Contractors & Excavators

Contractors and professional excavators are required by law to notify Iowa One Call at least 48 hours prior to ALL excavations (excluding Saturdays, Sundays and legal holidays). Upon notifying the Iowa One Call center of a pending excavation the contractor will be assigned a nine-digit “dig-ticket number”. All excavators at a given site must have a dig ticket number to be compliant with the law. Contractors and sub-contractors may NOT use the same dig ticket number. All contractors and excavators must notify Iowa One Call of their excavation work. If a contractor is to excavate on a homeowner’s property, it is the contractor that is required to notify Iowa One Call for locate markings – not the homeowner.

Locate requests to the Iowa One Call center are accepted 24 hours a day and 7 days a week. The call center, which is located in Davenport, IA, is open 365 days a year. Notifications must be made at least 48 hours prior to all excavations. The 48 hours timeline will commence only during normal business days between the hours of 7:00 a.m. and 5:00 p.m. and does not include weekends or legal holidays (the 48 hours timeline on calls after 5:00 p.m. will begin at 7:00 a.m. the following business day). Excavators who do not make notification to Iowa One Call or do not wait the required 48 hours prior to excavating are in violation of the law and subject to civil penalties. Emergency calls are processed immediately with no 48 hour timeline. Owners/operators of buried facilities will respond to emergency locate requests as soon as reasonably possible.

How to Make a Request

What is an excavation?

Iowa law defines excavation as meaning an operation in which a structure or earth, rock or other material in or on the ground is moved, removed, or compressed, or otherwise displaced by means of any tools, equipment or explosives and includes, but is not limited to, grading, trenching, tiling, digging, ditching, drilling, augering, tunneling, scraping, cable or pipe plowing, driving and demolition of structures.

As described above, the law defines an excavation as much more than simply digging into the earth. Iowa One Call must be notified prior to any operation that may disturb or potentially disturb buried facilities. Excavators should not make any assumptions about the depth at which a facility may be buried.

Identifying The Excavation Site

When making notifications to the Iowa One Call center excavators must identify as accurately and specifically as possible the excavation site to be marked for locates. If there is an existing 911 address, that address must be used along with the specific information required by Iowa One Call. Use of GPS coordinates will help define an area but must be used in conjunction with the other required descriptive information.

White Lining

The best way to identify the proposed excavation area for the locators who apply the markings is to white line the area prior to their arrival. Marking the proposed excavation area in white allows the locators to concentrate their efforts in a specific area, which allows for more accurate markings and safer locates. White lining is a process that enhances communication between the excavators and locators and should be practiced at all excavation sites. Another advantage of white lining is the reduction of paint and flags at the site, which can become an eyesore to property owners.

Reporting Damaged Facilities

Excavators are required to report all damages caused to buried facilities regardless of the extent or severity of damage. Even minor scrapes or dents can breach the integrity of the facility and lead to ruptures, failures and loss of service. Damaged tracer wires leave facilities untraceable and must be reported immediately. Excavators who encounter or cause damage to buried facilities have the choice of calling 911 for emergency notification, the owner or operator of the damaged facility or Iowa One Call.

Liability for Damaged Facilities

All excavators are liable for any damages they may cause to buried facilities. Simply calling Iowa One Call does not necessarily relieve an excavator of these liabilities. For example, a damaged fiber optics line may be extremely costly to repair and the financial obligation of the contractor/excavator responsible for the damage. Excavators need to take precautions and dig safely to avoid damaging buried facilities. In the event the locate markings are clearly inaccurate the liability for damage may shift to the facility operator.

How accurate are the markings?

Your underground facilities will be marked with paint and/or colored flags to approximate the location of the buried facilities. Iowa law allows for an 18 inch Tolerance Zone on each side of the buried facility. Excavators should try to avoid digging in this tolerance zone. If your plans demand that you must excavate in the tolerance zone, Iowa law requires that the buried facility within that tolerance zone be exposed. You expose the buried facility by hand digging with extreme caution. You must not use any type of power equipment to expose a buried facility within the tolerance zone (vacuum excavation is the only accepted means of exposing a buried facility in the tolerance zone other than hand digging). Keep in mind that the 18 inches is to be measured from both sides of the buried facility (18 inches on either side of a 4 inch facility requires a 40 inch tolerance zone – refer to chart). If you must excavate within the tolerance zone it is a good idea to call the operator of the buried facility (i.e.: gas & electric utility company, telephone company, etc.) to verify the size/diameter of the facility in question.

Color Code Chart

How Long Are The Makings Good For?

Under Iowa law the locate markings are good for as long as they are maintained and clearly visible. It is the responsibility of the excavator to maintain the original markings throughout the duration of the excavation even if it requires establishing reference points in the event the markings may be destroyed. Iowa law requires that the facility operators apply the markings in a manner that will last a minimum of five days on non-permanent surfaces and ten days on permanent surfaces. At the end of the five or ten-day period, depending on the surface type, excavators may call for relocates if they are not able to maintain the markings. However, to be compliant with the law, excavators must take the necessary precautions to maintain the original markings. Keep in mind that the original markings applied by the facility owners/operators (through their in-house or subcontracted locators) must not be altered. In the event a relocate is needed, the excavator should use the existing dig-ticket number as a reference for the call center operators. Iowa One Call does error on the side of caution. However, contractors and excavators must not take the system for granted. Misuse of the system will be reported to the Iowa One Call Board of Directors and possibly the Iowa Attorney General.

Global Positioning System (GPS)

Although Iowa One Call does not require GPS coordinates as a means of determining location, excavators are now given the option to utilize GPS readings on all locate notifications. While this information can certainly enhance the process of locating buried facilities, the practice of combining GPS coordinates with computer-based mapping leaves some room for error.

These errors stem from the fact that many mapping systems are not developed accurately enough to correlate with the precision of GPS coordinates. Commercial mapmakers utilize existing government maps (known as TIGER files) as a base and enhance them accordingly. It was the Census Bureau, not surveyors, that developed these TIGER files. The accuracy of a mapping system depends on the corrections and updates made to the original base maps. Some maps are less “enhanced” than others.

GPS (Global Positioning System) is a means of determining your position on the earth and is expressed in Latitude/Longitude coordinates. Verifying the Lat/Long coordinates of landmarks such as boundaries, streets and waterways will enhance a mapping system. Iowa One Call utilizes a GIS (Geographic Information System) mapping format for locate requests. IOC updates and enhances the mapping system with data provided by GIS sources such as GDT (Geographic Data Technologies) and Geo Com. This data, which is Lat/Long coordinated, creates a more accurate mapping system and allows GPS coordinates to be used as a means of identifying location.

The Lat/Long based mapping grid used by IOC is generally 1/5-minute or 1/5-mile square. A 1/5- minute grid is approximately 1,000’ x 1,000’ at the equator. Because the earth curves, that same grid changes to approximately 800’x 1,200’ in Iowa. Mapping systems are generally not a precise replica of the earth. While the IOC mapping grid is very accurate, there will be some variance in the position of the grid as it correlates with “the face of the earth”. The coordinates taken by a GPS unit will also have some variance in accuracy.

The Global Positioning System is a worldwide radio-navigation system formed from a constellation of 24 satellites and five ground-monitoring stations. The GPS process is a complicated method of measuring and correcting the velocity and timing of radio signals through a digital code. When all of the conditions are right, the GPS coordinates may be accurate within a few feet. Again, this process is complicated and may involve differential positioning for correcting inaccuracies. The point is, your GPS reading will have some variance in accuracy and when combined with the mapping system, that also has variances, the determined location will not precisely correlate with the actual position on the earth.

Summary

GPS is a means of determining a certain position on the earth and is expressed in Latitude and Longitude. Latitude and Longitude was established well before the invention of, and is not the same thing as GPS. Latitude is the horizontal angular distance, in degrees, minutes and seconds of a point north or south of the equator. Longitude is the vertical angular distance, in degrees, minutes and seconds of a point east or west of the Prime (Greenwich) Meridian. GPS is used to find a position on the earth, not a map. Verifying the boundaries and landmarks of a map with GPS will enhance the accuracy of that map. The accuracy or correlation of GPS coordinates with a map will depend on the accuracy of the map and the GPS reading itself. IOC constantly updates and enhances the mapping system with Lat/Long geographic data. GPS coordinates will help the IOC Customer Service Representatives at the call center determine the location of a proposed excavation. Excavators should remember that GPS is only one method or tool used for determining location. IOC still requires the excavator to provide specific descriptive information about the proposed excavation site. In many instances, the 911 address of a property will be the most precise means of determining location.