proposed place of worship 295 (lot 10 ......figure 4 shows the gswa mapping. test pitting at seven...

Sundowner Nominees Pty Ltd as trustee for the Bayley Cook Family Trust ABN 20 822 598 897 trading as Bayley Environmental Services

PROPOSED PLACE OF WORSHIP 295 (LOT 10) SEABORNE ST, PARKERVILLE

ENVIRONMENTAL ASSESSMENT

Prepared for

Mundaring Gospel Trust c/- Rowe Group

369 Newcastle Street NORTHBRIDGE WA 6003

Draft Report No. J19004 9 October 2019

BAYLEY ENVIRONMENTAL SERVICES 30 Thomas Street SOUTH FREMANTLE WA 6162

Proposed Place of Worship, 295 (Lot 10) Seaborne St, Parkerville – Environmental Assessment Page i ______________________________________________________________________________________

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BAYLEY ENVIRONMENTAL SERVICES

TABLE OF CONTENTS Page

1.0 INTRODUCTION 1

2.0 PROJECT DESCRIPTION 1

3.0 EXISTING ENVIRONMENT 23.1 Rainfall 23.2 Physiography 3

3.2.1 Topography 33.2.2 Geology and Soils 33.2.3 Hydrology 5

3.3 Vegetation 53.4 Fauna 63.5 Land Uses and Contamination 63.6 Aboriginal Heritage 6

4.0 EFFLUENT TREATMENT AND DISPOSAL 74.1 Land Capability for On-site Effluent Disposal 7

4.1.1 Site Area and Capacity 74.1.2 Slope 74.1.3 Soil Profile 74.1.4 Soil Permeability 74.1.5 Published Land Capability Recommendations 84.1.6 Land Capability Summary 8

4.2 Effluent System Conceptual Design 84.2.1 Effluent Generation 84.2.2 System Selection 94.2.3 System Location 114.2.4 System Sizing 11

5.0 EROSION AND SEDIMENT CONTROL 145.1 Erosion Risk Assessment 145.2 Priorities 145.3 Site Management 145.4 Basin Sizing 155.5 Long-Term Basin Use 15

6.0 STORMWATER MANAGEMENT 166.1 Overview 166.2 Drainage Management System 166.3 Basin Sizing and Design 166.4 Water Quality Management 186.5 Maintenance 18

Proposed Place of Worship, 295 (Lot 10) Seaborne St, Parkerville – Environmental Assessment Page ii ______________________________________________________________________________________

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7.0 GROUNDWATER MANAGEMENT 197.1 Groundwater Levels 197.2 Groundwater Quality 19

8.0 LANDSCAPING 208.1 Landscaping Zones 208.2 Water Supply 22

CONSTRUCTION MANAGEMENT 23

9.0 IMPLEMENTATION 249.1 Responsibilities 249.2 Monitoring 249.3 Contingencies 24

10.0 REFERENCES 26

Proposed Place of Worship, 295 (Lot 10) Seaborne St, Parkerville – Environmental Assessment Page iii ______________________________________________________________________________________

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LIST OF TABLES

Table Title Page

3.1 Rainfall Intensity for Parkerville 3 4.1 Site Population and Operating Hours 9 6.1 Drainage Design Parameters 17 6.2 Runoff and Basin Sizing 17

LIST OF FIGURES

Figure Title

1 Oblique Aerial View 2 Development Plan 3 Bickley Mean Rainfall (p.2 of document) 4 Environmental Features 5 Drainage and Sediment Controls 6 Detention/Bioretention Basin Profile 7 Landscape Concept Plan

LIST OF APPENDICES

Appendix Title

A Soil Logs B Permeability Test Results C Effluent Flows and System Sizing D Runoff Calculations and Basin Sizing

Proposed Place of Worship, 295 (Lot 10) Seaborne St, Parkerville – Environmental Assessment Page 1 ______________________________________________________________________________________

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1.0 INTRODUCTION

The Mundaring Gospel Trust is proposing to construct a place of worship at 295 (Lot 10) Seaborne St, Parkerville. Figure 1 shows an oblique aerial view of the site.

The Trust, through its planners Rowe Group, has submitted a Development Application to the Shire of Mundaring. This environmental assessment report has been prepared in support of that application.

2.0 PROJECT DESCRIPTION

The development will comprise the following major elements:

a main building measuring approximately 1,297 m2;surrounding paved areas and walkways measuring 416 m2;a sealed car park and driveways measuring approximately 3,906 m2; and a stormwater bioretention basin measuring 228 m2.

The remainder of the 2.02ha site will remain unchanged from its current state.

The development will employ on-site effluent disposal and will be served by scheme water, power and telecommunications.

Access to the site will be via a driveway in Seaborne Street.

Figure 2 shows a plan view of the major elements.


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3.0 EXISTING ENVIRONMENT

3.1 Rainfall

Parkerville has a strongly seasonal rainfall, with most of the annual rain falling between May and September in association with winter cold fronts. Occasional heavy falls may occur from summer thunderstorms. The long-term average annual rainfall for Bickley (the closest Bureau of Meteorology weather station) is 1,088.8mm, of which 78% falls between the months of May and September.

Figure 3 shows a rainfall occurrence chart for Bickley. Table 3.1 shows rainfall intensity and frequency for Parkerville.

Figure 3 Bickley Mean Rainfall


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Table 3.1 Rainfall Intensity for Parkerville

3.2 Physiography

3.2.1 Topography

Lot 10 lies on an east-facing slope on the undulating Darling Plateau. The elevation ranges from 266m AHD at the south-east corner to 276m AHD at the south-west corner. The development area slopes generally to the east at a gradient of about 3% to 6%. Figure 4 shows topographic contours over the site.

3.2.2 Geology and Soils

The majority of Lot 10 is mapped by the Geological Survey of Western Australia (Smurthwaite, 1986) as colluvial gravel (Czl/G2), consisting of yellow-brown to reddish brown, loose, fine to coarse, ferruginous pisolites, poorly sorted, with variable amounts of sand and silt and minor recementation. The western end of the site is mapped as laterite (Czl/LA1): massive, hard, cemented, vuggy and pisolitic; up to 4m thick, overlain by and associated with gravels (G2 and G3), of residual origin. Figure 4 shows the GSWA mapping.

Test pitting at seven locations across part of the lot mapped as Czl/G2 (Figure 4) found soil profiles that broadly confirm the GSWA mapping. The test pits generally found a gravelly-sandy clay-loam to about 0.5m over orange-yellow well-structured loamy clays.


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Two test pits near the centre of the site found a soft white, well structured sandy clay below 1.2 – 1.5m. Laterite boulders were encountered in the south-east of the site and some laterite outcrop was present in the north-west, but no extensive laterite was encountered. The soils were generally well-structured and permeable to the maximum depth of excavation (about 2.5m).

Optimum Engineering Consultants (OEC) drilled ten boreholes to 2.5m in February 2019, focussing on the footprint of the building and car park (Figure 4). OEC reported the soil profile as generally pebbly sandy silt to about 2m over orange-brown mottled silty clay to 1.5m underlain by white/orange/brown mottled silty clay to 2.5m.

Soil logs from the test pits are shown in Appendix A.

Soil-Landform UnitsThe Department of Agriculture (King & Wells, 1990) mapped most of Lot 10 as within the Murray-3 (My3) soil-landform unit, described as “Gently to moderately inclined sideslopes and lower slopes with very few areas of rock outcrop”, within “Deeply incised river valleys with up to 120m relief occurring upstream from the Helena Valley System”. The soils were described as “Yellow, red and brown gradational earths” and Yellow and mottled yellow duplex soils”.

The western end of the lot was mapped as Dwellingup-2 (D2) unit, described as “Gently undulating terrain with well drained, shallow to moderately deep gravelly brownish sands, pale brown sands and earthy sands overlying lateritic duricrust”.

These generally match the soils observed on the site. Figure 4 shows the DoA land units.

Soil Permeability Constant-head infiltration tests were carried out at 0.5m depth at four sites in the expected vicinity of the effluent disposal and drainage infiltration structures (Figure 4) using the method set out in Australian/New Zealand Standard 1547:2012 – On-site Domestic Wastewater Management. The tests gave saturated hydraulic conductivity (Ks) values ranging from 6.5 to 14 m/day. Details of the permeability tests are shown in Appendix B.

OEC carried out falling-head infiltration tests at 2m depth in two boreholes (Figure 4). These tests gave Ks values of 0.15 and 0.2 m/day. Falling-head tests typically give an over-estimate of hydraulic conductivity. Permeability normally decreases with increasing depth, so these results are consistent with the results of the constant-head tests.

The tests show that the shallow soils of the site are permeable and well drained. For the purposes of drainage design and basin sizing a Ks of 2 m/day has been adopted.


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Phosphorus Retention Index Phosphorus Retention Index (PRI) is a measure of the ability of a soil to adsorb and retain phosphorus from solution. A high PRI indicates that the soil is unlikely to leach phosphorus to the water table. Typical ranges for PRI in soils are as follows:

PRI Range Rating Typical soils 0 – 0.5 Very Low Bassendean Sand 2 – 4 Low – Moderate Karrakatta Sands 5 – 12 Moderate – High Cottesloe Sands 12 – 20 High Crushed Limestone, Limesand 20 – 1000+ Very High Clay

The loamy and clayey soils of the site are expected to have high to very high PRI (20+). No site testing of PRI is considered necessary.

3.2.3 Hydrology

There is no defined surface drainage within Lot 10, although sheet overland flow would occur under heavy rainfall conditions.

There is unlikely to be significant shallow groundwater present over most of the site given the topography. Downslope seepage above the clay subsoils may occur in winter.

Lot 10 is in the catchment of Mahogany Creek, a small seasonal watercourse that flows south-west about 100m south-east of the site before joining Jane Brook about 1.6km to the north-west. Mahogany Creek has been dammed in numerous places.

The upstream surface catchment of the development site is very small, extending about 210m to the south-west and covering less than 0.5ha. About half of the catchment consists of forest, with the remainder being cleared paddocks and residential garden.

3.3 Vegetation

Lot 10 is mostly cleared of native vegetation. Remnant or regrowth Marri (Corymbia calophylla) trees are present, along with a few Jarrah (Eucalyptus marginata), on the northern and eastern sides, mostly outside of the development area. The understorey in these areas consists mostly of grasses and weeds, with a few native species including Acacias and Grasstrees.

At the western end of the Lot is an area of about 0.345ha of Marri-Jarrah woodland with a degraded understory. Historical Landgate aerial photography shows that this is mostly regrowth since the lot was almost entirely cleared prior to 1965. This area is mapped as a Local Natural Area (LNA) in the Shire of Mundaring’s Local Biodiversity Strategy (2009). The LNA in Lot 10 is mapped as “Protection” category, which is the second tier on the Shires four-tier priority scale for LNAs. The LNA on Lot 10 is outside


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the development area and will not be affected by the development. Figure 4 shows the boundary of the LNA.

3.4 Fauna

There is little habitat for native fauna within Lot 10, owing to the lack of dense ground cover.

Red-tailed Black Cockatoos were observed feeding on Marri trees in the LNA at the western end of the lot during the April 2019 site inspection. There were no signs of ground fauna such as kangaroos or Quenda observed in the site inspection.

3.5 Land Uses and Contamination

Historical aerial photography held by Landgate shows that Lot 10 has been cleared and used for grazing since before 1965. In that time there have been no structures or cropping (except hay) on the Lot. There is no visual evidence, on the photography or on the ground, of any potential for soil contamination.

The DWER Contaminated Sites Database lists no contaminated sites within 5km of Lot 10. No further investigation of contamination is considered necessary.

3.6 Aboriginal Heritage

The Department of Planning, Lands & Heritage (DPLH) Aboriginal Heritage Inquiry System shows that Lot 10 is not within any registered Aboriginal heritage site but is within one Other Heritage Place: 3188 Darling Range. This is a large site, covering more than 1,000ha and including John Forrest National Park, parts of Wooroloo Regional Park, farmland, industry, rural-residential and urban land.

Site 3188 is listed as “stored data” as a mythological site, camp, hunting place, meeting place, named place, natural feature and plant resource. The Aboriginal Heritage Act 1947 does not restrict land use within non-registered sites.


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4.0 EFFLUENT TREATMENT AND DISPOSAL

4.1 Land Capability for On-site Effluent Disposal

The Government Sewerage Policy (GSP, 2019) sets site requirements for on-site effluent disposal including site area, slope and soil profiles.

4.1.1 Site Area and Capacity

The superseded Government Sewerage Policy (2006) limited the density of unsewered non-residential development in the outer Metropolitan area to “R5 equivalent”, which equated to an effluent loading of 2,700 litres/ha/day.

Under the new 2019 GSP, the amount of effluent that can be disposed on a particular site is assessed case-by-case on the basis of site and soil characteristics and the type of treatment system proposed.

The effluent system sizing for the proposed place of worship on Lot 10 is based on an effluent discharge rate of 4,900 litres per day, based on the maximum site population and effluent loads set out in Table 4.1 (Section 4.2.1). The area of the lot is 2.0234 hectares, giving an effluent load of 2,422 L/ha/day, or R4.5 equivalent.

4.1.2 Slope

The GSP limits the slope of land used for effluent disposal to 20% (1 in 5). The slope in the area proposed for effluent disposal on Lot 201 (Figure 4) is in the order of 3%, well below the limit set by the GSP.

4.1.3 Soil Profile

Test pitting and drilling at 17 locations (Figure 4) showed that all soils on the lot possess a permeable, free-draining soil profile with at least 2.5m clearance above groundwater. There are no confining layers such as sheet rock or heavy clay present.

The soil profile appears well suited to on-site effluent disposal.

4.1.4 Soil Permeability

Permeability testing at six sites showed saturated hydraulic conductivities of 6.5 – 14 m/day at 0.5m depth and 0.15 – 0.2 m/day at 2m depth. This confirms that the soil profile is well suited to on-site effluent disposal.


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4.1.5 Published Land Capability Recommendations

The Department of Agriculture’s Land Resources Series No. 3: Darling Range Rural Land Capability Study (King & Wells, 1990) rated the capability of the Murray 3 (My3) soil-landscape unit for on-site effluent disposal using septic tanks as Fair, with the limiting factors being soil absorption ability and ease of excavation.

These limitations appear to apply to areas of the My3 unit with rock outcrop. The site investigations have shown that these limitations do not apply to Lot 10, so the capability for on-site effluent disposal is effectively High or Very High.

4.1.6 Land Capability Summary

The site investigations and literature review lead to the conclusion that Lot 10 has a high capability for on-site effluent disposal for the proposed development. Specifically:

The site has ample area to accommodate the effluent.

The soil profile is deep and free-draining, with no evidence of confining layers or shallow groundwater.

Limitations noted by the Department of Agriculture have been shown by site testing to be not applicable to Lot 10.

4.2 Effluent System Conceptual Design

4.2.1 Effluent Generation

The number of worshippers using the facility will vary from day to day and week to week. Worshippers will typically be on site for between one and 1½ hours. Table 4.1 shows the expected usage.

The facilities on site will include toilets and hand basins but will not include showers, kitchens or laundry facilities.


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Table 4.1 Site Population and Operating Hours

Weekdays Monday Tuesday Wednesday Thursday Friday

Number of Patrons 40 120 150-250 150-250 120

Time on Site 5:15-6:00pm 7:15-8:30pm 5:45–7:00pm 7:15-8:30pm 7:15-8:30pm

Frequency Weekly Weekly 3 times/month Monthly Monthly Weekends

Saturday Sunday

Number of Patrons 120 150-250 40 350-450 150

Time on Site 7:45–8:45am 11am–12pm 6am–7am 11am-12:30pm 5pm–6pm

Frequency Monthly1 Monthly1 Weekly 2 times/month2 2 times/month2

Special Events Sunday3

Number of Patrons 500-600 Up to 900

Time on Site 8am-6pm 8am-6pm

Frequency Annually Every 3 years

Notes:1 Saturday morning and midday sessions will occur on alternate Saturdays. 2 Sunday midday and evening sessions will occur on alternate Sundays. 3 For special events hosting more than 500 persons, portable toilets will be hired to reduce the load

on the on-site system. When special events are held, other Sunday sessions will not take place.

Table 4.1 shows that the maximum site population during normal usage will be up to 490 persons on alternate Sundays. The Health Department of WA (A. Richard, pers. comm.) has advised that sizing of the effluent disposal system should be based on the maximum site population and an effluent generation rate of 10 litres/person/day, as set out in Supplement to Regulation 29 and Schedule 9 – Wastewater System Loading Rates (2017). Using the maximum site population of 490 patrons, this gives an effluent flow of 4,900 litres/day.

Occasional (annual and triennial) special events will see attendances of up to 900 persons in one day, which would exceed the capacity of the on-site effluent disposal system. In order to deal with the large effluent flows generated by these occasional events, portable toilets will be hired to reduce the load on the on-site system.

4.2.2 System Selection

Effluent treatment and disposal may be achieved by:

a conventional septic tank and leach drain system; septic tanks with a modified (nutrient-removing) leach drain (e.g. Filtrex); an aerobic treatment unit (ATU) with leach drains; or an ATU with subsoil irrigation.

Septic systems have the advantage of being relatively cheap to install and operate. They also can be gravity-fed (site layout permitting), and the disposal area may be used for low-impact recreation including walking, croquet lawns etc. Maintenance of septic


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tank/leach drain systems consists of turning a valve every six to twelve months to switch between leach drain pairs, and infrequent (generally every four to ten years) desludging of the septic tanks.

Conventional leach drains require a minimum total soil depth of 2m above confining layers such as rock or heavy clay. However, flatbed leach drains are available that reduce the depth considerably.

Modified leach drain systems use a conventional septic tank but the leach drain is filled with an amended soil (such as bauxite residue) and enclosed in an impermeable membrane, so that the effluent flow from the leach drain is forced up through the amended soil before exiting at the top of the membrane. Because the exit point is at the top, rather than the bottom of the leach drain, these systems can be installed closer to the water table. Their main advantage is their ability to remove up to 95% of phosphorus from the effluent. Modified leach drain systems are more expensive to purchase and install but their operation and maintenance are essentially the same as for conventional septic systems. Modified leach drains are generally not necessary on sites with good clearance to groundwater and high-PRI soils.

Aerobic treatment units (ATUs) are essentially small wastewater treatment plants, with multiple chambers operated by electric pumps and, in some cases, disinfection and chemical dosing. They produce a higher quality of effluent than septic tanks, although not as high as modified leach drain systems. Treated ATU effluent can be disposed of by leach drains or by subsoil irrigation. The major advantage of subsoil irrigation is that the height of the disposal system is only about 150mm (essentially the depth of soil cover over the drip lines), so the irrigation area can be sited on areas of shallow soil with less need for mounding than leach drains.

The disadvantages of ATUs are:

they are more expensive than septic systems to purchase, install and operate; they require regular (generally every three months) maintenance by a qualified person;they require inputs of power for the operation of the ATU and pressure distribution of the treated effluent; if using effluent irrigation, the irrigation area must be dedicated for that purpose and cannot be used for anything else; and they cope less well with “shock loadings” and widely varying daily effluent flows.

The scale and operation of the proposed place of worship, with intermitted occupancy and occasional large populations, does not favour an ATU system. The system sizing and layout discussion below is based on a conventional septic tank/leach drain system.


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4.2.3 System Location

The septic tanks and leach drains will be located south of the building and car park respectively, to enable the system to be largely gravity-fed. Figure 2 shows the proposed locations of septic tanks and leach drains.

This location has limited space for leach drains, and will require the use of a holding tank to spread the effluent flow over the week. The sizing of the holding tank is discussed below.

4.2.4 System Sizing

4.2.4.1 Septic Tanks

The Health Regulations require that a septic system should include a tank or tanks with a “reserve capacity” of 1,820 litres plus the equivalent of the maximum daily effluent flow. The maximum daily effluent flow is expected to be 4,900 litres/day. This means that a septic tank or tanks totalling 6,720 litres is required.

4.2.4.2 Holding Tank

The use of a holding tank located downstream of the septic tanks will allow the fluctuating daily flows to be spread over a full week. This will reduce the maximum daily effluent flow to the leach drains from 4900 litres to 2170 litres, thus more than halving the total length of leach drain required.

The holding tank will be equipped with a level switch and pump to enable effluent discharge to be matched to the capacity of the leach drains. The tank will be sized to contain the maximum cumulative flow (occurring on alternate Sundays) plus one following day’s flow in case of pump failure.

The size of the holding tank has been calculated at 3,460 litres. Appendix C shows the calculations used to determine the required size of the holding tank. The sizing will be confirmed by the supplier of the septic system prior to installation.

4.2.4.3 Leach Drains

Leach drain sizing in commercial applications is primarily determined by the effluent volume and quality and the soil type (and hence permissible effluent loading rate). Table L1 of Australian Standard AS1547:2012 – On-site Domestic Wastewater Management sets out recommended daily loading rates for different soil types. The soil type present at Lot 10 is assessed as a moderately structured clay-loam for the purposes of the Table. Table L1 gives a conservative Design Loading Rate (DLR) of 10 mm/day and a maximum DLR of 15mm/day for this soil type. Given the high capability of the site and the low frequency of maximum effluent flows, a DLR of 15mm/day has been adopted.


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Regular leach drains consist of a concrete or brick channel with an open floor and perforated sides, with a nominal internal width of 0.4m, an external width of 0.61m and a height of 0.6m. The leach drain is laid in a trench which is backfilled with a layer of porous material (e.g. blue metal) overlain with soil. Different sizes of leach drain can be created by laying leach drain sections end-to-end (to a maximum length of 20m) and/or by laying drains side by side. Leach drains are normally arranged in pairs, with one of each pair being used and rested in a 6 to 12 month rotation. The leach drains must be laid on a lengthwise gradient of 1:200.

Based on the requirements and recommendations of the Government Sewerage Policy,the Health (Treatment of Effluent and Disposal of Liquid Waste) Regulations 1974, the draft Code of Practice for Onsite Sewage Management (2012), Australian Standard AS1547:2012 and the Shire of Mundaring’s Guidelines for the Installation/Construction of Wastewater System (2012), the following design parameters have been adopted for leach drains on the site:

Leach drain length Minimum 6m Maximum 20m (Code of Practice)

Leach drain width Internal 0.4m (Health Regulations) External 0.61m (Health Regulations)

Aggregate surrounding leach drain 0.3m (Shire of Mundaring) Spacing between leach drains – Parallel 3m End-to-end 1m (Shire of Mundaring).

The diagram below illustrates this conceptual design.

LEACHDRAIN

LEACHDRAIN

AGGREGATE AGGREGATE AGGREGATE AGGREGATE

TOPSOIL COVER

SURROUNDING SOIL

0.6m 0.6m 0.3m0.3m0.3m0.3m 2.4m

LEACHDRAIN

LEACHDRAIN

AGGREGATE AGGREGATE AGGREGATE AGGREGATE

TOPSOIL COVER

SURROUNDING SOIL

0.6m 0.6m 0.3m0.3m0.3m0.3m 2.4m

This design gives an effective infiltrative width of 1.6m, comprising the base and sides of the leach drain. When leach drains are arranged in parallel, each leach drain occupies an effective width of 3.6m.

The size of the leach drain field required can be calculated from the DLR and the leach drain dimensions as follows:

Maximum daily effluent flow (with holding tank) = 2.17m3/day DLR = 0.015m/day


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Length of leach drain = 2.17 / (1.6 x .015) = 90m (arranged as of 10 x 9m parallel leach drains) Total width = 9 x 3.6 + 1.2 = 33.6m Total length = 9 + 0.6 = 9.6m Total area = 33.6 x 9.6 = 323m2

Appendix C shows the detailed sizing calculations for the septic tanks and leach drains. The sizing calculations will be confirmed by the supplier of the septic system prior to installation. Figure 2 shows the footprint of the leach drains on the site.


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5.0 EROSION AND SEDIMENT CONTROL

5.1 Erosion Risk Assessment

An erosion risk assessment has been carried out for Lot 10 in accordance with the EMRC Erosion and Sediment Control Guidelines for the Shire of Mundaring (2008) and the Erosion and Sediment Control Manual for the Darling Range, Perth Western Australia (Lloyd & Van Delft, 2001).

The erosion assessment shows that Lot 10 falls within Soil Loss Class 1 (low risk), due to its permeable well-drained soils and its low slope. For this class of site, the EMRC recommends the preparation of an Erosion and Sediment Control Plan and implementation of control measures as set out in the manual. This chapter presents the Erosion and Sediment Control Plan for Lot 10.

5.2 Priorities

The priorities of erosion and sediment management on Lot 10 are:

limit soil disturbance to the area required for construction; limit the duration of soil disturbance; minimise upstream run-on to the construction site; minimise sediment generation on the site; trap sediments at or as near to the source as possible; capture and treat runoff from disturbed areas prior to release.

5.3 Site Management

Site management will feature the following:

A single access point to the construction site will be maintained from Hill Road.

A detention basin will be constructed south-east (downslope) of the construction site to capture runoff from the site and infiltrate or detain it to enable sediments to settle out. The basin will remain in place after construction and will be vegetated to serve as a bioretention/detention basin for the completed place of worship. Section 6.3 details the sizing and construction of the detention basin.

Temporary earthen bunds will be placed on the southern and eastern sides of the construction site to capture runoff and direct it into the detention basin.

The detention basin and temporary bunds will be constructed as the first stage in site construction works and will stay in place until the end of construction.

Figure 5 shows the locations of the runoff and sediment control structures.


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5.4 Basin Sizing

The detention basin will be sized for the post-development site, which will generate substantially higher internal rates of runoff (due to the greater area of impervious surfaces) than the construction site. Details of the basin sizing are presented in Section 6.3 and Appendix D.

Construction sites, no matter how carefully managed, are characterised by a relatively high proportion of loose soil surfaces. Sediments are most likely to become mobilised and carried off site by short-term, intense rain events producing high flows.

The basin will have the capacity to hold the runoff from approximately 50mm of rainfall on the construction site in a short period (roughly equivalent to a 100-year ARI 1-hour storm). Runoff above this will progressively overflow the basin through a pipe overflow set 0.6m above the floor of the basin. An overflow pipe of 100mm diameter at a slope of 1-in-10 would give an overflow rate approximately equivalent to a 5-year 1-hour storm. The basin will be constructed with 200mm of freeboard above the overflow pipe invert. A spillway will be set 100mm below the crest of the basin. The outlet of the overflow pipe and the spillway will be hardened (e.g. by concrete, rock rubble underlain by geotextile or similar) to prevent scouring. Figure 5 shows the footprint of the basin on the site. Figure 6 shows a profile of the basin and overflow structures.

5.5 Long-Term Basin Use

At the end of construction the basin will be left in place to act as a bioretention/detention basin for the developed site. The basin will be densely planted with suitable native sedges and shrubs to stabilise it and enhance its ability to remove nitrogen and suspended sediments from runoff. Details of the development of the basin are provided in Chapter 6.


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6.0 STORMWATER MANAGEMENT

6.1 Overview

The volume and rate of drainage within the site will be managed to maintain total and peak surface water flows at or below pre-development levels.

The stormwater management strategy aims to comply with the principles and objectives for stormwater management identified in the Stormwater Management Manual for WA (DoW, 2004) and Better Urban Water Management (WAPC, 2008).

Nutrient concentrations and loads in water leaving the site will be managed to comply with the targets of the draft Swan Canning Water Quality Improvement Plan (SRT,2009), as follows:

Winter median TP concentration: 0.1 mg/L Winter median TN concentration: 1.0 mg/L Annual TP yield: 0.013 kg/ha Annual TN yield: 0.2 kg/ha.

6.2 Drainage Management System

Runoff from the place of worship and paved surrounds will be collected by a combination of roof downpipes, gully pits and surface drains and conveyed to a bioretention/detention basin located downslope of the building pad (Figure 5). This drainage layout conforms to the natural topography of the site.

6.3 Basin Sizing and Design

Runoff and basin sizing calculations have been carried out by the Rational Method (Engineers Australia, 1987) using the following parameters:

Basin Depth 0.8 m Freeboard 0.2 m Base permeability 2 m/day Internal batter slopes 1 in 4

Table 6.1 summarises the surface areas and runoff coefficients adopted for the drainage design.


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Table 6.1 Drainage Design Parameters

1 - 5-year ARI 100-year ARI Surface Area (m2)Runoff

Coefficient Effective

Impervious Area (m2)

RunoffCoefficient

Effective Impervious Area (m2)

Driveway & car park 6,214 0.9 5,593 0.9 5,593 Building roofs 947 0.9 852 1 947 Brick paving 492 0.9 443 1 492 Basin 366 1 366 1 366 Totals 8,019 7,254 7,398

The bioretention basin will be sized to capture and infiltrate the runoff from all impervious surfaces within the development area resulting from a 1-year ARI 1-hour storm. The basin will also capture and infiltrate the excess runoff (over the undeveloped state) from critical storms up to 100-year ARI. Runoff from larger and longer-duration storms will be detained and released at a rate that does not exceed the pre-development flow rate.

Runoff from larger longer-duration storms will overflow the basin via an overflow pipe and/or a hardened (concrete or rock pitched) spillway and will flow overland to the roadside drainage. The overflow path will be bunded if necessary to ensure that runoff does not enter the neighbouring lot. The area downslope of the basin will be densely planted with shrubs and sedges to further slow and filter the overflow before it reaches the roadside drain.

Table 6.2 shows the calculated flows and basin sizes for the 1-year, 5-year and 100-year ARI storms. Figure 6 shows a conceptual profile and 1-year, 5-year and 100-year event plans for the bioretention basin. Appendix D shows the flow and basin sizing calculations. All volumes and dimensions are subject to detailed design.

Table 6.2 Runoff and Basin Sizing

Storm Event (critical duration)

Rain Intensity (mm/hr)

StorageRequired

(m3)

Basin Base Area (m2)

Top WaterArea (m2)

Water Depth (m)

Top Water Level (mAHD)

1 year ARI (1 hour)

16.1 102 105 288 0.54 266. 4

5 year ARI (20 mins)

50 42 105 195 0.28 266.14

100 year ARI (20 mins)

95 125 105 314 0.61 266.47

The basin will be normally dry, with all runoff infiltrating within 96 hours in order to minimise the potential for insect breeding. With a maximum depth of 0.61m and a nominal base hydraulic conductivity of 2 m/day, the basin will drain completely from the full level in under eight hours.


_____________________________________________________________________________________


6.4 Water Quality Management

The bioretention basin and other drainage features on the site will be designed to maximise on-site retention of nitrogen and phosphorus. This will be achieved by infiltrating all stormwater up to 1-yr ARI (representing more than 95% of annual flows) in a densely vegetated bioretention basin with a high-PRI soils.

6.5 Maintenance

The small scale of the development means that the requirements for maintenance of the drainage system will be minimal. The following maintenance may be required to ensure that the stormwater drainage system continues to function as designed:

Regular (possibly annual) cleaning of bubble-ups and inlet pits. More frequent cleaning may be required during the construction phase, when sediment loads in runoff are typically higher.

Tending and maintenance of the bioretention basin to remove litter, control weeds and encourage the growth of native species.

All maintenance of the drainage system will be carried out by the owner.


_____________________________________________________________________________________


7.0 GROUNDWATER MANAGEMENT

7.1 Groundwater Levels

Groundwater levels beneath the development area will not be affected by the development. No subsoil drainage is expected to be required beneath the building pad or bioretention basin.

There will be no need for dewatering for the installation of underground services. As a result there will be no impact on groundwater levels from construction activities.

7.2 Groundwater Quality

Development of the site is not expected to significantly change the quality of groundwater beneath the site. The main threats to water quality under urban development are lawn and garden fertilisers and road runoff. The contaminant of main concern is phosphorus.

Test pitting undertaken on Lot 10 and nearby indicates that the soil has a high to very high capacity to adsorb phosphorus. Therefore it is considered unlikely that any phosphorus will leach to the groundwater from the bioretention basin or landscaping areas. The bioretention basin will be densely vegetated in order to maximise its ability to take up nitrogen.

The aim of nutrient management will be to limit nutrient inputs to the site so that nutrient exports are maintained at or below current levels. Measures implemented to minimise nutrient inputs and exports in the development will include:

regular sweeping of the car parks to remove accumulated contaminants; and selection of species with low water and fertiliser requirements for landscaped areas.


_____________________________________________________________________________________


8.0 LANDSCAPING

The surrounds of the building and car park will be landscaped using trees, shrubs and groundcovers to partially screen the building from outside view and improve its aesthetics. The landscaping will feature local native species and will be carried out in accordance with the Shire of Mundaring’s Landscape and Revegetation Guidelines(2015).

Existing native trees will be retained wherever practical. Shrubs and sedges will be planted beneath the existing tree canopy to improve screening. The landscaping treatments to be applied to each part of the site are described below and shown on Figure 7.

8.1 Landscaping Zones

Fire Protection14m Asset Protection Zone (APZ) around building to give BAL -29. Restricted planting in APZ.

Native LandscapingArea (approx.): 1,931 m2.Planted with drought-tolerant sedges, herbs and low (


_____________________________________________________________________________________


Trees Marri Corymbia calophylla

Container size: Sedges & herbs 130mm Shrubs 150mm Trees 45L

Road VergesArea (approx.): 1,613m2.Infill planting with drought-tolerant sedges and low (


_____________________________________________________________________________________


White Myrtle Hypocalymma angustifoliumTrees

Moonah Paperbark Melaleuca preissiana Container size: Tube Stock

Garden Beds / Planter BoxesArea (approx.) 769m2

Planted with native low (


_____________________________________________________________________________________


CONSTRUCTION MANAGEMENT

The construction contractor will implement a Construction Management Plan for the development dealing with dust management, erosion and sediment control, containment of environmentally hazardous materials and spill response. The key elements of the Construction Management Plan will include the following:

Dust Minimisation No topsoil stripping will be undertaken in dry soil conditions when the wind speed is greater than 25km/h. No earthworks will be undertaken in dry soil conditions when the wind speed is greater than 40km/h. Dust will be suppressed on open ground and stockpiles by regular watering and/or wind fencing as required. An adequate supply of water for dust suppression will be kept on site at all times. Ground to be disturbed will be wet prior to soil disturbance. Soil stockpiles will be limited to a height of 2.5m to minimise dust generation and to facilitate watering. Other dust minimisation measures will include minimising areas of disturbance, limiting volume and speed of construction traffic, and instructing site workers in dust minimisation.

Erosion and Sedimentation The bioretention basin will be constructed at the first stage of site works to act as a sediment basin during the construction phase. Drains and bunds will be constructed as necessary to capture and direct all runoff from disturbed areas into the sediment basin prior to discharge. Vehicles and machinery will be kept to designated roads, tracks and work areas. Further details of erosion and sediment during construction are given in the Erosion and Sediment Control Plan (Chapter 5 of this report).

Water Conservation Water consumption during construction will be minimised by:

- limiting dust suppression watering to prevent ponding and runoff; and - use of non-water dust control methods such as wind fencing and hydromulching.

Hazardous MaterialsAll environmentally hazardous materials will be stored in their original labelled containers in a ventilated enclosure equipped with appropriate signage, fire extinguishers and a spill response kit. Petroleum products will not be stored on site. Material Safety Data Sheets (MSDS) and a chemical register for all hazardous materials on the site will be maintained by the site supervisor in the site office.

Complaints Register The site supervisor will maintain a record of any public complaints and the actions taken in response.


_____________________________________________________________________________________


9.0 IMPLEMENTATION

9.1 Responsibilities

The construction contractor’s site supervisor will be responsible for the construction of sediment and drainage controls including bunds, drains and the detention basin, and monitoring of their performance (see Section 9.2). The supervisor will also be responsible for ensuring proper practices on the site including adherence to the single point of access and restriction of soil disturbance to the construction site.

The project manager for the Mundaring Gospel Trust will be responsible for oversight of the construction contract, ensuring that the sediment control measures set out in this plan are implemented, and reporting as required to the Shire of Mundaring.

9.2 Monitoring

The construction contractor’s site supervisor will visually monitor the bunds, detention basin and downstream roadside drains each day when sufficient rainfall occurs to generate runoff from any part of the site. The monitoring will include:

performance and integrity of the bunds, drains, detention basin and overflow structures;occurrence and frequency of overflows from the basin; entry of overflows from the basin to the roadside drains; and visible sediments/turbidity in the roadside drains and Mahogany Creek upstream and downstream of the entry point of overflows from the site.

The site supervisor will keep a written record of the results of the monitoring. The monitoring records will be provided to the Project Manager and made available to the Shire of Mundaring on request.

9.3 Contingencies

The main adverse events that could occur during construction are a breach of the bunds or detention basin, or entry of excessive sediments to the roadside drains and hence Mahogany Creek.

If a breach of the detention basin or bunds occurs, most likely through scouring, the initial response will be to repair the breach and reinforce (by raising wall height and/or by hardening with concrete, stone pitching or similar) the affected section.


_____________________________________________________________________________________


If monitoring of the roadside drains shows that excessive sediment is reaching the drains or Mahogany Creek (detectable as a visible sediment plume in the creek), responses available will include:

increasing the size of the basin to provide longer detention times; cleaning out the basin to remove accumulated sediments and restore permeability; installing sediment fences on outflow paths below the basin; and installing additional sediment controls within the site including sediment fences, bunds, straw bales and mulching.


_____________________________________________________________________________________


10.0 REFERENCES

Churchward H.M. and W.M. McArthur (1980). Landforms and Soils of the Darling System, Western Australia. In Atlas of Natural Resources: Darling System, Western Australia. Dept of Conservation & Environment, Perth.

DoE (2004). Stormwater Management Manual for Western Australia. Department of Environment, Perth.

EMRC (2008). Erosion and Sediment Control Guidelines for the Shire of Mundaring.Eastern Metropolitan Regional Council, Belmont.

Engineers Australia (1987). Australian Rainfall and Runoff: A Guide to Flood Estimation.Institution of Engineers, Australia, Barton, ACT.

Government of Western Australia (2003). Health Act 1911: Health (Treatment of Sewage and Disposal of Effluent and Liquid Waste) Regulations 1974.

Health Department of Western Australia (2001). Code of Practice for the Design, Manufacture, Installation and Operation of Aerobic Treatment Units (ATUs).Health Department of WA, Perth.

Heddle E.M., Loneragan O.W. and Havel J.J. (1980). Vegetation Complexes of the Darling System, Western Australia. In: Atlas of Natural Resources Darling System, Western Australia. Department of Conservation and Environment, Perth.

King P.D. and M.R. Wells (1990). Darling Range Rural Land Capability Study. Land Resources Series No. 3. Department of Agriculture, Perth.

Lloyd B. and van Delft R. (eds) (2001). Erosion and Sediment Control Manual for the Darling Range, Perth, Western Australia. Upper Canning/Southern Wungong Catchment Team, Perth.

Shire of Mundaring (2015). Landscape & Revegetation Guidelines. Shire of Mundaring.

Smurthwaite A.J. (1986). 1:50,000 Environmental Geology Series: Mundaring Part Sheets 2134 II & 2134 III. Geological Survey of Western Australia, Perth.

Standards Australia (2012). Australian/New Zealand Standard 1547:2012 – On-site Domestic Wastewater Management. SAI Global Ltd, Sydney.

_

Figures

Figu

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Appendix A

Soil Logs

J19004

PT1

418662

6470721

5-tonne excavator

2.0

N

16/04/2019

Not encountered

DEPTH (m) SAMPLE ID INTERVAL (m)

0 - 0.1

0.1 - 2.0

SOIL PROFILE SAMPLE DATA

DEPTH TO WATER (mbgl)

SOIL DESCRIPTION

Grey-brown topsoil

Yellow-brown gravelly clay-loam with common laterite boulders to 1m

REFUSAL (Y/N):

DATE:

SOIL PROFILE LOG

PROJECT NUMBER:

SITE ID:

METHOD:

TOTAL DEPTH (mbgl):

EASTING:

NORTHING:

J19004

PT2

418666

6470765

5-tonne excavator

2.2

N

16/04/2019

Not encountered


0 - 0.1

0.1 - 0.6

0.6 - 1.7

1.7 - 2.2

REFUSAL (Y/N):

DATE:

SOIL PROFILE LOG

PROJECT NUMBER:

SITE ID:

METHOD:

TOTAL DEPTH (mbgl):

EASTING:

NORTHING:


Orange/brown mottled lateritic clay with laterite cobbles to 100mm

SOIL DESCRIPTION

Grey-brown sandy topsoil

Yellow-brown gravelly loam with laterite stones to 30mm

Orange/yellow mottled loamy clay, moderately structured with laterite stones to 50mm


J19004

PT3

418611

6470770

5-tonne excavator

2.3

N

16/04/2019

Not encountered


0 - 0.1

0.1 - 0.6

0.6 - 2.3



SOIL DESCRIPTION


Yellow-brown gravelly loam with laterite stones to 30mm

Yellow-brown lateritic sandy clay with occasional orange mottles, well structured

REFUSAL (Y/N):

DATE:

SOIL PROFILE LOG

PROJECT NUMBER:

SITE ID:

METHOD:

TOTAL DEPTH (mbgl):

EASTING:

NORTHING:

J19004

PT4

418609

6470725

5-tonne excavator

2.6

N

16/04/2019

Not encountered


0 - 0.15

0.15 - 0.4

0.4 - 1.2

1.2 - 2.6

REFUSAL (Y/N):

DATE:

SOIL PROFILE LOG

PROJECT NUMBER:

SITE ID:

METHOD:

TOTAL DEPTH (mbgl):

EASTING:

NORTHING:


White sandy clay, soft and well structured with red mottles

SOIL DESCRIPTION


Yellow-brown gravelly loam

Yellow/orange mottled loamy clay


J19004

PT5

418537

6470747

5-tonne excavator

2.2

N

16/04/2019

Not encountered


0 - 0.15

0.15 - 0.5

0.5 - 2.2



SOIL DESCRIPTION


Pale yellow-brown sandy gravelly loam

Red/orange/yellow mottled lateritic sandy clay

REFUSAL (Y/N):

DATE:

SOIL PROFILE LOG

PROJECT NUMBER:

SITE ID:

METHOD:

TOTAL DEPTH (mbgl):

EASTING:

NORTHING:

J19004

PT6

418560

6470733

5-tonne excavator

2.4

N

16/04/2019

Not encountered


0 - 0.1

0.1 - 0.5

0.5 - 2.4

REFUSAL (Y/N):

DATE:

SOIL PROFILE LOG

PROJECT NUMBER:

SITE ID:

METHOD:

TOTAL DEPTH (mbgl):

EASTING:

NORTHING:


SOIL DESCRIPTION


Yellow-brown gravelly loam

Orange/brown mottled lateritic sandy clay, becoming harder below 1.3m


J19004

PT7

418624

6470753

5-tonne excavator

2.5

N

16/04/2019

Not encountered


0 - 0.1

0.1 - 0.7

0.7 - 1.6

1.6 - 2.5



White soft, well structured sandy clay with occasional red mottles

SOIL DESCRIPTION

Grey sandy topsoil

Yellow-brown gravelly sandy clay-loam

Orange/brown mottled loamy clay

REFUSAL (Y/N):

DATE:

SOIL PROFILE LOG

PROJECT NUMBER:

SITE ID:

METHOD:

TOTAL DEPTH (mbgl):

EASTING:

NORTHING:

Appendix B

Permeability Test Results

SOIL

PER

MEA

BIL

ITY

TEST

Site

No.

PI1

Dat

e16

/04/

19Ea

stin

g41

8663

Nor

thin

g64

7072

8D

epth

0.5

Tim

e (h

:m:s

)W

eigh

t (kg

)C

hang

e in

W

eigh

t (kg

)K

s (m

/d)

09:0

3:30

37.8

09:0

5:30

35.5

2.3

9.68

H =

2509

:07:

3033

.61.

97.

99r

=4.

509

:10:

0031

.12.

58.

4109

:12:

0029

.31.

87.

5709

:14:

0027

.32

8.41

#NU

M!

#DIV

/0!

#DIV

/0!

#DIV

/0!

#DIV

/0!

#DIV

/0!

#DIV

/0!

#DIV

/0!

#DIV

/0!

#DIV

/0!

#DIV

/0!

#DIV

/0!

#DIV

/0!

#DIV

/0!

#DIV

/0!

#DIV

/0!

#DIV

/0!

#DIV

/0!

#DIV

/0!

Ks

=8

m/d

ay

0.00

2.00

4.00

6.00

8.00

10.0

0

12.0

0 09:0

509

:07

09:0

909

:11

09:1

3

Tim

e (h

:m:s

)

Ks (m/day)

SOIL

PER

MEA

BIL

ITY

TEST

Site

No.

PI2

Dat

e16

/04/

19Ea

stin

g41

8559

Nor

thin

g64

7073

1D

epth

0.5

Tim

e (h

:m:s

)W

eigh

t (kg

)C

hang

e in

W

eigh

t (kg

)K

s (m

/d)

11:2

5:00

26.1

11:2

7:00

24.8

1.3

5.47

H =

2511

:29:

0021

.43.

414

.30

r =

4.5

11:3

1:00

19.7

1.7

7.15

11:3

3:00

17.6

2.1

8.83

11:3

5:00

15.6

28.

4111

:37:

0013

.62

8.41

#NU

M!

#DIV

/0!

#DIV

/0!

#DIV

/0!

#DIV

/0!

#DIV

/0!

#DIV

/0!

#DIV

/0!

#DIV

/0!

#DIV

/0!

#DIV

/0!

#DIV

/0!

#DIV

/0!

#DIV

/0!

#DIV

/0!

#DIV

/0!

#DIV

/0!

#DIV

/0!

Ks

=8

m/d

ay

0.00

2.00

4.00

6.00

8.00

10.0

0

12.0

0

14.0

0

16.0

0 11:2

711

:29

11:3

111

:33

11:3

511

:37

Tim

e (h

:m:s

)

Ks (m/day)

SOIL

PER

MEA

BIL

ITY

TEST

Site

No.

PI3

Dat

e16

/04/

19Ea

stin

g41

8638

Nor

thin

g64

7071

9D

epth

0.5

Tim

e (h

:m:s

)W

eigh

t (kg

)C

hang

e in

W

eigh

t (kg

)K

s (m

/d)

01:4

6:00

34.9

01:4

8:00

32.8

2.1

8.83

H =

2501

:50:

0030

.72.

18.

83r

=4.

501

:52:

0029

.11.

66.

7301

:54:

0027

.21.

97.

9901

:56:

0025

.71.

56.

3101

:58:

0023

.91.

87.

5702

:00:

0022

.51.

45.

8902

:02:

0020

.91.

66.

7302

:04:

0019

.41.

56.

3102

:06:

0017

.81.

66.

7317

.8#N

UM

!#D

IV/0

!#D

IV/0

!#D

IV/0

!#D

IV/0

!#D

IV/0

!#D

IV/0

!#D

IV/0

!#D

IV/0

!#D

IV/0

!#D

IV/0

!#D

IV/0

!#D

IV/0

!#D

IV/0

!

Ks

=6.

5m

/day

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

9.00

10.0

0 01:4

801

:50

01:5

201

:54

01:5

601

:58

02:0

002

:02

02:0

402

:06

Tim

e (h

:m:s

)

Ks (m/day)

SOIL

PER

MEA

BIL

ITY

TEST

Site

No.

PI4

Dat

e16

/04/

19Ea

stin

g41

8552

Nor

thin

g64

7075

7D

epth

0.5

Tim

e (h

:m:s

)W

eigh

t (kg

)C

hang

e in

W

eigh

t (kg

)K

s (m

/d)

02:4

6:00

31.2

02:4

8:00

26.6

4.6

14.8

7H

=25

02:5

0:00

21.7

4.9

15.8

4r

=6.

502

:53:

0014

.37.

415

.95

02:5

5:00

9.7

4.6

14.8

7#N

UM

!#D

IV/0

!#D

IV/0

!#D

IV/0

!#D

IV/0

!#D

IV/0

!#D

IV/0

!#D

IV/0

!#D

IV/0

!#D

IV/0

!#D

IV/0

!#D

IV/0

!#D

IV/0

!#D

IV/0

!#D

IV/0

!#D

IV/0

!#D

IV/0

!#D

IV/0

!#D

IV/0

!#D

IV/0

!

Ks

=14

m/d

ay

0.00

2.00

4.00

6.00

8.00

10.0

0

12.0

0

14.0

0

16.0

0

18.0

0 02:4

802

:50

02:5

202

:54

Tim

e (h

:m:s

)

Ks (m/day)

Appendix C

Effluent Flows and System Sizing

EFFL

UEN

T G

ENER

ATI

ON

Popu

latio

nEf

fluen

t lpd

Wor

ship

pers

490

1049

00M

ax d

aily

flow

(with

hol

ding

tank

)21

70Si

te a

rea

2.02

34ha

2170

= R

2.0

SEPT

IC T

AN

K S

IZIN

GA

llow

ance

Volu

me

Res

erve

cap

acity

1820

Wor

ship

pers

490

1049

0067

20

LEA

CH

DR

AIN

SIZ

ING

- W

ITH

SEP

TIC

IRR

IGA

TIO

N A

REA

SIZ

ING

DLR

15m

m/d

ayD

IR5

mm

/day

Leac

h dr

ain

effe

ctiv

e w

idth

1.6

m

Area

requ

ired

434

m2

Efflu

ent p

er m

24lit

res/

day

Leng

th o

f LD

requ

ired

90m

(

4.5

x 20

m o

r10

x

9.0

m)

Tota

l wid

th -

para

llel

33.6

mTo

tal w

idth

- en

d to

end

/par

alle

l15

.6m

Tota

l are

a - p

aral

lel

324

m2

Tota

l are

a - e

nd to

end

/par

alle

l30

7m

2

LEA

CH

DR

AIN

SIZ

ING

- W

ITH

ATU

DLR

25m

m/d

ayLe

ach

drai

n ef

fect

ive

wid

th1.

6Ef

fluen

t per

m40

Leng

th o

f LD

requ

ired

54m

(

2.7

x 20

m o

r4.

0x

13

.6m

)To

tal w

idth

- pa

ralle

l12

.0m

Tota

l wid

th -

end

to e

nd/p

aral

lel

4.8

mTo

tal a

rea

- par

alle

l17

0m

2To

tal a

rea

- end

to e

nd/p

aral

lel

138

m2

Sun

day

Mon

day

Tues

day

Wed

nesd

ayTh

ursd

ayFr

iday

Sat

urda

yS

unda

yM

onda

yTu

esda

yW

edne

sday

Thur

sday

Frid

ayS

atur

day

Wor

ship

pers

190

4012

025

025

012

025

049

040

120

250

250

120

120

Dai

ly e

fflue

nt g

ener

atio

n pe

r per

son

Tota

l19

040

120

250

250

120

250

490

4012

025

025

012

012

010

Efflu

ent f

low

1900

400

1200

2500

2500

1200

2500

4900

400

1200

2500

2500

1200

1200

Max

dai

ly fl

ow (n

omin

ally

Cum

ulat

ive

Efflu

ent

1900

400

1200

2500

2830

1860

2500

5230

3460

2490

2820

3150

2180

1210

fallin

g on

2nd

Sun

day)

490

Leac

h D

rain

Flo

w19

0040

012

0021

7021

7018

6021

7021

7021

7021

7021

7021

7021

7012

10St

orag

e0

00

330

660

033

030

6012

9032

065

098

010

0

Max

thr

ough

put

2170

Max

sto

rage

3460

WD

V1.

541.

863.

46

0

500

1000

1500

2000

2500

3000

3500

Sund

ayTu

esda

yTh

ursd

aySa

turd

ayM

onda

yW

edne

sday

Frid

ay

Day

Storage

Appendix D

Runoff Calculations and Basin Sizing

1 YE

AR

AR

I 1 H

OU

R F

LOW

S - P

RE

& P

OST

DEV

ELO

PMEN

T

Rai

nfal

l Int

ensi

ty i

(mm

/h)

16.1

(1 Y

r, 1

Hr S

torm

)C

r Roa

d &

carp

ark

0.9

http

s://w

ww

.mel

bour

new

ater

.com

.au/

plan

ning

-and

-bui

ldin

g/de

velo

per-g

uide

s-an

d-re

sour

ces/

stan

dard

s-an

d-sp

ecifi

catio

ns/h

ydro

logi

c-an

dC

r Bui

ldin

g &

Surro

unds

0.9

Cr B

asin

1C

r Lan

dsca

ping

0

Perm

eabi

lity

k (m

/hr)

0.08

33

Cat

chm

ent

Roa

d &

car

park

Bui

ldin

g &

Su

rrou

nds

Bas

inLa

ndsc

apin

gA

iQ

(L/s

)Vi

nflo

w (m

3)

A62

1414

3936

672

53.7

032

.47

117

Bas

in S

izin

gSt

orm

Eve

ntD

epth

Slop

e 1:

xB

ase

Wid

thB

ase

Leng

thTo

p W

idth

(m

)To

p Le

ngth

(m

)Vo

lum

eEf

fect

ive

Volu

me

Surf

ace

Are

a (m

2)Vo

lum

ech

eck

2% A

rea

Basi

n1

0.54

43.

035

.07.

339

.310

211

828

8ok

153

5 YE

AR

AR

I DR

AIN

AG

E PR

OPE

RTI

ES -

PRE

& P

OST

DEV

ELO

PMEN

T

CA

TCH

MEN

TC

RIT

ICA

L ST

OR

M IN

TEN

SITY

(mm

/h)

Roa

d &

ca

rpar

kB

uild

ing

&

Surr

ound

sG

rass

Land

scap

ing

Tota

lPr

e-D

evPo

st-D

evLo

nges

t Pa

th (m

)R

L To

p (m

AH

D)

RL

Bot

tom

(m

AH

D)

Slop

e(m

/km

)TC

(min

)Lo

nges

t Pa

th (m

)R

L To

p (m

AH

D)

RL

Bot

tom

(m

AH

D)

Slop

eTC

(min

)Pr

e-D

evPo

st-D

ev

A62

1414

3936

60

8019

2406

7254

145

273

267

39.3

17.

412

427

226

740

.32

5.6

88.1

397

.64

Run

off C

oeffi

cien

tsPr

e-D

evPo

st-D

evht

tps:

//ww

w.m

elbo

urne

wat

er.c

om.a

u/pl

anni

ng-a

nd-b

uild

ing/

deve

lope

r-gui

des-

and-

reso

urce

s/st

anda

rds-

and-

spec

ifica

tions

/hyd

rolo

gic-

and

Roa

d &

carp

ark

0.3

0.9

Build

ing

& Su

rroun

ds0.

30.

9Ba

sin

0.3

1La

ndsc

ape

0.3

0

Rai

nfal

l IFD

Even

tD

urat

ion

(min

s)In

tens

ity(m

m/h

r)5

min

510

110

min

1073

.920

min

2050

.130

min

3039

.11

hr60

25.3

2 hr

120

16.4

3 hr

180

12.9

6 hr

360

8.49

12 h

r72

05.

5824

hr

1440

3.56

48 h

r28

802.

1972

hr

4320

1.62

TIM

E O

F C

ON

CEN

TRA

TIO

N P

OST

-DEV

ELO

PMEN

TEF

FEC

TIVE

AR

EAS

(m2)

TIM

E O

F C

ON

CEN

TRA

TIO

N P

RE-

DEV

ELO

PMEN

TA

REA

S (m

2)

5 YE

AR

AR

I FLO

WS

- PR

E &

PO

ST D

EVEL

OPM

ENT

Stor

m D

urat

ion

(min

s)Pr

e-D

evFl

ow (l

/s)

Post

-Dev

Flow

(l/s

)Ex

cess

Flow

(l/s

)St

orag

e(m

3)5

58.8

920

3.51

144.

6229

.28

1058

.89

148.

9090

.01

42.0

020

58.8

910

0.95

42.0

642

.20

3058

.89

78.7

819

.89

30.7

960

58.8

950

.98

-7.9

1-2

5.41

120

58.8

933

.04

-25.

85-1

70.5

618

058

.89

25.9

9-3

2.90

-330

.17

360

58.8

917

.11

-41.

78-8

54.0

472

058

.89

11.2

4-4

7.65

-197

4.22

1440

58.8

97.

17-5

1.72

-432

5.24

2880

58.8

94.

41-5

4.48

-916

8.67

4320

58.8

93.

26-5

5.63

-140

80.0

2

Perm

eabi

lity

0.08

33m

/hr

Bas

in S

izin

gSt

orm

Even

tD

epth

Slop

e 1:

xB

ase

Wid

thB

ase

Leng

thTo

p W

idth

(m

)To

p Le

ngth

(m

)Vo

lum

eEf

fect

ive

Volu

me

Surf

ace

Are

a (m

2)Vo

lum

ech

eck

Basin

A5

0.28

43

355

3741

4519

5ok

Cat

chm

ent A

100

YEA

R A

RI D

RA

INA

GE

PRO

PER

TIES

- PR

E &

PO

ST D

EVEL

OPM

ENT

CA

TCH

MEN

TR

oad

&

carp

ark

Bui

ldin

g &

Su

rrou

nds

Bas

inLa

ndsc

apin

gTo

tal

Pre

Post

Long

est

Path

(m)

RL

Top

(mA

HD

)R

L B

otto

m

(mA

HD

)Sl

ope

(m/k

m)

TC (m

in)

Long

est

Path

(m)

RL

Top

(mA

HD

)R

L B

otto

m

(mA

HD

)Sl

ope

TC (m

in)

Pre-

Dev

Post

-Dev

A62

1414

3936

60

8019

1604

7398

145

273

267

39.3

17.

712

427

226

740

.32

5.6

173.

3719

7.82

Run

off C

oeffi

cien

tsPr

e-D

evPo

st-D

evht

tps:

//ww

w.m

elbo

urne

wat

er.c

om.a

u/pl

anni

ng-a

nd-b

uild

ing/

deve

lope

r-gui

des-

and-

reso

urce

s/st

anda

rds-

and-

spec

ifica

tions

/hyd

rolo

gic-

and

Roa

d &

carp

ark

0.3

0.9

Build

ing

& Su

rroun

ds0.

31

Basi

n0.

31

Land

scap

e0.

20.

2

Rai

nfal

l IFD

Even

tD

urat

ion

(min

s)In

tens

ity(m

m/h

r)5

min

520

510

min

1014

620

min

2094

.630

min

3072

1 hr

6044

.82

hr12

027

.83

hr18

021

.16

hr36

013

.312

hr

720

8.52

24 h

r14

405.

5148

hr

2880

3.53

72 h

r43

202.

66

AR

EAS

(m2)

CR

ITIC

AL

STO

RM

INTE

NSI

TY (m

m/h

)EF

FEC

TIVE

AR

EAS

(m2)

TIM

E O

F C

ON

CEN

TRA

TIO

N P

RE

DEV

ELO

PMEN

TTI

ME

OF

CO

NC

ENTR

ATI

ON

PO

ST-D

EVEL

OPM

ENT

100

YEA

R A

RI F

LOW

S - P

RE

& P

OST

DEV

ELO

PMEN

T

Stor

m D

urat

ion

(min

s)Pr

e-D

evFl

ow (l

/s)

Post

-Dev

Flow

(l/s

)Ex

cess

Flow

(l/s

)St

orag

e(m

3)5

77.2

442

1.25

344.

0181

.98

1077

.24

300.

0122

2.78

114.

3720

77.2

419

4.39

117.

1612

4.92

3077

.24

147.

9570

.71

114.

8660

77.2

492

.06

14.8

249

.17

120

77.2

457

.13

-20.

11-1

35.6

518

077

.24

43.3

6-3

3.88

-345

.59

360

77.2

427

.33

-49.

91-1

030.

5472

077

.24

17.5

1-5

9.73

-249

1.65

1440

77.2

411

.32

-65.

91-5

543.

7428

8077

.24

7.25

-69.

98-1

1842

.41

4320

77.2

45.

47-7

1.77

-182

61.8

6

Perm

eabi

lity

0.08

33m

/hr

Bas

in S

izin

gSt

orm

Even

tD

epth

Slop

e 1:

xB

ase

Wid

thB

ase

Leng

thTo

p W

idth

(m

)To

p Le

ngth

(m

)Vo

lum

eEf

fect

ive

Volu

me

Surf

ace

Are

a (m

2)Vo

lum

ech

eck

Basin

A10

00.

614

335

840

122

128

314

ok

Cat

chm

ent A

proposed place of worship 295 (lot 10 ......figure 4 shows the gswa mapping. test pitting at seven...

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