3.2 hydrology and water quality - mendocino county, ca4. project area surface water hydrology...

Harris Quarry Expansion Draft EIR 10 County of Mendocino

3.2 Hydrology and Water Quality

A. Setting 1. Introduction This section of the DEIR describes the existing hydrologic conditions of the Harris Quarry area and discusses the potentially adverse physical and chemical hydrologic impacts from the project. The expansion plans would potentially result in:

• Physical hydrologic affects from changing the contributing drainage area of the quarry.

• Water quality effects from chemical hydrologic interaction and transport of runoff draining from the expanded mining area, the new processing area, and the new road configuration into nearby drainages.

• Groundwater lowering effects from pumping and seepage into a deepened sedimentation basin.

• Adverse effects on wells and springs from quarrying disruption of groundwater flow pathways.

• Adverse effects on Forsythe Creek from interruption of creek flow, or diversion of quarry area contributions to base flow.

This analysis was prepared based on reviewing the following sources:

• Environmental Assessment and Reclamation Plan, Harris Quarry Expansion. Rau and Associates, 2005;

• Process Area Plan for Harris Quarry, January 2005, Northern Aggregates, Inc.;

• Final Grading and Phased Erosion Control Plans for Earth Products Removal, Rau and Associates, October 10, 2006;

• Stormwater Pollution Prevention Plan, September 2004, Northern Aggregates, Inc.;

• Well Test for Quarry/Processing Plant Environmental Review at Harris Quarry South of Willits, Rau and Associates, April 2007;

• Well and spring location map, Jason McConnell, Northern Aggregates, February 2007;

• Mendocino County Water Agency Memorandum, June 2005; and

• Site investigation, well and spring verification and mapping by Questa Engineering Corp, May 2007.

2. Project Description The Harris Quarry Project elements that have an effect on the local hydrology include a three phase expansion of the aggregate extraction area, a new aggregate processing

Harris Quarry Expansion Draft EIR Page 111 County of Mendocino

facility, a new paved haul road between the quarry and processing area, and an expanded, paved quarry access road. The processing facility would be located south of Black Bart Drive, immediately north and over the ridge from the existing quarry site. It would include an asphalt processing facility, a concrete production facility, a fueling area, truck and auto parking, and quarry stockpile areas. The work area would have an asphalt composite surface. A sediment cleanout and retention swale would be constructed to the northwest of the processing area. The water source for the processing area would be an existing well and, if needed, an existing spring, with a combined 22 gallon per minute capacity. The three-phase aggregate extraction area expansion begins with a base floor elevation at 1,850 feet, and then deepens to 1,750 feet, with a final pit elevation of 1,650 feet. The associated maximum depths of a proposed sedimentation pond would be 1,814 feet, 1,721 feet, and 1,636 feet accordingly. The sediment does not have a proposed outlet. It would release water by pit bottom infiltration and evaporation. As such, it can be considered a “wet retention pond” not a “detention pond.” As the quarry floor would be lower so would the elevation of the southerly ridgeline. Consequently, the quarry’s area of disturbance will become closer to the drainage to its south as the quarry is expanded. Average distance from the quarry boundary to a 50-foot stream buffer would be between 190 and 350 feet. Drinking water sources for the quarrying area would continue to be purchased from an external supply. The estimated volume of water draining the surrounding area and running into the first phase quarry pit from a 100-year 24-hour storm was estimated to be 25.26 acre feet (Rau Engineers, 2005). This corresponds to flooding in the pit bottom to the internal contour elevation of 1,833 feet. The volume of accumulated runoff water entering the pit during the average winter would be 148.6 acre feet, including losses from evaporation and infiltration. For the wettest year the volume of storage required would be 259.1 acre feet. The expansion of the quarry road network between the mining area and the proposed processing area is planned to facilitate entry, egress, and traffic flow. Whereas a single gravel road currently serves the entry and egress from the quarry mining area, an additional haul road would connect the processing area with the quarrying area, and the future roads would have an asphalt surface. The haul road would drain to forested hill slopes, while the newly paved access road would drain to new and existing stormwater culverts. 3. Topography and Climate Harris Quarry is located immediately west of Highway 101 approximately five miles south-southeast of the City of Willits in Mendocino County, California. The study area includes the existing quarry and the area that is part of the proposed quarry expansion. In addition, several small, adjacent watersheds that could be affected by the proposed project are included within the study area. The terrain is moderately rugged to rugged, with elevations ranging from 1,600 feet to 2,078 feet above mean sea level. Forsythe Creek and some smaller tributaries of that creek lie to the southeast of the project area. (See Figure 3.2-1).

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Figure 3.2-1

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PROJECT AREA HYDROLOGY AND GEOLOGYHarris Quarry, Mendocino County, California

Figure 3.2-2

(To Willits ~ 3.0 miles)

(To Ukiah ~ 4.1 miles)

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This map was compiled from the following sources: Alquist-Priolo Fault Evaluation Report 123, Figure 3A, California Department of Conservation, California Geological Survey, July 8, 1981; BCI, Engineering Geology and Geologic Hazards Report, Harris Quarry, Willits, California, December 9, 2004; Pampeyan, E.H., Harsh, P.W., and Coakley, J.M., 1981, Preliminary Map Showing Recently Active Breaks Along the Maacama Fault Zone Between Laytonville and Hopland, Mendocino County, California; USGS MF-1217; Northern Aggregates Processing Area Plan, 2005; Rau and Assoc., Environmental Assessment and Reclamation Plan, 2005. Map base: USGS 1:24k Digital Raster Graphic, Laughlin Range

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The climate of the region is characterized as Mediterranean. The region’s rainy season extends between the months of October and April, with generally dry conditions for the remainder of the year. The highest rainfall months are November through February. The average annual rainfall for Willits is roughly 51.29 inches; minimum and maximum recorded annual precipitation is 30.31 inches (1985) and 91.6 inches (1983), respectively43. Temperatures in the area are relatively moderate, averaging 54 degrees Fahrenheit annually. Temperatures occasionally drop below freezing at night in the winter and can rise to over 100 degrees Fahrenheit during the summer months. Evaporation data for the region indicate seasonal rates of approximately 44.6 inches per year44. 4. Project Area Surface Water Hydrology Russian River The Harris Quarry is located roughly 1,200 feet east of Forsythe Creek, a major tributary of the Russian River (see Figure 3.2-2). The Russian River drains an area of 1,485 square miles in the California Coast Range north of San Francisco (Higgins, 1952). From its headwaters north of Ukiah, the Russian River flows southeastward through a series of canyons and valleys for about 104 miles. South of Healdsburg, the River generally flows to the southwest until it joins the Pacific Ocean near the town of Jenner. The Russian River system is the primary drinking water source for more than 570,000 people in Mendocino, Sonoma, and Marin Counties (Sonoma County Water Agency, 2003). Forsythe Creek Forsythe Creek enters the Russian River north of the community of Calpella approximately sixteen miles downstream of Harris Quarry. Forsythe Creek is a fifth order stream with a drainage area of 36,480 acres (57 square miles) and an average precipitation of 45.7 inches per year.45 Its major tributaries include Mill Creek, Walker Creek, and Seward Creek. Elevations range from about 680 feet at the confluence with the Russian River to 2,600 feet in the headwaters. Historically, the creek has year-round flow, and may go dry during very dry years46. The watershed has a history of grazing and logging dating from the 1850’s47. It is likely that many of the stream processes and stream conditions are a result of these land uses. Significant stream restoration projects are planned or have been implemented to address chronic bank erosion, reduce sediment sources, and improve salmonid habitat. Salmonid migratory habitat on

43 “Willits, California – Climate Summary”, Western Regional Climatic Center, Willits (049684), California

Monthly Total Precipitation (http://www.wrcc.dri.edu/cgi-bin/cliMAIN.pl?ca9684) Accessed April 9, 2007.

44 West Yost, Assoc, 2006. City of Willits Water Supply Planning Study. 45 The stream order signifies the relative position of a stream segment in a drainage network: the

smallest, unbranched, intermittent tributaries are designated order 1; the junction of two first-order streams produces a stream segment of order 2; the junction of two second-order streams produces a stream segment of order 3, etc. Ephemeral draw channels that exist upstream from the intermittent first order streams in the drainage basin will be designated 0.

46 Resources Agency of California, Department of Fish and Game. 1963. Stream Survey. 47 The Cultural Landscape Foundation, 2006.


Forsythe Creek extends from the confluence with the Russian River to a natural waterfall migration barrier located approximately 59,598 feet (11.3 miles) upstream48. This location is estimated to be upstream of where the north-south tributary adjacent to the site (see the discussion below) enters Forsythe Creek and below where any hill slope drainage from the processing area could enter the creek. Minor North-South Drainage A well-defined seasonal drainage channel parallels the west side of State Highway 101 (see Figure 3.2-2). It receives runoff from approximately 0.2 square miles, mostly in the form of overland flow and road drainage. Its upstream source of runoff is the area around and including Black Bart Drive. At the end of Black Bart Drive it drains to a culvert which then transfers runoff from the west side of Highway 101 to the east side of the Highway. A second culvert carries flow and additional runoff back to the west side of the highway to a channel that parallels the quarry entry road. These two culverts effectively transfer runoff from the west side of the highway, to the east side, then back again49. Before entering the quarry area, the flow enters a 30 inch stormdrain, then daylights in the area next to the scale house, then returns to a culvert before discharging to the south-facing slope below the quarry. During a May 2007 field review by Questa Engineering staff, it was noted that upstream of the quarry, the drainage has a channel width ranging from approximately three to 6 feet, and a depth from one to four feet. Flows were estimated to be around 0.5 cubic feet per second (cfs). There was no evidence of siltation, and the bed consisted primarily of cobbles, gravel, and coarse sands. Downstream of the quarry, the bed consists of larger cobbles, and there was an approximate 4 to 6 feet of vertical channel incision as flows have cut through the colluvial fill from the adjacent slopes and the confluence with the west to east running drainage. This indicates some minor quarry induced channel incision of the adjacent drainage. Southerly East-West Drainage Another small drainage, which is a tributary of Forsythe Creek, is located immediately to the south of the quarry mining area. The channel runs from west to east and has a drainage area of about 49 acres (0.9 miles). It was dry during the May 2007 investigation by Questa Engineering staff. Large boulders, wood debris, and smaller side cast fill the channel at its midpoint, probably as a result of previous quarrying practices and the natural active erosion processes. At its easterly terminus, there is a 3-foot headcut caused by the drainage flowing from the north-south drainage. A trickle of groundwater was observed flowing out of the base of the headcut. Again, this indicates that the existing historic disturbances in the vicinity of the quarry have had some small impact on the channel processes. South of the project area, the creek continues for about 4,600 feet through less sloped terrain to where it joins Forsythe Creek.

48 Resources Agency of California, Department of Fish and Game. 1999. Stream Survey. 49 Jason McConnell, Northern Aggregates. 2007.


5. Project Site Drainage The surface water contributions at Harris Quarry are in the form of overland flow from the mining and processing areas, roads, surrounding hill slopes, and the drainage channel running from the north to the south along the projects eastern edge. Stormwater runoff from the existing Harris Quarry facilities currently collects in a sediment retention basin on the southeast corner of the quarry floor, and more widely across the quarry floor during wetter times of the year. Other runoff collects on quarry access road on the east of the quarry and the north-south creek drainage. Drainage in the Active Mining Area The mining area is composed of gravel access roads, steep actively mined surfaces, and relatively flat benches where source material is accessed, stored, and transferred. Exposed bedrock and piles of overburden and crushed rock are the typical surface materials. Sparse trees, shrubs, and grasses cover the western upper slopes adjacent to the active mining area, while a woodland persists to the north. Most of the drainage of the active mining area occurs as overland flow directed to the quarry floor. A sediment basin or pond was observed in the south of the quarry in May 2007, but was not hydrologically connected to the surrounding drainage area at the time. The purpose of the basin is storage of sediment from quarry runoff, evaporation, and infiltration. As previously noted, there is currently no active stormwater runoff discharge from the majority of the disturbed quarry areas to the adjacent creeks. A portion of the runoff from the quarry access roads is contributed to the minor north-south drainage. Project Site Flooding The project site is not located within a 100-year or 500-year flood hazard zone, as mapped by the Federal Emergency Management Agency (FEMA) (FEMA, Flood Insurance Rate Map, Mendocino County, California (Unincorporated Areas), Panel 060183 0700 B, 1983). 6. Groundwater Resources Regional Groundwater Two major alluvial groundwater basins are located outside of the immediate project area, the Willits basin, 1.5 miles to the north, in the Eel River watershed, and the Ukiah basin, 10 miles downstream to the southwest in the Russian River watershed. Outside of these large basins and several smaller alluvial valley basins, groundwater in the region is generally scarce and limited by the condition of “bedrock aquifers,” where groundwater is variable depending on local rock fracturing. Wells in fractured rock usually have a low capacity (less than 5 gallons per minute). A description of the hydro-geology of the Harris Quarry area is presented in the groundwater section of the Geology Section (See Section 3.1), and the reader is referred to that section for additional information on groundwater occurrence and movement in areas of Franciscan complex bedrock.


Immediately Neighboring Springs and Wells Three wells have been drilled into the underlying Franciscan bedrock in the immediate quarry area with the objective of encountering and capturing groundwater moving through and stored within open fracture zones. The project is planning on using the well to the immediate north of the quarrying area and, if needed,the springs previously used by CAL FIRE further to the northwest to supply water for the quarry and the processing area. The spring is located 2,300 feet northwest of the processing area, on the northeast facing slope of the Black Bart Drive ridge. An additional shallow well is located upslope, near the primary supply well, and a 500-foot deep “dry well” that was never developed is located in the southeast part of the quarry area. The nearby businesses located north of the proposed project include a restaurant, a motel, a custom modular home retailer, and a realtor. These businesses all use diverted spring water provided by the Church of the Golden Rule, which is stored in a water tank to the west. The source of this water is a spring approximately two miles to the south-east of the quarry. An additional spring used as a supplementary water source for residences west of the project parcel is located on the applicant’s property. The spring is approximately one mile west of the processing facility site, on the southwest facing slope, and at the same approximate elevation as the proposed processing area. In a June 15, 2005 letter to the Mendocino County Planning and Building Services (MPBS), the Mendocino County Water Agency expressed concern that the quarry expansion could impact spring flow for users of the spring. The locations of wells and known springs within a 2-mile vicinity of Harris Quarry are shown on Figure 3-2-2. Private wells are not shown on this figure, because of State-required consideration of privacy issues, but information collected from a review of the distribution of wells and analysis of well logs was considered in this analysis. As noted in the groundwater discussion of the geology section of the DEIR, groundwater is largely confined to highly weathered zones and rock fractures, which often follow geologic structure, in areas of Franciscan rock. An analysis of available drillers logs for the private wells in the vicinity of the quarry indicates highly variable conditions, with wells 50 to 60 feet deep located adjacent to wells 200 to 300 feet deep, and with dry wells interspersed among them. Estimated yields to these wells is also variable, ranging from 2 to 3 gallons per minute (gpm) to as much as 12 to 15 gpm. Questa Engineering's analysis of the distribution and characteristics of these wells did not indicate any specific geographic trend. It is concluded that based on this noted variability, although the wells are drawing water from rock fractures, the fractures are likely not inter-connected. It appears that the springs to the north and to the northwest, along Black Bart Drive, that provide surface water to the quarry and that are used by some nearby residents as a supplemental water source, in addition to the active wells within the quarry area, occur in a narrow band in a northwest-southeast alignment, to the north of the quarry. This apparent trend roughly parallels Black Bart Drive on its north side and is shown on Figure 3.2-2. The trend of this band follows a general ridgeline, although springs are


located on both the northeast and southwest sides of the upper ridge. Further, the general trend of this spring and well band alignment parallels the trend of Forsythe Creek to the southwest. In addition to the springs that occur within the band of highly weathered and fractured rock to the immediate north of the quarry, several springs occur to the east, along the Maacama fault zone (see Figure 3.2-2). Often creeks will erode (over geologic time) into rocks that are weakened and fractured along structural lines. This general northwest-southeast trend is consistent with the regional geologic structure, although it is somewhat oblique to the more northerly trend of the nearby Maacama fault zone (see also geology section of DEIR for a more complete discussion of the geology of this area). Available regional geologic mapping shows the general spring-well line orientation as occurring near the contact between undifferentiated Franciscan assemblage rock and Franciscan meta-volcanic rocks, but the scale of mapping of this map sheet is too small to properly show the orientation and details of the contact.50 The Ukiah sheet does not show the quarry area, including the trend of wells and springs, as being within a fault zone, nor does it show the Maacama fault zone, but this trend could represent either an unrecognized fault that has fractured and sheared the local rocks, creating similar opportunities for springs to issue forth, or it could conceivably represent a joint or rock fracture system that is connected over some distance. Pampeyan (1981) also does not show any structural trends or lineaments along this spring-well line band in his mapping of the Maacama fault, but a lineament with a similar trend is shown on the Maacama fault studies map along (just north of) lower Forsythe Creek to the south of the quarry area, and the fault maps show a trace of the fault with a similar trend just to the north of the quarry, west of the Mendocino County CDF Headquarters.51 A spring also occurs along this lineament. A detailed geologic map of the immediate quarry area that was prepared by BCI (Figure 3 of October 2004 BCI report that is on file with the Mendocino County Department of Planning and Building Services) does show that the spring-well line band is within or near a zone of intensely weathered and fractured sandstone and meta-sedimentary rock, and geologic map symbols representing a fault or shear zone with a similar northwest-southeast orientation are also shown on this map.52 According to the BCI report, shallow borings completed in the vicinity of this area indicate that some 15 feet or more of soil, colluvium and weak rock (shale and chert) are underlain at depths to at least the 80 feet explored in the study by (harder) blue green rock, which was interpreted to be a metavolcanic rock or greenstone. The geology of the area, including contacts of rocks with differing primary and secondary porosity, fractures and shear zones are of interest as any quarry operations that disrupt a potential “open pipe” rock fracture pattern that serves to carry groundwater laterally for some distance, could conceivably also disrupt the flow of water to springs upon which local residents depend. Springs are also an important source of water to wildlife in an area where many creeks go dry in the late summer and fall. Potential quarry project impacts on springs are especially of concern in

50 California Division of Mines and Geology, 1960, Geologic Map of California, Ukiah Sheet. 51 Pampeyan, E.H., Harsh, P.W., and Coakley, J.M., 1981, Preliminary Map Showing Recently Active

Breaks Along the Maacama Fault Zone Between Laytonville and Hopland, Mendocino County, California; USGS MF-1217.

52 Blackburn Consulting, Inc. (BCI), 2004. Engineering Geology and Geohazards Report for Harris Quarry, Mendocino County, California


the Ridgewood Subdivision rural residential area, where some residents of this water-short area depend on the spring on the Harris Quarry property (but outside of the proposed active quarry area) as a supplemental water source in an informal arrangement with the quarry property owner. Alternatively, the springs could occur coincidentally within a zone of weathered and fractured near surface rock and emerge at similar contacts with the underlying more dense, less weathered and fractured greenstone rock. If this is the case, then quarrying operations are much less likely to disrupt lateral groundwater movement and impact springs. In March 2007, Rau and Associates Inc. conducted a 72-hour pump test of the currently used quarry well, with water level and flow monitoring of adjacent wells and springs with the objective of providing information useful to determining if increased use of the on-site well by the quarry could impact nearby wells and springs through adverse well drawdown or “cone of depression” type impacts.53 A secondary objective was to provide additional information to characterize the general fractured bedrock “aquifer” in this area. Well #1, the quarry well on the map, is the well that is proposed to serve the expanded quarrying operations. Wells #2 and #3 (not shown) were located near-by and were used for monitoring groundwater levels during the pumping of the quarry well. Well #1 with a well depth of 35.0 feet was pumped for 72 hours and had a sustained yield of about 15 gallons per minute. Observation Wells #2 and #3 (the monitoring wells) showed no response to the pumping of Well #1. Chart 3.2-1 In Appendix C of this EIR provides the pump test data, and Charts 3.3-2, 3, and 4 in Appendix C display the results of the pump tests on the monitoring wells and springs, including recovery. Spring discharge was also monitored at the spring adjacent to Black Bart Drive and at the spring that was previously the source of water for CDF during the test pumping, with no significant decrease in spring discharge observed during the well test pumping. Spring discharge decreased about 10%, from 3.16 to about 2.80 gallons per minute, during the pumping period, and continued to drop after test well pumping ceased by about another 10% during an additional 5-day post pump test monitoring period. The spring monitored was one of a pair of springs closest to the quarry, and not the more distant spring that provides a supplemental source of water to the Black Bart residential area. However, any inference of well pumping impacts noted on the closer spring's flow will provide a conservative indication of potential affects on the more distant spring. Since this (winter 2006-spring 2007) was a very dry period, with little rainfall occurring within 4 days of the pump test, it cannot be conclusively concluded if the slight decrease in spring discharge during and following test well pumping was due to well pumping, or reflects normal spring flow seasonal discharge drop off following the end of the unusually dry rainy season. Because the monitoring wells showed little or no response to the pumping of the test well, completing traditional pump test well hydraulics to determine the ability to store and transmit the groundwater of the fractured bedrock aquifer was not possible. The April 4, 2007 Rau and Associates Inc. report stated that the test well actually had its static water level rise slightly during the test period. There was virtually no recovery in either the quarry pump test well, or the monitoring wells. Rau and Associates surmised

53 Rau & Associates, Inc. letter report dated April 4, 2007. This report is included in Appendix C of this EIR.

Harris Quarry Expansion Draft EIR 8 County of Mendocino

that the reason the observation wells did not recover following cessation of pumping and continued to have their static water surface levels drop was a result of normal seasonal drops in water surface levels, perhaps accelerated by the dry winter/spring. They also indicated that the fact that the pumped test well had water surface levels increase was a result of the normal seasonal downward movement of groundwater in rock fractures, as the test or pumped well was the deepest and lowest in elevation. They explained the fact that a 500-foot deep well located within the proposed quarry expansion area to the south was a dry well was due to some sort of impermeable “bedrock dam”. In general, the pump test charts show a fairly rapid drawdown in the pumping well, with stabilization at a discharge of about 15 gpm. The monitoring wells show little impact of pumping (poor hydraulic connectivity of rock fractures) and the test well had poor recovery following cessation of pumping. An alternate explanation, consistent with the observed spring-well band, of the little or no response of the monitoring wells with the pumped test well, and conjectured geologic structure or highly weathered rock and fracture zone, is that the test well and the nearby observation wells are not very well hydrologically interconnected through a shared and intercepted common rock fracture system within the spring-well band zone. Only a finite amount of groundwater is stored within these rock fractures and recharge and recovery from above percolating groundwater would be slow, especially in a dry year. Since the test or pumped well is deeper and has a well bottom lower in elevation than the observation wells, it could have effectively drained during pumping the adjacent observation wells and their small surrounding volume of water held in rock fractures, with slow or no recovery during this dry water year. This did not occur. The fact that the 500-foot well is a dry well can be explained by its being located outside of the conjectured highly weathered rock or fracture/shear zone band and has few rock fractures containing water. West of Quarry There are approximately 30-35 rural residential units within a two-mile radius of the quarry in the Ridgewood Subdivision to the west of the Harris Quarry, most of which depend on individual wells and several springs for their water supply. This is a water short area. Nearly all of these residencies have wells drilled in hard rock and depend on water stored in rock fractures and replenished annually by rainfall-fed groundwater recharge for their water supply. Most of the residents have water storage tanks, and many need to truck in water late in the summer and fall in drier than normal years to fill their storage tanks. North of Quarry A small commercial area occurs less than a quarter mile north of the quarry. The commercial area consists of a restaurant, a 30 unit motel, a residence, and several other small businesses, including a mobile home sales lot. This area reportedly relies almost entirely on water supplied by a spring on land owned by Church of the Golden Rule


located south of the quarry and east of Highway 101. The water supply line runs along the easterly quarry perimeter. Further to the north and on the east side of Highway 101 is the California Department of Forestry and Fire Protection (now called CAL FIRE) headquarters. This is about one half mile from the quarry. This facility previously depended on springs owned by the project applicant for its water supply, but now obtains water from the City of Willits. South of Quarry Ridgewood Ranch, owned by the Church of the Golden Rule, is located immediately south of the quarry. The Church gets much of its water supply from springs in the hills east of Highway 101. The springs have been deemed "pristine water sources" by the State, which allows the Church to blend the various sources. These springs feed covered reservoirs, which deliver the water to the uses west of the highway. There are about 8 springs feeding two reservoirs.54 There is also a moderately productive alluvial well to the east of Forsythe Creek on the ranch. East of Quarry There is undeveloped land to the east of the quarry. This area is east of the Maacama fault and appears to be hydrologically not connected to the quarry area. 7. Water Supply and Usage Water for the project area is currently supplied by wells and springs located on the project property and water purchased from an outside supplier. Onsite water supply and storage estimates were completed by Northern Aggregates in the amounts listed below. Source Gal/Min Gal/Year* Well 15 6,762,198 Spring 7 3,155,693 Total 22 9,917,891 *Pumping 6 days a week These sources will be used to store and replenish the following storage facilities: Storage Storage Facility (Gal) Well water tank 212,000 Spring water tank 4,000 Wash plant water tank 20,000 Quarry water tank 5,000 Concrete surge tank 5,000 Concrete detention pond 27,000 Total 273,000

54 Tracy Livingston, Church of the Golden Rule ranch manager, personal communication, 7/12/07.


The proposed water use for dust suppression and aggregate washing were estimated at 4.0 million gallons per year, as shown below. Water Use Use Amount (gallons/year) Aggregate wash and dust suppression 1,200,000 Ready-mix plant 2,800,000 Total 4,000,000 8. Water Quality Stormwater Runoff Stormwater runoff pollutant sources at the quarry include loose decomposed rock (rock flour) and soil stockpiles, disturbed slopes, and vehicles and equipment storage and maintenance areas. Rock flour and soil can contribute silt and suspended solids to stormwater runoff. Vehicles and equipment can contribute diesel fuel, gasoline, motor oil, lubricants, hydraulic fluid, anti-freeze, and other similar pollutants to stormwater runoff. To prevent the transport of these pollutants to downstream waters, the quarry operator has developed a Storm Water Pollution Prevention Plan (SWPPP) and a Spill Prevention Control and Countermeasure Plan (SPCCP), in accordance with the requirements of their NPDES General Permit55 (described in the section “Regulatory Framework” of this DEIR). The Spill Prevention Plan provides general information on the type and quantity of potential on-site spill sources, design and operating procedures, emergency response procedures, and inventory, facility maintenance, training, and fuel transfer information. Existing Harris Quarry SWPPP Best Management Practices Harris Quarry has developed a Storm Water Pollution Prevention Plan (SWPPP) that discusses the sources of sediment on the site and how the quarry currently utilizes Best Management Practices (BMPs) to mitigate some of the potential impacts of on- and off-site pollutant transport. These practices are focused on retaining and/or filtering eroded sediments in runoff water, and place less emphasis on soil erosion control through establishment of adequate protective cover. The BMPs are both structural and non-structural in nature. Existing Structural BMPs The structural BMPs included in the current Harris Quarry SWPPP include site grading and berms to prevent stormwater from entering both the north-south drainage and the southerly east-west drainage. The existing sediment retention basin is designed to contain a 2-year 24-hour storm, while the larger quarry floor will contain a 100-year storm. Operations continue only when the quarry floor outside of the sedimentation pond

55 State of California General Industrial Activities Storm Water Permit (General Permit), Water Quality

Control Order N. 9703-DWQ, adopted by the State Water Resources Control Board on April 17,1997.


is not inundated. The berm to the south is 2 feet to 6 feet high and prevents quarry by products and erosion from entering the southerly east-west and north-south drainages. Berms also direct storage water to the existing sediment retention pond. Double walled fuel tanks and lines are in use, and the quarry grading serves to contain stormwater as well as any hazardous materials in the event of a spill. Existing Non-structural BMPs Non-structural BMPs include good housekeeping practices (e.g., using a vacuum truck to remove soil from the paved parking area), preventative maintenance of all structural control measures, a spill response plan, employee training in material handling and storage, as well as training in conducting stormwater visual observations, and completing data forms. Annual comprehensive site compliance evaluations are all documented. However, as previously noted, stormwater monitoring does not presently include sampling due to the distance and gradient at the location of the southerly culvert outfall and because the quarry stormwater is retained on site. Other non-structural BMPs include quarrying excavation and construction practices such as the combing ridgeline material toward the quarry basin to reduce side cast of boulders and sediment to adjacent fill slopes.56 Planned Stormwater Management and BMPs The Operator has submitted a Notice of Intent to the North Coast Regional Water Quality Control Board stating compliance with National Pollutant Discharge Elimination System (NPDES) for industrial activities. For all three phases of the proposed quarry expansion, the quarrying area stormwater would be retained onsite. The configuration of the proposed retention system would be such that even stormflow from 100-year, 24-hour events would be kept within the quarry basin and not be released to local slopes or drainages. The water balance would be maintained by adequate storage capacity during the winter months and evaporative and infiltration losses during the summer. Accumulated sediments would be removed from time to time to maintain retention storage capacity. The sedimentation/retention basin would be located to the north, at the base of the quarry face. There will be no work on the quarry floor during periods of inundation. Berms to the south and around an eastern sump would continue to protect the minor north-south drainage. Erosion control planting would be done on the southerly berm. At the processing site, constructed berms are proposed that would prevent off-slope drainage and direct stormwater over an asphalt pavement surface to a swale/cleanout structure at the northwest end of the processing facility pad. Fill slopes will be vegetated, stabilized, and culverts with rocked outlets will allow water seepage from within the fill slopes to drain. The proposed haul roadway will drain to natural slopes or to the newly culverted entry road and the smaller north-south drainage. Runoff will be added to existing runoff from

56 Jason McConnell, 2007.


the Highway 101 culvert and pass through the quarry to be discharged to the southerly slope and tributary to Forsythe Creek. 9. Reclamation Plan Reclamation is planned to occur after the end of each phase of expansion, from upslope to downslope as upper quarry terraces are abandoned and new extraction occurs for the subsequent phase. A total of 23.3 acres will be reclaimed by establishment of tanoak, chemise-chaparral, canyon live oak, and grassland habitats. Pilot planting will precede the end of phase 1 quarry extraction (year 2052) by 5 years, and will be implemented over 9 years, from 2047 to 2056. The four lower benches will be reclaimed over 5 years, from 2056 to 2061, after phase 2 extraction period. The quarry floor and the processing area in the northwest will be reclaimed over 5 years, from 2071 to 2076. The benefits of phased planting would be greatest if initiated at the earliest time possible for portions of mined lands that will not be subject to further disturbance (Rau Engineers, 2005a). Quantitative and qualitative monitoring and maintenance is planned to be conducted to maximize establishment of vegetation, including irrigation, weed control, and plant protection. 10. Regulatory Framework Both State and Federal regulations govern the control of water quality in California. The Clean Water Act, as amended by the Water Quality Act of 1987, is the legislation governing water quality at a Federal level. The objective of the act is “to restore and maintain the chemical, physical, and biological integrity of the nation’s waters.” Water quality regulation within California is based upon the State’s Porter-Cologne Water Quality Control Act (Division 7 of the California Water Code). The State Water Resources Control Board (SWRCB) administers water rights, water pollution control, and water quality functions throughout the State, while the Regional Water Quality Control Boards (RWQCBs) conduct planning, permitting, and enforcement activities. North Coast Regional Water Quality Control Board The North Coast Regional Water Quality Control Board (RWQCB) has primary responsibility for the maintenance of water quality in the North Coast Region. The first comprehensive Water Quality Plan for the North Coast Region (Basin Plan) was adopted by the RWQCB in 1975. Since that time, the RWQCB has updated and amended the Basin Plan several times. The RWQCB adopted the most current version of the Basin Plan in September 2006. The Basin Plan is used by the RWQCB as a regulatory tool and by other agencies for permitting and resource management. The RWQCB has the responsibility of protecting the beneficial uses of surface waters from pollution and nuisance that may be caused by waste dischargers. The goal of the Basin Plan is to define a program of actions that are designed to preserve and enhance water quality and to protect the beneficial uses of waters in the North Coast. Beneficial uses are identified in regional waters in order to assess which uses need to be protected from degraded water quality. From a water quality management standpoint, the most sensitive beneficial uses are municipal, domestic, and industrial water supply, recreation,


and uses associated with the maintenance of resident and anadromous fisheries. The beneficial uses designated for Forsythe Creek, as recognized in the Basin Plan, are summarized in Table 3.2-1. Additional water quality objectives are included in the Basin Plan, and have been developed with the intent of providing reasonable protection of identified beneficial uses and for nuisance prevention. These objectives apply to water in the Russian River hydrologic unit (HU), which includes Forsythe Creek and small drainages to it, such as the small drainage along the quarry entryway. Turbidity has not been monitored in runoff from or through Harris Quarry, but visual observations of water clarity during initial periods of runoff have included accounts of silty or cloudy runoff in the local drainage, specifically during the initial days of precipitation57. The Basin Plan allows a 20% maximum increase in turbidity above naturally occurring background levels, as measured at a downstream monitoring point. Allowable zones of dilution, within which higher percentages can be tolerated, may be defined for specific discharges upon the issuance of discharge permits or waiver58. Industrial Activity Permitting A National Pollutant Discharge Elimination System (NPDES) General Permit is typically issued by the Regional Board for Discharges of Storm Water Associated with Industrial Activities (General Permit). The General Permit regulates discharges from the quarry’s mining operations. The requirements of the General Permit typically include, but are not limited to, the following: • Prepare and maintain a Stormwater Pollution Prevention Plan; • Develop and implement stormwater best management practices to minimize

discharge of pollutants in runoff; • Conduct wet and dry weather inspections of the quarry on a regular basis; • Collect and analyze stormwater runoff at least twice per year from each discharge

location; and • Prepare and submit annual reports on stormwater management activities. Since 1997 Harris Quarry has not been required to collect stormwater runoff from discharge locations.59 The rationale for the exemption includes the risk associated with accessing and sampling the southeasterly culvert outlet of the north-south drainage, and the fact that the quarry area stormwater is retained on-site in the quarry basin, while the incoming drainages are relatively isolated from quarry area inputs. Monitoring is completed only on a visual basis from upslope.

57 Letter from Charles Martin, local resident, 2006. 58 North Coast Regional Water Quality Control Board, 2006. 59 Rau and Assoc., 2005.


Table 3.2-1 Beneficial Uses of Forsythe Creek

HYDROLOGIC UNIT/AREA/ SUBUNIT/DRAINAGE FEATURE 114.33 Forsythe Creek Hydrologic Subarea

Beneficial Use Type

Existing (E)/ Potential (P)

Municipal and Domestic Supply (MUN) E

Agricultural Water Supply (AGR) E

Industrial Water Supply (IND) E

Industrial Process Supply (PRO) P

Groundwater Recharge (GWR) E Freshwater Replenishment to Surface Waters (FRSH) -

Navigation (NAV)

Hydropower Generation (POW) P

Wetland Habitat (WET) E

Water Contact Recreation (REC-1) E

Non-contact Water Recreation (REC-2) E

Commercial and Sport Fishing (COMM) E

Warm Freshwater Habitat (WARM) E

Cold Freshwater Habitat (COLD) E Preservation of Areas of Special Biological Significance (ASBS) -

Inland Saline Water Habitat (SAL) -

Wildlife Habitat (WILD) E

Rare, Threatened or Endangered Species (RARE) E

Marine Habitat (MAR) -

Migration of Aquatic Organisms (MIGR) E

Spawning, Reproduction, and Development (SPWN) E

Shellfish Harvesting (SHELL)

Estuarine Habitat (EST)

Aquaculture (AQUA) P

Native American Cultural (CUL) beneficial use

Flood Peak Attenuation/Flood Water Storage (FLD)

Wetland Habitat (WET)

Water Quality Enhancement (WQE)

Source: North Coast Regional Water Quality Control Board, 2006. California Surface Mining and Reclamation Act of 1975 The Surface Mining and Reclamation Act of 1975 (SMARA) addresses the State’s need for mineral resources while preventing or minimizing negative public health, property, and environmental impacts of surface mining. As related to hydrologic and water quality issues, the process of reclamation includes maintaining water quality, and minimizing


flooding and erosion damage to wildlife and aquatic habitats caused by surface mining. The requirements of the SMARA apply to any surface mining operations that disturb more than one acre or remove more than 1,000 cubic yards of material60. Therefore, Harris Quarry, which would mine up to 410,000 cubic yards of material per year, and disturb approximately up to 50 acres by the end of the permit, is subject to the requirements of SMARA.61 22.16 Surface Mining and Reclamation Standards The County of Mendocino fully adopts the Surface Mining and Reclamation Act of 1975 (SMARA) and all the provisions pursuant to Chapter 22.16 of Title 22 of the Mendocino County Code and all provisions thereof. These provisions require that: • Adverse environmental effects of surface mining operations are minimized, or, if

possible, prevented, and that mined lands are reclaimed to a usable condition which is readily adaptable for appropriate alternative land uses;

• The production and conservation of minerals is encouraged, while giving

consideration to values relating to recreation, watershed, wildlife, fisheries, range and forage, and aesthetic enjoyment;

• Residual hazards to the public health and safety are eliminated. (Ord. No. 4031

(part), adopted 1999.) Additional Sections, Sec. 22.16.060 through 22.16.080, address the permit requirements and reclamation standards pertaining to stormwater discharge, erosion, groundwater, water quality, and other standards. B. Potential Impacts and Mitigations 1. Criteria Used for Determining Impact Significance Based on CEQA guidelines and other commonly accepted standards, a project would have significant hydrology and water quality impacts if it meets any of the following criteria: 3.2a Violates any water quality standards or waste discharge requirements. 3.2b Substantially depletes groundwater supplies or interferes substantially with

groundwater recharge such that there would be a net deficit in aquifer volume or a lowering of the groundwater table level (e.g., the production rate of pre-existing nearby wells or springs would drop to a level which would not support existing land uses or planned uses for which permits have been granted).

60 California Department of Conservation, 2007. Office of Mine Reclamation. Surface Mining and

Reclamation Act and Associated Regulations. 61 Yearly material extraction estimates from Northern Aggregates, 2004.


3.2c Substantially alters the existing drainage pattern of the site or area, including through the alternation of the course of a stream or river in a manner which would result in substantial erosion or siltation on- or off-site.

3.2d Substantially alters the existing drainage pattern of the site or area, including

through the alteration of the course of a stream or river, or substantially increases the rate or amount of surface runoff in a manner which would result in flooding on- or off-site.

3.2e Creates or contributes runoff water which would exceed the capacity of existing

or planned stormwater drainage systems or provides substantial additional sources of polluted runoff.

3.2f Substantially degrades water quality or results in additional siltation of either

surface or groundwater. 3.2g Places housing within a 100-year flood hazard area as mapped on a Federal

Flood Hazard Boundary or Flood Insurance Rate Map or other flood delineation map.

3.2h Places within a 100-year flood hazard area structures which would impede or

redirect flood flows. 3.2i Exposes people or structures to significant risk of loss, injury, or death involving

flooding, including flooding as a result of the failure of a levee or dam. 3.2j Is subject to inundation by seiche, tsunami, or mudflow. 3.2k Results in or requires the construction of new storm drain water facilities or

expansion of existing facilities, the construction of which could cause significant environmental effects.

2. Project Impacts The Initial Study determined that there would be no impacts for criteria 3.2g through 3.2j. because the site is not within a 100-year floodplain or an area affected by dams, levees, seiche, tsunami, or mudflows. Potential impacts addressed in this section include a) stormwater runoff volume and water quality/aquatic habitat effects from quarry expansion and b) groundwater and related water-supply effects of the proposed quarry operations. The goal of the applicant’s mining and reclamation plan is to contain all runoff within the quarry area and have no offsite runoff, except from the proposed processing area and the local haul and service roads. The surface water impact analysis focuses on providing independent verification of the ability of the plan to achieve a no net runoff goal from the quarry area, and separately, increased stormwater runoff consequences from the proposed processing area and roadway expansion. The groundwater section focuses on the potential impacts of increased use of the quarry’s well on surrounding wells and


springs, as well as the potential effects of quarry pit expansion and deepening on groundwater flow and recharge to neighboring wells and springs. Water Quality Impacts Impact 3.2-A Stormwater runoff containing sediments, metals, dust

suppressants, total petroleum hydrocarbons, oil and grease, and other pollutants associated with mining activities and vehicle and equipment use would potentially violate water quality standards and/or impact habitat.

There are three project components of the proposed Harris Quarry expansion plan related to stormwater runoff: 1) the mining area expansion; 2) the new asphalt and concrete processing area, and 3) the roadway expansion. Each has differing levels of potential impact on stormwater runoff. Mining Expansion Currently, approximately 11.2 acres drain to the quarry basin. Following grading and after the proposed reclamation, the drainage area would be increased to roughly 48.8 acres. The design intent of the proposed mining area expansion is to have no stormwater runoff leave the site, with the entire quarry floor being used as a retention basin during the wet periods of the year. This stormwater management design is different from many other quarry operations where a detention basin is used. A detention basin is a topographic feature, either natural or man-made where stormwater runoff is intercepted and detained for a finite period to reduce peak discharge volumes into downstream watercourses. A retention basin, as is proposed for Harris Quarry, is landform where stormwater runoff is intercepted and retained indefinitely for evaporation and on-site percolation into the ground. If not retained on site, the finer stormwater sediments and other pollutants (i.e., fine silts, clays, hydrocarbons) would not usually settle out of small or medium sized standard detention ponds or swales, and could potentially be transported downstream. For the proposed project, a sedimentation pond at the bottom of the extraction area has been verified as being more than adequate to hold the SMARA-required design level storm for a detention basin, while the 100-year 24-hour storms would be contained within the quarry limits.62 In the case of the proposed Harris Quarry expansion, because all the stormwater runoff is estimated to be retained onsite, as it is now, the storm water holding capacity, and not the settling time for sediments, is the appropriate design factor to consider and verify. For the Environmental Assessment and Reclamation Plan, the sediment settling pond and the basin stormflow holding capacity was calculated by Rau Engineers using the SCS unit hydrograph method for a 10-year, 24-hour storm event and a 100-year 24-hour storm event.63 According to that analysis, the proposed configuration of the quarry

62 Rau and Associates, 2006. 63 Rau and Associates, 2005. Appendix C, Stormwater Retention Analysis Report, Environmental

Assessment and Reclamation Plan.


would contain a 100-year, 24-hour storm event below the 1,832 foot contour of the quarry basin. This elevation contour is 18 feet below the first phase design elevations of the southerly quarry rim as well as the elevation of the open sump in the east end of the quarry that drains to the minor north-south drainage. These applicant-furnished retention estimates do not factor in potential storage losses due to the presence of stockpiles or other sediment accumulations on the quarry floor, which if present, would reduce the effective capacity to retain stormwater. Given the available freeboard and the rainfall estimates used, the stormwater volume detention exceeds the required SMARA standards for a detention pond, and the design of the pond would also meet required SMARA standards as a sedimentation pond. Because the quarry basin is being designed as a retention basin, rather than a detention basin, single storm event calculations do not address how much water will likely accumulate in the pond beyond a single 24-hour, 100-year storm, since previous storm events that may potentially fill the pond are not accounted for. The estimates provided by the applicant do not address accumulations of water over the entire wet season, nor do they address the eventuality of a 100-year storm occurring after previous heavy rain events. It is possible that in such an event, stormwater might not be retained and could be released at the most opportune location and elevation. Using rainfall data, evaporation, infiltration, and sedimentation estimates, a simplified water balance was created to estimate the total accumulated water volume that could occur at the site. These data were used to verify whether the retention system has adequate capacity to handle successive rainfall events. The water balance used the equation:

Vs = P – I –E+Se Where:

Vs= The volume of storage (acre feet) P = Precipitation (for December through April) I = Losses from infiltration (estimated at 0.01 cfs or 2.4 acre feet/yr ) E = Pan evaporation (December through April) Se= Sedimentation (Estimated using modest erosion rates of 2 tons/acre/year)

According to rainfall data collected by the Department of Water Resources for the Howard Research Station, approximately 1 mile to the north of Harris Quarry, average rainfall is 51.2 inches per year. The wettest water year on the record totaled 91.6 inches in 1983, while the driest totaled 30.31 inches in 1985. Precipitation for December through April for the average and wettest years was used to estimate a period when successive storms are likely to accumulate water and evaporation is lowest. Losses due to infiltration were scaled from an estimated 0.01 cfs or 2.4 acre feet/yr for the existing sediment pond. This corresponds to estimates reported in the hydrological analysis and based on observer estimates at the site. Evaporation was estimated using the yearly evaporation values for the area.64 Sedimentation was estimated from other quarry erosion estimates. Table 3.2-2 below lists the estimated accumulated winter rainfall and corresponding volume within the quarry basin.

64 UC Davis and DWR, 1999.


Table 3.2-2 Harris Quarry Required Stormwater Retention Capacity Rainfall

December to April (inches)

Accumulated Volume (ac-ft)

Average Year 36.84 148.7 Wettest Year 64.30 259.2

In the design study by Rau Engineers, the quarry’s water storage capacity was calculated using the Conic Method:

Where:

V = Volume h = height (the difference

between contour elevations) A1 = Area at bottom contour elevation A2 = Area at top contour elevation

Using this method, the available storage capacity at the higher elevation for the proposed phase 1 quarry basin, as well as a conservative estimate for the critical storage volume above which stormwater could flow out of the quarry into the adjacent drainages and slopes is 333.5 acre feet. Given these results, there is a low likelihood of runoff escaping the site due to an accumulation of runoff from consecutive rain events during an average rainy season. Under an average precipitation year, rainfall is likely to rise slightly above the 1,840-foot contour (10 feet below the quarry basin rim) and remain below the 1,845-foot quarry basin contour. For the extremely wet year (the wettest year on record), during Phase 1, water elevations would reach the 1,845-foot elevation of the basin but remain below the southerly temporary berms and the easterly berms for the sump near the scale house. The presence of stock piles and other volumes of material on the quarry floor would reduce storage capacity. Storage and work areas could also be inundated, but only in the very wettest years of record. Based on the estimates of accumulated rainfall and the water balance for the quarry basin, the proposed design and configuration of the quarry basin will retain even accumulated precipitation stormflow from very wet years. This represents a less than significant impact. Nevertheless, it is recommended that an emergency overflow be added to the quarry plan to route stormflow to a location that is the least erosion prone and would cause the least impact. This is recommended because estimates of infiltration for the planned quarry basin were extrapolated from anecdotal observations of changes of water surface elevations in the existing sedimentation pond. Actual infiltration rates may vary with the variability in bedrock as the floor is excavated, as well as the amount of fine sediments and silts that coat the quarry floor. The unlikely event of a large landslide from the quarry


face could further reduce storage capacity of the basin. The process of excavating the quarry floor to meet the Phase 1 storage capacity will take time. As the current basin is expanded, and the floor area is not increased, the capacity to retain the mean annual accumulated rainfall will be effectively reduced. The basin may be of sufficient size to settle out sediment, but in the unlikely event of quarry overflow, the route for that overflow has not been identified in the stormwater pollution plan. Processing Area An approximate 3.5-acre asphalt covered processing area is proposed to be located off of Black Bart Road, immediately northwest of the quarry. Creating the processing area pad would involve extensive site grading, including both hillside cut and fill slopes. The Yorktree, Hopland, and other soils in that area have high erosion (K) values. A slump, which is a form of mass wasting was observed at this location65. Slope stabilization techniques are planned to reduce risk of fill failure. The applicant’s plan includes fill slope stabilization and hill slope erosion control measures, which were evaluated in Section 3.1 of this EIR. Onsite stormwater would be directed and treated by site grading, an exterior curb/berm, and a system of structural best management practices before exiting the site. The site would be graded such that a 0.23-acre parking area located in the northeast of the processing pad would drain north and east to a rip rap spillway at the entrance to the quarry haul road, then to the tree and grass covered area adjacent to Black Bart Drive. This parking area would be separated from the working portion of the processing area by 0.5-foot high asphalt containment berm. To the east and south of the parking area, the approximate 3.33-acre working portion of the processing area would contain the concrete plant, the asphalt plant and truck cleanout area, a fueling area, as well as quarry rip-rap, stone, and sand product stock piles. Grading of this portion of the site would direct stormflow to the northwest where it would eventually enter a sediment cleanout basin and bio-retention swale. Total Petroleum Hydrocarbons Total petroleum hydrocarbons (TPHs) that would be used at the processing area include diesel fuel, bio-diesel (wash), gasoline, motor oil, lubricants, and asphalt oil. The processing area contains numerous potential sources of accidental TPH release, including aboveground fuel storage tanks, vehicles, and equipment. Road or parking lot TPH accumulations would enter the vegetated area south of Black Bart Drive. TPH accumulations in the larger processing area would enter clean-out basins, a common sump for the fueling area, and a bioretention swale. The area management and practices may prevent the release of TPHs from the processing area, but the potential for contributions of petroleum hydrocarbons and other pollutants associated with trucks, machinery, and the hauling of quarry products will clearly increase. The release of TPHs in stormwater discharge from the proposed processing area represents a potentially significant impact.

65 Blackburn Consulting, 2005.


Concrete Plant The concrete plant and truck washout area would include a series of three clean out or settling basins with overflow weirs that would collect truck wash and stormflow for settling and water reuse in concrete batching. The basins would be sized to allow regular cleaning and mucking by a loader to maintain storage capacity. The mucked out material would be dried and re-added to a recycle pile. The concrete plant’s proposed clean out basins are sized to handle 3,000 cubic feet, which is greater than the 2,400 cubic feet of stormflow predicted for the area under 9.62 inches of rainfall from a 100-year 24-hour storm event. A final clean-out basin will be located in the northwest of the processing area to settle out sediments before releasing storm flow to the planted bio-retention swale that extends further to the northwest. All clean-out basins would contain gooseneck shaped outlet pipes so that any overflows would come from below water surface levels and leave floating materials and constituents behind. Fueling Area The fueling area in the north of the processing area would be graded inward to direct stormflow and any spilled fuel to a dedicated sump. The sump would collect surface runoff, contain spills, and facilitate spill clean up. The sump would also have a gooseneck outlet to retain floating constituents. An overflow would release stormwater to the general processing area and eventually to the final settling basin and bio-retention swale in the northeast. Asphalt Plant The asphalt plant would be located in the south of the processing area. Asphalt loading will be conducted in this area, as well as asphalt oil storage and deliveries. This area has no special protective berm other than the curb surrounding the processing area. Bioretention Swale With the exception of the parking area, the processing area’s stormwater would eventually drain through a settling basin, and a planted bio-retention swale. Any stormflow leaving the swale would be passed through an overflow and underflow (buried) pipe, then discharged to a rock diffuser, and finally to the existing small grass and tree lined slope, 750 to 1200 feet above Forsythe Creek. The purpose of the bio-swale is to mitigate the concentration of flow from the processing area and any erosion, riling, and gullying on the adjacent hill-slopes, as well as to filter out sediment and chemical constituents that could impair water quality in Forsythe Creek. This would be achieved by allowing stormwater to evenly infiltrate and pass through the swale before being released. Bio-retention swales have been shown to remove pollutants such as phosphorus, metals (Cu, Zn, Pb), nitrogen (TKN), solids, organics, and bacteria at removal rates ranging from 68-98%.66 In order to handle runoff effectively, a bioretention swale must be

66 The California Stormwater Quality Association (CASQA), January 2003. California Stormwater BMP

Handbook. Bioretention. TC-32.


appropriately sized for the area that it drains. Depending on the method used, sizing estimates can vary significantly. The source referred to in the process area plan for design criteria, “TC-32, Bioretention” by the California Stormwater Quality Association (CASQA), does not provide sufficient sizing recommendations and may be inadequate for an area such as the large processing pad. It recommends minimum sizes, without relationship to the area being drained. Other design and maintenance recommendations contained therein have definite value and should be followed. Also cited in the processing area plan, and included as attachment G, the “EPA Storm Water Technology Fact Sheet – Bioretention” prescribes estimating the size of a bioretention area using the following equation: 67

A = .5 x da x C (used for sand lined swales), or A = .7 x da x C (used for swales without sand) Where: A = design area of the bioretention area Da = drainage area C = runoff coefficient

Using this method to size a sand-lined bioretention area, and using a range of estimated runoff coefficients, a bioretention area from 1.3 to 1.7 acres is required (see Table 3.2-3). It should be noted that this design method was developed for areas of the east coast with larger storm events than the project area.

Table 3.2-3 Harris Quarry Processing Area Bioretention Swale Estimates

Processing Area estimate (acres)

C-value

Required Bioretention (acres)

Estimated for an asphalt surface with stock piles

3.5 0.75 1.3

Estimated for an asphalt surface without stock piles

3.5 0.95 1.7

Process Area Plan swale size68 - - 0.22

The 1.7-acre upper value estimate for the processing area is a conservative estimate. It uses a runoff coefficient C-value of .95 for an all asphalt surface, with no stockpiles. The values provided in the processing area Stormwater Pollution Prevention Plan included a

67 USEPA, 1999. 68 Northern Aggregates, 2005. Process Area Plan for Harris Quarry.


drainage area of 3.5 acres, with 25% of that area being covered by quarry product stockpiles, and a combined C-value of 0.725. With these values, a swale of 1.3 acres or 55,267 square feet would be required. The applicant-proposed bioretention area as stated in the process area plan (0.22 acres or 9,625 feet) is significantly smaller than the estimated bioretention requirements using the proposed sizing methods. Even for the most optimistic case, the planned bioretention swale does not fit the lowest predicted amount of runoff using the EPA fact sheet as the design basis using the proposed sizing methods. Other methods for designing bioretention swales allow for customizing the size of the swale’s width, length, depth, flow depth, and other elements for the required amount of stormflow, pretreatment, soil types, and the type of vegetation to optimize the function of the swale. An important design goal is to reduce flow velocities within the swale to reduce erosion potential and allow for infiltration. The flow depth should be appropriate for the vegetation being planted and maintained within the bioretention area. Estimating the size of the required swale should be based on estimates that include site runoff, site soils, slope, swale vegetation, infiltration time, and space available. Swale design is often an iterative process and is generally based on the Manning’s equation.69 For an undersized swale under heavy rain events, flow exiting the swale will be greater than that which normally drains to that area. As such, there is a potential for erosion within the drainage at the swale outlet and further down slope where existing dirt roads traverse the area. A swale design, maintenance and monitoring plan that meets site characteristics and design standards using low impact methodology has not been proposed, and is required for treatment of runoff from the processing area. This represents a potentially significant impact. Roadway Expansion The quarry access road expansion and new haul road would result in increased runoff and transport of associated pollutants to the minor north-south running drainage paralleling Highway 101. Although some background stormwater pollution may be attributed to runoff from Highway 101, additional runoff and pollution inputs may be significant, considering the increased transport of aggregate, asphalt, and concrete, and associated potential for spillage problems.

69 where: Q =Flow, (Q=VA, where V is velocity and A is area) n = Manning’s n (0.3 for rough grasses) Rh = Hydraulic radius (Rh= A / (Wb + 2y) for rectangular channels S = Slope of swale (1% to 2%) A = Cross-sectional area y = Flow depth (approximated at 2 inches) Wb = Swale bottom width

See Low Impact Development (LID) Urban Design Tools. 2007. (http://www.lid-stormwater.net/) and (http://www.lowimpactdevelopment.org/epa03/LIDtrans/Ex_Swale.pdf).


Runoff from the existing and planned roads was calculated using the rational method with C coefficients for gravel and asphalt surfaces (0.8 and 0.95 respectively). Other contributing areas to the downstream drainage include the forested area south of Black Bart Drive, and the south-facing slope, south of the quarry. If stormwater is concentrated and rapidly delivered to a drainage system, then erosive effects are usually intensified. If stormwater is detained in swales, or returned to forested areas, these effects can be diminished and mitigated. For the proposed section of road between the quarrying area and the processing area, stormwater is planned to be returned to the forested area in two locations where it can infiltrate or be detained. For the newly paved quarry access road, stormwater would drain directly to a newly installed culvert. This unattenuated flow could represent an .04 cfs increase, which represents a small fraction of flow contribution by the project area watershed. As noted in the site investigation of the north-south channel, south of the quarry, significant incision has already occurred in the channel below the culvert outfall. Bank failure is also evident in one location farther downstream. The additional unattenuated flow and potential polluted stormflow from paved road contributions would slightly increase these effects. This represents a potentially significant impact. Total Petroleum Hydrocarbons Total petroleum hydrocarbons (TPHs) that are used at the quarry include diesel fuel, gasoline, motor oil, and lubricants. The quarry contains numerous potential sources of accidental TPH release, including above ground fuel storage tanks, vehicles, and equipment. Currently any road accumulations enter the north-south drainage with natural channel buffer. Harris Quarry’s management and practices may prevent the release of TPHs from the quarrying area; however, it is not currently possible to know if these pollutants are being released into receiving waters at significant levels. Stormwater sampling by the quarry has not been conducted to date and has not included analysis of total petroleum hydrocarbons (TPHs). The planned road runoff would also drain to the north-south tributary. It is planned that future road runoff will leave the paved roadway via storm drains and go directly to a new 290-foot long culvert system that will replace the existing open channel70. The potential for additional contributions of petroleum hydrocarbons and other pollutants associated with trucks, machinery, and hauling quarry products will also increase. The release of TPHs in stormwater discharge from the quarry road expansions represents a potentially significant impact. Conclusions The expansion of the quarry including the processing area will result in more highly disturbed areas potentially subject to erosion. Even though stormwater and sedimentation in the active mining area will remain on the site during a normal precipitation year, greater than average amounts of precipitation could inundate storage and work areas on the quarry floor, especially until the first phase of the quarry floor configuration and storage capacity is reached. Planned best management practices for the processing area and new roadway will greatly reduce the risk of pollution and

70 Jason McConnell, personal communication, May, 2007.


erosion due to stormwater runoff. For the processing area, the proposed bioretention swale, if sized appropriately will diminish flows to the slopes above Forsythe Creek. The proposed rock energy dissipater will also mitigate stormflow. The swale design currently contains no method to distribute flows evenly across its proposed 35-foot width. Concentration of larger than average storm events could also initiate erosion and gullying in the drainage downslope from the swale outlet. The proposed paved quarry access road will contribute a small increase in runoff and road pollution. The extensive length of the proposed permit and extent of expanded operations increase the potential for some of the above impacts to occur. This represents a potentially significant impact. Mitigation Measures The following mitigation measures are designed to ensure that the proposed expansion project will not discharge more suspended solids or other pollutants than the existing quarry does (under baseline conditions). This will be achieved by requiring that the applicant revise and supplement the soil erosion and sediment control plan with more detailed, rigorous and comprehensive plans including preventative measures to prevent erosion and sources of pollution for the proposed project. Also, drainage from roadways, fill slopes, the processing area, and the post reclamation slopes shall be attenuated to reduce the flow of water and sediment to the north-south drainage and Forsythe Creek. Many of these mitigation measures are based on implementation of current best management practices for controlling erosion and sedimentation and removing pollutants from stormwater. The extended permit period requested by the applicant limits the ability of the County to require additional mitigations that may be warranted given changed conditions or new techniques that are developed over the next several decades. Therefore, this EIR recommends that the County consider a defined permit period, after which the applicant can request a permit renewal, and/or a permit review process. See the discussion of the permit length in Section 3.13, subsection 5 of this EIR. 3.2-A.1 The applicant shall construct and operate the project in a manner that avoids

the escape of pollutants into the environment and prevents the entry of such pollutants into Forsythe Creek. The applicant shall design and implement a comprehensive water quality protection program to meet this standard. In addition to the measures proposed in the project application, the program shall include measures 3.2-A.2 through 3.2-A.8 described below. The program shall be submitted to the County Water Agency, and the North Coast Regional Water Quality Control Board (RWQCB) for review and comment and shall be subject to approval by the County Water Agency. The program shall include water quality performance criteria that define what levels of sediment, turbidity, iron, and other factors will be allowed in the stormwater that leaves the processing area.

In no case will the amount of total suspended sediment (TSS), Total Petroleum Hydrocarbons as Diesel (TPH), iron, specific conductance, or pH in the stormwater leaving the site be allowed to exceed the levels coming off the site under baseline conditions. Stormwater from the project site will not be


allowed to increase the turbidity of Forsythe Creek beyond limits set forth in the Basin Plan or by the RWQCB. The baseline conditions will be established by the RWQCB, based on the results of a stormwater runoff sampling program that is implemented prior to quarry pit expansion.

Regardless of what the baseline conditions are, if the stormwater exceeds the water quality benchmarks listed below, additional measures (as described in the subsequent mitigations in this section) may be required by the RWQCB in order to improve the quality of the stormwater leaving the site.71

Water Quality Benchmarks The water quality benchmarks are based on the State Stormwater Pollutant Benchmark levels. The benchmarks are used by the RWQCB to determine when additional pollution control may be required for a project. They include:

• PH – should be between 6.5 to 8.5; • Total Suspended Solids (TSS) – not greater than 150 and 190 mg/L; • Specific Conductance – not greater than 320 uS/cm; • Iron – not greater than 300 ug/L; and • Total Petroleum Hydrocarbons as Diesel (TPH) – not greater than 15

mg/L.72 • Other constituent levels as specified in Table 3-2 of the North Coast

Basin Plan. 3.2-A.2 The applicant shall revise and implement an updated stormwater pollution

prevention plan for the quarry area and processing area. The erosion control portion of the SWPPP shall include an aggressive sediment source and delivery control program. It shall place greater emphasis on establishing temporary and permanent protection of disturbed fill slopes and drainages in the processing areas that drain to Forsythe Creek. Most importantly the plan must include a yearly winterization report that documents the location and application of best management practices to mitigate reduction in water quality due to storm runoff containing sediment. The required SWPPP, including the detailed erosion control plan shall also include:

• A formal plan for preventing the inadvertent side cast of materials from

the quarrying area entering the north-south and east-west drainages. • Stabilization of all fill slopes prior to October 15 of each year. The plan

shall include a detailed design plan for annual stabilization. Stabilization

71 Baseline conditions under CEQA are defined as existing conditions as of the date of the Notice of Preparation. Baseline conditions would be the quality of water leaving the project site. For regulatory stormwater quality permitting purposes, baseline monitoring is defined as the period during which water quality sampling and analysis is completed, which must be approved prior to the initiation of an action or change by the applicant.

72 90% or more of the values must be less than or equal to an upper limit and greater than or equal to a lower limit. North Coast Regional Water Quality Control Board, 2006.


measures include fill slopes suitable for hydraulic application of surface stabilizing compounds, hydroseeding, mulching, or other measures to prevent erosion, and the application thereof. It shall include a description of the erosion control materials to be used and application rates. Seed mixes shall be specified. A schedule for completion of stabilization shall be included, and the stabilization shall be completed by October 15 each year. To insure accurate compliance with this condition the applicant shall submit to the County a site plan or aerial photograph clearly depicting the extent of mining, best management practices, and reclamation implemented on the site prior to October 15. This shall be conducted during mining and reclamation and at the completion of reclamation.

• The site plan shall show work areas, indicating the year the initial

reclamation occurred, active mining, stockpiling, work areas, and areas to be mined the following year.

• The site plan shall show erosion and drainage problem areas, and

proposed emergency stormwater runoff flow directions, in addition to the planned retention, bioretention, and treatment areas.

• Place all hazardous materials and fueling areas above predicted 100-year

24-hour flood elevations and above observed seasonal high-water elevations.

• A plan to annually monitor and treat stormwater outlets that discharge to

slopes and drainages to insure that gullying, incision, or other erosion and mass wasting processes are not occurring as a result of project area operations and site drainage.

• A stabilized emergency stormwater overflow shall be designed and

constructed for the quarry. It should be installed in the eastern portion of the quarrying area, either in the existing sump near the scale house, or in the southeast at the old Highway 101 roadway. The exact location and design shall be prepared by the applicant's engineer and is subject to further review and approval by the County. The outlet of the overflow shall be rocked and stabilized such that there shall be no significant erosion during potential emergency overflow conditions or during more frequent rain events.

• An energy dissipater and channel protection device shall be designed and

installed in the north-south tributary to Forsythe Creek, south of the quarrying area, to stabilize the active channel incision. The design will be provided by the applicant engineer and is subject to review and approval by the Mendocino County Water Agency and the Mendocino County Department of Planning and Building Services.

3.2-A.3 During mining and reclamation activities, the following measures shall be

implemented to reduce the potential for erosion and sediment discharge:


• Topsoil suitable for use in revegetation shall be stockpiled in a stable

manner for use in reclamation and replanting of cut slopes. Prior to October 15 of each year, all topsoil stockpiled for future use in revegetation shall be seeded and mulched in order to prevent soil loss through erosion. Topsoil shall be stored in locations that are not above or adjacent to stream drainages.

3.2-A.4 Implement best management practices to reduce the potential for discharge

of contaminants to stormwater runoff. To minimize the introduction of contaminants which may degrade the quality of water discharged from the site, the following measures shall be taken:Runoff from the access roads shall be collected and passed through a treatment swale or trap system prior to entering the existing or planned drainage features for the north-south drainage or before it leaves the south end of the quarry.

• Fueling and maintenance of all rubber-tired loading, grading and support

equipment shall be prohibited within 100 feet of drainage ways. Fueling and maintenance activities associated with other less mobile equipment shall be conducted with proper safeguards to prevent hazardous material releases. All refueling and maintenance of mobile vehicles and equipment shall take place in a designated area with an impervious surface and berms to contain any potential spills.

• All chemical dust suppressants and slope stabilization chemicals or polymers, and sediment detention basin enhancement chemicals or polymers shall be used strictly according to the manufacturer’s specifications. An accurate accounting of all these materials purchased and used on the site shall be maintained, including kinds and quantities of material.

• Prior to project approval, the County Engineer shall evaluate the design, implementation, and plan for maintenance and monitoring for the bioretention swale for the processing area. The swale shall be designed to treat stormflow using design recommendations by Caltrans in its Storm Water Quality Handbook - Project Planning and Design Guide and Design of Biofiltration Swales and Strips (2007), and Low Impact Development (LID) Urban Design Tools (2007).73 During the operational period of the swale, flow shall be evenly distributed across its width and should not cause erosion within the swale. The bioretention swale shall be inspected and maintained to assure proper function at least twice each winter, and after each major storm event. The slopes at the swale outlet, down slope areas and roads shall be monitored and treated for any gullying or erosion that may occur over the permit period.

It appears that there is enough available land for a larger bioswale if the design is well

73 It appears that there is enough available land for a larger bioswale if the design is well thought out to

account for hill slope and soil properties. If the area is limited, to meet the required design standards, the design shall focus on source control and optimize treatment through use of innovative approaches.


thought out to account for hill slope and soil properties. If the area is limited, to meet the required design standards, the design shall focus on source control and optimize treatment through use of alternate approaches in order to comply with Mitigation Measure 3.2-A.1.

3.2-A.5 Collect baseline data for a monitoring program (these are the same baseline

data referenced in Mitigation Measure 3.2-A.1 above). The stormwater monitoring shall be conducted for at least a single season to collect a series of baseline samples during representative storm events. The consulting firm performing the monitoring on behalf of the applicant shall develop a water quality monitoring program in coordination with the County and the Regional Board. The stormwater monitoring program shall include the following: • The monitoring program shall be conducted by a qualified third-party

water quality consulting firm that is approved by the County and paid for by the applicant.

• Collect a minimum of four baseline samples of runoff from upstream and downstream locations to determine background water quality. The baseline sampling locations shall be selected in areas away from processing activities and other human disturbance and sampled at least four times at each location during the single rainy season. The baseline locations shall include: the bioretention swale outlet ditch and Highway 101 discharge points immediately upstream of the quarry, and downstream of the quarry, where accessible, or prior to leaving the sump near the scale house.

• Baseline water quality analysis shall include: pH, TDS, TSS, turbidity, TPH-diesel, and oil and grease.

• As proposed in the processing area Stormwater Pollution Prevention Plan, stormwater samples shall be collected at the outlet of the bioretention area and any location stormflow leaves the processing area pad.

3.2-A.6 Upon request of the RWQCB, CDFG, or the County, or if baseline water quality values exceed the State Stormwater Pollutant Benchmark levels, the applicant shall collect semi-annual representative samples (or more frequent samples if required by RWQCB, CDFG, or the County) from all stormwater discharge outfalls (at the location where the discharge leaves the quarry area and the processing facility area or where access is available) while discharges are occurring. This sampling would be used to determine consistency with the performance criteria set forth in Mitigation Measure 3.2-A.1. The following sampling shall be performed:

• Collect samples upstream and downstream of the quarry stormwater

outfalls to the north-south drainage during discharges from the site where accessible, such as at the scale house sump (at the same frequency as described above).

• All of the semi-annual samples shall be analyzed for pH, TSS, turbidity, specific conductance, and total organic carbon, total and dissolved iron,


magnesium and calcium, TPH as diesel (with silica gel clean-up), alpha-olefinsulfonate (if CDS 8040 is used for dust control), and any polymers by a State-certified analytical laboratory.

• The surface water quality data shall be analyzed semi-annually or as determined by the RWQCB by a qualified professional for exceedance of the water quality performance criteria and/or changing conditions in water quality that could indicate a potential impact to water quality.

3.2-A.7 The applicant shall submit a monitoring report to the Regional Water Quality

Control Board with a copy submitted to the Mendocino County Water Agency and the Mendocino County Department of Planning and Building Services. Frequency of reporting will be determined by the RWQCB but shall not be less than once each rainy season. For water quality sampling, a qualified water quality professional conducting the monitoring shall provide an analysis of the data and an evaluation of the overall effectiveness of the sediment control system. If the water quality performance criteria have been exceeded, the report shall include the expert's opinion regarding the specific causes of the exceedances. The monitoring report will include winterization BMPs put in place prior to each rainy season and status of the drainage below each stormwater outfall.

3.2-A.8 Repair storm damage, as necessary. Following storm events which

significantly damage (i.e., erosion or rainfall-induced land sliding) the reclamation areas, the operator shall have a qualified professional conduct a damage survey of the reclamation improvements, and recommend remedial actions as necessary to help assure that the performance standards will be met. A report shall be submitted to the Mendocino County Water Agency and the Mendocino County Department of Planning and Building Services regarding the effects of such damage, including recommendations for replanting, if necessary.

Impact Significance After Mitigation The mitigation measures provide an appropriate method for delivering runoff from the quarry to the adjacent tributary in case of a record wet year and unforeseen conditions on the quarry. They address the problem of the existing erosion on the north-south drainage that drains highway and project access road drainage. The mitigation measures also require that the runoff from the site, including the processing facility, meet or exceed the water quality performance criteria for the life of the project. Stormwater runoff from the processing area will not be allowed to increase sedimentation or any other water quality criterion in the stormwater runoff. The above-noted measures would ensure that impacts to water quality per the Water Quality Plan for the North Coast Region would be reduced to a less than significant level. The turbidity would not exceed baseline conditions by more than the Regional Board allowed 20%, so there should be no adverse impact on water quality as regards fish and aquatic wildlife inhabiting Forsythe Creek or the Russian River. The mitigation measures ensure ongoing monitoring best management practices and provide appropriate discretion to the County and the RWQCB to require additional monitoring, erosion control devices, and practices,


or, if compliance cannot be reached, to close quarry operations if compliance cannot be realized. The recommended measures to be included in the water quality protection program would reduce the impact to water quality to a less than significant level. Changes in Runoff Impact 3.2-B Quarry expansion and use will decrease runoff to

Forsythe Creek. The quarry expansion and reclamation process includes the removal of vegetation, overburden material, and significant changes to the topography at the project site. The removal of vegetation and overburden material (i.e., soil) will lower infiltration on the site surfaces by exposing bedrock to rainfall. This will increase erosion rates delivered to the quarry floor. Although hillslopes and benches will be revegetated as part of the reclamation, the soil plant cover will be significantly different from native conditions, and post-reclamation infiltration will be limited compared to that of the existing undisturbed slopes. Because the quarry will act as a retention basin for the expanded quarry area, net discharge could decrease and groundwater infiltration from the quarry basin may increase, primarily during the winter months. Currently, approximately 11.2 acres drain to the quarry basin. Following grading and after the proposed reclamation, the drainage area would be increased to roughly 48.8 acres. The new asphalt haul road and quarry access road will capture and route runoff to the north-south drainage. Discharge for the haul road is planned to be intercepted and released to two locations in the existing forested area along Black Bart Drive before eventually continuing as overland flow to the north-south drainage. The Rational Method was used to estimate peak discharge (runoff) from the project site and watershed for existing and post-reclamation conditions. The peak discharge was estimated for the 2-, 25-, and 100-year design storms. The rainfall intensity was based upon the rainfall intensity/duration curve equations by the Department of Water Resources. The runoff coefficients used in the analysis are summarized Table 3.2-4. The contributing watershed area was divided into several smaller drainage areas for a more accurate estimate of runoff.

Table 3.2-4 Runoff Coefficients Used in Rational Method Analysis

Land Type Runoff Coefficient Undisturbed (forest) 0.15 Undisturbed (grassland) 0.30 Reclaimed 0.65 Actively mined / bare earth 0.80 Paved roadway 0.90


The estimated decrease in runoff at the project site over the existing conditions is on the order of 90 percent (Table 3.2-5). To put the change in context, the project represents 2% of the larger upper Forsythe Creek drainage area. For the upper Forsythe Creek watershed, the decrease in discharge represents a small and less than significant change over the existing conditions. The project, at a worst case, would decrease the flow in upper Forsythe Creek by 0.3%. A portion of the water captured by the basin would eventually be returned via groundwater flow. The change in discharge is of a magnitude that would not affect the receiving channels, other than a very small decrease in peak flow water surface elevations in Forsythe Creek.

Table 3.2-5

Rational Method Peak Discharge Results Peak Discharge, Q (cfs)

Storm frequency

Existing condition

Proposed expansion Post-reclamation

Percent

decrease 2-year 9.0 7.8 7.0 86.7% 25-year 14.1 13.4 11.8 95.0% 100-year 18.5 16.1 12.9 87.0%

Increases in runoff to the north-south drainage from newly surfaced roads would be offset by increased capture of the quarry basin and a decrease in the total contributing area. The reduced time of concentration on the roads could potentially continue to exacerbate downstream erosive effects in the north-south drainage and subsequent sediment contributions to Forsythe Creek. This potential erosion impact was addressed in the previous impact, and mitigation was recommended for that impact.

Table 3.2-6 Discharge Results, Upper Forsythe Creek Watershed

Peak Discharge, Q (cfs) Storm frequency Existing condition Post-reclamation

Percent decrease

2-year 7.3 6.54 0.06% 25-year 202.1 181.30 0.07% 100-year 1,060.9 949.48 0.07%

The changes in runoff would have a less than significant impact on flows in Forsythe Creek. Groundwater Recharge Impact 3.2-C Quarry activities may result in reduced groundwater

recharge to area streams, including reduced summer base flow.

The proposed lowering of the quarry floor to an elevation of 1,650 feet would bring the floor to the same channel bottom or thalweg elevation of Forsythe Creek 1,500 feet southwest of the quarry. The proposed quarry bottom would be below the elevation of the thalweg of the ephemeral tributary 1,000 feet to the immediate south of the quarry. The concern is that slow moving fracture flow may provide an important component of


summer base flow and that the quarrying activity would intercept groundwater now flowing in the rock fractures towards the creeks. Or alternatively, if the pit bottom were slightly lower than the creek bottoms, that flow would reverse direction and move from the creeks to the pit. No springs or seeps have been mapped as occurring on the slopes above Forsythe Creek or the ephemeral stream to the south of the quarry, which would provide one indication of subsurface preferential flow through rock fractures. At this time, the potential for horizontal seepage to flow through the fractured bedrock geology between the Forsythe Creek or the local tributary and the quarry basin is not well understood. The nature of fractured bedrock geology within the Franciscan formation complex makes prediction of groundwater elevations and transfers subsurface flow quantities and direction very difficult. Examples of stream or groundwater capture by quarries do exist, but none have been found reported for Franciscan formation complex fractured bedrock geology. Potential for stream flow capture by the pit can only be partially ascertained by test drilling through the quarry bottom in one or more locations to the planned excavation depth, and determining the occurrence depth and direction of groundwater flow. A 500-foot dry well is located in the east of the quarrying area, indicating a low likelihood of interception of fracture flow in this immediate area. Because the quarry pit will act as a retention basin, infiltration and fracture flow from the quarry will likely could potentially increase during the wet periods of the year. In addition to concerns that a deep pit would somehow capture or drain summer low flow or base flow from Forsythe Creek into the pit, there is also a concern that quarrying could intercept groundwater flow moving through rock fractures that currently supplies important summer base flow to Forsythe Creek. As discussed in more detail in Impact 3.2-D below, Questa’s analysis of the hydrogeology and groundwater conditions of the Harris Quarry area found that although the bedrock is locally highly fractured, there does not appear to be a well-connected network of rock fractures within the quarry expansion area that stores or transmits groundwater. Because the potential for capture of stream water exists and is not fully understood, this represents a potentially significant impact. Mitigation Measures 3.2-C.1 No mining will be permitted below the thalweg of the adjacent tributary of

Forsythe Creek unless additional geohydrologic studies are conducted that show that there is no hydraulic connectivity between the quarry and the tributary. If the applicant wishes to excavate deeper, the applicant shall conduct additional studies of the potential effects of the quarry excavation on groundwater flow towards the tributary of Forsythe Creek. This may include review of existing wells completed within the fractured bedrock, the estimated volume of affected groundwater, the potential affects of the lost groundwater on Forsythe Creek, if any, and the recommendations for measures to reduce the impact to area streams, if necessary. The analysis should review the need for the installation of additional monitoring wells at least as deep as the project quarry pit bottom, These studies shall be submitted to the County for a permit revision, subject to CEQA review.


3.2-C.2 Mitigation Measure 3.2-D.1 requires completion of a hydrologic investigation and spring monitoring. This hydro-geology investigation shall include a detailed examination of the conjectured fracture/shear zone north of the quarry and an annual examination of the rock fractures on new quarry faces for hydrologic connectivity to Forsythe Creek. This can be done with the already required rock face slope stability analysis.

Impact Significance After Mitigation The mitigations ensure that the project would not adversely affect streamflow in Forsythe Creek. If the applicant in future decades seeks to mine to the elevation proposed in this application, additional technical studies would be required to assess subsurface flows beneath the tributary and whether mining below the elevation of the creek would capture any then existing subsurface flows. The mitigations reduce the impact to a less than significant level. Effects on Groundwater Resources Impact 3.2-D The project could adversely affect groundwater

resources. The proposed expansion includes increased use of water pumped from area wells and springs. As additional water resources are used for aggregate processing and concrete production, local groundwater resources could be affected. In addition, quarry activities could affect how water moves through rock fractures, potentially changing recharge patterns, as well as flow rates in wells and springs. Water from the on-site wells and, if needed, nearby springs owned by the applicant will be used for aggregate washing and production at the ready-mix plant and for dust control. Harris Quarry plans to use an aggregate wash water recycling system which could reduce wash water requirements by 50%74. As roads are paved, water required for dust control will decrease. Increased production due to the expansion of the quarry would require more water for materials processing and interim dust control. Groundwater quality could be impacted if water contaminated with fuel or other mobile pollutants is allowed to infiltrate at the site. Groundwater Quality Groundwater is at a depth varying seasonally between about 25 to 50 feet below ground surface in nearby wells and springs (near the 2020 foot elevation), however, depth to groundwater beneath the quarry floor at the site is not known. A well drilled to 500 feet in the southeast corner of the quarry was found to be dry. This supports the hypothesis that groundwater is contained only locally (and at difficult to predict locations) within fractured and weathered zones in the underlying bedrock. Groundwater quality at the site may be impacted by accidental spills or leaks if immediate action is not taken to remediate the spills; however the applicant already has a sufficient spill prevention plan in place. No other groundwater quality impacts are likely

74 Northern Aggregates, 2005.


to occur as a result of the expansion and reclamation project. This represents a less than significant impact. Groundwater Quantity Project Impacts on Immediately Neighboring Wells and Springs Potential groundwater-related impacts associated with quarry expansion including pit deepening and continued and expanded use of the quarry well can be divided into four categories for discussion purposes:

• Adverse Well Interference • Groundwater Withdrawal in Excess of Recharge • Local Fracture Flow Disruption • Quarry Pit Deepening Impacts on More Distant Wells and Springs

1. Quarrying Activities May Have Adverse Well Interference Effects Well interference refers to the groundwater drawdown effects on neighboring wells from the pumping of a given well or group of wells. The extent of the effect, if any, depends on a number of factors including the distance between wells, pumping rates, and the general nature and hydraulic properties of the aquifer. Generally, the best way to determine potential well interference effects is through the completion of a pumping test (as was completed for the applicant by Rau, 2007) in which water levels in the pumped well and an adjacent well or wells are monitored during the pumping period and a recovery period following completion of pumping. Knowledge of well construction details in the pumping and monitoring of wells and a general understanding of the hydrogeology are necessary to properly interpret the test data. Well interference effects can occur both short term, via local pumping cone of depression effects, or long term, via groundwater withdrawn in excess of recharge rates that lower local groundwater levels, sometimes below the depth of nearby existing wells (See section #2 below). Based on the applicant-furnished pump test results, the response of the monitoring wells to the pumping of Well #1 leads to the conclusion that there is not a good direct hydraulic connectivity among the groundwater bodies surrounding the quarry well and the two monitoring wells. Connectivity in these aquifer materials relies on good connections among major, intersecting rock fracture zones. Adverse well interference effects between the on-site quarry well (during extended and heavy use periods) and the more outlying wells (such as some of the closer Ridgewood Subdivision area wells) is remotely possible but is expected to be very minimal since groundwater connectivity is expected to be very low:

• to the south, (through the primarily non- water-bearing hard rocks of the quarry area),

• to the east, (because of blockage by the Maacama fault zone), and • to the west (because of the occurrence of Forsythe Creek, and a ridgeline further

southwest).


There does not appear to be any wells or springs to the immediate north of the quarry that are not on quarry property. The pump tests can be interpreted as indicating no potentially significant effects on the near-by monitoring wells, and no significant impacts are expected to occur for any well further to the northwest that are not included among the springs and wells on Figure 3.2-2. The presence of the band of highly weathered and fractured rock to the north that may trend transverse (northwest-southeast) through the quarry would likely preclude any adverse well interference effects from extending beyond the band further to the north as the fractures would intercept and divert flow to the west. Based on the above analysis, it is concluded that potential well interference effects would be a less than significant impact. 2. Quarrying Activity May Cause Groundwater Withdrawal in Excess of Recharge. Groundwater withdrawal (by heavy pumping) greatly in excess of the storage and recovery or recharge capabilities of an aquifer is sometimes termed “groundwater mining”. The “fair-share” principle has been used to evaluate this issue in other areas of northern California. Under a fair share use analysis for CEQA purposes, allowable groundwater use is considered to be equal to the long-term average natural rainfall recharge to the groundwater body that occurs within the parcel in question. CEQA analysis is different than California Water Law, as it is generally recognized that the owner of a well (in a non-groundwater adjudicated basin) has the right to underlying groundwater, as long as it is beneficially used and not transported outside of the basin of origin. Groundwater recharge for the project area was estimated by the annual water budget method. In this method, Mean Annual Runoff (Roff) and Mean Annual Evapotranspiration (ET) are subtracted from Mean Annual Precipitation (Ppt) to estimate the total amount of incident annual precipitation that is available for Annual Recharge (Rchg.).

(Rchg = Ppt - Roff - ET). For the Harris Quarry Area; Mean Annual Rainfall (Ppt) is estimated to be 51.3 inches per year; Evapotranspiration (ET) is estimated to be 16.2 inches for November through June, the time when water can percolate into the bedrock aquifer.75 Mean Annual Runoff is estimated to be about 31.5 inches.76

51.3" Ppt – 31.4" Roff – 16.1" ET = 3.8" Annual Recharge; This represents runoff of about 7% of the annual rainfall, a credible estimate given the average slope, soils and underlying geologic materials of the project area.

75 Evapotranspiration estimated from rates for the Ukiah area published by UC Cooperative Extension,

updated 2000. 76 McKee et al., 2003. A Review of Urban Runoff Processes in the Bay Area. San Francisco Estuary

Institute.


It is estimated that there is currently approximately 3.8 inches of recharge available per year (0.30 acre-feet per acre per year) of aquifer recharge, or 101.7 acre feet from rainfall on the project area lands owned by the quarry operator (~335.3 acres of the applicant’s parcels on which the project is located). The quarry operator/applicant owns a much larger parcel than that of the quarry operations. If only the lands immediately involved in the quarrying and processing are considered, the estimated total average annual recharge for the local area of the Harris Quarry project is estimated to be 78.2 acre-feet, while the recharge for the parcel that contains the quarry’s well is 23.7 acre-feet. The well is predicted to produce 24.2 acre feet/year and water use is predicted to be about 19.9 acre feet per year. The amount of well water expected to be used (19.9 acre feet per year) is within the ‘fair share’ concept of annual groundwater recharge on land controlled by the applicant (23.7 acre-feet /year). 3. Quarrying Activities May Cause Local Fracture Flow Disruption and Spring Flow

Interception If a band of fractured and highly weathered bedrock that transmits groundwater over some distance does occur as inferred from the geologic data, then there would be a concern that rock quarrying activities could somehow disrupt or intercept groundwater flow moving within this zone. This could potentially impact spring flow for the springs located in this band. This is not likely to occur as rock quarrying is not proposed within what Questa has identified as a possible band of highly weathered and fractured or sheared rock that contains most of the wells and springs. As previously indicated, local groundwater is inferred to be present within this band, but not likely present in appreciable quantities to the south of the band in the proposed quarrying area. The proposed quarry expansion stops short of this band. In addition it appears that the spring on Black Bart Drive used by some of the neighbors, and located to the west and north of the quarry is topographically at an elevation above the quarry by about 80 feet. Therefore, physical disruption of any such weathered rock or shear and fracture zones that serve to transmit flow laterally (and hydraulically upgradient) is not likely. However, it should be emphasized that the present understanding and knowledge of fractured rock hydrogeology of this area is incomplete and has primarily been inferred based on a field reconnaissance and interpretation of available geologic and hydro-geologic information. Because of the uncertainty of potential impact on springs and the importance to local water supply, this is considered to be a potentially significant impact. 4. Quarry Pit Deepening May Impact More Distant Wells and Springs (within 2 Miles). There is the possibility that excavating a deep quarry pit could physically disrupt groundwater moving through rock fractures, and therefore change patterns of water moving to (and currently through the quarry) and recharging surrounding wells within a larger potential impact area extending beyond the proposed quarry boundaries. Based on Questa's review of the geology and groundwater hydrology of the Harris Quarry area, and their experience with other areas where small rural residential wells are located within fractured bedrock, they conclude that there will be no significant impacts from quarry expansion, including quarry deepening, on neighboring and more distant wells and springs.


Furthermore most of the surrounding rural residential wells in the area are more than 3/4 of a mile away and are separated by Forsythe Creek to the west, and other small local drainages on the east and south as discussed in groundwater impact section #1 above. Forsythe Creek is at the same approximate elevation as the proposed maximum quarry pit bottom, so pit drawdown and interception of any groundwater flow moving towards the rural residential areas further to the west is not probable. The Maacama fault zone occurs to the east of the quarry, roughly paralleling Highway 101. The subdivided topography, diverse geologic units, and the presence of abundant landslides in this zone indicated that the rocks within it are highly sheared and shattered, while the occurrence of springs indicates that any east-west trending fractures zones in the underlying bedrock have been disrupted by fault movement and rock shearing, forcing local groundwater flow to the surface. There is little likelihood of groundwater in rock fracture zones to the east of Highway 101 moving west through the proposed quarrying area that would recharge groundwater further to the west of the quarry. Similarly the Maacama fault would likely block and disrupt any groundwater that would otherwise (prior to quarrying) travel east through rock fractures to recharge areas east of Highway 101. The biggest groundwater management concern in these areas is having more houses with individual wells and septic systems than the land and available water resources can support. Numerous residences on relatively small parcels create concerns regarding well interference effects between adjacent wells. This interference is much more potentially significant than the more distant project. It appears that the quarry will be located predominantly within a rock unit that is not pervasively fractured and sheared, and judging from the 500-foot deep dry test well, does not contain appreciable quantities of groundwater. It is therefore unlikely that the deepened quarry pit will intercept rock fracture flow moving or radiating outward from the quarry that does or could recharge neighboring springs and wells. It is more likely that the quarry will have a very slight beneficial effect on nearby deep wells and on springs and stream courses located down gradient due to the fact that runoff water from the future quarry hillside areas will be diverted in the future, with quarry expansion, into a retention basin on the quarry floor where it will be allowed to infiltrate into the rock fractures, and therefore recharge the local groundwater fracture zone aquifer. Mitigation Measures 3.2-D.1 The project applicant shall not withdraw water from wells or springs in a

manner that reduces flows to existing springs and wells in the area. Prior to expansion of the quarry in the vicinity of the suspected highly weathered rock fracture or shear zone on the site, monitoring of springs shall be performed over at least eight (8) quarters (2 years) to establish a baseline flow.

The spring monitoring should be completed by a registered geologist, certified engineering geologist, or hydro-geologist. Associated with the spring monitoring, the above professional should further examine and map the geology and rock structure in Questa’s conjectured fracture and shear zone to confirm its presence and relevance to spring flow, and further confirm that the quarry will not impact the springs and local wells within the zone. Rock fracture


patterns and local groundwater seeps and springs should also be observed and mapped in new quarry faces at the same time as spring flow monitoring.

During and following the expansion and reclamation of the quarry, spring flow

monitoring of the three springs along Black Bart Road (as shown on Figure 3.2-2) shall be performed quarterly and the data analyzed on an annual basis for a statistically significant deviation from the baseline flow. The analysis shall include a consideration of rainfall in establishing baseline spring flow. Following completion of the expansion and reclamation of the quarry, spring flow shall be monitored quarterly for five years, and the data analyzed on an annual basis for a statistically significant negative deviation from the baseline flow.

Allowing for rainfall variation, if it is determined that the spring flow has had a

statistically significant negative deviation from the baseline condition at any time during the expansion of the quarry, or within five years following the completion of the expansion and reclamation, the applicant shall be financially responsible for providing a reliable supply of water to the impacted beneficial water users who had an on-site well or spring in 2007. This could be done by providing a storage tank and delivered water to the affected homesite

3.2-D.2 Reduce project water consumption to the degree feasible by implementing

‘best management practices’ such as use of concrete admixtures and utilizing wastewater and detention pond water recycling to reduce the amount of water required.

Some admixtures can reduce water content used in concrete by 30%.

Recycling of aggregate wash water and use of water stored in sedimentation ponds can be used to reduce groundwater use, provided the water meets ASTM requirements77.

Impact Significance After Mitigation The above-noted measures would ensure that the impacts to groundwater resources would be reduced to a less than significant level. 3. Cumulative Impacts Water Quality Impact 3.2-E The project in combination with the other projects would

generate sediments and other pollutants that could potentially violate water quality standards and/or impact habitat.

There are no other proposed projects in the immediate project area or the watershed of Forsythe Creek. The only cumulative biological impacts that the project might contribute

77 ASTM 1602 C, 2004.


to would be water quality impacts on Forsythe Creek from the proposed project, any future incidental residential development in that watershed, and timber harvesting in that watershed. The Church of the Golden Rule has an approved Nonindustrial Timber Management Plan (NTMP) for their property which allows the Church to cut a sustained harvest of timber off their property, which contains lands within the Forsythe Creek watershed, A review of the NTMP shows that this harvesting is not expected to have an adverse impact on water quality resources. The timber harvest on the property that includes the project site has been completed. The project combined with adjacent timber harvesting and possible future development in the Forsythe Creek watershed could adversely affect water quality of the stream, which would be a potentially significant cumulative impact. Mitigation Measures The mitigation measures recommended for Impact 3.2-A apply to this impact. Impact Significance After Mitigation Project compliance with required mitigations will ensure that the project does not adversely affect water quality in Forsythe Creek or the Russian River. It is assumed that future timber harvests on Ridgewood Ranch would comply with all water quality protections included in the adopted NTMP. The cumulative impact would therefore be reduced to a less than significant level.

3.2 hydrology and water quality - mendocino county, ca4. project area surface water hydrology...

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