|During private development and/or public sector construction projects, the avoidance of damage to underground and overhead utility systems caused by excavation and utility installation/repair activities is imperative. Accurate utility locations assure that damage to or relocation of existing underground utilities caused by the presence of unknown or mis-located utilities is minimized. Overhead utility lines are becoming a thing of the past except in rural areas. The urban underground has become a spider's web of utility lines, including phones, electricity, gas, cable TV, fiber optics, traffic signals, street lighting circuits, drainage and flood control facilities, water mains and waste water pipes etc. The deregulation of utility services is adding to the problem as multiple service providers seek to place their networks underground. All utility lines are susceptible to being damaged as construction and renovation equipment excavate in their vicinity. Historical records are often poor with inaccurate utility positions and/or depths. Some “live” services do not even show on the construction drawings or as-built plans. This means that the ability to physically determine the location, nature and depth of underground utility services is critical to reducing the risk and consequences of inadvertent damage during construction.
Annual Utility Meetings
In April or May, the DPW&T schedules a utility coordination meeting with representatives of all the local utility companies, including the Metropolitan Commission. The purpose of the meeting is to: recap the lessons learned over the past year; offer policies and solutions to problems encountered; discuss the upcoming construction season, evaluate the availability of easements; coordinate specific projects of mutual interest, and solidify timing/duration of any needed relocation efforts. All work is performed and coordinated under a Master Utility Permit.
R/W 57 Forms
For capital roadway improvement projects, copies of the design plans are forwarded to all the local utility agencies by the DPW&T Engineering staff. The plans are reviewed by the respective utility and “marked-up”/ “red-lined” if records show utilities in the vicinity. The proposed disposition of existing services (i.e. relocate, reset, remove, etc.) are also denoted on the plans. A Utility Tabulation (R/W 57) Form is completed by the utility to designate pole numbers, stations and offsets from the road plans, date of grant to the utility, title information (if available) and offer any general remarks. A joint utility field walk-through is conducted to ensure the accuracy of the survey forms. The information on the forms is used to finalize the County’s cost responsibilities associated with the moving, upgrading and relocation of individual and shared utility service(s). This assessment of cost responsibility is known as Prior Rights Determination. Once this has been determined, a Notice-to-Proceed with the relocation of utilities is provided by the DPW&T.
Miss Utility is a "One Call" notification center that is mandated as a partial solution to the utility damage problem. Miss Utility serves as a single point of contact for excavators to determine which utilities are present in the area in which they will be digging. Miss Utility notifies the utility companies with utilities in the vicinity of the dig area and the utility company provides a physical locating/marking service prior to the excavation. In Maryland, utilities are scheduled to be located within 48 hours from the time the locate is requested. For more information about Miss Utility or to submit a location request, call 1-800-257-777, dial the new "811" Federal Communications Commission hotline or the view the Miss Utility website.
Although many existing methods can give more precise information under favorable conditions, the following information is considered the normal precision of utility location information (not including mis-locates): Typical Surface-only Utility "Locates"; Horizontal location within 24 inches either side of location markings; Vertical location not provided; Typical Surface Survey with Vacuum Excavation Potholes for confirmation (Subsurface Utility Engineering (SUE) provider; Horizontal location within 0.5 feet; and Vertical location within 0.05 feet.
Utility Trench Relocation Costs
Estimated costs for the relocation of utilities vary depending on type and location. Good budget figures for the relocation of utilities during major construction projects are: $15,000 per mile for overhead cable; $27,000 per mile for buried cable; $133,000 per mile for overhead phone lines; $264,000 per mile for underground service; $54,000 per mile for electric service; and $5-10,000 per utility pole/pedestal.
Destructive methods include soil borings, test pits, hand excavation These procedures are used to confirm the position of known utilities or previously located utilities prior to actual construction. Non-destructive methods of locating objects underground typically utilize a wave/signal that is introduced into the ground and/or a physical property of the object that is to be located that is different from the surrounding ground. An instrument is then used to measure the ground response and from this response, information about the position of the object below ground and/or soil properties is inferred. Both methods described above have problems in one or more of the following areas:
They cannot locate all types of utilities
They can't be used in all types of soils
They are affected by interference from nearby objects
They cannot penetrate to the required depths
They cannot resolve smaller utilities at the required depths
They use hazardous materials that increase cost and risk
They have a cost when used in normal practice that exceeds what the market is willing to pay.
The conduits for these utilities range from steel, cast iron and ductile iron pipes to clay, polyethylene, polyvinyl chloride, and fiberglass reinforced plastic pipes. Cable may be copper or fiber optic. The conduits have different shapes, compositions, densities, and diameters, and their depths may be as little as 0 to 2 feet or in excess of 50 feet. Some lines (usually local telephone, electric and gas lines) may be stacked vertically in a common trench. Multiple lines may be grouped in a single conduit or duct bank. Multiple utilities may be grouped in common utility tunnels often called “utilidors”. For some utilities, hits cause interruptions to daily life and commerce, for others they can cause physical danger to workers, bystanders and nearby buildings. They all result in expense that is borne by a combination of the contractor, the locating company, utility providers, insurance companies and the affected public and business owners.