00405.02 329 PART 00400 - DRAINAGE AND SEWERS
Description
00405.00Scope - This Work consists of excavating trenches, constructing Trench Foundations, and
placing bedding, Pipe Zone Material and backfill.
00405.01General - Excavate, backfill and dispose of excess excavated materials in connection with
minor Structures and conduits such as subsurface drain, culvert, siphon, irrigation and sewer pipe of nominal inside diameters not exceeding 72 inches. Perform excavation for major Structures and conduits with a nominal inside diameter or width greater than 72 inches according to Section 00510.
Trench Excavation does not include earthwork covered under any other Section, or any earthwork that may be specifically included and provided for other Pay Items of the Contract. Dispose of excess excavated materials and perform other matters not covered in this Section according to Section 00330.
00405.02Definitions :
Boulder Excavation - The removal, without drilling, blasting or splitting, of masses of Rock having one or more dimensions of 3 feet or greater. Common Excavation - The removal of all material not classified as Rock Excavation.
Flexible Pipe - For the purpose of these Specifications, potable water pipes and pipes constructed of corrugated metal, PVC, and polyethylene are considered F lexible Pipes.
Pipe Bedding - Furnishing, placing and compacting specified Materials on the Trench Foundation so as to uniformly support the barrel of the pipe.
Pipe Zone - The area from the top of the bedding to a point 8 inches, minimum, above the top outside of the pipe barrel for the full width of the trench.
Rigid Pipe - For the purpose of these Specifications, pipes constructed of concrete and ductile iron are considered R igid Pipes. Rock Excavation - Excavation of solid ledge Rock that, in the opinion of the Engineer, requires for its removal drilling and blasting, wedging, sledging, barring, or breaking up with power -operated tools. The term "Rock Excavation" indicates a method of removal and not a geological formation. Surface Removal - The removal of surface material such as Topsoil , sod, Pavement , sidewalks, or Gravel, that requires different Equipment or methods than those used for Trench Excavation.
Trench Backfill - Furnishing, placing, and compacting Material other than CLSM in the trench, between the top of the Pipe Zone Material and the bottom of the Pavement Base Aggregate, ground surface or surface M aterial. Trench Excavation - The removal of all material encountered in the trench to the depths as shown or as directed. Trench Excavation is classified as either common or Rock Excavation.
Trench Foundation - The bottom of the trench on which the Pipe Bedding is to lie and whic h provides support for the pipe. 00405.03 330
00405.03Lines, Grades, and Cross Sections - Excavate trenches to the lines, depths, grades and
Cross Sections as shown or as established. Variations will be allowed only when necessary to ensure firm foundations and when such variations will not be detrimental to the Work .
Materials
00405.10General - Materials may be native or imported, as specified
00405.11Trench Foundation - Where additional excavation is required due to groundwater or other
unstable conditions so that the native material cannot support the pipe, furnish one of the following Materials for T rench Foundation:
• Selected general backfill conforming to 00330.13. • Selected granular backfill conforming to 00330.14. • Selected stone backfill conforming to 00330.15. • Other approved M aterial .
00405.12Bedding - If groundwater is present in the bedding zone, use 3/4" - 0 Aggregate bedding
If groundwater is not present, and unless otherwise specified, furnish one of the following Materials for bedding the pipe:
• Commercially available 3/4" - 0 Aggregate. • Reasonably well -graded, from maximum size to dust, S and with 100 percent passing the 3/8 inch sieve. • Commercially available 3/8" - 0 or No. 10 - 0 Sand. CLSM conforming to Section 00442.
00405.13Pipe Zone Material - For Flexible Pipes, backfill the Pipe Zone with bedding M aterial as
described in 00405.12. For Rigid Pipes, unless otherwise directed, furnish either:
• 1" - 0 or 3/4" - 0 base Aggregate conforming to 02630.10, or • Commercially available 1" - 0 or 3/4" - 0 Aggregate.
00405.14Trench Backfill - Furnish the following Materials where shown or required:
the characteristics required for the specific surface loading or other criteria of the backfill zone.
requirements of Section 00641. Designated size shall be 1" - 0 or 3/4" - 0.
maximum dimension shall be 3 inches.
00405.15Quality Control - Provide quality control according to Section 00165
00405.41 331 Labor
00405.30Quality Control Personnel - Provide technicians having CEBT, CAgT, and CDT technical
certifications.
Construction
00405.40General - Perform all excavation and backfilling according to the following requirements:
existing ground has been measured and the measurements have been approved by the Engineer.
streambeds. Comply with 00290.30(a). Restore the streambed according to 00405.46(f).
according to 00330.42(c)(6) and as shown , before excavating trenches.
00405.41Trench Excavation - Excavate trenches according to the following:
excavation method, unless otherwise directed. Do not disturb the adjoining Pavement more than necessary.
resurfacing shall be completed within 800 feet of the open trench limit.
install the pipe in a safe manner, but not less than 24 inches. In all cases, make trenches of sufficient width to allow for shoring and to permit proper jointing of the pipe and backfilling of Material along the sides of the pipe. Refer to the Standard Drawings for minimum trench widths for various diameter pipes. Make excavations for manholes and other Structures wide enough to provide a minimum of 12 inches between the Structure surface and the sides of the excavation. Keep the top of the trench within Right -of-Way or permit limits.
allowance for pipe thickness, Pipe Bedding and foundation stabilization. Place Pipe Bedding on a firm, undisturbed, foundation, true to grade. If the trench is excavated below grade without authorization, restore to grade with Material of the type specified for Pipe Bedding at no additional cost to the Agency. Place the M aterial over the full width of the trench, in compacted layers not exceeding 6 inches.
that it does not create a hazard to pedestrian or vehicular traffic, or interfere with the function of existing drainage facilities.
Make arrangements for and dispose of all excess material not required elsewhere on the Project in an approved manner, at no additional cost to the Agency, and according to 00330.41(a)(4).
at all times. P rovide safe working conditions in the trench and protect the Work , existing property, utilities, Pavement , and the public. The method of protection shall be according to the Contractor's 00405.42 332 design. The Contractor may elect to use any combination of shoring, overbreak, tunneling, boring, sliding trench shields or other methods of accomplishing the Work , provided the method meets with the approval of the Engineer and complies with all applicable local, state, and federal safety codes.
Be responsible for damages resulting from improper removal of shoring or from failure to shore.
and other facilities as necessary to construct the trench according to 00310.41(c).
00405.42Rock Excavation - Where Rock Excavation as defined in this Section is required, remove
the Rock to provide the minimum clearances shown on the Standard Drawings. Excavate and remove the overburden and expose the Roc k to allow the Engineer to measure the Rock prior to removal. If using explosives, comply with the requirements of 00170.94. Prior to blasting, obtain the approval of the Engineer and the appropriate permits. Provide all tools and devices required for l oading and using explosives, blasting caps and accessories. When blasting Rock in trenches, cover the area to be shot with blasting mats or other protective Material to prevent the scattering of Rock fragments outside of the excavation.
00405.43Dewatering - Promptly remove and dispose of all water entering the trench during the time
the trench is being prepared for the pipe laying, during the laying of the pipe and until the backfill at the Pipe Zone has been completed. Dispose of the water in an approved manner without damage to adjacent property.
Control groundwater to prevent softening of the bottom of excavations or formation of "quick" conditions or "boils". Design and operate dewatering systems to prevent removal of th e natural Soils and so that the groundwater level outside the excavation is not reduced to the extent that would damage or endanger adjacent Structures or property.
When dewatering near a river, lake, or stream, conform to the requirements of 00290.30(a) and Section 00280. When the presence of water or other conditions in the excavated area would be detrimental to the purpose of the Work , obtain approval of the Engineer for the temporary measures required to correct or care for the condition. If water or other conditions encountered require permanent correction or care not anticipated by the Contract and not due to the Contractor's neglect or method of operation, perform the Work according to 00140.60.
00405.44Trench Foundation - Make the full length and width of completed trench bottoms firm. Do
not place bedding material before the T rench Foundation is inspected and approved. If bell and spigot pipe is used, recess the trench bottom to accommodate the bell.
When, in the judgment of the Engineer, the existing material in the bottom of the trench is unsuitable for supporting the pipe, excavate below grade, as directed. Replace the excavated material with imported Trench Foundation Material conforming to 00405.11. Place the T rench Foundation Material in 6 inch layers and compact according to 00330.43 except compact selected stone backfill material in 12 inch layers. Bring the Trench Foundation Material to the elevation established.
00405.45Pipe Bedding - Spread the bedding smoothly to the proper grade so that the pipe is
uniformly supported along the barrel. Excavate bell holes at each joint to permit proper assembly and inspection of the joint. Bedding under the pipe shall provide a firm, unyielding support along the entire pipe length.
00405.46Backfilling - Backfill with Material conforming to 00405.13 and the details shown, or as
directed. 00405.46 333
• The foundation has been prepared, if required. • The bedding has been prepared. • The drainage facilities and fittings are installed. • The installation has been inspected and approved.
Thoroughly tamp and compact all Trench Backfill with machine or pneumatic operated tampers of a size and type that will obtain the required density. When fill is to the top of the pipe, compact the Trench Backfill in a manner to avoid damage to the installed pipe. Test for density according to 00330.43. Backfill either to the top of the trench, the surrounding ground level, or the upper limit of excavation, as directed. Dispose of excess excavated material not used in backfill Work according to Section 00330.
in a manner that equalizes pressure on the Structure and minimizes stress. Before placing backfill Material , condition, aerate, or wet the Material so that the moisture content of each layer is within minus 4 percent to plus 2 percent of optimum moisture content.
As required under the haunches of pipe and in areas not accessible to mechanical tampers or to testing, compact with hand methods to ensure intimate contact between the backfill Material and the pipe or Structure . Place backfill M aterial between corrugati ons when the pipe product is manufactured with external corrugations. Provide thorough compaction. Ponding or jetting is not allowed within the Pipe Zone.
Zone, except where in conflict with the requirements of 00405.46(b):
The Engineer may sample excavated Material to determine the suitability of t he Class A M aterial for use as backfill. If the M aterial is approved, the Contractor may elect to use the Material in place of the specified backfill. Prevent excavated M aterial from becoming saturated beyond the critical moisture limits, and replace any saturated Class A Material with Class B, C, or D M aterial , as specified, at no additional cost to the Agency.
Do not allow the backfill to free -fall into the trench until at least 3 feet of cover is provided over the top of the pipe. Modify the method of compaction as necessary to protect the pipe.
Compact each layer of Trench Backfill Material within the Roadway and Shoulders, and within a 2V:1H Slope line projected from each Subgrade Shoulder , to not less than 95 percent of maximum density. Compact all other T rench Backfill Material to not less than 90 percent of maximum density.
Determine the maximum density by AASHTO T 99. If the spec ified compaction is not obtained, the Contractor may be required to use a modified compaction procedure or reduce the thickness of Lifts. If approved M aterials meeting the Specifications cannot be compacted to the required density regardless of compactive effort or method, the Engineer may reduce the required density 00405.48 334 or direct that alternate Materials be used. Do not proceed with excavation and pipe laying operations until the backfill can be compacted to the satisfaction of the Engineer.
If the M aterial is not density testable, the Engineer will observe each layer for deflection or reaction under the compaction Equipment to verify that no soft or pumping areas remain. Compact until there is no perceptible deflection under the compaction Equipment . When the backfilling is complete, finish the surface area as specified. In paved or graveled areas, maintain the surface of the T rench Backfill level with the existing grade with 3/4" - 0 crushed Aggregate Material , or asphalt concrete if directed, until final Pavement replacement is complete and accepted.
is to be used as a temporary Surfacing, backfill the CLSM to the top of the trench and strike it off to provide a smooth surface. If the CLSM is not to be used as a temporary Surfacing , backfill the CLSM up to the bottom of the proposed resurfacing. No compaction of CLSM is allowed. Use ste el plates to protect the CLSM from traffic a minimum of 24 hours. After 24 hours, the CLSM may be paved, or opened to traffic until permanent surface restoration is completed, if it has hardened sufficiently to prevent rutting.
lateral limits. Ponding or jetting will be allowed outside Roadbeds when approved by the Engineer in writing.
Use Class C or D Trench Backfi ll Material at no additional cost to the Agency. Provide drainage at the bottom of the trench to remove water from the jetting operation. Compact to the density and deflection requirements of 00405.46(c). Furnish Equipment that provides a minimum gauge pressure of 35 psi at the discharge nozzle. Use a Rigid Pipe that will reach within 1 foot of the bottom of the backfill. Insert the pipe at intervals not exceeding 4 feet throughout the entire width and length of the T rench Backfill.
shall be capable of carrying at least an MS -18 loading. Place steel plates with a minimum of 12 inches bearing on all sides of a cut. Anchor steel plates to minimize shifting. Shim the edges of all steel plates with cold mix asphalt.
of the Work :
• Restore the streambed to its former condition of resistance to scour. • Remove all matter that has come into the stream due to the Contractor's activities.
00405.48Surface Removal :
on which Topsoil exists, remove the Topsoil to a minimum 12 -inch depth and place the Material in a stockpile. Do not mix the Topsoil with other excavated material. Af ter the trench has been backfilled, replace the Topsoil .
In lieu of stockpiling the Topsoil , approved imported Topsoil may be substituted, to a depth specified or approved, at no additional cost to the Agency.
00405.81 335 Maintain the finished grade of the Topsoil level with the area adjacent to the trench until Final Acceptance by the Engineer, and repair damage to adjacent Topsoil caused by the Contractor's operations. Remove all Rock , Gravel, Clay and other foreign materials from the surface. Regrade and add Top soil as required.
and sidewalks, regardless of thickness. In bituminous Pavement , when no Pavement overlay will occur, saw -cut the Pavement along each edge of the area to be removed. When Roadways will receive a Pavement overlay as part of the Project or following trench resurfacing, bituminous Pavement to be removed may be cut by wheel cutter, jack hammer, or other approved methods.
Upon completion of backfill and just prior to Pavement resurfacing, saw the Surfacing on both sides of the trench a minimum of 6 inches wider than each top of the trench. In areas of any undermined or damaged Surfacing , re-saw to a width outside these areas. When saw -cutting, follow lines parallel to the pipe centerline.
Where the width changes in areas of asphalt Pavement resurfacing, cut the transition between the different widths at 45 degrees. When the pipeline changes direction, or there is a connecting pipeline that requires the sawcut alignment to change at an angle greater than 60 degrees, make a minimum 24-inch transition sawcut. If there is damaged or undermined Surfacing at the transition point, make the transition sawcut beyond the damaged or undermined Surfacing. Make the transition sawcut angle half the angle change in th e direction of the pipeline or connecting line. If the asphalt Surfacing is to be overlaid, the second sawcut will only be required to firm Subgrade .
A second sawcut for concrete sidewalks, driveways and Pavements will not be required unless needed to reach firm Subgrade .
Remove and dispose of Pavement lying within the limits of the cuts and from any adjoining areas damaged by the cutting and removal o perations according to Section 00310.
Measurement
00405.80Measurement - Except for Rock Excavation, Boulder Excavation, and Trench Foundation,
no measurement of quantities will be made for Work performed under this Section.
Imported Topsoil will be m easured according to 01040.80.
00405.81Rock Excavation and Boulder Excavation - The quantities of Rock Excavation and
Boulder Excavation will be measured as follows:
be of the actual dimensions of Rock removed within the following limits:
• Length - Length will be the horizontal distance measured along the centerline of the trench excluding manholes, inlets, and other Structures. • Width - Width will be the width of the Rock removed but will not be greater than the outside diameter of the pipe bell plus 12 inches.
• Depth - Depth will be measured at 30-foot intervals, or as specified, along the centerline of the trench. The depth will not be greater than 6 inches below the outside bell of the pipe.
00405.82 336 Rock Excavation for manholes, inlets, and other Structures will be computed from the Rock excavated to a depth 6 inches below the bottom of the Structure and an area within a line parallel with, and 12 inches outside of, the actual dimensions of the manhole, inlet, or Structure .
No separate measurement will be made for the following:
• Soft or disintegrated Rock . • Hardpan or cemented Gravel that can be removed with a hand pick or power -operated excavator or shovel. • Loose, shaken, or previously blasted Rock or broken stone in Rock fillings or elsewhere. • Rock outside of the minimum limits of measurement allowed, which may fall into the excavation.
Measurement will be made in the field by the Engineer after removal of each Boulder from the excavation but prior to removal from the site. Each Boulder removed will be measured for length, width, and height. The volume of each Boulder will be determined as the product of 85 percent of each of the three measured dimensions.
00405.82Trench Foundation - The quantities of unsuitable T rench Foundation will be measured on
either the weight basis or the volume basis as follows:
• Weight Basis - Trench Foundation will be measured on the weight basis. The quantity of replacement foundation Material will be b ased on weigh tickets from scales meeting the requirements of Section 00190. Present weigh tickets to the Engineer for signature on the Day the Material is delivered.
• Volume Basis - Trench Foundation will be measured on the volume basis, computed using t he following dimensions:
• Length - Length will be the horizontal distance measured along the centerline of the trench. Measurement will be continuous through manhole or Structure locations.
• Width - Width will be the nominal inside diameter of the pipe pl us two times dimension "B" from "Table A" shown on the Standard Drawings .
• Depth - Depth will be the vertical distance from the top of the underlying surface (following excavation of Unsuitable Material ) to the bottom of the Pipe Bedding. The depth will be measured at intervals of 30 feet, or as specified, along the centerline of the trench and the average depth between points will be used for the volume computation.
00405.90 337 Payment
00405.90Payment - The accepted quantities of Rock Excavation, Boulder Excavation, and T rench
Foundation will be paid for at the Contract unit price, per unit of measurement, for the following items: Pay Item Unit of Measurement
Item (c) includes removal of Unsuitable Material and replacement as necessary to provide a stable foundation for the pipe.
Payment will be payment in full for furnishing and placing all Materials, and for furnishing all Equipment , labor, and Incidentals necessary to complete the Work as specified. Imported Topsoil will be paid for according to 01040.90.
No separate or additional payment will be made for:
• Trench Excavation • Trench Backfill • sawcutting • trench protection • Pipe Bedding • Pipe Zone Material • dewatering
When the Contract Schedule of Items does not indicate payment for Work performed under this Section, no separate or additional payment will be made. Payment will be included in payment made for the appropriate items under which this Work is required.