute an application for permission to install a wastewater disposal system. However, it should be used to support and accompany such an

application.

The Designer Clause 3.5.5. of AS/NZS1547:2000 states that Designers "may include professional engineers, soil scientists, drainage contractors or plumbers with appropriate training

and experience in design and installation practice."

Designers prepare design reports including an application to install, relevant aspects (or all) of this SSER, and details of the selected system. Designers "are familiar with information on current installation trade practices, the range of materials and methods used, the types of machinery available to the installer and the level of

operator competence required for their use" [AS/NZS1547:2000 Clause 3.5.5.(c)].

Depending on the details of individual sites and system designs, the requirements of the last sentence may be outside the expertise of William C. Cromer Pty. Ltd.

Council may require the Designer to inspect the system during construction, and

certify that it has been installed according to recommendations.

The Installers/contractors Clause 3.5.6 of AS/NZS1547:2000 states that Installers/contractors "may include

certified drainlayers and plumbers, technical or professional engineering people or any other persons with appropriate experience in construction and installation."

The installer/contractor may be required to certify aspects of the wastewater system.

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Attachment 1 (2 pages)

Location, aerial photography and published geology Sources: www.thelist.tas.gov.au and Mineral Resources Tasmania

1

GN 0

Approx. km

Aerial photography

Deleted

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Sources for geology Leaman, D. E. (1972). Geological atlas 1:50,000 series. Hobart. Tasmanian Department of Mines, and

Gulline, A.B. (1982). Geological atlas 1:50,000 series. Sorell. Tasmanian Department. of Mines

Key to colours: Stippled blue = Permian-age sedimentary rocks; Yellow = Quaternary-age alluvium, wind-blown sands, etc.

1

GN 0

Approx. km

Deleted

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Attachment 2 (1 page)

Schematic of existing wastewater system

Deleted

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Attachment 3 (2 pages)

Sketch map showing locations of auger holes, permea bility tests, recommended ADA (dashed red line) for wastewater management, and suggested location of PDA#2

See next page for explanation of ADA, PDA, etc.

Fence

50

GN 0

Approx. metres

Components of upgraded wastewater system Retain and use existing trenches (in PDA#1) and pump pit with pump. Install new conventional bed in PDA#2 as shown. Bed fed by existing pump via 32mm poly pipe (purple coded). Return line (with valve at pit) from bed to pump pit to enable bed flushing. Plumber to check pump has duty to cope with existing trenches and new PDA#2. Upgrade if required. Upgrade existing septic tanks to the equivalent of a single, dual purpose tank of 4,000L discharging to pump pit.

Gate

Gate

Sandy track (location can be

changed if needed)

A, 0.15, 0.70 C, 0.17, 0.55

B, 0.35, 0.75

Property boundary

4-bedroom equivalent house; rain water tanks;

standard water saving fixtures

Fence

J, 1.03, 0.50

G, 0.72, 0.75 Large eucalypt

Pump pit, 0.00 Trench GL, 0.00

0.7

0.7

0.7

0.75

0.4

0.7

H, 0.85, 0.70

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0.90

1.90

1.70

0.40

1.10

D, 0.66, 0.90

K, 0.55, 0.90

I, 0.83, 0.60

F, 0.65, 0.70

ADA

1-bedroom equivalent unit; standard water saving fixtures

Native grasses

Native grasses

Grassed

Grassed

Grassed

Permeability test results (Cromer Constant Head Permeameter)

Auger hole Depth interval (m) tested

Permeability (m/day)

D 0.2 – 0.5 0.2

E 0.16 – 0.55 0.15

ADA

ADA

Top ST, 0.14 PDA#1

E, 0.58, 1.10

PDA#2

Design notes for PDA#2 See Attachment 6 for general design notes and examples. Conventional (in ground) bed in PDA#2 shall be located as shown, with its N corner 2m from gate and 1m upslope from sandy drive. Orientate its long axis parallel to the drive. The bed must have a minimum wetted area of 70m2, with no protective perimeter strip. Nominal length shall be 14m, and width 5m and depth on downslope side no more than 200mm. Step the bed if appropriate to make two parallel beds each 2.5m wide. Use 25mm colour-coded poly pipe perforated each metre or so with 3mm holes for wastewater distribution, on a 25mm thick screened durable gravel bed. Bed fed by existing pump via 32mm poly pipe (purple coded). Return line (with valve at pit) from bed to pump pit to enable bed flushing. Use short lengths of pipe to join different parts of the system, to help equalise pressure. Designer to inspect before poly distribution pipework is covered (with gravel, geofabric and final c.150mm of on-site sand soil). No upslope cut-off drain required. Corners of completed PDA#2 to be permanently pegged out. Heavy animals and vehicles are prohibited over PDA#1 and PDA#2. Hole ID

Auger hole with permeability test

C, 0.17, 0.55

Hole depth and sand thickness (m)

Hole elevation (m) relative to top of pump pit

Auger hole with water at base (August 2012)

1.10 Slope angle (o) and direction

Contour line (0.1m interval)

Key

Min setback 5m

32mm poly pipes 4,000L equivalent septic tank

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Explana tion of ADA, PDA, SDA, Disposal System and Setback Distance

Disposal system. It must be wholly within the PDA, and may consist of one or more beds or trenches, or other suitable designs. The system may comprise perforated arches, or a line or grid of rigid perforated distribution pipework (‘a’ at left) if low pressure (eg small gravity head), or an irregular layout of smaller diameter perforated polyethylene pipework (‘b’ at left) if sufficiently pressurised (eg via pumping or with adequate gravity head). Whatever the construction details, the area of the disposal system must be at least equal to the minimum wetted area required from water balance calculations, and the system must be able to wet the required minimum area.

‘a’

‘b’

The Available Disposal Area (ADA ) is the area reasonably available for wastewater disposal, after applying any setbacks (see below) and subtracting the areas covered by permanent infrastructure. The ADA may be a single area, or two or more separate areas. The total size of the ADA may vary depending on whether the effluent to be disposed of is treated to primary level or secondary level. The heavy dashed area (‘a’ at left) is the ADA for either type of effluent; the fine dotted area (‘b’ at left) is the ADA for secondary treated effluent only.

‘a’

‘b’

Setback distance. This is the minimum distance required between the lowest, watercourse, dam, house, road cutting, etc.) The setback distance is always measured at right angles to topographic contours. It applies only to subsurface movement of wastewater, not overland flow. It may be estimated using the separation distance module in Trench®3.0.

10m

Primary Disposal Area (PDA). This (or these) must be wholly within the ADA. It consists of (a) the disposal system (eg bed(s) or trench(es)), (b) any separation distances between the beds or trenches, and usually, (c) a perimeter strip to protect the system. The system area must be at least equal to the minimum wetted area requirement, but will usually be greater by the area of the perimeter strip, etc. A Secondary Disposal Area (SDA) may be required by regulatory authorities for a back-up system in the event of failure, or changed circumstances. The SDA must be the same size as the PDA, and must be located within the ADA.

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Attachment 4

(2 pages) Site photographs

Plate 2 (below). View northeast looking over the existing pump pit towards the existing trenches in PDA#1.

Deleted

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Plate 3 (above). Auger hole E, showing 1.1m of fine sand. A permeability test over the interval 0.16 – 0.55m returned a value of 0.15m, which (despite the Category 1 texture) is Category 4 in terms of permeability. Plate 4 (below). View east over the area recommended for PDA#2, comprising a single or 2 stepped conventional beds 14m long x total 5m wide with 25mm colour-coded poly distribution pipe as shown schematically. See report for details.

Auger hole E

Auger hole E

Auger hole D

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William C Cromer Pty LtdLand suitability and system sizing for on-site wastewater management

Trench 3.0 (Australian Institute of Environmental Health)

Site Capability ReportWastewater management

Assessment for A. Sheehan and B. Wilson Assess. DateRef. No.

Assessed site(s) 9 Richardsons Road, Sandford Site(s) inspectedLocal authority Clarence City Council Assessed by

Consultant Engineering Geologist

ConfidAlert Factor Units level

Expected design area sq m High Moderate

Density of disposal systems /sq km Mod. Very low

Slope angle degrees V. high Very low

Slope form Straight simple V. high Low

Surface drainage Good High Very low

Flood potential Site floods

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Environmental Sensitivity ReportWastewater management




ConfidAlert Factor Units level

Cation exchange capacity mmol/100g High Very high Moderate

Phos. adsorp. capacity kg/cub m High High Moderate

Annual rainfall excess mm Mod. Very low

Min. depth to water table m High Moderate

Annual nutrient load kg Guess Low

G'water environ. value Agric non-sensit High Low

Min. separation dist. required m High Very low

Risk to adjacent bores

Surf. water env. value Agric sensit/dom drink High Moderate

Dist. to nearest surface water m High Moderate

Dist. to nearest other feature m High Moderate

Risk of slope instability Very low High Very low

Distance to landslip m High Very low

Sheehan016 and 13 August 2012

W. C. Cromer

1.1

5.6

5

15 Other factors lessen impact

LimitationValue

0.2 Other factors lessen impact

-47

200

50

1000

Trench Amended Remarks

Factor not assessed

14 08 12

This report summarises data relating to the environmental sensitivity of the assessed site(s) in relation to applied wastewater. Physical capability andsystem design issues are reported separately. The 'Alert' column flags factors with high (A) or very high (AA) limitations which probably requirespecial consideration in site acceptability or for system design(s). Blank spaces indicate data have not been entered into TRENCH.

Comments

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Assessment ReportWastewater management




Wastewater CharacteristicsWastewater volume (L/day) used for this assessment = (using the 'No. of bedrooms in a dwelling' method)

Septic tank wastewater volume (L/day) = Sullage volume (L/day) =

Total nitrogen (kg/year) generated by wastewater = Total phosphorus (kg/year) generated by wastewater =

Climatic assumptions for site (Evapotranspiration estimated using mean max. daily temperatures)Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Mean rainfall (mm) 49 41 44 50 47 50 47 45 44 57 51 57Adopted rainfall (R, mm) 53 46 48 55 53 55 53 50 48 60 55 60

Retained rain (Rr, mm) 53 46 48 55 53 55 53 50 48 60 55 60Max. daily temp. (deg. C) 20 21 19 17 15 12 12 13 15 16 19 20

Evapotrans (ET, mm) 74 65 58 49 43 43 45 48 54 60 68 74Evapotr. less rain (mm) 21 19 10 -6 -10 -12 -8 -2 6 0 13 14

Annual evapotranspiration less retained rain (mm) = 47

Soil characterisiticsTexture = Category = 4 Thick. (m) = 0.8

Adopted permeability (m/day) = Adopted LTAR (L/sq m/day) = 12 Min depth (m) to water = 1.1

Proposed disposal and treatment methodsProportion of wastewater to be retained on site: All wastewater will be disposed of on the site

The preferred method of on-site primary treatment: In dual purpose septic tank(s)The preferred method of on-site secondary treatment: In-groundThe preferred type of in-ground secondary treatment: Evapotranspiration bed(s)

The preferred type of above-ground secondary treatment: NoneSite modifications or specific designs: Are needed

Suggested dimensions for on-site secondary treatmen t systemTotal length (m) =

Width (m) = 7Depth (m) = 0.6

Total disposal area (sq m) required = comprising a Primary Area (sq m) of:

and a Secondary (backup) Area (sq m) of: Sufficient area is available on site

10

140

805

70

2.4

70

0.2sand

270540

14 08 12

1.6

Sheehan016 and 13 August 2012

W. C. Cromer

This report summarises wastewater volumes, climatic inputs for the site, soil characteristics and sustem sizing and design issues. Site Capability andEnvironmental sensitivity issues are reported separately, where 'Alert' columns flag factors with high (A) or very high (AA) limitations which probablyrequire special consideration for system design(s). Blank spaces on this page indicate data have not been entered into TRENCH.

The exisitng trenches in PDA#1 are adequate for 1.5 of the 5 bedroom equivalents. This Trench assessment therefore adressessystem sizing for 3.5 bedrooms ie 805L/day; standard water saving fixtures, DLR of 12mm/day. The wetted area in PDA#2 is about70m2, or 20m2/bedroom.

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Attachment 6 (13 pages including this page)

Design notes for and examples of conventional and nonconventional beds

The following notes and photographs are intended as guidance only for conventional and nonconventional beds. It is acknowledged that on a site specific basis the designs might need to be altered. It is also recognised that a range of different wastewater management systems might be environmentally appropriate.

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Layer 4. Geotextile (perforated and permeable)

Layer 5. 150mm imported or on-site soil. Grass or plant water loving, shallow-rooted species. Pedestrian access OK, but no heavy animal or vehicle access

Layer 3. Place 25mm layer of clean, screened gravel (eg 7, 10, 15mm bluemetal). Then 20-25mm diam poly pipework (or for gravity flow systems, 90 or 100mm PVC pipe) perforated with nom 3-4mm holes at nom. 0.8m centres, Cover pipework with min. 50mm gravel. Pipework must be at least 1m from outer edge of bed. To equalise pressure distribution in poly pipe, link segments of pipe. To aid flushing in poly pipe, include a return line (with control valve) back to pump or treatment system. For gravity flow system, include vertical IO’s to surface at corners and elsewhere to aid flushing.

Layer 2. Construct bed of imported or on-site clean sand or sandy loam (no clay, rocks, roots, etc) on existing ground surface. Do not compact. Suggest 0.2 – 0.3m thickness along higher side, thickening downslope over PDA. Make top surface level to +/-5mm.

Layer 1. Existing soil. Rotary hoe or otherwise plough and loosen to a depth of nominally 0.2-0.3m.

LAYER 1

LAYER 2

LAYER 3

LAYER 5

LAYER 4

Colour-coded, perforated polyethylene pipework, or for

gravity flow systems, perforated 90mm or 100mm PVC pipework

Inner (upslope) edge) Outer (downslope) edge) New ground surface

Seepage pathways

Nom 0.2-0.3m wide

Clean, coarse sand or screened gravel to surface

Detail of subsurface cut-off drain

Flexible perforated agricultural pipe laid on, and covered by, 5mm screened clean aggregate

Permeable geotextile

Schematic cut-off drain into Layer 1

One metre min

Outer edge of bed may be soil graded at 1:3 or gentler, or supported by

wall of any construction, but with

no substantial foundation into Layer 1

Landscape; plant with water loving, shallow rooted species

See detail below

1

2

3

5

Original ground surface

Schematic cross-section of nonconventional (raised) bed

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Nonconventional beds that receive wastewater under pressure (eg from a pump, or a sufficient gravity head) need not be levelled to the same high tolerance (5mm) as gravity flow systems. They can also be constructed of polyethylene pipe laid in any fashion which uniformly covers the wetted area requirement. Perforations are drill holes about 3-4mm in diameter at nominally 0.8m intervals, but it is best to lay the pipework unperforated, and add holes by trial and error during water testing. Excess holes can be plugged, or others added. The conventional (in-ground) bed below is in the process of testing. Use short lengths of pipe to join different parts of the system, to help equalise pressure. A return line to the pump pit, with a control valve attached, should be installed to permit flushing of the pipework from time to time.

Pressurised system

Pressurised system

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Nonconventional terraced beds with timber retaining walls and surface covers of mulch. The rocks are not essential but add aesthetic value. Clockwise from top left: 1 and 2. The distribution pipework is held down by temporary weights before perforating, testing and covering with screened gravel, filter cloth (geofabric) and soil. 3. Cross connections help equalise pressure. The aim is to achieve an even distribution of wastewater. 4 and 5. The completed and landscaped bed.

1

2

3

4

5

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Nonconventional beds as terraces with timber retaining walls and surface covers of mulch. An appropriate distance (at least 1m suggested) must be maintained between each retaining wall and the distribution pipework behind it.

A grassed nonconventional bed six months after completion.

Nonconventional bed

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Above and below. This nonconventional bed received gravity flow wastewater from a septic tank further up the slope at right. PVC pipework perforated with 3mm diam holes at 0.8m centres was used instead of polyethylene pipework. The PVC needs to be level with a tolerance of less than a few millimetres. The bed was later completed with screened gravel to cover the pipework, a geotextile cover, and a 150mm layer of on-site soil.

Gravity flow system

Gravity flow system

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Above. This conventional (in-ground) bed receives gravity flow wastewater from a septic tank at left. PVC pipework perforated with 3mm diam holes at 0.8m centres was used instead of polyethylene pipework. The PVC needs to be level with a tolerance of better than a few millimetres. At this site, the pipework needed to be placed at a depth of about 0.6m to provide sufficient gravity fall from the septic tank, but lesser depths (eg 0.2m) to the top of the pipework are acceptable). Below. The bed is being completed with more gravel to cover the pipework, a geotextile cover, and a layer of on-site soil to surface.

Geotextile

Gravel

On-site soil

Gravity flow system

Gravity flow system

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Above and below. Before drilling holes in the PVC pipework, fill it with water first, and then drill. In this way, the number and spacing of holes can be adjusted to achieve an even distribution of wastewater over the gravel bed. Use a guide (above) to ensure all holes are the same height above the base of the pipe, which itself is laid horizontally using a dumpy level or laser level to a tolerance of better than a few millimetres. As a guide, it is suggested holes are 3-4mm in diameter (below), drilled on one side of the pipe only, and spaced about 0.8m apart. The best spacing depends on the gravity head into the system. Holes in poly pipe need to be similarly located.

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Above and below. For gravity flow nonconventional beds which use 90mm or 100mm perforated PVC pipework, include inspection openings (IO’s) at least at each corner, and preferable elsewhere in the pipe grid. Extend the IOs to the surface (below) and complete with a screw cap. The purpose of the IO’s is to provide access to the buried pipework for flushing or cleaning (eg with a water jet or hose).

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Above and right. A nonconventional bed with final soil cover (above), and soon after (right) with a grass cover becoming established. This bed receives primary treated wastewater from a single purpose septic tank, which discharges into a pump pit (green cover at right). A return line with gate valve from the bed to the pump pit ensures the buried pipework is able to be flushed if needed.

Pressurised system

Pressurised system

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Left. Site selected for nonconventional bed receiving septic tank effluent from a new public toilet block at Gordon for Kingborough Council (2010). Below. Nonconventional bed during installation. Colour-coded 25mm poly pipe is laid on nominally 50mm of screened durable gravel, itself laid on 0.3m of Category 1 sand soil. The pipe is then to be perforated (3-4mm diam drill holes; one each metre), covered with gravel and geofabric, then 0.15m of loam and finally pine bark.

Pressurised system

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Above. Kingborough Council public toilet block at Gordon: dual septic tanks and pump pit with float-operated pump. Visible and audible alarms for pump failure are mounted on the adjacent toilet block. Below. Completed, nonconventional bed with pine bark cover ready for planting with local provenance native shrubs.

Pressurised system

Pressurised system

Documents

Words, maps, and photographs which might identify the site …...The property covers about a hectare, is mainly cleared to gardens, lawns and native grasses, and is mostly flat, with