SECTION TRENCHING, BACKFILL AND COMPACTION

Transcription

1 SECTION TRENCHING, BACKFILL AND COMPACTION PART 1 - GENERAL 1.1 SUMMARY A. Section Includes 1. Native Backfill Material 2. Crushed Stone Bedding 3. Select Backfill Material 4. Shoring and Bracing 5. Excavation 6. Dewatering 7. Bedding 8. Backfill and Compaction B. Related Sections: 1. Section Erosion & Sediment Control 2. Section Crushed Aggregate Base Course 1.2 REFERENCES A. American Society for Testing and Materials (ASTM) 1. ASTM D1557 Testing Methods for Moisture-Density Relations of Soils and Soil-Aggregate Mixtures Using 10-lb (4.54 kg) Rammer and 18- In. (457 mm) Drop 2. ASTM D2922 Testing for Density of Soil and Soil Aggregate in Place by Nuclear Methods (Shallow Depth) 3. ASTM D448 Standard Classification for Sizes of Aggregate for Road & Bridge Construction 1.3 SUBMITTALS A. Submit two (2) copies of the quality control testing, including location where testing was done. Testing results shall include: 1. Materials source testing 2. Background testing 3. Installation testing 4. Additional density testing, if required. 1.4 QUALITY ASSURANCE A. Contractor shall obtain an independent testing laboratory, approved by the Owner, to provide quality control testing. B. Background Testing 1. Perform five (5) moisture/density tests for each major native soil type to determine density of the undisturbed soils. TRENCHING, BACKFILL AND COMPACTION

2 2. Moisture/density testing shall be in accordance with ASTM 1557 (Modified Proctor). C. Installation Testing 1. Moisture/Density testing shall be according to ASTM D2922 (Nuclear Method) 2. Perform at least one (1) moisture/density test for each 100 linear feet of trench at a depth and location directed by Engineer. D. Additional density and gradation testing shall be required when aggregate density does not meet project requirements, there is a change in compaction method, there is a change in the source or quality of aggregate, or as directed by Engineer/Architect. PART 2 PRODUCTS 2.1 NATIVE BACKFILL A. Unless shown otherwise on drawings or ordered in writing by Engineer, material excavated from the trench shall be used for backfilling. B. Excavated material shall be used as backfill provided that such material consists of loam, clay or other materials that are, in the judgment of the Engineer, suitable for backfilling. Backfill material shall be free from frozen materials, organic matter, large stones or boulders, concrete, refuse and litter. 2.2 SELECT BACKFILL MATERIAL A. Select backfill material shall be used as shown on drawings or ordered in writing by Engineer. B. Select backfill material shall conform to the following gradation: ¾-inch (19.0 mm) Crushed Rock ASTM D448-No. 67 SIEVE SIZE % PASSING BY WEIGHT 1-inch 100 3/4-inch /8-inch No No PART 3 EXECUTION 3.1 SHORING AND BRACING A. Provide shoring and bracing materials, such as sheet piling, up rights, stringers and cross braces, in good serviceable condition. Shoring shall be provided as required for safety and by governing authorities. B. Maintain shoring and bracing in trenches and excavations regardless of duration that the excavation will be open. Carry down shoring and bracing as excavation progresses and arrange bracing such that it does not place stress on completed work. TRENCHING, BACKFILL AND COMPACTION

3 C. Exercise care during removal of shoring and bracing materials to prevent collapse or caving of excavation. D. Damages to pipes or structures as a result lack of adequate shoring and bracing or negligence on the part of the Contractor, shall be repaired at the Contractor s expense. 3.2 EXCAVATION A. General 1. No compensation will be given for trenching done in excess of the amount required by the drawings, contract and specifications. 2. Costs associated with trenching, backfilling and compaction of backfill as required by the drawings, contract and specifications shall be included in the unit price bid per foot. B. Removal of Obstructions 1. Remove obstructions mounds of dirt, stone, debris and refuse from within the construction limits 2. Remove and replace, in original condition, the following: signs, culverts, apron endwalls, riprap aprons, and guard posts. 3. Remove concrete and asphalt pavements, curb and gutter, and sidewalk to the maximum trench width at the ground surface or as shown on the drawings. 4. Sawcut pavement, curb and gutter, sidewalk and other surfaces vertically to a minimum depth of 3-inches prior to removal. Remove concrete surfaces to the nearest joint. C. Trenching 1. Excavate trench to sufficient width and depth to allow for proper utility construction at the line and grades shown on drawings. Maximum trench width 2-feet above the top of the pipe shall be the outside diameter of the pipe plus 24- inches. Keep trench walls vertical when possible. The Engineer/Architect may prohibit benching or sloping of the trench walls if the excavation is within permanent pavement, if the excavation would not be contained within the limits of construction or if the excavation would endanger underground utilities or structures. 2. No more than 200-feet of trench shall be open at any given time. 3. Disposed of excess material according to Earth Moving Section DEWATERING A. Contractor shall provide and maintain means and methods necessary to dewater excavations as needed. Dewater to a minimum of 3-feet below excavations. TRENCHING, BACKFILL AND COMPACTION

4 B. Dispose of water in such a way as to prevent runoff and dewatering system discharge from entering the excavation. Convey groundwater to the point of discharge though piping. The use of open ditching or trenching, nor the use of Owner s utilities, shall be permitted. Sediment content of discharge shall not exceed 10 milligrams per liter. C. Maintain dewatering system until backfilling and compaction is complete. D. Obtain all necessary permits from regulatory and governmental agencies governing dewatering. E. Maintain a water supply to any private and public wells affected by the dewatering operation. Any damage caused to private wells as a result of dewatering shall be corrected. 3.4 BEDDING A. Bedding material for sewers 18-inches in diameter and smaller shall conform to: SIEVE SIZE % PASSING BY WEIGHT 1-inch 100 3/4-inch /8-inch No No B. Bedding material for sewers 18-inches in diameter and larger shall conform to: ¾-inch (19.0 mm) Crushed Rock ASTM D448-No. 67 SIEVE SIZE % PASSING BY WEIGHT 1-inch 100 3/4-inch /8-inch No No C. Bedding material for water mains and force mains shall consist of hard, durable particles ranging in size from fine to course in a substantially uniform combination. Material shall be free from organic matter, refuse, litter and balls or lumps of clay and shall conform to the gradation requirements detailed below: SIEVE SIZE % PASSING BY WEIGHT 1-inch 100 No No D. Spread bedding material over the bottom of the trench and solidly compacted such that after the pipe has been placed, imbedded to grade and aligned, there is a minimum of 4- inches of bedding material beneath the pipe barrel and a minimum of 3-inches of bedding material beneath the bell of the pipe. Fill excess depth resulting from excavation deeper than 6-inches beneath the pipe barrel with crushed stone. TRENCHING, BACKFILL AND COMPACTION

5 E. Class C Bedding 1. Place bedding material up to the spring line of the pipe making sure that the lower quadrants of the pipe are firmly bedding and supported. F. Class B Bedding 1. Place and compact bedding material to a level 12-inches above the top of pipe. G. Provide an additional 3-inches of bedding material beneath the required 4-inches of bedding material where wet trench conditions exist. Extra excavation, furnishing, and installation of this extra stone shall be included in the unit price bid for the pipe line. 3.5 BACKFILL AND COMPACTION A. Backfill trench with excavated material in layers not more than 12-inches thick unless select backfill material is shown on drawings or ordered in writing by Engineer/Architect. B. Backfill trench to last pipe joint, not to exceed 10-feet, at the end of each work day. C. Warranty 1. Settlement or damage as a result of settlement that occurs during the specified warranty period shall be repaired at the Contractor s expense. Owner shall determine failed areas and the extent of repair shall be agreed upon prior to the repair being made. 2. Repair of settled areas shall required removal of existing material and recompaction or flushing of the trench, as agreed upon with the Owner. 3. Contractor shall provide an additional one (1) year warranty for failed areas. - END OF SECTION - TRENCHING, BACKFILL AND COMPACTION

6 SECTION EROSION AND SEDIMENTATION CONTROLS PART 1 - GENERAL 1.1 SUMMARY A. Section Includes 1. Submittals 2. Erosion control plan. 3. Erosion control materials. 4. Grading and earthwork 5. Drainage. 6. Tracking control. 7. Maintenance. B. Related Sections 1. Section Closeout Procedures 2. Section Site Clearing 3. Section Earth Moving 4. Section Trenching, Backfill, and Compaction 1.2 REFERENCES A. Wisconsin Department of Natural Resources Technical Standards for Construction Site Erosion & Sediment Control (Technical Standards). B. Erosion Control Produce Acceptability List ( PAL ), current version as published by the Wisconsin Department of Transportation. C. Standard Specifications for Highway Construction, current version as published by the Wisconsin Department of Transportation. SUBMITTALS A. Contractor shall submit to the Engineer, shop drawings for erosion control features as indicated on Drawings. 1.3 EROSION CONTROL PLAN A. The Engineer has prepared an erosion control plan included in these documents for the project. The erosion control plan is in accordance with Chapters NR 151, NR 216, and COMM 60, Wis. Adm. Code. Contractor shall provide additional or alternate erosion control measures as needed due to the contractors means and methods throughout all phases of construction. B. Contractor shall comply with all requirements of the erosion control plan, and the requirements of the General Permit to Discharge under the Wisconsin Pollutant Discharge Elimination System: n/construction_permit_s pdf). EROSION AND SEDIMENTATION CONTROLS

7 If applicable, the project specific WPDES Construction Site Stormwater Discharge Permit for Erosion Control shall supersede the General Permit. C. Erosion control and storm water management practices shall be installed and maintained in accordance with the WDNR approved Technical Standards (or equivalent). PART 2 PRODUCTS 2.1 MATERIALS A. General 1. Erosion mats, soil stabilizers, and tackifiers shall be listed on the PAL or the Technical Standards 2. When the design or contract includes permanent erosion control or stormwater control features, the contractor may employ these items to control erosion and stormwater during construction activities. However, these features shall be fully cleaned and restored to the original design providing full function for the intended permanent use prior to acceptance of the work. B. Straw Bale Barriers: Rectangular bales of hay or straw, tightly bound with twine, not wire. Anchor stakes shall be T" or "U" steel posts, or hardwood, 2.0 by 2.0 inches nominal. Rebar shall not be used to anchor bales. C. Silt Fence: Fence fabric, support posts and support cord shall comply with the requirements of the Wisconsin DNR Technical Standards. D. Erosion Mat: Erosion control mat shall comply with the Wisconsin DNR Technical standards and the applicable Class and Type as defined by the PAL. E. Staples: Use biodegradable staples in accordance with manufacturer s recommendations for materials being anchored. Wood and metal staples are not allowed. F. Riprap: Riprap shall be the class specified and shall conform to the Standard Specifications for Highway Construction Section G. Tracking Pad Stone: The aggregate for tracking pads shall be 3 to 6 inch clear or washed stone. All materials shall be retained on a 3-inch sieve. H. Soil Stabilizers: Soil stabilizers shall be non-asphalt-based products of the type specified, and meeting the requirements of the PAL. I. Soil Tackifiers: Soil tackifiers shall be non-asphalt based products of the type specified, and meeting the requirements of the PAL. J. Polymers: Polymers used to settle suspended soils shall meet the requirements of the Technical Standards. K. Anionic Polyacrylamide: Water soluble anionic polyacrylamide (PAM) used as temporary soil binding agents to reduce erosion shall meet the requirements of the Technical Standards. EROSION AND SEDIMENTATION CONTROLS

8 L. Geotextile Fabric: Geotextile fabric used for inlet protection shall be Type FF geotextile fabric meeting the requirements of the PAL. M. Dewatering: All dewatering shall be done in accordance with the Technical Standards. N. Ditch Check: Ditch checks shall be stone or logs conforming to the Technical Standards. O. Dust Control: Dust control measures shall be done in accordance with the Technical Standards. PART 3 EXECUTION 3.1 GENERAL A. Install and maintain erosion control measures as required by the erosion control plan throughout all phases of the project. Notify Engineer of modifications to the erosion control plan as directed by Contractor s means and methods, construction phasing or differing site conditions. B. Contractor shall provide all erosion control measures necessary to prevent and manage polluted runoff from the construction site and discharge of sediment onto adjacent property, into storm sewers or waters of the state. C. Perform all work in accordance with manufacturer s instruction when these specifications do not specify a higher requirement. 3.2 GRADING AND EARTHWORK A. Install temporary or permanent erosion control measures applicable to each phase or land disturbance prior to commencing on that phase. B. Clear only those areas designated for the placement of improvements or earthwork before placement of the final cover. Perform stripping of vegetation, grading, excavation or other land disturbing activities in phases to minimize exposure of bare soil. Do not clear the site of topsoil, trees, and other natural ground covers before the commencement of construction. Retain natural vegetation and protect until the final ground cover is placed. C. Do not stock pile soil within 25 feet of any roadway, parking lot, paved area or drainage structure/channel. Provide temporary stabilization and erosion control measures on disturbed areas and soil stockpiles which will remain for a period of more than 7 consecutive calendar days. D. Remove surplus excavation materials from the site immediately after rough grading. 3.3 DRAINAGE A. Divert roof drainage and runoff from all undisturbed areas upslope of the site around disturbed areas, where possible. Minimize runoff on exposed soil. Provide measures to remove sediment and debris. EROSION AND SEDIMENTATION CONTROLS

9 B. Convey clean or treated runoff to the nearest adequate storm water facility. Do not discharge water in a manner that will cause erosion or sedimentation of the site or receiving storm water facility. C. Protect storm sewer inlets and catch basins with inlet protection devices. D. Provide ditch checks in swales or ditches to reduce the velocity of water in the channel. E. Dewatering discharge shall be routed to a sedimentation basin or sedimentation vessel to reduce the discharge of sediments to meet the requirements of NR 151. Do not discharge water in a manner that will cause erosion or sedimentation of the site or receiving storm water facility. 3.4 TRACKING CONTROL A. Construct and maintain tracking pads in accordance with the Technical Standards. Provide each entrance to the site with a stone tracking pad at least 50 feet in length with a minimum thickness of 12 inches. The tracking pad shall be the full width of the egress. Inspect tracking pad on a daily basis and replace aggregate when no longer effective. B. If applicable, wash water shall be discharged to sedimentation basins, sedimentation vessels, or other such control areas. Untreated wash water shall not be routed to storm sewers or waters of the state. 3.5 MAINTENANCE A. Contractor shall inspect all erosion control measures within 24 hours of the end of each rainfall event that exceeds 0.25 inches, or daily during periods of prolonged rainfall, or weekly during periods without rainfall. Immediately repair and/or replace any and all damaged, failed, or inadequate erosion control measures. B. Re-apply soil stabilizers, tackifiers, polymers and anionic polyacrylamides as needed to prevent erosion of exposed soil. C. Maintain records of all inspections and any remedial actions taken on-site. Records must be made available to state and local officials upon request. D. Remove any sediment reaching a public or private roadway, parking lot, sidewalk, or other pavement. Do not remove tracked sediments by flushing. Completely remove any accumulations not requiring immediate attention at least once daily at the end of the workday. E. Frequently dispose of all waste and unused construction materials in licensed solid waste or wastewater facilities. Do not bury, dump, or discharge, any garbage, debris, cleaning wastes, toxic materials, or hazardous materials on the site, on the land surface or in detention basins, or otherwise allow materials to be carried off the site by runoff onto adjacent lands or into receiving waters or storm sewer systems. - END OF SECTION - EROSION AND SEDIMENTATION CONTROLS