Innovation in Stormwater sediment separation. David Carew (MW), Tony Short (MW) & Charles Mellish (MWH)

Transcription

1 Innovation in Stormwater sediment separation David Carew (MW), Tony Short (MW) & Charles Mellish (MWH)

2 Urban stormwater sediment management Innovative solution required 500 ponds 400,000 m3 functional volume 50,000 tonne annual maintenance program 40-50% prescribed waste Sediment status % of total volume Current program Future program Solid inert (clean fill) 30% Local area disposal Local area disposal Solid inert (clean fill) 30% Landfill Reuse via facility Low level contamination High risk contamination 30% Landfill Reuse via facility 10% Landfill Landfill

3 Sediment management costs $20,000,000 $11,700,000 $15,000,000 $10,000,000 $3,900,000 BAU disposal cost 5% Cat B landfill cost $5,000,000 $1,900,000 Sediment management $ ,000 tonne ,000 tonne ,000 tonne New solution to delivering activity required

4 Greater Melbourne Port Phillip & Westernport region Port Phillip Bay Region = 13,000 km 2

5 Rapid growth in constructed wetland systems to Development funded Melbourne Water

6 Sediment pond function Sediment ponds are designed to capture >125µm particles for a given flow. Protect other assets. 5 yr accumulation volume.

7 Constrained urban context Stormwater treatment is required following development. Sediment ponds to be managed

8 Current desilting process

9 Maintenance access Assets not always set up to enable maintenance. Section of rock weir removed to enable works

10 Dewatering

11 Debris removal Onsite sediment processing to remove debris has traditionally been done on dry material.

12 Debris removal Onsite sediment processing to remove debris has traditionally been done on dry material. Problems: Blanking of screens Dust generation

13 2ENVI1, 24 2ENVI2, 15 2ENVI3, 8.8 4ENVI1, 44 4ENVI2, 2.5 4ENVI3, 3.6 6ENVI1, 17 6ENVI2, 17 6ENVI3, 54 1ENVI1, 380 1ENVI2, 520 1ENVI3, 490 3ENVI3, 400 5ENVI3, 420 5ENVI1, ENVI2, 800 7ENVI1, 550 7ENVI2, 530 7ENVI3, 280 8ENVI1, 210 9ENVI1, 57 9ENVI3, 44 10ENVI1, ENVI2, 77 9ENVI2, ENVI3, 150 1ENVI1, 21 1ENVI2, 21 1ENVI3, 23 13ENVI1, 41 13ENVI2, 56 3ENVI3, 15 4ENVI1, 11 4ENVI2, 21 14ENVI3, 50 5ENVI1, 16 15ENVI2, 94 15ENVI3, 81 6ENVI1, 14 6ENVI2, 14 6ENVI3, 15 7ENVI1, 21 7ENVI2, 17 17ENVI3, 33 8ENVI1, 19 8ENVI2, 22 18ENVI3, 26 12ENVI1, ENVI3, 420 3ENVI1, ENVI2, ENVI2, ENVI3, 1600 Zinc (mg/kg) 3ENVI2, 3400 Prescribed waste implications - Zinc analyses 3600 Zinc, Zn mg/kg

14 Prescribed waste implications - Zinc analyses

15 Prescribed waste implications - C10-C36 analyses

16 Prescribed waste implications - C10-C36 analyses

17 Dredging and Sediment Separation System tender Safe sediment removal all year round, Separate sediment fractions, Dewater sediments, Minimise impacts on public amenity.

18 Dredging and Sediment Separation System tender Safe sediment removal all year round, Separate sediment fractions, Dewater sediments, Minimise impacts on public amenity. Maximise reuse of sediments minimise landfill disposal, Minimise overall costs associated with sediment removal and disposal, Enable management of assets.

19 Dredging and Sediment Separation System tender Used earlier investigations and market research to define the problem, Pretender undertook international technology investigation, HazWaste Fund grant to introduce an innovative solution, Engaged consultant to provide independent review, Tight timeline.

20 Sediment - Dredge and Sediment Separation System (DSSS) MW Capex (including HazWaste Funding Contribution) MW Opex Description of Activity Aim: 5 days on site Debris/Litter to landfill Coarse fraction (0.5 to 20mm) reuse Fine fraction (0.1 to 0.5mm) reuse Maximise re-use and diversion from landfill Coarse Fraction. Dry (spadable) >100 to 500µm (0.1 to 0.5mm) up to 20mm material Stockpile for transport Approx. 60T to 540T (10-90%) Reuse material Transport Functional Requirement Sediment contamination test Risk assessment Low risk Hydrocyclone <100 to 500µm (0.1 to 0.5mm) and water Fine Fraction > 20um dry solids Continue monitoring Undertake sediment contamination assessment to determine risk profile and reuse potential <40mm material and water Coagulant and flocculent dosing Geo-fabric bag for dewatering Approx. 6 months Water NTU <20 High risk Transport YES Wet Trommel 40mm screen Vegetative material, debris and litter mm Sediment pond or drainage system Landfill Dredged material, up to 65mm material and water Transport Sediment pond or drainage system Asset condition assessment: Is pond functional? NO Work scope and comms plan. Site prepara tion Mobilise to site 1 day Dredge sediment 3 days 1000m3 of pond volume dredged = 600T solid De-mobilise from site 1 day Maintain asset register De-silt works planning and site preparation. 2 weeks 2 years De-silting operation 5 days Site clean up Fine fraction removal Sediment pond desilting Condition monitoring Ongoing maintenance as per SAMP

21 Preferred solution from tender Local supplier selected to deliver solution and commission equipment. Site preparation Sediment extraction Sediment processing Process monitoring Fine fraction flocculation Fine fraction dewatering O&M and SoP Mini-AD Dredge Mini-SD Dredge Mobile debris and coarse fraction separation Incorporated post tender Polymer dosing Geo-bag technology Documentation and training

22 Urban Dredge (Mini AD) site setup

23 Urban dredge sediment extraction Trailer deployed dredge with three day productivity of 1000m3 excavation. (600 tonne solids).

24 Mobile sediment separation Trailer mounted unit to access majority of urban sediment ponds. Separates: Debris 300µm to 20mm < 300µm

25 Mobile sediment separation

26 Mobile sediment separation

27 Solids measurement and Polymer dosing

28 Fine fraction dewatering Photo credit: Apex Envirocare Roselea Compensating Basin, Stirling (WA)

29 Operational trial Ten stormwater systems Eighteen ponds >500 samples for analysis

30 Operational trial Ten stormwater systems Eighteen ponds >500 samples for analysis Mobility Sediment extraction and processing capacity Separation effectiveness Capture of fine fraction Ensure process meets EPA requirements Benefit to prescribed waste reduction

31 Constrained urban context Operational flexibility to be tested in tight urban setting. Sediment ponds to be managed

32 Site Management plans

33 Prescribed waste reduction of 27% expected 2345 tonne Melbourne Water Asset ID Name Prescribed waste category Volume m^3 Material mass (t) % >300µm Volume >300µm m^3 Predicted Prescribed Material m^3 Predicted Prescribed Material mass (t) DST401 Dandenong Valley Wetland Category C DWL259B Golflinks Rd Wetland Fill Material DST322 A Caroline Springs Wetland complex Category C DST322 C Caroline Springs Wetland complex Category C DST322 D Caroline Springs Wetland complex Category C DST132B Watervale Stage 1 sediment ponds Fill Material DST132C Watervale Stage 1 sediment ponds Fill Material DST132E Watervale Stage 1 sediment ponds Fill Material DST161 Evans Rd RB Category C DST068A Karkarook Sediment pond Category C DST054 Troups Creek South Category C DST172 A Fairbairn Rd Category B DST172 B Fairbairn Rd Category B DST389A Botanica Springs Fill Material DST382A Marriott Waters Sediment Ponds Fill Material DST382D Marriott Waters Sediment Ponds Fill Material DST382E Marriott Waters Sediment Ponds Fill Material

34 On-site sieve assessment 1180µm 300µm 200µm 106µm

35 Sampling and Monitoring plan Location # Samples Flow Volume % Solids in slurry Residual polymer test ph Turbidity TSS Redox Soluble contaminates ANZECC suite Contaminates EPA-IWRG621 Contaminates EPA-IWRG631 Asbestos Particle size distribution Total weight Sediment pond In-situ sediments 10 Sediment pond water 10 Dredger outlet Hydrocyclone inlet Rotary drum solids storage bin Hydro cyclone overflow outlet Hydrocyclone under flow solids storage bin Continuous Continuous Continuous 10 Polymer dosing inlet Continuous Geo-textile bag filtrate 10 Geo-textile bag retained solids 10

36 BAU sediment reuse vs landfill disposal Melbourne Water Sediment pond network 500+ ponds. Functional volume 400,000m3 Group A IWRG621 Clean Fill Group B IWRG621 CatC contaminated soil IWRG631 Non-prescribed Industrial Waste MW low risk category Group C IWRG 621 or 631 Cat C, B or A MW High Risk Category BAU process Annual sediment management program 50,000tonne ponds managed Contamination Risk Assessment 4 samples per pond 1 sample EPA Scan analysis and 3 samples Metals & C10-36 analysis Group A 60-65% Sediment categorisation Group C 5-10% 30% of total volume Group B 30% Local reuse Landfill 70% of total volume 30-35% of total volume

37 Future sediment reuse vs landfill disposal Melbourne Water Sediment pond network 500+ ponds. Functional volume 400,000m3 Group A IWRG621 Clean Fill Group B IWRG621 CatC contaminated soil IWRG631 Non-prescribed Industrial Waste MW low risk category Group C IWRG 621 or 631 Cat C, B or A MW High Risk Category Sediment management utilising DSSS and reuse Annual sediment management program 50,000tonne ponds Contamination Risk Assessment 4 samples per pond 1 sample EPA Scan analysis and 3 samples Metals & C10-36 analysis Group A 60-65% Sediment categorisation Group C 5-10% of total volume 30% of total volume 30-35% of total volume Group B 30% of total volume Landfill 15-20% of total volume (up to 70% reduction of waste to landfill) DSSS sediment particle separation and dewatering EPA HazWaste fund supported DSSS sediment particle separation and dewatering EPA HazWaste fund supported DSSS sediment particle separation and dewatering EPA HazWaste fund supported Fine Fraction with contamination 10% of total volume Local reuse Melbourne Water sediment processing facility Product QA Coarse fraction 20% total vol Reuse Combined reuse 80-85% of total volume

38 Revised Sediment management costs $16,000,000 $6,240,000 $12,000,000 $8,000,000 $4,000,000 $1,900,000 $2,112,500 Disposal cost 5% Cat B landfill cost Sediment management $ ,000 tonne ,000 tonne ,000 tonne Approx $5.5M pa saving on disposal costs in 2023

39 Challenges Manufacturing customised solution, Defining environmental risks and mitigations, Stakeholder management, Keeping to timeline, Being safe.

40 Actions following commissioning trial Complete trial and bring new method into business practice.

41 Actions following commissioning trial Complete trial and bring new method into business practice. Report on benefits.

42 Actions following commissioning trial Complete trial and bring new method into business practice. Report on benefits. Ensure regulatory assets are maintained to provide design service.

43 Actions following commissioning trial Run trial and bring new method into business practice. Report on benefits. Ensure regulatory assets are maintained to provide design service. Define sediment treatment facility and improve reuse to drive down costs.

44 Questions?