Hydrology

Representative Hydrology Projects

Text Box: OEI has performed groundwater resource assessments in Sonoma, Napa, Marin and Lake Counties. The assessments were prepared according to County planning criteria to evaluate groundwater availability, usually in areas where groundwater is believed to be in limited supply. Groundwater availability is assessed through analysis of local hydrogeology using drillers’ well completion reports, geologic maps, pump test data, and development of aquifer water balances.

Previous Groundwater Availability Projects

Groundwater Assessment for Proposed Winery, Cloverdale, Sonoma County

This groundwater study was prepared as required by Sonoma County Permit and Resource Management Division regarding water availability in Class III and IV areas where groundwater is believed to be of limited supply. The overall objective of the study is to assess the availability of groundwater from an existing well for a proposed winery. The potential impact of this proposed groundwater withdrawal on other existing wells, or future potential uses on adjacent properties that could exploit the same aquifer, was also considered.

Groundwater Assessment for Proposed Second Dwelling Permit, Calistoga Rd, Santa Rosa, Sonoma County

The well was located in on the alluvial plain adjacent to an unnamed tributary to Rincon Creek, Santa Rosa. The report was required by the PRMD for proposed development of a second dwelling unit on the subject parcel The hydrogeology of the parcel was inferred from well logs and surface geology. Likely recharge rates were calculated and compared to maximum potential domestic and vineyard development that could depend on this aquifer.

Bachelor Valley Pond/well Hydrologic Impacts, Lake County

We assessed the potential impacts of shallow groundwater withdrawal from an existing agricultural pond in Lake County, on nearby domestic wells. Based on field observations and geologic maps, the general character of the aquifer and the potential effect of water utilization were assessed.

Groundwater Assessment for Proposed Vineyard and Winery, Alexander Valley

Hydrogeologic conditions in the vicinity of the project were described based on available maps and well logs. The available information was then synthesized to characterize aquifers and the impact area. Water supply and potential demand for water in the project area and the potential that the proposed use may impact groundwater supplies available on adjacent parcels were also assessed.

Groundwater Assessment, Wildwood Mountain Road, Santa Rosa, Sonoma County

The well was located in an upland area of the Sonoma Volcanics, near Oakmont, Santa Rosa. report was required by the PRMD for the proposed development of a second dwelling unit on the subject parcel. The hydrogeology of the parcel was inferred from well logs and surface geology. Likely recharge rates were calculated and compared to maximum potential domestic and vineyard development that could depend on this aquifer.

Groundwater Assessment, Long Valley, Lake County

This groundwater assessment was intended to provide information for Department of Public Works, County of Lake, regarding potential effects of proposed development of a private water skiing reservoir. The scope of this environmental assessment was limited to hydrology, focused on potential project impacts on groundwater resources.

Hydrogeological Report for Second dwelling, Cloverdale, Sonoma County

A hydrogeological report was prepared for a second dwelling permit in Cloverdale. The well was located adjacent to Cherry Creek, on the alluvial plain. Site hydrogeology and aquifer conditions were determined from available geology maps, drillers logs, and pump test data. Groundwater yield and recharge rates were estimated from annual runoff and precipitation rates, and compared to expected water use.

Salmon Creek Water Availability Assessment, Sonoma County

Water Right Application-Water Availability Assessment/Cumulative Flow Impairment Index Report prepared for review by California Division of Water Rights. Assessed the significance of an existing diversion for public water safety supply on instream flows and anadromous fish habitat. USGS stream gage record and water rights records for Salmon Creek were used to determine water supply and expected demand.

Mainstem and North Fork Elk River Hydraulic Analysis

Utilizing cross section and longitudinal surveys as well as detailed discharge records, OEI has conducted several 1-dimensional hydraulic analyses of Elk River and its two tributaries, North Fork and South Fork. By varying input parameters in model runs, the sensitivity of channel conveyance (or water depth) to changes in discharge and roughness coefficients was examined. Roughness from vegetation and woody debris was intensively evalutated. These hydraulic analyses have been used to support litigation defense as well as for submittal to the state regional water quality control board.

Sulphur Creek Water Availability Assessment, Mendocino County

Water Right Application-Water Availability Assessment/Cumulative Flow Impairment Index Report prepared for review by California Division of Water Rights. Assessed the significance of an existing diversion for public water safety supply on instream flows and anadromous fish habitat. Water rights records for Sulphur Creek were used to determine water supply and expected demand.

Hydrologic and Hydraulic Assessment, Pruitt Creek, Mendocino County

Flood frequency and channel flow capacity were analyzed to evaluate the spatial extent of regulatory jurisdiction adjacent to the channel of Pruitt Creek, a tributary of Big River, Mendocino County. Maximum likely water elevations and peak discharge were estimated based on a surveyed a channel cross-section, plus watershed drainage area and elevation data. Flood elevations at the cross section were determined using USGS and USDA models.

Reservoir Management Plan, Redwood Valley, Mendocino County

Monitoring data for stream flows, rainfall and reservoir water levels, were collected and analyzed to develop a management plan for a large reservoir for vineyard irrigation. The plan included preservation of minimum flows for fish habitat in the receiving creek, and controlled releases during high flow events to mimic the natural hydrograph. Work required to comply with regulatory enforcement by CDFG and NCRWQCB.

Assessment of Potential Hydrologic Effects, Timber Harvest Plan and Conversion, Little Creek and Buckeye Creek, Gualala River Watershed, Sonoma County

The proposed project would convert approximately 16 acres of timberland to vineyard. The report addressed the reduction in canopy interception and evapo-transpiration changes water delivery to the soil, the affect of likely run-off increases on erosion potential on the road surface, poorly-maintained road cut/fill banks, and onsite vineyard roads, and the affect of increased summer and winter flows on fluvial geomorphic characteristics (stream channel and banks) of Little Creek and its tributaries, and what effect will this have on steelhead habitat resources in Little Creek. Analyses submitted in support of a project EIR.

Water Availability Analysis and Cumulative Flow Impairment, Floodgate Creek, Navarro River, California

Report was prepared for the California Water Resources Control Board Division of Water Rights for an existing reservoir located on a drainage swale tributary to Floodgate Creek, Navarro River watershed. The analysis includes calculation of the Cumulative Flow Impairment Index (CFII) of Floodgate Creek directly above its confluence with the Navarro River, and at two other “Points of Interest” (POI’s).

Floodplain Impact Evaluation

Flood levels for the 10, 25 and 100 year floods were modeled for a proposed project on the 100yr floodplain of Sonoma Creek using the 1D hydraulic model HEC-RAS. Flooding was evaluated in relation to both the Sonoma Creek floodplain and a small stream crossing the site.

Assessment of Hydrologic Effects of Proposed Vineyard Development, Napa County

Report addresses hydrologic, erosion and sedimentation, and cumulative effects issues pertaining to a proposed vineyard development, on the mountain uplands of western Napa County. Potential on-site hydrologic effects assessed include changes in infiltration, runoff, erosion and sediment yield, water yield, and groundwater. Potential off-site effects assessed included watershed hydrology from conversions in York Creek over the past 20 years, and estimated increases in water yield per unit area and contribution to increased peak flow downstream. Potential impacts to salmonid habitat in York Creek, the Napa River, and the Napa Estuary were also assessed.

Assessment of Potential Hydrologic Effects of THP and Conversion, Alder Creek and Brush Creek Watersheds, Mendocino County

This report summarizes the findings of potential hydrologic effects of a proposed Timber Harvest Plan/Conversion in western Mendocino County. The proposed THP would convert approximately 250 acres of timberland and grassland to vineyard and orchard.

Urban Stream Assessment Report, Oakland, Alameda County

A headwater channel on the Oakland hills, was surveyed and a creek assessment report was prepared under City of Oakland’s urban creeks ordinance to determine set backs and mitigation requirements.

Timber Harvest Impact on Runoff and Flood Potential

OEI assessed potential changes in the extent of local flooding associated with a proposed THP. Potential remedial actions that could reduce runoff and improve drainage in the project area were also discussed. An empirical hydrologic model derived from the Caspar Creek watershed experiment was applied to the project area.

Text Box: OEI has conducted investigations of surface waters and groundwater at many sites and project scales in northern California and the Pacific Northwest. Typical investigations evaluate project impacts and land management on runoff rates, flood potential, and hydrologic budgets. Areas of specialization include effects of timber harvest on hydrologic processes, channel capacity and flood studies, and water availability analyses for water rights and wells.

Please scroll down to read about our experience with groundwater availability studies

Office Location: 447 Hudson St. Mailing Address: PO Box 794, Healdsburg, CA 95448 Ph (707) 431-2810 Fax (707) 473-9050

O’Connor Environmental, Inc.

Geomorphology ▪ Hydrology ▪ Engineering Geology

P.O. Box 794, Healdsburg, CA 95448 (707) 431-2810