S
ECTION 9.10 – MICRO-TRENCHING
9.10.1 DESCRIPTION
This section establishes the requirements for the construction, installation, inspection, and restoration of micro- trenched broadband conduit systems within the City of Fairfield public right-of-way (ROW). Work includes all labor, materials, equipment, and documentation necessary to complete micro -trenching and associated conduit, vault, and appurtenance installation in accordance with approved plans, City Standard Specifications, federal and state codes, and all permit conditions.
All broadband/fiber/communication/cable installations shall follow the City’s “dig once” policy.
When trenches or pavement cuts are opened for any utility work, conduit for future broadband infrastructure shall be placed to minimize repeated disturbances within the ROW.
Applicant /Contractor shall inform other utility providers about the MT schedule at least 4 weeks in advance and provide an opportunity for others and the city to install conduit in the same trench as the city’s dig -once policy . T his will minimize deterioration of street pavement.
Applicant/Contractor shall show proof of communication.
Contractors must document pre- construction site conditions with photographs and maintain a complete log of existing features. Any damage to landscaping, irrigation, pavement, or structures shall be restored to equal or better condition at the Contractor’s expense.
9.10.2 PERMITS, APPROVALS AND GENERAL REQUIREMENTS
A. Permits and Submittals
1. A fully executed Micro-Trenching Maintenance Agreement shall be in place prior to work.
2. An Encroachment Permit is required for all micro-trenching activities. Submittals shall include:
• Conduit and vault layout plans
• Installation details
• Traffic control plans
• Proposed trench alignment
3. A complete list of equipment and materials shall be submitted for City Engineer approval before construction.
4. A geotechnical firm shall perform required materials and compaction testing in accordance with City standards.
B. Restrictions and Limitations
1. Micro-trenching is permitted only in asphalt-paved public streets. It is not allowed in concrete pavement, decorative paving, alleyways, sidewalks, gutters, curbs, valley gutters, driveways,
EXHIBIT A
ADA ramps, bus pads, traffic -calming features, roundabouts, islands, or other specialty paved areas.
2. Streets under moratorium require City Engineer approval.
3. No more than:
• Two micro trench cuts allowed in any street. may place conduit in any street, each on opposite sides. This requirement may be amended by the City Engineer to be more restrictive depending on type of street, traffic volumes or other concerns. • Two vertically stacked conduits may be placed within a trench. Additional conduits must be approved by the City Engineer.
4. No micro-trenching is permitted within 350 feet of signalized intersections to avoid damage to traffic loops; boring may be required. This should be measured from back of crosswalk/stop bar. However, it is required that the contractor meet in advance with the city to mark layout/conflicts.
5. No above-ground pedestals are allowed unless specifically approved. All splicing shall occur in approved ground vaults.
6. All ducts must be located according to current industry standards.
7. Micro-trench alignments will not be allowed (closer than 3 foot) parallel and directly above publicly owned utilities.
C. Contractor Responsibilities
1. The Contractor must repair or replace, at no cost to the city, any installed conduit or fiber damaged during City maintenance operations (including stormwater, water, sewer, sidewalks, paving, or signal work).
2. A draw -down inspection account must be established and replenished when the balance reaches 20 percent.
3. A 24-hour emergency contact must be provided.
4. Weekly three-week lookahead schedules and daily 24-hour advance work schedules shall be provided during construction.
5. All USA markings created for the project must be removed (power washing or approved method) after work.
6. A GIS or CAD map of installed assets shall be provided, including conduit locations, side of street, duct quantities, excess-capacity ducts, vaults, and all project appurtenances.
7. If conduit will no longer be maintained, the owner must notify the City Engineer and transfer ownership to another party or to the City.
D. Work Hours
1. 7:00 AM–5:00 PM Monday–Friday
2. 9:00 AM–2:00 PM near schools when school is in session
3. No weekend or holiday work without City approval
9.10.3 MATERIALS
A. Conduits
1. PVC or HDPE Schedule 80, minimum 2-inch ID unless otherwise specified.
2. SDR-11 orange innerduct with pre-installed mule tape (1600-lb minimum).
3. Fabric innerduct (e.g., MaxCell) or multicell micro duct bundles (e.g., FuturePath) may be used when approved.
4. All conduits must be electronically locatable and include detectable warning tape 6–12 inches below grade.
5. Factory bends only; minimum bend radius 18 inches.
B. Vaults
1. HDPE or polymer vaults meeting Telcordia GR -902-CORE, ANSI/SCTE 77 Tier 22, and AASHTO H-20/H-25 loading.
2. Standard size: approx. 36" depth by 35.5" × 28.75" opening, larger where required.
3. Vault covers shall be composite or ductile iron with anti-slip and anti-seize design and labeled by contents.
4. Vaults shall be installed on a minimum 8- inch crushed rock base, level and supported per specifications.
C. Appurtenances
1. Polymer concrete pull boxes, traffic-rated, labeled by content.
2. All water-adjacent fittings must meet NSF-61.
9.10.4 INSTALLATION
A. Alignment and Location
1. Micro-trenches shall be placed 5 feet from face of curb unless otherwise approved.
2. Trenching is limited to asphalt local streets, except were approved for collectors and arterials.
3. Crossings shall be at 90 degrees and limited to one per block or 500-foot spacing.
4. Trenches shall avoid wheel paths.
B. Trench Dimensions
1. Depth: minimum 18 inches– maximum 22 inches below asphalt surface, unless approved otherwise by the city.
2. Width: 2–4 inches
3. Vertical separation: minimum 12 inches at crossings
4. Horizontal separation:
• 3 feet from water and power utilities
• 5 feet from sanitary sewer and storm drain utilities
C. Utility Locating & Potholing
1. Contractor shall call USA 48 hours before work and pothole all crossings and utilities within 24 inches of proposed trench alignment vertical and horizontal.
2. Potholing must be performed by coring—jack-hammering is prohibited.
3. Mobile ground-penetrating radar must be used to identify metallic and non-metallic utilities to 24 inches depth.
4. All utilities must be potholes where the micro trench shall be performed. The inspector must witness all potholes where utilities cross the trench above or below and any utilities within 3 feet running parallel to the trench.
D. Conduit Placement
1. Conduits must be secured to prevent floating or rising every 10 feet.
2. All conduits must be sealed to prevent water intrusion.
3. Shadow duct (City excess-capacity duct) shall be installed where required, including independent vault access approximately every 1500 feet.
E. Backfill and Restoration
1. All trenches must be fully backfilled the same day using 3000-psi cement-sand slurry (CLSM).
2. No trench may remain open overnight.
3. Asphalt restoration must begin once slurry cures and must be completed within 30 calendar days.
4. Grind-and-repave requirements:
• Collectors: 4-inch minimum
• Arterials: 5-inch minimum
• If existing asphalt is <4 inches, grind full existing depth.
5. Grinding areas must be extended when within:
• Trench interferes with a wheel path, or
• 24 inches of another restoration.
6. Restoration in bike lanes shall extend to a full lane width.
7. All striping damaged must be replaced in kind.
8. If trench restoration deteriorates prior to general resurfacing, the Contractor must perform additional repairs within 10 days of City notification.
F. Housekeeping
1. Trench spoils must be removed immediately with a vacuum truck or approved method.
2. All sites must be swept daily; no equipment or materials may be stored outside working hours.
9.10.5 INSPECTION
1. City Engineer must be notified at least three working days before potholing.
2. City inspector will verify traffic control, materials, installation, and restoration.
3. Contractor must provide 48-hour notice before work near traffic signal loops; damaged loops must be replaced at Contractor cost.
4. The trench must be inspected before backfilling and after completion of backfill.
5. All crossings must meet in-depth and backfilling requirements, according to the city standard specifications.
9.10.6 MEASUREMENT AND PAYMENT
Payment is made per linear foot of conduit installed (measured from center-to-center of vaults or pull boxes). Trace wire, pull tape, trench backfill, trench restoration and installation per these specifications shall be inclusive to the per linear foot of conduit. Compensation includes all labor, materials, equipment, testing, traffic control, documentation, and incidentals required to complete the work.
Vault Vaults and installation shall be a separate pay item.
All materials and installations are subject to applicable warranties as required by City Standard Specifications. A minimum one- year warranty applies where not otherwise specified, and all manufacturer warranties shall be assigned to the City.