The bottom line … The first Ascente Final Map shows residential construction on a fault identified by the Nevada Bureau of Mines. It is commonly called the Galena Creek Fault. It is drawn as a dashed line.
There’s a lot more to the story, but the county should be concerned that they have accepted a misleading Geotech report for this project.
- NNV1 Partners: developer
- Toll Brothers: builder
- Lumos & Associates: Civil engineering firm
- Gasch Geophysical Services: Soils engineering
- Fred Saunders: Consulting geologist
- A Lumos civil engineer selected the trench locations. Lumos dug the trenches. These trenches were poorly located, poorly dug, and poorly documented.
- Gasch used seismic testing to determine the structure of the underground rock formations for the purposes of grading. The testing is conducted with a line of vibration sensors and an impact device. It is called a “refraction seismic line” (RS). The results may also detect an earthquake fault. The RS line locations were selected by Lumos.
- Fred Saunders reviewed the work performed by Gasch and Lumos
The graphic below shows the Ascente Tentative Map superimposed on the fault map using Photoshop Elements. The maps used had consistent North-South orientation. The maps were superimposed using the end of Fawn Lane and the end of Shawna Lane as reference points. See the attached file for the reference materials.
Notes from the graphic
Note-1: Gasch found a fault indication on RS-4. “ … corresponds well to the fault trace previously mapped to this area.” Saunders said “it could be reinterpreted”, but concluded that Lumos should take a core sample to find out. No core sample was taken.
Note-2: Trench 3 is very close to the GC fault. Saunders reported that no fault was found, but there appeared to be fault debris in the trench and in the soil that was excavated.
Note-3: Trench-4 showed evidence of a fault. It was dismissed by Saunders as “too old”, but this is implausible.
The “NEW FAULTS” are ones discovered by the Lumos trenching.
- The first final map of 5 home sites appears to be situated on top of a major fault identified by the Nevada Bureau of Mines.
- The Geotech report submitted by Lumos is inadequate in every way. The trenches were not located by a geologist who would know what to look for. The trenches were not dug to industry standards and were not documented (“logged”) to professional standards.
- Lumos did not follow up with additional core samples or trenches at locations where there was evidence of the Galena Creek fault.
- The “known fault” at the north end of the property may extend into the property. No trench was dug nor core sample taken to locate the end of this fault.
- The northern end of the “new fault” in Donner Village was not found. It may extend further into the development.
The deficiencies in the Geotech survey were reported in to the County Engineer and Planning Manager in December of 2017. The local geologists that authored this letter received no reply.
The developer has an incentive to minimize the faults found on the property so as to be able to build the maximum number of homes. The engineering company is paid by the developer. The geologist is paid by the engineering company. There is good reason to be skeptical of such a report.
Note: the complete Geotech report includes many pages of soil characteristics, foundation design, and other details not pertinent to the fault issues.