June 9, 2008 - PDF Document

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  1. June 9, 2008 Ms. Etayenesh (Ty) Asfaw Environmental Policy Analyst Water and Wetlands Department National Association of Home Builders 1201 15th St. NW Washington, DC 20005 Subject: Analysis of Draft General Construction Permit Risk Factors Dear Ms. Asfaw: URS Corporation (URS) is pleased to present this technical memorandum on the analysis of the Draft General Construction Permit Risk Factors. In summary, Sediment Risk factors appear to be calibrated properly; Receiving Water risk factors are skewed high and cause the Project Combined Risk Level to be skewed high. Based on the builder surveys, obtaining risk factor data was difficult to obtain and confusing. Recommendations are provided within the technical memorandum to simplify the risk analysis, clarify risk factor definitions, and to provide better sources for risk factor data. Sincerely, URS CORPORATION Edward F. Othmer Jr., PE, CPESC, CPSWQ Project Manager C:\Draft General Construction Permit\Draft Order\20500168 NAHB\GCP Risk Factor Tech_Memo 06-09-08.doc\10-Jun-08\SDG

  2. TABLE OF CONTENTS List of Acronyms and Abbreviations......................................................................................iii Section 1 Introduction.....................................................................................................1-1 1.1 Background........................................................................................................... 1-1 1.1.1Sediment Risk Factor Calculation.............................................................. 1-1 1.1.2 Receiving Water Risk Factor Calculation.................................................. 1-3 1.1.3 Project Risk Level...................................................................................... 1-3 Objective............................................................................................................... 1-5 1.2 Section 2 Methodology...................................................................................................2-1 2.1 2.2 CBIA Surveys..................................................................................................... GIS Tools Combined with Various Scenarios......................................................2-3 2-1 Section 3 Results ............................................................................................................3-1 3.1 3.2 CBIA Surveys.......................................................................................................3-1 GIS Tools Combined with Various Scenarios ...................................................... 3-2 Section 4 Conclusions and Recommendations............................................................4-1 4.1 4.2 Conclusions........................................................................................................... 4-1 Recommendations................................................................................................. 4-2 C:\Draft General Construction Permit\Draft Order\20500168 NAHB\GCP Risk Factor Tech_Memo 06-09-08.doc\10-Jun-08\SDG i

  3. List of Tables, Figures, and Appendices Tables Table 3-1 CBIA Survey Results Table 3-2: Receiving Water Risk Scenarios Figures Figure 1-1: Sediment Risk Factor Worksheet Figure 1-2: Receiving Water Risk Factor Worksheet Figure 1-3: Combined Risk Level Matrix Figure 2-1: Channel Stability Evaluation Flow Chart Figure 2-2: R-Value (Annual) Figure 2-3: K-Factor Figure 2-4: Slope (S) Figure 2-5: Slope Length (L) Figure 2-6: CWA 303(d)-Listed Waters Impaired by Sediment Figure 2-7: All 303(d), COLD, SPAWN, RARE, ASBS (500-ft Buffer) Figure 3-1: Sediment Risk Factor (L< 3 ft), Annual R-Value Figure 3-2: Sediment Risk Factor (L=300 ft), Annual R-Value Figure 3-3: Sediment Risk Factor (L=1,000 ft), Annual R-Value C:\Draft General Construction Permit\Draft Order\20500168 NAHB\GCP Risk Factor Tech_Memo 06-09-08.doc\10-Jun-08\SDG ii

  4. List of Acronyms and Abbreviations ASBS ATS CBIA COLD CWA GCP GIS K LS NAL NOI PRD R RARE RWQCB SPAWN SWPPP SWRCB URS Area of Special Biological Significance Active Treatment System California Building Industry Association Cold Freshwater Habitat Beneficial Use Clean Water Act General Construction Permit Graphical Information System Soil Erodibility Hillslope-length Factor, L, and a Hillslope-Gradient Factor, S. Numeric Action Level Notice of Intent Permit Registration Documents Rainfall Erosivity Rare and Endangered Species Habitat Beneficial Use Regional Water Quality Control Board Fish Spawning Habitat Beneficial Use Storm Water Pollution Prevention Plan State Water Resources Control Board URS Corporation C:\Draft General Construction Permit\Draft Order\20500168 NAHB\GCP Risk Factor Tech_Memo 06-09-08.doc\10-Jun-08\SDG iii

  5. SECTIONONE Introduction SECTION 1 INTRODUCTION 1.1 BACKGROUND The California State Water Resources Control Board (SWRCB) released the Draft General Construction Permit (GCP) in March 2008. The GCP regulates stormwater runoff from construction sites. To obtain coverage under this General Permit, dischargers must electronically file the Permit Registration Documents (PRDs), which includes a Notice of Intent (NOI), Storm Water Pollution Prevention Plan (SWPPP), and other compliance related documents required by the GCP and mail the appropriate permit fee to the SWRCB. Many stakeholders supported the risk-based approach in the Preliminary Draft GCP. As a result, the Draft GCP presents a risk approach that is intended to approximate a project’s actual risk of impacting water quality during construction activities. The Draft GCP contains an approach for estimating both sediment and receiving water risk separately, and an overall risk determination framework that reflects the applicable levels of implementation and monitoring for three risk levels. Projects determined to be Risk Level 4 (the highest risk category) will not be covered by the GCP – individual permits will be needed for these projects. The project's sediment risk and receiving water risk is calculated using the methodology in Attachment A of the GCP. For any project that spans two or more planning watersheds1, the discharger shall calculate a separate Risk Level for each planning watershed. The discharger shall notify the SWRCB of the project’s Risk Level determination(s) and shall include this as a part of the PRDs submittal. If a discharger ends up with more than one Risk Level determination, the Regional Water Board (RWQCB) may choose to break the project in to separate levels of implementation. 1.1.1Sediment Risk Factor Calculation Figure 1-1 shows the Sediment Risk Factor Calculation Worksheet that is included in Attachment A of the GCP. The following factors are used to calculate sediment risk, which are based on the Revised Universal Soil Loss Equation (RUSLE): •Rainfall Erosivity (R); •Soil Erodibility (K); and •Topography (LS). Each of these factors is defined in Attachment A of the Draft GCP. These three factors are multiplied together to determine erosion potential in tons per acre. The Site Sediment Risk Factor is defined as follows: Low: <1 ton/acre Medium: >/=1 and <75 tons/acre High: >/= 75 and <500 tons/acre Extreme: >/= 500 tons/acre 1 Planning watershed: defined by the Calwater Watershed documents as a "planning watershed (PWS)," that ranges in size from approximately 3,000 to 10,000 acres http://gis.ca.gov/catalog/BrowseRecord.epl?id=22175. C:\Draft General Construction Permit\Draft Order\20500168 NAHB\GCP Risk Factor Tech_Memo 06-09-08.doc\10-Jun-08\SDG 1-1

  6. SECTIONONE Introduction Figure 1-1: Sediment Risk Factor Worksheet 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 http://ei.tamu.edu/ to determine the R factor for the project site. 200 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 0.65. Silt-size particles are easily detached and tend to crust, producing high rates and large volumes of runoff. Refer to NRCS soil data (http://websoilsurvey.nrcs.usda.gov/app/ ) or site-specific data. 0.45 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 LS table located in separate tab of this spreadsheet to determine LS factors. Estimate the weighted LS for the site prior to construction. 1 LS Factor Value Watershed Erosion Estimate (=RxKxLS) in tons/acre 90 Site Sediment Risk Factor Low Sediment Risk: < 1 tons/acre Medium Sediment Risk: >/=1 and <75 tons/acre High Sediment Risk: >/= 75 and < 500 tons/acre Extreme Sediment Risk: >/= 500 tons/acre High C:\Draft General Construction Permit\Draft Order\20500168 NAHB\GCP Risk Factor Tech_Memo 06-09-08.doc\10-Jun-08\SDG 1-2

  7. SECTIONONE Introduction 1.1.2Receiving Water Risk Factor Calculation Figure 1-2 shows the Receiving Water Risk Factor Calculation Worksheet that is included in Attachment A of the GCP. The following factors are used to calculate receiving water risk: •Discharge directly or indirectly to a Clean Water Act (CWA) 303(d)-listed water body impaired by sediment; •Discharge to a water body with designated beneficial uses of COLD or SPAWN; •Proximity to sensitive receiving waters; •Channel stability; •Work within a receiving water; and •Use of Active Treatment System (ATS). Each of these factors is defined in Attachment A of the Draft GCP. Scores assigned to each of these factors are added together to determine a total score. The Receiving Water Risk Factor is defined as follows: Low: <10 points Medium: >/=10 and <20 points High: >/= 20 points 1.1.3Project Risk Level Results from the Sediment Risk Level and Receiving Water Risk Level Calculations are used to determine the project’s combined risk, as defined in the matrix shown in Figure 1-3. C:\Draft General Construction Permit\Draft Order\20500168 NAHB\GCP Risk Factor Tech_Memo 06-09-08.doc\10-Jun-08\SDG 1-3

  8. SECTIONONE Introduction Figure 1-2: Receiving Water Risk Factor Worksheet Receiving Water (RW) Risk Factor Worksheet Scoring Entry Score Instructions: answer all questions and add up points, then determine RW Risk Factor. Base Score: 10 points 10 A. Watershed Characteristics A.1. Does the disturbed area discharge (either directly or indirectly) to a 303(d)-listed waterbody impaired by sediment? If answer is "yes," the project is automatically a high receiving water risk project - proceed to "Combined" worksheet. For help with impaired waterbodies please check the attached worksheet or visit the link below: 2006 Approved Sediment-impared WBs Worksheet http://www.waterboards.ca.gov/tmdl/303d_lists2006approved.html Yes = 15 points No = 0 points Yes 15 http://atlas.resources.ca.gov/imaps/atlas/app.asp A.2. Does the disturbed area discharge to a waterbody with designated beneficial uses of COLD or SPAWN? Yes = 10 points No = 0 points Yes 10 http://www.ice.ucdavis.edu/geowbs/asp/wbquse.asp B. Site Characteristics B.1. Is the disturbed area more than the floodprone width1 or 500 ft (whichever is greater) from sensitive receiving water and discharge is captured and/or attenuated, settled, percolated, or infiltrated allowing for suspended solids reduction prior to entering sensitive receiving water. 2 1 Floodprone width is the width at twice the bankfull depth. 2 Requires a minimum of 100 ft. of flow through a vegetated buffer prior to discharge Yes = -5 points No = 0 points Yes -5 B.2. Is the channel stability index greater than 10? (use Channel Stability Index Ranking Worksheet) Yes = 5 points No = 0 points No 0 B.3. Discharge within water body (WB): Is construction activity located within the sensitive receiving water body? (Please note: other permits and agreements may be required.) Yes = 5 points No = 0 points No 0 B.4. Will the project utilize an Active Treatment System (ATS) operated in compliance with this General Permit to treat ALL the discharges from the site? Yes = -10 points No = 0 points No 0 Total Score RW Risk Factor 30 Low RW Risk< 10 20 20 High Medium RW Risk >= 10 and < High RW Risk>/= C:\Draft General Construction Permit\Draft Order\20500168 NAHB\GCP Risk Factor Tech_Memo 06-09-08.doc\10-Jun-08\SDG 1-4

  9. SECTIONONE Introduction Figure 1-3: Combined Risk Level Matrix Combined Risk Level Matrix Sediment Risk Low Medium High Extreme Receiving Water Risk Level 1 Level 2 Level 2 Level 3 Low Level 2 Level 2 Level 2 Level 3 Medium Level 2 Level 3 Level 3 Level 4 High Project Sediment Risk: Project RW Risk: Project Combined Risk: High High Level 3 3 3 1.2 OBJECTIVE The objective of this study was to determine if the risk calculation proposed by the SWRCB was properly calibrated (i.e., Project Combined Risk Level normally distributed). In other words, do most sites calculate to be Risk Level 2, and do fewer sites calculate to be Risk Levels 1, 3, and 4. C:\Draft General Construction Permit\Draft Order\20500168 NAHB\GCP Risk Factor Tech_Memo 06-09-08.doc\10-Jun-08\SDG 1-5

  10. SECTIONTWO Methodology SECTION 2 METHODOLOGY URS assessed the project Risk Level calculation using two methods. The first method assessed Risk Level using risk factor data collected from California Building Industry Association (CBIA) projects. The second method assessed project Risk Level calculation using Graphical Information System (GIS) tools combined with various scenarios. Each of these methods is discussed in more detail below. 2.1.1CBIA Surveys URS developed a survey form/questionnaire to evaluate the risk level of construction sites (refer to Attachment A). The survey form/questionnaire included questions consistent with the risk factor criteria that are listed in the Draft GCP and other risk factors that may be considered more appropriate to be included in the GCP; a qualitative assessment was also asked. Additionally, the survey form/questionnaire was developed to capture information to calculate site-specific Numeric Action Levels (NALs). The level of difficulty to collect the requisite information was also be tracked. CBIA distributed the survey form/questionnaire to approximately 20 construction sites that were geographically distributed throughout California. The survey form/questionnaire was populated by construction site staff and/or their consultant. URS received completed survey forms/questionnaires from 14 construction sites. URS reviewed and summarized the results of the survey forms. URS also independently checked the results of each risk factor. Where appropriate, URS adjusted the risk factor based on best professional judgment. The following assumptions were made when adjusting the risk factor or when a risk factor result was not reported by the construction site: Sediment Risk Factor: •R-factor was obtained from http://ei.tamu.edu. The start and end dates of construction (or duration) was based on data recorded on the survey form/questionnaire. •K-factor was obtained from the Natural Resources Conservation Service (NRCS) soil data (http://websoilsurvey.nrcs.usda.gov/app/ ) unless site-specific data was provided. •LS-factor was determined from topographic maps/grading plans provided by the construction site. Receiving Water Risk Factor: •If a project was located within a planning watershed (defined by the Calwater Watershed documents as a "planning watershed (PWS)," that ranges in size from approximately 3,000 to 10,000 acres http://gis.ca.gov/catalog/BrowseRecord.epl?id=22175) that was directly adjacent to a CWA 303(d)-listed water body impaired by sediment, then it was considered to discharge directly or indirectly to that listed water body, and was given a score of 15. C:\Draft General Construction Permit\Draft Order\20500168 NAHB\GCP Risk Factor Tech_Memo 06-09-08.doc\10-Jun-08\SDG 2-1

  11. SECTIONTWO Methodology •If a project was located within a planning watershed that was directly adjacent to a water body with designated beneficial uses of COLD or SPAWN, then it was considered to discharge to that water body, and was given a score of 10. •Projects located within 500 feet of a sensitive receiving water were assigned a score of 0. •Sensitive receiving waters were defined as follows: oAll CWA 303(d)-listed receiving waters regardless of impairment; oReceiving waters with COLD, SPAWN, or RARE beneficial uses; and oAreas of Special Biological Significance (ASBS). •The channel stability index of a receiving water body is site-specific. URS developed the following flow chart to evaluate whether or not a channel is considered stable. Channels considered unstable were assigned a score of 5. Figure 2-1: Channel Stability Evaluation Flow Chart Discharge Channel Lined Unlined Stable Percent of Developed Watershed Less Than 10% More Than 10% Channel Slope Percent Unstable Less Than 5% More Than 5% Stable Unstable C:\Draft General Construction Permit\Draft Order\20500168 NAHB\GCP Risk Factor Tech_Memo 06-09-08.doc\10-Jun-08\SDG 2-2

  12. SECTIONTWO Methodology 2.1.2GIS Tools Combined with Various Scenarios URS produced several GIS exhibits covering the state of California examining the sediment risk factors and receiving water risk factors where possible. A GIS shape file showing areas of probable development was also overlaid onto these figures. Sediment Risk Levels were calculated for both Statewide and areas of probable development. Sediment Risk Factor: Sediment risk factor exhibits were produced for R, K, and S (L is project specific; several slope lengths scenarios were evaluated). Information for these GIS exhibits was obtained from the following sources: •The Draft GCP refers to http://ei.tamu.edu to obtain the R-value. The calculated R-value from this website is based on the Erosivity Index Zone Map and Isoerodent Map of California presented in the EPA Storm Water Phase II Final Rule, Construction Rainfall Erosivity Waiver Fact Sheet 3.1, EPA 833-F-00-014. The source of these maps are from the Agricultural Handbook Number 703, Predicting Soil Erosion by Water: A Guide to Conservation Planning with the Revised Universal Soil Loss Equation (RUSLE), Chapter 2, pp. 21-64, January 1997. As a result, URS developed R-value maps using these sources for three scenarios: 1) annual R- value; wet season R-value (October through May); and dry season R-value June through September. The annual R-value map is shown in Figure 2-2. •The K- factor data was obtained from the NRCS soils data website (http://websoilsurvey.nrcs.usda.gov/app/), and is shown in Figure 2-3. •The average pre-developed slope (S) was assumed to be the same as the average post-developed slope (S), in percent. The slope was determined from a digital terrain model, and is shown in Figure 2-4. The slope length factor, L, is project specific and its definition is graphically shown in Figure 2-5. A number of slope lengths were evaluated including slope lengths of <3 feet, 300 feet, and 1,000 feet. The relationship between L and S are presented in Attachment A to the Draft GCP. C:\Draft General Construction Permit\Draft Order\20500168 NAHB\GCP Risk Factor Tech_Memo 06-09-08.doc\10-Jun-08\SDG 2-3

  13. SECTIONTWO Methodology Figure 2-2: R-Value (Annual) C:\Draft General Construction Permit\Draft Order\20500168 NAHB\GCP Risk Factor Tech_Memo 06-09-08.doc\10-Jun-08\SDG 2-4

  14. SECTIONTWO Methodology Figure 2-3: K-Factor S C:\Draft General Construction Permit\Draft Order\20500168 NAHB\GCP Risk Factor Tech_Memo 06-09-08.doc\10-Jun-08\SDG 2-5

  15. SECTIONTWO Methodology Figure 2-4: Slope (S) C:\Draft General Construction Permit\Draft Order\20500168 NAHB\GCP Risk Factor Tech_Memo 06-09-08.doc\10-Jun-08\SDG 2-6

  16. SECTIONTWO Methodology Figure 2-5: Slope Length (L) Receiving Water Risk Factor: URS developed a series of GIS shapefiles and/or matrices (as appropriate) to determine the Receiving Water Risk Factor for the area of probable development. Several of the risk factors (e.g., channel stability index, construction site located within a receiving water body, and use of ATS) cannot be specifically determined through this exercise. As a result, URS developed a series of matrices to calculate the risk factor score based on various scenarios. The same assumptions presented in Section 2.1.1 were applied to this method. The following GIS exhibits were prepared: •CWA 303(d)-listed receiving waters impaired by sediment (refer to Figure 2-6); •All CWA 303(d)-listed receiving waters regardless of impairment (refer to Figure 2-7); •Receiving waters with COLD, SPAWN, or RARE beneficial uses (refer to Figure 2-7); and •Areas of Special Biological Significance (ASBS) (refer to Figure 2-7). C:\Draft General Construction Permit\Draft Order\20500168 NAHB\GCP Risk Factor Tech_Memo 06-09-08.doc\10-Jun-08\SDG 2-7

  17. SECTIONTWO Methodology Figure 2-6: CWA 303(d)-Listed Waters Impaired by Sediment C:\Draft General Construction Permit\Draft Order\20500168 NAHB\GCP Risk Factor Tech_Memo 06-09-08.doc\10-Jun-08\SDG 2-8

  18. SECTIONTWO Methodology Figure 2-7: All 303(d), COLD, SPAWN, RARE, ASBS (500-ft Buffer) C:\Draft General Construction Permit\Draft Order\20500168 NAHB\GCP Risk Factor Tech_Memo 06-09-08.doc\10-Jun-08\SDG 2-9

  19. SECTIONTHREE Results SECTION 3 RESULTS This section summarizes the results of the two methods used to calculate Risk Level. 3.1 CBIA SURVEYS URS received and summarized the results of survey forms/questionnaires from 14 of the 20 construction sites that were asked to participate in this evaluation. URS also independently checked the results of each risk factor. Where appropriate, URS adjusted the risk factor based on best professional judgment. Table 3-1 summarizes the results of the surveys. Table 3-1 CBIA Survey Results Sediment Risk Receiving Water Risk Contractor's Qualitative Assessment High Low Medium Medium Low High Medium Low Extreme Contractor's Qualitative Assessment Medium Low Medium Low Low Medium Low Low Medium Incomplete Incomplete High Low Medium Size (Acres) Contractor Score High Incomplete Medium Medium Medium Medium Medium Low 1048 Incomplete Medium 35.4 High 20.6 Medium Medium 32 Extreme Extreme 21.4 Medium Medium Incomplete 24 Incomplete Medium Incomplete 42 Medium Medium 84.8 High 443 Medium Medium URS Score Medium Contractor Score Medium Medium Medium Low Medium Medium High Incomplete High Medium High Medium Medium Low High High High High URS Score Combined Risk Level 2 Level 2 Level 2 Level 2 Level 2 Level 3 Level 3 Level 3 Level 3 Level 3 Level 3 Level 3 Level 3 Level 3 Builder Builder 2 Builder 5 Builder 6 Builder 10 Builder 12 Builder 1 Builder 3 Builder 4 Builder 7 Builder 8 Builder 9 Builder 11 Builder 13 Builder 14 County Los Angeles 695.4 Fresno Sacramento Riverside Riverside Riverside Sonoma Sonoma El Dorado Alameda Contra Costa Orange San Diego San Diego 18 152 144 30 Low Low Low High High High High High High High High High High Medium High High The following statistics can be derived from the table and the supporting surveys: •R-value was provided for 14 of 14 sites; R-values were not adjusted for any of the sites. •K-factor was provided for 13 of 14 sites; K-factor was adjusted for 3 of the sites. •L was provided for 11 of 14 sites; L was adjusted for 4 of the sites. •S was provided for 12 of 14 sites; S was adjusted for 3 of the sites. •Determination of discharge to 303(d)-listed water bodies was provided for 14 of 14 sites; determination was adjusted for 1 of the sites. C:\Draft General Construction Permit\Draft Order\20500168 NAHB\GCP Risk Factor Tech_Memo 06-09-08.doc\10-Jun-08\SDG 3-1

  20. SECTIONTHREE Results •Determination of discharge to water body with COLD or SPAWN designation was provided for 14 of 14 sites; determination was adjusted for 3 of the sites. •Channel stability index was calculated for 6 of 14 sites; channel stability index was estimated for 8 of the sites. •Sediment Risk was adjusted for 4 of the 14 sites. •Receiving Water Risk was adjusted for 4 of the 14 sites. •Qualitative assessment of sediment and receiving water risks did not correlate well with calculated risks. •Most sites (9 of 14) are Risk Level 3; remaining sites (5 of 14) are Risk Level 2. •None of the sites were Risk Levels 1 or 4. •Sediment Risk factors appear to be reasonably calibrated. •Receiving Water Risk factors are skewed towards High Risk. •Combined Risk Levels are highly influenced by the Receiving Water Risk factor. 3.2 GIS TOOLS COMBINED WITH VARIOUS SCENARIOS Sediment Risk Factor: The sediment risk was calculated for the state for three different slope lengths; a one-year project duration was assumed. The model was also run for those areas of the state where development was probable. Refer to Figures 3-1 through 3-3 for a graphical presentation of the results for slope lengths of <3 feet, 300 feet, and 1,000 feet, respectively. The following statistics can be derived from the supporting GIS exhibits and results: •Annual R-value ranges from 10 to 220. •K-factor was not mapped by NRCS for approximately 48% of the state. •The K-factor ranges from 0.02 to 0.64. •The majority of the state and area of probable development are a Medium Sediment Risk Level, regardless of slope length. •Less than 3 percent of the state and area of probable development are an Extreme Sediment Risk Level. C:\Draft General Construction Permit\Draft Order\20500168 NAHB\GCP Risk Factor Tech_Memo 06-09-08.doc\10-Jun-08\SDG 3-2

  21. SECTIONTHREE Results Figure 3-1: Sediment Risk Factor (L< 3 ft), Annual R-Value C:\Draft General Construction Permit\Draft Order\20500168 NAHB\GCP Risk Factor Tech_Memo 06-09-08.doc\10-Jun-08\SDG 3-3

  22. SECTIONTHREE Results Figure 3-2: Sediment Risk Factor (L=300 ft), Annual R-Value C:\Draft General Construction Permit\Draft Order\20500168 NAHB\GCP Risk Factor Tech_Memo 06-09-08.doc\10-Jun-08\SDG 3-4

  23. SECTIONTHREE Results Figure 3-3: Sediment Risk Factor (L=1,000 ft), Annual R-Value C:\Draft General Construction Permit\Draft Order\20500168 NAHB\GCP Risk Factor Tech_Memo 06-09-08.doc\10-Jun-08\SDG 3-5

  24. SECTIONTHREE Results Receiving Water Risk Factor: Fifty possible receiving water risk scenarios were identified; these are identified in Table 3-2. Coupling the results of the GIS receiving water exhibits with the 50 possible scenarios was not feasible and would not likely yield useful information. However, results contained in Table 3-2 indicate that there is a higher probability of being ranked High Risk vs. Medium and Low. Table 3-2: Receiving Water Risk Scenarios COLD or SPAWN Listed RW More Than 500' from Sensitive RW Channel Stability Index > 10 Active Treatment System (ATS) 303(d) Listed RW Within Water Body BASE Scenario SCORE Total RW Risk Yes No Yes No Yes No Yes No Yes No Yes No Points 1 10 15 0 10 0 -5 0 5 0 5 0 -10 0 45 High Risk 2 10 15 0 10 0 -5 0 5 0 5 0 -10 0 40 High Risk 3 10 15 0 10 0 -5 0 5 0 5 0 -10 0 40 High Risk 4 10 15 0 10 0 -5 0 5 0 5 0 -10 0 35 High Risk 5 10 15 0 10 0 -5 0 5 0 5 0 -10 0 35 High Risk 6 10 15 0 10 0 -5 0 5 0 5 0 -10 0 35 High Risk 7 10 15 0 10 0 -5 0 5 0 5 0 -10 0 35 High Risk 8 10 15 0 10 0 -5 0 5 0 5 0 -10 0 35 High Risk 9 10 15 0 10 0 -5 0 5 0 5 0 -10 0 30 High Risk 10 10 15 0 10 0 -5 0 5 0 5 0 -10 0 30 High Risk 11 10 15 0 10 0 -5 0 5 0 5 0 -10 0 30 High Risk 12 10 15 0 10 0 -5 0 5 0 5 0 -10 0 30 High Risk 13 10 15 0 10 0 -5 0 5 0 5 0 -10 0 30 High Risk 14 10 15 0 10 0 -5 0 5 0 5 0 -10 0 30 High Risk 15 10 15 0 10 0 -5 0 5 0 5 0 -10 0 25 High Risk 16 10 15 0 10 0 -5 0 5 0 5 0 -10 0 25 High Risk 17 10 15 0 10 0 -5 0 5 0 5 0 -10 0 25 High Risk 18 10 15 0 10 0 -5 0 5 0 5 0 -10 0 25 High Risk 19 10 15 0 10 0 -5 0 5 0 5 0 -10 0 25 High Risk 20 10 15 0 10 0 -5 0 5 0 5 0 -10 0 25 High Risk 21 10 15 0 10 0 -5 0 5 0 5 0 -10 0 25 High Risk 22 10 15 0 10 0 -5 0 5 0 5 0 -10 0 20 High Risk 23 10 15 0 10 0 -5 0 5 0 5 0 -10 0 20 High Risk 24 10 15 0 10 0 -5 0 5 0 5 0 -10 0 20 High Risk 25 10 15 0 10 0 -5 0 5 0 5 0 -10 0 20 High Risk C:\Draft General Construction Permit\Draft Order\20500168 NAHB\GCP Risk Factor Tech_Memo 06-09-08.doc\10-Jun-08\SDG 3-6

  25. SECTIONTHREE Results COLD or SPAWN Listed RW More Than 500' from Sensitive RW Channel Stability Index > 10 Active Treatment System (ATS) 303(d) Listed RW Within Water Body BASE Scenario SCORE Total RW Risk 26 10 15 0 10 0 -5 0 5 0 5 0 -10 0 20 High Risk 27 10 15 0 10 0 -5 0 5 0 5 0 -10 0 20 High Risk 28 10 15 0 10 0 -5 0 5 0 5 0 -10 0 20 High Risk 29 10 15 0 10 0 -5 0 5 0 5 0 -10 0 20 High Risk 30 10 15 0 10 0 -5 0 5 0 5 0 -10 0 15 Medium Risk 31 10 15 0 10 0 -5 0 5 0 5 0 -10 0 15 Medium Risk 32 10 15 0 10 0 -5 0 5 0 5 0 -10 0 15 Medium Risk 33 10 15 0 10 0 -5 0 5 0 5 0 -10 0 15 Medium Risk 34 10 15 0 10 0 -5 0 5 0 5 0 -10 0 15 Medium Risk 35 10 15 0 10 0 -5 0 5 0 5 0 -10 0 15 Medium Risk 36 10 15 0 10 0 -5 0 5 0 5 0 -10 0 15 Medium Risk 37 10 15 0 10 0 -5 0 5 0 5 0 -10 0 10 Medium Risk 38 10 15 0 10 0 -5 0 5 0 5 0 -10 0 10 Medium Risk 39 10 15 0 10 0 -5 0 5 0 5 0 -10 0 10 Medium Risk 40 10 15 0 10 0 -5 0 5 0 5 0 -10 0 10 Medium Risk 41 10 15 0 10 0 -5 0 5 0 5 0 -10 0 10 Medium Risk 42 10 15 0 10 0 -5 0 5 0 5 0 -10 0 10 Medium Risk 43 10 15 0 10 0 -5 0 5 0 5 0 -10 0 10 Medium Risk 44 10 15 0 10 0 -5 0 5 0 5 0 -10 0 5 Low Risk 45 10 15 0 10 0 -5 0 5 0 5 0 -10 0 5 Low Risk 46 10 15 0 10 0 -5 0 5 0 5 0 -10 0 5 Low Risk 47 10 15 0 10 0 -5 0 5 0 5 0 -10 0 5 Low Risk 48 10 15 0 10 0 -5 0 5 0 5 0 -10 0 0 Low Risk 49 10 15 0 10 0 -5 0 5 0 5 0 -10 0 0 Low Risk 50 10 15 0 10 0 -5 0 5 0 5 0 -10 0 -5 Low Risk The following statistics can be derived from the supporting GIS exhibits and Table 3-2: •Approximately 12% of the state discharges to CWA 303(d)-listed water bodies impaired by sediment. •Approximately 6% of the state is within a 500-foot buffer of sensitive receiving waters. •58% of the scenarios are High Risk. C:\Draft General Construction Permit\Draft Order\20500168 NAHB\GCP Risk Factor Tech_Memo 06-09-08.doc\10-Jun-08\SDG 3-7

  26. SECTIONTHREE Results •28% of the scenarios are Medium Risk. •14% of the scenarios are Low Risk. •Receiving Water Risk factors are skewed towards High Risk. •Combined Risk Levels are highly influenced by the Receiving Water Risk factor. •Use of ATS did not reduce High Risk to Medium Risk for 29 scenarios. •Discharge to a CWA 303(d)-listed water body or receiving water body with a designated beneficial use of COLD or SPAWN causes the site to be High Risk. C:\Draft General Construction Permit\Draft Order\20500168 NAHB\GCP Risk Factor Tech_Memo 06-09-08.doc\10-Jun-08\SDG 3-8

  27. SECTIONFOUR Conclusions and Recommendations SECTION 4 CONCLUSIONS AND RECOMMENDATIONS 4.1 CONCLUSIONS The survey that was based on the Draft GCP was difficult for contactors to complete. While all contactors included the R-Factor, only 93% of those surveyed included a K factor. Only 71% of those surveyed included information to calculate LS. However, the CSI calculation seemed to cause contractors the most trouble with only 43% including data on it. Many stakeholders commenting on the Preliminary Draft GCP favored a system where monitoring requirements and possibly effluent limits would be contingent on the relative risk levels for individual sites. Clearly a system for evaluating the risk of a site would be required. However, the system that has been presented in the Draft GCP is incredibly complex, and it appears to place inordinate weight on factors that have little bearing on the overall site risk, while at the same time the model diminishes the importance or even completely ignores many basic risk factors. Basic risk factors not addressed include: •Size of the site •Length of time of the active construction phase •No credit for phasing disturbance and limiting amount of disturbed land present at any one time •No allowance for limiting disturbance activities to low risk seasons •No allowance for more detailed evaluation of distance of disturbed activities from the receiving water •The failure to assign risk credits to any traditional or innovative BMP technology other than an ATS system The proposed risk assessment system also has the major drawback of being completely beyond the expertise of the average operator to implement, and will require detailed studies subcontracted to teams consisting of hydrologists, geologists, soil scientists, and geomorphologists. This CGP is supposed to regulate construction sites a small as one acre. Such small operators/sites cannot spend the huge cost required to hire experts to perform the type of surveys and evaluations necessary. In Table 2 of the Draft GCP, a maximum sheet flow length is assigned to various percentage slopes. There are only three categories, and the first category covers the slope range from “0-25%”, where a maximum 20 ft. of sheet flow length is allowed. Several comments on this issue are below regarding the categorical choices in Table 2, and the confusing use of alternative sheet flow lengths in Attachments A and C. Both Attachment A, the spreadsheet for risk, and Attachment C, the spreadsheet for turbidity, have tables for choosing various sheet flow lengths (the L/S Tables). These Tables list 17 different length ranges, from <3 feet, up to 1000 feet. Only five of the 17 choices are less than 20 feet, and there is no choice that is exactly 20 feet, which is the prescribed length in the Draft Permit for all land with 0-25% slope. If a 20 C:\Draft General Construction Permit\Draft Order\20500168 NAHB\GCP Risk Factor Tech_Memo 06-09-08.doc\10-Jun-08\SDG 4-1

  28. SECTIONFOUR Conclusions and Recommendations foot sheet flow is mandated for all L/S, why are the large majority of choices in the models longer than 20 feet, and none equal to 20 feet? 4.2 RECOMMENDATIONS •The use of the TAMU website certainly simplifies the process but it needs further explanation for what it does and how to use it. The term erosion index needs better definition. If the graphic county function is used the sheet often returns R=0. Furthermore, based on conversations with EPA and TAMU representatives, the website is based on old data and is not maintained. It is recommended that R-Values be obtained from the USDA-NRCS National RUSLE2 Database. •K factors can be a weakness particularly on projects where the substrate soils are exposed. The K values given for sites in the NRCS web soil survey are for surface soils. •The LS Factor was confusing to many whom completed the survey form/questionnaire. More prescriptive guidance should be provided to calculate the LS factor. •The Slope Length Factor (LS) is problematic. The Revised Universal Soil Loss Equation (RUSLE) is a model that predicts slope erosion. As used in this spreadsheet it requires selecting a single LS value to characterize the whole site. On a large complex project trying to characterize LS with a single value is not really possible because erosion, transport and deposition depend so much on location and surface hydraulics. RUSLE2 program has a profile routine that allows the entry of complex slopes and different soil compositions. However, this routine would represent only one section trough the site. While it might be a better characterization of the conditions it still might not represent the real erosion hazard well. The Water Erosion Prediction Program (WEPP) is another option, which provides a means to integrate multiple slope profiles within a single drainage basin and could be a more appropriate tool for this application. •Credit should be given when the following are implemented: oPhasing disturbance and limiting amount of disturbed land present at any one time. oLimiting disturbance activities to low risk seasons. oUse of traditional or innovative BMP technology other than an ATS system. oSelf containment or in other words not allowing the site to discharge. •Following are risk factors that should be considered: oSize of the site. oLength of time of the active construction phase. C:\Draft General Construction Permit\Draft Order\20500168 NAHB\GCP Risk Factor Tech_Memo 06-09-08.doc\10-Jun-08\SDG 4-2

  29. SECTIONFOUR Conclusions and Recommendations •The channel stability index risk factor should not be included and yields relatively information for the level of effort required to assess its score. Rather, the GCP should work with the five other receiving water risk parameters to develop a more efficient calculation of risk. •We have found one other State, Vermont, which has formally adopted a risk assessment scheme into their CGP. (Details of the Vermont Risk Evaluation Process are contained in Appendix A to the Vermont CGP.) This plan is certainly not perfect, and certainly needs significant modification to meet the differing circumstances found in California. The Vermont CGP far exceeds the requirements of the EPA CGP, as well as almost all other State CGPs. However, the Vermont style risk assessment has the virtue of being much simpler than that proposed by the SWRCB, and it also addresses many of the omissions from the proposed California Risk Assessment process. Concepts in the Vermont model could be used as the backbone of a suggested risk model, with input from builders as to what specifics they would like to see incorporated into a simpler risk assessment scheme. Any alternative risk assessment should include the following improvements: •Sites of five acres or less should be able to be evaluated by a construction person certified in stormwater management, and not require professional scientists and engineers. •It should also allow risk credits for a range of innovative and effective BMP technologies, not just for ATS. The following is an attempt to devise a simpler Site Risk Assessment Procedure for the California CGP. It generally follows the outline of the Vermont Risk Assessment Process, but tailors the questions to 1) be more appropriate for California, a much larger and more diverse State, and 2) to include additional factors not included in the original Vermont process that we believe are important in determining overall site risk. Preliminary Risk Evaluation 1.Is the proposed watershed 303(d) impaired due to sediment, or will there be discharge to a water body with a designated beneficial uses of COLD or SPAWN? 2.Will the project have any stormwater discharges from the construction site to receiving waters that do not pass through a 100 ft. (minimum) vegetated, undisturbed buffer? (Buffer may be located on or off-site, as long as it remains undeveloped for the duration of the permit.) 3.Will any portion of the disturbed area be within 500 ft. or within the flood prone width (whichever is greater) of the receiving water? 4.Will the project have disturbed earth in any one location for more than 7 consecutive calendar days without temporary or final stabilization? 5.Will the project have more than five acres disturbed at any one time? 6.Will the disturbed area include more than 1 acre with a slope of 15% or greater? C:\Draft General Construction Permit\Draft Order\20500168 NAHB\GCP Risk Factor Tech_Memo 06-09-08.doc\10-Jun-08\SDG 4-3

  30. SECTIONFOUR Conclusions and Recommendations If the answer to allof the above questions is “no”, then the proposed site automatically qualifies as a low risk project. If the answer to any one question is yes, the operator must proceed to Part 2 of the Risk Evaluation. Note that for a site meeting these criteria, no average soil K value or other complex site evaluation is required. Detailed Risk Evaluation, Factors Contributing to Risk This portion of the questionnaire assigns scores for various risk factors that can be determined through normal survey and investigations of a proposed site. The scoring rules for each question immediately follows the question. 1.Will the site, in total, disturb more than 5 acres of soil? (Score: Yes=+10, No=0) 2.Will the site, in total, disturb more than 50 acres of soil? (Score cumulative with Question 1: Yes=+5, No=0) 3.Does the disturbed area discharge (either directly or indirectly) to a303(d)-listed water body impaired by sediment? (Score: Yes=15 No=0) 4. Does the disturbed area discharge to a water body with designated beneficial uses of COLD or SPAWN? (Score: Yes=10, No=0) 5.Will the proposed project have earth disturbance within of 100 ft. (horizontal) upslope of any pond or 50 ft. horizontal upslope of any rivers or streams (perennial or seasonal)? (Score: Yes=+5, No=0) 6.Will the project have disturbed earth in any one location for more than 14 consecutive calendar days, without temporary or final stabilization? (Score: Yes=+5, No=0) 7.Will a disturbed area greater than one acre, or greater than 5% of the total disturbed area (whichever is larger), be on soil that has a slope steeper than 15%? (Score: Yes=+5, No=0) 8.Will more than 50% of the disturbed area on the site have a slope greater than 5%, or will the average slope of the disturbed area on the site be greater than 5%? (Score: Yes=+10, No=0) 9.Will the weighted average K factor for the disturbed soils on the site exceed 0.36 (Score: Yes=+5, No=0) 10.Is construction activity located within the sensitive receiving water body? (Please note: other permits and agreements may be required.) (Score: Yes=+5, No=0) Risk Attenuations This portion lists various means of risk attenuation. Scores from this section are negative, and deducted from risk points accrued from Part 2. C:\Draft General Construction Permit\Draft Order\20500168 NAHB\GCP Risk Factor Tech_Memo 06-09-08.doc\10-Jun-08\SDG 4-4

  31. SECTIONFOUR Conclusions and Recommendations 1.Will the stormwater leaving the construction site pass through at least 100 feet of established vegetated buffer before entering a receiving water, and will disturbed areas have a maximum of seven days pass before temporary or permanent stabilization is implemented? (Score: Yes =-3, No=0) 2.Will all of the disturbed area be further than 500 ft. or outside the flood prone width (whichever is greater) of the receiving water? (Score (Yes=-3, No=0) 3.Will the project be phased so that there are never more than 5 acres of disturbed, unstabilized area at one time? (Note: types of acceptable stabilization can be specified.) (Score: Yes=-5, No=0) 4.Will the project include less than 2 acres of disturbance on soil with an erodibility factor higher than K=0.25? (Note: A larger acreage or a percentage and/or different K factor may be more appropriate, but the question could remain the same.) (Score: Yes=-5, No=0) 5.Will the project include less than 2 acres of disturbance on soil that is greater than 5% slope? (Score: Yes=-5, No=0) 6.For arid or semiarid areas with defined wet and dry seasons, will land disturbing activities be limited to the dry season, and either completed to final stabilization or semi-permanently stabilized during the wet season? (Note: types of acceptable stabilization can be specified.) (Score: Yes=-5, No=0) 7.If the site is located in an MS4, will runoff from the site discharge into a common stormwater detention or other treatment system where suspended solids will be removed prior to entering a receiving water, and will the site be in complete compliance with all of the local MS4 provisions? (Score: Yes=-10, No=0) 8.Select one of the following, if it is applicable to the site: Will the site be graded and designed with a combination of various BMPs, including infiltration, limiting impervious areas, terracing, slope management, and vegetative buffers, so that A) There will be no runoff from rain events that do not exceed the two year, 24 hour rain event for the site, B) The runoff from the site will not exceed previous use both in quantity and velocity, or C) the percent infiltration or water retention will be at least 85% that of an undeveloped area of similar terrain. (Score: A=-10, B=-7, C=-5, none of the above=0) 9.Will the project utilize an Active Treatment System (ATS) operated in compliance with this General Permit to treat ALL the discharges from the site that can feasibly be collected and directed to the ATS treatment system(s)? (Score: Yes=-12, No=0) The above is only intended to be a guide, and URS suggests fine tuning may be necessary. C:\Draft General Construction Permit\Draft Order\20500168 NAHB\GCP Risk Factor Tech_Memo 06-09-08.doc\10-Jun-08\SDG 4-5

  32. SECTIONFOUR Conclusions and Recommendations Suggested scoring ranges: a.Complies with Part 1—Low Risk Site. b.Score <10 = Low Risk c.Score 10 to <20 = Medium Risk d.Score 20 to 30 = High Risk e.Score >30 = Extreme Risk C:\Draft General Construction Permit\Draft Order\20500168 NAHB\GCP Risk Factor Tech_Memo 06-09-08.doc\10-Jun-08\SDG 4-6

  33. ATTACHMENT Builder Survey C onst r uc t ion S it e R isk E val uat ion Sit e Inf or mat ion* 1. Name of Person Completing Survey 2. Phone Number: 3. Site Name: 4. City: 5. County: 6. Latitude: 7. Longitude: 8. General description of project (e.g., 500 home subdivision in Los Angeles County; 400 home redevelopment in Anaheim, etc.): Overall Project Size (acres): 9. 10. Maximum Area of Disturbed Soil (acres) at any one time 11. Will the project have disturbed earth in any one location for more than 14 consecutive calendar days without temporary or final stabilization? Number of locations where storm water leaves the project boundaries (i.e., discharge points): Is each discharge point accessible for sampling? Yes No 12. 13. Yes No Yes No 14. Do you have safe, public access to the receiving water both upstream and downstream of the point where your discharge enters the receiving water, to collect samples? If no, please describe what prevented access: 15. Private property Current owner information not available No road access Characteristics of water body (dense vegetation, steep slopes, etc. Other:_____________________________ Please attach the following: 16. Project Vicinity Map Yes No Yes No Yes No Yes No 17. Project Topographical Map (Grading Plan) 18. Water Pollution Control Drawings (i.e., BMP Plans) 19. Photographs of Site: All information collected from this survey will be kept confidential and specific project information will not be released to the State Water Resources Control Board. 7

  34. ATTACHMENT S ediment R isk F ac t or Inf or mat ion The following questions are directly from the Draft Construction Permit (Appendix A) Builder Survey Degree of Difficulty Answering Question High Medium Low High Medium Low What is the erosivity factor “R” for the site? Refer to http://ei.tamu.edu/ to determine the R factor for the project site. 20. What is the soil-erodibility factor “K” (weighted average, by area, for all site soils) Refer to NRCS soil data (http://websoilsurvey.nrcs.usda.gov/app/ ) or site- specific data. What is the average Length of Slope (L) on the site (ft)? 21. 22. High Medium Low High Medium Low High Medium Low What is the average Slope Inclination (S) on the site (%)? 23. What is the corresponding area-weighted (LS) factor? Refer to the table shown below. 24. Average Watershed Slope (%) Sheet Flow Length (ft) 0.2 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.5 0.07 0.07 0.07 0.07 0.07 0.07 0.08 0.08 0.09 0.09 0.10 0.10 0.10 0.11 0.12 0.12 0.13 1.0 0.09 0.09 0.09 0.09 0.09 0.10 0.13 0.14 0.15 0.17 0.18 0.19 0.20 0.22 0.24 0.26 0.27 2.0 0.13 0.13 0.13 0.13 0.13 0.16 0.21 0.25 0.28 0.33 0.37 0.40 0.43 0.48 0.56 0.63 0.69 3.0 0.17 0.17 0.17 0.17 0.17 0.21 0.30 0.36 0.41 0.50 0.57 0.64 0.69 0.80 0.96 1.10 1.23 4.0 0.20 0.20 0.20 0.20 0.20 0.26 0.38 0.47 0.55 0.68 0.79 0.89 0.98 1.14 1.42 1.65 1.86 5.0 0.23 0.23 0.23 0.23 0.23 0.31 0.46 0.58 0.68 0.86 1.02 1.16 1.28 1.51 1.91 2.25 2.55 6.0 0.26 0.26 0.26 0.26 0.26 0.36 0.54 0.69 0.82 1.05 1.25 1.43 1.60 1.90 2.43 2.89 3.30 8.0 0.32 0.32 0.32 0.32 0.32 0.45 0.70 0.91 1.10 1.43 1.72 1.99 2.24 2.70 3.52 4.24 4.91 10.0 0.35 0.37 0.38 0.39 0.40 0.57 0.91 1.20 1.46 1.92 2.34 2.72 3.09 3.75 4.95 6.03 7.02 12.0 0.36 0.41 0.45 0.47 0.49 0.71 1.15 1.54 1.88 2.51 3.07 3.60 4.09 5.01 6.67 8.17 9.57 14.0 0.38 0.45 0.51 0.55 0.58 0.85 1.40 1.87 2.31 3.09 3.81 4.48 5.11 6.30 8.45 10.40 12.23 16.0 0.39 0.49 0.56 0.62 0.67 0.98 1.64 2.21 2.73 3.68 4.56 5.37 6.15 7.60 10.26 12.69 14.96 20.0 0.41 0.56 0.67 0.76 0.84 1.24 2.10 2.86 3.57 4.85 6.04 7.16 8.23 10.24 13.94 17.35 20.57 25.0 0.45 0.64 0.80 0.93 1.04 1.56 2.67 3.67 4.59 6.30 7.88 9.38 10.81 13.53 18.57 23.24 27.66 30.0 0.48 0.72 0.91 1.08 1.24 1.86 3.22 4.44 5.58 7.70 9.67 11.55 13.35 16.77 23.14 29.07 34.71 40.0 0.53 0.85 1.13 1.37 1.59 2.41 4.24 5.89 7.44 10.35 13.07 15.67 18.17 22.95 31.89 40.29 48.29 50.0 0.58 0.97 1.31 1.62 1.91 2.91 5.16 7.20 9.13 12.75 16.16 19.42 22.57 28.60 39.95 50.63 60.84 60.0 0.63 1.07 1.47 1.84 2.19 3.36 5.97 8.37 10.63 14.89 18.92 22.78 26.51 33.67 47.18 59.93 72.15 <3 6 9 12 15 25 50 75 100 150 200 250 300 400 600 800 1000 The following questions are supplemental to the Draft Construction Permit (Appendix A) 25. What is the duration of construction (months)? 26. Will construction occur during the wet season (generally defined from October to May) Yes No 27. Will construction occur over multiple wet seasons? Yes No Construction Phase Anticipated Duration Percent of Site Being Actively Graded 28. 29. 30. 31. 32: Preliminary Stage (Pre-Construction) Mass Grading Stage Street and Utilities Stage Vertical Construction Stage Post-Construction Stage All information collected from this survey will be kept confidential and specific project information will not be released to the State Water Resources Control Board. 8

  35. ATTACHMENT S ediment R isk F ac t or Inf or mat ion (C ont inued) 33. Please select the soil texture that best describes the site Builder Survey Sand Loamy Sand Sandy Loam Loam Silt Sandy Clay Loam Silty Clay Loam Sandy Clay Clay Silty Loam Clay Loam Silty Clay If available, provide the results of ASTM D-422 (particle size analysis) to specify the following percentages: 34. What is the % Gravel? 35. What is the % Sand? 36. What is the % Very Fine Sand? 37. What is the % Silt? 38. What is the % Clay? 39. What % of particles is less than 0.02 mm? The following questions are directly from the Draft Construction Permit (Appendix C) For Questions 37 through 40 refer to NRCS Web Soil Survey (www. http://websoilsurvey.nrcs.usda.gov/app/), or from the procedures defined in NRCS Technical Release 55 (Urban Hydrology for Small Watersheds) 40. Area of site that is Hydrologic Soil Group A (acres) Degree of Difficulty Answering Question High Medium Low High Medium Low High Medium Low High Medium Low High Medium Low 41. Area of site that is Hydrologic Soil Group B (acres) 42. Area of site that is Hydrologic Soil Group C (acres) 43. Area of site that is Hydrologic Soil Group D (acres) 44. What is the 2-year, 24-hour precipitation (inches) Refer to Western Regional Climate Center (www.wrcc.dri.edu), NRCS Field Offices (http://offices.sc.egov.usda.gov/locator/app?state=ca), or local public works and flood control agencies Select the Storm Type that your site is subject to Refer to NRCS Technical Release 55 (Urban Hydrology for Small Watersheds) for storm types in California - (www.info.usda.gov/CED/ftp/CED/tr55.pdf) Describe the Cover factor “C” that best represents the site; refer to the attached Cover Factor Table 45. I IA II High Medium Low 46. High Medium Low High Describe the Practice factor “P” that best represents the site; refer to the 47. All information collected from this survey will be kept confidential and specific project information will not be released to the State Water Resources Control Board. 9

  36. ATTACHMENT attached Practice Factor Table Builder Survey Medium Low High Medium Low High Medium Low 48. Will detention basins be used to capture the 2-year, 24-hour storm event or 3,600 cubic feet per acre from the entire site, whichever is greater? Yes No 49. Will runoff from the site be self-contained from the entire site (i.e., ponded and not allowed to discharge)? Yes No All information collected from this survey will be kept confidential and specific project information will not be released to the State Water Resources Control Board. 10

  37. ATTACHMENT Builder Survey COVER FACTOR C VALUES FOR CONSTRUCTION-SITE BMPS Treatment C-Factor 1.00 0.89 0.90 0.80 1.20 1.20 0.90 0.90 0.64 0.54 0.38 0.66-1.30 0.76-1.31 0.61 0.01 0.01-0.019 0.14-0.57 0.28-0.60 0.05 1.05 0.29-0.78 0.68 0.94 0.71-0.90 0.66 0.40 0.05 0.05 0.35 Bare soil conditions Freshly disked to 6-8 in. After one rain Loose to 12 in. smooth Loose to 12 in. rough Compacted root raked Compacted bulldozer scraped across slope Same except root raked across Rough irregular tracked all directions Seed and fertilize, fresh, unprepared seedbed Same except after 6 months Seed, fertilize after 12 months Undisturbed except scraped Scarified only Sawdust 2 in. deep, disked in Asphalt/Concrete Pavement Asphalt emulsion 1210 gal/acre 605 gal/acre 302 gal/acre Gravel (Diameter = 25-50 mm) at 90 tons/ac Dust binder 605 gal/acre 1210 gal/acre Other chemicals Aquatain Aerospray 70, 10% cover PVA Terra-Tack SeedingsA Temporary, 0 to 60 daysB Temporary, after 60 days Permanent, 2 to 12 months Brush All information collected from this survey will be kept confidential and specific project information will not be released to the State Water Resources Control Board. 11

  38. ATTACHMENT Builder Survey PRACTICE FACTOR P VALUES FOR CONSTRUCTION-SITE BMPS Treatment Bare Soil With No Cover Compact and smooth, scraped with bulldozer or scraper up and downhill. Same condition, except raked with bulldozer root rake up and downhill. Compact and smooth, scraped with bulldozer or scraper across the slope. Same condition, except raked with bulldozer root rake across the slope. Loose as a disked plow layer. Rough, irregular surface equipment tracks in all directions. Loose with rough surface greater than 12 inches depth. Loose with smooth surface greater than 12 inches depth. Sediment Containment Systems (a.k.a. Sediment Trap/Basin) Bale or Sandbag barriers Rock (Diameter = 25-50 mm) Barriers at Sump Location Silt-Fence Barrier Contour Furrowed Surface Must be maintained throughout construction activities, otherwise P-factor = 1.00. Maximum length refers to downslope length. Slope (%) Max. Length (ft) 1 to 2 400 3 to 5 300 6 to 8 200 9 to 12 125 13 to 16 80 17 to 20 65 > 20 50 Terracing Must contain 2-year, 24-hour runoff volumes without overflowing, otherwise P-factor = 1.00. P Factor 1.3 1.2 1.2 0.9 1.0 0.9 0.8 0.9 0.10-0.901 0.90 0.80 0.60 0.60 0.50 0.50 0.60 0.70 0.80 0.80 0.12 0.10 0.12 0.14 0.16 0.18 0.60 0.80 Slope (%) 1 to 2 3 to 8 9 to 12 13 to 16 17 to 20 > 20 Grass Buffer Strips to Filter Sediment-Laden Sheet Flows Strips must be at least 50 feet wide and have a ground-cover value of 65% or greater, otherwise P-factor = 1.00. Basin Slope 0% to 10% 11% to 24% 1Should be constructed as the first step in over-lot grading. All information collected from this survey will be kept confidential and specific project information will not be released to the State Water Resources Control Board. 12

  39. ATTACHMENT R ec eiving W at er R isk F ac t or Inf or mat ion The following questions are supplemental to the Draft Construction Permit (Appendix A) Builder Survey Degree of Difficulty Answering Question High Medium Low High Medium Low 50. Identify the receiving water body to which the site drains 51. Where did you obtain this information from? Regional Water Quality Control Board Website USGS Other:____________ Less than 1 mile 1-10 miles More than 10 miles from site boundary Yes No 52. How far is the site from the receiving water? High Medium Low 53. Does the site discharge directly to the receiving water body (i.e., does not commingle with offsite discharges before entering the receiving water body? 54. How does discharge from the site reach the receiving water body? High Medium Low Open natural channel Open hardened channel Through an offsite storm drain system Overland sheet flow Other:____________ Yes No High Medium Low 55. Does the site discharge to any of the following types of “Environmentally Sensitive Areas”? - Clean Water Act Section 303(d) impaired water body - A water body with a Total Maximum Daily Load (TMDL) - Areas of Special Biological Significance - Water bodies designated with the RARE beneficial use - Areas designated as preserves or their equivalent under the Multi Species Conservation Program - California Coastal Commission’s Environmentally Sensitive Habitat 56. Does the receiving water body have a TMDL for sediment, siltation, or turbidity? High Medium Low Yes No High Medium Low All information collected from this survey will be kept confidential and specific project information will not be released to the State Water Resources Control Board. 13

  40. ATTACHMENT R ec eiving W at er R isk F ac t or Inf or mat ion (C ont inued) The following questions are directly from the Draft Construction Permit (Appendix A) Builder Survey Degree of Difficulty Answering Question High Medium Low 57. Does the disturbed area discharge (either directly or indirectly) to a 303(d)-listed water body impaired by sediment? Refer to http://atlas.resources.ca.gov/imaps/atlas/app.asp or http://www.waterboards.ca.gov/tmdl/303d_lists2006approved.html 58. Does the disturbed area discharge to a water body with designated beneficial uses of COLD or SPAWN? Refer to http://www.ice.ucdavis.edu/geowbs/asp/wbquse.asp 59. Is the disturbed area more than the floodprone width1 or 500 ft (whichever is greater) from sensitive receiving water and discharge is captured and/or attenuated, settled, percolated, or infiltrated allowing for suspended solids reduction prior to entering sensitive receiving water. 2 1Floodprone width is the width at twice the bankfull depth. 2Requires a minimum of 100 ft. of flow through a vegetated buffer prior to discharge 60. Discharge within water body (WB): Is construction activity located within the sensitive receiving water body? Yes No Yes No High Medium Low Yes No High Medium Low Yes No High Medium Low High Medium Low 61. Will the project utilize an Active Treatment System (ATS) operated in compliance with this General Permit to treat ALL the discharges from the site? Please complete the next series of questions regarding Channel Stability. The following instructions define where you should collect the data. 1The length of stream channel to be analyzed depends on the width and length of the channel. Data shall be collected from at least two sites within a distance of 30 bankfull channel widths. The sites shall be located in portions of the channel reach with relatively uniform width and gradient. For example, a 20 foot-wide channel would require data from at least two sites within a 600 foot distance. If sections of channel within the 30 bankfull width distance are immediately upstream or downstream of steps, culverts, grade controls, tributary junctions, or other features and structures that significantly affect the shape and behavior of the channel, a distance of longer than 30 bankfull widths must be analyzed. Yes No All information collected from this survey will be kept confidential and specific project information will not be released to the State Water Resources Control Board. 14

  41. ATTACHMENT Channel Stability Index Rating (From B.2 Receiving Water Risk Assessment)1 62. Primary bed material Bedrock Boulder/Cobble Gravel 0 1 63. Bed/bank protection Yes No (with) 0 1 64. Degree of incision (Relative ele. Of "normal" low water; floodplain/terraces @ 100%) 0-10% 11-25% 26-50% 4 3 65. Degree of constriction (Relative decrease in top-bank width from up to downstream) 0-10% 11-25% 26-50% 0 1 66. Streambank erosion (Each Bank) None Fluvial Mass Wasting Left 0 1 Right 0 1 67. Streambank instability (Percent of each bank failing) 0-10% 11-25% 26-50% Left 0 0.5 Right 0 0.5 68. Established riparian woody-vegetative cover (Each bank) 0-10% 11-25% 26-50% Left 2 1.5 Right 2 1.5 69. Occurrence of bank accretion (Percent of each bank with fluvial deposition) 0-10% 11-25% 26-50% Left 2 1.5 Right 2 1.5 70. Stage of channel evolution I II III 0 1 2 71. Composition of adjacent side slope N/A Bedrock Boulders Left 0 0.5 Right 0 0.5 72. Percent of slope (length) contributing sediment 0-10% 11-25% 26-50% Left 0 0.5 Right 0 0.5 73. Severity of side-slope erosion None Low Moderate Left 0 0.5 1.5 Right 0 0.5 1.5 Builder Survey Score (Fill in Shaded Cells) Sand 3 Silt Clay 4 2 1 bank protected 2 2 banks 3 51-75% 1 76-100% 0 2 51-75% 3 76-100% 4 76-100% 2 2 76-100% 0 0 2 (failures) 2 2 51-75% 1.5 1.5 1 1 51-75% 0.5 0.5 1 1 51-75% 0.5 0.5 76-100% 0 0 VI 1.5 Fines 2 2 76-100% 2 2 1 1 IV 4 V 3 Gravel-SP 1.5 1.5 1 1 51-75% 1.5 1.5 1 1 High 2 2 All information collected from this survey will be kept confidential and specific project information will not be released to the State Water Resources Control Board. 15

  42. ATTACHMENT Builder Survey Degree of Difficulty Answering Question: Over al l Quest ions 74. On a scale of 1 to 10 (with 1 being the easiest and 10 being the hardest) How difficult was it to read, understand, and then complete this survey? Low High Medium 1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10 1 -3 hours 4-5 hours 6-10 hours More than 10 hours 75. On a scale of 1 to 10 (with 1 being the easiest and 10 being the hardest) How difficult was it to collect the information used in this survey? 76. How many hours did it take you to complete this survey? 77. What was the approximate cost for you to complete the survey (please include labor, data gathering, field work, etc.) Please describe what you think your Sediment Risk would be: 78. Low Medium High Exceptional Low Medium High 79. Please describe what you think your Receiving Water Risk would be: 80. Are there any other factors regarding risk that you think would be appropriate to consider? Thank You! All information collected from this survey will be kept confidential and specific project information will not be released to the State Water Resources Control Board. 16