May 29, 2003

Director

California Department of Forestry and Fire Protection

1416 Ninth Street

Sacramento, CA 95814

Subject: Evaluation of Potential Hydrologic Effects

Negative Declaration for THP/Vineyard Conversion, Artesa Vineyards

Annapolis, California

Dear Director:

The purpose of this letter is to present comments on project evaluations and conclusions regarding impacts to hydrologic conditions in the Grasshopper and Annapolis Creek watersheds associated with the Fairfax Timber Harvest Plan and (Vineyard) Conversion, Number 1-01-171 SON. This letter focuses on the materials presented in the following documents:

1. “Assessment of Potential Hydrologic Effects, Fairfax Timber Harvest Plan and Conversion Number 1-01-171 SON, Grasshopper Creek and Annapolis Watersheds, Sonoma County; prepared for the Natural Resources Management Company, Calpella, California by O’Connor Environmental, Inc., Healdsburg, CA, and dated March 15, 2002 (hereafter referred to as O’Connor report).

2. Erosion Control and Mitigation Plan, Fairfax Ranch Vineyard, Annapolis Road, Annapolis, CA, prepared for David DiPero, Grower Relations, Artesa Vineyards and Winery, Napa, CA by Erickson Engineering, Inc., Valley Ford, CA, and dated March 27, 2002 and associated design/documentation materials submitted to various state and county agencies (hereafter referred to as the Erickson report).

Many of the data, assumptions, site characteristics, and conclusions regarding potential impacts to local and watershed hydrologic conditions are incorrect and/or misleading in these reports. Because these documents do not accurately evaluate the potential impacts to hydrologic conditions, the project should be reevaluated, requiring the preparation of an Environmental Impact Report (EIR) in order to correct these deficiencies. The rational for these statements are presented below.

Anticipated Changes in Seasonal Runoff and Minimum Summer Flows

A central premise applied throughout the O’Connor report is that project impacts on hydrology can be predicted based on hydrologic research conducted in the Casper Creek watershed that included measuring changes in runoff quantity and patterns associated with differing logging practices. This analogy was applied because of the close proximity and similarity between the project site and Casper Creek watershed and the planned clear-cut logging associated with vineyard conversion. The O’Connor report states,

“In summary, watershed experiments at Casper Creek indicate substantial increases in annual water yield, summer minimum flows, and storm runoff following clear-cut harvest in the North Fork Casper Creek.” The report continues with, “Increased summer minimum flows result primarily from reduced growing-season evapotranspiration and higher soil moisture. The increased trend in these parameters and the approximate magnitude of change is likely to be similar for conversion of forest to vineyard as the project site near Annapolis.” This statement is followed with, “Hence, it can be stated with relatively high certainty that the proposed project is not likely to reduce dry season flows.”

There are several significant problems with this reasoning, which call into question the conclusion that the project will not adversely impact local hydrologic conditions. First, the conclusions presented in the O’Connor report are based primarily on the hydrologic responses presented in the E.T. Keppeler report ¹which document summer flow and water yield responses to different timber harvest practices in the Casper Creek watershed. The O’Connor report represents some of Keppeler’s data and concludes that there are increases in total annual yield and “summer minimum flows” in the post-logged period when compared to the pre-logged records. Although this is true for the 7-8 year period following logging, what the O’Connor report fails to present is that over this period, the yield and flow estimates recede back to pre-logging levels and that minimum summer flow rates average 10% lower than pre-logged conditions for the period 8-15 years after logging in the South Fork Casper Creek watershed. However, the O’Connor report makes no mention of the potential for long-term decreased summer base flow rates as a result of project deforestation.

Secondly, although the hydrologic responses to deforestation may be well understood, the validity of comparing the project site to Casper Creek is flawed in that the post-logging land use practices will differ significantly between these locations. The processes that control runoff (interception, infiltration, vegetation density, evapotranspiration, soil properties, etc.) differ significantly between a vineyard and logged forest left to regeneration. The O’Connor and Erickson reports fail to evaluate if the short-term gains in soil moisture (due to logging) are offset by reduced infiltration (i.e. increased runoff) associated with vineyard conversion. In order to properly quantify the impacts of the project on hydrologic conditions, one needs to develop a detailed water budget comparing the perceived gains in available soil moisture as a result of logging against the retained vegetation water demands (evapotranspiration) and infiltration potential from the altered substrate. The relationships between groundcover type and infiltration potential are well understood as exemplified in the attached Figures. In general, these figures² demonstrate:

Increased organic cover leads to increased infiltration rates;

Areas covered in vegetation have higher infiltration rates than cultivated areas; and

Forested areas commonly have higher infiltration rates that grasslands.

Although the Erickson report states that the vineyard will ultimately be managed with a permanent cover crop having an infiltration rate similar to “historical grassed meadow conditions”, the O’Connor report makes reference to “cultivated” and “pasture” post-project conditions. In addition to the uncertainty in proposed “post-project” land cover conditions, there is no evaluation, in either report, of how runoff/infiltration/evapotranspiration rates will differ between existing forested and resulting vineyard cover conditions.

Finally, the Erickson report indicates that “diffuse sheet flow and swale flow” from approximately 20-percent or 20.3 acres of the proposed 104 acres acre THP/Conversion area will be “intercepted and conveyed by pipe” to a proposed on-site reservoir to meet summer vineyard irrigation demands. How will this system alter the infiltration potential of the affected area? Will intercepting sheet flow reduce the amount of water that otherwise would go to infiltration in this area? If so, how does this factor into the contention that the project will result in increased annual runoff yields and summer base flow rates?

Anticipated Vineyard Water Demand vs. Water Supply

The Erickson report presents a cursory water budget for the project. However, based on review of this description and readily available hydrology reports for the region, a number of potential inconsistencies and inaccurate hydrologic/meteorologic variables exist, including:

3. The Erickson report calculates a water demand based on a 17-week irrigation season, reportedly extending from June 1 to mid-October. This period, as defined, is actually 137 days or 19.6 weeks long.

4. The Erickson report estimates potential runoff based on 6-feet (72-inches) of annual precipitation. The USGS³ isohyet map indicates a mean annual rainfall total of 44-inches for the project site. The report accompanying the USGS mean annual runoff map⁴ indicates “mean annual basin wide” rainfall total of 51-inches for the South Fork Gualala River gage near Annapolis. Granted the USGS estimates are dated, but this magnitude of discrepancy is not attributable solely to differing periods of record. In addition, anecdotal accounts from Annapolis residents suggest a mean annual rainfall total significantly less than 72-inches.

5. The USGS’s mean annual runoff estimate for the Annapolis site is between 24 and 26-inches, significantly lower that the 36-inch estimate used in the Erickson report.

The runoff estimates presented in the Erickson report are not conservative estimates. Given the proposed reservoir size presented in the report, there is little if any contingency built into these estimates if irrigation demand is to be satisfied solely by runoff and storage components. It is also surprising that a dry-year runoff estimate was not generated to assist in project planning and design purposes. Thus, it is assumed from the discussion regarding groundwater pumping demands, that groundwater will be used to augment irrigation demand during periods of shortfall, which, based on the numbers presented in the Erickson report, could occur to varying degrees during 50-percent of the time. However, as discussed below, neither the O’Connor or Erickson reports demonstrate, let alone evaluate, the available water supply and safe yields that could be obtained from the underlying aquifer. In addition, won’t groundwater withdrawals negate any of the postulated benefits of increased base flow (groundwater supplied) from timber harvesting?

Evaluation of Groundwater Conditions and Supply

The characterization of groundwater aquifer conditions and groundwater flow directions in the O’Connor report are inconsistent and unsubstantiated. This has lead to an unfounded assertion that there will be no potential adverse impacts of groundwater pumping on the underlying aquifer and surrounding wells. As indicated in the O’Connor report, the project site is underlain by the Ohlson Ranch Formation, which, in turn, lies above Franciscan bedrock. However, evaluation of local geologic maps and reports along with regional geologic cross-sections indicate that the contact between the Ohlson Ranch and Franciscan Formations is essentially a horizontal to slightly eastward dipping plane, resulting in the thickest portions of the Ohlson Ranch Formation being located beneath the higher elevations of area ridges^{5, 6, 7, 8} . The sequence of geologic events that lead to this configuration is as follows. After emplacement, the Franciscan Formation, it was eroded to a relatively flat plain along the coast. About five million years ago, this surface was covered by silts, sands, and gravels of the Ohlson Ranch (Merced) Formation in what was likely a broad shallow marine embayment covering most of Sonoma County (Blake et al., 1971; Rice and Strand, 1971⁹). Following deposition of approximately 500 feet of deposits, the combined effects of a net fall in sea level and uplift of the coastal mountains led to erosion and down cutting into the Ohlson Ranch Formation. In essence, the Ohlson Ranch Formation remains today as flat-lying caps of silt-sand-gravel deposits on area ridges.

The geologic cross-section presented as Figure 3 of the O’Connor report projects the formational contact between the Ohlson Ranch and Franciscan somewhere along the west side of the section resulting in an overly steep (sloped eastward) contact. This configuration does not agree with the geologic map (Figure 2) presented in the report as the map does not indicate a surface expression of the formational contact along the cross-section alignment A-A’. Also attached to this letter is a geologic map of the project vicinity, which depicts the outcrop areas of Ohlson Ranch Formation. This figure indicates that the Ohlson Ranch is only found on ridge tops above and elevation of approximately 700 feet, and the contact with the Franciscan is generally on contour, suggesting a near-horizontal to gently eastward dipping plane of contact between the formations¹⁰.

The statement in the O’Connor report that the groundwater gradient most likely parallels the slope of the geologic contract is speculative. Groundwater flow gradients are determined from groundwater table level measurements in area wells – these data are not presented in the O’Connor report. Flow gradients are also modified by existing groundwater withdrawals – data also not quantified or presented in the report. There is no definitive analysis or evaluation presented in either the O’Connor or Erickson reports that: 1) characterize groundwater table conditions beneath the site; 2) use standard analytical methods to determine the cone of influence and amount of draw down that will occur in the underlying aquifer under project groundwater pumping conditions; and 3) complete an analysis of cumulative impacts from all local groundwater withdrawals. Based on our experience with the installation of wells and aquifer testing of equivalent deposits in southwestern Sonoma County, the relatively fine-grained nature of these deposits and the limited lateral extent can easily lead to rapid dewatering of the aquifer system, especially during the summer months, a period of natural and rapid water table recession. Given the likely dependence on groundwater supplies to meet irrigation needs of vineyard conversion especially during dry years (a period of reduced recharge and groundwater supply) the project has not demonstrated a responsible evaluation of future impacts on the groundwater supply and surrounding residential and ecological groundwater needs.

In summary, the hydrology and water development reports submitted as part of the THP/Conversion contain a number of misleading and inaccurate conclusions. They focus on how perceived changes in a discrete variables will impact the overall water balance. This is a flawed approach, as it does not consider the cumulative/net effects of additive or competing processes and variables. A proper evaluation should also account for and integrate surface water (e.g., runoff, infiltration, etc.) and groundwater (e.g., withdrawals) conditions and processes. These hydrologic processes are intrinsically linked at the project site and making statements that removing tress will lead to increased annual and summer minimum flows are inaccurate without characterizing and simultaneously evaluating the other dominant processes at play (e.g., increased runoff, reduced infiltration, groundwater withdrawals, etc.).

If you have any questions, concerns, and would like to discuss this letter, please call me.

Sincerely,

Greg Kamman

California Registered Geologist

California Certified Hydrogeologist