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Estimating and Contracting Rock Slope Scaling Adjacent to Highways (2020)

Chapter: Appendix B - Questionnaire Responses

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Suggested Citation:"Appendix B - Questionnaire Responses." National Academies of Sciences, Engineering, and Medicine. 2020. Estimating and Contracting Rock Slope Scaling Adjacent to Highways. Washington, DC: The National Academies Press. doi: 10.17226/25824.
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Suggested Citation:"Appendix B - Questionnaire Responses." National Academies of Sciences, Engineering, and Medicine. 2020. Estimating and Contracting Rock Slope Scaling Adjacent to Highways. Washington, DC: The National Academies Press. doi: 10.17226/25824.
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Suggested Citation:"Appendix B - Questionnaire Responses." National Academies of Sciences, Engineering, and Medicine. 2020. Estimating and Contracting Rock Slope Scaling Adjacent to Highways. Washington, DC: The National Academies Press. doi: 10.17226/25824.
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Suggested Citation:"Appendix B - Questionnaire Responses." National Academies of Sciences, Engineering, and Medicine. 2020. Estimating and Contracting Rock Slope Scaling Adjacent to Highways. Washington, DC: The National Academies Press. doi: 10.17226/25824.
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Suggested Citation:"Appendix B - Questionnaire Responses." National Academies of Sciences, Engineering, and Medicine. 2020. Estimating and Contracting Rock Slope Scaling Adjacent to Highways. Washington, DC: The National Academies Press. doi: 10.17226/25824.
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Suggested Citation:"Appendix B - Questionnaire Responses." National Academies of Sciences, Engineering, and Medicine. 2020. Estimating and Contracting Rock Slope Scaling Adjacent to Highways. Washington, DC: The National Academies Press. doi: 10.17226/25824.
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Suggested Citation:"Appendix B - Questionnaire Responses." National Academies of Sciences, Engineering, and Medicine. 2020. Estimating and Contracting Rock Slope Scaling Adjacent to Highways. Washington, DC: The National Academies Press. doi: 10.17226/25824.
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Suggested Citation:"Appendix B - Questionnaire Responses." National Academies of Sciences, Engineering, and Medicine. 2020. Estimating and Contracting Rock Slope Scaling Adjacent to Highways. Washington, DC: The National Academies Press. doi: 10.17226/25824.
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Suggested Citation:"Appendix B - Questionnaire Responses." National Academies of Sciences, Engineering, and Medicine. 2020. Estimating and Contracting Rock Slope Scaling Adjacent to Highways. Washington, DC: The National Academies Press. doi: 10.17226/25824.
×
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Suggested Citation:"Appendix B - Questionnaire Responses." National Academies of Sciences, Engineering, and Medicine. 2020. Estimating and Contracting Rock Slope Scaling Adjacent to Highways. Washington, DC: The National Academies Press. doi: 10.17226/25824.
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Suggested Citation:"Appendix B - Questionnaire Responses." National Academies of Sciences, Engineering, and Medicine. 2020. Estimating and Contracting Rock Slope Scaling Adjacent to Highways. Washington, DC: The National Academies Press. doi: 10.17226/25824.
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Suggested Citation:"Appendix B - Questionnaire Responses." National Academies of Sciences, Engineering, and Medicine. 2020. Estimating and Contracting Rock Slope Scaling Adjacent to Highways. Washington, DC: The National Academies Press. doi: 10.17226/25824.
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Suggested Citation:"Appendix B - Questionnaire Responses." National Academies of Sciences, Engineering, and Medicine. 2020. Estimating and Contracting Rock Slope Scaling Adjacent to Highways. Washington, DC: The National Academies Press. doi: 10.17226/25824.
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Suggested Citation:"Appendix B - Questionnaire Responses." National Academies of Sciences, Engineering, and Medicine. 2020. Estimating and Contracting Rock Slope Scaling Adjacent to Highways. Washington, DC: The National Academies Press. doi: 10.17226/25824.
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Suggested Citation:"Appendix B - Questionnaire Responses." National Academies of Sciences, Engineering, and Medicine. 2020. Estimating and Contracting Rock Slope Scaling Adjacent to Highways. Washington, DC: The National Academies Press. doi: 10.17226/25824.
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Suggested Citation:"Appendix B - Questionnaire Responses." National Academies of Sciences, Engineering, and Medicine. 2020. Estimating and Contracting Rock Slope Scaling Adjacent to Highways. Washington, DC: The National Academies Press. doi: 10.17226/25824.
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Suggested Citation:"Appendix B - Questionnaire Responses." National Academies of Sciences, Engineering, and Medicine. 2020. Estimating and Contracting Rock Slope Scaling Adjacent to Highways. Washington, DC: The National Academies Press. doi: 10.17226/25824.
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Suggested Citation:"Appendix B - Questionnaire Responses." National Academies of Sciences, Engineering, and Medicine. 2020. Estimating and Contracting Rock Slope Scaling Adjacent to Highways. Washington, DC: The National Academies Press. doi: 10.17226/25824.
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Suggested Citation:"Appendix B - Questionnaire Responses." National Academies of Sciences, Engineering, and Medicine. 2020. Estimating and Contracting Rock Slope Scaling Adjacent to Highways. Washington, DC: The National Academies Press. doi: 10.17226/25824.
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Suggested Citation:"Appendix B - Questionnaire Responses." National Academies of Sciences, Engineering, and Medicine. 2020. Estimating and Contracting Rock Slope Scaling Adjacent to Highways. Washington, DC: The National Academies Press. doi: 10.17226/25824.
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58 A P P E N D I X B Questionnaire Responses Note that responses have had geographic identifiers removed. Question: Scaling projects are often selected using a variety of methods; some planned and some unplanned. Of the following project selection methods, please fill in the general percentage (0 to 100 scale) adding up to 100 (required) for each method. General percentages based on recollection (+/– 10%) are okay. ANSWER CHOICES AVERAGE NUMBER TOTAL NUMBER RESPONSES Performed as a routine maintenance exercise and/or part of a maintenance program 12 212 17 Performed as part of other highway preservation work (paving, minor realignments, major ditch rehabilitation, guardrail replacements, etc.) 25 455 18 Programmed as part of a Statewide Transportation Improvement Program (STIP), a Highway Safety Improvement Program (HSIP), or other statewide or regional project candidate as part of a larger rockfall mitigation project 40 875 22 Performed on an emergency basis following rockfall events 34 818 24 Other (comment below) 7 40 6 Comments: […] districts are autonomous of each other. Depending on the district and its management, routine scaling work may or may not be done at all. At the moment the majority of rock scaling throughout […] is done on a reactive approach. However […] now has a rockfall management program and in the future with a proactive approach these numbers will change. Performed as design recommendation after rockfall modeling during construction. As requested by […] Maintenance Division for spot improvement of problematic sites.

Questionnaire Responses 59 Question: How do scaling contractors generally get selected? Of the following methods, please fill in the general percentage (0 to 100 scale) adding up to 100 (required) for each method. General percentages based on recollection (+/– 10%) are okay. ANSWER CHOICES AVERAGE NUMBER TOTAL NUMBER RESPONSES Prequalified scaler and/or contractor, on-call list for emergency response 28 275 10 Not-prequalified, on-call list for emergency response 28 250 9 Low bid, qualifications of scalers and/or contractor required 33 457 14 Low bid 20 100 5 Hired by general contractor without qualification requirements 15 135 9 Hired by general contractor with qualification requirements 68 1083 16 Other (Comment Below) 25 100 4 Comments: In my district we have a yearly rockfall mitigation contract that is paid out of maintenance funding to the district. Under this contract in our district we scale and hang draped rockfall netting and perform erosion control installations to establish vegetation and reduce rockfall on selected slopes. […] is currently in the process to create a prequalified scaler list. But this is in the works. We typically write the special provisions, but do not get involved in the selection process. When done in-house, our maintenance crews perform the work under a geologist’s supervision and guidance. Question: What level of effort does your department typically use for designing and specifying scaling activities? ANSWER CHOICES NUMBER OF RESPONSES RESPONSES (PERCENT) Maintenance activity and observations 14 58.33% Roadside visual review by department or consultant geotechnical design personnel 23 95.83% Up-close slope inspection by personnel in boom lifts, crane baskets, or on ropes 13 54.17% Advanced laser scanning and/or photogrammetric techniques 10 41.67% Other (please specify) 5 20.83% Comments: I select sites and have used many measures for selection as detailed above. Each site requires different levels of effort. All of the above. […] is in the first stages of utilizing UAV inspection of slopes. […] has only recently started to use terrestrial lidar and UAV lidar. Photogrammetric techniques are used on a case-by-case basis. We are beginning to look at ground and aerial UAV tools to help us monitor scaling pre- and post-scaling rockfall.

60 Estimating and Contracting Rock Slope Scaling Adjacent to Highways Question: How does your department estimate the volume of scaling debris for removal and haul? ANSWER CHOICES NUMBER OF RESPONSES RESPONSES (PERCENT) Expert judgement for rock type and rock quality 16 66.67% Volume & area relationships (e.g., ½ cy per 100 sf of slope to be scaled) 9 37.50% Other (please specify) 5 20.83% Unit (vol./weight) production per scaler hour (e.g. ½ cy per scaler hour) 4 16.67% Weight & area relationships (e.g., 1 ton per 100 sf of slope to be scaled) 1 4.17% Comments: Under our yearly program we are tied into scaling work with department forces and equipment. Our maintenance crews do the haul and roadway and ditch cleanup. We count loads to estimate the amount of material removed from the slope but generally we scale until I decide that we are done. Under programmed projects we have used varied methods and await the next project for evaluation of lidar data for estimating purposes. My first project was done by consultants and estimates were based on expert knowledge and cross sections. Payment was by the ton removed. Department is progressing towards using more detailed topographic and/or lidar surveys to more accurately determine the quantity of rock that needs to be removed. We add a 30% bulk volume increase of calculated volume of scaled material. Visual estimate of total quantity. Estimate excavation quantity from surveyed cross sections or assumed typical section area of debris removal . Question: How does your department estimate scaling production rates? ANSWER CHOICES NUMBER OF RESPONSES RESPONSES (PERCENT) Expert judgement for individual slopes 18 75.00% Expert judgement for various scaling levels of effort 13 54.17% Other (please specify) 7 29.17% Standard quantity for all slopes 2 8.33% Analytical approach using rock quality indicators (RMR, RQD, GSI, etc.) 2 8.33% A few standard quantities for overburden/rock types, slope geometries, etc. 0 0% Proprietary methods 0 0% Comments: On maintenance projects it’s expert judgment. On programmed projects it’s a mix depending on the slope. […] bids scaling by square yard of rock face. We are currently reviewing our bid process for rock scaling. Scaling production rates are estimated only for project scheduling purposes; payment is based on other factors . Generally do not figure rates. Most done as lump sum or time and materials. 200 SF/HR is our published guidance in Supplemental Specification 862 (starting point for an estimate) . We have looked at past levels of effort put into scaling on previous rock slope remediation projects to help us with our estimation of hand scaling production rates. Essentially hours per rope set and add traffic cue clearing time.

Questionnaire Responses 61 Question: In your department’s experience, what is considered a “reasonable” production rate for “General Scaling”? For consistency between geologic materials and project purposes, presume a non- presplit rock slope, an RQD of 60%, and as part of a larger rockfall mitigation project within a two- lane, rural, mountainous highway corridor with scaling performed using rope access methods. ANSWER CHOICES NUMBER OF RESPONSES RESPONSES (PERCENT) Too variable to answer. 11 47.83% 50–200 square feet per individual scaler hour. 6 26.09% 200–400 square feet per individual scaler hour. 3 13.04% 400–800 square feet per individual scaler hour. 3 13.04% 800+ square feet per individual scaler hour. 0 0%

62 Estimating and Contracting Rock Slope Scaling Adjacent to Highways Question: Which units does your department most frequently use to measure scaling quantities? If multiple methods are used, select which one has had the most success. ANSWER CHOICES NUMBER OF RESPONSES RESPONSES (PERCENT) Hours (Crew Hours) 12 50.00% Hours (Individual Scaler Hours) 4 16.67% Unit Volume 3 12.50% Other (please specify) 3 12.50% Unit Area 2 8.33% Unit Length 0 0% Lump Sum 0 0% Comments: Not sure, either unit volume or lump sum. Scaling operations are paid by Unit Area; debris is removed and paid by Unit Volume. Hours (Crew Hours) with supplemental pay items for Trimblasting (SF) and Debris Removal/Excavation (CY).

Questionnaire Responses 63 Question: Does your department use separate bid items for different scaling techniques (hand scaling from ropes, hand scaling from lifts, mechanical scaling, air-pillows, heavy scaling, etc.)? ANSWER CHOICES NUMBER OF RESPONSES RESPONSES (PERCENT) Yes 12 50.00% No 8 33.33% Other (please specify) 4 16.67% Comments: We typically only use a single bid item for scaling, which indicates scaling from ropes or lifts using scaling bars or air-pillows. We have discussed using mechanical scaling techniques but this is not typical for our department and would require a separate bid item. Typically “No” but have used CY for mechanical scaling on limited # (less than 10%) of projects. In the past hand scaling bid item has included all work with pry bars as well as using air bags, hydraulic splitters, expanding grout, and other propellant-based systems. Currently we have begun to separate hand scaling with pry bars using rappel from air bagging/splitting/expanding grout/etc. We call this item “Mechanical Scaling,” which is separate from “Machine Scaling,” which is defined as using heavy equipment to rip loose rock out either with a bucket and/or hammer. Slope scaling includes all scaling techniques other than excavator or crane-assisted mechanical scaling.

64 Estimating and Contracting Rock Slope Scaling Adjacent to Highways Question: What is your department’s preferred method for delineating scaling extents in the plan drawings? ANSWER CHOICES NUMBER OF RESPONSES RESPONSES (PERCENT) Oblique photographs with scaling extents drawn 11 45.83% Plan view drawings with scaling station-extent shown 5 20.83% Scaling extents by station in a table 3 12.50% Other (please specify) 5 20.83% Comments: We typically use both photographs and plans. Plan view drawings with scaling station-extent (we also use photos and have a Geologist on site to direct contractor to achieve preferred results). Show stop/start limits by station. Onsite scaling direction during scaling from qualified personnel. […] Slope Assessment Forms (assess the safety and goals of slopes for scaling operation). Annotated panel photos of rock cut by stationing depicting areas to be scaled and expected degree of effort (heavy scaling vs. general scaling). Preferred Method for Delineating Scaling Extents

Questionnaire Responses 65 Question: Does your department specify performance criteria that defines satisfactory scaling or to otherwise judge when scaling is complete? ANSWER CHOICES NUMBER OF RESPONSES RESPONSES (PERCENT) Yes 6 25.00% No 12 50.00% Other (please specify) 6 25.00% Comments: I use visual examination. When double twist or other mesh is to be installed I require that scaling must remove all loose rock capable of exceeding the capacity or the mesh to contain without damage. I instruct the scaling crew to use their professional judgment when double twist mesh is being installed to inform the inspector when they believe scaling is complete and no obvious loose rocks capable of damaging the mesh have been removed. I then usually review the slope visually or in some cases rappel areas to confirm their assessment. I take into account slope elevation and observe rock roll outs to determine the point when rock will no longer reach the roadway also to assess completion of scaling. Scaling is always specified “as directed by the Engineer” which indicates that the construction inspector determines when scaling is complete. There is no standard performance criteria that the inspector uses but it prevents the contractor from determining scaling extents and duration. See question 3. Scaling completion/adequacy is determined by visual inspection by Engineering Geologist designer of record. Performed to the satisfaction of the project geologist. Onsite scaling review by qualified personnel. Slope Assessment Form [requires] onsite evaluation and whether we met the goals set out in Slope Assessment Form.

66 Estimating and Contracting Rock Slope Scaling Adjacent to Highways Question: If your department requires qualifications for scaling, whom do they apply to? ANSWER CHOICES NUMBER OF RESPONSES RESPONSES (PERCENT) All scaling personnel 13 54.17% All scaling personnel, but with a training/journeyman provision 5 20.83% Not applicable 4 16.67% Foremen only 1 4.17% For the company as a whole rather than on a person-by-person basis 1 4.17% Other (please specify) 1 4.17% Comments: We are not too involved with consultant selection processes. Question: If your department requires prequalification for scaling, what are the qualifications? ANSWER CHOICES NUMBER OF RESPONSES RESPONSES (PERCENT) Not applicable 4 16.67% Hours of experience per qualified scaler 8 33.33% Number of projects completed per scaler 0 0% Number of years of scaling work (per company) 1 4.17% Number of projects for scaling work (per company) 3 12.50% References from past clients (per company) 0 0% Other (please specify) 8 33.33% Comments: We have used number of projects completed per company and number of years of scaling work per scaler. We are not too involved with consultant selection processes. Number of year per scaler on similar projects. General requirement assumption that individual scalers are comfortable with the described methods at height. Loosely quoted as “a description of all the likely techniques and that the personnel are experienced doing this at the prescribed height.” Years of scaling with foreman/training exemption […] uses a combination of choices 2–6. Years of experience for scalers/foreman/past project experience. Hours of experience, minimum number of scaling jobs, and sometimes references on complex slopes.

Questionnaire Responses 67 Question: If paying hourly, when does scaling typically “start”? ANSWER CHOICES NUMBER OF RESPONSES RESPONSES (PERCENT) Not applicable 6 25.00% When ascending (e.g., hiking, boom lift, helicopter, etc.) to the top of the slope 5 20.83% Beginning of the shift 5 20.83% When in position and actively scaling using the allowed scaling methods 4 16.67% Other (please specify) 3 12.50% When ascending the slope while harnessed up 1 4.17% Comments: When fully staffed crew is working on the slope. Varies per contract. When actively getting harnessed up and preparing rigging to begin scaling activities.

68 Estimating and Contracting Rock Slope Scaling Adjacent to Highways Question: How does your department measure and pay for removal of scaling debris? ANSWER CHOICES NUMBER OF RESPONSES RESPONSES (PERCENT) Unit volume removed 10 41.67% Other (please specify) 5 20.83% Incidental to scaling 4 16.67% Lump sum 2 8.33% Time & materials 2 8.33% Unit weight measured 1 4.17% Comments: We have used both lump sum and unit weight. Weight requires scales which is not always practical. I believe this is best determined based on the scaling site specifics and the logistics related to the waste site. Either unit weight or volume. Depends on the amount and if we have lidar set up in contract. Either unit volume removed or time and materials (equipment hours). Either lump sum or unit volume removed. Has been incidental to scaling but is being updated to unit volume removed.

Questionnaire Responses 69 Question: How does your department handle “safety scaling” requested by the Contractor not specified in the Plans? For purposes of this survey only, “safety scaling” is scaling requested by the scaling contractor that falls outside the scaling boundaries required in the plan and specifications package. ANSWER CHOICES NUMBER OF RESPONSES RESPONSES (PERCENT) Case-by-case 10 41.67% Pay it at the contract rate 9 37.50% It is considered incidental 3 12.50% Other (please specify) 2 8.33% Pay at a new, negotiated rate 1 4.17% Comments: Safety scaling is a difficult subject. If it’s for the contractors’ convenience then it’s incidental; if it potentially has production implications to the rest of the project, then it’s paid by the contract rate with a no-effect change order that does not allow renegotiating prices. If it’s truly for the safety of the scalers to be able to perform the contract scaling as outlined in the plans, then we prefer to negotiate a separate price. In reality you can’t ask them to scale below a hazard that you know about without some form of payment. Scope escalations initiated by the contractor are not allowed. Question: What tasks are measured and paid as “scaling”? ANSWER CHOICES NUMBER OF RESPONSES RESPONSES (PERCENT) Non-scaling foreman 15 65.22% Labor to support scaling/equipment moving (air hoses, ropes, etc.) while not harnessed up 15 65.22% Tree/vegetation removal at the slope crest and/or on the slope 14 60.87% Bench cleaning 11 47.83% Safety spotters 10 43.48% Other (please specify) 4 17.39% Comments: On typical projects only scaling vegetation removal at the crest of the slope and/or on the slope are paid as scaling. On maintenance projects directed by the state, it’s all things that need being done so as to reduce the overall manpower needs on the project. Only rock removal is paid as scaling. Safety spotters are on a case-by-case basis. Non-scaling foreman is required but not paid separately; general labor and tree/vegetation removal are paid as separate items. We do not get very involved with […] contracts regarding pay items. Lump sum or time and materials.

70 Estimating and Contracting Rock Slope Scaling Adjacent to Highways Question: If your department requires temporary roadway/property protection (e.g., pavement, appurtenant structure, river, or property protection rather than safety-related protection) during scaling, is it: ANSWER CHOICES NUMBER OF RESPONSES RESPONSES (PERCENT) Contractor designed? 13 54.17% Designed by the Owner or their representative? 5 20.83% Other (please specify) 5 20.83% We do not require roadway protection. 1 4.17% Comments: Both contractor designed on projects and state designed on maintenance projects. It has been both designed by owner and designed by contractor. We have used both owner-designed and supplied systems, and contractor-designed and supplied systems. The manner in which we handle this varies by contract. In some cases, we design sand blankets or use owner- selected barriers. In many cases, protection of features is up to the contractor. Often contractor designed with performance specification and submittal requirements but when environmental clearance is required prior to design completion, the protection plan is designed by the Owner so NEPA can be completed prior to construction. Question: If your department requires temporary rockfall protection (e.g., rockfall safety protection for public or others), is it: ANSWER CHOICES NUMBER OF RESPONSES RESPONSES (PERCENT) Contractor designed? 10 41.67% Designed by the Owner or their representative? 5 20.83% Other (please specify) 5 20.83% We always completely close the road, so rockfall protection for the public is not needed 4 16.67% Comments: Both contractor designed on projects and state closes road on maintenance projects. It has been both designed by owner and designed by contractor. Varies. We typically run a rudimentary or complete rockfall simulation to determine road closure. If it is even in the realm of being safe we will see what’s available to the contractor and re-assess. For program work we evaluate proposals from the contractor. […] uses both Owner-designed and Contractor-designed systems, depending on the project. When possible, we completely close the road for 2- to 4-hour time-frames with limited daily openings. Otherwise, it is the same as answered for [the prior question].

Questionnaire Responses 71 Question: If your department uses temporary rockfall protection measures to facilitate traffic passage, please indicate the success of each measure as part of a temporary rockfall protection system. ANSWER CHOICES NOT USED IN OUR DEPARTMENT FAILED WHEN USED ON A STAND- ALONE BASIS MINOR CONTRIBUTOR TO SYSTEM SUCCESS MAJOR CONTRIBUTOR TO SYSTEM SUCCESS TOTAL RESPONDENTS Freshly cleaned catchment ditch 20.00% ( total) 4 (count) 0% 0 40.00% 8 40.00% 8 20 Energy-absorbing gravel blanket 36.84% 7 0% 0 57.89% 11 5.26% 1 19 Construction material barrier (plywood/hay bales/debris berm/sand bags/etc.) 57.89% 11 0% 0 26.32% 5 15.79% 3 19 Concrete barriers 5.00% 1 10.00% 2 40.00% 8 45.00% 9 20 Stationary rockfall barrier 52.63% 10 0% 0 0% 0 47.37% 9 19 Shipping containers or other barriers 57.89% 11 0% 0 5.26% 1 36.84% 7 19 Barrier-mounted fence extension for small debris 50.00% 10 0% 0 25.00% 5 25.00% 5 20 Moveable rockfall barrier 23.81% 5 0% 0 4.76% 1 71.43% 15 21 Crane-supported debris barrier 47.37% 9 0% 0 15.79% 3 36.84% 7 19 Other 100.00 2 0% 0 0% 0 0% 0 2 Comments: My district does use some of these methods above but has never allowed live traffic while scaling. The systems above were used to facilitate road cleanup to release traffic after temporary closures . We assume moveable rockfall barrier includes portable concrete barrier.

72 Estimating and Contracting Rock Slope Scaling Adjacent to Highways Question: How does your department inspect and review scaling activities (multiple choice)? ANSWER CHOICES NUMBER OF RESPONSES RESPONSES (PERCENT) Inspector reviews from the ground as part of other inspection duties 18 75.00% Inspector with rock slope experience (in-house or consultant) reviews performance by accessing the slope via ropes or other slope access technique (i.e., boom lift, crane basket, etc.) 16 66.67% Inspector with rock slope experience (in-house or consultant) inspects performance from the ground full-time 11 45.83 Other (please specify) 6 25.00 Comments: Inspector with rock slope experience inspects part-time. Inspector is briefed on process w/r/t time and expected techniques. Periodic inspection by geotech staff. Inspector review from ground is primary. Inspection by accessing the slope is limited (maybe 10–20% of time). Assisted by departmental geologist. […] is exploring the use of UAVs for pre- and post-scaling inspection. Owner Inspector trained by engineering geologists before project starts and engineering geologists often visit the site for final “buyoff” evaluation of the slope scaling before other rockfall mitigation activities commence. Question: Who accepts the completed scaling work (multiple choice)? ANSWER CHOICES NUMBER OF RESPONSES RESPONSES (PERCENT) Experienced designer with on-slope verification 12 50.00% Construction engineer with scaling experience 11 45.83% Construction engineer without scaling experience 9 37.50% Other (please specify) 5 20.83% They are done when the budget is exhausted 1 4.17% Comments: Engineering Geologist designer of record typically from the ground, but occasionally from on-rope. Agency Engineering Geology personnel with scaling experience. Assisted by departmental geologist. The […] Engineering Project Manager accepts the work based on technical guidance provided by the Geotechnical Section or their qualified designee. The Agency Geologist and/or qualified inspector views the scaling work at the request of the Resident Engineer. Once approval is given by Geologist/qualified inspector then Resident Engineer accepts the completed scaling work.

Questionnaire Responses 73 Question: Does your department currently or plan to use advanced techniques to measure scaling completion for payment purposes (multiple choice)? ANSWER CHOICES NUMBER OF RESPONSES RESPONSES (PERCENT) Yes, we plan to use advanced techniques to measure scaling completion and area coverage 9 37.50% No 8 33.33% We’ve considered it, but not sure of its use, reliability, or defensibility 6 25.00% Other (please specify) 3 12.50% Yes, we currently use advanced techniques (laser scanner, photogrammetry, etc.) to measure scaling completion and area coverage 2 8.33% Comments: “Advanced techniques” have been used when mechanical scaling is specified with payment in CY. Volume of debris from scaling (scaling measured in $/hr) is measured per SS862 guidance—there are two options: 3-D volume method or “Measured in Vehicle.” Scaling itself will still be measured by hours. Depending on job size, some thought is being given to measuring scaled material quantities via UAV or similar means, but still paid as unclassified excavation. (Typically the material removal is completed by the prime contractor and not directly tied to the scaling items.) We plan to use before-and-after scaling scans to evaluate rockfall activity post-scaling. We haven’t used it for measurements of payment.

74 Estimating and Contracting Rock Slope Scaling Adjacent to Highways Question: Does your department keep records of rockfall activity following scaling? ANSWER CHOICES NUMBER OF RESPONSES RESPONSES (PERCENT) Yes, but kept informally or through job experience 9 37.50% Other (please specify) 8 33.33% No 5 20.83% Yes, and we have documentation that we can share 2 8.33% Comments: We track rockfall events that are reported to the department by county sheriffs, state law enforcement, and individuals, or by maintenance personnel. We keep records through our Maintenance rockfall reporting system but the results are not comprehensive— reporting quality varies across the state. We are happy to share the documentation that we have. Performance of slopes is documented as part of our unstable slope management system. Yes but it isn’t well coordinated. Slope scaling may occur but that information may take time to get to the personnel recording the activity. Yes; kept through continuation of periodic monitoring of all highway rock cuts within our Rockfall Hazard Management System. We have a rockfall reporting system through our maintenance department. This is captured in our Rock Slope Asset Management Program (RAMP), https://www.mdt.mt.gov/other/webdata/external/research/docs/research_proj/rockfall/PROJECT_S UMMARY.pdf. We are not owners of the facilities that we help maintain but we work with the owners to track rockfall activity before and after the scaling. We often participate in adding informat ion to their slope asset management or maintenance information systems for tracking rockfall activity, but more recently, we have been emphasizing instituting an unstable slope management tool for managing their slope assets. Setting this system up for the owner to use prior to the scaling has been very helpful in allowing them to track their slope assets performance. Question: Does your department keep records of slope condition (RHRS ratings, apparent RQD, RMR, etc.) pre- and post-scaling? ANSWER CHOICES NUMBER OF RESPONSES RESPONSES (PERCENT) Yes 13 54.17% No 8 33.33% Other (please specify) 3 12.50% Comments: Each district has or does not have a rockfall inventory system. Mine uses RHRS and we track scaling success and rockfall events after scaling. Some slopes we scale every 2–5 years when frequency of events increases. We try to do another RHRS after scaling but many times the elapsed time is significant . Work with our local maintenance crews to record rockfall event occurrence before and after scaling operations to determine effectiveness.

Questionnaire Responses 75 Question: If your department uses advanced techniques to monitor slope performance following scaling completion, which technique? ANSWER CHOICES NUMBER OF RESPONSES RESPONSES (PERCENT) No, we do not use advanced techniques 18 75.00% Yes, other (please specify) 4 16.67% Yes, we use terrestrial scanner techniques 1 4.17% Yes, we use UAV-based technology (photogrammetry, laser scanner, etc.) 1 4.17% Yes, we use terrestrial photogrammetry techniques 0 0% Comments: We have just begun the process of collecting UAV-based and terrestrial scanner and photogrammetry technology but have not yet collected follow-up scans. We have used both terrestrial lidar, [but] more typically, we use photogrammetric record. We have used terrestrial scanning techniques and are exploring the use of UAV-based technology for future projects. We are starting to use terrestrial with photogrammetry overlays and UAV-based technology to look at slope performance following scaling activities. This discussion and techniques have only been applied with some of our partners through pilot programs in the last 2 years.

76 Estimating and Contracting Rock Slope Scaling Adjacent to Highways Question: If applicable, what lesson has your department learned regarding slope scaling over the past 10 to 20 years? Comments: The more time and experience you spend prior to scaling to access the degree of effort for scaling needed the better the project outcome will be. Accurate surveying of the existing slope topography is important. It is invaluable to have an individual with extensive rock slope experience directing the scaling efforts at a site and determining when scaling is complete. Correct catchment design is strived for if space is available on a given project. Pre-splitting is highly recommended to keep rock mass from becoming damaged (some Districts prefer a more natural rock slope which tends to give more rockfall problems vs. pre-splitting). Ensure that Maintenance knows that it is very important to keep the catchment ditch cleaned out to original design criteria. Build in risk to project (extra contingency) due to unpredictable, variable quantities. Best results occur when Geotech (design expert) is on site to use judgement on scaling locations and quantities. We have seen an interest from contractors to employ “apprentice” scalers, which are not currently allowed in our specification. In cases where roadway or feature protection is provided by the contractor, they often are not prepared to provide a level of protection that we, as the owner, feel is adequate. We have typically experienced difficulties in the accurate estimation of debris removal quantities despite employing a variety of methods. Although some of the observed variability can be attributed to diff iculties in quantifying how rock scales based on its condition, some is likely the result of variation in practice from scaler to scaler. This issue is especially acute on very high slopes. We place a high value on the use of experienced engineering geologists to guide scaling work to reduce the potential for damaging the slope and also for focusing work in targeted areas. We see quite a bit of variation from project office to project office in how scaling hours are counted; do the hours include accessing the slope? How are traffic control delays accounted for? Is a standby rate applied? etc. Experience submittals often vary in how scaling hours are presented and counted, requiring iterative clarification in order to align with our specification. Issues with temporary catchment, productivity rates. Quantities for scaling can almost never be overestimated; scaling operations should be closely monitored and inspected for compliance. Experience is key! Typically only complete this work to address emergencies. We have chosen crew time as opposed to volume production. Mostly because it’s easier for an inspector to record. Additionally, there are a limited number of scaling contractors who work on our projects so we are familiar with their technique, experience and production. That estimating scaling hours and quantity material is very difficult and varies significantly on every job. Lack of [state] based scalers can create $/hr irregularities. Prime contractors are motivated to use earthwork equipment instead of a subcontractor scaling. Relying on general contractors to perform challenging scaling work has become more difficult and we are moving toward using specialty contractors. We have found the maintenance scaling of slopes to be extremely important in improving public safety, reduced maintenance expenses, accelerating emergency openings of highways after storm events and improved protection to state facilities. Photo plans are a tremendous aid for bidding and contract administration. Scaling is cost-effective rock slope mitigation and can be incorporated in larger projects to take advantage of traffic control. Some additional rockfall can be expected and planned for after scaling as the slope re-stabilizes. Performance-based contracts frequently result in cost overruns or poor performance. Prescriptive approaches have been effective in managing contract costs.

Questionnaire Responses 77 We have run into problems with running out of scaling hours on projects before, specifically for two reasons: (1) Extensive vegetation has obscured some areas of the rock cut, making it difficult to predict actual rock slope conditions, leading to change in design once the vegetation is cleared. (2) The rock composing the areas to scale is much more weathered/unstable than anticipated, leading to extra scaling time—the opposite has also been true in the past, where even though numerous joints have been exposed, making easy access for scaling/air bagging, the rock has been competent enough to greatly slow down scaling activities. We have also run into the issue of scaling thoroughness, meaning that there have been disagreements between us and the scalers as to deciding on when an area has been scaled to satisfaction. Use qualification-based requirements for all scaling personnel; provide a safe way for training scalers in your specifications to allow for replenishment of industry workers; require air pillows as mandatory equipment for slope scaling (for general and intensive areas); include safety scaling as incidental to your scaling item; allow contractors to use their ingenuity for protecting property and the roadways through performance specifications and the submittal process; pay by the scaling hour per scaler, not the crew hour or by area on the slope. I would prefer to separate debris removal, including haul, from the slope scaling bid item because it makes it difficult to follow trends in scaling unit bid prices when the debris removal is part of the equation and may heavily influence the unit prices. I am working on this with our construction and contracting folks.

Next: Appendix C - Example Scaling Plan Sheets Submitted by DOTs »
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Scaling loose rock from highway rock slopes is an important aspect of improving rock slope safety in mountainous areas, according to input from 42 state departments of transportation and two regional divisions of the Office of Federal Lands Highway.

The TRB National Cooperative Highway Research Program's NCHRP Synthesis 555: Estimating and Contracting Rock Slope Scaling Adjacent to Highways documents current rock slope scaling practices adjacent to highways.

An appendices document is also included as part of the publication.

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