I've been working on a natural gas pipeline project in the desert that more-or-less follows Interstate 40 from Needles to Barstow (140 miles). The pipe is 30-inches in diameter with a wall thickness of 1/2-inch. The working pressure is about 900 psi, but it is greatly reduced while we work on it (to less than 1/2 psi at some times). From Barstow, the gas is ultimately delivered to southern California.

The pipeline was built in the 1950s, and the gas company needs to check the pipe for corrosion. To do so, they send instruments (called "pigs") down the inside of the pipe that take readings of the corrosion. There are a series of different pigs in a pigging operation, but the main "smart" pig uses strong magnets and powerful computers to measure the thickness of the steel pipe. By inference, where the pipe is thin, it is corroded. If there is too much corrosion, the gas company must dig up the corroded spot and repair the pipe.

The current problem for the gas company is that the 30-inch pipe has valves every 10 miles that are only 24-inches in diameter. A 30-inch pig cannot pass through a 24-inch valve.

So the first matter of business was to replace the old valves with new and improved, 30-inch valves that the pig can fit through.

I started in July, and it is now mid-October. My job on this project is to ensure the safety of desert tortoises, which are listed under the Endangered Species Act as "Threatened," one step below the worst category of "Endangered." Under government permit, the gas company is allowed to "take" (a legal term that more-or-less means kill) two tortoises per year in their entire southern California desert region on all of their many repair projects. The gas company takes this very seriously, and unfortunately, they killed one back in May.

The main danger for tortoises on this project is being hit by vehicles, so one of my main job functions is to drive slowly ahead of construction vehicles looking carefully for tortoises. We need to spot hatchlings just as much as full-grown adults, so I constantly scan the roadway for 2-inch-long hatchling tortoises trying to disguise themselves as one small stone among many.

Next, we escort the trucks and equipment to the worksites where they will dig up the pipe to expose the old pipe and valve.

There are 13 valves and two other features on this project, so we will have 15 "dig" sites, each of which is about 10 miles apart.

Here a "digging crew" is working to expose the old pipe and valve.

A biologist is monitoring the construction activity to ensure that procedures are followed to protect tortoises and also to keep tortoises out of harm's way should one walk into the work area. This could involve the biologist calling a stop to all construction work until the tortoise moves out of the area on its own, or it could involve helping the tortoise exit the area quickly and safely.

Here a "digging crew" worked for three days to expose the old valve and pipe. It doesn't show well in the photo, but there is a metal screen fence around the pit to keep tortoises from falling in. There is also an orange plastic fence to keep humans from falling in.

After they dig the pit, the crews must install temporary fencing around the pit to ensure the safety of tortoises and of humans. For tortoises, the crews use wire-mesh fence that is 36 inches high. Crews bend the fencing at 14 inches, set it on the ground with the 22-inch segment upright, and cover the 14-inch segment with dirt to create a barrier that tortoises can't dig through.

Outside the tortoise fence, the crews erect orange plastic snow-fencing. This is to keep humans from inadvertently falling into the pit. They also set up highway barricades with reflectors and flashing lights to warn humans of the hazard within.

Cutting out the old valve assembly. During valve replacement, the gas company reduces the pressure inside the pipe to less than 1 psi. By keeping some pressure inside the pipe, and by working hard to let as little as possible escape, they keep air out of the pipe. With no air (oxygen) inside the pipe, there can be no fire inside the pipe, and therefore no explosion.

Have you ever wondered why there are always so many people sitting around doing nothing on construction sites? Read the next segments for one answer.

Lifting the old valve assembly out of the pit. Note that the end of the old is covered with wet burlap. This keeps air out of the pipe while the valve is being replaced.

We had one exciting moment when something went wrong and a large (at least it seemed large to me) fire ball erupted into the sky. The six men in the pit scrambled to safety, and the four men on "fire watch" quickly extinguished the flames.

One heroic guy went back into the pit to cover the pipe and contain the gas, and while there, kept calling for a fire extinguisher. The guys on fire watch kept spraying him with their dry-power fire extinguishers until they realized he wanted a fire extinguisher, not be be extinguished himself. The guy was heroic, but a bit of an ass, so I could only chuckle about his situation when it was over.

Welding the new pipe in place. It doesn't show, but there is always some pressurized gas inside the pipe, so the gas burns outside the pipe while the welders are working.

Note the guy in the background sitting around "doing nothing." He is on "fire watch," and his job is to say alert in case of fire. The pin on his extinguisher has already been pulled, and he is prohibited from eating, talking, or doing anything that could distract him from the business of being ready to put out a fire. There are always four or five men on fire watch during welding operations.

Before the pipe can be reburied, the cribbing must be removed, so another crew builds concrete supports under the pipe to hold it in place during the back-filling process.