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Culvert Replacement Cost Benefits in the Long Term
Ben Naumann1 Lynn Knight2 1 NRCS Fisheries Biologist, Bangor ME 2 NRCS Economist, Greensboro NC Technical Center
Stream-‐Smart Crossings…
Maintain fish and wildlife habitat
while protecting roads and public safety.
Stream-‐Smart crossing
Pro’s • Environmental
• Healthier popula7ons of fish • Decreased erosion of stream banks
• Improved water quality • Public safety • Economic
• Recrea7on • Jobs
• Climate change • Long term cost benefits?
Con’s • Cost • Cost • Cost • Cost • Invasive species
Long Term Cost Benefits?
Exis,ng analysis on structure comparison costs Forestry roads • Long compared arch culverts Municipal roads • “An Economic Analysis of Improved Road-‐Stream Crossings” TNC
Arch culvert Round culvertCase 1 10' x 4'5" arch replaces two 2.5' round culverts 1,357$ 1,706$ Case 2 12' x 5' arch replaces 3.5' round culvert 1,545$ 1,887$ Case 3 12' x 5' arch replaces 3' round culvert 2,265$ 1,461$ Case 4 12' x 5' arch replaces 4' round culvert 2,452$ 2,000$
Scenario Description Average annual cost over 50 year time-‐frame
Table 5. Eastern Maine Culvert Cost Estimates (2007 dollars)
Estimated Average Annual Cost for Lewis Brook Culvert (2012 Dollars) Annual cost over 15 years
Annual cost over 35years
Annual cost over 70 years
Double Metal Pipe Culvert 6,551$ 4,446$ 2,726$ Concrete Box Culvert 13,533$ 5,800$ 2,900$
Long Term Cost Benefits?
Addi,onal analysis need: • Compare costs over 7me for difference structure types for forestry crossings over 50 years
• More cost examples from Maine specifically for municipali7es
• Two case studies • Forestry • Municipali7es
Arch culvert Round culvertCase 1 10' x 4'5" arch replaces two 2.5' round culverts 1,357$ 1,706$ Case 2 12' x 5' arch replaces 3.5' round culvert 1,545$ 1,887$ Case 3 12' x 5' arch replaces 3' round culvert 2,265$ 1,461$ Case 4 12' x 5' arch replaces 4' round culvert 2,452$ 2,000$
Scenario Description Average annual cost over 50 year time-‐frame
Table 5. Eastern Maine Culvert Cost Estimates (2007 dollars)
Estimated Average Annual Cost for Lewis Brook Culvert (2012 Dollars) Annual cost over 15 years
Annual cost over 35years
Annual cost over 70 years
Double Metal Pipe Culvert 6,551$ 4,446$ 2,726$ Concrete Box Culvert 13,533$ 5,800$ 2,900$
Forestry Case Study
Four Structure types compared: Waste block bridge: Inside span 14’ actual cost $10,200
Maintenance schedule: Running boards every 10 yrs, 8x8 every 20 yrs Arch culvert: 10x6.3x40 es7mated cost $35,400
Maintenance schedule: None CMP Culvert 4’: Es7mated cost 4,000 note, doesn’t meet current BMP’s
Maintenance schedule: Annual $600, Culvert replacement every 20 yrs 2 PVC Culverts 4’: Es7mated cost $9,600 Meets current BMP’s for 25 yr storm
Maintenance schedule: Annual 600, Culverts not replaced
Forestry Case Study
Present Value Analysis bringing all future payments to the present (today) answers the ques7on: “How do I objec7vely compare alterna7ves with differing up-‐front installa7on costs, and future O&M costs?” Infla7on rate of 2.8 percent
Average Annual answers the ques7on: “If I had to borrow money up front to install and maintain the various alterna7ves, how much would I need to borrow, and what would the annual loan payments be?”
Forestry Case Study
Table 1. Total Prac7ce Cost Analysis:
Altera,ve Structure Net Present Value Average
Annual Cost
1 Arch Culvert $35,400 $1,324
2 2 Plas7c Culverts $25,642 $959
3 Round Culvert $23,670 $885
4 Bridge $13,640 $510
Forestry Case Study
Table 1. Total Prac7ce Cost Analysis:
Altera,ve Structure Net Present Value Average
Annual Cost
1 Arch Culvert $35,400 $1,324
2 2 Plas7c Culverts $25,642 $959
3 Round Culvert $23,670 $885
4 Bridge $13,640 $510 5 Bridge $11,426 $427
Municipal Case Study
Structure types compared: CMP Culvert: 6’ with a 2 foot over flow
Actual maintenance schedule: 500 every other year, $10,000 large repair at 20 yrs, culvert replaced 28 yrs Concrete Box Culvert: Actual cost $164,000
Maintenance schedule: None, 75 yrs lifespan
Municipal Case Study
Table 1. Total Prac7ce Cost Analysis:
Alterna,ve Structure Net
Present Value
Average Annual Cost
1 6’ culvert $135,274 $4,317
2 Concrete Culvert $164,000 $5,234
Conclusion
Forestry case study: bridges were the most cost savings over7me regardless of maintenance Municipal case study: Short term concrete box is much more expensive, annual costs between the two structure type become less as lifespan increases Future analysis could include: catastrophic failures, climate change, and human safety. Addi7onal project comparisons are needed from the state Request for an on-‐line municipality data repository for keeping track of maintenance, replacement dates and costs