Appendix G Water Quality Assessments

Transcription

1 Appendix G Water Quality Assessments

2 Water Quality Assessment for Regulus Solar Project

3 Prepared For: FRV Regulus Solar, LP Prepared By: Alton Parkway Irvine, CA JN

4 Regulus Solar Project Water Quality Assessment A qualitative assessment of the project was performed to assess water quality pre- and postdevelopment conditions based on the region s applicable stormwater regulations according to the National Pollutant Discharge Elimination System (NPDES) permit requirements. The assessment was performed to characterize the baseline water quality conditions and identify potential project water quality issues, and applicable mitigation measures (best management practices or BMPs). The assessment covers the following: a. A description of the approach to the water quality assessment and evaluation of the potential impacts related to project implementation. b. Identification of the regional hydrology, local hydrology, floodplains, groundwater resources, topography, climate, soils/erosion potential, and existing water quality. c. Identification of the applicable requirements of the federal Clean Water Act (CWA), state water quality regulations (California Statewide Construction General Permit or CGP), state requirements under Section 402 of the federal CWA, beneficial uses, groundwater and surface water quality objectives, and a listing of impaired waters. d. A description of the project s water quality risk assessment that was performed for the project according to the CGP (Order DWQ) to determine project risk levels. e. Identification of potential stormwater quality mitigation measures (BMPs) that may be needed based on the water quality requirements applicable to the project. This includes a qualitative BMP type selection, conceptual preliminary sizing (if treatment BMPs are applicable), and cost estimate. The Regulus Solar Project (project site) consists of 13 parcels of approximately acres of vacant agricultural land, and the parcels are identified as follows: Assessor s Parcel Number Acreage Township Range Section S 29 E S 29 E S 29 E S 29 E S 29 E S 29 E S 29 E S 29 E S 29 E S 29 E S 29 E S 29 E S 29 E 27 The project is located approximately 10 miles east of the City of Bakersfield and four miles northeast of Lamont, at the intersection of East Panama Lane and Malaga Road, in unincorporated Kern County, California (refer to Figure A-1, Vicinity Map in the Appendix). Site elevation ranges from 500 feet above mean sea level (msl) at the southwest corner to 610 feet above msl at the northeast corner, and slopes gently upward from southwest to northeast. There are no existing structures located within the areas proposed for solar development, except for 1

5 Regulus Solar Project Water Quality Assessment one vacant house in the northeast corner of APN The project site consists primarily of agricultural fields, and portions of the site are under Williamson Act land use contracts. In addition, aboveground transmission lines, oil development infrastructure, oil wells and water detention basins (associated with farming activities) are present on-site. Site access will be provided from East Panama Lane, Comanche Drive, Hermosa Road, and Malaga Road. The area surrounding the project site consists largely of rural agricultural land. The Regulus Solar Project was designed with an emphasis on protecting the project site and downstream facilities from flood hazards and water quality impairments. This proactive approach to mitigate for runoff flow rates and volumes will be necessary to address the requirements to preserve the existing drainage patterns, flood hazard potential, and stormwater quality. Therefore, designing this project site addressed these requirements by considering the following mitigation measures: Mitigate increases in runoff volumes and rates because of the project site for the 85 th percentile storm using BMPs, which provide infiltration or retention (either above ground or underground). Provide soil erosion control and soil stabilization during the construction phase by implementing temporary construction BMPs and by implementing a Storm Water Pollution Prevention Plan (SWPPP). Implement structures or improvements (if necessary) to ensure flood hazard protection for the project site, solar structures, and downstream flow conveyance and properties. In general, this approach will ensure protection using the 100-year flood event to maintain existing flood patterns, flow depths, and flow velocities throughout the project site and downstream. The project site is located in the Arvin-Wheeler Ridge Subbasin, part of the valley floor waters of the Tulare Lake Basin within the Central Valley Region of California. It is located 10 miles east of SR-99 and 11 miles southeast of the City of Bakersfield in Kern County, California. The region is bordered by the San Emigdio and Tehachapi Mountains to the south and the Tejon Hills to the east. The project site is located in an area that is primarily agricultural. A desktop survey of the region was performed using topographic maps and aerial images to identify the receiving water body. No receiving surface water bodies for runoff from the project site were identified during the desktop survey. The Water Quality Control Plan for the Tulare Lake Basin, Second Edition (Basin Plan) states that normally direct precipitation percolates into valley groundwater if not lost through consumptive use, evaporation, or evapotranspiration. According to U.S. Geological Survey (USGS) topography data, the project site drains from northeast to southwest toward the Arvin Edison Canal with a slope of approximately 1.2 percent. The relatively flat project site area has elevations varying between approximately 500 feet above mean sea level on the southwestern boundary and 610 feet above mean sea level on the northeastern boundary. Rainfall on the valley portion of the basin averages less than 10 inches per year (Basin Plan, 1995). The rainfall erosivity factor (R factor) for the area is estimated to be This factor represents the total storm kinetic energy times the maximum 30-minute intensity and is directly proportional to the soil loss, when factors other than rainfall are held constant. The R factor was 2

6 Regulus Solar Project Water Quality Assessment estimated using the United States Environmental Protection Agency (U.S. EPA) Rainfall Erosivity Factor Calculator ( The U.S. EPA defines a watershed as the area of land where all of the water that is under it or drains off of it goes into the same place ( The project site is located within the Arvin-Wheeler Ridge Subbasin. The desktop survey and Basin Plan suggest that drainage from the project site is likely lost through consumptive use, evapotranspiration, or evaporation or percolates into groundwater before reaching a surface water body. This project site is located in an area designated as Zone X. This designation corresponds to areas of 0.2% annual chance flood, and areas of one percent annual chance sheet flow flooding where average depths are less than one foot, areas of one percent annual chance stream flooding where the contributing drainage area is less than one square mile, or areas protected by levees from the one percent annual chance flood. No base flood elevations or depths are shown within this zone. The project site is located within the Kern County Groundwater Basin. The basin comprises 1,950,000 acres. Overdraft of groundwater for municipal, agricultural and industrial purposes has in part led to the paramount water quality problem in the basin: accumulation of salts. The primary constituents of concern in the Tulare Basin are high total dissolved solids, nitrate, arsenic, and organic compounds (California Department of Water Resources, 2004). A monitoring station near the project site was monitored between 1980 and 2000, and its data indicates that the depth to groundwater is approximately 351 feet ( The Soil Erodibility Factor (K factor) for the project site is 0.30, according to the Natural Resources Conservation Service (NRCS) soil survey data. Generally, this equates to a low potential for erosion within the project site area characterized by particles resistant to detachment. However, this is a planning-level tool, so a detailed project site-specific survey is still required for design-level analysis. The K factor represents: Susceptibility of soil or surface material to erosion Transportability of the sediment The amount and rate of runoff given a particular rainfall input, as measured under a standard condition. The Clean Water Act, as amended by the Water Quality Act of 1987, is the major federal legislation governing water quality, which was enacted to restore and maintain the chemical, physical, and biological integrity of the nation s waters. This project site drains to a water body that is designated as a federal water of the United States, however the permits associated with the Clean Water Act are not applicable to this project site. The State of California s Porter- Cologne Act requirements also apply to this project site. 3

7 Regulus Solar Project Water Quality Assessment The Porter-Cologne Act established the State Board and the nine Regional Boards, and authorized the State Board to formulate, adopt, and revise state water policy, which may include water quality objectives, principles, and guidelines. In addition, it authorizes the State Board to adopt water quality control plans on its own initiative, which supersede regional Water Quality Control Plans to the extent of any conflict. Article 3 of the Porter-Cologne Act directs Regional Boards to adopt, review, and revise Basin Plans, and provides specific guidance on factors, which must be considered when adopting water quality objectives and implementation measures. It also allows Regional Boards to prohibit discharges in Basin Plans or in waste discharge requirements. The Central Valley Regional Water Quality Control Board (RWQCB) is responsible for the protection of beneficial uses of water resources within the Central Valley Region and uses planning, permitting, and enforcement authorities to meet this responsibility. Every water body within the jurisdiction of the RWQCB is designated a set of beneficial uses that are protected by appropriate water quality objectives and identified in the Basin Plan. The beneficial uses for minor surface waters in the Undefined Hydrologic Sub-Area (HSA ) of the Arvin-Weeler Ridge Hydrologic Area and the Kern County Groundwater Basin (DAU 254 & 258) include the following: Municipal and Domestic Supply (MUN) Agricultural Supply (AGR) Industrial Service Supply (IND) Industrial Process Supply (PRO) Hydropower Generation (POW) Water Contact Recreation (REC-1) Non-Contact Water Recreation (REC-2) Warm Freshwater Habitat (WARM) Wildlife Habitat (WILD) Rare, Threatened, or Endangered Species (RARE) Ground Water Recharge (GWR) However, no receiving surface water body was identified during the desktop survey performed for this project site. For a detailed description of how the RWQCB defines the beneficial uses, see the Appendix. Section 303 of the CWA requires that the state adopt water quality objectives for surface waters. The Basin Plan contains water quality objectives that are considered necessary to protect the specific beneficial uses it identifies (as identified in Section 5.2). Section 303(d) of the CWA specifically requires the state to develop a list of impaired water bodies and Total Maximum Daily Loads (TMDLs) plans to determine the maximum allowable pollutant load that a water body can receive and continue to meet the designated beneficial uses. Since the project site does not drain to a surface water body identified within the Basin Plan, impaired receiving surface water bodies and TMDLs will not need to be addressed by the project site. 4

8 Regulus Solar Project Water Quality Assessment NPDES Municipal Permit Requirements The project site is not located in an area that drains to a permitted municipal separate storm sewer system (MS4) and therefore is not subject to an NPDES municipal permit. Construction General Permit The project site is subject to the requirements of the General Permit for Storm Water Discharges Associated with Construction and Land Disturbance Activities (CGP, Order DWQ) permit. It requires that any construction project disturbing more than one acre of land obtain coverage, for any size parcel that is part of a larger common plan of development, or for any project that the RWQCB requires coverage. The CGP generally requires: 1. Assessment of the Project Risk (Risks 1, 2, 3, from low risk to high risk) 2. Enrollment under the Permit through the State Water Resources Control Board (SWRCB) 3. Development and implementation of a Storm Water Pollution Prevention Plan (SWPPP) 4. Sampling of stormwater and potential sampling of receiving water (depending on project risk) 5. Reporting requirements As required by the CGP, the project risks were evaluated based on project location, sediment discharge risks, and receiving waters risk. The results from this analysis are included in the Appendix and summarized below. Receiving water: None identified Construction duration: October 1, 2012 to December 1, 2013 Sediment Risk Analysis R-factor = K-factor = 0.30 LS-factor = 1.02 Sediment Yield = 3.66 tons/acre Sediment Risk Factor: Receiving Water Risk Analysis On 303(d) List for Sediment = No All Beneficial Use Impact (COLD, SPAWN, MIGR) = No Receiving Water Risk: LOW The risk assessment conducted per the data above indicates that the project site is Risk Level 1. Runoff Reduction Requirements The project is required to comply with the runoff reduction and post-construction standards according to the CGP, since the project is not within a Phase I or Phase II permit area. The project will be required to replicate the pre-project water balance (defined as the volume of rainfall that ends up as runoff) for the smallest storms up to the 85th percentile storm event (or the smallest storm event that generates runoff, whichever is larger). The volume that cannot be addressed using nonstructural practices will be captured in structural practices and approved by the RWQCB. 5

9 Regulus Solar Project Water Quality Assessment The CGP requires projects that disturb an area exceeding two acres must do the following: Preserve the pre-construction drainage density (miles of stream length per square mile of drainage area) for all drainage areas within the project serving a first order stream or larger stream; and, Ensure that the post-development time of concentration is equal to or greater than predevelopment time of concentration. A first order stream is defined as a stream with no tributaries. No first order streams were located during the planning evaluation; however, confirmation will need to be conducted in later phases of developing the project site. The project site will result in an increase in runoff volume due to compaction of soils during construction. A hydrologic analysis was prepared to compare the expected runoff flows and volumes of pre-development with the runoff flows and volumes of post-development for the 85 th percentile storm rainfall of 0.34 inches. The Basin Sizer program was used to determine the size of the 85 th percentile storm rainfall, and the output is included in the Appendix. The project site was first analyzed for the 85 th percentile storm event to determine if runoff would occur. Since the 85 th percentile storm event did not produce runoff, the next largest storm event, the 2-year (50% annual chance) storm event, was analyzed. The 2-year storm event generated runoff in the project site s pre-development and post-development conditions. The project s postdevelopment conditions are expected to generate 194 cubic yards of runoff. Table 1 presents the results of the analysis. Table 1: Peak Flow and Volume Increase from a 2-Year Storm Event Condition 2-Year Peak Flow (cubic feet per second) Cross Section 1 (XS-1) 6 2-Year Volume (acre-feet) Pre-Development Post-Development Difference between Post- Development and Pre Development Cross Section 2 (XS-2) Pre-Development Post-Development Difference between Post- Development and Pre Development Cross Section 3 (XS-3) Pre-Development Post-Development Difference between Post- Development and Pre Development Cross Section 4 (XS-4) Pre-Development Post-Development Difference between Post- Development and Pre- Development

10 Regulus Solar Project Water Quality Assessment Condition 2-Year Peak Flow (cubic feet per second) Cross Section 5 (XS-5) 2-Year Volume (acre-feet) Pre-Development Post-Development Difference between Post- Development and Pre Development Cross Section 6 (XS-6) Pre-Development Post-Development Difference between Post- Development and Pre- Development Project Site Area = 743 Acres 85th percentile rainfall = 0.34 inches Figures 1 and 2 show the flow patterns in the pre-development and post-development conditions, and identify the locations of the cross sections. Figures 3 through 8 show the relationship between the affect of the peak flow resulting from post-development project site conditions at the locations of the six cross sections that were analyzed. Baseline Conditions represents the pre-development condition, Project Conditions is the post-development condition, and Project-related changes is the change as a result of the post-development condition. 7

11 Regulus Solar Project Water Quality Assessment Figure 1: Local Map of Maximum Flood Depths Baseline Conditions 50-Percent Annual Chance Storm Event 8

12 Regulus Solar Project Water Quality Assessment Figure 2: Local Map of Maximum Flood Depths Project Conditions 50-Percent Annual Chance Storm Event 9

13 Regulus Solar Project Water Quality Assessment Figure 3: 50-Percent Annual Chance 24-Hour Peak Flow Distribution Along XS-1 Figure 4: 50-Percent Annual Chance 24-Hour Peak Flow Distribution Along XS-2 10

14 Regulus Solar Project Water Quality Assessment Figure 5: 50-Percent Annual Chance 24-Hour Peak Flow Distribution Along XS-3 Figure 6: 50-Percent Annual Chance 24-Hour Peak Flow Distribution Along XS-4 11

15 Regulus Solar Project Water Quality Assessment Figure 7: 50-Percent Annual Chance 24-Hour Peak Flow Distribution Along XS-5 Figure 8: 50-Percent Annual Chance 24-Hour Peak Flow Distribution Along XS-6 Based on the analysis, post-development runoff volumes for the 2-year storm event are expected to generate runoff due to soil conditions in the area. 12

16 Regulus Solar Project Water Quality Assessment Per the water quality requirements, development projects must consider opportunities to reduce runoff and prevent impacts to downstream receiving waters. To meet the CGP requirements, the project site design should incorporate structural post-construction BMPs such as the following to meet the intent of these requirements: Using a portion of the project site area as a retention basin (with panels, not a dedicated basin) Constructing a dedicated infiltration/retention basin Constructing infiltration trenches Extended detention basins (where infiltration is technically infeasible) The BMPs were sized using available soil data, assuming the entire 743-acre project would be developed, and to address the greatest change in runoff volume produced by the 2-year storm event when comparing the pre-development conditions to post-development conditions. The proposed BMPs should be considered when the project site s plan is prepared. The table below summarizes the results of the analysis. 85 th Percentile Storm Event Volume (Post-development - Pre-development): Volume = 0.3 Cubic Yards per Acre Mitigation Measure Cost Estimate (Assuming Mitigation for Runoff Volume for up to a 2- year Event) Mitigation Measure Type Area (ac) Volume Runoff (cf) Width (ft) Length (ft) Depth (ft) Infiltration Basin (IB) 743 5, $6,700 Infiltration Trench (IT) 743 5, $18,000 Shallow IB 743 5, $5,700 Shallow IB $100 IB = Infiltration Basin IT = Infiltration Trench Shallow IB = Shallow Infiltration Area (no more than 6 inches in depth) Cost Project Site Management BMPs Non-stormwater BMPs (control of non-stormwater discharges) Erosion Control BMPs o Implement wind erosion controls o Provide effective soil cover for inactive areas o o Limit use of plastic materials Ensure soil loss during each phase is equivalent or less than pre-construction soil loss 13

17 Regulus Solar Project Water Quality Assessment Sediment Control BMPs o Establish effective perimeter controls o Stabilize construction entrances/exits o Comply with sediment basin guidelines o Implement appropriate erosion control in conjunction with sediment control o Establish linear slope controls o Establish access road controls The table below summarizes the regulatory requirements that must be met to develop this project. Regulatory Requirements/ Development Impacts Porter-Cologne Act Construction General Permit Temporary Construction BMPs Post-Development Mitigation to Address Regulatory Requirements/Development Impacts Design and implement the project site per the requirements of the Basin Plan. Adhere to the Basin Plan s water quality objectives, discharge prohibitions, and water quality standards. Develop and implement a SWPPP that meets the requirements of the CGP. Temporary BMPs such as desilting basins, erosion control blankets, and other minimum construction BMPs will be implemented as stated in the SWPPP developed for the project site. Implement post-construction BMPs. Design the project to minimize hydromodification impacts, such as flow direction and flow volume mitigated by BMPs. All Central Valley RWQCB discharge requirements and the County of Kern s water quality regulations will be adhered to in the development and maintenance of this project. 14

18 Regulus Solar Project Water Quality Assessment California Department of Water Resources, California s Groundwater, Bulletin 118, updated 2006 ( accessed on September 13, 2011 California Department of Water Resources, Water Data Library, (Well 32S28E34R001M) accessed on September 13, California Regional Water Quality Control Board, Central Valley Region, Water Quality Control Plan for the Tulare Lake Basin, second Edition, Revised January Federal Emergency Management Agency (FEMA) Map Service Center, Flood Maps. accessed September 13, State Water Resources Control Board, National Pollutant Discharge Elimination System (NPDES) General Permit for Storm Water Discharges Associated with Construction and Land Disturbance Activities (Order Number DWQ, NPDES Number CAS000002), September 5, United States Department of Agriculture, Natural Resources Conservation Service, Web Soil Survey data, accessed September 13, 2011 via their website: Western Regional Climate Center, a partnership between the National Climatic Data Center, National Weather Service, the American Association of State Climatologists, and NOAA Research Institute, Monthly Climate Summary for Bakersfield, California, accessed September 13, 2011 via their website: 15

19 Appendix Regulus Solar Project Water Quality Assessment

20 South Fairfax Road Edison Road Comanche Drive Comanche Drive Tower Line Road }þ178 }þ184 Oswell Street Fairfax Road Edison Highway Bena Road }þ58 East Panama Lane }þ184 General Beale Road East Panama Lane M:\Mdata\ \GIS\Regulus_VicinityMap.mxd Buena Vista Boulevard Legend Project Boundary Highway Major Road Edison Road East Bear Mountain Boulevard 0 REGULUS SOLAR PROJECT WATER QUALITY ASSESSMENT 1 2 Miles Source: NAIP - National Agriculture Imagery Program, and StreetMap USA Vicinity Map Figure A-1

21 Regulus Solar Project Water Quality Assessment Description of Beneficial Uses Designations The following are descriptions of the beneficial uses identified in Section 5.2 of this report. Municipal and Domestic Supply (MUN) Uses of water for community, military, or individual water supply systems, including, but not limited to, drinking water supply. Agricultural Supply (AGR) Uses of water for farming, horticulture, or ranching, including, but not limited to, irrigation, stock watering, or support of vegetation for range grazing. Industrial Service Supply (IND) Uses of water for industrial activities that do not depend primarily on water quality, including, but not limited to, mining, cooling water supply, hydraulic conveyance, gravel washing, fire protection, or oil well repressurization. Industrial Process Supply (PRO) Uses of water for industrial activities that depend primarily on water quality. Hydropower Generation (POW) Uses of water for hydropower generation. Water Contact Recreation (REC-1) Uses of water for recreational activities involving body contact with water, where ingestion of water is reasonably possible. These uses include, but are not limited to, swimming, wading, water-skiing, skin and scuba diving, surfing, white water activities, fishing, or use of natural hot springs. Non-Contact Water Recreation (REC-2) Uses of water for recreational activities involving proximity to water but where there is generally no body contact with water, nor any likelihood of ingestion of water. These uses include, but are not limited to, picnicking, sunbathing, hiking, beachcombing, camping, boating, tidepool and marine life study, hunting, sightseeing, or aesthetic enjoyment in conjunction with the above activities. Warm Freshwater Habitat (WARM) Uses of water that support warm water ecosystems, including, but not limited to, preservation or enhancement of aquatic habitats, vegetation, fish, or wildlife, including invertebrates. WARM includes support for reproduction and early development of warm water fish. Wildlife Habitat (WILD) Uses of water that support terrestrial or wetland ecosystems, including but not limited to, preservation and enhancement of terrestrial habitats or wetlands, vegetation, wildlife (e.g., mammals, birds, reptiles, amphibians, invertebrates), or wildlife water and food sources. Rare, Threatened, or Endangered Species (RARE) Uses of water that support habitats necessary, at least in part, for the survival and successful maintenance of plant or animal species established under state or federal law as rare, threatened or endangered. Ground Water Recharge (GWR) Uses of water for natural or artificial recharge of ground water for purposes of future extraction, maintenance of water quality, or halting of saltwater intrusion into freshwater aquifers.

22 Version 6/10/2009 Construction General Permit - Risk Determination Worksheet Step 1 Step 2 Step 3 Determine Sediment Risk via one of the options listed: 1. GIS Map Method - EPA Rainfall Erosivity Calculator & GIS map 2. Individual Method - EPA Rainfall Erosivity Calculator & Individual Data Determine Receiving Water Risk via one of the options listed: 1. GIS map of Sediment Sensitive Watersheds provided (in development) 2. List of Sediment Sensitive Watersheds provided Determine Combined Risk Level

23 Sediment Risk Factor Worksheet Entry A) R Factor Analyses of data indicated that when factors other than rainfall are held constant, soil loss is directly proportional to a rainfall factor composed of total storm kinetic energy (E) times the maximum 30-min intensity (I30) (Wischmeier and Smith, 1958). The numerical value of R is the average annual sum of EI30 for storm events during a rainfall record of at least 22 years. "Isoerodent" maps were developed based on R values calculated for more than 1000 locations in the Western U.S. Refer to the link below to determine the R factor for the project site. R Factor Value B) K Factor (weighted average, by area, for all site soils) The soil-erodibility factor K represents: (1) susceptibility of soil or surface material to erosion, (2) transportability of the sediment, and (3) the amount and rate of runoff given a particular rainfall input, as measured under a standard condition. Fine-textured soils that are high in clay have low K values (about 0.05 to 0.15) because the particles are resistant to detachment. Coarse-textured soils, such as sandy soils, also have low K values (about 0.05 to 0.2) because of high infiltration resulting in low runoff even though these particles are easily detached. Medium-textured soils, such as a silt loam, have moderate K values (about 0.25 to 0.45) because they are moderately susceptible to particle detachment and they produce runoff at moderate rates. Soils having a high silt content are especially susceptible to erosion and have high K values, which can exceed 0.45 and can be as large as Silt-size particles are easily detached and tend to crust, producing high rates and large volumes of runoff. Use Site-specific data must be submitted. Site-specific K factor guidance K Factor Value C) LS Factor (weighted average, by area, for all slopes) The effect of topography on erosion is accounted for by the LS factor, which combines the effects of a hillslope-length factor, L, and a hillslope-gradient factor, S. Generally speaking, as hillslope length and/or hillslope gradient increase, soil loss increases. As hillslope length increases, total soil loss and soil loss per unit area increase due to the progressive accumulation of runoff in the downslope direction. As the hillslope gradient increases, the velocity and erosivity of runoff increases. Use the LS table located in separate tab of this spreadsheet to determine LS factors. Estimate the weighted LS for the site prior to construction. LS Table LS Factor Value Watershed Erosion Estimate (=RxKxLS) in tons/acre Site Sediment Risk Factor Low Sediment Risk: < 15 tons/acre Medium Sediment Risk: >=15 and <75 tons/acre High Sediment Risk: >= 75 tons/acre Low

24 Receiving Water (RW) Risk Factor Worksheet Entry Score A. Watershed Characteristics yes/no A.1. Does the disturbed area discharge (either directly or indirectly) to a 303(d)-listed waterbody impaired by sediment? For help with impaired waterbodies please check the attached worksheet or visit the link below: 2006 Approved Sediment-impared WBs Worksheet OR A.2. Does the disturbed area discharge to a waterbody with designated beneficial uses of SPAWN & COLD & MIGRATORY? No Low

25 Combined Risk Level Matrix Receiving Water Risk Low Level 1 Sediment Risk Low Medium High Level 2 High Level 2 Level 3 Project Sediment Risk: Low 1 Project RW Risk: Low 1 Project Combined Risk: Level 1

26

27 Water Quality Assessment for Adobe Solar Project

28 Prepared For: FRV Adobe Solar, LP Prepared By: Alton Parkway Irvine, CA JN

29 Adobe Solar Project Water Quality Assessment A qualitative assessment of the project was performed to assess water quality pre- and postdevelopment conditions based on the region s applicable stormwater regulations according to the National Pollutant Discharge Elimination System (NPDES) permit requirements. The assessment was performed to characterize the baseline water quality conditions and identify potential project water quality issues, and applicable mitigation measures (best management practices or BMPs). The assessment covers the following: a. A description of the approach to the water quality assessment and evaluation of the potential impacts related to project implementation. b. Identification of the regional hydrology, local hydrology, floodplains, groundwater resources, topography, climate, soils/erosion potential, and existing water quality. c. Identification of the applicable requirements of the federal Clean Water Act (CWA), state water quality regulations (California Statewide Construction General Permit or CGP), state requirements under Section 402 of the federal CWA, beneficial uses, groundwater and surface water quality objectives, and a listing of impaired waters. d. A description of the project water quality risk assessment that was performed for the project site according to the CGP (Order DWQ) to determine project risk levels. e. Identification of potential stormwater quality mitigation measures (BMPs) that may be needed based on the water quality requirements applicable to the project. This includes a qualitative BMP type selection, conceptual preliminary sizing (if treatment BMPs are applicable), and cost estimate. Since the Adobe Solar Project (project site) is adjacent to the Rigel Solar Project, two postdevelopment scenarios were evaluated to determine the impacts of developing the project site only, or developing both the Adobe Solar Project and the Rigel Solar Project. The project site is located approximately 9.5 miles southwest of the town of Arvin and approximately 1.5 miles east of SR-99, near the intersection of Adobe Road and Crider Road, in unincorporated Kern County, California. The project site consists of four parcels, containing approximately 160 acres of vacant land. Parcel 1 consists of approximately 60 acres and is located in the northeast quarter section of the northeast of Section 34, Township 32 South, Range 28 East, Mount Diablo Meridian. Parcel 2 and 3 each consist of approximately 10 acres respectively and are located west of Parcel 1, in the northwestern quarter section and northeast quarter of the southwest quarter of Section 34, Township 32 South, Range 28 East, Mount Diablo Meridian. Parcel 4 is approximately 80 acres and is just south of Parcels 1, 2, and 3. Parcel 4 is located in the southwest and southeast quarter of the northeast quarter of Section 34, Township 32 South, Range 28 East, Mount Diablo Meridian. The Assessor s Parcel Numbers (APNs) for the four parcels are , , , and Site elevation varies between approximately 400 and 445 feet above mean sea level, and slopes gradually downward to the north-northwest. The project site has historically been used for agricultural production, and the land is under a Williamson Act land use contract. There are no existing structures located on-site. Site access will be provided from Crider Road, and an additional access via David Road is currently being considered. The establishment of additional site access is being considered from the south via David Road (refer to Figure A-1, Vicinity Map in the Appendix). 1

30 Adobe Solar Project Water Quality Assessment The area surrounding the project site is primarily agricultural land. David Road is located south of the project site, and an agricultural processing facility is located approximately one mile east of the project site. The Adobe Solar Project site was designed with an emphasis on protecting the project site and downstream facilities from flood hazards and water quality impairments. This proactive approach to mitigate for runoff flow rates and volumes will be necessary to address the requirements to preserve the existing drainage patterns, flood hazard potential, and stormwater quality. Therefore, designing this project site addressed these requirements by considering the following mitigation measures: Mitigate increases in runoff volumes and rates because of the project site for the 85 th percentile storm using BMPs, which provide infiltration or retention (either above ground or underground). Provide soil erosion control and soil stabilization during the construction phase by implementing temporary construction BMPs and by implementing a Storm Water Pollution Prevention Plan (SWPPP). Implement structures or improvements (if necessary) to ensure flood hazard protection for the project site, solar structures, and downstream flow conveyance and properties. In general, this approach will ensure protection using the 100-year flood event to maintain existing flood patterns, flow depths, and flow velocities throughout the project site and downstream. The project site is located in the Arvin-Wheeler Ridge Subbasin, part of the valley floor waters of the Tulare Lake Basin within the Central Valley Region of California. It is located 1.5 miles east of SR-99 and 11 miles south of the City of Bakersfield in Kern County, CA. The region is bordered by the San Emigdio and Tehachapi Mountains to the south and the Tejon Hills to the east. The project site is located in an area that is primarily agricultural. A desktop survey of the region was performed using topographic maps and aerial images to identify the receiving water body. No receiving surface water bodies for runoff from the project site were identified from the desktop survey. The Water Quality Control Plan for the Tulare Lake Basin, Second Edition (Basin Plan) states that normally direct precipitation percolates into valley groundwater if not lost through consumptive use, evaporation, or evapotranspiration. According to the U.S. Geological Survey (USGS) topography data, the project site drains from southeast to northwest towards the New Rim Ditch with a slope length of approximately 0.7 percent. The relatively flat project site area has elevations varying between approximately 420 feet above mean sea level on the southeastern boundary and 400 feet above mean sea level on the northwestern boundary. Rainfall on the valley portion of the basin averages less than 10 inches per year (Basin Plan, 1995). The rainfall erosivity factor (R factor) for the area is estimated to be This factor represents the total storm kinetic energy times the maximum 30-minute intensity and is directly proportional to the soil loss, when factors other than rainfall are held constant. The R factor was estimated using the United States Environmental Protection Agency (U.S. EPA) Rainfall Erosivity Factor Calculator ( 2

31 Adobe Solar Project Water Quality Assessment The U.S. EPA defines a watershed as the area of land where all of the water that is under it or drains off of it goes into the same place ( The project site is located within the Arvin-Wheeler Ridge Subbasin. The desktop survey and Basin Plan suggest that drainage from the project site is likely lost through consumptive use, evapotranspiration, or evaporation or percolates into groundwater before reaching a surface water body. The project site is located in an area designated as Zone X. This designation corresponds to areas of 0.2% annual chance flood, and areas of one percent annual chance sheet flow flooding where average depths are less than one foot, areas of one percent annual chance stream flooding where the contributing drainage area is less than one square mile, or areas protected by levees from the one percent annual chance flood. No base flood elevations or depths are shown within this zone. The project site is located within the Kern County Groundwater Basin. The basin comprises 1,950,000 acres. Overdraft of groundwater for municipal, agricultural and industrial purposes has in part led to the accumulation of salts in the basin s groundwater resources. The primary constituents of concern in the Tulare Basin are high total dissolved solids, nitrate, arsenic, and organic compounds (California Department of Water Resources, 2004). A monitoring station located near the project site was monitored between 1980 and 2000, and its data indicates that the depth to groundwater is approximately 306 feet ( The Soil Erodibility Factor (K factor) for the project site is 0.23, according to the Natural Resources Conservation Service (NRCS) soil survey data. Generally, this equates to a low potential for erosion within the project site area characterized by particles resistant to detachment. However, this is a planning-level tool, so a detailed project site-specific survey is still required for design-level analysis. The K factor represents: Susceptibility of soil or surface material to erosion Transportability of the sediment The amount and rate of runoff given a particular rainfall input, as measured under a standard condition. The Clean Water Act, as amended by the Water Quality Act of 1987, is the major federal legislation governing water quality, which was enacted to restore and maintain the chemical, physical, and biological integrity of the nation s waters. This project site drains to a water body that is designated as a federal water of the United States, however the permits associated with the Clean Water Act are not applicable to this project site. The State of California s Porter- Cologne Act requirements also apply to this project site. The Porter-Cologne Act established the State Board and the nine Regional Boards, and authorized the State Board to formulate, adopt, and revise state water policy, which may include water quality objectives, principles, and guidelines. In addition, it authorizes the State Board to 3

32 Adobe Solar Project Water Quality Assessment adopt water quality control plans on its own initiative, which supersede Regional Water Quality Control Plans to the extent of any conflict. Article 3 of the Porter-Cologne Act directs Regional Boards to adopt, review, and revise Basin Plans, and provides specific guidance on factors, which must be considered when adopting water quality objectives and implementation measures. It also allows Regional Boards to prohibit discharges in Basin Plans or in waste discharge requirements. The Central Valley Regional Water Quality Control Board (RWQCB) is responsible for the protection of beneficial uses of water resources within the Central Valley Region and uses planning, permitting, and enforcement authorities to meet this responsibility. Every water body within the jurisdiction of the RWQCB is designated a set of beneficial uses that are protected by appropriate water quality objectives and identified in the Basin Plan. The beneficial uses for minor surface waters in the Undefined Hydrologic Sub-Area (HSA ) of the Arvin-Weeler Ridge Hydrologic Area and the Kern County Groundwater Basin (DAU 258) include the following: Municipal and Domestic Supply (MUN) Agricultural Supply (AGR) Industrial Service Supply (IND) Industrial Process Supply (PRO) Water Contact Recreation (REC-1) Non-Contact Water Recreation (REC-2) Warm Freshwater Habitat (WARM) Wildlife Habitat (WILD) Rare, Threatened, or Endangered Species (RARE) Ground Water Recharge (GWR) However, no receiving surface water body was identified during the desktop survey performed for this project site. For a detailed description of how the RWQCB defines the beneficial uses, see the Appendix. Section 303 of the CWA requires that the state adopt water quality objectives for surface waters. The Basin Plan contains water quality objectives that are considered necessary to protect the specific beneficial uses it identifies (as identified in Section 5.2). Section 303(d) of the CWA specifically requires the state to develop a list of impaired water bodies and Total Maximum Daily Loads (TMDLs) plans to determine the maximum allowable pollutant load that a water body can receive and continue to meet the designated beneficial uses. Since the project site does not drain to a surface water body identified within the Basin Plan, impaired receiving surface water bodies and TMDLs will not need to be addressed by the project site. NPDES Municipal Permit Requirements The project site is not located in an area that drains to a permitted municipal separate storm sewer system (MS4) and therefore is not subject to an NPDES municipal permit. Construction General Permit The project site is subject to the requirements of the General Permit for Storm Water Discharges Associated with Construction and Land Disturbance Activities (CGP, Order

33 Adobe Solar Project Water Quality Assessment 009-DWQ) permit. It requires that any construction project disturbing more than one acre of land obtain coverage, for any size parcel that is part of a larger common plan of development, or for any project site that the RWQCB requires coverage. The CGP generally requires: 1. Assessment of the Project Risk (Risks 1, 2, 3, from low risk to high risk) 2. Enrollment under the Permit through the State Water Resources Control Board (SWRCB) 3. Development and implementation of a Storm Water Pollution Prevention Plan (SWPPP) 4. Sampling of stormwater and potential sampling of receiving water (depending on project risk) 5. Reporting requirements As required by the CGP, the project site risks were evaluated based on project location, sediment discharge risks, and receiving waters risk. The results from this analysis are included in the Appendix and summarized below. Receiving water: None identified Construction duration: September 2012 to September 2013 Sediment Risk Analysis R-factor = K-factor = 0.23 LS-factor = 0.89 Sediment Yield = 2.90 tons/acre Sediment Risk Factor: Receiving Water Risk Analysis On 303(d) List for Sediment = No All Beneficial Use Impact (COLD, SPAWN, MIGR) = No Receiving Water Risk: LOW The risk assessment conducted per the data above indicates that the project site is Risk Level 1. Runoff Reduction Requirements The project site is required to comply with the runoff reduction and post-construction standards according to the CGP, since the project site is not within a Phase I or Phase II permit area. The project site will be required to replicate the pre-project water balance (defined as the volume of rainfall that ends up as runoff) for the smallest storms up to the 85th percentile storm event (or the smallest storm event that generates runoff, whichever is larger). The volume that cannot be addressed using nonstructural practices will be captured in structural practices and approved by the RWQCB. The CGP requires project sites that disturb an area exceeding two acres must do the following: Preserve the pre-construction drainage density (miles of stream length per square mile of drainage area) for all drainage areas within the project site serving a first order stream or larger stream; and, Ensure that the post-development time of concentration is equal to or greater than predevelopment time of concentration. A first order stream is defined as a stream with no tributaries. No first order streams were located during the planning evaluation; however, confirmation will need to be conducted during later phases of developing the project site. 5

34 Adobe Solar Project Water Quality Assessment The project site will result in an increase in runoff volume due to compaction of soils during construction. A hydrologic analysis was prepared to compare the expected runoff flows and volumes of pre-development with the runoff flows and volumes of two post-development scenarios, the development of the Adobe Solar Project only, and the development of the Adobe Solar Project and the Rigel Solar Project together, for the 85 th percentile storm rainfall of 0.36 inches. The Basin Sizer program was used to determine the size of the 85 th percentile storm rainfall, and the output is included in the Appendix. The results of the analysis show the project site s pre-development conditions generated runoff during the 85 th percentile storm event. The project site s post-development conditions are expected to generate a maximum of 1,710 cubic yards of runoff. Tables 1 and 2 present the results of the analysis for the post-development conditions, the Adobe Solar Project Only and the Adobe Solar Project and Rigel Solar Project, respectively. Table 1: Adobe Solar Project Only Condition Peak Flow and Volume Increase from an 85 th Percentile Storm Event Condition 85 th Percentile Peak Flow (cubic feet per second) Cross Section 1 (XS-1), Adobe Solar Project North Boundary 85 th Percentile Volume (acre-feet) Pre-Development Post-Development Difference between Post-Development and Pre- Development Cross Section 2 (XS-2), Rigel Solar Project North Boundary Pre-Development Post-Development Difference between Post-Development and Pre- Development Project Site Area = 160 Acres 85th percentile rainfall = 0.36 inches Table 2: Adobe Solar Project and Rigel Solar Project Condition Peak Flow and Volume Increase from an 85 th Percentile Storm Event Condition 85 th Percentile Peak Flow (cubic feet per second) Cross Section 1 (XS-1), Adobe Solar Project North Boundary 85 th Percentile Volume (acre-feet) Pre-Development Post-Development Difference between Post-Development and Pre- Development Cross Section 2 (XS-2), Rigel Solar Project North Boundary Pre-Development Post-Development Difference between Post-Development and Pre- Development Figures 1, 2, and 3 show the flow patterns in the pre-development and post-development conditions, and identify the locations of the cross sections. 6

35 Adobe Solar Project Water Quality Assessment Figures 4 and 5 show the relationship between the affect of the peak flow resulting from postdevelopment project site conditions at the downstream end of the project site for both postdevelopment conditions. In the figures, Baseline Conditions represents the pre-development condition, Project Conditions is the post-development condition, and Project-related changes is the change because of the post-development condition. 7

36 Adobe Solar Project Water Quality Assessment Figure 1: Local/Onsite Map of Flood Depths Baseline Conditions 85 th Percentile Storm Event 8

37 Adobe Solar Project Water Quality Assessment Figure 2: Local/Onsite Map of Flood Depths Project Conditions Adobe Solar Project Only 85 th Percentile Storm Event 9

38 Adobe Solar Project Water Quality Assessment Figure 3: Local/Onsite Map of Flood Depths Project Conditions Adobe Solar Project and Rigel Solar Project 85 th Percentile Event 10

39 Adobe Solar Project Water Quality Assessment Figure 4: 85th Percentile Peak Flow Distribution along XS-1, Project Adobe Solar Project Only Figure 5: 85th Percentile Peak Flow Distribution along XS-1, Project Adobe Solar Project and Rigel Solar Project 11

40 Adobe Solar Project Water Quality Assessment Per the water quality requirements, development projects must consider opportunities to reduce runoff and prevent impacts to downstream receiving waters. To meet the CGP requirements, the project site design should incorporate structural post-construction BMPs such as the following to meet the intent of these requirements: Using a portion of the project site area as a retention basin (with panels, not a dedicated basin) Constructing a dedicated infiltration/retention basin Constructing infiltration trenches Extended detention basins (where infiltration is technically infeasible) The BMPs were sized using available soil data, assuming the entire 160-acre project site would be developed, and to address the greatest change in runoff volume produced by the 85 th percentile event when comparing the pre-development conditions to post-development conditions. The proposed BMPs should be considered when the project site s plan is prepared. The table below summarizes the results of the analysis. 85 th Percentile Storm Event Volume (Post-development - Pre-development): Volume = 10.7 Cubic Yards per Acre Mitigation Measure Cost Estimate (Assuming Mitigation for Runoff Volume for up to 85 th Percentile Event) Mitigation Measure Type Area (ac) Volume Runoff (cf) Width (ft) Length (ft) Depth (ft) Infiltration Basin (IB) , $50,500 Infiltration Trench (IT) , $162,000 Shallow IB , $43,500 Shallow IB $200 IB = Infiltration Basin IT = Infiltration Trench Shallow IB = Shallow Infiltration Area (no more than 6 inches in depth) Cost Project Site Management BMPs Non-stormwater BMPs (control of non-stormwater discharges) Erosion Control BMPs o Implement wind erosion controls o Provide effective soil cover for inactive areas o o Limit use of plastic materials Ensure soil loss during each phase is equivalent or less than pre-construction soil loss 12

41 Adobe Solar Project Water Quality Assessment Sediment Control BMPs o Establish effective perimeter controls o Stabilize construction entrances/exits o Comply with sediment basin guidelines o Implement appropriate erosion control in conjunction with sediment control o Establish linear slope controls o Establish access road controls The table below summarizes the regulatory requirements that must be met to develop this project site. Regulatory Requirements/ Development Impacts Porter-Cologne Act Construction General Permit Temporary Construction BMPs Post-Development Mitigation to Address Regulatory Requirements/Development Impacts Design and implement the project site per the requirements of the Basin Plan. Adhere to the Basin Plan s water quality objectives, discharge prohibitions, and water quality standards. Develop and implement a SWPPP that meets the requirements of the CGP. Temporary BMPs such as desilting basins, erosion control blankets, and other minimum construction BMPs will be implemented as stated in the SWPPP developed for the project site. Implement post-construction BMPs. Design the project site to minimize hydromodification impacts, such as flow direction and flow volume mitigated by BMPs. All Central Valley RWQCB discharge requirements and the County of Kern s water quality regulations will be adhered to in the development and maintenance of this project site. 13

42 Adobe Solar Project Water Quality Assessment California Department of Water Resources, California s Groundwater, Bulletin 118, updated 2006 ( accessed on July 25, California Department of Water Resources, Water Data Library, (Well 32S28E34R001M) accessed on July 25, California Regional Water Quality Control Board, Central Valley Region, Water Quality Control Plan for the Tulare Lake Basin, second Edition, Revised January Federal Emergency Management Agency (FEMA) Map Service Center, Flood Maps. accessed January State Water Resources Control Board, National Pollutant Discharge Elimination System (NPDES) General Permit for Storm Water Discharges Associated with Construction and Land Disturbance Activities (Order Number DWQ, NPDES Number CAS000002), September 5, United States Department of Agriculture, Natural Resources Conservation Service, Web Soil Survey data, accessed July 26, 2011 via their website: Western Regional Climate Center, a partnership between the National Climatic Data Center, National Weather Service, the American Association of State Climatologists, and NOAA Research Institute, Monthly Climate Summary for Bakersfield, California, accessed July 22, 2011 via their website: 14

43 Appendix Adobe Solar Project Water Quality Assessment

44 Weedpatch Rancho Wible Union Bear Mountain Main Edison Herring Sandrini }þ99 Copus David 5 Wheeler Ridge }þ166 M:\Mdata\ \GIS\Adobe_VicinityMap.mxd Legend Project Boundary Highway Major Road 0 1 ADOBE SOLAR PROJECT WATER QUALITY ASSESSMENT 2 Miles Source: NAIP - National Agriculture Imagery Program, and StreetMap USA Vicinity Map Figure A-1

45 Adobe Solar Project Water Quality Assessment Description of Beneficial Uses Designations The following are descriptions of the beneficial uses identified in Section 3.2 of this report. Municipal and Domestic Supply (MUN) Uses of water for community, military, or individual water supply systems, including, but not limited to, drinking water supply. Agricultural Supply (AGR) Uses of water for farming, horticulture, or ranching, including, but not limited to, irrigation, stock watering, or support of vegetation for range grazing. Industrial Service Supply (IND) Uses of water for industrial activities that do not depend primarily on water quality, including, but not limited to, mining, cooling water supply, hydraulic conveyance, gravel washing, fire protection, or oil well repressurization. Industrial Process Supply (PRO) Uses of water for industrial activities that depend primarily on water quality. Water Contact Recreation (REC-1) Uses of water for recreational activities involving body contact with water, where ingestion of water is reasonably possible. These uses include, but are not limited to, swimming, wading, water-skiing, skin and scuba diving, surfing, white water activities, fishing, or use of natural hot springs. Non-Contact Water Recreation (REC-2) Uses of water for recreational activities involving proximity to water but where there is generally no body contact with water, nor any likelihood of ingestion of water. These uses include, but are not limited to, picnicking, sunbathing, hiking, beachcombing, camping, boating, tidepool and marine life study, hunting, sightseeing, or aesthetic enjoyment in conjunction with the above activities. Warm Freshwater Habitat (WARM) Uses of water that support warm water ecosystems, including, but not limited to, preservation or enhancement of aquatic habitats, vegetation, fish, or wildlife, including invertebrates. WARM includes support for reproduction and early development of warm water fish. Wildlife Habitat (WILD) Uses of water that support terrestrial or wetland ecosystems, including but not limited to, preservation and enhancement of terrestrial habitats or wetlands, vegetation, wildlife (e.g., mammals, birds, reptiles, amphibians, invertebrates), or wildlife water and food sources. Rare, Threatened, or Endangered Species (RARE) Uses of water that support habitats necessary, at least in part, for the survival and successful maintenance of plant or animal species established under state or federal law as rare, threatened or endangered. Ground Water Recharge (GWR) Uses of water for natural or artificial recharge of ground water for purposes of future extraction, maintenance of water quality, or halting of saltwater intrusion into freshwater aquifers.

46 Version 6/10/2009 Construction General Permit - Risk Determination Worksheet Step 1 Step 2 Step 3 Determine Sediment Risk via one of the options listed: 1. GIS Map Method - EPA Rainfall Erosivity Calculator & GIS map 2. Individual Method - EPA Rainfall Erosivity Calculator & Individual Data Determine Receiving Water Risk via one of the options listed: 1. GIS map of Sediment Sensitive Watersheds provided (in development) 2. List of Sediment Sensitive Watersheds provided Determine Combined Risk Level

47 Sediment Risk Factor Worksheet Entry A) R Factor Analyses of data indicated that when factors other than rainfall are held constant, soil loss is directly proportional to a rainfall factor composed of total storm kinetic energy (E) times the maximum 30-min intensity (I30) (Wischmeier and Smith, 1958). The numerical value of R is the average annual sum of EI30 for storm events during a rainfall record of at least 22 years. "Isoerodent" maps were developed based on R values calculated for more than 1000 locations in the Western U.S. Refer to the link below to determine the R factor for the project site. R Factor Value B) K Factor (weighted average, by area, for all site soils) The soil-erodibility factor K represents: (1) susceptibility of soil or surface material to erosion, (2) transportability of the sediment, and (3) the amount and rate of runoff given a particular rainfall input, as measured under a standard condition. Fine-textured soils that are high in clay have low K values (about 0.05 to 0.15) because the particles are resistant to detachment. Coarse-textured soils, such as sandy soils, also have low K values (about 0.05 to 0.2) because of high infiltration resulting in low runoff even though these particles are easily detached. Medium-textured soils, such as a silt loam, have moderate K values (about 0.25 to 0.45) because they are moderately susceptible to particle detachment and they produce runoff at moderate rates. Soils having a high silt content are especially susceptible to erosion and have high K values, which can exceed 0.45 and can be as large as Silt-size particles are easily detached and tend to crust, producing high rates and large volumes of runoff. Use Site-specific data must be submitted. Site-specific K factor guidance K Factor Value C) LS Factor (weighted average, by area, for all slopes) The effect of topography on erosion is accounted for by the LS factor, which combines the effects of a hillslope-length factor, L, and a hillslope-gradient factor, S. Generally speaking, as hillslope length and/or hillslope gradient increase, soil loss increases. As hillslope length increases, total soil loss and soil loss per unit area increase due to the progressive accumulation of runoff in the downslope direction. As the hillslope gradient increases, the velocity and erosivity of runoff increases. Use the LS table located in separate tab of this spreadsheet to determine LS factors. Estimate the weighted LS for the site prior to construction. LS Table LS Factor Value Watershed Erosion Estimate (=RxKxLS) in tons/acre Site Sediment Risk Factor Low Sediment Risk: < 15 tons/acre Medium Sediment Risk: >=15 and <75 tons/acre High Sediment Risk: >= 75 tons/acre Low

48 Receiving Water (RW) Risk Factor Worksheet Entry Score A. Watershed Characteristics yes/no A.1. Does the disturbed area discharge (either directly or indirectly) to a 303(d)-listed waterbody impaired by sediment? For help with impaired waterbodies please check the attached worksheet or visit the link below: 2006 Approved Sediment-impared WBs Worksheet OR A.2. Does the disturbed area discharge to a waterbody with designated beneficial uses of SPAWN & COLD & MIGRATORY? No Low

49 Combined Risk Level Matrix Receiving Water Risk Low Level 1 Sediment Risk Low Medium High Level 2 High Level 2 Level 3 Project Sediment Risk: Low 1 Project RW Risk: Low 1 Project Combined Risk: Level 1

50

51 Water Quality Assessment for Rigel Solar Project

52 Prepared For: FRV Rigel Solar, LP Prepared By: Alton Parkway Irvine, CA JN

53 Rigel Solar Project Water Quality Assessment A qualitative assessment of the project was performed to assess water quality pre- and postdevelopment conditions based on the region s applicable stormwater regulations according to the National Pollutant Discharge Elimination System (NPDES) permit requirements. The assessment was performed to characterize the baseline water quality conditions and identify potential project water quality issues, and applicable mitigation measures (best management practices or BMPs). The assessment covers the following: a. A description of the approach to the water quality assessment and evaluation of the potential impacts related to project implementation. b. Identification of the regional hydrology, local hydrology, floodplains, groundwater resources, topography, climate, soils/erosion potential, and existing water quality. c. Identification of the applicable requirements of the federal Clean Water Act (CWA), state water quality regulations (California Statewide Construction General Permit or CGP), state requirements under Section 402 of the federal CWA, beneficial uses, groundwater and surface water quality objectives, and a listing of impaired waters. d. A description of the project water quality risk assessment that was performed for the project according to the CGP (Order DWQ) to determine project risk levels. e. Identification of potential stormwater quality mitigation measures (BMPs) that may be needed based on the water quality requirements applicable to the project. This includes a qualitative BMP type selection, conceptual preliminary sizing (if treatment BMPs are applicable), and cost estimate. Since the Rigel Solar Project (project site) is adjacent to the Adobe Solar Project, two postdevelopment scenarios were evaluated to determine the impacts of developing the project site only, or developing both the project site and the Adobe Solar Project. The project site is located approximately 9.5 miles southwest of the town of Arvin and approximately 1.5 miles east of SR-99, near the intersection of Adobe Road and Crider Road, in unincorporated Kern County, California. The project site consists of two parcels, containing approximately 160 acres of vacant land. Parcel 1 consists of approximately 80 acres and is located in the north part of the southeast quarter Section 34, Township 32 South, Range 28 East, Mount Diablo Meridian. Parcel 2 consists of approximately 80 and is just south of Parcel 1. It is located in the south half of the southeast quarter of Section 34, Township 32 South, Range 28 East, Mount Diablo Meridian. The Assessor s Parcel Numbers (APNs) for the two parcels are and Site elevation varies between approximately 400 and 445 feet above mean sea level, and slopes gradually downward to the north-northwest. The project site has historically been used for agricultural production, and the land is under a Williamson Act land use contract. There are no existing structures located on-site. Site access will be provided from David Road, which is immediately adjacent to the site s southern boundary (refer to Figure A-1, Vicinity Map in the Appendix). The area surrounding the project site is primarily agricultural land. David Road is located to the south of the project site, and an agricultural processing facility is located approximately one mile east of the project site. 1

54 Rigel Solar Project Water Quality Assessment The Rigel Solar Project was designed with an emphasis on protecting the project site and downstream facilities from flood hazards and water quality impairments. This proactive approach to mitigate for runoff flow rates and volumes will be necessary to address the requirements to preserve the existing drainage patterns, flood hazard potential, and stormwater quality. Therefore, designing this project site addressed these requirements by considering the following mitigation measures: Mitigate increases in runoff volumes and rates as a result of the project site for the 85 th percentile storm using BMPs which provide infiltration or retention (either above ground or underground). Provide soil erosion control and soil stabilization during the construction phase by implementing temporary construction BMPs and by implementing a Storm Water Pollution Prevention Plan (SWPPP). Implement structures or improvements (if necessary) to ensure flood hazard protection for the project site, solar structures, and downstream flow conveyance and properties. In general, this approach will ensure protection using the 100-year flood event to maintain existing flood patterns, flow depths, and flow velocities throughout the project site and downstream. The project site is located in the Arvin-Wheeler Ridge Subbasin, part of the valley floor waters of the Tulare Lake Basin within the Central Valley Region of California. It is located 1.5 miles east of SR-99 and 11 miles south of the City of Bakersfield in Kern County, CA. The region is bordered by the San Emigdio and Tehachapi Mountains to the south and the Tejon Hills to the east. The project site is located in an area that is primarily agricultural. A desktop survey of the region was performed using topographic maps and aerial images to identify the receiving water body. No receiving surface water bodies for runoff from the project site were identified from the desktop survey. The Water Quality Control Plan for the Tulare Lake Basin, Second Edition (Basin Plan) states that normally direct precipitation percolates into valley groundwater if not lost through consumptive use, evaporation, or evapotranspiration. According to U.S. Geological Survey (USGS) topography data, the project site drains from southeast to northwest towards the New Rim Ditch with a slope length of approximately 0.7 percent. The relatively flat project site area has elevations varying between approximately 420 feet above mean sea level on the southeastern boundary and 400 feet above mean sea level on the northwestern boundary. Rainfall on the Valley portion of the basin averages less than 10 inches per year (Basin Plan, 1995). The rainfall erosivity factor (R factor) for the area is estimated to be This factor represents the total storm kinetic energy times the maximum 30-minute intensity and is directly proportional to the soil loss, when factors other than rainfall are held constant. The R factor was estimated using the United States Environmental Protection Agency (U.S. EPA) Rainfall Erosivity Factor Calculator ( The U.S. EPA defines a watershed as the area of land where all of the water that is under it or drains off of it goes into the same place ( The project site is located within the Arvin-Wheeler Ridge Subbasin. The desktop survey and Basin Plan suggest that drainage from the project site is likely lost through consumptive use, 2

55 Rigel Solar Project Water Quality Assessment evapotranspiration, or evaporation or percolates into groundwater before reaching a surface water body. The project site is located in an area designated as Zone X. This designation corresponds to areas of 0.2% annual chance flood, and areas of one percent annual chance sheet flow flooding where average depths are less than one foot, areas of one percent annual chance stream flooding where the contributing drainage area is less than one square mile, or areas protected by levees from the one percent annual chance flood. No base flood elevations or depths are shown within this zone. The project site is located within the Kern County Groundwater Basin. The basin comprises 1,950,000 acres. Overdraft of groundwater for municipal, agricultural and industrial purposes has in part led to the accumulation of salts in the basin s groundwater resources. The primary constituents of concern in the Tulare Basin are high total dissolved solids, nitrate, arsenic, and organic compounds (California Department of Water Resources, 2004). A monitoring station located near the project site was monitored between 1980 and 2000, and its data indicates that the depth to groundwater is approximately 306 feet ( The Soil Erodibility Factor (K factor) for the project site is 0.31, according to the Natural Resources Conservation Service (NRCS) soil survey data. Generally, this equates to a low potential for erosion within the project site area characterized by particles resistant to detachment. However, this is a planning-level tool, so a detailed project site-specific survey is still required for design-level analysis. The K factor represents: Susceptibility of soil or surface material to erosion Transportability of the sediment The amount and rate of runoff given a particular rainfall input, as measured under a standard condition. The Clean Water Act, as amended by the Water Quality Act of 1987, is the major federal legislation governing water quality, which was enacted to restore and maintain the chemical, physical, and biological integrity of the nation s waters. This project site drains to a water body that is designated as a federal water of the United States, however the permits associated with the Clean Water Act are not applicable to this project site. The State of California s Porter- Cologne Act requirements also apply to this project site. The Porter-Cologne Act established the State Board and the nine Regional Boards, and authorized the State Board to formulate, adopt, and revise state water policy, which may include water quality objectives, principles, and guidelines. In addition, it authorizes the State Board to adopt water quality control plans on its own initiative, which supersede Regional Water Quality Control Plans to the extent of any conflict. Article 3 of the Porter-Cologne Act directs Regional Boards to adopt, review, and revise Basin Plans, and provides specific guidance on factors, 3

56 Rigel Solar Project Water Quality Assessment which must be considered when adopting water quality objectives and implementation measures. It also allows Regional Boards to prohibit discharges in Basin Plans or in waste discharge requirements. The Central Valley Regional Water Quality Control Board (RWQCB) is responsible for the protection of beneficial uses of water resources within the Central Valley Region and uses planning, permitting, and enforcement authorities to meet this responsibility. Every water body within the jurisdiction of the RWQCB is designated a set of beneficial uses that are protected by appropriate water quality objectives and identified in the Basin Plan. The beneficial uses for minor surface waters in the Undefined Hydrologic Sub-Area (HSA ) of the Arvin-Weeler Ridge Hydrologic Area and the Kern County Groundwater Basin (DAU 258) include the following: Municipal and Domestic Supply (MUN) Agricultural Supply (AGR) Industrial Service Supply (IND) Industrial Process Supply (PRO) Water Contact Recreation (REC-1) Non-Contact Water Recreation (REC-2) Warm Freshwater Habitat (WARM) Wildlife Habitat (WILD) Rare, Threatened, or Endangered Species (RARE) Ground Water Recharge (GWR) However, no receiving surface water body was identified during the desktop survey performed for this project site. For a detailed description of how the RWQCB defines the beneficial uses, see the Appendix. Section 303 of the CWA requires that the state adopt water quality objectives for surface waters. The Basin Plan contains water quality objectives that are considered necessary to protect the specific beneficial uses it identifies (as identified in Section 5.2). Section 303(d) of the CWA specifically requires the state to develop a list of impaired water bodies and Total Maximum Daily Loads (TMDLs) plans to determine the maximum allowable pollutant load that a water body can receive and continue to meet the designated beneficial uses. Since the project site does not drain to a surface water body identified within the Basin Plan, impaired receiving surface water bodies and TMDLs will not need to be addressed by the project site. NPDES Municipal Permit Requirements The project site is not located in an area that drains to a permitted municipal separate storm sewer system (MS4) and therefore is not subject to an NPDES municipal permit. Construction General Permit The project site is subject to the requirements of the General Permit for Storm Water Discharges Associated with Construction and Land Disturbance Activities (CGP, Order DWQ) permit. It requires that any construction project disturbing more than one acre of land 4

57 Rigel Solar Project Water Quality Assessment obtain coverage, for any size parcel that is part of a larger common plan of development, or for any project site that the RWQCB requires coverage. The CGP generally requires: 1. Assessment of the Project Risk (Risks 1, 2, 3, from low risk to high risk) 2. Enrollment under the Permit through the State Water Resources Control Board (SWRCB) 3. Development and implementation of a Storm Water Pollution Prevention Plan (SWPPP) 4. Sampling of stormwater and potential sampling of receiving water (depending on project risk) 5. Reporting requirements As required by the CGP, the project site risks were evaluated based on project location, sediment discharge risks, and receiving waters risk. The results from this analysis are included in the Appendix and summarized below. Receiving water: None identified Construction duration: September 2012 to September 2013 Sediment Risk Analysis R-factor = K-factor = 0.31 LS-factor = 0.89 Sediment Yield = 4.40 tons/acre Sediment Risk Factor: Receiving Water Risk Analysis On 303(d) List for Sediment = No All Beneficial Use Impact (COLD, SPAWN, MIGR) = No Receiving Water Risk: LOW The risk assessment conducted per the data above indicates that the project site is Risk Level 1. Runoff Reduction Requirements The project is required to comply with the runoff reduction and post-construction standards according to the CGP, since the project is not within a Phase I or Phase II permit area. The project site will be required to replicate the pre-project water balance (defined as the volume of rainfall that ends up as runoff) for the smallest storms up to the 85th percentile storm event (or the smallest storm event that generates runoff, whichever is larger). The volume that cannot be addressed using nonstructural practices will be captured in structural practices and approved by the RWQCB. The CGP requires project that disturb an area exceeding two acres must do the following: Preserve the pre-construction drainage density (miles of stream length per square mile of drainage area) for all drainage areas within the project site serving a first order stream or larger stream; and, Ensure that the post-development time of concentration is equal to or greater than predevelopment time of concentration. A first order stream is defined as a stream with no tributaries. No first order streams were located during the planning evaluation; however, confirmation will need to be conducted during later phases of developing the project site. 5

58 Rigel Solar Project Water Quality Assessment The project site will result in an increase in runoff volume due to compaction of soils during construction. A hydrologic analysis was prepared to compare the expected runoff flows and volumes of pre-development with the runoff flows and volumes of two post-development scenarios, the development of the Rigel Solar Project only and the development of the Adobe Solar Project and the Rigel Solar Project together, for the 85 th percentile storm rainfall of 0.36 inches. The Basin Sizer program was used to determine the size of the 85 th percentile storm rainfall, and the output is included in the Appendix. The results of the analysis show the project site s pre-development conditions generated runoff during the 85 th percentile storm event. The project site s post-development conditions are expected to generate a maximum of 1,710 cubic yards of runoff. Tables 1 and 2 present the results of the analysis for the post-development conditions, Rigel Solar Project Only and Adobe Solar Project and Rigel Solar Project, respectively. Table 1: Rigel Solar Project Only Condition Peak Flow and Volume Increase from an 85 th Percentile Storm Event Condition 85 th Percentile Peak Flow (cubic feet per second) Cross Section 1 (XS-1), Adobe Solar Project North Boundary 85 th Percentile Volume (acre-feet) Pre-Development Post-Development Difference between Post-Development and Pre- Development Cross Section 2 (XS-2), Rigel Solar Project North Boundary Pre-Development Post-Development Difference between Post-Development and Pre- Development Project Site Area = 160 Acres 85th percentile rainfall = 0.36 inches Table 2: Adobe Solar Project and Rigel Solar Project Condition Peak Flow and Volume Increase from an 85 th Percentile Storm Event Condition 85 th Percentile Peak Flow (cubic feet per second) Cross Section 1 (XS-1), Adobe Solar Project North Boundary 85 th Percentile Volume (acre-feet) Pre-Development Post-Development Difference between Post-Development and Pre- Development Cross Section 2 (XS-2), Rigel Solar Project North Boundary Pre-Development Post-Development Difference between Post-Development and Pre- Development Figures 1, 2, and 3 show the flow patterns in the pre-development and post-development conditions, and identify the locations of the cross sections. 6

59 Rigel Solar Project Water Quality Assessment Figures 4 and 5 show the relationship between the affect of the peak flow resulting from postdevelopment project site conditions at the downstream end of the project site for both postdevelopment conditions. In the figures, Baseline Conditions represents the pre-development condition, Project Conditions is the post-development condition, and Project-related changes is the change because of the post-development condition. 7

60 Rigel Solar Project Water Quality Assessment Figure 1: Local/Onsite Map of Flood Depths Baseline Conditions 85 th Percentile Storm Event 8

61 Rigel Solar Project Water Quality Assessment Figure 2: Local/Onsite Map of Flood Depths Project Conditions Rigel Solar Project Only 85 th Percentile Storm Event 9

62 Rigel Solar Project Water Quality Assessment Figure 3: Local/Onsite Map of Flood Depths Project Conditions Adobe Solar Project and Rigel Solar Project Sites 85 th Percentile Event 10

63 Rigel Solar Project Water Quality Assessment Figure 4: 85th Percentile Peak Flow Distribution along XS-2, Project Rigel Solar Project Only Figure 5: 85th Percentile Peak Flow Distribution along XS-1, Project Adobe Solar Project and Rigel Solar Project 11