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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
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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
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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
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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
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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.
Proposed Place of Worship, 295 (Lot 10) Seaborne St, Parkerville – Environmental Assessment Page 17 ______________________________________________________________________________________
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BAYLEY ENVIRONMENTAL SERVICES
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.
Proposed Place of Worship, 295 (Lot 10) Seaborne St, Parkerville – Environmental Assessment Page 18 ______________________________________________________________________________________
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BAYLEY ENVIRONMENTAL SERVICES
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.
Proposed Place of Worship, 295 (Lot 10) Seaborne St, Parkerville – Environmental Assessment Page 19 ______________________________________________________________________________________
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BAYLEY ENVIRONMENTAL SERVICES
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.
Proposed Place of Worship, 295 (Lot 10) Seaborne St, Parkerville – Environmental Assessment Page 20 ______________________________________________________________________________________
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BAYLEY ENVIRONMENTAL SERVICES
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 (
Proposed Place of Worship, 295 (Lot 10) Seaborne St, Parkerville – Environmental Assessment Page 21 ______________________________________________________________________________________
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BAYLEY ENVIRONMENTAL SERVICES
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 (
Proposed Place of Worship, 295 (Lot 10) Seaborne St, Parkerville – Environmental Assessment Page 22 ______________________________________________________________________________________
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BAYLEY ENVIRONMENTAL SERVICES
White Myrtle Hypocalymma angustifoliumTrees
Moonah Paperbark Melaleuca preissiana Container size: Tube Stock
Garden Beds / Planter BoxesArea (approx.) 769m2
Planted with native low (
Proposed Place of Worship, 295 (Lot 10) Seaborne St, Parkerville – Environmental Assessment Page 23 ______________________________________________________________________________________
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BAYLEY ENVIRONMENTAL SERVICES
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.
Proposed Place of Worship, 295 (Lot 10) Seaborne St, Parkerville – Environmental Assessment Page 24 ______________________________________________________________________________________
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BAYLEY ENVIRONMENTAL SERVICES
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.
Proposed Place of Worship, 295 (Lot 10) Seaborne St, Parkerville – Environmental Assessment Page 25 ______________________________________________________________________________________
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BAYLEY ENVIRONMENTAL SERVICES
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.
Proposed Place of Worship, 295 (Lot 10) Seaborne St, Parkerville – Environmental Assessment Page 26 ______________________________________________________________________________________
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BAYLEY ENVIRONMENTAL SERVICES
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
re 1
OB
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268
266
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274
276
270
050
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re 2
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PT5
PT4
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PI2
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re 4
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re 6
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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
DEPTH (m) SAMPLE ID INTERVAL (m)
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:
DEPTH TO WATER (mbgl)
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
SOIL PROFILE SAMPLE DATA
J19004
PT3
418611
6470770
5-tonne excavator
2.3
N
16/04/2019
Not encountered
DEPTH (m) SAMPLE ID INTERVAL (m)
0 - 0.1
0.1 - 0.6
0.6 - 2.3
SOIL PROFILE SAMPLE DATA
DEPTH TO WATER (mbgl)
SOIL DESCRIPTION
Grey-brown sandy topsoil
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
DEPTH (m) SAMPLE ID INTERVAL (m)
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:
DEPTH TO WATER (mbgl)
White sandy clay, soft and well structured with red mottles
SOIL DESCRIPTION
Grey-brown sandy topsoil
Yellow-brown gravelly loam
Yellow/orange mottled loamy clay
SOIL PROFILE SAMPLE DATA
J19004
PT5
418537
6470747
5-tonne excavator
2.2
N
16/04/2019
Not encountered
DEPTH (m) SAMPLE ID INTERVAL (m)
0 - 0.15
0.15 - 0.5
0.5 - 2.2
SOIL PROFILE SAMPLE DATA
DEPTH TO WATER (mbgl)
SOIL DESCRIPTION
Grey-brown sandy topsoil
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
DEPTH (m) SAMPLE ID INTERVAL (m)
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:
DEPTH TO WATER (mbgl)
SOIL DESCRIPTION
Grey-brown sandy topsoil
Yellow-brown gravelly loam
Orange/brown mottled lateritic sandy clay, becoming harder below 1.3m
SOIL PROFILE SAMPLE DATA
J19004
PT7
418624
6470753
5-tonne excavator
2.5
N
16/04/2019
Not encountered
DEPTH (m) SAMPLE ID INTERVAL (m)
0 - 0.1
0.1 - 0.7
0.7 - 1.6
1.6 - 2.5
SOIL PROFILE SAMPLE DATA
DEPTH TO WATER (mbgl)
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