Terrace Management

The major objective of the terrace management program is to allow sufficient terrace mining acreage to supply only PCC and other high quality uses for a ten-year period while quarry resources are explored, permitted and developed. This limitation is intended to reduce the loss of agricultural land consumed by terrace mining and to minimize the potential for other environmental impacts and land use conflicts.

Terrace mining will only be allowed within the designated portion of the Middle Reach area, as shown on Figure 7-11, located south of the Town of Windsor wells east of the Russian River and generally north of the well locations west of the river. New mining requires the approval of MR overlay zoning, a use permit, and a reclamation plan. All mining permits and reclamation plans require environmental review to determine whether or not they are within the scope of the Program EIR. Procedures shall be developed and implemented to give the Board of Supervisors original jurisdiction over review of a master reclamation plan when it is submitted independently of a use permit application. Terrace mining permits may be approved for lands under Williamson Act contract only if the site will be reclaimed to plant crops within three years after the beginning of mining operations, or the Williamson Act contract is cancelled, or the contract is rescinded and replaced with an open space easement.

All terrace mining approved pursuant to this Plan shall cease after a ten-year period, which shall commence and run as follows:

With respect to terrace mining on the east side of the Russian River, the ten years shall commence on the effective date of the first use permit issued for terrace mining on that side of the river following adoption of this Plan. Similarly, the ten-year period for terrace mining on the west side of the Russian River shall commence on the effective date of the first use permit issued for terrace mining on that side of the river following adoption of this Plan.

However, if the first such permit is subject to a legal challenge, the ten-year period governing terrace mining on that particular side of the river shall be tolled during any time in which terrace mining under such permit is enjoined as a result of such legal challenge. For purposes of this section 7.6.1, a "legal challenge" shall include an action filed in a court of law or an administrative agency to contest the validity of the permit, but shall exclude any action filed in a court of law or administrative agency by a public agency to enforce permit conditions or otherwise abate violations of the permit or applicable law.

Should a court of law invalidate such first permit, the ten-year period for all terrace mining shall commence on the effective date of the next use permit issued for terrace mining on that particular side of the river, which is not subject to or withstands legal challenge, minus any time during which terrace mining was allowed or took place pursuant to the prior permit or permits issued following adoption of this Plan.

Terrace mining under a subsequent permit may only be allowed from the effective date of such subsequent permit through the remaining term of the ten- year period. However, if a legal challenge is brought against any such subsequent permit, and a court of law or administrative agency consequently enjoins terrace mining under such permit, the time remaining in the ten-year period shall be tolled during the time of such court-ordered cessation of terrace mining but only with respect to such permit and the terrace mining authorized thereunder. In no event shall terrace mining continue under the same permit on any site for more than ten years.

Because it is impossible to anticipate all applications of this provision, the Board of Supervisors reserves jurisdiction to hear and decide all disputes regarding the interpretation of this section 7.6.1 as to the calculation of the ten-year period allowed for terrace mining or the term of a particular use permit. The Board shall also have the authority to adopt such rules as it deems necessary to implement this section.

In order to reduce the amount of land consumed by terrace mining and assure that terrace resources are used to the maximum extent possible for high-quality construction aggregate, the area excavated shall be limited to ten acres on each side of the Russian River during each year after the first terrace mining permit is approved on that side of the river, as delineated above. The total area excavated pursuant to mining permits approved after adoption of this ARM Plan shall not exceed 100 acres on each side of the Russian River and shall not exceed 200 acres in total. Acreage not mined during any year may be carried over and mined in a subsequent year but not beyond the end of the ten-year period.

These acreage limits apply to all terrace mining allowed by mining permits granted after the approval of the ARM Plan but do not apply to terrace operations allowed by vested rights or mining permits approved by Sonoma County before the adoption of this Plan.

For the purposes of applying the acreage limits stated above, the area(s) excavated in any year on any site shall be measured at the elevation of the top of groundwater on May 1 of that year and shall consist of the area(s) where the mining has removed all earth materials above that elevation. Required above- water slopes, other mined areas above that elevation, and required marsh and shoal areas at or below that elevation shall not be included in the determination of excavated acreage. The total acreage excavated in a year or ten-year period and the method for calculating such totals do not modify in any way the groundwater protection standards and wildlife habitat standards stated in this chapter.

Notwithstanding the general 10-year time limit requirements listed in this Sections 7.6 and 7.6.1 to complete all terrace mining, up to 3 years of additional time from date of project approval may be allowed to complete the existing unfinished Phase VI Terrace Mining Project, subject to obtaining the necessary use permit and reclamation plan approvals. This deadline may be tolled in accordance with Section 26-92-270 of the Sonoma County Code. (Revised Oct. 7, 2008, Resolution #08-0849)

Groundwater Protection: Groundwater levels that drop may affect pumping costs and water yield and may cause some shallow wells to dry out. The following standards are designed to mitigate the potential long-term adverse groundwater effects of terrace operations. The development and reclamation of terrace pits which involve gravel removal below the top of the groundwater at any time shall conform to the following standards:

1. The maximum area of a new pit is limited to 20 acres measured at the pre- mining surface.
2. The minimum distance between the edge of any new pit and any other new or existing pit will not be less than 450 feet, as measured at the pre- mining surface. Leaving unmined gravel areas between pits will allow groundwater to flow more freely through the terrace area.
3. A 450-foot buffer will be left between new pits and the Russian River. This setback, to be measured from the edge of pit excavation on the original ground surface to the ordinary high- water mark of the river, will allow continued flow of water between the aquifer and the river.
4. No deep-pit terrace mining shall take place more than 2,000 feet from the ordinary high-water mark of the river. This limitation will reduce the potential for blocking groundwater flow into and along the edge of the Middle Reach aquifer.
5. Gravel may be extracted to the full depth of the upper gravel deposit, but the blue clay layer or underlying strata may not be mined because reduction in their thickness could result in a greater exchange of flows between the poor quality lower aquifer and the high quality upper aquifer. The transmissivity of the upper aquifer is so high that removal of the gravel deposits will have little effect on the interchange of flows between the aquifers.
6. Deep-pit terrace mining shall not take place on opposite sides of the river at any point where mining sites are directly across from each other.
7. Terrace mining operations and reclamation plans which do not meet all of the categorical standards above may not be approved unless it is determined that the proposal would not result in a drop in the water table at any point on adjacent properties of more than one foot. This determination shall be based upon an analysis of potential groundwater impacts using the MODFLOW computer model or similar model of equal or better analytical capability. The analysis shall assume the worst combination of existing and planned pit permeability, water extraction by agricultural and municipal wells, and cumulative effects since the baseline condition reported in Chapter 4, section 4. The 450-foot setback from the river specified in standard #3 above cannot be reduced regardless of the results of MODFLOW analysis.

Handling of Top Soil: Top soil that is removed from the mining area will be stockpiled and protected for future use. All soils shall be used to reclaim mined sites to crop production, enhance crop production on nearby lands, or otherwise be used in the surface treatment conducted as part of the approved reclamation plan. Each use permit application for terrace mining will include a soils report and the steps that will be used to remove, store and reuse the soils. The application will also include a full description of how the physical and nutrient properties of the soil will be maintained and protected until it is returned for productive use.

Screening and Setbacks: Visual screening of the terrace pits and mining equipment from public roads and uses will be required using shrubs and trees native to the area and berms to the extent feasible. Mining excavation and stockpiles of extracted aggregate are to be set back a minimum of 50 feet from the MR zone boundary, property boundary, and public roads. Stockpiles are also to be set back a minimum of 300 feet from the ordinary high water mark of the river. Screening, crushing, and other processing activities are to be set back a minimum of 200 feet, measured from the nearest point, from the MR boundary, the property boundary, and public roads and a minimum of 300 feet from the ordinary high water mark of the river. Mining excavation shall be set back 450 feet from the ordinary high water mark of the river.

Flood Protection and Levees: Stockpiles, processing operations, and ancillary uses located within the 100-year flood plain between November 1 and June 1 shall be designed and operated to prevent on-site and off-site damage from floods. A 450-foot setback is required between new terrace pits and the river to minimize the risk of the river channel being diverted into or through the terrace pits in major floods. In order to prevent levee failure and channel diversion, approval of a reclamation plan for any existing terrace pit which is located within 450 feet of the river requires a levee stability study performed by qualified engineers, geologists and/or hydrologists. The study shall address the following subjects:

1. Channel cross-sections and longitudinal profile.
2. Stream flow volumes, levels and meander dynamics at different flood frequencies.
3. Size, depth, slope, and mining history of adjacent pits.
4. Seasonal variations in adjacent groundwater levels.
5. Potential for seismic groundshaking and liquefaction.
6. Description of existing levee or separation materials, dimensions and vegetation.
7. Past and current erosion, bank instability and levee failure.
8. Potential for future erosion, bank instability and levee failure, including risk factors for various portions of the levee during bankfull or flood events.
9. Recommended measures to reduce risk factors to stated levels. The study shall specifically consider the feasibility and effectiveness of the following measures and others:
   1. Reducing steepness of slopes on stream side of pits.
   2. Construction of engineered levees.
   3. Paving, screening, riprap or other covering of stream banks and overflows.
   4. Planting of small and medium-size vegetation on all slopes.
   5. Other bio-technical bank stabilization techniques.
   6. Installing pipes through levees to equalize water levels without sudden overtopping.
   7. Monitoring for bank erosion and problem identification.
   8. Providing access for vehicles and equipment for maintenance and repair.
   9. Developing emergency response and repair procedures.
   10. Maintaining a source of funds for maintenance and repair.

Ancillary Uses: With a use permit, terrace operations may include processing and sales of raw, processed, or recycled earth materials and aggregate products, excluding the manufacture and batching of concrete and asphalt products.Importation of aggregate materials from approved sites under control of the same operator may be allowed with a use permit. No more than 10 percent of materials processed or exported from any terrace site in any calendar year, except materials to be recycled, shall be imported from outside the designated terrace mining area.

Monitoring and Mitigation: Aerial photographs for the purpose of monitoring terrace operations will continue to be taken by the County in the spring and the fall. The ground coverage of the photographs will include the entire area designated for terrace operations. Monitoring of the Middle Reach aquifer will be conducted by the PRMD and SCWA at the expense of the mining operators.Groundwater levels in each terrace pit and in the monitoring wells in the terrace mining area will be measured at least four times a year. The Board of Supervisors shall receive an annual report on such data and monitoring, plus at least one interim report. This information shall provide a basis for future decisions. Site inspections will be conducted a minimum of once every 60 days by the PRMD during the mining operations. Additional monitoring requirements may be imposed in order to verify satisfactory completion of approved reclamation.

All terrace operations shall be subject to mitigation measure fees for the Russian River Gravel Mitigation Fund and mitigation programs described in sections 7.5.2 and 7.7. These programs will avoid, reduce or compensate for cumulative impacts of gravel mining on agriculture, fisheries, riparian habitat, water supply systems, recreational opportunities, flood control, channel degradation, and bank erosion. In agricultural areas adjacent to past and future terrace mining sites, the mitigation fees may be used to purchase open space easements.

Priorities: In the event that restoration to the pre-mining use is not feasible, reclamation to provide wildlife habitat is the highest priority. Future use of water from the pits to support neighboring agricultural uses is a desired component for all terrace reclamation plans. The potential for development of public recreational use shall be considered and incorporated in the reclamation plans for the Kaiser South pit area.

Reclamation of existing pits as soon as possible is a high priority. In order for new mining permits to be approved, the operators must demonstrate timely performance of the approved reclamation activities for existing pits. To achieve that objective, the following terrace reclamation policies shall be in effect:

1. On the west side of the Russian River, no new permits shall be approved until the Planning Department has determined in writing that reclamation of the Basalt, Grace Ranch and Phase 2 Pits has been performed in accordance with approved reclamation plans and schedules.
2. On the east side of the Russian River, a maximum of 10 acres may be approved by the County if the applicable operator has submitted revised reclamation plans for the Wilson, Benoist, McLaughlin, and Richardson/Argonaut Pits and, if approved, begun reclamation work pursuant to the approved reclamation plans. No additional mining permits shall be approved until the reclamation plans for the existing pits have been approved and the Planning Department has determined in writing that reclamation has been performed in accordance with approved reclamation plans and schedules.

Benefits: County approval of each terrace reclamation plan requires a finding that the design features of the plan will provide the maximum public benefit consistent with the applicable post-mining use. Because of the value of this area's resources to the public and the unavoidable impact on agriculture, minimal reclamation of terrace mining sites to simply prevent hazards and impacts is not sufficient. The design and implementation features of each reclamation plan must assure the highest feasible level of production, value, or effectiveness for the applicable post-mining use.

This section describes the potential public benefits and environmental impacts of each of the allowed reclamation options and provides methods and criteria for maximizing benefits and minimizing impacts. The statement of standards is not intended to be a comprehensive or exclusive list. Reclamation plans may include other design features or methods which provide more public benefit and/or impact mitigation.

Completion: Reclamation plans for new terrace mining sites shall be designed to complete reclamation activities concurrently with the mining activities to the maximum extent feasible. Grading of final slopes and placement of soil shall take place at the end of the mining season in areas where the mining is complete. Planting of vegetation and other activities in the approved reclamation plan shall be completed within one year of the cessation of mining.

The operator shall submit an annual progress report on all activities related to the implementation of the reclamation plan. The owner or operator of an unreclaimed terrace pit shall also submit yearly cross-section profiles of the pit to indicate the depth of mining, water, and fill. Where an approved reclamation plan is later found to be infeasible by the County, a revised plan must be approved before any mining resumes on the site, and the originally approved financial assurances shall be maintained until the revised reclamation plan and new financial assurances are submitted and accepted.

Depending upon the future use specified in an approved reclamation plan, the Planning Department's determinations regarding completion of the reclamation shall be dependent upon the written approval of the following agencies: 

1. California Department of Fish and Game for wildlife habitat reclamation.
2. Sonoma County Agricultural Commissioner for agricultural reclamation.
3. Sonoma County Regional Parks Department for reclamation for public recreational use.

Wildlife Habitat: With proper design, the water and land features created by terrace mining and reclamation can be made into very productive habitat for fish, birds, and other wildlife. This use has the added benefit of restoring or replacing the many acres of riparian vegetation and natural habitat in the Middle Reach area consumed in the past by mining and agricultural uses. Where reclamation to wildlife habitat is proposed, a habitat restoration plan will be required to create and maintain conditions appropriate for species that have been historically found in the Middle Reach area. The plan shall set forth the specific types of habitat, describe how revegetation will take place, and present the other methods that will be utilized to enhance terrestrial and aquatic habitat. Reestablishing natural riparian conditions is the preferred type of wildlife habitat, particularly on sites within 1,000 feet of the Russian River.

In order to promote healthy, sustainable habitat conditions, the margins and slopes of the pit should be graded and contoured pursuant to the following standards unless the habitat restoration plan presents evidence that a different configuration is needed to achieve a desired habitat condition and the change is approved by the County following consultation with CDF&G or unless it is not feasible to grade an existing pit in the required manner. Areas above groundwater should be graded to a slope of no steeper than 3 horizontal to 1 vertical except that areas along the margin of the pit equivalent to at least 10 percent of the open water area should be graded flat to allow cottonwood and willow thickets to form on the land and/or freshwater marsh to form in the water. These zones should be from 5 feet below to 5 feet above early spring water level and should occupy all corners and coves of the water surface.

An additional area offshore equivalent to at least 10 percent of the open water area should be 5 to 15 feet below early spring water level and have some surface irregularity and changes in depth. Gravel shoals should be developed in these areas to create additional fish spawning habitat. The flat marsh/wooded thicket areas along the pit margin should drop abruptly to a depth of five feet or more in order to allow fish to keep mosquitos under control. Along other portions of the pit margin not adjacent to marsh and thicket areas, the underwater surface shall drop to 5 feet or more within 15 feet of the shore. The aquatic environment shall provide proper food, cover, temperature, oxygen and other conditions for successful fishery habitat.

All plantings of shrubs and trees should consist of native stock derived from areas along the Russian River in Sonoma County, preferably from within 5 miles of the area to be reclaimed. Reclamation plans shall specify the native species to be accommodated by the restoration Plan. The revegetation program will need to reflect the fluctuation of the groundwater table in the grading of the site and the selection and location of plant materials. The revegetation performance standards shall be considered met once the established plantings have been in place at least 5 years, and are capable of self regeneration and have met the quantified measurements for a period of two years without human intervention such as watering, weeding, fertilizing, replanting, etc. (Revised August 1, 1998 Resolution #98-1083 PLP98-0008)

ll grading and site preparation shall be timed to allow revegetation to be completed during the optimal planting season. The habitat restoration plan shall contain specific measures to incorporate the available topsoil from the site into the design as needed for vegetation survival. All slopes, benches, and berms shall be graded to the final slopes set forth in the habitat restoration plan with no more than 1 foot variation in relief. Slopes below the water level will meet the minimum standards set forth in the State Reclamation Guidelines.

The habitat restoration plan will contain provisions to control erosion of slopes and sedimentation of the pit. It will address how drainage from adjacent areas will be controlled and how all slopes will be benched, terraced, or otherwise protected. There shall be no gully wash or rill erosion allowed on graded slopes. All planting areas previously packed down by mining equipment or vehicles shall be ripped and scarified prior to resoiling or replanting. 

Agricultural Uses: Reclamation of terrace mining sites to plant crops or other agricultural uses provides substantial public benefit because it avoids a significant long-term impact where proposed mining sites are currently in and designated for agricultural production. The topsoil from terrace mining sites shall therefore be used for surface treatment and reclamation to productive agricultural use of terrace mining sites. Topsoil remaining after agricultural reclamation may also be utilized to support approved reclamation to wildlife habitat or recreation. Topsoil to be used in agricultural reclamation shall be stored, protected, and treated to limit loss of nutrients and to maintain or enhance the ability to support crop production.
Where reclamation to plant crops is proposed, it shall be deemed successfully completed when the County Agricultural Commissioner determines that adequate survival and economic feasibility has been demonstrated. Achieving this standard requires that appropriate climatic conditions and an adequate water supply are available for the agricultural use and that the site drainage and the elevation of the ground surface above groundwater are both designed to prevent root damage and support the growth of a wide range of plant crops. Each reclamation plan proposing reclamation of terrace mining sites to agricultural uses shall include a business plan and analysis of economic feasibility which contains criteria for determining successful completion of the reclamation efforts. Results of previous or existing agricultural reclamation plan efforts shall be considered as part of the review of proposed reclamation plans

Shallow mining with agricultural reclamation is identified in Chapter 6 as the environmentally superior option, but it is not mandated by the 1994 ARM Plan because the amount of gravel removed would be much less than from deep pits, substantial additional land would be required to produce a given amount of gravel, this type of reclamation is not yet proven feasible in this area, not all terrace mining sites are prime agricultural land, and other post-mining uses of terrace pits also have distinct public benefits. For these reasons, shallow mining above groundwater is therefore subject to the annual and long-term acreage limitations stated earlier and will only be considered as part of a deep-pit terrace mining project on land abutting the deep pit.

Reclamation with Additional Fill: Importing of earth materials from off-site sources, including topsoil from other mining sites and the return of fine sediments from aggregate processing, may be necessary where reclamation to agriculture or other land-based use is proposed for a terrace pit which would be too deep to allow refill and reclamation by using on-site topsoil only. The combination of deep pits with imported fill permits more gravel to be removed while still allowing agricultural reclamation but also generates new concerns about fill materials from some sources affecting groundwater quality. Where a terrace mining site is reclaimed by refilling a pit with processing sediments or any fill from off-site sources, the following standards shall apply: 

1. No pollution or contamination of groundwater quality would occur, based on application of federal and State drinking water standards.
2. The fill operation would be approved by the RWQCB.
3. Environmental review would be conducted of the removal, transport, storage, and deposition of off-site earth materials used for refill.
4. No significant impact could occur to the levels of nearby groundwater and wells based upon use of the MODFLOW computer model or similar model of equal or better analytical capability.
5. Ponding of surface water would not occur after periods when the flood plain is inundated.

Aquaculture: The raising of fish and shellfish does not require the extensive land areas used by plant crops but is nonetheless considered to be an agricultural use by the General Plan. However, the feasibility of aquaculture in the terrace pits is not known at this time. Consequently, approval of this type of reclamation is permitted only where consistent with reclamation of adjacent pit areas and clearly demonstrated to be technically and economically feasible. Project design shall control surface drainage and groundwater flow into and out of the pits, including flood overflow from the river, to protect the aquaculture operation, water quality, natural existing fisheries, and adjacent properties. The reclamation plan must include a complete description of the related processing, storage, transportation, and other land-based features of the aquaculture operation and any non-aquacultural uses proposed. This type of reclamation will be deemed completed when the aquaculture operation has been fully operational for two years. Because aquaculture is unproven in this area, the reclamation plan must specify the contingencies and alternative uses that will be implemented if the aquaculture operation is found to be technically or economically infeasible within two years. Financial assurances provided by the operator must be sufficient to cover the costs of the contingency alternatives in the reclamation plan. If an aquacultural reclamation plan has been permitted for any terrace pit, its success must be demonstrated before a similar aquaculture project will be approved for any other site.

Water Supply: The abundant groundwater resource in the Middle Reach area is tapped by numerous agricultural wells and partially by the large wells of the Sonoma County Water Agency and Town of Windsor located adjacent to the Russian River. Because terrace reclamation has the potential to affect future groundwater flows and levels, reclamation plans must consider and avoid impacts on wells in the area. The conservative groundwater protection standards in section 7.6.2, including MODFLOW analysis, maximum area, and minimum separation, will prevent these impacts, but if additional mitigation is required for a specific reclamation plan, it may include an additional setback between the pit and the wells or transfer of ownership or control of the pit to the owner of the wells after mining.

Removal of large quantities of sand and gravel also increases the water storage capacity and the ease of access to the water resources if the pits are not refilled. This creates the opportunity to go beyond mitigation of potential impacts by using terrace pits to provide an additional water source or storage reservoir for nearby users and water systems. The County encourages creative use of such opportunities to enhance the water supply facilities and systems in the Middle Reach area. If supplying water to neighboring agricultural properties is proposed for a site, it may be appropriate to transfer the post-mining ownership of the site to the owners of those properties or to an irrigation district or other independent entity. Similarly, for pits located close to public water supply wells, reclamation plans should consider transferring post-mining ownership to the water purveyor. Before the approval of any terrace reclamation plan which proposes such a transfer of ownership or any off-site use of the water in the pit by parties other than the mining operator and site owner, all affected parties must agree in writing to the legal arrangements and water quality protection proposed in the reclamation plan. In any case, water supply development is considered as an added benefit or feature in conjunction with other post-mining uses allowed and is not considered to be a primary use or sufficient reclamation by itself.

Recreation Facilities and Activities: The water-based recreational opportunities associated with the lakes created by terrace mining and their proximity to the Russian River have long been recognized. The Regional Parks Department has previously expressed a need for and interest in public recreation facilities in this area. The Open Space map in the General Plan designates two general locations for future public parks in the terrace mining area, one west of Windsor River Road and the other near Wohler Bridge. The Open Space map also designates the Russian River as a Waterway Trail where recreational boating is to be facilitated and adjacent hiking trails can connect urban areas, parks, and the waterway.

The only recreational uses which could be allowed with a use permit by the present LIA General Plan designation and zoning in the terrace mining area are game preserves, horse stables, fishing and hunting clubs, and golf courses. Development of public recreational facilities by the County would therefore require changing the General Plan land use designation to Public / Quasi-Public and changing the zoning to PF Public Facilities as part of the approval process for a park master plan. minimize conflicts with the valley's prime vineyard operations. Recreational development of this area will depend upon close cooperation between the operator and the County Regional Parks Department. Transfer of ownership will require a written agreement specifying the responsibilities of each party.

County approval of a reclamation plan for the Kaiser South area shall consider the effects of the proposed mining, grading and reclamation on the potential for future public recreational development of the site. The Board of Supervisors shall direct the Sonoma County Regional Parks Department to prepare a needs assessment, site evaluation, and feasibility study for development of a regional park on the Kaiser plant site, McLaughlin Pit, Wilson Pit, Benoist Pit and adjacent properties, but this requirement is not intended to delay or prevent the approval of reclamation plans for mined lands and the completion of reclamation in accordance with approved reclamation plans. If a park appears feasible, a project design, financing plan, and environmental analysis and determination shall be prepared for Board review and approval. The net County costs of park-related activities shall be reimbursed by the Recreation Enhancement Program funded by the Russian River Gravel Mitigation Fund. The Regional Parks Department shall consult with nearby property owners and residents and other interested parties in public meetings during both the initial site evaluation and environmental analysis for the project.

Wastewater Storage: Several cities near the Russian River place treated sewage effluent in ponds for evaporation, filtering by the surrounding sand and gravel deposits, and further treatment by biological processes. The only site where this is done in the Middle Reach terrace mining area is the old Basalt pit used by the City of Healdsburg for many years. Monitoring thus far has not found any significant water quality impacts connected with this use. Any reclamation plan for this pit shall serve to protect and maintain the City of Healdsburg's ability to continue to use the pond for wastewater storage in accordance with applicable water quality standards. The processing sediments which have been piped into this pit may be removed to enlarge effluent storage capacity and provide fill for agricultural reclamation of other mined areas as long as the transfer of sediments meets the standards for imported fill stated above. No other terrace mining site may be used for storage or disposal of effluent from public sewage treatment systems unless the Board of Supervisors finds that the proposal is the environmentally superior alternative being considered, will meet applicable water quality standards enforced by the Regional Water Quality Control Board, and will avoid significant impacts on nearby groundwater and surface water.

Unfilled Pits: Unless previously specified in this Chapter, the following standards shall apply where a pit will not be refilled above groundwater level and will be left as open water:

The Management Plan identifies the Kaiser South terrace pit area, including the Wilson, McLaughlin and Benoist pits and Kaiser's processing plant site, as an appropriate location for future public recreation use. The site is well located to serve the region, connect with other publicly-owned lands, and, most importantly, 

1. The potential for levee failure and/or diversion of the river channel into the pit shall be minimized.
2. No pollution or contamination of groundwater quality shall occur based upon federal and State drinking water standards.
3. No significant impact shall occur to the levels of nearby groundwater and wells based upon use of the MODFLOW computer model or similar model of equal or better analytical capability.
4. Sedimentation from erosion of adjacent slopes shall be minimized.
5. Where human uses of a reclaimed pit are proposed, these shall be minimized in and adjacent to marsh areas and riparian habitat where wildlife is abundant.
6. Final pit slopes below the water level shall not be steeper than 1 horizontal to 1 vertical.