Downtown Fort Worth is entering a building boom.
There are a number of residential and commercial projects in the planning phases, and there is substantial utility construction that needs to be done to accommodate the future demand.
One of the largest such projects is a high-rise residential and commercial skyscraper on the edge of downtown, near the central train station.
The project has been mentioned in the local newspaper, the Fort Worth Star Telegram, and has generated lots of excitement.
One of the major financiers of the project is William “Bill” Cawley of Cawley Wilcox Companies.
“Fort Worth is a great office market,” said Cawley. “And it’s a great city. It’s one of the most stable markets in the U.S.”
Developers are facing a pro-growth atmosphere in City Hall, which furthers their ambitions.
Mayor Mike Moncrief agreed with bullish pro-growth market sentiments, “I know there’s demand for square footage downtown, offices large and small alike.”
To realize that growth, there is a formidable challenge on the construction end directly in the path of the planned facilities.
Beneath the bustling streets of downtown Fort Worth, there exists a labyrinth of live and abandoned utilities of all variations, many of which date back more than 100 years to the birth of the city itself.
The situation is the same under the streets of other American cities, and is particularly intricate in heavily urban, older central business districts.
In the case of Forth Worth, the utility department has granted easements to 19 franchise utility companies.
The number of entities with ownership to underground lines has increased significantly with the advent of the fiber-optic age and the deregulation of the telecommunications industry, dating back to the breakup of AT&T in the early 1980s.
Many of these lines have therefore been laid in recent times, which has drawn complaints from motorists weary of roads that are in a seemingly constant state of cut and asphalt overlay.
Not all of these excavations are due to the franchise, or “dry,” utilities.
There is a substantial amount of municipal infrastructure to service downtown areas, and they must be sized to handle much larger demands than their suburban counterparts.
When speaking loosely of city-owned amenities, such networks can be divided into three categories: potable water, sanitary sewer, and storm drain collection systems.
The equation is made more complex by the addition of abandoned facilities underneath the city streets.
In the case of Fort Worth, the city was built on the banks of one of the three forks of the Trinity River.
In the early-20th century, a network of masonry tunnels was built throughout the central business district to serve the purpose of draining stormwater runoff away from the streets and into the river.
These tunnels were built on the crushed stone of existing streambeds, along whose alignment the tunnels followed, thus making use of natural topography for a cost-effective drainage system.
In many cases, these tunnels dated back to the days of “combined sewers,” when population was sparse enough that washing human waste into the river did not create large-scale public health problems (although outbreaks of cholera are well-documented across Texas prior to the days of wastewater treatment plants).
As the city grew, sanitary sewers were built to send human waste to such treatment plants, and pre-cast storm drain pipes were installed to handle larger flows of water associated with increases in development patterns that led to more stormwater runoff due to more paved surfaces.
The masonry tunnels became obsolete, but were abandoned-in-place, because there really wasn’t reason to remove them, and because they could serve as auxiliary flood control structures in the event of heavy rainfall.
Such tunnels pose an interesting challenge for current construction projects.
For many years, the tunnels sat undisturbed. However, Fort Worth is currently going through a surge in residential construction, a trend that is a boon to the city tax rolls.
Such construction must be tapped into the underground network of wet and dry utilities, which leads to challenges for contractors doing business downtown.
In the case of the tunnels, little is known about their exact location and about lateral tie-ins.
This, coupled with the fact that there are up to 19 franchise utilities running underneath the pavement (which is often asphalt overlaid on brick pavers), can make both large and small excavations an uncertainty.
It is often necessary to make a confined-space entry of the tunnel, in order to map the line.
Safety precautions for entering abandoned storm tunnels are governed by the Occupational Health and Safety Administration (OSHA).
There are a number of tools that are used to make the job easier, as well as protocol that must be followed to ensure the safety of all involved.
The municipality must be notified, and personnel from the fire department must be on-hand to assist in rescue operations in the event of an emergency.
Entry and exit from the confined space must be documented, and support staff on the ground must establish some form of communication with the entrants.
Confined space entry is unlike other routine excavation-planning operations. According to Bill McCook, who has performed subsurface reconnaissance, “It’s definitely a bit of a claustrophobic feeling at first, but it really makes you think about all the history down there — years and years of infrastructure that was built well before any of us were around.”
Personnel working in confined space must be outfitted with suitable equipment to do the job. This includes wet suits, which can be necessary when working in tunnels that are often wet throughout most of the year.
Most importantly, potential exposure to harmful gases must be identified and prevented. Storm drains are often contaminated with harmful gases, since the underground positioning of the drains is ideal for collection of fatal sewer gases, which are heavier than air, and therefore gravitate toward low elevations.
This is accomplished via the use of a four-gas meter, such as the RKI GX 2003 Personal Four-Gas meter. Such a tool is calibrated to local conditions, and identifies the presence of sulfide gases, carbon monoxide, natural gas, and oxygen.
In addition to sewer gases (which are sulfide-based), natural gas breaches in nearby gas lines can lead to the smell of the odorant of natural gas, which smells like rotten eggs, and is an indicator of flammable conditions.
If oxygen readings are too low, it is required that fresh air be pumped into the working area.
Furthermore, ventilation systems can be established to keep a fresh supply of air available at the worksite.
More information on ventilation standards and safety precautions can be acquired through OSHA.
Safety regulations have become much more detailed than in previous years, when the only “precaution” was to throw a canary into a storm drain, and see if the canary survived, which indicated that the area was free of noxious fumes.
Sanitary sewers must similarly be explored, in order to understand their alignment, cross-connections and the overall condition of the system.
In many cases (especially downtown), it is impractical to make an open-cut excavation with a backhoe in order to make a simple diagnostic assessment of an existing sanitary sewer line.
For this reason, television inspection can be of enormous value to contractors and municipal officials.
The Envirosight Rovver 400 robotic crawler camera is suited for such investigation. It can be placed in a sanitary sewer manhole and controlled via a heavy-duty cable connection leading to a support truck on the street.
The camera is typically equipped with support lighting, in order to capture video imaging in near-total darkness.
In the case of larger pipes, the camera can be placed on a wheelbase, which can maneuver over obstacles and small changes of grade in existing pipe alignments.
Television survey equipment is fitted with an odometer, so that the linear location of lateral tie-ins can be documented.
Oftentimes, television inspections are commissioned by municipal employees in search of pipe joints that are faulty, or areas in which entire segments of pipe have been crushed, either by tree roots, adjoining lines, or expanding soil.
Due to the many hazards that underground lines are subjected to, television inspections can serve the purpose of monitoring existing conditions, or preparation for a proposed tie-in.
Techniques are different for reconnaissance of sanitary sewer and storm drain appurtenances that are below the ground of congested urban areas.
The end goal is the same, however: to ensure that when excavation operations commence, construction equipment operators are provided with the best information possible about the location and condition of existing subsurface utilities.
(David H. Recht owns an Irving-based civil engineering and construction firm.) CEG