October 5 2011 Estimating Stormwater System Annual Maintenance and Repair Costs - A GIS Approach 2011 SESWA Annual Conference 2011 Southeast Stormwater Associated Annual Conference
Presentation Overview Purpose of developing annual repair and maintenance costs Local government level of service (LOS) GIS analysis considerations Asset management/risk approach Economic life model Additional considerations Brown and Caldwell 2011 SESWA Conference 05oct11 2
Purpose Develop justification for department budget Rationale for setup of Stormwater Utility Support for Stormwater Utility fee increase Proactive approach to managing stormwater system Brown and Caldwell 2011 SESWA Conference 05oct11 3
Level of service Stormwater system Culverts, inlets and pipes Ditches and swales Ponds and BMPs Streams Right-of-way Directly connected to ROW Justified community benefit AND budget available Public/private partnerships Brown and Caldwell 2011 SESWA Conference 05oct11 4
GIS Analysis Available inventory data Structures drop inlets and outfalls Pipe type CMP RCP HDPE/PVC Other Pipe size Pipe age/service life Pipe condition Brown and Caldwell 2011 SESWA Conference 05oct11 5
GIS Analysis Age/Service life Pipe Material Code Service Life Corrugated Metal Pipe CMP 20 Ductile Iron Pipe DIP 40 Steel Ductile Steel 30 High Density Polyethylene HDPE 80 Polyvinylchloride PVC 100 Reinforced Concrete Pipe RCP 50 Brown and Caldwell 2011 SESWA Conference 05oct11 6
GIS Analysis Priority Schedule Good Low Priority Medium Priority High Priority Unknown Good Low Priority Medium Priority High Priority Unknown Closed/Open Conduit Conditions New condition or some defects or cracks, but does not affect strength. No separation or leaking in cracks. Minor evidence of erosion but no evidence of flooding. Minimal defects, slight separation, no evidence of leaking/ evidence of moderate erosion and possible evidence of minor flooding. Displaced, crushed or collapsed sections, possibly affecting strength of structure or ability to function as designed. Evidence of leaking in cracks. Evidence of serious erosion and possible frequent flooding. Displaced, crushed or collapsed sections that prevents structure from functioning as designed. Evidence of severe erosion and frequent flooding. Pipe condition is not obtainable due to debris, sediment or water obstructing the view of more than 75% of the of the pipe. Structure Conditions New condition or some defects or cracks, but does not affect strength. No separation or leaking in cracks. Some defects or slight separation, no evidence of leaking, does not affect strength of structure. Displaced, crushed or collapsed sections, possibly affecting strength of structure or ability to function as designed. Missing manhole lids. Displaced, crushed or collapsed sections that prevents structure from functioning as designed. Structure condition is not obtainable due to debris, sediment or water obstructing the view of more than 75% of the of the structure. Brown and Caldwell 2011 SESWA Conference 05oct11 7
GIS Analysis - Assess your system statistics Assess number of miles per pipe size, type and condition Extrapolate to whole system Can factor if needed based on known density, land cover, etc. Brown and Caldwell 2011 SESWA Conference 05oct11 8
GIS Analysis System Statistics Example Maintained Stormwater System Pipes Greater Than 20 Years Old, All Conditions Length (miles) Diameter (inches)* Material Total Inventoried to Date CMP Other Plastic RCP 0 35.4 7.5 6.4 52.7 102.0 18 160.5 2.9 3.4 77.2 243.8 24 99.8 1.9 2.2 41.5 145.3 30 53.1 0.9 1.5 17.6 73.1 36 41.7 0.6 0.5 13.6 56.5 42 17.1 0.2 0.2 4.8 22.3 48 17.3 0.3 0.1 4.7 22.4 54 5.8 0.1-1.4 7.3 60 5.0 0.1 0.0 1.7 6.8 66 1.3 0.0-1.0 2.3 72 2.3 0.1-0.8 3.1 78 0.6 - - 0.9 1.5 84 0.3 0.0-0.8 1.2 90 0.1 - - 0.5 0.6 96 0.1 0.2-1.3 1.6 102 0.0 - - 1.0 1.1 108 0.1 - - 0.2 0.3 114 0.0 - - 0.3 0.3 120 0.3 0.1-2.8 3.2 Totals 440.8 14.9 14.3 224.7 694.6 If 75% of the system has been inventoried and remaining 25% similar in land use and density, then extrapolate out. 694.6/75% = 926.1 miles Brown and Caldwell 2011 SESWA Conference 05oct11 9
GIS Analysis Develop a cost table Review past construction bids Evaluate in-house repair and maintenance costs Blended average for repair vs. replacement Consider contractor vs. in-house staff Example Planning Level Stormwater Pipe Repair /Replacement Unit Costs Diameter (in) Replacement Cost per Foot Repair Cost per Foot Blended Cost per Foot 0 $200 $50 $155 18 $325 $119 $263 24 $350 $124 $282 30 $395 $139 $318 36 $450 $143 $358 42 $630 $158 $488 48 $660 $165 $512 54 $815 $204 $632 60 $1,030 $258 $798 66 $1,040 $260 $806 72 $1,045 $261 $810 78 $1,230 $308 $953 84 $1,300 $325 $1,008 90 $1,360 $340 $1,054 96 $1,430 $358 $1,108 102 $1,520 $380 $1,178 108 $1,650 $413 $1,279 114 $1,800 $450 $1,395 120 $2,200 $550 $1,705 10
GIS Analysis Cost Scenarios Example Summary of of Maintained Stormwater System Pipe Repair/Replacement / Replacement Costs High Priority Condition CMP Pipe Greater Than 20 Years Old Not in High Priority Diameter (inches)* Total Length (miles) Estimated Cost Diameter Total Length Estimated Cost (inches)* (miles) Cost per ft Total Cost Cost per ft Total Cost 0 11.3 $155 $9,226,000 18 0 28.0 42.9 $263 $200 $ 38,881,920$ 45,305,000 18 195.4 $325 $335,306,400 24 24 11.4 124.4 $282 $350 $ 16,974,144 $229,891,200 Description Estimated Pipe Length 30 30 4.8 66.9 $318 (mi) Estimated Cost $395 $ 8,059,392$139,526,640 36 High 36 Priority 51.5 4.9 $358 66.1 $450 $ 9,262,176 $90,854,858 $122,364,000 42 21.3 $630 $ 70,907,000 42 48 1.5 21.0 $488 $660 $3,891,000 $ 73,189,000 48 54 2.5 7.4 $512 $815 $6,732,000 $ 31,649,000 60 6.0 $ 1,030 $ 32,901,000 54 66 0.4 1.6 $632 $ 1,040 $1,430,000 $8,687,000 60 72 0.6 2.9 $798 $ 1,045 $2,572,000 $ 15,994,000 78 0.8 $ 1,230 $4,992,000 66 0.1 $806 $400,000 84 0.4 $ 1,300 $2,964,000 72 90 0.3 0.1 $810 $ 1,360 $1,466,000 $913,000 78 96 0.0 0.1 $953 $ 1,430 $229,000 $1,123,000 102 0.1 $ 1,520 $448,000 84 0.1 $ 1,008 $461,000 108 0.1 $ 1,650 $1,090,000 96 114 0.1 0.0 $ 1,108 $ 1,800 $487,000 $330,000 Totals 120 66.1 0.4 - $ 2,200 $90,854,858$4,377,000 Totals 543.4 $ 1,121,957,240 Example Summary of Total Estimated Contracted Stormwater Pipe Repair / Replacement Costs CMP : 10-20 years, not High Priority 210.9 $434,966,840 CMP: > 20 years old, not High Priority 543.4 $ 1,121,957,240 11
GIS Analysis Cost Scenarios Example Estimated Annual Stormwater Conveyance Repair/Replacement Annual Costs - 100% Contracted Year Pipe Repair/Replacement Cost Open Channel Cost All Other Costs (BMP and Stream restoration) Total Estimated Annual Cost 2011 $31,524,631 $355,500 $19,099,001 $50,979,132 2012 $31,524,631 $355,500 $20,784,319 $52,664,450 2013 $31,524,631 $355,500 $21,074,547 $52,954,678 2014-2020 $31,524,631 $355,500 $21,364,775 $53,244,906 Year Example Estimated Annual Stormwater Conveyance Repair/Replacement Annual Costs - 100% County Pipe Repair/Replacement Cost Open Channel Cost All Other Costs (BMP and Stream restoration) Total Estimated Annual Cost 2011 $20,491,010 $355,500 $19,099,001 $39,945,511 2012 $20,491,010 $355,500 $20,784,319 $41,630,829 2013 $20,491,010 $355,500 $21,074,547 $41,921,057 2014-2020 $20,491,010 $355,500 $21,364,775 $42,211,285 Brown and Caldwell 2011 SESWA Conference 05oct11 12
GIS Analysis Other costs Open Conveyances /Stream restoration/bmps within LOS Include in the inventory assess size of channel and type of maintenance required Integrate into the maintenance program erosion repairs, tree removal, mowing, clearing, minor regrading, revegetation Ditches, swales, surface channels $3,500-9,500/mile for routine maintenance and severe erosion issues as much as $100,000/mile Identify opportunities through watershed program, inventory activities, citizen complaints Projects range from stream stabilization, severe erosion control, and stream restoration Stream Restoration $50-$500/linear foot depending on project scope, stream size, and materials used Identify opportunities through watershed program, inventory activities, citizen complaints Integrate into the maintenance program erosion repairs, tree removal, mowing, clearing, revegetation, trash and debris, structural problems, and possible water quality issues Projects range from retrofits to meet current conditions or maximize downstream benefits or install new BMP BMPs $10,000-$1,000,000 depending on BMP size and project scope Brown and Caldwell 2011 SESWA Conference 05oct11 13
Asset Management/Risk Approach Probability of failure/consequence of failure Cost Compare to cost of proper maintenance/repair & replacement Primary factors Location Environmental impacts Health and safety Property damage Public disruption Brown and Caldwell 2011 SESWA Conference 05oct11 14
Economic Life Model Probability of failure Cost of failure Optimal intervention timing calculation Brown and Caldwell 2011 SESWA Conference 05oct11 15
Other Considerations What if you have very little or no data? Level of inventory detail Rate of inventory Structures vs. pipes Condition assessment Assumptions of condition Maintenance program Frequency can affect service life In-house vs. contractor Brown and Caldwell 2011 SESWA Conference 05oct11 16