Cost Effective Stormwater Asset Management Sarath Manatunga

Abstract

All councils are required to manage and maintain the stormwater assets which are owned by the council. What is the economical way of stormwater asset management? Today, I will share my knowledge and experience on the following topics. 1. What are the main stormwater asset categories? 2. Methods of data collection, developing asset register, defects & identification, 3. Cost & benefit analysis of alternative defect identification method. What are the main stormwater asset categories? Stormwater Drainage: 1. Open channel 2. Headwall 3. Gully pit 4. Field inlet pit 5. Maintenance pits 6. Litter collection traps 7. Wetlands Culverts: 1. Box Culvert 2. Pipe Culvert 3. Headwall Methods of data collection, asset register, defects identification, methods Data collection: Most councils already have significant data on their stormwater assets including type, location, size, condition, age etc. This data is gathered over several years and usually called an Asset Register. However, if the data is not available, the important information that needs to be collected is as below. 1 Location identification (Road name, segmentation, plant name etc.); 2 Urban/Rural Environment 3 Quantity (length, width, depths, diameter); 4 Attribute details (type); 5 Componentisation (It is important as per the CPA guidelines, that Assets that are made of significant parts, have different lifecycles, should be depreciated separately); 6 Important points in data collection; • It is very economical to use a tablet and/or GPS data collecting unit. • Plan and identify the type of data to be collected • Develop a standard methodology and consider the practicality. Avoid heavy raining days, heavy lifting and use correct lifting equipment, Wet days may be slippery, Consider safety, Steep & Overgrown situation, Snakes, Confined space etc • Create guidelines by reading published documents • Determine how sophisticated the location data should be, for example: (1or 2m accuracy, 5m accuracy etc) • Use the flow of direction to start with (Treatment plant – Inlet to outlet, Roads - Township to rural properties etc.) Assets register development 1 Develop the asset register by analysing the collected data frequently 2 Group the similar assets under the asset category: 3 Determine the calculation quantity and unit. 4 Develop a component code for each asset to calculate unit rate, useful life etc., a. Pipe type & diameter or Pipe type, diameter & depth b. Pit length, width & depth, c. Urban rural or hierarchy Stormwater asset defects Pipe defects: • Major joint displacement • Spalling and corrosion • Fractures Pit defects • Spalling and corrosion • Fractures • Cracking Defects identification, methods; 1 CCTV 2 Quick view camera; 3 Visual condition assessment Cost & benefit analysis of alternative defect identification method CCTV Negatives 1. Relatively costly method 2. Relatively high time consume Positives 1. Relatively accurate details 2. Can obtain details of the joints very well Quick view camera Negatives 1. May not be able to view the pipe if it is deformed 2. Unable to view the joints clearly 3. Lower pitcher quality. Positives 1. low cost