1) Plan of Work: United States Geological Survey Seismic Imaging Study in the Cities of Reno and Sparks, Nevada, June 2009
Version May 21, 2009, Contractor: John N. Louie, Prof. of Geophysics, Nevada Seismological Laboratory, University of Nevada, Reno; , office 775-784-4219, fax 784-4165, cell 229-3835
To better understand earthquake hazards in the City of Reno and along the Reno-Carson City Urban Corridor, the United States Geological Survey (USGS) is preparing to undertake a high-resolution, non-invasive, seismic imaging study of the Truckee Meadows Valley. The purpose of this investigation is to get a clearer picture of subsurface soil and rock layers including faults and folds that influence earthquake ground motions. The subsurface target zone is in the 100-to-3000 foot depth range. The anticipated time frame to acquire these data will be about 10 days beginning on or about June 8, 2009.
Motivation and Outline of This Study
A primary objective for the U.S. Geological Survey's National Earthquake Hazard Reduction Program in Nevada is the development of a realistic earthquake-hazard map for the Reno/Carson urban corridor. The Survey expects to spend as much as a million dollars of Federal funds over the next few years to study our urban area. Scientists at the University of Nevada are receiving some small Federal grants to collaborate in these studies. The objective this June for the Geological Survey's field crew is to image potential earthquake faults in the geologic basin underlying Reno and Sparks, and to better characterize the basin itself.
The USGS/UNR survey work will take place from June 8 through 18. Survey work, during daylight hours only, will extend along the River west from Rock Blvd., through downtown, to Keystone Ave. or Booth St.; and also for a few miles along Manzanita Ln. west of Virginia St. They surveys will be full-scale seismic reflection soundings as are done for oil and gas exploration. A seismic vibrator with a 700-lb reaction mass, mounted on a 1-ton pickup will induce seismic waves in the ground. The waves will be recorded by coffee-cup-sized sensors planted in turf or pavement joints on 4-inch spikes. The sensors are connected by about a mile of cable, which will be placed in a cable guard where it must cross traffic. The truck-mounted vibrator will creep about 1 mile per day along the River path, street parking lanes where they can be closed temporarily, and traffic lanes only where necessary. No single location will be obstructed for more than a few hours. The 700-lb vibrator has been tested for years in California and Utah, and only damages pavements very rarely. The USGS and UNR will repair any damage caused by the survey. All survey results will be scientifically vetted and publicly available.
This Federally sponsored work will collect some of the information needed to make the earthquake hazard map. Earthquake-hazard parcel mapping, as is being done now in Clark County, is another crucial component of the hazard map. The U.S. Geological survey has so far been unable to provide funds for parcel mapping anywhere in the country.
General Location of Seismic Profiles
The seismic surveys will take place along two routes totaling about 7 miles in length: the River profile; and the Mazanita profile. Attachment 1 on pages 9 and 10 below shows maps of the routes.
Some additional locations will be occupied as well, for additional recording activities.
The proposed River seismic profile location is shown on the map as the yellow line with red waypoints. Acquisition along the Truckee River Path will extend west from Rock Blvd., run along Mill St. between Museum Dr. and Sierra St., along Island Ave, and then along the River Path to Booth St.
The proposed Manzanita seismic profile location is shown on the map as the yellow line with red waypoints. Acquisition will extend west from Virginia St. initially along Redfield Pkwy., to Manzanita Park at Baker Ln., then west along Manzanita Ln. to West McCarran Blvd.
Figure 1a. Minivibe vibroseis truck operating along street in Santa Rosa, California, in October, 2007.
Data Acquisition Process – Roadway/Street Operations
We will use the vibrations generated by a rubber-tired “minivibe” vibroseis truck (Figures 1a and 1b) as the seismic source. This seismic source is preferred in urban situations and on roadways over other traditional seismic sources, such as explosives, because a) the source energy is spread out over about a 12 second interval rather than being released all at once, and b) the source is non-invasive, operating on the ground surface without the need for drilling or excavation. This vibroseis truck will drive along the entire profile route stopping at 15-ft intervals to put a 4-ft diameter polyurethane pad on the ground surface. Part of the truck’s 14,000-lb weight is put on the pad and the pad is vibrated for about 8-12 seconds. This 8-12 second vibration “sweep” is repeated 4-10 times at each stop, then the truck is ready to move up to the next station after about a minute. The audible noise from the vibroseis truck is about the same as a garbage truck operating in a neighborhood.
Figure 1b. Minivibe vibroseis and USGS recording vehicle (1-ton truck with camper) operating along residential street.
Figure 2. a) Placement of the ground motion sensor (geophone) in the joint between curb and sidewalk. b) Sketch of 5/16”-diameter hole drilled 1” into concrete for geophone placement. Hole will be backfilled with epoxy when completed.
During generation of the seismic signal, ground vibrations may be felt in the vicinity of the truck and up to about 200 feet away at a maximum level of 0.04 in/sec at about 20 Hz. These vibration levels are about 10 times lower than the peak particle velocity damage thresholds set by the U.S. Bureau of Mines (see section (3) “Impacts to pavement and utilities”).
The vibrations generated by the truck are detected and recorded by sensitive “geophones” placed every 15 feet along a cable that stretches for 3/4 mile in front of the vibroseis truck. The geophones are about 4 inches tall with a 2-inch steel spike that is pushed into the soil off the edge of road to firmly couple the sensor to the ground. Where there is only concrete or asphalt, a 5/16”-diameter hole will be drilled 1” deep into the joint between the curb and adjoining pavement (Figure 2). The geophone will be placed in this hole during data acquisition, but then will be removed at night. Holes in concrete or asphalt will be back-filled with caulk/epoxy after use.
As the vibroseis truck moves along, the geophones and cables are also moved up to record ahead of the vibroseis truck. The average speed of the vibrator truck during this data acquisition process is about 0.3 miles/hour. We anticipate that the vibrator truck will be in operation for about 10 days (8 hours/day) between 8 am and 6 pm, along the route. In addition to the vibrator truck, there will be 2 other 3/4-ton pickups, and one 1-ton pickup. Personnel from the USGS will be with the equipment at all times and ready to answer questions from the public and give out information regarding the survey. After the survey is complete there will be little evidence of our work at the site.
2) Excavation Plan:
Because all equipment used for this study are non-invasive and mobile, no excavations are required to complete this work.
3) Traffic Control:
Figure 3 below shows our Traffic Control Plan along typical roadway for the vehicles involved in the USGS seismic imaging study along this route.
Operation of the vibroseis truck
The vibroseis truck, which is 20-ft long and 7-ft wide, will operate in the parking lane or along the road shoulder while operating along city streets, as shown in Figure 3.
Figure 3. Typical position of the vibroseis truck operating in the parking lane or on the shoulder along SR 147.
In this position the truck will not be in the traveled way and traffic will flow freely. The vibroseis truck will work along the shoulders but may at times be required to partially encroach onto the eastbound lane.Tall 28” cones, a large flashing directional arrow board,orange 1-meter square “Survey Crew Ahead” signs and high-intensity warning flashers mounted on all vehicles will be used to alert oncoming traffic of our activity. All USGS and UNR personnel will be wearing safety orange or green vests or shirts.
Operating the vibroseis truck during data acquisition is a semi-mobile process involving a continuous sequence of 1-minute stops followed by a truck move of 15 feet east along the roadway. To alert motorists and bicyclists in advance of the vibroseis truck work area, the truck will have a flashing yellow double beacon mounted on top, a “slow-moving vehicle” triangle mounted on the back of the vehicle, 4-way flashers, plus headlights, and a bright flashing arrow board (in caution mode) operating at all times mounted on rear of the truck. The “Survey Crew Ahead” warning signs will be placed about 100-200 yards behind and ahead of the vibroseis truck to alert drivers and bicyclists in both directions. Because the operation moves slowly (less than 1 mph), the stationary signing will be periodically retrieved and repositioned in the advance warning area.
Placement of the cable and sensors
For several hours before starting the vibroseis truck we will be laying the cable and sensors along the south edge of the roadway. To drop the cable along the roadway we will likely use a 3/4-ton white USGS-marked pickup, equipped with flashing yellow double beacons and strobed taillights/front turning lamps, moving along in the direction of traffic within the parking lane or along the road shoulder. Cable laying along portions of bikeways will employ officially marked 4-wheel ATVs. Cable and sensor installation is done by 5-8 workers wearing safety orange vests or shirts. To alert pedestrians and autos to the presence of the cable and sensors at cross-traffic areas, fluorescent traffic cones will be put down. The cable will also be tucked against the curb when present so as not to impede pedestrian traffic. When crossing streets, bikeways, or pedestrian traffic areas, the cable will be covered by a 1-inch-high rubber guard, which is taped to the pavement. The rubber guard is taped down at intersections so as not impede the flow of traffic on the streets or restrict access to businesses and residences.
Impact to Pavement and Underground Utilities
We expect no damage to any pavement or underground pipe or structure. We have conducted over 100 miles of these types of surveys in a variety of urban conditions with over 40,000 vibration points and caused no damage to above- or below-ground structures or pavement. In fact, when the vibroseis truck operates on city street pavement, there is no marking, denting, or scratching of the pavement surface. This absence of damage suggests completely elastic behavior of the soils and pavement around the vibroseis source pad. The vibroseis truck we will use operates on the ground surface and involves no excavation. In addition, in contrast to impact or explosive sources, the vibroseis source energy is spread out over 8-12 seconds thereby decreasing the impact on the built environment. Buried pipes and other below-grade structures are constrained by the surrounding soil and move in the same manner as the surrounding material during a vibration episode. In contrast, structures located above ground, are relatively free to respond in a manner different from the ground upon which they are built: they could amplify or attenuate the input ground motions. Buried pipelines will withstand vibrations well in excess of the U.S. Bureau of Mines (USBM) recommendations for above ground structures, and the expected vibration levels in our study near the vibroseis truck will be well below the USBM criteria. For example, in a study of the vibrations from six, 25,000-lb vibroseis trucks operating simultaneously on Los Angeles streets for several years in the 1970's, there was only one instance of minor damage to a home and the generated strains throughout the surveys were far less than those from environmental sources (Oriard, 1994). We are also aware of the results of vibroseis operations in the city of Santa Monica, Calif., in 2000. In that case, a single 30,000-lb vibroseis truck operated on city streets for several days without damage to infrastructure. For this study we will use only one, 14,000-lb vibrator, so the strains and vibrations will be far less than those described for the work in Los Angeles. For an additional common-sense measure of precaution, we will not operate the vibe directly over manhole covers, sewer grates, or directly over any marked utility line.
Oriard, Lewis L., 1994, Vibroseis operations in an urban environment: Bulletin of the Association of Engineering Geologists, v. 31, no. 3, p. 343-366.
4) U.S. Government Legal Provisions Concerning Liability (Bonding) and “Hold Harmless” agreements:
Because of the peculiar nature of the United States Government, its employees and agents may act only in the manner set forth in statutory mandates. As a result, in several instances it is unable to "contract", or enter agreements in the conventional way. One such peculiarity is that an agency cannot enter into "hold harmless", or "indemnity" agreements on behalf of the Government unless specifically authorized, since such an agreement would seem to amount to an agreement for an expenditure and/or liability which might arise in the future. This may be interpreted or construed as a commitment or obligation of funds prior to appropriation by Congress, which is prohibited by statute. (31 U. S. C. § 665; California Pacific Utilities Co. v. U. S., 194 Ct. Cl. 703 (1971)) Consequently, a substitute provision, set forth below, tailored to fit the Government's statutory restrictions, provides essentially the same protection a landowner would seek under a "hold harmless" agreement. It states that the Government promises to perform the work with all reasonable diligence and precaution. Failure to do so could be considered a breach of contract, which could be disposed of under the Tucker Act. (28 U. S. C. §1490) Also, the Federal Tort Claims Act (28 U. S. C. § 2671) provides a recourse against the Government for negligent acts or omissions of employees resulting in injury or damage.
The Survey agrees that the (construction, installation, maintenance and use) of the (structures, appurtenances, equipment, and tools) on the lands (of the Landowner, lessee, etc.) on which they are (used or installed) shall be effected with all reasonable diligence and precaution to avoid damage to the and, property, or personnel of the (Landowner); further, the Government agrees to cooperate, to the extent allowed by law, in the submission of claims pursuant to the Federal Tort Claims Act against the United States by third parties for personal injury, or property damage resulting from the negligent act or omission of any employee of the Government in the course of his employment (28 U. S. C. §§ 2671, et seq.).
Another aspect peculiar to the United States, is the question of insurance. Although in a sense the United States has been referred to as being "self insured", it does not take out or carry liability insurance, but disposes of its liabilities under the Federal Tort Claims Act. It has been held that a government agency, absent specific statutory authority, cannot purchase insurance (19 Comp. Gen. 798). Thus, the United States cannot produce a certificate of insurance when requested: however, all proper claims will be disposed of under the Federal Tort Claims Act. In conjunction with this, the Government can require its contractor, if any, to provide a certificate of insurance to cover the contractor's activities during the course of a specific project.
What Is A Tort Claim?
There are two types of Tort Claims. The first and most common is a tort claim filed against the United States (SM 451.1.1). These claims involve property losses, property damage, personal injuries and deaths alleged to have resulted from the negligent or wrongful acts or omission of employees of the USGS in the course of their duties. The second type of tort claim is one filed by the Government (SM 451.3) to recover for damages to Government property under the USGS jurisdiction.
Who Is Responsible for Assembling/Forwarding Tort Claims Against the Government?
Usually the responsibility for assembling and forwarding Tort Claims resides with a member of the Administrative staff within the District, Field, Team or Center office where the USGS employee or Government property resides. Although assembling the claims may be the responsibility of the Administrative staff, employees and supervisors are responsible for providing certain pieces of information to make the claim complete.
What Is Required To Forward A Tort Claim Against The Government?
When dealing with claims against the Government, the claimant is responsible for initiating the claim, however, they often need information to get started. It is appropriate for the USGS to inform claimants that they must submit a complete Standard Form (SF-95) - Claim for Damage, Injury, or Death to the District, Field, Team or Center office that is responsible for forwarding the complete claim package. Be careful during conversations with claimants not to provide an opinion on the validity of the claim. Once the claimant has submitted the SF-95, the following information is required before the Tort Claim can be forwarded for review and processing:
1) A memorandum summarizing the claim. This memorandum should contain information about the accident or incident such as the location and date, the name of the USGS employee involved, and any additional information that may be helpful to the reviewer.