COOPER STREET, EPPING STORMWATER MANAGEMENT STRATEGY. May Cooper Street Pty Ltd

Size: px
Start display at page:

Download "COOPER STREET, EPPING STORMWATER MANAGEMENT STRATEGY. May Cooper Street Pty Ltd"

Transcription

1 COOPER STREET, EPPING STORMWATER MANAGEMENT STRATEGY May 2017 Cooper Street Pty Ltd

2 Disclaimer Dalton Consulting Engineers Pty Ltd This report has been prepared solely for the benefit of Cooper Street Pty Ltd and Dalton Consulting Engineers Pty Ltd. No liability is accepted by this company or any employee or sub-consultant of this company with respect to its use by any other person. This disclaimer shall apply notwithstanding that the report may be made available to other persons for an application for permission or approval or to fulfil a legal requirement. Revision No: Date: Description: Document History 1 May 2017 Stormwater Management Strategy v1 Prepared: Reviewed: Approved: J. Baumann AN: J. McGrath AN: T. Liakopoulos AN: Page i

3 Executive Summary This report outlines the stormwater strategy for a proposed 9.72-ha industrial subdivision at Cooper Street, Epping. The site is bounded by Cooper Street to the north, a quarry access road to the east, and industrial development to the west and future drainage reserve and existing quarry to the south, as shown in Figure 1. The site is zoned for industrial use. Figure 1: Location of subject site showing adjacent land use Minor event flows are defined by the City of Whittlesea in the Engineering Design and Construction Manual (VPA (formerly GAA), 2011) as 10-year annual recurrence interval (ARI) flows which will be conveyed via the underground drainage network to the legal point of discharge. The site is part of Melbourne Water s Edgars Creek DSS (4440), and a connection to the scheme at the south-eastern corner of the site has been nominated by Melbourne Water. Page ii

4 Major event runoff is defined as runoff generated by the 100-year ARI rainfall. The 100-year runoff will be safely conveyed through the subject site. Flows greater than the capacity of the underground drainage will be conveyed overland via roadways. Stormwater runoff is summarised in Table 1. Table 1: Stormwater runoff summary for the subject site at 1620 Centre Road, Springvale Location ARI Existing runoff (cu. m/s) Subject Site Developed runoff (cu. m/s) 10-year year It is proposed that contributions be paid to the Edgars Creek DSS in lieu of on-site water quality treatment. The land lies within the area covered by Melbourne Water s Edgars Creek Drainage Scheme. Compliance with the Scheme is mandatory for Drainage Requirements on Subdivisions. Melbourne Water will provide a formal Offer for the provision of drainage facilities on application and at the time of submission to Council of an Application for Planning Permit for Subdivision. Melbourne water s Offer will specify the Scheme Contributions as specified in this Report, at the Contribution rates current at the time of application. The Contributions may be offset to some extent by constructing water quality treatment and Scheme pipe works in lieu of payment, by agreement with Melbourne Water. Page iii

5 Contents Executive Summary ii 1. Introduction 1 2. Site overview Existing condition Developed condition 3 3. Stormwater management Stormwater management: Minor event flow Major event flow Edgars Creek DSS contributions External Catchment 5 4. Stormwater Quality 6 5. Conclusions 7 2. Appendices 8 A. Melbourne Water s Edgars Creek DSS (4440) 8 B. Complete Drainage Calculations 9 Tables Table 1: Stormwater runoff summary for the subject site at 1620 Centre Road, Springvale... iii Table 2: Minor event (Q 10 ) flows for development... 5 Table 3: Major event (Q 100 ) flows for development... 5 List of Figures Figure 1: Location of subject site showing adjacent land use... ii Figure 2: Location of subject site showing existing condition... 1 Figure 3: Location of the subject site within the Edgars Creek DSS... 2 Figure 4: Subject site in the developed condition... 3 Figure 5: Melbourne Water stormwater quality contribution rates... 6 Page iv

6 1. Introduction This report presents the stormwater management strategy for the proposed industrial development of Cooper Street, Epping The 9.72-ha subject site is located within the City of Whittlesea. In the existing condition, the site is mostly vacant with the remains of a recently demolished dwelling and sheds at the north-eastern corner of the site. The subject site in the existing condition is shown in Figure 2. Figure 2: Location of subject site showing existing condition The site is bounded by Cooper Street to the north, existing industrial development to the west, a future drainage reserve and existing quarry to the south, and a quarry access road and the Hume Freeway to the east. In accordance with Whittlesea City Council requirements for industrial development, minor (10-year year average recurrence interval (ARI)) and major (100-year ARI) flows will be determined for both the existing and developed condition. Page 1

7 2. Site overview 2.1 Existing condition The subject site at Cooper Street, Epping comprises approximately 9.72 ha. The subject site is mostly vacant with the remains of existing buildings in the north-east and patchy vegetation covering the remainder of the site. The site generally falls from north-west to south-east. The lowest elevation is in the south-eastern corner. The subject site is within Melbourne Water s Edgars Creek DSS (4440). Based on the plan for the Edgars Creek DSS, the subject site will connect to the scheme at the south-east corner of the subject site. Existing culverts under the Hume Freeway will convey flow to the scheme infrastructure, as shown in Figure 3. A large-scale plan of the Edgars Creek DSS is included in Appendix A. Figure 3: Location of the subject site within the Edgars Creek DSS Page 2

8 2.2 Developed condition The entire site will be developed for industrial use. Stormwater will drain to the south-eastern corner of the site where a connection will be made to the Edgars Creek DSS. An indicative layout of the developed condition, including major-event 100-year flow paths, is shown in Figure 4. In the developed condition, safe overland flow paths will convey runoff from the site and toward Edgars Creek DSS infrastructure. Figure 4: Subject site in the developed condition The land lies within the area covered by Melbourne Water s Edgars Creek Drainage Scheme. Compliance with the Scheme is mandatory for Drainage Requirements on Subdivisions. Melbourne Water will provide a formal Offer for the provision of drainage facilities on application and at the time of submission to Council of an Application for Planning Permit for Subdivision. Melbourne water s Offer will specify the Scheme Contributions as specified in this Report, at the Contribution rates current at the time of application. The Contributions may be offset to some extent by constructing water quality treatment and Scheme pipe works in lieu of payment, by agreement with Melbourne Water. Page 3

9 3. Stormwater management The 9.72-ha subject site is located within the City of Whittlesea and is subject to council stormwater guidelines. The stormwater guidelines reference the Victorian Planning Authority (VPA) Engineering Design and Construction Manual (VPA (formerly GAA), 2011). Minor and major flows have been calculated using the Rational Method (Equation 1). The time of concentration has been calculated using Equation 2. As the site is within a Melbourne Water drainage scheme, retention of stormwater will not be required. In relation to stormwater quality, payment of offsets is available as part of the Edgars Creek DSS (refer to Section 4). Detailed flow calculations are included as Appendix B. Equation 1: Rational method Where: Q = design discharge (cu. m/s) C = runoff coefficient I = rainfall intensity (mm/hr) A = catchment area (ha) 360 Equation 2: Time of concentration t c = t 1 + t 2 + t 3 Where: t c = time of concentration t 1 = time to reach the pipe or kerb and channel t 2 = kerb and channel travel time (from Australian Rainfall and Runoff) t 3 = pipe travel time from Australian Rainfall and Runoff; or = L/V Where: L = pipe length V = velocity Page 4

10 3.1 Stormwater management: The site will form a single stormwater catchment of 9.72 ha. The catchment naturally grades to the southeastern boundary. The site will connect to Melbourne Water s Edgars Creek DSS at the south-eastern corner of the site. The development will comprise industrial land-use Minor event flow Minor event (10-year average recurrence interval (ARI)) flows will be conveyed via the underground drainage network to the Edgars Creek DSS. The 10-year ARI flows are shown in Table 2. Complete drainage calculations are included as Appendix B Major event flow Table 2: Minor event (Q10) flows for development Catchment conditions Existing 0.43 cu. m/s Developed 1.39 cu. m/s Major event runoff is defined as runoff generated by the 100-year ARI rainfall. The 100-year runoff will be safely conveyed through the subject site. Gap flow is defined as 100-year ARI 10-year ARI flows. Gap flows will be conveyed overland via roadways. Internal roads will convey gap flows to a connection to the Edgars Creek DSS. Major event flows are shown in Table 3. Complete drainage calculations are included as Appendix B. Table 3: Major event (Q100) flows for development Catchment conditions Existing 0.88 cu. m/s Developed 2.86 cu. m/s Gap flow (100-year 10-year) 1.47 cu. m/s Edgars Creek DSS contributions The subject site is located within Melbourne Water s Edgars Creek DSS. As a result of its location, hydraulic contributions can be made for the control of runoff downstream of the subject site. Based on the Melbourne Water contribution rates for the Edgars Creek DSS, the hydraulic contribution payable as of 10 May 2017 is $852,172, as shown in Figure External Catchment No external flow is catered for in the underground drainage, overland flow paths or retarding basin. Page 5

11 4. Stormwater Quality The subject site is located within Melbourne Water s Edgars Creek DSS. The DSS will provide full stormwater quality treatment for all developed flows. The DSS will enable the subject site to comply with Council and Melbourne Water Drainage Requirements without the need for on-site stormwater quality infrastructure. Based on the Melbourne Water contribution rates for the Edgars Creek DSS, the hydraulic contribution payable is $852,172 and the water quality contribution payable as of 10 May 2017 is $241,853, as shown in Figure 5. A reduction in contributions will occur if more than 0% stormwater quality is provided on -site. Figure 5: Melbourne Water stormwater quality contribution rates Page 6

12 5. Conclusions This report outlines the stormwater strategy for the proposed industrial development at Cooper Street, Epping. The stormwater will be effectively managed both during and after development occurs. The drainage strategy for the subject site takes into account City of Whittlesea stormwater requirements and the location of the subject site within Melbourne Water s Edgars Creek DSS. Minor flows (10-year ARI flows) in the developed condition will be conveyed by underground drainage. Minor flows will drain to the connection to Melbourne Water s Edgars Creek DSS. Major flows in excess of the 10-year ARI up to the 100-year ARI will be conveyed safely overland by roads to the connection of Melbourne Water s Edgars Creek DSS. It is recommended that stormwater quality contributions to the Edgars Creek DSS be made in lieu of onsite stormwater quality treatment. The payment of hydraulic and water quality contributions will ensure that the site is able to take advantage of the stormwater management and treatment provided by the Edgars Creek DSS. Page 7

13 2. Appendices A. Melbourne Water s Edgars Creek DSS (4440) Page 8

14 Subject Site

15 B. Complete Drainage Calculations Page 9

16 PEAK FLOW CALCULATION SHEET (RATIONAL METHOD) JOB NAME: Cooper Street, Epping JOB No.: C' From the VPA (previously GAA) Engineering Design and Construction Manual for the North-West Region (Hume and Whittlesea) Rural (Existing Condition) Developed Industrial Fraction Impervious 0.1 Fraction Impervious 0.9 COEFFICIENT OF RUNOFF Frequency factor (Fy) Cy COEFFICIENT OF RUNOFF Frequency factor (Fy) Cy C10 n/a C10 n/a C C C C C C C C C C C C Fraction impervious from Engineering Design and Construction Manual Fraction impervious from Engineering Design and Construction Manual G:\Designdata\12700\ to 425 Cooper Street Epping\Documents\RoadsDrainage\12701my1117G_DrainageCalcsRationalMethod.xls

17 Job Description: 415 Cooper Street, Epping Job Number: Compiled by: JMB Date: 11-May-17 Location and ARI 415CooperSt-10 ARI a b c d e f g Point Length Velocity Tc Area C Ae SAe I 10 Q 10 m m/s mins ha ha ha mm/hr m 3 /s Subject Site (at south-east corner) Where: Catchment lengths based on existing contours. Assume 10-year existing condition flows are overland with an average velocity of 1 m/s Tc = Time to concentration = 6 + ((Length/Velocity)/60) Ae = effective area = Area * C (co-efficient of imperviousness) I 10 = 10-yr Intensity, which is derived from the co-efficients a to e * Tc Q 10 = 10-yr Flow = (Area * Intensity)/360 G:\Designdata\12700\ to 425 Cooper Street Epping\Documents\RoadsDrainage\12701my1117G_DrainageCalcsRationalMethod.xls 2

18 Job Description: 415 Cooper Street, Epping Job Number: Compiled by: JMB Date: 11-May-17 Location and ARI 415CooperSt-10 ARI a b c d e f g Point Length Velocity Tc Area C Ae SAe I 10 Q 10 m m/s mins ha ha ha mm/hr m 3 /s Subject Site (at south-east corner) Where: Catchment lengths based on proposed development layout. Assume 10-year flows are piped and average velocity is 1 m/s Assume overland flow across ENPTC and Protected Zone at 1 m/s Tc = Time to concentration = 6 + ((Length/Velocity)/60) Ae = effective area = Area * C (co-efficient of imperviousness) I 10 = 10-yr Intensity, which is derived from the co-efficients a to e * Tc Q 10 = 10-yr Flow = (Area * Intensity)/360 G:\Designdata\12700\ to 425 Cooper Street Epping\Documents\RoadsDrainage\12701my1117G_DrainageCalcsRationalMethod.xls 3

19 Job Description: 415 Cooper Street, Epping Job Number: Compiled by: JMB Date: 11-May-17 Location and ARI 415CooperSt-100 ARI a b c d e f g Point Length Velocity Tc Area C Ae SAe I 100 Q 100 m m/s mins ha ha ha mm/hr m 3 /s Subject Site (at south-east corner) Where: Catchment lengths based on existing contours. Assume 100-year flows are overland with an average velocity of 1 m/s Tc = Time to concentration = 6 + ((Length/Velocity)/60) Ae = effective area = Area * C (co-efficient of imperviousness) I 100 = 100-yr Intensity, which is derived from the co-efficients a to e from AR&R * Tc Q 100 = 100-yr Flow = (Area * Intensity)/360 G:\Designdata\12700\ to 425 Cooper Street Epping\Documents\RoadsDrainage\12701my1117G_DrainageCalcsRationalMethod.xls 4

20 Job Description: 415 Cooper Street, Epping Job Number: Compiled by: JMB Date: 11-May-17 Location and ARI 415CooperSt-100 ARI a b c d e f g Point Length Velocity Tc Area C Ae SAe I 100 Q 100 m m/s mins ha ha ha mm/hr m 3 /s Subject Site (at south-east corner) Gap Flow Where: Catchment lengths based on existing contours. Assume 100-year flows are overland with an average velocity of 1 m/s Tc = Time to concentration = 6 + ((Length/Velocity)/60) Ae = effective area = Area * C (co-efficient of imperviousness) I 100 = 100-yr Intensity, which is derived from the co-efficients a to e from AR&R * Tc Q 100 = 100-yr Flow = (Area * Intensity)/360 G:\Designdata\12700\ to 425 Cooper Street Epping\Documents\RoadsDrainage\12701my1117G_DrainageCalcsRationalMethod.xls 5

21 Coefficient List ARI a b c d e f g ARR87 COOPERSTREET 415CooperSt E-05 ARR87 COOPERSTREET 415CooperSt E-05 ARR87 COOPERSTREET 415CooperSt E E-05 ARR87 COOPERSTREET 415CooperSt E E-05 ARR87 COOPERSTREET 415CooperSt E E-05 ARR87 COOPERSTREET 415CooperSt ARR87 COOPERSTREET 415CooperSt DURATION 1 Year 2 years 5 years 10 years 20 years 50 years 100 years 5Mins Mins Mins Mins Mins Hr Hrs Hrs Hrs Hrs Hrs Hrs Hrs