Lake Bennett Bungalows Review of Wastewater Treatment Facilities 14 October 2019 Revision 2 Job No: 18DA0418 Melbourne Office L3 289 Wellington Parade South EAST MELBOURNE VIC 3002 t +613 9622 9700 mlb@irwinconsult.com.au ABN 89 050 214 894 Bendigo Office L1 133 McCrae Street BENDIGO VIC 3550 t +613 5442 6333 bgo@irwinconsult.com.au Darwin Office 82 Smith Street DARWIN NT 0800 t +618 8980 5900 drw@irwinconsult.com.au Directors Joe Bruno, Phil Gardiner Peter Hale, Barry Roben, Dean Whiteley Member Green Building Council Australia www.irwinconsult.com.au 18DA0418 - Bungalow 20191014 - Review of Waste Water Treatment Facilities - Rev 2.docx JT 14/10/19 Document Control Project Title: Lake Bennett Bungalows – Review of Waste Water Treatment Facilities Project No: 18DA0418 Revision Date 0 01/04/2019 1 04/07/2019 2 14/10/2019 File name 18DA0418\Correspondence\Reports\Review of Waste Water Treatment Facilities Prepared Checked Approved Initial MM SW NWC Date 18DA0418\Correspondence\Reports\Review of Waste Water Treatment Facilities Description Revision 1 Prepared Checked Approved Initial MM SW NWC Date Prepared Checked Approved Initial Date 18DA0418\Correspondence\Reports\Review of Waste Water Treatment Facilities Description Revision 2 Prepared Checked Approved Initial MM SW NWC Date 14/10/2019 14/10/2019 14/10/2019 File name Description Prepared Checked Approved Initial Date Report checked by Certifying Engineer (Hydraulic) Simon Watkins (Reg No. 18235EH) Irwinconsult has prepared this report with the following conditions:  The report may only be used by the client for the purpose for which it was commissioned.  The report may only be reproduced in full.  The report shall not be considered as relieving any other party of their responsibilities, liabilities or contractual obligations.  The report addresses the engineering disciplines noted within only.  The report does not address the presence of asbestos or other contaminative materials. Review of Waste Water Treatment Facilities to Lake Bennett Resort 18DA0418 - Bungalow 20191014 - Review of Waste Water Treatment Facilities Rev 2.docx JT 14/10/19 Page 2 of 28 Contents 1 Executive Summary ......................................................................... 4 1.1 1.2 1.3 Scope of Requirements .............................................................................. 4 Objectives .................................................................................................... 4 Findings ....................................................................................................... 6 1.3.1 1.3.2 1.4 2 Configuration ......................................................................................................... 6 Assessment ............................................................................................................ 6 Recommendations ...................................................................................... 7 Background ....................................................................................... 8 2.1.1 2.1.2 2.2 Assessment of Disposal Area .................................................................... 9 2.2.1 2.2.2 2.2.3 3 Septic tank capacities for residential domestic premises Class 1 and Class 10. 8 Current Facilities/Configuration ........................................................................... 8 Absorption Disposal Area .................................................................................... 9 Existing Disposal Installation ............................................................................... 9 Assessment of Current Required Disposal Area ............................................... 9 Existing Infrastructure ................................................................... 10 3.1 3.2 3.3 3.4 3.5 Existing Septic Tanks ............................................................................... 10 Existing Lift Well ....................................................................................... 13 Rising Sewer Main ..................................................................................... 16 Effluent Disposal Area .............................................................................. 18 Distribution Chamber ................................................................................ 23 4 Review of Waste Water Treatment Facilities ............................... 26 5 Findings ........................................................................................... 27 6 Recommendations ......................................................................... 28 APPENDIX A WIGG PLUMBING REPORT APPENDIX B DOUGLAS & PARTNERS GEOTECHNICAL REPORT APPENDIX C SCHEMATIC DRAWING OF OSWM LAYOUT Review of Waste Water Treatment Facilities to Lake Bennett Resort 18DA0418 - Bungalow 20191014 - Review of Waste Water Treatment Facilities Rev 2.docx JT 14/10/19 Page 3 of 28 1 Executive Summary 1.1 Scope of Requirements Irwinconsult, as Certifying Engineer (Hydraulic), have been commissioned by the Department of Health to undertake a site survey of the Lake Bennett Bungalows On-site Wastewater Management System (OSWM); and to prepare a report for the OSWM confirming whether it is fit for purpose, poses a public health risk and complies with the Code of Practice for OSWM including the provisions of solutions to overcome any identified non-compliant issues with the Code. 1.2 Objectives The following briefing requirements form a basis for this report: The Certifying Engineer is required to undertake the following at the Bungalows: • A site survey of the OSWM system: - Determine the compliance of the OSWM system as installed; - Verify the capacity of the land application area by conducting a site-and-soil evaluation; and - Provide solutions to overcome any identified non-compliant issues with “the Code” of Practice for On-site Wastewater Management. It is proposed that the site survey of the OSWM system be undertaken by: • Certifying Engineer (Hydraulic) experienced in OSWM design and installation including producing “as constructed” plans and following up with drawings and specifications for proposed alternative solutions if required. • Certifying Plumber and Drainer engaged by the Certifying Engineer (Hydraulic) with the capacity and professional capability to undertake a survey of an OSWM, which includes: • - Counting and quantifying the hydraulic flow from the installed fixtures. - Locating and exposing and ensuring by camera the soundness of the sewage pipes, to conduct the effluent to its’ collection. - Locating the septic tanks and calculating their capacity to accommodate the hydraulic load for a minimum of 24 hours and the corresponding emergency storage. - Measuring pump/holding tanks and calculating their capacity to accommodate daily flow and emergency storage. - Assessing trade waste management. - Testing soundness of high pressure pump lines. - Surveying the land application dispersal system for performance and capacity. Site and Soil Evaluator engaged by the Certifying Engineer (Hydraulic) to analyse the land capability (including long term acceptance rates LTAR) of the land application areas, providing the survey team with a basis for calculating the size of the dispersal area for both the current installations and re-calculate on expanded occupancy. Review of Waste Water Treatment Facilities to Lake Bennett Resort 18DA0418 - Bungalow 20191014 - Review of Waste Water Treatment Facilities Rev 2.docx JT 14/10/19 Page 4 of 28 Following from this, prepare a detailed report that: a. Identifies any public or environmental health issues from the site survey including any leaks, deficit or condition relating to the OSWM system which impacts on its efficiency, effectiveness, safety, performance; Commentary: The system is grossly undersized. Effluent flowing through the system to the absorption trenches would almost be raw sewer during high occupancy rate of the Bungalows. Ground water entering the system is also adding considerable loading to the system. b. Provides scaled ‘as-constructed’ plans showing the layout of the entire OSWM system; Commentary: Refer to Appendix C c. Provides specifications and photos of the current OSWM system including daily hydraulic flow, nutrient loading, capacity of any septic tanks or pump wells, distribution boxes, inspection openings, stormwater management, and design and capacity of land application area; Commentary: Refer to Section 3.2 and Wigg Plumbing Report in Appendix A d. Confirms that the current OSWM system has sufficient capacity, treatment and disposal capabilities to service the maximum number of residents and visitors using the Bungalows without posing a risk to public health; Commentary: Refer to Section 2.2.3 e. Confirms any greywater reuse or disposal on-site, and if so then advise how it is managed; Commentary: Refer to Section 3.3 f. Provides comment on the Water Management Plan (prepared by the proprietor) in reference to disposal of wastewater; Commentary: Not applicable to the Bungalows. g. Evaluates the performance of the current OSWM system detailing any works required to ensure compliance with the Code, AS/NZS3500.2.2015, AS/NZS 1546.1.2008, AS/NZS 1547.2012, and manufacturers requirements; Commentary: This is addressed throughout the report. h. Provides recommendations for a maintenance and servicing program for the OSWM system; and Commentary: As the existing OSWM system is grossly undersized any required maintenance and servicing requirements will not resolve the underlying issue. i. Provides evidence that the OSWM system can manage trade waste generated by the Resort. Commentary: Trade waste not applicable. Review of Waste Water Treatment Facilities to Lake Bennett Resort 18DA0418 - Bungalow 20191014 - Review of Waste Water Treatment Facilities Rev 2.docx JT 14/10/19 Page 5 of 28 1.3 Findings Based on investigative inspections of the existing OSWM system, it is the opinion of this report that the current OSWM system is substantially undersized for the Bungalows when fully occupied. The effluent disposal system does not meet the minimum site assessment criteria. It is also the opinion that the absorption trenches are substantially undersized and not operating efficiently as the trenches were over flowing with effluent water on one of the site inspections. 1.3.1 Configuration The current OSWM system servicing 65 Bungalows comprising 1, 2 and 3 bedrooms configurations is 1 X 18,000 litre, 2 X 6,000 litre and 1 X 3,000 litre septic tanks (1 X 3000 L Tank bypassed) and 5 lift wells associated with the septic tanks, and 1 transfer lift well. The largest septic tank which is located near the causeway and adjacent to the access road to Bungalows 17 through to Bungalow 59. It is approximately 4.5m below surface level (top of tank). The tank is approximately 2.4 metres in diameter and 6.0 metres in length, the effluent level within the tank was measured at 2 metres. The tank appears to be fabricated from precast concrete and has an effective capacity of approximately 18000 litres. Bungalows 17 through to 59 discharge sewer into a common sewer main (DN150) which runs parallel / adjacent to the access road servicing the Bungalows. At the time of inspection it was noted that ground water was entering the sewer chamber through the joints in the precast segments. For context, this arrangement is indicated on sketch schematic in Appendix C. The 6000 litre septic tanks are located on the opposite side of the causeway servicing Bungalows 1 through to 16. The twin precast concrete septic tanks discharge to a precast concrete lift well (Pump Pit No. 2) which pumps the effluent waste across the cause way to the larger septic tank. The discharge of the effluent sewer rising main is located within one of the access points to the septic tank. The 2 x 3000 litre septic tanks located adjacent to Bungalows 75, 76, 79 & 80 only one of the tanks is servicing the Bungalows. This system originally was 2 Aqua Treat systems that has been modified into a septic and pump well (Pump Pit No. 5). Based on our investigation (Wigg Plumbing) it appears based on the CCTV investigation of the drainage system one of the systems has been bypassed / decommissioned and all effluent is discharging into the septic adjacent to Bungalow 76. The effluent from this system is pumped to a transfer pump station (Pump Pit No. 3). A further lift well (Pump Pit No. 4) is located between Bungalows 65 and 66, pumping across to Pump Pit No. 3 Pump Pit No. 3 pumps effluent across the lake via a DN32 HDPE Blue line main into an existing gravity sewer access chamber. 1.3.2 Assessment It has been calculated that the current configuration of the Bungalow estate, when at full occupancy, would be generating a hydraulic flow rate of approximately 48,000 litres per day. In general terms, the existing OSWM system is in a reasonable condition and appears to be maintained by contractors, however this would not resolve the insufficient capacity of the system. This is with the exception of the effluent disposal area (absorption beds) that appear to be showing signs of trench failure. The system would not be deemed fit for purpose. The following general shortcomings are noted: 1) SSP1, SSP3 and SSP5 lift well covers are not watertight, no obvious signs of venting, chamber holding capacity inadequate. Review of Waste Water Treatment Facilities to Lake Bennett Resort 18DA0418 - Bungalow 20191014 - Review of Waste Water Treatment Facilities Rev 2.docx JT 14/10/19 Page 6 of 28 2) Incorrect use of HDPE pipework (identification). AS 1345 requires that the content within the pipe work to be identified by specific colour coding. Lilac is to identify sewer effluent. 3) Disposal area inadequate is size and does not meet the minimum site assessment criteria. 4) Septic tank capacity, undersized. Based on this report and in accordance with the Code of Practice site assessment criteria, the existing effluent disposal area would be considered to be unsuitable and an alternative effluent disposal method must be investigated. 1.4 Recommendations We consider the only immediate options available for the Bungalow Estate to operate would be to install a Commercial Wastewater Treatment System (Modular / Containerised). Body Corporate to engage a consultant to determine a suitable Commercial Wastewater Treatment System so that wastewater can be used for landscaping, irrigation or other approved uses. The system would be capable of producing secondary treated recycled water of a standard up to “A” Class therefore further substantially reducing the Land application area required. This would be prudent as it has been identified by the Geotechnical Report that the soils within the current effluent disposal area have a low LTAR. Review of Waste Water Treatment Facilities to Lake Bennett Resort 18DA0418 - Bungalow 20191014 - Review of Waste Water Treatment Facilities Rev 2.docx JT 14/10/19 Page 7 of 28 2 Background The Bungalow Estate was established in the mid 1990’s We have been unable to locate / find any information / approval associated with the on-site treatment sewage for this development. A search of the Building Advisory Files contained information and approvals only for hydraulic works associated with each individual Bungalow to the extent of the cadastral boundary but did not contain the common sewer drainage system and effluent treatment. In the absence of any design information and approvals the summarized loadings are based on septic tank selection. This has then been reversed engineered based on the configuration for the system inspected. 2.1.1 Septic tank capacities for residential domestic premises Class 1 and Class 10. Based on the Code of Practise a minimum daily allowance (hydraulic loading) of 150 litres per person per day in Urban and Rural Living areas is applicable, with a minimum sludge/scum accumulated rate of 80 litres per person per year. In the NT a nominal capacity of two persons per bedroom is used for the daily flow calculations. Determining the appropriate size of a septic tank requires the determination of two factors, namely: 1) Volume for accumulation of sludge/scum (S x P1 x Y) 2) Volume of daily flow into septic tank (P2 x DF) The effective capacity is obtained by calculating: (S1 x P1 x Y) + (P2 x DF) S = Rate of sludge/scum accumulation per person per year P1 = Number of persons using the system Y = Desludging frequency required and upon which the tank capacity depends = 1 year desludging frequency. P2 = Number of persons using the system DF = Daily inflow in litres per person per day. Based on Body Corporate advice, the average bedroom per Bungalow within the estate is 2.5 bedrooms. Bungalows – (bedrooms) 1 to 16 - (40 bedrooms) 17 – 59 – (105 bedrooms) 65 & 66 – (5 bedrooms) 75, 76, 79 & 80 – (10 bedrooms) Total P1 80 210 10 20 S 80 80 80 80 P2 80 210 10 20 DF 150 150 150 150 SxP1 6,400 16,800 800 1600 P2xDF 12,000 31,500 1,500 3000 SxP1xY+P2xDF 18,400 48,300 2,300 4,600 25,600 48,000 73,600 L The current effluent disposal area associated with this hydraulic loading is 4 trenches 35 metres long. 2.1.2 Current Facilities/Configuration The required septic tank capacity including sludge accumulation would be 73,600 Litres which is nearly four times greater than the available holding capacity of the existing primary septic tank which is deemed to be 18,000L as discussed in following sections. Review of Waste Water Treatment Facilities to Lake Bennett Resort 18DA0418 - Bungalow 20191014 - Review of Waste Water Treatment Facilities Rev 2.docx JT 14/10/19 Page 8 of 28 2.2 2.2.1 Assessment of Disposal Area Absorption Disposal Area In the absence of any design information and approvals it is assumed the original design was based on an LTAR of 15 from the Lake Bennett Resorts original findings undertaken by Aquatreat Pty Ltd (field test). As the two effluent disposal areas are in close proximity and were developed by the same developer. 2.2.2 Existing Disposal Installation Absorption trench length required is calculated by the use of the following formula: Trench length = Absorption area (AA) / effective absorption width (We). In the absence of any design information and approvals we have adopted the trench design / configuration from the Lake Bennett Resorts documented system. As they were developed by the same developer at the same time, this is considered a reasonable assumption. Based on the standard arch tunnel and the detailed trench within the ADG documents, the effective absorption width (We) is 1.4m, the required trench length therefore = Absorption area = 4800 /15 = 3200. Effective absorption width = 1.4 Trench length = 3200 / 1.4 = 2,285.7m Therefore 66 absorption trenches x 35m long would be required based on a daily flow of 48,000 L/day. Currently the existing absorption trench lengths are 35m long x 4 rows = 140 m, substantially less than the required 66 trenches x 35 meters = 2,310 m 2.2.3 Assessment of Current Required Disposal Area Based on the Geotechnical Investigation and testing it has been established that at best the LTAR of 10 would be the upper limit, therefore based on this the calculated Absorption Area (AA) required is Calculated by Hydraulic flow/LTAR being 48000L /10 LTAR = 4,800m2. Utilising the standard arch tunnel (as documented) for the absorption trench the effective absorption width = 1.4m. Trench Lengths = Absorption Area (AA)/Effective Absorption Width (We) being 4,800m2 /1.4m = 3,428 m. Individual trench lengths shall be limited to around 20m. This would satisfy AS/NZS 1547 maximum trench length of 20m. A longer trench is possible of the installer if the installer can guarantee a level bottom over the proposed length. In situations, the designer shall specify the maximum trench length appropriate to the construction method to be used. The disposal area is thus grossly undersized (approximately 25 times the current installation) for the anticipated usage. Due to these elevated flows the water quality reaching the disposal area is likely to be of poor quality, posing a health risk, as it may not had the required settling period within the septic system. Review of Waste Water Treatment Facilities to Lake Bennett Resort 18DA0418 - Bungalow 20191014 - Review of Waste Water Treatment Facilities Rev 2.docx JT 14/10/19 Page 9 of 28 3 Existing Infrastructure A further site inspection was undertaken on the 02 February 2019 & 17 April 2019 by Mitch Roberts (Wigg Plumbing) and Mario Maddalozzo (Irwinconsult). The purpose of the inspections was to investigate the existing OSWM system with regard to capacity and condition. 3.1 Existing Septic Tanks The existing concrete septic tanks are approximately 1 X 18,000 litres, 2 X 6,000 litres 1 X 3,000 (refer Section 1.3.1) Litres in capacity, providing a total holding capacity of 33,000 litres. However the smaller tanks discharge the waste which is partially treated into the primary septic tank closest to the effluent disposal area. 18,000 is considered to be the ‘primary’ tank (SSP1). The tanks and access lids appear to be in reasonable condition with no evidence of sulphate attack on the concrete structure. The primary tank is located adjacent to the causeway and has been known to be submerged during flooding. The primary tank and controller panel is protected by vehicle loads via bollards and chain. The existing 2 X 6,000 litre septic tanks associated with Pump Station 2 are located on the opposite side of the causeway and similarly have been known to be submerged in flooding events. The septic’s are not protected and vehicle loads are considered to be a risk. Similarly with the 3,000 litre septic tank associated with sewer pump station SSP5, the septic may be subjected to flooding in major flooding events. All septic tanks are located within the minimum set back / proximity requirements as set out in the Code of Practice. The minimum required distance from lakes / water course is 50m but primarily as the adjacent Lake Resort primarily obtains its water source from the lake the required minimum distance is 200 meters. Upon inspection of the primary septic tank there was evidence of surcharging (flooding). This may have occurred when the effluent lift well pumps failed. Review of Waste Water Treatment Facilities to Lake Bennett Resort 18DA0418 - Bungalow 20191014 - Review of Waste Water Treatment Facilities Rev 2.docx JT 14/10/19 Page 10 of 28 18,000L Concrete Septic tank and Sewer Pump Station adjacent to Water Course. Inspection Opening to septic – Note surcharging (ragging) on ladder and PVC rising sewer main discharge pipe. Review of Waste Water Treatment Facilities to Lake Bennett Resort 18DA0418 - Bungalow 20191014 - Review of Waste Water Treatment Facilities Rev 2.docx JT 14/10/19 Page 11 of 28 Evidence of ground water entering sewer access chamber. 3000 Litre septic tank and associated sewer pump station SSP5 (behind). Note existing septic to the right hand side appears to have been by-passed and all effluent collected in left tank. Review of Waste Water Treatment Facilities to Lake Bennett Resort 18DA0418 - Bungalow 20191014 - Review of Waste Water Treatment Facilities Rev 2.docx JT 14/10/19 Page 12 of 28 3.2 Existing Lift Wells The site has several effluent lift well and pumps / sewer pump stations. These are located adjacent to the septic tanks and at strategic locations to pump the effluent into the septic tanks. Generally they appear to be in good working condition. We were informed by the Body Corporate that some of the pumps are relatively new as they were replaced prior to the investigation commencing. We did notice on one site visit that HD Pumps service personnel were changing out pumps on SSP2. All but one lift well / pump station are precast concrete. Pump station SSP4 is Polyethylene and is located between Bungalows 65 and 66. The concrete sewer pumps chambers have been assembled using a series of concrete rings but the joints have not been fully sealed. Existing effluent lift well / Pump station SSP1. Review of Waste Water Treatment Facilities to Lake Bennett Resort 18DA0418 - Bungalow 20191014 - Review of Waste Water Treatment Facilities Rev 2.docx JT 14/10/19 Page 13 of 28 Sewer Pump Station SSP1 Existing effluent lift well / Pump station SSP2. Review of Waste Water Treatment Facilities to Lake Bennett Resort 18DA0418 - Bungalow 20191014 - Review of Waste Water Treatment Facilities Rev 2.docx JT 14/10/19 Page 14 of 28 Existing lift well / Sewer Pump station SSP3 – pumps effluent across the lake. Existing lift well / Sewer Pump Station SSP4. Review of Waste Water Treatment Facilities to Lake Bennett Resort 18DA0418 - Bungalow 20191014 - Review of Waste Water Treatment Facilities Rev 2.docx JT 14/10/19 Page 15 of 28 Existing lift well / Sewer Pump Station SSP5. 3.2.1 Compliance of Existing Pump Chambers (SSP1, SSP2, SSP3, SSP4 & SSP5) In accordance with the Code of Practice for Small On-site Sewage and Sullage Treatment Systems Section 7.13.4, the pump chambers generally meets the requirements to satisfy the code except for: • Be provided with a cover that is fitted so as to be water tight and have an access opening and cover of at least 500 x 450mm or DN500 terminating at the surface. • The existing cover would not be deemed water tight. • Fitted with a DN100 induct vent either located in the inlet pipe to the pump chamber or on the pump chamber cover. • No venting visible on chamber. • A minimum holding capacity of “500 litres or 50% of the daily inflow, whichever is the greater shall be provided as an emergency storage provision”. • As the calculated daily inflow for the Bungalows estate is 48,000L the pump chamber would need to be in the order of 24,000L to be compliant. 3.3 Rising Sewer Main The alignment of the existing DN32 HDPE sewer rising main that traverses the lake appears to be within the sewer easement registered on title. The rising sewer main between the pump chamber and lake is un-marked and due to the incorrect pipe identification (Colour) poses a risk that cross contamination could occur between potable, irrigation water and effluent water. In accordance with AS 1345 “Identification of the Contents of pipes, conduits and ducts” the markings on the pipe indicates the content within and the blue line represents potable water, green line represents irrigation water and Lilac represents effluent water. The existing rising main is Blue line (potable water). The effluent sewer rising main should be identified by a Lilac strip, this is conventional pipe work identification. Someone without the existing knowledge could potentially cut in a connection into the effluent rising main assuming it was Review of Waste Water Treatment Facilities to Lake Bennett Resort 18DA0418 - Bungalow 20191014 - Review of Waste Water Treatment Facilities Rev 2.docx JT 14/10/19 Page 16 of 28 irrigation / potable water posing a health risk to visitors to the Estate and contaminating the potable supply to the Resort. It is recommended that alignment of the effluent rising sewer main be re-routed around the perimeter of the lake following the access road. As the primary source of potable drinking water to the adjacent Lake Bennett Resort is from the lake, the submerged rising sewer main poses a High risk to this water source. Un mark alignment of DN32 sewer rising main between SSP3 and lake. DN32 blue line sewer rising main running along surface. Review of Waste Water Treatment Facilities to Lake Bennett Resort 18DA0418 - Bungalow 20191014 - Review of Waste Water Treatment Facilities Rev 2.docx JT 14/10/19 Page 17 of 28 DN32 HDPE Blue Line (effluent rising sewer main) running adjacent to Bungalow and above ground crossing irrigation mains. DN32 HDPE (Blue Line) effluent sewer rising main discharging into sewer access chamber. 3.4 Effluent Disposal Area In assessing a suitable effluent disposal area in accordance with the Code of Practice the following criteria must be considered: 1) The disposal site shall not: a. Be within a water course. b. Be within a flood plain as indicated by contours of the terrain or type of vegetation. Review of Waste Water Treatment Facilities to Lake Bennett Resort 18DA0418 - Bungalow 20191014 - Review of Waste Water Treatment Facilities Rev 2.docx JT 14/10/19 Page 18 of 28 c. Must have a consistent soil horizon to a depth of 1.2 metres. Comment: The existing effluent disposal area is located approximately 150m East of the septic tanks and North East of the lake. The effluent beds are separated from the lake by a ridge which runs North South parallel to the lake. The effluent disposal area is above a flood plain and away from a known water course, so the existing location is deemed to meet the requirements set out in the site assessment criteria Item 1 above. 2) The nearest point of discharge from the septic tank’s effluent disposal system shall be no less than 100 metres from a bore or well. Comment: The effluent disposal area is approximately 150m from the bore. 3) For effective operation, the soil Long Term Acceptance Rate (LTAR) should be between 10 – 25 litres/m2/day. An LTAR outside the 10-25 litres/m2/day range shall necessitate further site investigation and certification by plumber designer that effluent disposal by ground absorption under these circumstances, will operate effectively. Comment: The disposal area/plateau has been created by a method of cut and fill and is well drained. The cut side of the effluent disposal area has no cut off drains to capture storm water runoff prior to it reaching the effluent beds. Due to the cut and fill method used to create the effluent disposal area, the consistent requirements for the soil horizon has been affected and the rock layer is now within 0.4m of the surface for a portion of the effluent disposal area. This has been identified in the Geotechnical investigation undertaken by Douglas and Partners attached in Appendix B within this report. For the effective operation, the soil’s LTAR requires to be within 10 – 25L/m2/day. In the absence of any design information and approvals we are unable to determine the original design parameters. The Geotechnical investigation recently undertaken by Douglas and Partners classified the LTAR of the soil between a range of 8 -10L/m2/day with 10L/m2/day being the upper limit for this soil type. The 8L/m2/day falls outside the NT Code of Practice minimum LTAR standards. Based on this report and in accordance with the Code of Practice for site assessment criteria, the existing effluent disposal area would be considered to be unsuitable and an alternative effluent disposal method would need to be investigated as part of a remedial works. 4) Ground slope must not exceed 1 in 4 (25%). Comment: The effluent disposal area is relatively flat and meets the assessment criteria for an effluent disposal area. 5) Unfragmented or impervious rock shall be not closer than 1.0 meter to the ground surface. Comment: Review of Waste Water Treatment Facilities to Lake Bennett Resort 18DA0418 - Bungalow 20191014 - Review of Waste Water Treatment Facilities Rev 2.docx JT 14/10/19 Page 19 of 28 Impervious rock was found within 1.0m of the surface, so the assessment criteria for the effluent disposal area does not meet the NT Code of Practice. 6) Ground water during all seasonal conditions shall be not less than 1.0 metre to the ground surface. Comment: No ground water was detected during the investigation of the effluent disposal area, satisfying the assessment criteria for an effluent disposal area at the time of investigation. 7) The septic tank’s effluent disposal system shall satisfy the proximity to site features criteria of Section 7.5 of the Code of Practice. Comment: The effluent disposal area would be deemed to satisfy the criteria as set out in Section 7.5 of the Code of Practise. 8) No structure shall be built over the proposed septic tank site. Comment: Compliant with site assessment criteria. Summary In summary, the existing effluent disposal system does not satisfy the minimum standards in order for the disposal by ground absorption within an individual allotment. Review of Waste Water Treatment Facilities to Lake Bennett Resort 18DA0418 - Bungalow 20191014 - Review of Waste Water Treatment Facilities Rev 2.docx JT 14/10/19 Page 20 of 28 Existing effluent disposal area. Inspection opens at the commencement of effluent trenches surrounded by 200 L drums. Review of Waste Water Treatment Facilities to Lake Bennett Resort 18DA0418 - Bungalow 20191014 - Review of Waste Water Treatment Facilities Rev 2.docx JT 14/10/19 Page 21 of 28 Existing effluent trenches cut into existing ridge. Effluent disposal area located East of the septic tanks. Effluent disposal area is well above flood prone areas. Disposal area over grown with weeds. Review of Waste Water Treatment Facilities to Lake Bennett Resort 18DA0418 - Bungalow 20191014 - Review of Waste Water Treatment Facilities Rev 2.docx JT 14/10/19 Page 22 of 28 Effluent disposal area constructed within a rocky ridge. Effluent visible at surface at end of effluent trenches. When the inspection openings at the head off the absorption trenches were opened, we observed that the drains were ¾ full of effluent. This was not surprising as the effluent was evident at the surface. This would suggest that the absorption trenches are not operating efficiently or that the volume of effluent is far greater than the system can absorb. 3.5 Distribution Chamber The effluent is pumped from the lift well at the end of the septic tank system to a receiving concrete distribution chamber located at the head of the effluent drains. The distribution chamber is showing signs of sulphate attack and would be nearing the end of its design life. Review of Waste Water Treatment Facilities to Lake Bennett Resort 18DA0418 - Bungalow 20191014 - Review of Waste Water Treatment Facilities Rev 2.docx JT 14/10/19 Page 23 of 28 The effluent from this receiving distribution chamber is then distributed to the 4 effluent drains via gravity. Receiving Distribution chamber. Exposed pipe work leading into the receiving chamber will be prone to bush fire damage and vehicle loads. It is recommended that the pipe work is buried/covered with soil to prevent damage. Review of Waste Water Treatment Facilities to Lake Bennett Resort 18DA0418 - Bungalow 20191014 - Review of Waste Water Treatment Facilities Rev 2.docx JT 14/10/19 Page 24 of 28 Rising sewer main exposed to surface and within access road to absorption area. Review of Waste Water Treatment Facilities to Lake Bennett Resort 18DA0418 - Bungalow 20191014 - Review of Waste Water Treatment Facilities Rev 2.docx JT 14/10/19 Page 25 of 28 4 Review of Waste Water Treatment Facilities Refer to Appendix A – Wigg Plumbing Report Review of Waste Water Treatment Facilities to Lake Bennett Resort 18DA0418 - Bungalow 20191014 - Review of Waste Water Treatment Facilities Rev 2.docx JT 14/10/19 Page 26 of 28 5 Findings Based on investigative inspections of the existing OSWM system, it is the opinion of this report that the current OSWM system is substantially undersized for the Bungalows when occupied at an average rate of 2.5 rooms/Bungalow. The effluent disposal system does not meet the minimum site assessment criteria. It is also the opinion that the absorption trenches are not operating efficiently as the trenches were found to be overflowing as they are grossly undersized. In general terms, the existing OSWM system is in a reasonable condition, however this would not resolve the inadequate capacity of the system. The following shortcomings are noted: 1) Lift well cover not watertight, no obvious signs of venting, chamber holding capacity inadequate. 2) Incorrect use of HDPE pipework (identification). AS 1345 requires that the content within the pipe work to be identified by specific colour coding. Lilac is to identify sewer effluent. 3) Disposal area inadequate is size and does not meet the minimum site assessment criteria. 4) Septic tank capacity, undersized. Based on this report and in accordance with the Code of Practice site assessment criteria, the existing effluent disposal area would be considered to be unsuitable and an alternative effluent disposal method would need to be investigated. Review of Waste Water Treatment Facilities to Lake Bennett Resort 18DA0418 - Bungalow 20191014 - Review of Waste Water Treatment Facilities Rev 2.docx JT 14/10/19 Page 27 of 28 6 Recommendations Commercial Wastewater Treatment System (Modular / Containerised) Design and install a Commercial Wastewater Treatment System so that wastewater can be used for landscaping, irrigation or other approved uses. The system should be capable of producing secondary treated recycled water of a standard up to “A” Class therefore further substantially reducing the Land application area required. This would be prudent as it has been identified by the Geotechnical Report that the soils within the current effluent disposal area have a low LTAR. Review of Waste Water Treatment Facilities to Lake Bennett Resort 18DA0418 - Bungalow 20191014 - Review of Waste Water Treatment Facilities Rev 2.docx JT 14/10/19 Page 28 of 28 APPENDIX A WIGG PLUMBING REPORT Review of Waste Water Treatment Facilities to Lake Bennett Resort April 2018 Lake Bennett Bungalows Chinner Road, Batchelor NT Review of Waste Water Treatment Facilities Report Prepared by: Mitch Roberts PH: (08) 8947 0321 Email: admin@wiggplumbing.com.au Web: www.wiggplumbing.vom.au Lake Bennett Bungalows Review of Waste Water Treatment Facilities As requested by Irwinconsult, Wigg Plumbing have carried out an assessment of the On-Site Wastewater Management (OSWM) system at Lake Bennett Bungalows at the request of the NT Department of Health. The assessment has been carried out to determine the condition, performance and compliance with the NT Code of Practise for the On-site Wasterwater Management (Code). An initial site assessment was carried out by Irwinconsult's Neil Clarke & Mitch Roberts from Wigg Plumbing to identify the features and basic layout of the OSWM. Further detailed inspection on the OSWM were also carried out on the 05/02 & 17/04/2019 accompanied by Mario Madalozzo. Site Details All waste water generated on site is treated through the main concrete septic tank on the North East corner of the lake. From the septic tank the water is pump from from the lift well (SSP1) to the land application area (disposal area) approximately 150mm away in an easterly direction. Effluent from the bungalows on the eastern side of the lake (17-58) is received via a gravity main discharging directly into the main septic tank as raw effluent. The gravity main appears to be a 150mm PVC line with 2 sewer access chambers located along the line, where the main changes direction. Each bungalow then appears to connect individually through a 100mm property service to the 150mm main. The upstream access chamber, located approximately halfway along the gravity main receives the primary treated effluent from a lift well (SSP3) on the western side of the lake through a 32mm blueline polyethylene pipe. SSP3 receives the primary treated water from septic tanks located at units 65-66, 75-76 & 79-80 via a 32mm blueline polyethylene pipeline. Units 65-66 raw sewerage is treated by a Everhard 3000ltr septic tank located between the two units. Outflow from the septic tank is then collected and discharged from a lift well (SSP4) to the common 32mm blueline polyethylene discharging at SSP3. Two Aqua Treat Waste Water Treatment System (WWTS) have been installed between bungalows 75-76. Effluents from bungalows 75-76 & 79-80 discharge into the WWTS located nearest to unit 76 with no inflows received into the second WWTS. Primary treated effluent is then pumped from the final effluent chamber of the WWTS down to SSP3, connecting with the discharge from SSP4. Effluent generated by Bungalows 1-16 on the Northern end of the lake is collected by a gravity sewer main. The raw sewerage is then evenly distributed through two concrete septic tanks located on the eastern end of bungalow 16 via a concrete distribution chamber. Outflow from the septic tank is then collected by the concrete lift well (SSP2) and pump across the causeway to the main septic tank where it discharges through a 50mm PVC pipe through the side wall of the riser chamber. Water for the site is source from a bore located adjacent north east end of Eastlake Drive. The bore water is then pumped to the top of the ridge line running north south parallel to the lake where it is stored in in multiple storage tanks. Water is then supplied to the bungalows under head pressure through a common polyethylene water main. Chocolate Gold Pty Ltd T/A's Wigg Plumbing ABN: 57618240190 PH: (08) 8947 0321 Email: admin@wiggplumbing.com.au Web: www.wiggplumbing.vom.au Main Concrete Septic & Lift Well (SSP1) Septic Tank: The main concrete septic tank appear to be constructed from two 3 meter lengths of steel reinforced concrete pipes. The pipes appear to have a diameter of 2.4 meters, with a total length of 6 meters. Concrete riser have been installed to provide the access to the septic tank with ladder access provided for the 4.1meter depth to the top of the tank. The maximum depth of soil cover of 1.0 metre over the septic tank permitted by the code has been well exceeded by the 4.1 meter depth the septic tank has been installed at. Sealing of the chamber risers with a two part epoxy between the joins of the risers appears to have been carried out with evidence of excess epoxy hanging from the joins, however there was no evidence of the join having been completely sealed internally to ensure the integrity of the joint seal. Surcharging of the system had occurred due to the debris left on the top rung of the ladder. At the time of the initial site familiarisation the chairperson of the body corporation had advised that the pumps in SSP1 had failed and had been replaced by HD Pump who service and maintain the pumps & controllers throughout the development. The pumped discharge from SSP2 enters through the top section of the access chamber of the mains septic in 50mm PVC pipe work. The discharge pipe is then directed at 90 degrees towards the top of the tank. The pump discharge then flows into the septic tank through the top crust of the system, rather than at a minimum level of 155mm below the invert level of the outlet fitting as required by the code. Lift Well SSP1: Lift well SSP1 located adjacent to the main septic collects all discharge from the development and transfers it via a duty & stand by pump set to the land application area. The pumps are controlled through a Matelec FPC-Series controller with visual & audible alarms. The controller operates through a 4-float system, with low level float (pump off), pump start (duty float), stand-by pump start (mid-level) and high water alarm. On the site visit on the 17/04/2019 an intermittent alarm fault was occurring on the controller panel indicating a high water alarm. The pump well appeared to be at normal operational level and functioning normally. Evidence of cracking of the coating of the cabling of the alarm floats was sighted at the time which could allow moisture to short circuit the float operation. HD Pump employees who were on site carrying out works on were notified and aware of the issue at the time inspection. On later visit to sites the alarm fault appeared to have been rectified. The main electrical sub board for the electrical supply to the pumps has also been fitted with a visual alarm strobe. The strobe is installed in the normally activated position to to confirm that power is supplied to the pump station and that no power outages have occurred. The concrete lift well also appears to be constructed from from 2.4mtr diameter pipes. however due to the depth of the lift well, a full visual inspection could not be carried out without the use of confined space equipment. The risers used to extend the pit to surface level appeared in good condition with no evidence of sulphur attack or water ingress through the joins. The original discharge pipe work appears to have been altered with a redundant 50mm pipe penetration sighted below the existing discharge pipe work. The penetration through the side wall of the lift well for current discharge pipe work has not been sealed to prevent storm Chocolate Gold Pty Ltd T/A's Wigg Plumbing ABN: 57618240190 PH: (08) 8947 0321 Email: admin@wiggplumbing.com.au Web: www.wiggplumbing.vom.au water run off from entering the lift well which would allow added flow to the land application area. It is recommended that the pipe work be sealed with a two-part epoxy resin or similar to prevent the entry of the storm water. Septic Tank, Distribution Box & Lift Well SSP2 Distribution Box: A concrete distribution box collectors all raw sewerage inflow and directs flow evenly to the two concrete septic tanks. Concrete risers have been installed to raise the access chamber to ground level, with cast iron Gatic type access covers providing access at ground level. The invert of the inlet pipe to the natural ground level is approximately 2.4 meters. At the time of inspection approximately 30mm of top soil was required to reveal the location of the chamber, as the natural ground level appears to have been raised by the surrounding trees and gardens. Septic Tanks: The two concrete septic tanks located at the eastern end of the bungalow 16. Each concrete septic tank appear to be constructed from a horizontal steel reinforced concrete pipes, 2.4 meters in length. The water level in the tanks was measured at 1.8meters giving an effective capacity of each tank of approximately 6,000ltrs. Riser have also been provided to the top of the septic tanks to provide access for maintenance and pumping of the system. The risers are approximately 1.2mtr in diameter and finished at ground with Gatic style lids. Two lengths of concrete risers were installed to raise the chamber the required 2.6 meters to the finished ground level. Evidence of water ingress and tree root infiltration was sighted on both systems. The water ingress was occurring where the risers had been sealed to the main chamber of the septic tank. The low flow of the water and iron staining sighted appeared to be seepage through the join rather than complete failure of the join. The majority of the tree root infiltration appeared to be at the join of the lid an the chamber risers. Some minimal intrusion was also sighted between the join of the septic tank and chamber risers. Lift Well SSP2 SSP2 appears to consist of a concrete pump well with additional risers installed to the lid of the chamber to provide access to the pit. The square access lid of the pit, appears of similar construction to the Darwin Pre-cast vertical septic tanks used in the rural areas around the time development was carried out. Gatic style access chambers have been provided above ground level to provide access to the pump well. On the initial site inspection, the dual pumps installed were controlled by a basic pump controller. The controller had no automation and relied on the water level activating the floats of the individual pumps. The controller also had provision for a high water alarm. Due to the simplistic operation of the controller, pump failure would not be identified until inspection of the system was carried out or the second pump had failed. On a return inspection, the original pump controller was in the process of being replaced with a Matelec FPC-Series controller with visual & audible alarms. The controller also provide duty and standby control of the pumps and individual pump fault alarming. Penetrations through the side wall of the risers for the electrical and float leads were also not sealed which would allow sewer gases to escape from the system. The pump pit has also had the required 100mm vent installed as per code requirements. Chocolate Gold Pty Ltd T/A's Wigg Plumbing ABN: 57618240190 PH: (08) 8947 0321 Email: admin@wiggplumbing.com.au Web: www.wiggplumbing.vom.au Lift Well SSP3 SSP3 appears to be a concrete baffle-less septic tank of similar dimension and construction to the Darwin Pre-Cast vertical septic tank. The dimensions of the tank were taken at 1.8mtr x 2.2mtrs deep with a total capacity of the tank is approximately 5,600 litres. The tank appears in good condition for the age of the development with no defects sighted. The pump pit has been fitted with two pumps operated from a Matelec FPC-Series controller with visual & audible alarms. The main electrical sub board for the electrical supply to the pumps has also been fitted with visual alarm strobe which has been installed in the normally activated position to identify if a power outage to the system has occurred. The pumps in lift well SSP3 have been suspended approximately 0.5 meters from the bottom of the tank reducing the effective capacity of the tank by 1,200ltrs. Discharge from the pumps is via individual bar-flex reinforced hose connected to the 50mm stainless steel manifold. The manifold then connects to the 32mm blue-line poly on the external side of the pit where it is pumped under the lake to the gravity sewer main on the eastern side of the lake. A pressure test of the 32mm blueline poly between SSP3 and the gravity sewer line was conducted to ensure that the pipe was holding pressure and that no failures of the line had occurred. The line was disconnected and capped at the connection point to the stainless steel manifold at SSP3 and then pressurised from the inlet pipe at the inspection chamber on the eastern side of the lake. The line was pressure tested to 200kPa and held for a period of 30 minutes with no pressure loss recorded during that time. On the initial site, water level in the SSP3 were above there normal operational levels. After some investigations it was found that one of the barflex hose had worked loose from the hose tail fitting where connecting to the manifold. The reinforced hose was refitted and secured back in place with the original the hose clamp with the body corporate notified of the issue. Flows rates from the submersible pumps after reconnection of the discharge pipe work were noticeable low. The water level in the pit took a considerable amount of time to pump down from the high water level to the normal working levels. Flow sighted at the discharge point to the access chamber on the gravity main were consistent, but not of a volume as would normally be expected for pumps installed. Flow rate from the pumps would have been greatly reduced due to the length and size of the discharge pipe work. Inflows to SSP3 through the 32mm blue-line polyethylene feed were also low with the flow volume fluctuating. Chocolate Gold Pty Ltd T/A's Wigg Plumbing ABN: 57618240190 PH: (08) 8947 0321 Email: admin@wiggplumbing.com.au Web: www.wiggplumbing.vom.au SSP4 & Everhard Polypropylene Septic Tank An Everhard 3,000 litre plastic septic tank has been installed to received the raw sewerage from Bungalows 65-66. From the septic tank effluent flows through to PPS4. The Everhard septic tank appears of sound structure with no defects sighted. An XtraTreat septic tank outlet filter has been installed to the outlet of the septic tank to help reduce the level of solids leaving the septic tank. At the time of inspection the ExtraTreat outlet valve was due for cleaning due to the the sludge and scum deposits on the filter. PPS4 is constructed from a polymer tank of approximately 500 litres. The original screw lid appears to have been removed and a compost bin installed to raise the lid above the surrounding ground level. The join between the pit and riser appears to have been screwed together with no evidence of sealant in the area. The pit is fitted with a single pump connected directly to a 240 volt power supply with the float activating off the pump when the set level in the tank has been reached. A pump fault inn the pit was found on one of the site visits, with the water level in the pit well above the outlet height of the septic tank. The high water alarm fitted to the pit was not activated and appeared to be faulty with the system in high water. On a return visit the pump appeared to have been replaced and water level in the system was back to normal operating levels. The high water alarm was operated manually however the strobe light was not activated and required further repairs/maintenance. The required vent on the pump out pit as required by the code was not installed. A low level 100mm vent was located approximately 30 meters away adjacent to the driveway of unit 66. Confirmation of the connection of the vent and associated pipe work pipe work could not be confirmed without alterations to the pipe work to allow for a CCTV inspection of the drain. SSP5 Two AquaTreat WWTS were originally installed to treat the raw effluent from units 75-76 & 79-80. The electrical component of the system have since been removed with the systems operating primarily as septic tanks with the secondary tanks acting as additional settling chambers before the final pump out chamber. The AquaTreat systems consist of a primary concrete septic tank which collects all the waste water. The primary tanks have a capacity of 3,000, 4,000 & 5,000ltrs depended on the invert level of the sewer line. From the septic tank the water flows through to a secondary tank that contains additional settling, aeration and disinfection to provide secondary treated effluent. Inspection of the primary tanks of both system was carried out and it was found that there was no evidence of a scum layer in the system on the northern side. A CCTV inspection of the drainage system from the tank on the southern side was then carried out to identify where the inflows to the tank were generated. The drainage line was found to head in a Westerly direction away from the lake, with a junction facing south within the first meter of the line. The line then change direct at a 90 degree angle and headed north towards units 75-76 for approximately 8 meters before the inspection having to be abandoned as the push camera would not pass through what appeared to be an offset in the pipe work. During the CCTV inspection, water was run through the overflow relief gully of Bungalow 76 with the inflow sighted entering the common drain from the junction at the entry to the septic tank on the southern side. CCTV inspection through the inlet pipe of the septic tank on the northern side was not possible due to the tree root infiltration of the system. From the CCTV inspection & lack of scum layer to the tank on the northern side, it was confirmed that the system on the southern side was treating all the water generated from Bungalow 75-76 & 79-80. Chocolate Gold Pty Ltd T/A's Wigg Plumbing ABN: 57618240190 PH: (08) 8947 0321 Email: admin@wiggplumbing.com.au Web: www.wiggplumbing.vom.au When inspected the system on the northern side was found to have tree root infiltration, with the root infiltration appearing to be occurring around the inlet pipe of the primary septic tank. Possible storm water infiltration is also occurring in the taken as at the initial site visit the water level in the system was well below the normal operating system. On subsequent visits which occurred later in the wet season the water level in the tanks was found to be back at normal working level. The Body Corporation had advised that the tanks through out the development had been pumped out by McMInns Pumping and the tanks may have been manually filled. Sewer Access Chambers Two sewer access chambers were sighted along the gravity sewer along the main line of the system on the eastern side of the lake. The access chamber nearest to the septic tank located on the northern side of Bungalow 17 was found to have ground water ingress through the join between the base of the access chamber and the first section of the concrete riser. The consistent flow of the ingress would have been putting a substantial amount of load into the system. Evidence of sealant between the joins in the sections of risers was sighted in both access chambers and around the lids of the chambers. Large gaps between the lid and riser pipe were also noted on both chambers which would not pass a pressure test of the chambers, had one been carried out at the time of construction. Land Application Area The land application area (disposal area) is located on the northern end of the ridge line running parallel to the lake. The disposal area consists of a concrete distribution box which receives the pumped discharge from SSP1. From the distribution box the water is evenly distributed to the 4 disposal beds, with each bed approximately 35mtrs in length. The pumped discharge from SSP1 runs through a 50mm UPVC pressure pipe from PPS1, crossing Lakeview drive at approximately 90 degrees and then following the access track to the distribution box. In several sections the pipe has been exposed at ground level along the track and does not have the minimum 450mm depth recommended by AS 3500 plumbing code requirements. Due to the location of the pipe work at surface level along the main access to the disposal area the likely hood of potential damage to the line is high. The concrete distribution box has evidence of sulphur attack which has left the aggregate in the concrete exposed. Due to the condition of the concrete it would be recommended that the distribution box be replaced prior to leakage occurring. The disposal bed appear to be constructed from Reln style plastic tunnel or similar. Separation of the inspection openings at the start of the trenches indicate that the maximum trench width of 1.5mtrs is achieved if installed to meet code requirements, with an approximately length of 35 meters. Steel drums have been used as protection collars around the 100mm PVC inspection risers at the entry point of the disposal area. Evidence of damage tot he risers has occurred and where repairs carried out several of the risers have not been sealed to the trenches. Where this has occurred loose soil was sighted between the pipe and top of the plastic tunnel. Chocolate Gold Pty Ltd T/A's Wigg Plumbing ABN: 57618240190 PH: (08) 8947 0321 Email: admin@wiggplumbing.com.au Web: www.wiggplumbing.vom.au On the initial site visit there was evidence of water in the bottom of the trenches which was consistent with the discharge sighted when the pump had recently operated. On the following site visits effluent was clearly visible flowing from the end of the trenches indicating complete saturation of the trenches, with the discharge appearing to have occurred for some time due to the algae and slime that was present. Water Reservoir The water supply to the development is supplied from the bore at the north eastern end of the lake. The bore supply is then pumped from a secondary pump set to the water storage tanks located at the top of the ridge line on the eastern side of the lake. The storage tanks consist of 4 x 25,000ltr Terra Corp polyethylene tanks, 2 x 10,000ltr Terra Corp polyethylene tanks & 1 135,000ltr steel tank with internal liner. Due to height difference of the overflows points on the individual tank the estimated total capacity of all the tanks is approximately 220,000ltrs. As the water supply is not rely on power, water usage through out the development is possible during a power outage. As the waste water system relies on power for the effluent pumps to operate, there is a potential that the full 220,000 litres of stored water could be placed into the waste water treatment system during extended power outages. If the stored supply was diminished during an out, when the power was reinstated pumps would automatically operate pumping the system down to its normal operating levels which would cause inundation of the disposal area. Chocolate Gold Pty Ltd T/A's Wigg Plumbing ABN: 57618240190 APPENDIX B DOUGLAS & PARTNERS GEOTECHNICAL REPORT Review of Waste Water Treatment Facilities to Lake Bennett Resort APPENDIX C SCHEMATIC DRAWING OF OSWM LAYOUT Review of Waste Water Treatment Facilities to Lake Bennett Resort RO AD AC CE SS RO A D SEWER PUMP STATION 2 (SSP2) WITH ASSOCIATED 2 x 3000 LITRE SEPTIC TANK R CHINNER ROAD SEWER PUMP STATION 1 (SSP1) WITH ASSOCIATED 18,000 LITRE SEPTIC TANK CH IN NE SSP2 SSP1 DN32 SEWER RISING MAIN EFFLUENT DISPOSAL AREA FOR BUNGALOWS 4 x 35m LONG EFFLUENT TRENCHES DN32 SEWER RISING MAIN ACROSS LAKE APPROXIMATE ALIGNMENT OF DN150 GRAVITY SEWER MAIN SEWER PUMP STATION 3 SSP3 SEWER PUMP STATION 4 EFFLUENT DISPOSAL AREA FOR THE LAKE BENNETT RESORT CHIN SEWER PUMP STATION 5 AND ASSOCIATED SEPTIC TANK RO NER DN32 SEWER RISING MAIN BETWEEN SSP5 AND SSP4 AD ROA D SSP4 SSP5 N LA LAKE BENNETT O GO RS E TH A HE SCHEMATIC LAYOUT OF EFFLUENT DISPOSAL SYSTEM SITE PLAN CAD FILE: SK002.DWG DISCLAIMER: Copyright of this drawing is vested in Irwinconsult Pty Ltd and this drawing/file is not to be reproduced or copied in whole or in part, in any form, without the prior written approval of Irwinconsult Pty Ltd. The recipient is responsible for ensuring that they review the status of this drawing, and are in receipt of the current revision prior to use. except where figured dimensions have been provided, Irwinconsult is not responsible for dimensioning and setting out. this drawing has not been produced to a level of dimensional accuracy suitable for fabrication. the contractor is responsible for production of fabrication / shop drawings where these are required. this drawing has been produced for the named client for use on this project only and is not to be used for any other purpose. CLIENT: PROJECT NAME: TITLE: DEPARTMENT OF HEALTH LAKE BENNETT BUNGALOWS LAKE BENNETT SCHEMATIC LAYOUT OF EFFLUENT DISPOSAL SYSTEM - SITE PLAN SCHEMATIC DESIGN NOT TO BE USED FOR CONSTRUCTION P1 REPORT ISSUE REV DESCRIPTION TGN 04/07/2019 BY DATE SCALE AT A1 REV DESCRIPTION BY DATE SCALE INDICATED FOR REFERENCE ONLY. DO NOT SCALE DRAWING. N.T.S DATE: 5/06/2019 DRAWN: DESIGNER: CHECKED: APPROVED: TGN MM MM MM PROJECT NUMBER: DRAWING No: REVISION: 18DA0418 SK 001 P1 SHEET SIZE: A1 DATE PLOTTED: 4/07/2019 9:03:35 AM BY : TESSA NOSSAN