Cost of Upgrading Stream Crossings - Science & … S2 | Cost of Upgrading Stream Crossings | JOE...

ABSTRACTThis paper discusses various alternatives that exist to upgrade culverts so that

they will provide acceptable fish passage as well as the costs associated with imple-menting these alternatives. Most of the streams involved are perennial fish-bearingstreams, although some intermittent streams do have fish spawning in the springwhen flows are adequate.

INTRODUCTIONOver the past several years the Idaho Department of Lands has been conduct-

ing surveys and research to evaluate what impacts are influencing fisheries inIdaho. One of the major impacts we are finding are man made fish barriers thatprevent fish from accessing excellent habitat or restrict fish populations upstreamof these crossings from having a migratory life cycle. In an effort to reduce theimpacts from these barriers, the Idaho Department of Lands as well as other organ-izations is putting a lot of effort into identifying barriers and determining how toupgrade them. I have been involved extensively in training individuals on how toidentify what a barrier actually is and what it takes to provide acceptable fishpassage.

I understand these experiences do not exactly make me an expert in dealingwith cost issues; however, it’s important to realize the Idaho Department of Landsmust manage its land first to provide for a secure maximum long term financialreturn for its beneficiaries. Consequently, cost is always a consideration whendesigning stream crossings and is something I must always be aware of.

Figure 1 shows a culvert that is a fish barrier. Probably close to 99% of streamcrossings that I deal with that impede fish passage are problematic culverts.Consequently, when dealing with upgrading stream crossings, we are reallyaddressing the issue of upgrading culverts so they provide fish passage.

Road maintenance, road decommissioning, and streamcrossing upgrades

Cost of Upgrading Stream Crossings

JOE DUPONTIdaho Department of Lands3780 Industrial Ave SCoeur d’Alene, ID [email protected]

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Figure 1. Fish can’t get through here?

Before I discuss how to evaluate the costof upgrading culverts we must first knowwhy a culvert is a barrier in the first place.Different fish passage problems can besolved with different fixes, some of which aremuch more expensive than others.

There are three main reasons whyculverts cause fish passage problems. First,the drop from the outlet is too high. Second,the water velocity through the culvertexceeds a fish’s swimming ability, especiallyin the springtime when rainbow or cutthroattrout are migrating through. Finally, thewater depth inside the culvert is too shallow.This is a big issue, especially now that wemust size our culverts so that they can pass50 to 100-year peak flows. When we makethat allowance, almost inevitably the waterbecomes too shallow during low-flow periods.State rules govern what is acceptable for eachof these issues. There are numerous alterna-tives to fixing these passage problems andnot too surprisingly depending on whichalternative we choose, the cost will varyconsiderably.

When determining which alternative touse to upgrade a crossing so it provides fishpassage the first three things I consider are:

1. What alternatives will provide accept-able fish passage?

2. Which alternatives will meet the trafficneeds for the site? For example we wouldn’twant to put a ford at a site where we needyear round access.

3. What alternatives will have a lowchance of failure over the long run? Forexample if we place materials into the culvertwe want to insure the crossing will still allowpeak flow events to pass through it.

Once you have a list of alternatives thatwill provide acceptable fish passage, providethe necessary traffic requirements and havea low risk of failure, it’s time to consider thecost of upgrading the culvert. When evaluat-ing the cost of upgrading a culvert I considerthe following:

• Cost of materials, including delivery to site

• Cost of installation• Longevity of structure• Maintenance of structure

CULVERT UPGRADESUsing those four cost criteria (materials,

installation, longevity and maintenance), Iwill now walk through several alternativesthat we regularly consider in Idaho. A costcomparison will tell us which might have thebest cost benefit. Note: In these examples,I’m not going to consider the cost of totallyremoving a crossing and putting in a newone because it is much cheaper to upgrade aculvert in place, wherever practical.

Examples

Angle Iron Fish Ladder Installing an angle iron fish ladder is one

alternative for increasing water depth andslowing water velocity in a culvert. Figure 2shows such a ladder. When properlyinstalled, the fish ladder will create a step

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pool sequence throughout the length of theculvert allowing fish places to rest as theymigrate through. This particular culvertoccurs at about a 5% grade and is about 50feet long. With that fish ladder in place, evenjuvenile fish will have no problem gettingthrough.

When we’re determining the cost of one ofthese ladders, we first ascertain materialscost, including delivery to the site. Theladders aren’t expensive: $15 a foot for oneabout four feet wide; for a 50-ft. culvert,that’s $750. We usually build these in 15- to25-ft. lengths, so they can be transported ona flatbed, which runs up to $35 an hour fordelivery. Of course, in Idaho this may becheaper than in other states.

Figure 2. Angle iron fish ladder

In our area, rock typically runs $3 percubic yard for rock that’s a foot in diameter.For each fish ladder, it usually takes a cubicyard of rock per cross member. For a 50-ft.culvert with 10 cross members the total cost

for rock will be $30. Loading the rock intothe transport truck runs $0.50 a yard, whichseems cheap; if we’re hauling a lot of rock,the costs can quickly add up. Getting therock to the site is often the most expensivepart. In the example in Table 1, delivery ofthe rock costs $0.60 per cubic yard per mile(a round trip of 30 miles thus costs about$180). If we’re in an area where it’s hard tofind good rock, that travel distance candouble or even triple.

Once everything is at the site, the costshifts to installation of the fish ladder.Fortunately, installing an iron fish laddercan be done with manual labor in about twohours with experienced supervision. Ourgoing rate for manual labor is $25 per hour.Once the ladder is placed inside the culvert,rock must be placed behind each crossmember. This is definitely the hardest part ofthe installation, and for a culvert with a 4-ftdiameter, this takes about 4 hours. Once therock is in place the top end of the laddermust be chained to a dead man of some sort— either a big piece of rip rap, angle iron orrailroad iron. The whole project totals$1,185, which is relatively cheap. Table 1reflects costs of the actual project for theculvert shown in Figure 2.

Total 1,185

Labor for installing the fish ladder:Installing fish ladder – 2/hrs ($25/hr) 50Placing rock – 4/hrs ($25/hr) 100

Materials including delivery to site:Fish Ladder 50 ft. long ($15/ft) 750Delivery on Flat Bed truck ($35/hr) 70Rock for fish ladder ($3/yd3) 30(1/ yd3 per cross member)Loading rock ($0.50/ yd3) 5Delivery of rock – 30 miles 180($0.60/ yd3/mile)

Item Cost ($)

Table 1. Angle iron fish ladder average costs

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Chimney Block Fish Ladder Another alternative is a second type of

fish ladder called a chimney block ladder,which operates under the same principle asthe angle iron ladder. Here, the cost ofmaterial, the chimney block, is the mostexpensive part. We try to keep the laddersspread 5 feet apart, depending upon thegrade of the culvert. In the example inTable 2, the 50-ft.-long culvert received 2blocks every 5 feet for a total of $100. Themain cable that runs the length of thisculvert (60 ft.) costs $0.50 a foot for a totalof $30. Tether cables that attach the maincables and hold the chimney blocks in placecost $50 for 100 feet plus cable clamps,washers, and a hook to hold everything inplace at another $20. One pickup truck candeliver all the materials to the site in around trip of two hours for a total of $50.

Again, this is fairly inexpensive for materi-als and only manual labor is needed for itsinstallation. From experience, it takes aboutfive hours to put in place, adding $125 forlabor for a grand total of $375, or one-thirdthe cost of the angle iron fish ladder. In the

right situation, a chimney block ladder canbe very cost-effective.

Welding Baffles into CulvertsBaffles are another solution for

increasing depth and slowing water velocityin a culvert (Figure 4). This alternative ismore expensive than the last two as shownin Table 3. Baffles can be welded into aculvert on site for about $225 a baffle – thisincludes cost of materials. A 50-ft. culvertwith baffles 5 ft. apart would require 10baffles or $2,250. But it’s more complicatedthan that. To facilitate the welding, theculvert must be dry so a pump and hose arerequired (rented), the stream is dammed


Total 375

Labor for installing the fish ladder:Labor – 5 hrs. 125($25 p/hr)

Materials including delivery to site:Chimney blocks – 2 every 5 ft. 100($5/block)Main cable – 60 ft. long 30($0.50/ft)Tether cables – 100 ft. 50($0.50/ft)Cable clamps, washers, and hook 20Delivery – 2 hr. trip 50($25 p/hr in pickup truck)

Item Cost ($)

Total 2,530

Labor – 8 hrs. 200($25/hr)

Weld in baffles – 10 baffles 2,250($225/baffle)Pump and hose rental – 8 hrs. 80($10/hr)

Item Cost ($)

Table 2. Chimney block fish ladderaverage costs

Table 3. Welding baffles into culvert — average costs

Figure 3. Correctly installedchimney block fish ladder

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upstream of the culvert and the waterpumped around. Typically, 8 hours or a fullday are needed to weld all these in place. At$10 an hour, the pump will cost $80 plus 8hours of labor (to man the pump and makesure the dam functions appropriately) at $25an hour, or another $200. Now the grandtotal is $2,530, twice as much as the angleiron fish ladder and six times the cost of achimney block ladder.

Figure 4. Baffles welded into a culvert

Backing Water into the Culvert(Drop Structure)

An additional technique is backing waterinto the culvert. Basically, we install a grade-control structure or drop structure down-stream from the culvert, which backs waterup into the pipe. Figure 5 shows how thistechnique can greatly slow water velocityand increase depth inside the culvert. Thistechnique can also be used to reduce thedrop from the culvert.

This relatively simple alternative hasonly one required material: rock. A typicalproject needs about 20 cubic yards of rock; at$3 per cubic yard, that equals $60. Theexpense comes in loading and hauling thatmaterial to the site. The example in Table 4shows a round trip of 30 miles at $0.60 permile per cubic yard totaling $360. Thisbecomes expensive if the hauling distance is

100 miles or so. This alternative alsorequires an excavator, which must be trans-ported to the site. On a low-boy in a 2-hourround trip at $100 an hour, it would add$200 to the cost. In our example, the excava-tor took 4 hours to complete the task,although that will vary with the size of theexcavator and local rates. Last, additionallabor costs added $100, for a grand total of$1,180, about the same price as the angleiron ladder.

Figure 5. Backing water into the culvertby use of drop structures

Table 4. Backing water into culvert — average costs

Total 1,180

Labor for installing drop structure:Mobilization – 2 hrs. 200($100/hr)Excavator – 4 hrs. 400($100/hr)Manual labor – 4 hrs. 100($25/hr)

Materials including delivery to site:Rock – 20 yards 60($3/yd3)Loading 60($0.50/yd3)Hauling – 30 miles 360($0.60/yd3)

Item Cost ($)

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A word of caution: Each of these alterna-tives will reduce the capacity of the pipe.Most states require that stream crossingspass a certain peak flow event. Hence, if oneof these alternatives will reduce the ability ofthe culvert to pass these peak flow eventsbelow what is required by law, they’re proba-bly not acceptable alternatives or the cross-ing will need some additional modifications.

Such modifications that will increase theability of a crossing to pass peak flowsinclude: putting in overflow pipes if there isa wide enough flood plane, mitering theentrance of the culvert, and raising the roadfill over the culvert to increase the amount ofhead — the higher the head, the more waterthat can shoot through the culvert. Whenincreasing the head, we must be sure to seri-ously armor the crossing or there can beserious problems. I’ve seen a lot of culvertsthat held year after year in that way, but I’vealso seen some that have blown out.

It should be noted that, in our area, theForest Service will also armor the entirecrossing. They don’t raise the fill, but theyhave it functioning like a vented ford. In aflood, the water flows over the top of thecrossing, but the culvert is armored in such away that it will stay in place. This is veryexpensive and those costs are not brokendown here.

Cost of MaintenanceFor all these crossing upgrades, mainte-

nance is an important issue. At theDepartment of Lands, we maintain ourculverts annually. If there is debris stuck infront or inside the culvert, we remove it; ifbranches or vegetation are starting to growin front, they are also removed. When weplace materials inside the culverts, thatoften increases the maintenance costsbecause debris is more likely to become hungup inside the culvert.

For the most part, maintenance isn’texpensive (Table 5). Most often, the annual

check-up reveals little or no maintenanceneeded, so on average, it takes another 15to 20 minutes of labor per crossing to main-tain the angle iron or chimney block fishladders. At $25 an hour, that’s only $10 ayear per culvert.

With the baffled culverts, maintenancegenerally averages less time because wehave solid structures. However, when we dohave problems, e.g., a piece of wood knocks abaffle out, it costs a lot more to replace it.

Finally, with the drop structure, mainte-nance runs about $40 per year. The rockstructures will shift over time; when thathappens, excavators must go in to do thework. In the life of a culvert, it isn’tunusual to readjust the drop structures twoor three times.

Table 5. Average cost of annual maintenance

Maintaining these structures is lowcompared to the overall cost. But the main-tenance needs to be done or more seriousand more expensive problems will arise. Forthose who can’t or are not willing to main-tain these types of crossings on an annualbasis, these aren’t good alternatives toconsider. Some agencies have so manystructures to maintain that they can’t checkthem all. In my opinion, we shouldn’t installmore stream crossings than we can main-tain on an annual basis as that increasesthe risk of failure.

LongevityThe final thing to consider when looking

at overall price is longevity of the structures(Table 6). Over time culverts become dented


Iron Fish Ladder $10/yrBlock Fish Ladder $10/yrBaffled Culvert $20/yrDrop Structure $40/yr

Item Cost

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and they rust through; from bed-load move-ment, they’ll get abrasion or holes punchedin them. We’re finding these culverts lastfrom 15–60 years, depending on bed-loadmovement, how corrosive the water is, andthe type of traffic. On average a culvert typi-cally lasts about 30 years. When we put inan iron fish ladder, typically it will last theduration of the culvert, about 30 years; withthe block fish ladder, however, the chimneyblocks will chip or crack so its longevity iscloser to 10 years. The baffles should last theentire duration of the culvert as will the dropstructure if installed properly.

Putting It All Together: Culvert Upgrades

Table 7 pulls all the cost considerationstogether for a comparison of the different

alternatives (minus the baffle). I did notinclude baffles because the cost is much moreexpensive than the others. When developingthe overall cost, it is important to considerthe interest lost from the money we put intothis crossing, in this case, 30 years (30 yearsbecause that is the longevity of the mostdurable structures). Here I used simpleinterest, because when the Department ofLands does business, they put money into apermanent endowment fund. The moneyearns interest and that interest is given outto the schools, so it’s not rolled back in andcompounded. With private individuals,compounded interest is more appropriate.Obviously, the more money spent up front,the more interest is lost over time.

In the final analysis, over 30 years theprice of all three alternatives is comparable,with $700 separating the high from the low.In a situation such as this where the overallcosts are similar, I recommend selecting thealternative that is going to last the longestand requires the least maintenance. Forexample, in this case I would suggest puttingin the angle iron ladder. If we anticipatedthat the culvert would have to be replaced in

Cost Item Iron Ladder Block Ladder Drop Structure

Initial cost $1,185 $375 $1,130

Interest lost (for 30 years) $2,133 $675 $2,034

Maintenance $300 $300 $1,200

1st removal/replacement $0 $574 $0

Interest lost (for 20 years) $0 $688 $0

2nd removal/replacement $0 $722 $0

Interest lost (for 10 years) $0 $434 $0

Total $3,618 $3,768 $4,364

Table 7. Putting it all together (initial cost + maintenance + longevity)

Table 6. Longevity of structures

Iron Fish Ladder 30 yearsBlock Fish Ladder 10 yearsBaffled Culvert 30 yearsDrop Structure 30 years

Item Longevity

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ten years than the chimney block culvertwould be the way to go.

CULVERT REPLACEMENTSThere are many culverts where there is

no reasonable way to upgrade them so thatthey will provide acceptable fish passage, orany upgrades will put the crossing at a highrisk of failure. In situations like this, theonly practical way to restore fish passage isto remove the culvert and replace it with afish friendly stream crossing. When replac-ing a culvert I consider a bridge, a bottom-less type culvert, a ford or a properlyinstalled culvert. The cost of each of thesecrossings can vary tremendously dependingon conditions of the site and the design plan.I will go over some of the things to considerwhen determining the cost of these types ofstream crossings.

BridgesBridges tend to be the most expensive

stream crossing; however, they also tend tobe the most fish and environmentallyfriendly crossings. Typical bridge designconstitutes a deck, abutments, footers andwingwalls. The cost of each of these struc-tures fluctuates greatly depending on thetype of material used. Table 8 indicates whatcurrent installed prices for a bridge are,depending on the type of materials to beused. The deck can be made with steel,concrete, or wood. A wood deck runs

$150–300 per foot whereas steel or concreteruns $800 per foot. Decommissioned railroadcars are also available as material; they costabout the same as wood, $150–300 per foot.

Another expensive structure on thesebridge designs is the abutment. They holdthe whole bridge in place and give it stabil-ity. The cost of abutments can vary widely.Wood abutments typically cost about $5000each installed, +/-$1000. Steel or concreterun about $10,000. Abutments are notneeded if we construct a pass through bridge.These bridges span the entire streamchannel and rest on footers. Footers cost lessthan half the price of abutments, but withfooters the cost of the deck will be more asthe deck must be another 10–15 ft in lengthso that it can span the entire streamchannel. Another consideration in bridgedesign is wingwalls, usually used with abut-ments. Wingwalls insure that the abutmentsaren’t undercut by sediment being pipedaway from them. Again, cost depends uponthe type of material used.

Table 9 shows the cost of some of thedifferent bridge designs used in Idaho. Thephoto examples are of bridges on streamsless than 20 feet wide where we typically seeculvert problems. Note: These prices includeinstallation, but they don’t include a designcost. For my agency, the Department’shydrologist, engineering geologist, and fishbiologist do most of the design work; conse-quently the cost of our work is not factored


Table 8. Average costs of bridge design

Material Used Deck Abutments Footers Wingwall

Wood $150–300/ft $5,000 $2,000 $2,500

Steel/concrete $500–800/ft $10,000 $3,000 $5,000

Rock $2,000

Railroad car $150–300/ft

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in. If the design is hired out, that costshould be added in.

Wood Stringer BridgeFigure 6 shows a wood stringer bridge,

which ranges in cost from $10–20,000. Thisbridge is actually on the upper end of thatcost range. It’s a fairly sturdy structuredesigned to pass loaded log trucks, and itcost about $18,000 when completed. Theissue with wood bridges is their lowlongevity (approximately 30–50 years); overtime the wood tends to rot.

Figure 6. Example of a wood stringer bridge

Prefabricated Concrete BridgeFigure 7 shows a prefabricated concrete

bridge. Basically everything is made in theshop; then it is brought to the site anddropped in place. Prefabricated concrete

bridges range from $15–25,000. This one wason the low side at about $17–18,000. Theissue here is limited span: the biggest I’veseen was about 20 ft long. Larger ones areharder to handle and can break duringinstallation. Their longevity is 40–60 years.Cost of annual maintenance is pretty negligi-ble; in fact, it may not be necessary to go inevery year and remove material. However, awood running surface will only last 15–20years and costs $1,500 to replace.

Figure 7. Example of a pre-fabricatedconcrete bridge

Railroad BridgeFigure 8 shows a railroad bridge, where

the rail car was cut in half and laid side byside with gabion abutments under it.Railroad bridges range from $15–30,000 inprice, about the same as a wood bridge.Because railroad bridges have a bit longerlife span, we rarely put wood bridges in any

Bridge Type Total Cost Longevity

Wood stringer $10,000–$20,000 25–50 years

Pre-fabricated concrete $15,000–$25,000 40–60 years

Railroad $15,000–$30,000 40–60 years

Steel or concrete $30,000–$50,000 50–75 years

Table 9. Total costs and longevity of four different bridge types

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more. The pictured railroad bridge cost about$24,000 installed. Different vendors sell therailroad cars and price lists are available.Price and quality can vary widely; i.e., if youbuy an old beat-up flat car, it will only lastabout five years.

Figure 8. Example of a railroad bridge

It should be noted that in some statesrail cars cannot be used on public roads orforest roads because they don’t have designspecifications. There is a supplier thatupgrades them for such use, but these are alot more expensive. They have struts under-neath and have rails on either side. Theydon’t look like actual rail cars any longer. Itis also possible to have rail cars re-engi-neered for use in crossing projects.

Figure 9 shows a steel or concrete bridge.We have chosen this material a lot lately.Whether steel or concrete, prices rangebetween $30–50,000. This isn’t a particularlylarge bridge; it spans 40 feet or less and cost

$45,000 to put in place. The advantage ofthis alternative is that you can put wood orgravel over it or pave it. Gravel makesgrading the road easier; the grader can goright over the bridge and not be sloweddown, although he must be careful not topush the dirt off the side. Longevity is 50–75years, although shifting stream channelsmight shorten that.

Figure 9. Example of a steel bridge

Other Culvert/Passage Types and CostsSome additional options for stream cross-

ings include bottomless arches, buriedculverts, and fords. Table 10 providesaverage costs and expected longevity forthese additional options.

Bottomless ArchBottomless arches are built by digging

down outside the stream channel andputting in footers of corrugated metal orconcrete (Figure 10). Note that concrete is


Culvert/Passage Type Cost/ft Total Cost Longevity

Bottomless arch $400–600/ft $15,000–$25,000 30–60 years

Buried culvert $150–300/ft $8,000–$20,000 20–50 years

Ford $500–$5,000 Varies

Table 10. Cost and longevity comparison for three additional options

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much more expensive than corrugated metal.Then, in either case, corrugated metal sheetsare added on top. In Idaho, the installedprice is $400–600 per foot. The bottomlessarch shown in Figure 10 cost about $23,000.Bottomless arches are often cheaper thanbridges. However, contractors tend to hatethem because they have to be constructed onsite and they can be quite difficult to put in.Fine sediment can be a problem because itcan erode and undercut the footers and causethe structure to fail. The finer the sediment,the deeper the holes need to be for thefooters.

Bottomless arches have a huge range inlongevity, with a life span ranging from 30-60 years. Those with a shorter longevityseem to occur in streams with shifting chan-nels, considerable bed-load movement and/orcorrosive waters.

Figure 10. Example of a bottomless arch

Buried CulvertBurying a culvert can be an excellent

technique to insure it will provide proper fishpassage. Figure 11 shows what the inside ofa buried culvert looks like. Notice all thelarge substrate that occurs in the bottom ofthe culvert. This substrate mimics a naturalstream bottom and will allow even small fishsuch as sculpin to pass through. This tech-nique works on streams with gradients up to

about 5%. Over that grade, it is recom-mended to install angle iron fish ladders tohold all the rock in place. The installed pricefor a buried culvert ranges from $150–300per foot. The culvert shown in Figure 11 was40 ft. long and was installed for $12,000.

Figure 11. Example of a buried culvert

Longevity for these culverts can varywidely (20–50 years), depending on bed loadand the corrosive nature of the water. Irecently heard of several culverts that wereinstalled 15 years ago that now have holes inthem because of the bed-load movingthrough. With a buried culvert, abrasiondoes not occur along the bottom of theculvert as it is protected by rock. The onlyplace abrasion appears is on the sides abovethe rock line, which tends to increase thelifespan of this type of culvert over what wesee with typical culverts.

FordThe last solution presented here

involves fords. While many people denigratethem, I believe they are under-utilized andcan be a great alternative, especially onstreams with large flood plains or whereextensive channel shifting occurs. With aford, we don’t restrict the stream channel,and the only material needed is rock for theapproaches. Where we don’t need year-roundtraffic, a ford can be a great alternative.Constructing a ford costs from $500–5,000,

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although they can cost much more if thestream grade exceeds 3–4%. In this situationI would not recommend a ford. Typically allthat is needed for a ford is to rock theapproaches, usually about 150 feet on eachside of the stream so that vehicles can cleantheir tires off before they get to the creek.

Culvert Replacements — Comparison of Options

In a recent real-life example, IdahoDepartment of Lands compared the cost ofinstalling a steel bridge, a bottomless arch,and a buried culvert. The stream had a V-channel and a lot of bed-load movement. Inthis situation, the steel bridge had anexpected longevity of 75 years, but thebottomless arch had a life span half thatbecause of amount of bed-load. The buriedculvert we estimated at 25 years, a third ofthe steel bridge.

Initial costs were estimated at $45,000for the bridge, $20,000 for the arch, and$12,000 for the buried culvert. The interestlost period was the full 75 years, thelongevity of the most durable structure (thesteel bridge). Again, the more money spentup front, the more money we lose in interestover that time. This particular steel bridgehad a gravel surface, so the maintenancewas very low as described above. Thebottomless arch, if built correctly, also haslow maintenance since material rarely jamsaround it. Buried culverts, on the otherhand, have a higher maintenance cost,


Cost Item Steel Bridge Bottomless Arch Buried Culvert

Initial cost $45,000 $20,000 $12,000

Interest lost (for 75 years) $202,500 $90,000 $54,000

Maintenance $375 $600 $1,875

1st removal/replacement $0 $55,200 $28,125

Interest lost $0 $115,920 $84,375

2nd removal/replacement $0 $0 $41,250

Interest lost $0 $0 $61,875

Total $247,875 $281,720 $269,125

Table 11. Comparison of options (initial cost + maintenance + longevity)

Figure 12. Example of a stream ford

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because they do tend to jam with debrismore often.

Table 11 shows the rundown of the coststhat would be associated with these differentalternatives. Over 75 years, the bridge is thecheapest alternative. It also requires theleast maintenance, is the most environmen-tal friendly, and has the best longevity.

Note: In many cases, longevity will beconsiderably higher for buried culverts andbottomless arches, reducing the total by asmuch as $60–80,000. In that case, the deci-sion is more difficult and we must balanceenvironmental friendliness with cost. A lotof it depends on your policies and prefer-ences. However, if the costs are close intotal, I will always lean towards environ-mental friendliness.

LANDSCAPE APPROACHI will close with a discussion on evaluat-

ing the costs of upgrading culverts in alarger area, such as a watershed orEvolutionarily Significant Unit (ESU).

The first step in determining the cost ofupgrading culverts in a large area is discov-ering how many stream crossings there are.A typical topographic map shows where theroads cross the creeks, but these maps areseldom accurate. The maps seldom show allthe roads that exist, so an on-site survey ofthe watershed is preferred. We did a surveyrecently in a watershed where maps showed13 road crossings. We located four additionalcrossings in this case that were not depictedon the maps.

The next step is to determine whichculverts have problems and what are thoseproblems. When in the field, we determinewhat type of crossings there are, what thestream gradients are (for culverts), thelength and size of the culvert, the type ofcorrugation, the drop into the inlet and outof the outlet, and the depth of the holdingpool (Table 12). With this information, weusually can tell which crossings are fish

barriers and why. In the watershed surveymentioned above, we found that 12 of the 17crossings were actual fish-passage problems;i.e., they violated the fish passage rules ofour Stream Channel Protection Act.

Once the crossings that are barriers areidentified, it’s important to consider the sizeof the watershed upstream, how wide theflood plain is, the grade of the stream, andthe other issues identified in Table 12 beforewe can determine what alternative will workbest and be most cost effective. With thisinformation, we can relatively quickly (prob-ably within a day) and easily determine thecost of upgrading the culverts throughout thedesignated area.

Table 12. What to consider and knowwhen evaluating a stream crossing for

fish passage problems

However, if we look at a larger area, likea designated ESU, the process becomes moredifficult and complex. This is way outside myarea of expertise, but after thinking about itfor a while here is my thought. First, I wouldbreak the ESU into land ownership (U.S.Forest Service, Bureau of LandManagement, State, private, and Tribal), andfrom each of these owners, I would pick 5 to10 10–20,000 acre watersheds, and gothrough the process described above, includ-ing the on-site reconnaissance. Once 5–10watersheds had been evaluated, we couldexpand by ownership for the entire state. Itmay be necessary to also categorize by state,since different states do business differently.

• Type of crossing• Gradient• Length and size of culvert• Corrugation• Drop into inlet• Drop from outlet• Depth of holding pool

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If you do enough sub-samples you could actu-ally develop confidence intervals around yourcost estimates.

A lot of money and effort is currentlybeing put into upgrading stream crossingsand I’d just like to reinforce that improving astream crossing is one of the best ways to

increase the range and available habitat forfish. There are significant problems withstream crossings and these upgrades are agood way to use our money efficiently andeffectively. Our hope too is that over time,these fixes will help salmon populationsrebound.


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