Jodi Frediani is the Executive Director of Citizens for Responsible Forest Management (CRFM) and the Chair of the Forestry Task Force of the Sierra Club's Ventana Chapter.  We're still not sure what exactly are the qualifications for these titles.

January 25, 2004

By JODI FREDIANI  

From: JodiFredi@aol.com
To: Jonathan.Ambrose@NOAA.GOV, CBerry@ci.santa-cruz.ca.us
Cc: PANDERSON@dfg.ca.gov, mbaldzikowski@ci.santa-cruz.ca.us,
Barkfeld@rb3.swrcb.ca.gov, PLN714@co.santa-cruz.ca.us,  kaue@dfg.ca.gov
Subject: San Vicente Sinkhole
Date: Sun, 25 Jan 2004 09:28:57 -0800

Jon and Chris,

Just thought you might be interested in the following tidbit I unearthed quite by accident at the Felton CDF office. That is, if you haven't already heard.

I found a Notice of Emergency Timber Operations dated November 7, 2003 for RMC to remove a number of trees that have fallen into San Vicente Creek.

I quote from Jerry Weber's October 17, 2003 geological report to Satish Sheth:

"At your request I have conducted a brief preliminary investigation of a large sinkhole that is forming at the confluence of the above noted creeks (Picnic Creek, a Class II trib, and San Vicente Creek)....The focus of investigation was the effect of the sinkhole formation on the water line in San Vicente Creek that provides water to the town of Davenport.  My preliminary conclusion is that if immediate action is not taken to move the water line it will be destroyed by the collapse of the sinkhole during the rainy season.....(Rachel Lather and Joe Hanna from the County participated in a site visit)

The sinkhole is forming within the coarsely crystalline limestone marble present in the San Vicente Creek drainage.  At the time of my visits the entire flow of San Vicente Creek disappeared into a narrow void (swallow hole) at the upstream edge of the area that is slowly collapsing into a subterranean void.  The collapse area is roughly circular and approximate 200 feet in diameter.  Large fissures and voids extend to depths of 15-20 feet in the center of this mass; and a portion of the bed of San Vicente Creek about 75 feet downstream from the swallow hole has dropped 5-7 feet. Approximately a dozen small to moderate sized redwood trees have already fallen in the collapse area and perhaps a dozen more redwoods and alders are experiencing various degrees of tilting and deformation.  Picnic Creek the small tributary that enters San Vicente Creek at the collapse area disappears prior to reaching the edge of the collapse area.  Finally, although ! I have made no detailed measurements, it is clear that between

My first and last visit (seven days) the collapse are has increased in size and deepened."

The emergency notice includes cutting a cable corridor to access the trees and rerouting the water line along the other side of San Vicente.  One can assume the water supply to Davenport (the intake is just upstream of the sinkhole) is no longer in jeopardy, but what about the downstream fish?

And possible groundwater contamination?  Thayer Road is just a stone's throw from the sinkhole (well, say 1/2 mile.) I'm told that such underground flow can exacerbate other karst formations, hastening further collapse.

Interestingly, this sinkhole is in the area of the 1998 RMC timber harvest. Picnic Creek is flanked on both sides for a ways above the confluence and sinkhole by haul roads within or adjacent to the WLPZ.  I don't have the plan for that area so do not know if they conducted tractor ops, but since they were planning to put in a cable corridor to extract the fallen trees, I would assume so.

This is exactly the kind of problem Chris anticipated on the latest RMC plan where it  proposed to log along Smith Grade along Reggiardo Creek.  Chris was concerned for the City of SC water supply as that area is also underlain with karst. After a bit of a battle, we were successful in getting RMC to remove that area from their THP. But the whole mountain seems to be swiss cheese. What about the potential for additional collapse in the area of the recently approved 750 acre RMC THP upstream of the town of Davenport water uptake?  If the streams have gone subterranean, does anyone know if the water is resurfacing downstream?  And at the same flows as above the sinkhole?  I know there is water in downstream San Vicente, but Mill Creek enters below the sinkhole area.

And how might this affect RMC expanded water drafting plans?

Just thought you might be interested,

Jodi  

Click here to read what Jerry Weber thinks of Jodi Frediani's nescient comments. Jerry Weber is a professor of field geology at UCSC and has been a consulting hydrologist for 31 years