Feeling Steamy at Calaveras Dam

Among many other fascinating geological features present at the Calaveras Dam project site, a geothermal steam vent has recently been exposed during construction. Although typically associated with volcanic activity, steam/gas vents are also frequently found near large active faults, like the Calaveras fault, which is within 1/4 mile of the project site. There is also evidence of past geothermal activity in the vicinity of this vent. As seen in this photograph, there are areas of hydrothermally-altered bedrock (gray sandstone stained yellow) and holes where former vents, now dormant, were once active.

The construction team continues to monitor the temperature and the gaseous emissions of the present feature, and has created a cautionary exclusion area around it, but, as seen in this video, there has been no adverse effect to construction activity. We will keep you posted on our findings!

Local Cavers and the New Irvington Tunnel

They kindly attended one of our meetings, and we, in turn, attended their’ s. We were delighted to meet members of the National Speleological Society’s San Francisco Bay Chapter (SFBC) at one of our quarterly coffees in Fremont a while back.  Much to our surprise, they saw our New Irvington Tunnel (NIT) blog and became interested in the project. They invited us to speak at one of their future meetings about our man-made ‘cave’. Last week Project Manager David Tsztoo and Geologist Rebecca Fusee made a presentation at the SFBC general meeting and  ‘rocked out’ as it were by talking about the NIT Project and the complex geology it passes through.

The members of the SFBC Grotto sure know a thing or two about cave exploration, geology, conservation and organizing caving trips with fellow cavers. It was a great experience for our team to have the opportunity to share knowledge about tunneling with this group. Beautiful photos and rock samples were shown of the geologic features from the tunnel excavation, consisting of primarily sandstone, siltstone, shale, and chert ranging from Miocene to Cretaceous age (dated at 5 to 144 million years old).  Action photos of our road header equipment used in tunneling were featured during the presentation.  We look forward to more talks about rocks with the SFBC!

To learn more about the National Speleological Society San Francisco Bay Chapter, visit their website at www.sfbcgrotto.org

For more information on the New Irvington Tunnel Project, subscribe to our blog, or call our 24 hour answer line at 866-973-1476 or email mle@sfwater.org

New Irvington Tunnel Project Geologist Rebecca Fusee

shares some rock samples from the tunnel with attendees

L to R: John Tinsley, Tom Mathey, NIT Project Geologist Rebecca Fusee, NIT Project Manager David Tsztoo, Alan Chern, Matt Bowers