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Instream Management

Permit and Resource Management Department Banner 750

In addition to the major objectives set forth in Section 7.2, the following objectives apply to instream operations:

  1. Manage aggregate extraction amounts to more closely match the estimated natural recharge of gravel. Maintain a balance between aggradation and degradation that reflects the natural recharge of aggregate. This will be accomplished by managing production to remove only the net accumulation of aggregate within the channel.
  2. Provide high-quality aggregate materials.
  3. No reduction in flood channel capacity. Maintain or increase the flood flow capacity of stream channels.
  4. Reduce the potential for bank erosion.
  5. Protect and enhance biotic resources in the riparian corridor and stream channel.
  6. Minimize interference with the location and shape of the channel. No net long term downgrading of the channel. Maintain a distinct, non-braided low-flow channel.
  7. Maintain the physical hydrologic processes and bar form that provide pool and riffle habitat.
  8. Protect public infrastructure and facilities.
  9. Adjust mining methods and standards as necessary to meet objectives in response to changes in the hydrologic and biotic setting from year to year and/or site to site.

Instream Mining Objectives applicable to specific instream reaches: The following objectives apply to the Lower Alexander Valley Reach of the Russian River (River Miles 46.3 to 54.0):

  1. Operations in the lower reaches of the Alexander Valley are subject to the goals, objectives, and standards as described above and modified as follows:
  2. Reduce the potential for bank erosion in a manner that maintains or enhances riparian vegetation and habitat conditions for fish and wildlife.
  3. Avoid activities in the stream flow or below water level unless shown to be necessary to install crossings, improve aquatic habitat conditions, or provide other public benefits.
  4. Maintain and enhance opportunities for terrestrial wildlife movement.
  5. Maintain and enhance diverse riparian vegetation as necessary to protect beneficial uses. Strengthen banks along the mining reach with substantial riparian vegetation. Use bioengineered measures to improve bank stability and minimize bank erosion only where sufficient riparian zones cannot be established or to protect facilities. Encourage joint participation of landowners and other funding entities for such work.
  6. Maintain a confined channel with complex margins along the riparian zone. Avoid disturbance of existing mature riparian vegetation. Where disturbance of riparian vegetation is shown to be necessary for mining operations and/or reclamation, replace/replant vegetation that provides equal or better habitat than existed prior to mining. Onsite is preferable to offsite replacement.
  7. Prior to the first year of mining carry out a baseline survey of the mining reach and up and down stream non-mining areas to establish baseline elevations at established cross-sections and thalweg elevations at each pool and riffle crest. Manage extraction to assure that :
    1. The average thalweg elevation at the riffle crests for the entire mining reach does not drop below the average pre-mining thalweg elevation; and
    2. the actual thalweg elevations at the riffle crests downstream of each mined bar does not drop more than 2-feet below pre-mining elevations; and
    3. residual pool depths at each pool is maintained or increased.
  8. Manage extraction so that the pre-mining minimum baseline reference elevations are maintained at each mining site. Limit annual extraction to 1-foot above the baseline elevations or the specified elevations approved by PRMD in consultation with the Scientific Review Consultant team and resource agencies.
  9. Manage extraction so as to minimize disturbance to physical processes that maintain channel geomorphology and provide aquatic habitat. Retain to a large extent the topographic attributes of gravel bars including a robust bar head strong enough to withstand the typical annual in-channel flows. Mining is only allowed downstream of the horizontal apex of the bar (or the lower half of the bar where no apex is apparent) with an exception to allow mining in the upper half of the bar only when the head of bar buffer is at least 8-feet above the water surface elevation measured from the upstream riffle crest at approximately 200 cfs flow, but in no case shall the head of bar buffer be less than one-third of the bar length.
  10. Maintain side bar margins strong enough to withstand the typical annual in-channel flows. Minimum side bar buffers are established at 15% of the maximum width of the active channel (widest point of the bar and low flow channel) but in no case should be less than 50 feet wide. The side bar buffer elevations should be no higher than 8 feet above the low water surface if mining in the upper half of the bar (upstream of the apex). If side bar buffer heights exceed the head of bar buffer height, they shall be graded to match the maximum head of bar buffer elevation, retaining a minimum 50-foot undisturbed buffer along the edge of bar.
  11. Utilize an adaptive management strategy in consultation with the County’s Scientific Review Consultant team and resource agencies. Conduct annual review and approval of instream mining plans prior to mining activities in order to assure that mining activities meet all applicable requirements and appropriate adjustments are made to address any changes in channel geomorphology.

The accomplishment of the above objectives will consider protection of habitat for fisheries and wildlife, adjacent uses, and the groundwater characteristics of the adjacent terraces.

Location & Approval

Instream aggregate extraction may be permitted in the four resource and agricultural General Plan land use categories: RRD, DA, LIA, and LEA. All instream operations require approval of a use permit and reclamation plan and environmental review to determine whether or not they are within the scope of the Program EIR.

Multi-year instream operations are allowed only in designated portions of the Alexander Valley Reach of the Russian River, Big Sulphur Creek, Austin Creek, Sonoma Creek, and the Gualala River. The designated areas are shown on Figures 7-1 through 7-8. Designations are based upon natural characteristics, previous mining activities, ownership, access, and adjacent land use.

New permits in designated instream areas will have a stated time limit of up to ten years and require approval of MR overlay zoning. The permit term for an instream mining operation may be set longer than five years only where there have been no significant violations of operating standards by the applicant on the site or adjacent sites within the past five years.

A mining permit for instream operations in a designated area may be granted for a period of up to fifteen (15) years if :

  1. The permit is conditioned to incorporate and implement an Adaptive Management Strategy coupled with a robust annual monitoring program, and
  2. the mining and reclamation plan will result in habitat enhancement work or other public benefits above and beyond the operators reclamation or mitigation obligations. 

Approval of permits for instream aggregate extraction in non-designated stream sectors requires that, based on available information, a finding is made that a significant potential benefit to flood control, bank protection, public water supply, fisheries, recreation, or riparian and aquatic habitat will result from the proposed extraction. Permits in undesignated areas may not allow extraction more than once in three calendar years in any location, and a new permit is required each time mining is to take place. Instream operations are allowed on Williamson Act contracted lands if mining and processing take place only on lands not suitable for agriculture.

While recognizing that vested rights do exist and may be exercised, the Management Plan does not allow any new permits for gravel removal within the channel of Dry Creek or the Middle Reach of the Russian River due to past channel degradation. Monitoring of channel conditions in the Middle Reach will continue in order to provide the data necessary to future management decisions. The streamway concept described in Chapter 6 and Appendix H may be implemented in the Middle Reach through County approval of an aggregate mining permit and reclamation plan with appropriate mitigation of the impacts stated in Chapter 6 and other potential impacts identified during environmental review of a streamway project. Gravel may also continue to be removed periodically from the channel overlying the water supply intakes of the Sonoma County Water Agency and other municipal water purveyors to maintain the design withdrawal rate.

Operating Standards

The following operating standards regulate the location, depth, frequency, timing and manner of instream mining to achieve the instream management program objectives set forth in Section 7.5:

Instream aggregate extraction will occur through the process of gravel bar skimming and shall be limited to the downstream portion of each gravel bar as shown in Figure 7-10. The upstream bar area, where mining is not permitted, is defined as the portion of the bar from the upstream end to the point where the bar is widest, measured from the low flow channel.

Mining will not be allowed in the water, below the water level, or below a 2 percent minimum cross-section slope from the higher of the water level at the edge of the flowing stream as shown in Figure 7-9 or a baseline reference elevation established prior to the first year of mining. Where two or more distinct channels exists on a site, the maximum 2 percent grade shall be measured from the water level of each channel. Where a minimum low water flow is not maintained in a stream and the stream goes dry in some years, the minimum levels and grades shall be measured either from the water level on July 1 or from one foot above the thalweg. If the operators elect to measure from the water level on July 1, they will be responsible for a survey tying cross-sections to clearly marked benchmarks or survey controls and recording the water level and flow rate.

All mining and grading shall minimize the potential for entrapment of fish when water levels change, and the disturbed portions of gravel bars shall be graded at the end of the mining season so that there are no areas where water can pool. Cuts in gravel bars at property lines or the edge of the mining activities shall be no steeper than 2 horizontal to 1 vertical in slope.

After extraction has taken place on a permitted site for the first time pursuant to a multi-year permit, extraction in subsequent years shall be limited to prevent lowering of the channel profile. Based on data from the required cross-sectional surveys, the Permit and Resource Management Department will determine if any aggradation or degradation has taken place since the initial mining. Where aggradation is clearly shown by the cross-sectional profile of the channel to have occurred, additional mining will be allowed to remove only the amount of gravel deposited following the previous mining. Where significant degradation has occurred, gravel removal will not be permitted.

Instream gravel mining is limited to the period from June 1 to November 1, unless an earlier start date is acceptable to the CDF&G as specified in the permit. No instream mining operations will be allowed on Saturday, Sunday, or federal holidays, but processing may be allowed on Saturdays outside the ordinary high water mark.

Where canoes or other boats commonly traverse the stream, channel crossings require the use of raised structures so that the bridge span is a minimum of 4 feet above the water line and at least 8 feet wide. All crossings shall be located so they can be readily navigated and to have clear upstream approaches and downstream exits to provide safe boating conditions. Crossings shall be adequately signed upstream to inform boaters and to identify portage options if necessary. Crossings shall be placed to minimize turbidity and flow impairment and reduce pooling and the blockage of fish. Where crossings are required to pass shad, the span shall be at least 20 feet long.

Stockpiles on gravel bars shall not be visible from designated scenic highways. Stockpile areas shall be specified in the Use Permit and shall minimize disruption of riparian cover. Stockpiles and all mining related equipment shall be removed from within the ordinary high water channel by November 1 of each year. New aggregate processing operations, including new stockpiles, shall require a minimum 200-foot horizontal setback from low water and 15 feet from ordinary high water. Stockpiles, processing operations, and ancillary uses located within the 100 year floodplain between November 1 and June 1 shall be designed and operated to prevent on-site and off-site damage from floods.

Following consultation with CDF&G, retention of existing riparian vegetation along the low flow channel and other significant stands of riparian vegetation shall be required by the County except where necessary to accommodate an access road. All instream mining operations require approval of a streambed alteration agreement with CDF&G and a Section 404 permit from the Corps. All crossings require approval of a County permit according to the requirements of Ordinance 3836R and a Streambed Alteration Agreement from CDF&G. Approval by the SLC must be obtained for mining on sovereign lands owned by the State.

Gravel removal shall not take place within an outer bank setback defined as the greater of either 30 feet or 2.5 times the height of the outer bank.

The edge of the setback shall be measured from the toe of the bank or inner edge of the riparian vegetation toward the low flow channel of the river. This setback may be reduced where the gravel removal is associated with habitat enhancement, bank restoration or protection of public infrastructure approved in conjunction with the reclamation plan. Gravel removal shall not take place within 15 feet from the outer bank along streams other than the Russian River

Other Streams: The annual amount to be removed from the designated portions of other streams will also be based on natural replenishment. The County in consultation with the a Scientific Review Consultant Team, and other qualified professionals shall establish the minimum absolute elevations for extraction at the time of permit approval. All permits in the other designated areas issued after that date will state minimum baseline elevations to be maintained by extraction.

Exceptions: Exceptions from ARM Plan standards may be proposed and considered on site-specific mining and reclamation plan proposals at the time of permit approval only where such application requests are supplemented with the following site-specific studies, prepared by a qualified expert, which address the site-specific setting and indicate why such alternate standards or methods would be the best management approach for a particular site and better serve instream objectives while avoiding and minimizing environmental impacts. The studies shall, at a minimum, include the following information:

  1. Assessment of the hydrologic and biotic setting of the proposed project site and river channel within one-quarter mile upstream and downstream of the site ("assessed areas") as to the present conditions relative to low- flow channel form and stability, flood flow capacity, channel degradation or aggradation, lateral bank erosion, and aquatic and riparian habitat.
  2. Identification of all land uses along the river banks within the assessed areas, including wells, bridges, roads, levees, buildings and other public and private facilities and infrastructure, mining operations, and any erosion sites. Identify areas needing protection, potential areas for restoring eroded banks, enhancing existing bank stability, or minimizing future bank erosion.
  3. Riparian habitat characteristics and quality, including vegetation types, sizes, and locations and potential restoration and enhancement sites within the assessed areas.
  4. Fishery habitat characteristics and quality, including pool and riffle assessments and potential restoration and enhancement sites within the assessed areas.
  5. Recommendations for setbacks, buffers, or other management practices needed to maintain stability of the low-flow channel, maintain or increase the existing flood-flow capacity, and minimize lateral bank erosion within the assessed areas.
  6. Comparative analysis of the level of environmental mitigation and benefit which would be achieved by the alternate standards and methodologies.
  7. An analysis of cumulative impacts, if any, arising from the alternate methodologies and standards, to the extent data is available.
  8. A reclamation plan incorporating an enhancement program that includes measures to enhance or restore riparian habitat, stabilize banks, minimize bank erosion, improve aquatic habitat and/or carry out actions needed to protect public infrastructure.

Exceptions to the mining standards specified in this Plan may be approved in conjunction with a mining use permit and reclamation plan only where, the County, after a duly noticed public hearing and consideration of the site-specific studies and environmental review and consultation with resource agencies and scientific review consultants determines that the revised mining methods and standards are the best management approach for the site, will better serve instream objectives and that, taken together with the other mitigations and monitoring imposed as site-specific conditions of approval will better avoid and minimize environmental impacts. In addition, permit approvals authorizing exceptions to the mining standards may only be approved if site-specific objectives and performance criteria are established, “adaptive management strategy” is employed in the compliance monitoring, and the approved plan incorporates aquatic and/or riparian habitat enhancements, bioengineered bank stabilization/repair or other substantial public benefits.

By May 1, 1998 and every five years thereafter, or more frequently if necessary, a revised estimate of the amount of gravel deposited annually in the Russian River shall be made by the County in consultation with a Scientific Review Consultant (SRC) team incorporating the results of the on-going monitoring program. If gravel removal has exceeded the estimated sediment budget to the extent that substantial channel degradation has occurred, operating standards will be changed as needed to limit extraction. If substantial aggradation has occurred, the standards may be changed to allow increased extraction. No change in standards will be proposed until all monitoring data and possible changes in management practices have been analyzed by a Scientific Review Consultant (SRC) team in consultation with resource agencies. Any changes in standards proposed following this analysis shall be referred to all agencies responsible for regulation of gravel mining or protection of resources in the Russian River channel.

To help monitor channel incision, gravel recharge and other changes in channel topography, the operator shall be required to provide annual cross-section and thalweg elevation data and analysis of any changes in channel geomorphology to the County. Annual cross-section elevation data may be prepared from aerial photography, field surveys, and Digital Terrain Models (DTM) but must include above and below water areas to the top of bank and must include thalweg and edge of water elevation data. The surveys shall be accurate to within 1.0 foot horizontally and 0.1 feet vertically of actual 3-dimensional ground coordinates.

Prior to the first year of mining under this Plan, cross-section stations shall be established at a minimum of every 400 feet throughout the permitted mining reach, as well as, one location 400 feet upstream and 400 feet downstream of the mining reach. Outside of permitted mining reach the number of cross-section stations shall average at least one per half mile or as determined necessary by PRMD to simulate the geometry of the river. Surveyed cross-sections shall also be provided at bridge crossings in or near the permitted mining area and up and downstream of the bridge. Surveyed thalweg elevations shall also be provided annually at each pool and riffle crest within the mining reach and extending one- half the project length (or to significant hydraulic controls if they exist) in both the upstream and downstream directions. The measurements outside of the permitted reach shall be used as a control, to determine the changes attributed to natural variation as opposed to project-related mining activities.

Notwithstanding the above, if no mining is conducted for more than one year in a row, the number of annual cross-section surveys required may be reduced to an average of one per half mile within the permitted mining reach provided that cross-sections at all long-term stations and at bridge crossings are still prepared and submitted for both the permitted and unpermitted areas.

At the time of permit approval, establish minimum baseline elevations for the Lower Alexander Valley mining reach at 1-foot above the higher of either the 1997 or 2007 water surface elevations adjacent to each bar. If the water surface elevation is higher than the baseline elevation during implementation of mining activities, mining shall be limited to 1foot above the water surface elevation at that time. This elevation shall become a performance standard to be maintained during the permit period. The low flow channel elevation shall be monitored each year and compared to the baseline reference elevation to indicate possible areas of channel lowering.

Each spring, aerial photography will be developed by the County for the Russian River from the Wohler Bridge area to Mendocino County.

Where multi-year instream permits are approved or renewed along the Alexander Valley Reach, and annual monitoring of the low flow channel elevations provides evidence that the groundwater table may be lowering within the mining areas, operators shall be required to monitor groundwater levels in existing or new wells outside the ordinary high water mark at a minimum spacing of one every half mile of river. The wells can be located on either side of the river within 500 feet of skimming sites, and the water level shall be monitored at a minimum of once a year in the fall when groundwater elevations are most stable.

Each spring,,aerial photography will be developed by the County for the Russian River from the Wohler Bridge area to Mendocino County. Monitoring of selected riparian and aquatic habitat along the river will be conducted annually by the County.

Where instream permits are conditioned to employ an “Adaptive Management Strategy” they shall also be conditioned to establish objectives and performance criteria. A multi-disciplinary Scientific Review Consultant (SRC) team consisting of a geofluvial morphologist, a licensed engineer with experience in river hydraulics, and river ecologist with experience in aquatic and riparian biology shall be retained by the County to review, analyze and report on annual mining plans and monitoring data to evaluate the effectiveness of mining methods, standards and mitigations and report on the status and trends of the river within each mining reach. Under the “Adaptive Management Strategy”, annual mining plans shall be reviewed for acceptability by the SRC and resource agencies and shall not be commenced until PRMD authorizes mining to proceed. PRMD shall authorize annual mining plans to be carried out only after determining that 1) sufficient aggregate recharge exists; 2) appropriate recommendations of the SRC and resource agencies have been incorporated into the annual mining and reclamation plan; 3) the annual mining plan is designed to meet performance standards and instream objectives while avoiding and minimizing adverse impacts, and 4) other required agency permits and clearances have been obtained. The amount of materials which can be removed from any permitted instream mining site may be limited by the County on the basis of monitoring data to achieve the objectives of this Plan.

A Russian River Gravel Mitigation Fund will be established with mitigation measure fees from instream and terrace operations along the Russian River. The mitigation measure fees will be used for mitigation of cumulative impacts of gravel mining on fisheries, riparian habitat, water supply systems, recreational opportunities, flood control, channel degradation, and bank erosion. The mitigation programs are discussed further in Section 7.7.


Instream mining operations shall be required to carry out annual reclamation activities at the end of each mining season and final reclamation activities at the conclusion of the mining permit time period. Each instream reclamation plan shall identify the annual and final reclamation tasks to be carried out. These may include, but are not limited to, removal of all equipment, crossing structures, and stockpiled material, grading smooth the skimmed area and surrounding cut slopes to assure proper drainage and avoid ponding on the bar surface, carrying out revegetation activities or large woody debris placement along the bar buffers or banks, carrying out habitat enhancement or bank repair and restoration work, invasive vegetation removal, and securing access points onto the bar. Reclamation plans for instream operations shall describe where and how plantings using shrubs and trees native to the area will supplement the natural revegetation process along banks, on haul roads, and in processing areas.

If an instream mining permit is:

  1. granted for a period in excess of permit in excess of 10 years, or
  2. departs from ARM standards, and/or
  3. is deemed to result in significant unavoidable impacts,

reclamation plan approvals will require additional enhancement and/or public benefit improvements to be carried out beyond that required to reclaim the site or fulfill mitigation requirements. Such improvements may include, but is not limited to, riparian habitat restoration and enhancement, aquatic habitat restoration and enhancement, removal of invasive species, bioengineered bank stabilization/erosion repair, or protection of public infrastructure.

Other Standards

Notwithstanding the above, the preceding instream operating, reclamation and monitoring requirements may be supplemented, modified or waived at the time of permit approval by the decision making body, only where it is demonstrated on the basis of site-specific analysis that alternative standards, methods and management practices, are the best management approach for the site and would provide greater avoidance and mitigation of adverse environmental impacts and fulfillment of ARM Plan objectives. In such cases, the alternative standards, methods and management practices shall be incorporated into the approved project design and/or site-specific mitigation requirements and Conditions of Approval. (Revised Sept. 28, 2004 Resolution #04-0917) (Revised September 16, 2008 Resolution #08-0777) (Revised December 7, 2010 Resolution #10-0843)