- What is the cost of SUE investigation?
As is typical for the industry, the cost depends on the project. Costs include personnel, equipment, etc. The answer to the question depends on the ASCE Utility Quality Level of SUE investigation you are interested in (Levels D through A). Please contact us if you have a specific project scope of which you are curious, and we’d be happy to provide more detail.
- Design tickets take up to 3 weeks.
Not a question, but a good point made by a participant to compare to the 2-day or 3-day response requirement for Dig Tickets in Ohio and Michigan, respectively. For Design Tickets, the response tends to be more loosely treated, as excavations are not being performed. Therefore, response times can vary. We’ve had instances where we did not receive drawings until many months after the request was made; however, I would say this is not the norm and that more often than not we receive drawings within a couple weeks. On occasions, follow-up requests are needed as reminders.
- Do you work with competing surveyors who do not have the same investigative capabilities?
We do have competition, typical of other service industry providers. Without getting into specifics, I would assume each company trains their staff a certain way and also uses certain equipment that may differ from their competitors. We routinely work with (as the Prime or as a subconsultant) several professional survey firms when our markings are surveyed for CADD drawings, GIS, etc.
- How do you get access to the pedestals to hook onto the tracer wire for private utilities? Do we have legal rights to hook up to them?
If a utility is located in the public right-of-way, we have surveying rights that the governing agency allows through their permit process, which we make sure we look into and follow. When inquiring for permits, we describe the type of work we will be undertaking. In regards to private utilities, if access is prohibited, these utilities typically will require a specific tool to open their facilities – such as a specific wrench socket to which only the utility company has access. In this case, we will inform the owner and obtain access permission based on the owner’s protocol.
- How quickly can you respond to an emergency?
We like to consider ourselves very responsive. To provide an example, NTH is currently performing SUE services on two “emergency” projects involving failed subsurface utilities. In both cases, we have responded within 24-hours, including working weekends and holidays. We understand the need to act quickly to reduce safety risks at an emergency site and to reduce the time which facilities are out of service.
- In Pennsylvania it is a requirement for design engineers to contact PA One Call, get a serial number from them, and that number and the date of the One Call request must be shown on the drawings that go out for bids and construction. It is then the Contractor’s responsibility to again contact PA One Call prior to starting and underground installations.
As stated during the presentation, One-call notification is the law and therefore the entity in charge of excavation is required to call regardless of the amount or ASCE Utility Quality Level of SUE already performed. There are multiple reasons for this and some are listed below:
* So that ground markings are present during construction that occurs sometime after SUE services are performed
* Errors can occur based on the ASCE Utility Quality Level performed during SUE
* New utility installations could have been made after SUE and prior to construction
- It would seem that researching the history of a property would also be useful in determining what may exist below-grade, but in actuality, is this ever done?
This is absolutely done. During the presentation we mentioned that record drawings are received during Design Ticket requests. The same occurs prior to performing our SUE work. We obtain record drawings available through the owner of the property (usually readily available as part of the project), as well as through requests to the utility companies. These drawings are evaluated by our SUE personnel.
- Voids around sewers can cause settlement of roadway and plug sewer.
During the presentation it was stated that voids around sewers can be detrimental to the sewer. To expand on this: voids can result in uneven support of the sewer and cause failure of the sewer, which often times results in a sink-hole above the sewer. This is one reason why we perform evaluations of sewers using Ground Penetrating Radar.
- With GPR, does your equipment pick up utilities that are less that the general rule the utility must have a diameter of 1 inch per 1 foot of depth to detect?
The limitation mentioned is the general rule of thumb for the type of GPR device we typically use for non-structural SUE investigations. The device I am referring to is a GPR with a 250 MHz antennae (the portion of the equipment that transmits the electromagnetic waves). Different frequency antennae will result in different resolutions. For example, a higher frequency antennae may be able to go above and beyond this limitation, while a lower frequency antennae may have trouble detecting a 4-inch pipe that is buried three feet deep. The higher the frequency, the less depth penetration that occurs. Therefore, from a feasibility standpoint for target depth compared to target utilities, the 250 MHz has proven to be the go-to tool for non-structural SUE investigations. In some instances, utilities may be undetectable.
- Are fiber optics utility lines more restrictive to SUE?
Fiber optics can sometimes be placed without a metal shielding to the fibers. When this is the case, yes, they are restrictive to line locators that rely on metallic conductivity. GPR is then used to search for buried conduit that is housing the wire, if such a conduit exists and is large enough to be detected (see response to question 9 above).
- Water jetting seems like it might cause more problems.
We’re not sure what this question refers to, as water jetting is a common practice used to clean debris from sewers. If a utility is in poor condition, the water jet could break away loose, deteriorated materials from the pipe. In this case, the facility is in need of rehabilitation. Feel free to reach out to us if you have additional information you would wish to discuss on this topic.
- The line locator will also pick up a signal from magnetic marking tape over non-metallic pipe.
A good point made by a participant. There are various ways utilities are installed, which can assist in locating. For electromagnetic line locators, a form of metallic conductivity is required. The magnetic marking tape, marker balls, tracer wires, etc. are ways of making non-conductive facilities traceable.
- I would recommend taking a picture of markings after complete, in case someone removes the flags. This has happened and contractor hit sewer line.
Another good point made by a participant. Taking pictures of markings is a common step that we make sure we follow during our SUE work. Documentation is considered very important. We generally make field notes and measurements for any SUE job. Survey of the markings is the best way to retain the information for future use.
- Wouldn’t surveying and measuring the depth of a manhole give you vertical information for that particular utility?
Yes, it would give vertical information at that particular location where the measurements occur and this is commonly performed and recorded. This does not however guarantee vertical information beyond the point of measurement. For gravity sewers, one can assume the vertical alignment of two points are know from manholes. Other services could have varying alignments between manholes.
- Since the degree of accuracy is related to the cost of underground utility locating, do you see better bids from contractors when more information is available, thus the upfront costs may save future construction costs.
Absolutely. Anytime an unknown is removed, the Contractor has information to help them provide a more accurate cost. On the other hand of the question, utility locating can also help avoid a Contractor from guessing too low on cost due to an unknown – this can help avoid claims and change orders during construction.
During our last webinar, The SUE Advantage, the speakers received many questions that they were not able to answer due to time constraints. We want to make sure everyone's questions are addressed whenever we can, therefore, our SUE experts (Ryan P. Butler, P.E. and Tyler A. Dawson, Ph.D., P.E.) have reviewed the questions and provided below. If you missed it, you can view the original SUE webinar here.
The NTH Narrator
NTH Consultants, Ltd. (NTH) is a nationally recognized engineering firm specializing in Geotechnical, Environmental, and Facilities Engineering.