- SPECIAL REPORTS
- THE MAGAZINE
Wildly diverse, impressive and dangerous, Grand Canyon National Park is an incredible place, which naturally makes the opportunity to work there an equally incredible adventure.
Within the park boundaries of this water-carved wonder of nature is an impressive array of man-made water creations--a water and wastewater system comprising more than 500 sewer manholes, 400 fire hydrants, hundreds of valves and 49 miles of waterline, including the 6-inch transcanyon waterline. This amazing engineering marvel transports water from Roaring Springs, a natural spring within the Inner Canyon, 15 miles along the Inner Canyon walls to the south edge of the canyon. There, it is pumped one mile up to distribution tanks at South Rim Village.
For the three of us selected to complete this expedition, it was the beginning of an unforgettable experience into a raw and wonderful environment.
A Unique Orientation
In December 2006, our joint AME/PBS&J team--AME Project Manager Phil Hayes from Virginia, Pittsburgh-based PBS&J GIS Analyst Doug Harrison and me, the project’s licensed surveyor from the PBS&J Las Vegas office--met with NPS staff at the Grand Canyon Village park headquarters on the South Rim. At this kickoff meeting, we discussed the park service’s concerns, established relationships with onsite personnel and became familiar with the existing water and wastewater systems.
The NPS was particularly concerned about ensuring our safety and educating our team about working in an environmentally sensitive and remote area such as the Inner Canyon. NPS personnel detailed their environmental concerns about protecting the canyon’s natural inhabitants such as the endangered California condor. Safety instructions covered the dangers of falling, not just from steep trails but from the sheer canyon walls we would need to climb. The as-built location of the transcanyon waterline, which, in many places, hangs securely anchored to the cliff walls, had previously been mapped using only autonomous GPS positions with an accuracy of approximately 10 meters. We would use differential GPS to achieve submeter accuracy on our positions, which meant that accessing the waterline would be a bit precarious at times. The NPS also informed us of dangers from the canyon’s natural inhabitants such as rattlesnakes, scorpions and mountain lions. Compounding these perils was the remoteness of the Inner Canyon and the difficulty of getting help if needed.
Along with training and educational programs, we spent a good deal of time familiarizing ourselves with the water and wastewater systems of Grand Canyon Village, home to 600 year-round park workers and their families, a figure that rises to 2,000 during the summer season.
Finally, the NPS took our team on a helicopter ride into the canyon to gain a clear perspective of the transcanyon waterline path. Aside from being a white-knuckle thrill ride, as we dropped down between the canyon walls, we got our first look at the challenge before us. We quickly realized that the remote canyon, steep walls and long trek would prohibit us from using our normal survey-grade GPS equipment. Instead, we opted for Trimble’s (www.trimble.com) lightweight GeoXH hand-held GPS receiver/computer capable of subfoot accuracy running TerraSync software with Windows Mobile Bluetooth capability. To achieve submeter accuracy, we planned to apply a differential correction from continuously operating reference stations (CORS) back at the office.
The stage was set for a six-day, 20-mile backpacking trek through the Inner Canyon that challenged our fitness, our environmental awareness and our tools and technologies.
Two months later, on a cold, snowy day in February, our team of three met back at Grand Canyon Village, each carrying a backpack with 40 to 50 pounds of gear and food. In addition to clothing and personal-care items such as sleeping bags, extra footwear, etc., we packed a small stove with fuel, a laptop, camera, batteries and chargers, and the Trimble GeoXH hand-held GPS.
After double-checking our gear, we left the snow-covered rim at 7,000 feet and began our descent by foot on ice-covered trails. We planned to spend the first two nights 3,500 feet below and five miles away at Indian Gardens campground, the transition point of the transcanyon waterline where two 800-horsepower pumps push water to the canyon rim through a pipe that was directionally drilled in the canyon’s sheer limestone cliffs more than 40 years ago.
After dropping our packs in the empty bunkhouse at Indian Gardens, we hiked along the transcanyon waterline about 1.5 miles to Plateau Point, where the waterline makes its final descent to the bottom of the canyon another 1,500 feet below. This was one of the most impressive segments of the line from an engineering and construction perspective. The waterline plunges down a cliff for 500 feet anchored directly to the stone cliff face. It was a remarkable sight from the helicopter. But standing close to the edge, we were in awe as we imagined the danger and skill required by the NPS construction teams to build and maintain this section.
We spent the following day mapping and assessing the Indian Gardens campground septic and water systems and pump house using GPS. With the Trimble GeoXH, Doug and I obtained GPS positions on features such as sewer manholes, water valves, septic fields, etc., in order to position them in the geodatabase. Phil handled all asset assessment responsibilities including identifying the asset--such as type, manufacturer and age--and evaluating its condition. He also ran a video camera through all the 4-inch and larger sewer lines to inspect, record and assess the condition of the underground sewer pipes. Later, he included suggestions on replacement timetables and approximate costs in our report to the NPS.
The next leg of our trip took us the final five miles to the bottom of the canyon where the waterline--hanging from a 44-year-old suspension footbridge--crosses the Colorado River.
Upon reaching the mighty Colorado River, we dropped our backpacks and traced the waterline back to the base of the cliff below Plateau Point. With no existing trail to follow, we made our own path by following a string of water valves over very steep and rough terrain and then followed that same path back to the river.
We spent the next day surveying the systems that service this remote spot, including the septic sewage treatment facility at Phantom Ranch, a unique place at the bottom of the canyon where Bright Angel Creek joins the Colorado River. John Wesley Powell, who led a 10-man exploration of the Colorado River, camped at Phantom Ranch during that historic trip in 1869. Those who venture to Phantom Ranch today will find a campground, rustic guest cabins, a dining hall and a store built around 1930 and operated today by 15 to 20 year-round personnel.
Our nights were spent in the cabin of an NPS utilities operator who was away for the week. We were warned about the abundance of scorpions and set flypaper-type traps for them at the door of the cabin. In the middle of the night, Phil was stung on the hand when he swatted at one that had been crawling on his head. Luckily, his physical reaction to the sting was mild. He woke up to a swollen finger and eight more scorpions stuck on the flypaper traps. Needless to say, we were ready to move forward.
From Phantom Ranch, we followed the waterline upstream along the narrows of Bright Angel Creek to the headwaters at Roaring Springs. Surveying this 10-mile-long section of pipeline gave us our biggest challenge--both physically and technologically. Within the deep, narrow canyon walls that rose hundreds of feet on both sides, the window for the satellite signal was very small. We used Trimble’s Pathfinder Office software, which includes a “quick plan” menu to estimate the optimal time to be at the most narrow spot. Quick plan enables the user to enter the approximate location and date of the survey. Satellite data based on projected orbits can then show the user what to expect at a given time, such as the maximum number of satellites, what direction and elevation they are in the sky and what kind of PDOP (Position Dilution of Precision) values to expect. Since the narrow canyon made for a small “sky window,” we planned to be in the worst section when we had the best satellite constellation for our window. This worked out well, and we were able to get desirable results.
We made it to the Roaring Springs area at dusk as a light rain began to fall. We camped in an empty house that had been home to the pump-house operator for more than 20 years before his job was replaced with an automated system that could be controlled and monitored by staff on the South Rim via microwave communication. The old swing set and horseshoe pit were reminders that he had raised a family down there before retiring to Prescott and becoming a successful artist.
Roaring Springs, the source of Bright Angel Creek, is one of about six places in the Grand Canyon where water gushes out of a big hole in the cliff face. We scrambled--and sometimes crawled--400 feet up the base of the cliff. There, we found a cave opening sealed by a locked steel door the NPS had installed to keep out adventure seekers. A grate with the 6-inch waterline sticking through it allowed most of the water to cascade down into the headwaters of Bright Angel Creek below. When our park-service escort opened the door, we were completely awed by this river flowing from the darkness within the sheer rock wall. We recorded its position and headed back down--but not before tasting the cool, clean water filtered by thousands of feet of sandstone. It was by far the best water I’ve ever tasted.
After donning our flight suits, the helicopter flew us on a 10-minute trip out of the canyon and back to the South Rim where our adventure had begun more than six days, 20 miles and a couple blisters earlier.
Once back on the rim, we spent several weeks mapping the assets in Grand Canyon Village and other improved areas within the park boundary, including the village’s visitors centers, campgrounds, hotels, employee housing, schools, a hospital and NPS administration offices, maintenance and ranger facilities. It was important to collect the bulk of the data before the busy tourist season began Memorial Day weekend, after which the roads would become busy with thousands of daily visitors.
While collecting information on these assets, care was taken to match the names of valves, fire hydrants and sewer manholes with construction plans the NPS had on file at the park. In all, we mapped more than 3,000 point features at the park and recorded attributes for each feature such as size, type, condition and other unique data. Included in the mapping were all sewer cleanouts 4 inches in diameter and larger for the hundreds of buildings and campground comfort stations. We mapped the perimeters of wastewater septic fields as area features enabling square-footage calculations to be made.
With the fieldwork done, I returned to the office to reduce the data set and improve the precision of the GPS position data in order to achieve the submeter positions required by the contract. Using Trimble’s Pathfinder Office software, I applied a differential correction to the autonomous field positions using select reference stations from CORS.
After initiating the retrieval of the data files and holding the CORS record positions, the baselines were processed and a final position for each feature was established. An automatically generated differential-correction report indicated the accuracies of the final positions. By applying these corrections to data from conscientious fieldwork, it was easy to achieve subfoot accuracies. For example, the report indicated that one of the daily files contained 292 positions with 94.5 percent falling within the 0-15 cm range, 4.8 percent within 15-30 cm and 0.7 percent within the 0.5-1 m range. The corrected features were then exported in ESRI (www.esri.com) Shape files and sent via Internet to the PBS&J GIS Department in Virginia where they were incorporated into the geodatabase.
With this database, the NPS has already begun to plan and schedule necessary repairs to this critical water resource. The agency now has precise locations of all utilities equipment and features as well as survey information that enables it to develop accurate utility base maps. The NPS plans to ultimately tie the data to a utility GIS to assist in systems management.
From the stark beauty of the steep gorges and canyon walls to the surprisingly cold rivers and tributaries, the Grand Canyon survey expedition proved to be a spectacular six-day expedition through one of the world’s most impressive natural wonders. It was an arduous though personally satisfying adventure that gave each of us a great appreciation for Mother Nature’s force and for lightweight equipment. Our memories are still clear, and we look forward to future surveying challenges, though perhaps without the scorpions.