ATT D - Constructability Review Summary of Discussions.pdf

Constructability Review Summary of Discussions Project: ODOT | M22022 US101 MP 303.06 Culvert

Subject: Summary of Discussions from 1:1 Sessions with Contractors

1:1 constructability focused sessions were conducted April 1st and April 3rd, 2025 with 2 different Contractors and select members of the design team. As an outcome of these constructability focused sessions, ODOT conducted a site visit with the same 2 contractors on April 17th. The following is a summary of the discussions from these sessions, including the site visit.

Disclaimer: The Summary of Discussions is a preliminary Project Document subject to the disclaimer included in the industry outreach flyer titled “Constructability Review and One-On- One Meetings project area includes the M22022 US101 MP 303.06 Culvert. Anticipated Construction Cost is $1M-$2M”. See appendix A for full disclaimer language. All questions below relate only to the proposed preliminary design, and do not reflect any final design decisions or other final project decisions.

Trenchless Installation

1. ODOT question to Contractors: What would your proposed means and methods be for trenchless installation of this culvert? What method/tooling seems most suitable given the anticipated subsurface conditions and site geometry?

Summary of Contractor Responses:

Both contractors stated that after considering several options, their assessment was that a traditional jack and bore method would be the most suitable approach. This method would be expected to be effective in handling most, if not all, of the rock that might be encountered during the alignment. They emphasized that jack and bore doesn’t rely on drilling fluids, thereby eliminating the risk of frack-outs into the ocean, a critical concern given the site’s proximity to the coast. Additionally, jack and bore exerts limited vibration, making it more compatible with the area’s sensitive landslide-prone conditions.

One contractor specified that their preferred jack and bore installation method was to use an OTS steering shield ( short for "on-target steering equipped) with a carbide cutter head and wing cutters to achieve full-face cutting. They believed this method would be valuable for the installation, especially for its capability to handle harder material and its accessibility if any foreign objects, such as wood or boulders, needed to be removed manually. The contractor confirmed that it was a standard jack and bore system, essentially using a steering stabilizer

May 9, 2025 2 with wing controls that allowed both vertical and horizontal alignment adjustments. The contractor further elaborated that the system included a regular auger boring setup from a pit, where they would jack in 20-foot sections of casing pipe behind the shield. When asked about the potential use of a directional drilling system, the contractor expressed reservations. They noted that directional drilling posed more risks due to the lack of guaranteed casing during the crossing, which could lead to settlement issues.

Both contractors went on to explain that other methods were considered but found unsuitable. Pipe ramming was ruled out because the hammer size required to drive casing through the subsurface materials would generate significant vibration, which poses a risk to slope stability. Directional drilling was also dismissed as an option. They noted that directional drilling produces substantial fluid loss on the downstream side and carries an unacceptable risk of hydraulic fracture or bentonite surfacing near the ocean. They noted that directional drilling relied on bentonite slurry to keep the hole open and supported. They emphasized that given the steep grade of the site, the slurry material might not hold, depending on the direction of drilling.

They noted the high risk of slurry spillage and environmental hazards, especially since the hillside was considered a potential slide area. Even without environmental concerns, they questioned the effectiveness of directional drilling on such a steep slope. Microtunneling was similarly considered unsuitable, due to anticipated obstructions, complexity, and cost.

The contractor then transitioned to discuss project timeline and sequencing constraints, especially with respect to the in-water work window. The contractor stressed that a primary goal is to complete as much work as possible outside of the July 15–October 31 fish window, to minimize risk and scheduling pressure. Without seeing the site firsthand, they acknowledged that the plan set and photos were helpful “sort of,” but boots-on-the-ground assessment is necessary to fully understand site constraints. Nonetheless, their preferred plan would be to build the jacking pit on the downstream side, which he acknowledged may be challenging due to what appears to be a steep side slope. The pictures did not show the actual proposed outfall location, making it hard to judge available space. However, the existing road over the culvert could provide access and schedule benefits.

They explained further that boring uphill is generally preferred, especially in difficult ground conditions, because groundwater drains out of the casing back into the shaft, reducing the risk of water accumulation during hand tunneling through boulders. If the crew is forced to bore downhill, any encountered boulders may require hand excavation while working in standing water, which presents a safety and productivity concern. Another contractor responded similarly, stating that in all jack and bore operations, especially where groundwater was involved, it was always best to bore from the low end going uphill. This approach allowed water to drain out naturally if they encountered obstacles like boulders or logs and had to manually tunnel them out, avoiding any accumulation or pressure buildup in the pit. The contractor added that pushing from the low end also reduced slide hazards. Pushing downhill could increase skin friction on existing fill material and potentially destabilize the slope, making boring uphill the safer and more practical option.

May 9, 2025 3

In terms of space, the contractor stated that the smallest jacking pit they could work with would be 14 feet wide by 28 feet long, though 14 by 40 feet would be ideal, allowing them to jack 20-foot segments instead of 10-footers. Another contractor, when asked about jack/bore pit dimensions required for a 42-inch jack and bore from the low end, explained that their standard bore pit size was 40 feet long and 15 feet wide. However, if space was constrained, those dimensions could be reduced. For the receiver pit, depending on the tooling, they would likely need a 10 by 15-foot shaft. Due to site topography, the team noted that the outlet was constrained. They inquired about the minimum workable size for a bore pit. The contractor explained that while they typically used 20-foot pipe sections, they could reduce them to 10 feet to save space, though this would increase costs due to additional welds. A 25-foot-long by 10-foot-wide pit could potentially work, and they suggested following up during a site visit to confirm what was feasible. In general, multiple contractors expressed the ability to use 10 ft segments, albeit at further cost in comparison to 20 ft segments.

The contractors noted that the West Access Road, visible in site photos, appears to be a dirt road that will likely become muddy under construction traffic. They suggested that fabric and rock stabilization would be necessary to support heavy equipment like a 40- to 50-ton excavator. When asked whether this should be a lump sum or quantified pay item, the contractor responded that while either method would work, having a quantified item for fabric and rock would be preferable for estimating accuracy. They explained that, depending on actual site conditions, they may need anywhere from 8 to 16 inches of rock, potentially including a base layer of large rock topped with smaller aggregate to withstand frequent hauling of casing, machinery, and spoil material. The contractors emphasized that this road would experience high traffic volume, not just a few dump truck loads, so it must be designed as a durable gravel haul road.

They also explained that the jack and bore pad must be constructed to follow the pipe slope, which he estimated was around 3%. The bottom of the pit would need to be about 18 inches below the bottom of pipe, and they’d typically lay down 6 to 12 inches of gravel base, meaning the total depth from ground to pipe bottom would be roughly 2.5 feet.

When discussing push resistance and anchoring, the contractor said that ideally, they would push against native soil, if a good back slope exists. If not, they would install steel beams or concrete anchor blocks or even use an excavator as a backstop. They gave several examples of past projects where they had used different anchoring systems, depending on topography and soil conditions. They added that micro-piling is possible, but it would be expensive and would require a subcontractor. Their preference would be to work with what’s already onsite, using basic construction equipment, welders, and concrete. Another contractor expressed a similar desire for more pragmatic methods: when asked how they would anchor the jacking system, the contractor explained that from the centerline of the casing, they usually left 37 inches to a gravel pad set at the slope of the crossing. Depending on depth, they might slope the pit out or install shoring. In the back, they would typically use steel sheets and a thick 2-inch plate for backing. In steeper areas like this one, they could pour a concrete slab to serve as a push-off anchor if needed. Ultimately, they concluded that these specifics would depend on final site conditions and that a site visit would help determine the best course of action.

May 9, 2025 4

The contractor emphasized that working from the downstream side would reduce the number of hours needed inside the in-water work window, which is extremely beneficial. They noted that schedule risks increase significantly if the downstream jacking pit cannot be constructed, meaning they’d have to bore from the upstream side. That would involve extended work hours, potentially round-the-clock shifts, which are costly and difficult on remote sites like this.

They then described the time commitment involved even under ideal conditions. For example, constructing the jacking pad, pit, and backstop would take a minimum of two weeks, possibly more. Boring itself, under perfect conditions, might progress at a rate of 30 feet per day (for 20-foot casing segments), equating to about 10–12 working days just for the bore, not including setup or teardown. And that would assume no boulders or obstructions, when each large boulder could delay progress by over a week and a half.

After the bore is complete, crews still need time for tie-ins, drill placement, concrete inlet work before water flows, water diversion, and restoration, all of which add additional weeks.

They concluded that in ideal conditions, the job could be done in a single in-water work window, but any significant obstructions or scheduling issues would push it into a much longer duration.

If forced to bore from the upstream side, he projected a 30% to 40% increase in cost and schedule due to overtime, complexity, and risk.

The contractor reiterated that the downstream jacking pit option is the preferred and most efficient path forward, but its feasibility hinges on topographic conditions that need to be evaluated on-site. They recommended that ODOT consider a site walk within the next couple months and emphasized the importance of flagging key inlet and outlet locations and having tentative elevations marked before that visit.

The team asked about another contractor about the cost implications of boring from the inlet (top) rather than the preferred outlet (bottom). The contractor clarified that the issue was more about constructability than cost. In line with other contractors, they expressed a preference that boring uphill was safer and more manageable. While the cost difference wasn’t expected to be drastic, they estimated that boring downhill could potentially increase the overall cost by about $200,000 due to increased difficulty in controlling grade and removing obstacles.

The contractor then asked what the biggest factor would be that might prevent placing the bore pit at the low end. The team responded that the main issue would be the site topography. While the upslope end already had a relatively wide area for setup without needing to cut into adjacent hillslopes, the downstream end might require temporary shoring and more work to establish a 15 by 40-foot working pad. They emphasized that this didn’t make the low-end option impossible, just more complicated.

The team noted that an on-site visit would clarify these conditions, particularly since the slopes were rated 2:1 and difficult to fully assess from maps or drawings. While the upslope bench might appear more accessible, the feasibility and constructability benefits of boring from the low end likely outweighed the convenience of the upper area.

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During the discussion, ODOT used to photos to identify the location of the new pipe as upslope, in the wooded area behind the skid steer shown in the photo. The existing outlet was just below a group of trees near the access road, on the downslope side.

When asked if they could lower the outlet to match the elevation of the access road, the team noted that doing so would conflict with one of the project’s environmental constraints, which required the new pipe to align with the existing outlet location to maintain proper channel alignment. Lowering it would increase the outlet angle, which could introduce complications.

One of the team members asked whether a more realistic construction schedule would involve two in-water work periods, rather than compressing all trenchless work into one season.

the contractor responded that while it could be spread over two seasons, he believed the work could be completed within a single in-water window. However, doing so would likely require intensive scheduling, including working two 10-hour shifts, five to six days per week, particularly during critical phases. The contractor expressed concern about attempting to phase the work across two years, calling it “unwise.” Once the ground is disturbed for the first season, he explained, it becomes very difficult to stabilize the site for winter and then rebuild access and restart operations the following year.

The contractor described a typical approach if construction had to occur from the uphill/inlet side, where they would install a temporary drainage pipe (e.g., 30–36 inches in diameter) across the existing creek channel. This pipe would be sandbagged and backfilled with rock to form a temporary road crossing, allowing excavators and trucks to access the area. This method, though standard, still qualifies as in-water work, and the contractor did not believe constructing a temporary bridge would be practical at this site due to terrain constraints and feasibility.

A member of the design team then followed up with a technical question about the jack and bore method, asking whether the equipment needed to be anchored to resist thrust forces.

The contractor confirmed that it did, explaining that the ideal condition is to push against existing, undisturbed earth, such as a natural back slope. If that isn’t available, alternatives include installing steel beams into the ground and encasing them in concrete, using gravel and earth berms, or even pushing against a large excavator. The appropriate anchoring system depends entirely on the site’s topography and soil composition.

The contractor went on to describe the construction of the bore pit, stating that the bottom of the pit would sit about 18 inches below the bottom of the pipe, and they would typically place 6 to 12 inches of gravel as a base for the boring machine. In total, crews would need to budget about 2.5 feet below the pipe invert for the pit. The pad follows the pipe slope, which in this case he estimated to be approximately 3%, a relatively shallow incline that is easy to accommodate in the bore pit layout.

The contractor then addressed a potential challenge: if the bore begins at the downstream (outlet) side, there may not be enough native material to push against due to the slope descending toward the ocean. When asked if he had alternatives for anchoring in such a case, The contractor described a method involving dead-man anchors (steel beams embedded 6–8

May 9, 2025 6 feet deep into dense soil or mélange), then filled with concrete and welded back to the boring machine, effectively allowing the machine to “pull while it pushes.” Though more elaborate solutions like micro-piles could be considered, the contractor said those are costly and would require subcontracting; his strong preference was to use basic materials already on-site:

excavators, welders, steel, and concrete.

When asked if they had specific design recommendations to facilitate jack and bore from the downstream side, the contractor reiterated that a site visit would be necessary before making firm suggestions. The contractor emphasized that many of his comments were contingent on what conditions exist on the ground but restated his main recommendations: pursue construction of a bore pad on the downstream side, and ensure access road extensions are sufficient to support equipment movement to that location.

In closing, the contractor was asked what kind of cost or schedule increase ODOT might expect if downstream boring is not viable and the team is forced to work from the upstream side.

The contractor estimated a 30–40% increase in both cost and duration, attributing this to overtime, complexity, and risk factors involved in staying within a single fish window under less favorable conditions. The contractor explained that contractors develop their crew schedules based on agency-imposed timelines (e.g., finishing by October 31), and if the site requires longer hours or expedited material procurement, especially for Buy America-compliant steel casing, those costs scale up quickly. Nonetheless, he commended ODOT for typically being clear and specific about domestic material requirements, which helps with estimating.

Lastly, the team asked if the outlet-side pad could be countersunk into the slope to minimize the fill needed. The contractor confirmed that this was possible, provided it received geotechnical and structural approval. The contractor noted that this approach would depend on slope conditions and how ODOT planned to handle restoration of the disturbed area. At this point, ODOT referenced geotechnical drilling data that indicated the West Access Road extends farther than shown in the plans. The contractor remarked that from what he could see, there appeared to be enough usable slope to dig into and construct the pad, possibly with shoring, followed by backfill and slope stabilization as needed

1. Contractor question: When asked about the current alignment, the contractor inquired if there was any flexibility to shift the outfall slightly south, as flatter ground in that direction could facilitate pad construction.

ODOT Response: The design team clarified that the current alignment was chosen to stay outside the boundary of a known landslide complex, which cuts through the existing culvert, and that moving further south would re-enter unstable ground.

Acknowledging this, the contractor said that if the alignment must remain where it is, the next step would be to evaluate what ground conditions exist at the downstream side and whether a pad can be constructed safely and effectively. They suggested that alignment

May 9, 2025 7 modifications might be possible to slightly improve feasibility of jacking pad construction, such as shifting the outfall a little south if it turns out the slope is gentler there.

2. ODOT question to Contractors: Do contractors expect us to specify the anticipated method for trenchless construction, or do trenchless specialty contractors generally choose the tooling based on their own assessment of subsurface conditions?

What are the advantages or disadvantages of the Agency limiting the allowable methods/tooling?

Summary of Contractor Responses:

Whether ODOT should specify the trenchless method or leave the decision to the contractor was described by both contractors as a nuanced issue. One contractor began by acknowledging that the topic was tricky from their position since they’re not the project owner.

From his perspective, if ODOT were to specify the trenchless method, it would make the bidding process much clearer and more uniform. Contractors would all understand exactly what method was expected, which would make the bid comparison more apples-to-apples, creating a level playing field. However, he warned that the downside of specifying a method is that it could reduce competition. For example, if ODOT mandates jack and bore, they might only get three bids. In contrast, if the specifications are left open-ended and allow for any trenchless method, ODOT may receive bids from contractors proposing microtunneling or horizontal directional drilling (HDD), even if those methods aren’t appropriate. In that case, ODOT could end up with a contractor who underestimates the risk of fluid control or overestimates their method’s capability in the actual site conditions. That’s a risk, especially for an emergency project like this one, where time and reliability are critical.

Other contractor(s) specified that from their perspective, it was more beneficial to define the desired end product rather than the method, which allowed flexibility to adapt to site conditions and select the best tooling accordingly. This approach, they noted, often led to more competitive bids. The team inquired about the risks associated with directional drilling, especially in the context of putting the project out to bid, expressing concern that without limits on acceptable methods, another contractor might choose a risky approach that could jeopardize the quality or feasibility of the project. They confirmed the concern and explained that their recommendation stemmed from experience and professional judgment, though ultimately, a contractor should choose the method best suited to their own expertise, likely resulting in the lowest price.

Some contractors explained that from the owner’s perspective, they should want to minimize the risk of failure, both from a constructability and environmental standpoint. Since the existing culvert has collapsed, selecting a poor method could lead to project failure, legal delays, or environmental harm, all of which defeat the purpose of an emergency fix. The contractors explained that in this case, jack and bore seems like the most appropriate method, as it avoids many of the fluid and vibration risks that come with HDD or pipe ramming (due to pneumatic hammering, especially in a downhill slide zone), and has the most manageable construction profile. The contractor(s) explained further that directional drilling posed significant

May 9, 2025 8 risks, particularly for a 42-inch casing, and that such a large directional drill would require substantial overdrilling, followed by filling the void with drilling fluid to support the hole, which would otherwise remain unsupported without product in place. To the contractor, this seemed rather risky, though they acknowledged others might have different opinions. The contractor emphasized that their team preferred auger boring or pipe jacking due to the unknown ground conditions, which could include logs, rocks, or boulders. These conditions were best managed with methods that allowed manual retrieval or tunneling.

A contractor added that another option would be to issue the project as an RFP (Request for Proposals) and score submissions based on a matrix of methodology, price, and other evaluation factors. But as it stands, they recommended that ODOT specify jack and bore as the required method. It reduces uncertainty and ensures the job gets done right the first time.

They said, there are many contractors on the West Coast capable of performing jack and bore, so it wouldn’t eliminate competition entirely. The question is whether ODOT prioritizes a lower price with more method flexibility, or lower risk with a specified method.

Another ODOT team member asked for clarification on the difference between jack and bore versus microtunneling. The contractor explained that microtunneling typically uses fluids to cut, much like directional drilling. Fluids are used to excavate and transport spoil back to the shaft, while the casing remains stationary. In contrast, jack and bore pushes both the casing and the cutting head simultaneously, allowing spoil to be removed via auger from within the casing. The contractor added that microtunneling typically starts at pipe sizes of 42 inches and larger, and it’s usually at least twice the cost of jack and bore due to the specialized equipment and setup required. The team also asked whether microtunneling should be excluded from consideration. The contractor suggested that they shouldn’t exclude it outright, but he expressed reservations. The contractor explained that microtunneling was generally very expensive and not well suited for short distances like this one. The setup required a large footprint and utilized a pressurized slurry system, which came with the risk of a frack-out. Again, he concluded that auger boring or pipe jacking remained the most competitive and flexible option. The contractor further clarified that horizontal directional drilling (HDD) is more appropriate for small-diameter pipes and non-grade-sensitive installations, which wouldn’t apply to this culvert project. The contractor recalled that HDPE was listed as a possible material option in earlier documents, which might have suggested HDD compatibility, but he strongly advised against that method here due to the risk of fluid breakout and environmental concerns.

A team member followed up with a question about the jack and bore method, specifically regarding retrieval. If the crew encountered an obstacle such as a timber log or boulder, what would be the minimum bore size needed to manually extract it? The contractor responded that a 42-inch casing was more than adequate for tunneling and retrieving such obstacles. The contractor added that a 36-inch casing should be considered the minimum size for this type of work.

Another team member asked about horizontal and vertical control over a distance like the one in question. The contractor explained that this was where the steering stabilizers came into play. As an example, they shared a recent project where they completed a 340-foot crossing under I-5 using a 36-inch casing. In that case, they came out just three inches above grade. For a 42-inch casing, he noted, the larger pipe would be even more resistant to

May 9, 2025 9 deflection from rocks and other obstructions, increasing the likelihood of staying on grade. The team expressed interest in reviewing that project for potential specification language. The contractor agreed to follow up with ODOT to see if they could obtain the information.

The contractor expressed another critical concern: concrete filling the existing, collapsed culvert. The contractor emphasized that while jack and bore installation is relatively low-stress, concrete filling an old, deteriorated culvert near a marine environment is far more anxiety-inducing. The contractor cited experience on Jerry’s Flat Road near the Rogue River, where they carefully staged concrete fills in three phases to avoid hydraulic pressure blowouts. In that case, they capped the downstream end, pumped in a small volume of concrete, let it cure for a week, then finished the fill. The approach reduced the risk of failure in rotted pipe with multiple holes. The contractor cautioned that ODOT must take the risk of concrete escaping into the ocean seriously, especially given the 90-foot elevation drop from culvert outlet to sea level. This isn’t just a hypothetical issue: fluid concrete can flow through voids and burst from the slope, creating an environmental hazard.

In terms of grouting the space between the steel casing and the surrounding soil, the contractor described their standard approach: using low-pressure cement grout applied through internal grout ports inside the casing after boring is complete. This method seals the annular space created by the slight overcut during boring.

ODOT staff asked whether the CLSM (Controlled Low Strength Material) they usually specify (300 PSI concrete) was appropriate for this fill. The contractor replied that while CLSM is highly flowable and structurally adequate, it also exerts high hydraulic pressure, especially when poured downhill. Given the fragile condition of the old culvert and surrounding fill, he recommended instead using a sanded grout with lower pressure characteristics. The decision would need to be based on field conditions, ideally verified during a site visit.

The contractor concluded this part of the discussion by reiterating that a site visit would be essential for assessing fill risks and developing a sound grouting plan. Several critical decisions, both around method selection and culvert fill, are contingent on a better understanding of site conditions.

3. ODOT question to Contractors: Does the site topography present any concerns or constraints on proposed trenchless installation methods?

Based on the previous discussions, yes. The steep 90-foot elevation drop from the culvert outlet to sea level presents a major risk for fluid escape and hydraulic blowouts, especially if high-pressure methods like horizontal directional drilling (HDD) or controlled low-strength material (CLSM) are used. The slope is also considered landslide-prone, making vibration-intensive methods like pipe ramming unsuitable due to the potential for destabilizing already fragile terrain. Jack and bore was recommended as the most appropriate method, particularly because it does not rely on drilling fluids and generates minimal vibration. Contractors strongly preferred boring uphill, from the lower, downstream outlet to the upstream inlet, because it allows groundwater to drain back

May 9, 2025 10 into the jacking pit, reducing standing water, improving safety during hand tunneling through obstructions, and minimizing slope disturbance. However, establishing the downstream jacking pit may be challenging due to limited space, steep side slopes, and the need for temporary shoring. While both contractors affirmed the feasibility of working within constrained areas using shorter pipe segments and smaller bore pits (e.g., 25 feet by 10 feet), they noted this would come at higher cost due to increased welding and reduced efficiency. Anchoring the bore rig is also dependent on topography; in areas lacking a native backstop, they recommended using embedded steel beams (dead-man anchors), concrete slabs, or even excavators to resist thrust. Environmental constraints prevent lowering the outlet elevation to improve access, which further limits flexibility and reinforces the importance of constructing the jacking pit at the existing outlet location. A site visit was deemed essential to confirm whether the terrain could support the necessary pit dimensions, equipment access, and slope modifications.

Contractor question: What's the testing that has been done to see what the groundwater level tables are at and where they're putting in the bore pit at?

ODOT Response: ODOT performed a suite of field studies through here this last year. We installed vibrating wires, vibrating wire piezometers. ODOT will have that information out and it should be on the on the logs, the geotechnical data sheets that were with the plans, and as well as the engineering geology report that'll be coming out as a bid reference document as part of the project. Thank you.

Subsurface & Environmental

4. ODOT question to Contractors: Would there be any advantages or disadvantages of a 2-pipe system (i.e. casing and carrier pipe), given the subsurface conditions and presence of an active landslide?

The contractor stated that a two-pipe system, meaning a casing pipe with a carrier pipe inside, is acceptable if that’s what ODOT prefers. However, they emphasized that there are pros and cons. The contractor(s) explained that using a steel casing as the culvert itself has the benefit of being fully restrained by welding, forming one solid, structural pipe. This makes it a robust installation.

The main drawback, they noted, is that the steel would be exposed to the elements from the inside, which raises corrosion concerns, especially if the surrounding soil or groundwater is particularly caustic. To mitigate that, the industry typically uses a thicker-walled casing, which is designed with an engineered lifespan in mind.

The contractor went on to say that there are other options if corrosion or durability is a concern. For instance, the project could involve installing the steel casing and then lining it with a CIPP (Cured-In-Place Pipe) afterward. While they pointed out that CIPP is expensive, it is impervious and “will literally never fail.” This makes it an attractive option

May 9, 2025 11 in terms of longevity, though not necessarily in terms of cost. The contractor mentioned that CIPP could be particularly costly for a 42-inch diameter pipe, but nonetheless might be worth considering depending on the project’s risk tolerance and long-term goals. The contractor also noted that ODOT already uses CIPP frequently for rehabilitating failing CMPs (corrugated metal pipes).

Another method discussed was the traditional oversized casing with spacers, grout caps, and angular fill, a setup that’s common in ODOT specs for waterline crossings. However, they said this configuration doesn’t make much sense for a culvert, in his opinion.

ODOT clarified that the reason this question was being asked in the first place was due to the presence of a landslide area near the alignment. While the team had tried to shift the alignment outside the known landslide zone, it wasn’t clear whether it had been completely avoided. ODOT continued by asking whether a two-pipe system might have any advantage if ground displacement were to occur. For example, could a two-pipe setup offer better performance if the outer pipe was more rigid and the inner pipe more flexible, and if so, would that provide some added protection in a movement scenario?

The contractor responded that they hadn’t really considered that configuration before. However, they doubted that the steel casing would fail under those conditions.

The contractor emphasized that steel isn’t brittle like ductile materials, it won’t crack or separate under stress, and with a wall thickness between 0.625 and 0.75 inches, the casing would remain intact. In his view, if the steel casing were to fail, then everything else, including the pipe inside it, would fail as well, in fact, the whole road would likely fail at that point and "wash on down to the beach."

Another contractor shared their recommendation regarding whether or not to run a carrier pipe. They explained that, from their perspective, including a carrier pipe added cost with minimal benefit. Instead, they recommended increasing the steel wall thickness of the casing to provide added security during the jacking process. They also advised that the casing should have a fusion bond coating and be finished with an abrasion-resistant overcoat (ARO). The ARO would help protect the fusion bond coating from being scraped off during the jacking process. Once installed, the team should apply cathodic protection to mitigate any horizontal scratches or other damage sustained during installation.

A team member followed up, asking what wall thickness they would use for steel casing in this project. The contractor responded that they would feel comfortable jacking a casing with a ½-inch wall thickness but noted it could be upsized if desired for added service life. ODOT requested clarification, noting that the project was located within an active landslide area. ODOT asked whether an outer casing could serve as a protective layer to reduce stress on a carrier pipe in the event of slope movement. The contractor

May 9, 2025 12 responded that unless a steel carrier pipe was also used inside, they didn’t see the outer casing alone offering significant additional strength. Instead, they recommended putting all the structural strength into the casing by upsizing its wall thickness.

A team member asked for a more detailed explanation of the fusion bond coating. The contractor described it as an epoxy coating typically applied at a shop. The process involved sandblasting the pipe before applying the epoxy, commonly using a product like Scotchcoat 134. While not a coating specialist, the contractor explained that this type of coating was standard for projects like railroad crossings. They added that if the fusion bond was being used, it made sense to include the abrasion-resistant overcoat to protect it further. They confirmed that the coating was shop-applied, except for areas at weld joints (holdbacks), which would require field application. The team then asked for more details about the cathodic protection system. The contractor explained that it involved installing anodes sized appropriately for the steel, which would help prevent cavitation and rust.

One team member asked whether the coatings could substitute entirely for cathodic protection. The contractor replied that technically, the coatings would offer a high level of protection on their own. However, to maximize the lifespan of the casing, using both the fusion bond/ARO system and cathodic protection together would be the best strategy.

ODOT asked a follow-up question about the jacking process. ODOT inquired whether the annular space around the pipe, created by the oversized bore, was typically grouted and how that process worked. The contractor explained that they typically installed a 2-inch grout port at the center of each 20-foot pipe section. After installing the casing, they would place valves on the ports and pressure grout with a very flowable cement-water mix to fill any voids caused by over-excavation or washouts.

ODOT then asked if the contractor had ever considered alternative grouting methods that didn’t require ports, such as running a pipe along the outside. The contractor confirmed that, in the past, they had run small-diameter external pipes to inject bentonite and reduce jacking friction. However, this method was challenging due to the difficulty of targeting specific areas, especially since the slurry would be pumped from only one end. The contractor explained that standard practice was to grout through interior ports using pressure from inside the casing. Another team member clarified that factory-installed grout ports would be applied before coating, minimizing corrosion risks.

These ports would contain steel plugs, but their installation before coating helped protect the entire surface. When asked about the typical port placement, the contractor explained that there was little industry standardization, but they generally installed ports at the 12 o’clock (top center) position, every 20 feet. That method had yielded successful results in the past. The contractor noted that additional ports could be added if desired.

For example, a project starting soon in Bend required ports every five feet, with three ports per interval. However, they felt that level of frequency was excessive and not

May 9, 2025 13 necessary based on his experience. A question was raised about whether those requirements were dictated in the project specs or left to contractor discretion. The contractor confirmed that, in the Bend case, the specifications mandated the grouting port spacing, so they had no flexibility. An ODOT team member, commented that he personally preferred ports on top and was seeking clarification on common industry practices.

The group discussed what they typically saw in specifications. The contractor noted that specs often simply stated the annular space needed to be filled and left it to the contractor to determine the best method and mix. The key, they emphasized, was to avoid using the wrong grout, which could result in incomplete filling.

ODOT added that ODOT’s standard 406 specs required grout ports to be installed both at the springline and crown of the pipe at 10-foot intervals. ODOT noted that this specification would need to be either retained or revised, depending on what the team ultimately decided. Another ODOT team member commented that, in his opinion, the spec seemed excessive. The team member was confident they could achieve full annulus grouting with a single port at the crown every 20 feet. The contractor agreed, stating that 20-foot spacing was sufficient and that voids typically occurred at the top of the casing rather than the bottom. The contractor concluded by saying that if more coverage was truly necessary, they could space ports every 10 feet at the crown using couplings.

5. ODOT question to Contractors: What are major issues to be expected with construction here (Ground water, boulders, etc.)? Are there ways to mitigate these major issues?

The contractor(s) acknowledged that much of this question had already been addressed in previous responses, particularly regarding site issues like access, pad construction, and boulders. The contractor reiterated that dealing with boulders requires either the right tooling to cut through them or the ability to remove them manually from inside the casing. Jack and bore, they said, was the appropriate method to allow for that kind of internal hand work when necessary.

Regarding groundwater, the contractor said that ideally, the bore would proceed uphill, so that groundwater would naturally drain out of the casing. But if boring from the downhill side isn't possible, then groundwater can still be managed by climbing inside the casing with a small pump and pumping it out. The contractor emphasized the low-tech, straightforward solution that they’ve used many times.

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Another contractor recommended installing deep dewatering wells prior to excavation of the launch and reception shafts. These wells would help drain groundwater locally and reduce the overall water impact during construction. They explained that constructing both the bore pit and reception pit in advance helped alleviate groundwater pressure, and that this method had proven effective on past projects. For example, in a prior project, the team had worked 11 feet below the water table. They installed six deep dewatering wells at the launch shaft and three at the reception shaft. The bore pit on that project was approximately 28 to 30 feet deep, while the wells reached a depth of around 60 feet. The contractor reported good success with this dewatering strategy.

A team member asked whether the wells were 1–2 inches in diameter, as initially assumed. The contractor clarified that the dewatering wells used were 12-inch diameter casings and approximately 60 feet deep. They were asked how the pumped water was managed. The contractor explained that on the project, water was pumped first into a Baker tank, then into a filter bag (also referred to as a bile bag), and finally discharged into a storm drain. By that stage, the water was considered very clean, often entering the Baker tank already undisturbed. At the end of the project, the team pulled the well casing and backfilled the holes with bentonite to complete the dewatering process.

At this point, ODOT raised a question about whether a settling basin would be needed to manage groundwater running out of the pipe during construction.

The contractor responded directly: “Yes, we would [install one].” The contractor elaborated that while they aren’t adding any fluids, so there’s no need for treatment of contaminants, silt control is still necessary. Their approach would be to pump the groundwater either to a settlement tank or through a silt bag, ideally surrounded by hay bales and waddles, so that the water can disperse naturally like rain runoff while capturing the sediment.

As for placement of the settling facility, the contractor said they would build it on the downstream end, preferably in a flatter area, and off the access road. The ideal location would be as close to the existing outfall as possible.

The contractor then pointed out a small design note: in one of the provided plan visuals, the silt fence appeared to block off the existing outfall, which he noted would obviously have to be accessed and tied into during construction. The contractor acknowledged this was probably something the design team would catch eventually but emphasized that the silt fence would need to be extended down to the existing outlet and likewise for the new outlet location, since work would be taking place there too. The contractor again emphasized that placing a silt bag at the existing outlet would be ideal, assuming it’s within the in-water work period. If that’s not possible, then the discharge facility should be relocated to a flat spot where groundwater naturally exits.

Then ODOT opined with a follow-up based on one of the photos they had reviewed earlier. The contractor recalled seeing a skid steer in the image and said he remembered someone mentioning that the outlet pipe would emerge somewhere uphill of that machine.

ODOT asked whether it would be beneficial, from a jack and bore perspective, if the pipe could come out closer to the elevation of the road instead of higher up on the hill.

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The contractor confirmed: yes, keeping the outlet lower would be better. The contractor explained that elevating the outlet would require more anchoring due to the additional torque involved with boring into an elevated structure. Furthermore, a lower outlet also reduces the amount of rock that needs to be placed for the outlet structure itself. So, from both a construction and efficiency standpoint, the closer to ground level, the better for everyone.

Regarding boulders, a contractor noted that their steering system allowed sufficient access to remove obstructions without major limitations. They had a good track record of handling such issues. The contractor also addressed how boulders and other obstructions were handled in the bidding process. Sometimes, project specifications included line items for obstruction removal; other times, they did not. This variability raised the question of whether the cost for potential obstructions should be built into the base bid or paid out based on an hourly rate if encountered.

A team member asked how obstructions had been handled on a previous project.

The contractor said that in that case, no obstructions were encountered, but they usually included an hourly obstruction rate in their quotes, measured from the time they began addressing the obstruction until normal boring operations resumed. If no such line item existed in the specs, it could create ambiguity in the field. The contractor added that, from ODOT’s perspective, it was always better to anticipate obstructions and agree on pricing ahead of time.

Trying to negotiate in the field, he said, was often more difficult and less cost-effective. By including pre-negotiated rates in the bid, the state could ensure a more competitive and transparent process. When asked how obstruction time was measured in the field, the Contractor explained that under normal auger boring conditions, casing and augers were advanced simultaneously. However, if hydraulic pressure spiked, it usually indicated that the system had hit an obstruction. At that point, they would stop advancement and begin pulling out the augers. The hourly rate would start from the moment normal advancement ceased. After pulling out, they would investigate, identify the obstruction, and begin the removal process. The total time and cost would depend on the type and size of the obstruction, but having a predetermined rate ensured clarity and avoided delays.

6. ODOT question to Contractors: What are reasonable/appropriate tolerances of slope of pipe for the anticipated subsurface conditions?

The contractor(s) affirmed that a 3% slope is excellent and very manageable.

The contractor stated that they can handle slopes up to 15% without too much difficulty.

Regarding accuracy, they explained that the industry standard tolerance for jack and bore operations is 1% of the bore length. For example, on a 300-foot bore, a 1% deviation would equate to about 3 feet. However, they emphasized that with modern steering technologies, their actual performance is typically much more accurate than the industry average. The contractor added that if the target slope is 3%, the worst-case outcome might be a final slope of 2% depending on subsurface conditions encountered during the bore. The contractor(s) explained that if boring from the downhill (outlet) side, the inlet elevation may need to be field-adjusted depending on where the bore ends up.

Similarly, if boring from the uphill (inlet) side, the outlet location might need to be field-fit.

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The contractor noted that boulders and other subsurface conditions can deflect the bore in either direction, and these types of field adjustments are a standard and expected part of the jack and bore process. In general, multiple contractors noted that soil conditions would decide tolerances, as certain soils could cause more deviation during the bore.

However, given the significant grade at the site, they felt confident there was enough room to avoid any bellies in the pipe. Overall, they believed it would be possible to deliver a high-quality product that stayed on both target and grade.

In a…