Earthwork Balance MR-3 Greenroads™ Manual V1.5 Materials & Resources
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Greenroads™ Manual v1.5 Materials & Resources EARTHWORK BALANCE GOAL MR-3 Reduce need for transport of earthen materials by balancing cut and fill quantities. CREDIT REQUIREMENTS Minimize earthwork cut (excavation) and fill (embankment) volumes such that the 1 POINT percent difference between cut and fill is less than or equal to 10% of the average total volume of material moved. For purposes of this credit, use the method and definitions detailed in Chapter 8 (Earthwork) of the Road Design Manual from the South Dakota Department of Transportation (SDDOT), or equivalent, to compute cut and fill volumes. RELATED CREDITS Include miscellaneous additional cut and fill such as outlet ditches and muck PR‐8 Low Impact excavations (see definitions in Chapter 8 of the Manual) and account for moisture and Development density as well as shrink and swell. MR‐2 Pavement Reuse tBalance cu and fill material volumes: MR‐4 Recycled Materials A = Volume of Cross Section Cut MR‐5 Regional B = Volume of Cross Section Fill Materials C = Volume of Miscellaneous Cut D = Volume of Miscellaneous Fill SUSTAINABILITY For points, show that design volumes AND actual construction volumes meet: COMPONENTS Ecology Economy Extent Experience Note that for purposes of this credit, all volumes are positive quantities. SDDOT’s BENEFITS Chapter 8 is available here: http://www.sddot.com/pe/roaddesign/plans_rdmanual.asp Reduces Fossil Fuel Use Details Reduces Air Emissions Projects with minimal earthwork or with no earthwork do not qualify for this Reduces Greenhouse credit. “Minimal earthwork” means that the total excavated cut or imported fill Gases volume is less than one full dump truck volume, based on the smallest dump Reduces Solid Waste truck used on the project. Reduces Manmade Where soil stabilizer materials or other soil additives are used, include the Footprint volume of those materials in the total imports. Mechanical stabilizers such as Reduces First Costs rock bolts and geotextile fabric materials do not need to be included in volume Reduces Lifecycle calculations. Costs Removed topsoil materials must be included in calculations. Unused cut or imported fill materials placed in stockpiles that serve no purpose on the project must be treated as exported materials and may not be used to count toward the final “balanced” section for purposes of calculating this credit. Sometimes this practice is called “soil banking” since these materials are often placed in embankments that may be used at some later time, often on different nearby sites. This practice often helps successfully avoid import of new materials, so it still may qualify for 1 point. Structural aggregate for base courses in pavements, foundations, or MR-3 Earthwork Balance Materials & Resources Greenroads™ Manual v1.5 superstructures such as bridges need not be included in the total volume calculations. Structural backfill and drain rock specifically intended for utility trenches and stormwater infrastructure need not be included in the total volume calculations. Rock (Stable Rock, defined by the Occupational Health and Safety Administration) cuts sourced within the project boundary that are intended for use as structural aggregate within the project boundary do not count toward the total cut volume of materials. DOCUMENTATION Copy of the grading plan. The grading plan must report total cut and fill quantities, total miscellaneous cut/fill, and show that they are within 10% of one another. Calculate and report actual construction earthwork volume for the project. This calculation shall show the following: Actual cut and fill volumes during construction. Actual volume of unused embankment materials (include excess import and excess cut materials) Actual volume of earthwork material imported to the project site. Actual volume of earthwork material exported from the site. Show that: 100% 10% 1 2 APPROACHES & STRATEGIES Use a project design that balances cut and fill volumes. This assumes that cut material from one area of the project site is suitable for use as fill material in another. This may not always be possible. Use soil improvement or stabilization techniques in an effort to avoid removing existing soil. Apply binding agents, additives and other processes to unsuitable soils such that they become suitable for use. This often involves improving their bearing capacity so they can accept overburden or structures. Use in‐situ mitigation techniques to solve problems with unsuitable soils through ground improvement solutions such. Usually this involves forms of compacting, preloading, installed drains (to lower moisture levels) or other similar methods. Improve load bearing capacity of soils by placing geosynthetics over them. This can force the potential bearing capacity failure surface to develop along alternate, higher strength surfaces. Use recycled material from other structures (e.g., crushed recycled concrete material – RCM or reclaimed asphalt pavement – RAP). Use design software and computer aided drawings (CAD) to calculate the design volumes of earthwork to be reported in relation to this credit. Note that these drawings and calculations will be superseded by final volume calculations in the field in the event that they differ. Example: Sample Calculation The South Dakota Department of Transportation Road Design Manual, Chapter 8, contains a detailed example of balancing cut and fill volumes using computer software, titled “Example of Earthwork Quantities with Moisture & Density Control (Undercut)” (p. 8‐6). The example below shows how the calculation can be done by hand for this credit. There are a number of additional sample calculations in the referenced chapter. Variable Description Volume (cy) A Normal cross‐section excavation 54,889 Earthwork Balance MR-3 Greenroads™ Manual v1.5 Materials & Resources A Adjustment for moisture and density 9,233 C Miscellaneous extra excavation (unstable 805 material below undercut) B Normal cross‐section embankment 49426 B Adjustment for moisture and density 11079 D Miscellaneous additional embankment 1490 (unstable material below undercut) D Adjustment for moisture and density 298 A+C Total volume of excavated materials 64927 B+D Total volume of embankment materials 62993 ½ (A+B+C+D) Average total volume of materials 63557 64927 62993 100% . % 10% Project qualifies for 1 point 63557 Example: O’Hare Airport Modernization Program – Phase 1 The Chicago O’Hare Airport Modernization Program (OMP), which was ongoing as of early 2010, made a substantial effort to be more sustainable in their approach to airport design and construction. One of the features of their sustainability efforts is balanced earthwork. Phase 1 moved 15 million cubic yards of soil under a “balanced earthwork plan” that reportedly saved over $100 million by reducing truck trips and fees for dumping at landfills. Figure MR‐3.1: Runway 10C‐28C Paving and Electrical (West): Excavation in Area G5 (Photo Courtesy Chicago O’Hare Moderization Program) MR-3 Earthwork Balance Materials & Resources Greenroads™ Manual v1.5 Figure MR‐1.2: June 2010 Runway 10C‐28C Paving and Electrical (West): Placing and compacting Bit concrete base course on taxiway (Photo Courtesy Chicago O’Hare Moderization Program) Example: Wattstown Business Park Road Extension The Wattstown Business Park Road Extension Project in Coleraine, Ireland implemented a balanced cut and fill strategy that allowed all of the excavated materials to be re‐used on site including excavated topsoils in order to minimize waste and hauling. The vertical alignment of the road was also kept to a minimum in order to minimize earthwork. Figure MR‐3.3: Wattstown Business Park (CEEQUAL,n.d.) Example: Kicking Horse Canyon – British Columbia Ministry of Transportation The Kicking Horse Canyon project near Golden, British Columbia, is a 26 km corridor upgrade that began construction in 2002. One of the project goals was to minimize the need for earthwork along the entire corridor in order to reduce greenhouse gas emissions from hauling trips (and to save money) in accordance with Earthwork Balance MR-3 Greenroads™ Manual v1.5 Materials & Resources objectives of the British Columbia Ministry of Transportation (BCMoT) Climate Action Program. This balanced earthwork program also included addressing safety concerns on the project, which called for improvements to slope stability on roadway excavations as well as avalanche control and rockfall protection in several locations along the corridor’s new alignments. Slope stabilization on Phase 2 of the project was accomplished in some steep areas using 11,000 m3 of high tensile strength steel mesh that also allowed for seeding to grow, which can add stability to upper soil layers (BCMOT, n.d.). The mesh is tied to rock layers below the slope to stabilize the hillside (see Figure 4). Rockfall areas are protected by approximately 20,000 m3 of drapery mesh (BCMOT, n.d.). Excess fill soils were also stockpiled within the corridor for future lanes of highway (BCMOT, 2006). Construction of Phase 3 East ‐ Brake Check to Yoho National Park (underway) is also following a balanced earthwork design program (see Figures MR‐3.6 and MR‐3.7). Figure MR‐3.2: Tecco® high‐strength steel mesh used for slope reinforcement. (BCMOT, 2010) Figure MR‐3.3: West Alignment of Phase 2, Kickinghorse Canyon, showing approximate cut and fill boundary for corridor segment (BCMOT, 2006) MR-3 Earthwork Balance Materials & Resources Greenroads™ Manual v1.5 Figure MR‐3.4: Phase 3 of The Kicking Horse Project: Excavation on north side of the highway (BCMOT, 2010) Figure MR‐3.5: Phase 3 earthwork on east side of highway (BCMOT, 2010) Example: Software Tools for Designers The most straightforward means of balancing earthwork is to design and construct the project such that the volume of cut within the project is equal to the volume of fill. For designers and contractors there are numerous software packages that can provide exact and/or estimated earthwork quantities. The following are examples of software packaging that can be used to achieve balanced cut and fill. Earthwork Balance MR-3 Greenroads™ Manual v1.5 Materials & Resources Trakware Inc.