lockhart shire council sewerage reticulation feasibility ... · sustainability (deus)) ‘the rock...

Lockhart Shire Council

Sewerage Reticulation

Feasibility report DEUS –

ESLER Report Comparison

The rock NSW

January 2015

Esler and Associates Sewer Reticulation Feasibility Scope Expansion Report: Draft For Comment

Index:

1. Executive Summary: 1 2. Report Summary: 1 3. Differences in Scope of Reports: 1

3.1. Feasibility Land Areas: 1 3.2. Existing Sewage Treatment Facilities: 1 3.3. Existing Sewer System: 1

4. Estimated Tenement Projections: 1

4.1. DEUS Projection: 1 4.2. Esler and Associates Projection: 2 4.3. Growth Within the Township West of the Highway: 2 4.4. Future Development Lot Sizes: 2 4.5. Projected Tenement Table 2

5. Sewer Layout 2

5.1. Sewer Catchment Areas: 2 5.2. Gravity Sewer Proposed Layout: 2 5.3. Pump Station Locations: 2 5.4. Sewer Rising Main 2

6. Projected Hydraulic Loadings: 2

6.1. DEUS Loading Estimate: 2 6.2. DEUS Existing Gravity Main Capacity 2 6.3. Esler and Associates Existing Capacity 3 6.4. Pump Station Control 3 6.5. Storm Allowance 3

7. Storm Alowance: 3

7.1. DEUS Assumptions: 3 7.2. Alternative Storm Allowance: 3 7.3. Sewer Main Pip Capacity: 4 7.4. Alternative Ultimate Flows in Sewer Line A: 4 7.5. Example of Actual Measured Storm Flows 4 7.6. Verification of Storm Flow 4

8. Unit Cost Comparison: 5

8.1. Construction Unit Costs: 5 8.2. Table of Comparison of Construction Unit Costs: 5 8.3. Professional Fee Unit Rates: 5 8.4. Table of Comparison of Professional Fees: 5

9. Overall Construction Costs for the

Sewer System DEUS: 6 9.1. Construction Costs Pump Stsations: 6 9.2. Construction Costs Sewer Reticulation: 6 9.3. Possible Over Estimation by DEUS: 6

10. Overall Construction Costs for the

Sewer System Esler and Associates: 6 10.1. Construction Costs Pump Stations: 6 10.2. Construction Costs Sewer Reticulation: 6

Esler and Associates Sewer Reticulation Feasibility Scope Expansion Report: Draft For Comment

11. Overall Construction Cost Comparison: 6 11.1. Cost Comparison: 6 11.2. DEUS Cost Options: 7 11.3. Overall Cost Comparison Table: 7

12. Conclusion 8

Esler and Associates Sewer Reticulation Feasibility Report The Rock : Draft For Comment

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1. Executive Summary:

Lockhart Shire Council has commissioned 2 reports that discuss the feasibility and costs to construct a sewerage reticulation scheme to service The Rock township east of the Olympic Highway, firstly being NSW Department of Commerce (Department of Energy Utilities and Sustainability (DEUS)) ‘The Rock Sewerage Scheme’ March 2007 report and Secondly Esler and Associates ‘The Lockhart Shire Council Sewerage Reticulation Feasibility Report South Side of the Olympic Hwy The Rock NSW’ Both reports conclude it is feasible to service the study area and the ultimate number of lots and costs for the sewerage system are:

DEUS Report Esler Report

Ultimate Number of Lots 977 532 Overall Construction Cost $7,761,000 $5,080,000

Cost Per Lot $7,945.00 $9,550.00

2. Report Summary:

This report supplements the Esler and Associates ‘The Lockhart Shire Council Sewerage Reticulation Feasibility Report South Side of the Olympic Hwy The Rock NSW’ as presented to the Lockhart Shire Council May 2014.

The purpose of this report is to compare and discuss the above mentioned report and NSW Department of Commerce (Department of Energy Utilities and Sustainability (DEUS)) ‘The Rock Sewerage Scheme’ March 2007 report. Including: Differences in scope Design assumptions and specifications Supply and construction unit rates. Proposed gravity system and pump station layouts

3. Differences in Scope of Reports:

3.1. Feasibility Land Areas: Both reports investigate the feasibility of extending the existing

sewer system to include existing and potential new developments to the East of the Olympic Highway at The Rock Township. Esler and Associates study extends further than the DEUS, namely catchment areas identified as 5, 9 and 13 in the Esler’s report.

3.2. Existing Sewage Treatment Facilities: The DEUS report included data and comments on the existing Sewage Treatment Plant (STP) located to the west of the Township, while the STP was not included the scope of the Esler Report. For comparison purposes the STP and any cost associated with maintenance and/or upgrades will not be included in this report.

3.3. Existing Sewer System: Both reports discuss the capacity of the existing sewer system within the township to the west of the highway, While the method to determine the existing number of tenements and existing capacity of the system is different for each report the conclusions are similar. This is further discussed below.

4. Estimated Tenement Projections: 4.1. DEUS Projection: The number of existing tenements and future loadings has been

calculated using Census (2006) data from the Australian Bureau of Statistics. The estimated tenements and loadings over time have been estimated by assuming a 3.5% annual population growth for The Rock.


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4.2. Esler and Associates Projection: The number of existing tenements has been determined by a simple lot count within the current sewer system west of the Highway. Future loading has been calculated by identifying future developments (subdivisions) within the study area east of the highway and applying an appropriate lot density.

4.3. Growth Within the Township West of the Highway: DEUS has assumed future population growth within the township west of the highway will be similar to the growth east of the highway by the means of infill developments. Esler and Associates have assumed infill development west of the highway will be negligible because the existing lots are well established.

4.4. Future Development Lot Sizes: DEUS has assumed future development to the east of the highway will ultimately be standard ¼ acre lots (1000m2). Esler and Associates have assumed lots will average 2500m2 and be marketed as lifestyle lots. Therefore Esler and Associates have assumed the ultimate number of lots on the east side of the Highway will be approximately 75% of that assumed by the DEUS.

4.5. Projected Tenement Table: Estimated Number of Lots

NSW Department (2006)

Esler and Associates All Catchments

Esler and Associates Without Catchments

5,9 and 13 Existing West Hwy 297 373 373 Ultimate West Hwy 502 373 373 Existing East Hwy N/A 175 142 Ultimate East Hwy 997 703 532

Ultimate Lots

Combined 1499 1076 905

5. Sewer Layout

5.1. Sewer Catchment Areas: DEUS has divided the land east of the highway into 3 catchments

areas (catchments 4, 5 and 6 –see Appendix 1). Esler and Associates divided the land into 13 catchments (see Appendix 2). The combined catchment of the DEUS report closely matches the combined Esler catchment without Esler catchments 5, 9 and 13.

5.2. Gravity Sewer Proposed Layout: Both reports propose a similar layout for the gravity sewer mains on the east side of the highway, with the alignment of the sewer main a combination of rear of lots, front of lots and road verges. The general flow of material is south to north within the overall catchment area.

5.3. Pump Station Locations: Both reports propose 3 new sewer pump stations on the east side of the highway, although the proposed locations vary, the ultimate locations may again change with full design. Esler and Associates have proposed the first pump station (Pump Station 1) be located within the proposed new subdivision to be constructed by the Lockhart Shire Council; the DEUS has proposed the first new pump station (PS No.4) to be further east along Mangoplah Rd.

5.4. Sewer Rising Main: Both reports have proposed similar routes and discharge points for the sewer rising mains, ultimately all three pump stations will discharge into the existing 300mm dia sewer main in Crownwall Street between manholes A3 and A8. Both reports have an option to discharge directly to STP.

6. Projected Hydraulic Loadings: 6.1. DEUS Loading Estimate: Peak Wet Weather Flows (PWWF) for ultimate population has

been calculated by the use of a spread sheet and using the following parameters: Average Dry Weather Flow (ADWF) has been derived as 0.0071 L/s/ET from assessment of actual Lockhart Council flow data measured at the STP. The storm allowance has been assumed to be 0.058 L/ET.s (NSW Public Works Department Manual of Practice – Sewer Design Section 4).

6.2. DEUS Existing Gravity Main Capacity: The capacity of the existing gravity sewer system to


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handle to ultimate loading has been calculated and presented using a spread sheet, which predicts the existing sewer in Crownwall Street between manholes A3 and A8 will be above capacity with ultimate flows.

6.3. Esler and Associates Existing Capacity: Have calculated the capacity of the existing system using Reticulation Sewer Minimum and Maximum Tenements Charts with in the WSA specifications and the Albury City council specifications. Esler’s report predicts the existing sewer in Crownwall Street between manholes A3 and A8 will be at capacity with ultimate flows. The maximum number of lots from the east of the highway can be 694 to achieve full capacity, Eslers predicted ultimate number of lots from the east of the highway is 703, If catchments 5, 9 and 13 are removed the ultimate number of lots is 532 and the existing sewer in Crownwall Street will not be at maximum capacity.

6.4. Pump Station Control: With correct sizing and control of the pump stations potential overloading of the system can be effectively mitigated, including re-sizing of existing pump station PS No. 2 as recommended by the DEUS report.

6.5. Storm Allowance: Both methods of calculating future loadings assume a significant Storm Allowance and the actual PWWF may be significantly less than calculated if Storm Water does not infiltrate into the system at the assumed rate. Particularly on new gravity main sewer systems with correct materials and construction methods the storm infiltration can be significantly reduced. Further discussion and calculations in Section 7.

7. Storm Allowance:

7.1. DEUS Assumption: A Storm allowance of 0.058L/ET.s has been adopted to calculate the

existing capacity and ultimate capacity of the existing sewer system. This storm allowance is consistent with the NSW Public Works Department Manual Of Practice – Sewer Design Section 4 and is referred to in a number of NSW council specifications.

7.2. Alternative Storm Allowance: An alternative storm allowance can be calculated using Water Services Association of Australia (WSA 02-2002) Sewerage Code of Australia Appendix B

Design Flow=PDWF+GWI+IIF PDWF : Peak Dry Weather Flow GWI: Ground Water Infiltration IIF: Peak rainfall dependent infiltration Below is the calculation of the IIF: Calculations based on The Rock town site West of the Highway. IIF = 0.028 * Aeff * C * I Where Aeff = Effective Area C =Leakage Severity Coefficient I =Function of rainfall intensity. AEff = A * (Density / 150)0.5 A = Area = 109 Hectare Density = EP(Equivalent Population) / A EP =Equivalent Population = 2.7 * Tenements(368) = 994 Density = 994 / 109 = 9.12 Ten/Hec AEff =109 * (9.12 / 150)0.5 = 26.9 C is determined from Table B1 (WSA Appendix B) C = Saspect + Naspect

Saspect (Soil Aspect) assumed to be 0.4 Naspect (Network Aspect) assumed to be 0.4


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C = 0.4 + 0.4 = 0.8 I = I1,2 * Factorsize * FactorContainment I1,2 = 1 hr duration intensity = assume 22 (Canberra figure) Factorsize = (40 / A)0.12 = (40 / 109)0.12 = 0.89 FactorContainment= From Table B3 use 1.0 I =22 * 0.89 * 1.0 = 19.5 IIF = 0.028 * 26.87 * 0.8 * 19.5 = 11.73 l/sec For the assumed number of Tenements of 368 Storm Allowance = IIF / Tenements = 11.73 / 368 = 0.03 L/ET.s

7.3. Sewer Main Pipe Capacity: Table 3.8 (DEUS Report) highlights sewer line A will be in part over capacity with PWWF at ultimate development, however the calculation have been based on a Storm Allowance of 0.0058L/ET.s. It has also been noted in the report that council operation staff has not observed any overflows or operational issues with the system. The actual Storm Infiltration may be better estimated from the WSA specifications as per the calculation in 4.2 above.

7.4. Alternative Ultimate Flows in Sewer Line A: Looking at the worst case sewer line A8-A9 as shown in table 3.8 (DEUS Report) it has been calculated the ultimate PWWF is 47.8 L/s, by reducing the assumed Storm Allowance from 0.058 to 0.03 L/ET.s the PWWF may be as little as 25.8 L/s which is 94% of the pipe capacity.

7.5. Example of Actual Measured Storm Flows: Elser and Associates has recently measured and reported the Storm Water Infiltration into a newly constructed sewer main system servicing 85 lots in new subdivision at Albury. The calculated Storm Flow was 0.007 L/s or 12% of the 0.058 L/s allowance. With further shaping of the surface around the manhole lids it is expected the Storm Flow will reduce further.

7.6. Verification of Storm Flow: Esler and Associated agree with the DEUS comment ‘it is recommended that Council obtain further data to verify the level of flows that are actually experienced in wet weather for Line A’.


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8. Unit Cost Comparison: 8.1. Construction Unit Costs: The DEUS and Esler’s Reports have assumed unit rates for

construction of the sewer mains, pump stations and sewer rising mains. 8.2. Table of Comparison of Construction unit Costs:

Unit Costs Item Units DEUS Esler

100mm dia main trenching depth 0-1.5m m $165 - 100mm dia main trenching depth 1.5-3m m $215 - 150mm dia main trenching depth 0-2m m $250 $100 150mm dia main trenching depth +2m m $365 $120 225mm dia main trenching depth +2m m $375 $165

Rock Allownace m $12.00 $27.60

Manhole 0-2.5mtrs each $3,100 $2,800 Manhole +2.5mtrs each $3,100 $3,200

Restoration / Landscaping Surface m/pipe $6.00 $15.00

Testing of pipes m $1.20 $4.40 Site Establishment visit $24,000 $20,000

Pump Station 1 inc Supply, Construction, Telemetry unit $272,000 $192,000 Pump Station 1 inc Supply, Construction, Telemetry unit $302,000 $192,000 Pump Station 1 inc Supply, Construction, Telemetry unit $242,000 $192,000

Sewer Rising Main Pump 1 150dia m $84 $110 Sewer Rising Main Pump 2 150dia m $84 $110 Sewer Rising Main Pump 2 150dia m $84 $110

8.3. Professional Fee Unit Rates: Fees for engineering design, survey, engineering management and work as executed have been estimated primarily as percentages of constructions costs. Costs have been itemized differently in each report, summary of fees are listed below.

8.4. Table of Comparison of Professional Fees Unit Costs

Item Units DEUS Esler

Survey, Investigation and Design % 20 - Engineering Design % - 10 WAE per catchment item $6,000 -

Engineering / Construction Management % 10 - Engineering / Construction Management /WAE % - 10

Topo Survey Per Hec - $500 Easement Creation Per Lot - $1,200

Environmental Per Stage $24,000 $5,000


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9. Overall Construction Costs for the Sewer System DEUS: 9.1. Construction Costs Pump Stations: DEUS has calculated the overall cost of the pump

stations by considering each pump station and several alternatives have been given for the route and discharge position of the SRM. For comparison purposes options 4E and 5E have been used below.

9.2. Construction Cost Sewer Reticulation: The construction cost of Stage 1 has been calculated from an assumed layout, design and unit rates. Construction cost for stages 2, 3 and 4 have been calculated by using a per/hectare rated calculated from Stage 1.

9.3. Possible Over Estimation by DEUS: It should be noted the construction cost for the sewer reticulation of stage 1 includes approximately 350mtrs of 225dia reticulation sewer from the development area to the new pump station No.4 (Sewer Line 4A/1 to 4A/4) including 4 manholes. The per hectare rates calculated includes this portion of the sewer reticulation and therefore is possibly over estimated for calculation of construction cost of stages 1, 3 and 4. It is estimated the over estimation in construction costs for the all 4 stages could be in the order of $750,000.

10. Overall Construction Costs for the Sewer System Esler and Associates: 10.1. Construction Costs Pump Stations: The supply cost of each pump station has been assumed

to be $130,000. Installation Costs for each pump station has been assumed to be $50,000. Rates have been estimated from actual cost of similar pump stations constructed at other subdivisions.

10.2. Construction Cost Sewer Reticulation: The construction cost of all catchment areas has been calculated from a preliminary layout, design and unit costs. Unit costs have been estimated from actual contract rates of other subdivisions project managed by Esler and Associates in Albury and Wagga Wagga

11. Overall Construction Cost Comparison: 11.1. Cost Comparison: The table below summaries the overall construction cost for a sewer

reticulation system including 3 pumps stations on the east side of the highway at The Rock. The catchment area has been determined to be the combined DEUS Stage 1, 2, 3 and 4 catchments and similarly Eslers overall catchment less catchments 5, 9 and 13. DEUS


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11.2. DEUS Cost Options: Costing options 4E and 5E have been used in the table. 11.3. Overall Cost Comparison Table: Item NSW Department Cost Esler and Associates Cost Reticulated Gravity Sewer $4,123,000 $2,690,000 Pump Stations $1,002,000 $576,000 Sewer Rising Main $666,000 $308,000 Decommission Septic Tanks $88,000 $114,000 Contingency $0 $369,000 Sub Total Construction $5,879,000 $4,057,000 Survey, Eng Design, Eng WAE - Sewer $907,000 $292,000 Survey, Eng Design, Eng WAE - Pumps $222,000 $109,000 Eng / Const Management - Sewer $438,000 $292,000 Eng / Const Management - Pump $182,000 $109,000 Environmental $133,000 $51,000 Sub Total Professional Fees $1,882,000 $853,000 Easement Creation $0 $170,000 Overall Total Cost $7,761,000 $5,080,000

12. Conclusion:

Both reports have found the study area is generally suitable for a gravity reticulated system, with the natural grade of the land from the south east to the intersection of Olympic Hwy and Mangoplah Rd. The proposed reticulated sewer system would include 3 sewer pump stations, The pump stations would discharge to existing sewer system with in the town site west of the Olympic highway. The capacity of the existing sewer system west of the highway will be close to or at full capacity with ultimate sewer loading, a significant factor in determining the ultimate PWWF is the assumed Storm Allowance, accurate determination of the PWWF can be determined by site measurement of flows during storm events. It has determined up to 977 and 532 lots by DEUS and Esler and Associated respectfully could be serviced by the proposed catchment area. The overall cost to fully service the catchment area is $7,761,000 and $5,646,300 calculated by DEUS and Esler and Associated respectfully. The most significant difference in the cost estimation is the assumed unit rates, Esler and Associates unit rates are approximately 70% of the assumed rates by DEUS. Both DEUS and Esler and Associates have estimated the professional fees to be approximately 30% of the construction cost, because Esler and Associates construction cost is lower than DEUS the estimated professional fees are also lower.

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