Section_J_-_Att_No__001_SOW.pdf

Marin Headlands

Marin Headlands Forced Main Repair

Golden Gate National Recreation Area

Objective

Golden Gate National Recreation Area (GGNRA) desires to solicit a request for quote to qualified vendors to repair broken 6-inch PVC forced main under Bunker Road in Sausalito, CA.

Background

The Marin Headlands and Fort Baker have a robust community of park visitors, non-profits, park partners, residences, concessionaires, and housing for 134 NPS staff members and interns. Over 4 million visitors per year visit the Marin Headlands. Sewage from the Marin Headlands is pumped via forced main through the

Baker Barry tunnel to Fort Baker. A break in the pipe has been discovered at a double cleanout, approximately four feet under Bunker Road. As-Builts from the installation note that no ground water was discovered in the area during the install.

Project Description

The contractor will be responsible for all equipment, materials, and labor necessary for asphalt cutting, trenching, removal of broken pipe, pipe repair, backfill and compaction, asphalt repair. Contractor is also responsible for haul off and disposal of all spoils and materials. Additionally, contractor will be responsible for pumping sewage from downstream pump station to upstream pump station, bypassing the area of repair.

Contractor will be responsible for traffic control during the duration of the project.

Products and Execution

Bedding Materials

Class II Well graded crushed stone or crushed gravel meeting the requirements of ASTM C33, Gradation 67

(3/4 inch to No. 4)

Class III Selected soil free from clods and stones greater than 3/4 inch in maximum dimension and free of all unsuitable materials as defined below.

Unsuitable Materials-Expansive materials and material that contains debris, roots, organics, or frozen materials, stone or concrete having a maximum dimension larger than four (4) inches, or materials that are unsuitable for providing stable slopes, fill, backfill, foundation or sub-grade material for structures or surfaces shall be classified as unsuitable. Otherwise, suitable material which is unsuitable due to excess moisture content will not be classified as unsuitable unless it cannot be dried by manipulation, aeration, or blending with other materials satisfactorily to meet moisture limits for proper compaction

Removal of Cleared and Unsuitable Material-Materials from the clearing operations shall be the responsibility of the Contractor and shall be removed from the site of the work and disposed of in a manner satisfactory to the Government, and in accordance with state and local regulations. During the process of clearing or trench excavation, soils such as peat, soft clay, quicksand, or other materials which are unsuitable for bedding may be encountered. These materials shall be removed from the site and disposed of by the Contractor. If removal of unsuitable materials results in excavation below the grade required for bedding, the area shall be backfilled to grade with suitable bedding materials complying with the provisions of applicable specifications for the work being constructed.

Pavement Cutting- Where trench excavation requires the removal of asphalt pavement, the pavement shall be cut in a straight line parallel to the direction of trench excavation. The cut shall be made with a spade bit air hammer, by sawing, or with similar approved equipment to obtain a straight, square, and clean break. Ripping the asphalt will not be allowed. The pavement cuts shall be at least one foot wider in each direction than the anticipated limits of the open trench. No excavation in paved areas will be started until after the pavement has been cut. The paving material obtained from excavations in paved areas shall be disposed of by the Contractor.

All areas where pavement is removed shall be restored as specified herein. Temporary surfaces shall be placed until the permanent repair can be made. All surface improvements consisting of, but not limited to, pavements, ditches, and culverts damaged by the Contractor during the progress of work shall be replaced at Contractor expense. The construction of the repairs shall result in work equal to or better than that which existed before the damage was done.

Excavation-Excavation for pipe shall be by open trenches. The trench shall be excavated using conventional methods. The banks of the trench shall be kept as nearly vertical as soil conditions will permit, but shall not exceed the angle of repose of the soil. Vertical trench walls shall be used in the pipe zone.

Sheeting Bracing and Shoring-Where necessary, excavation shall be braced and sheeted to provide complete safety to persons working in or around the trenches and shall comply with applicable federal (OSHA), state, and local laws and ordinances. The Contractor shall be fully responsible for sufficiency and adequacy of bracing excavations with respect to work under construction and to adjacent utility lines. If sheeting is used to support the excavated trench, the sheeting shall be removed by the Contractor. Remove sheeting and shoring as excavations are backfilled in a manner to protect the material, construction, and compaction. No such sheeting will be permitted to remain in the trench.

Drainage-Maintain the excavation and site free from water and sewage throughout the work. Remove any sewage backflowing into the excavation with a vac truck. Sewage and water pumped from the excavation must be hauled offsite and disposed of at a legal disposal site.

Trench Width-Alignment of trenches shall be carefully controlled so that the pipe will be laid with adequate space for compaction of backfill between the pipe and trench walls. All excavation shall be of sufficient width to provide ample room for proper joining of pipe and fittings. Minimum trench width shall be twelve (12) inches plus pipe OD. Maximum trench width will be restricted to pipe diameter plus two (2) feet unless otherwise approved by the Government.

Bedding Preparation-The bottom of the trenches shall be accurately graded to provide uniform bearing and support throughout the pipe length. Excess loading of the bell will not be permitted under any circumstances.

Dig bell holes and depressions for joints after trench bottom has been graded. Bell holes and depressions shall be only of such length, depth, and width as required for properly making the particular type of joint. The use of earth mounds for bedding the pipe will not be permitted. All sharp stones, trash, and other materials which may damage the pipe or interfere with the proper bedding of the pipe and the placement and compaction of the backfill shall be removed from the trench. The soil in the bottom of the trench shall be loose, and at the optimum moisture, so that uniform bedding and compaction around the pipe is easily obtainable. Should any material be encountered which would prevent the obtaining of suitable bedding, e.g., wet, unstable, etc., the trench shall be over-excavated to a depth of six (6) inches minimum below the outside bottom of the conduit, except at points of rock and earth transitions, at which point the rock shall be excavated to a minimum of twelve (12) inches below the outside bottom of the flexible conduit. Backfill any over-excavation, required or inadvertent, with materials equivalent to and compacted as specified for haunching materials according to these specifications. If the trench bottom becomes unstable due to the entrance of water into the excavation, the saturated soil shall be removed and suitable bedding placed and compacted to pipe grade.

Placing Bedding Material-The bottom of the trench must be dry or well-drained before bedding and backfilling is started. Place material below and around the pipe by hand to prevent damage or displacement of the pipe.

Place in lifts not to exceed three (3) inches in compacted thickness in the pipe zone. Flexible pipe is used, and special care shall be employed in the pipe bedding.

Backfill and Compaction-The Contractor shall proceed with backfilling as soon as practicable, but not until

Work is inspected by the Government. Compaction or consolidation shall follow as soon after the placing as is practical. Backfill material shall consist of material which, after placement and compaction, will result in a stabilized soil condition capable of supporting the normal traffic and use loads that may be encountered.

Normally the backfill material will be obtained from the soil banks accumulated from the trench excavation, though it is expected that this soil will be saturated and unable to meet the compaction requirements. The backfill materials shall be free of vegetation, lumps, trash, lumber, and other unsuitable or objectionable materials. The backfill placed within twelve (12) inches of the pipe (the pipe zone), shall be a Class II or III material and shall not contain any sharp rocks, stones larger than three-fourths (3/4) inch in diameter, or other objects that might damage the pipe. In no event shall rocks or other objects whose largest dimension exceeds four (4) inches be used as backfill material. All such material shall be removed from the work area and disposed of in a manner acceptable to the Government. Moisture control of fill will be required to facilitate achieving acceptable soil densities.

Pipe Zone Compaction-After the pipeline has been installed, suitable backfill material shall be hand-placed in up to three (3) inch lifts to the pipe centerline (springline) and hand-tamped and compacted to provide firm uniform support for the pipe. Take care to ensure that sufficient material as been worked under the haunch of the pipe to provide adequate side support. With rigid pipe, if care has been taken to shape the bedding material to the curvature of the pipe, only one stage of placement will be required to bring the haunching material to the springline. Compact haunching material to a minimum of 95% Standard Proctor Density. Additional backfill shall then be hand-placed and hand-compacted in three (3) inch lifts to provide at least six (6) inches of suitable cover over the top of the pipe before any material is placed with machinery. Take care to avoid contact between the pipe and compaction equipment to avoid damage or displacement. Compaction of initial backfill and backfill materials shall be done in such a way that the sufficient backfill has been placed to ensure that such compaction equipment will not have a damaging effect on the pipe or its installation. Any damage resulting from the backfilling or compaction of the backfill shall be repaired by the Contractor in a timely manner. At all times precautions should be taken to prevent flotation of the pipeline due to entry of water into the trench. Compaction in the pipe zone shall be to 95% Standard Proctor unless authorized or noted on the approved plans. Upper Trench Compaction The degree of upper trench compaction required for the backfill will depend upon the location of the pipeline and the material used in the backfill. Under roads and other potential driving surfaces, minimum compaction through the entire depth shall be 95% of maximum dry density. Elsewhere within public rights-of-way the minimum compaction shall be at least 92%. In general, backfill shall be mechanically compacted by means of tamping rollers, sheep foot rollers, pneumatic tire rollers, vibrating rollers, or other mechanical tampers which are appropriate for the material being compacted.

Compaction by jetting or flooding shall not be permitted. The trench shall be filled to provide a minimum of three (3) feet of cover over the pipe before rolling equipment is used and 50 inches before utilizing a hydrohammer during compaction.

Surface Restoration-Prior to replacing asphalt on properly compacted backfill, square up any ragged edges of adjoining pavement. Such cutting shall be done in accordance with “Pavement Cutting” paragraph above.

Apply MC-70 or other approved price coat to Class 6 roadbase on top and against sides where pavement is to be placed, in accordance with manufacture’s recommendations. Lay two 2” mats of hot bituminous asphalt to area and compact to 95% of Marshal Density. Place patching material around the edges and work inward.

Unless otherwise specified herein, materials and construction methods shall comply with the California

Department of Transportation (CALTRANS) Specifications, Hot Mix Pavements.

List of Contract Line Items

Base Bid

• Pipe Repair

Option 1

• Repave Road Cut

ON-SITE WORK HOURS: Work shall be generally performed during normal business working hours of 8 a.m. to 5 p.m., Monday through Friday, except when otherwise indicated. No holiday work will be allowed.