Risk Determination Worksheet

Transcription

1 Appendix 1 Risk Determination Worksheet Step 1 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 Step 2 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 Step 3 Determine Combined Risk Level DWQ 1 September 2, 2009

2 EPA NPDES - Welcome to the Lower Erosivity Index Calculator Page 1 of 1 10/29/2010 National Pollutant Discharge Elimination System (NPDES) Recent Additions Contact Us Print Version Search NPDES: EPA Home > OW Home > OWM Home > NPDES Home > Basic Information Municipal MS4s Construction Activities Industrial Activities Road-Related MS4s Menu of BMPs Green Infrastructure Urban BMP Tool Stormwater Home NPDES Topics Alphabetical Index Glossary About NPDES Rainfall Erosivity Factor Calculator for Small Construction Sites Facility Information Facility Name: 2320 PZ Reach 1 Start Date: 05/01/2011 End Date: 02/01/2012 Latitude: Longitutde: Erosivity Index Calculator Results AN EROSIVITY INDEX VALUE OF HAS BEEN DETERMINED FOR THE CONSTRUCTION PERIOD OF 05/01/ /01/2012. Stormwater Information Recent Additions FAQs Publications Regulations Training & Meetings Links Contacts A rainfall erosivity factor of 5.0 or greater has been calculated for your site and period of construction. You do not qualify for a waiver from NPDES permitting requirements. Start Over The documents on this site are best viewed with Acrobat 8.0 Office of Water Office of Wastewater Management Disclaimer Search EPA EPA Home Privacy and Security tice Contact Us Last updated on August 07, :37 PM URL:

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4 Appendix 1 Soil Erodibility Factor (K) The K factor can be determined by using the nomograph method, which requires that a particle size analysis (ASTM D-422) be done to determine the percentages of sand, very fine sand, silt and clay. Use the figure below to determine appropriate K value. Erickson triangular nomograph used to estimate soil erodibility (K) factor. The figure above is the USDA nomograph used to determine the K factor for a soil, based on its texture (% silt plus very fine sand, % sand, % organic matter, soil structure, and permeability). mograph from Erickson 1977 as referenced in Goldman et. al., DWQ 6 September 2, 2009

5 RUSLE - an online soil erosion assessment tool Page 1 of 1 10/29/2010 > Home > About RUSLE > Erosion Factors > Calculate Erosion > Resources > Contact Us > Acknowledgement LS Table for Construction Sites The following table shows LS factors for freshly prepared constructed and other highly disturbed soil condition with little or no cover (not applicable to thawing soil) Slope (%) Slope Length (ft.) < (From: USDA Agricultural Handbook. 703). Copyright 2002 Institute of Water Research, Michigan State University

6 Appendix 1 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. B) K Factor (weighted average, by area, for all site soils) R Factor Value 0 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 C) LS Factor (weighted average, by area, for all slopes) K Factor Value 0 The effect of topography on erosion is accounted for by the LS factor, which combines the effects of a hillslopelength 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 0 Watershed Erosion Estimate (=RxKxLS) in tons/acre 0 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 DWQ 2 September 2, 2009

7 Table 3-1 BENEFICIAL USES - Continued LAKES AND RESERVOIRS BENEFICIAL USE Hydrologic Unit Primary Secondary EST SPWN RARE WILD BIOL COLD LWRM WARM COMM REC2 REC1 POW NAV GWR PROC IND AGR MUN UPPER SANTA ANA RIVER BASIN Baldwin Lake + I I I I I I I Big Bear Lake X X X X X X X X X Erwin Lake X X X X X X X Evans, Lake + X X X X X Jenks Lake X X X X X X X Lee Lake + X X X X X X X Mathews, Lake X X X X X X 5 X X X X Mockingbird Reservoir + X X 6 X X X rconian, Lake + X X X X LOWER SANTA ANA RIVER BASIN Anaheim Lake + X X X X X Irvine Lake (Santiago Reservoir) X X X X X X Laguna, Lambert, Peters Canyon, Rattlesnake, Sand Canyon, and Siphon Reservoirs + X X 7 X X X X Present or Potential Beneficial Use 5 Access prohibited by the Metropolitan Water District. I Intermittent Beneficial Use 6 Access prohibited by the Gage Canal Company (owner-operator) + Excepted from MUN (see text) 7 Access prohibited by the Irvine Company and/or the Irvine Ranch Water District BENEFICIAL USES 3-36 January 24, 1995 Updated February 2008

8 Appendix 1 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) or has a USEPA approved TMDL implementation plan for sediment?: 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? High DWQ 4 September 2, 2009

9 ATTACHMENT A.1 LUP Project Area or Project Section Area Type Determination ATTACHMENT A.1 Will 70% of the construction activity occur on paved surfaces**? Will areas disturbed be returned to preconstruction conditions or equivalent condition* at the end of the day? Will the construction activity occur on unpaved improved roads, including their shoulders or land immediately adjacent to them? Will > 30% of the construction activity occur within the non-paved shoulders or land immediately adjacent to paved surfaces? This is a Project Type 1 LUP Will areas disturbed be returned to preconstruction conditions or equivalent condition* at the end of the day? E Will areas of established vegetation disturbed by the construction be stabilized and revegetated by the end of the project? When required, will adequate temporary stabilization BMPs be installed and maintained until vegetation is established to meet the Permit s minimum cover requirements for final stabilization? *See Definition of Terms ** Or: Will < 30% of the soil disturbance occur on unpaved surfaces? DWQ 1 September 2, 2009

10 ATTACHMENT A.1 E ATTACHMENT A.1 LUP Project Area or Project Section Area Type Determination Is the project area or project section area located within a Sediment Sensitive Watershed*? Is the project area or section located within the flood plain or flood prone area (riparian zone) of a Sensitive Receiving Water Body*? Receiving Water Risk: HIGH Receiving Water Risk: MEDIUM Receiving Water Risk: LOW Calculate the Sediment Risk Based on the Attachment C Risk Factor Worksheet Project Sediment Risk = LOW : <15 tons/acre MEDIUM : 15 and < 75 tons/acre; or HIGH : 75 tons/acre * See Definition of Terms RECEIVING WATER RISK PROJECT SEDIMENT RISK LOW MEDIUM HIGH LOW Type 1 Type 1 Type 2 MEDIUM Type 1 Type 2 Type 3 HIGH Type 2 Type 3 Type DWQ 2 September 2, 2009

11 ATTACHMENT A.1 Definition of Terms ATTACHMENT A.1 1. Equivalent Condition Means disturbed soils such as those from trench excavation are required to be hauled away, backfilled into the trench, and/or covered (e.g., metal plates, pavement, plastic covers over spoil piles) at the end of the construction day. 2. Linear Construction Activity Linear construction activity consists of underground/ overhead facilities that typically include, but are not limited to, any conveyance, pipe or pipeline for the transportation of any gaseous, liquid (including water, wastewater for domestic municipal services), liquescent, or slurry substance; any cable line or wire for the transmission of electrical energy; any cable line or wire for communications (e.g., telephone, telegraph, radio or television messages); and associated ancillary facilities. Construction activities associated with LUPs include, but are not limited to those activities necessary for the installation of underground and overhead linear facilities (e.g., conduits, substructures, pipelines, towers, poles, cables, wires, connectors, switching, regulating and transforming equipment and associated ancillary facilities) and include, but are not limited to, underground utility mark-out, potholing, concrete and asphalt cutting and removal, trenching, excavation, boring and drilling, access road and pole/ tower pad and cable/ wire pull station, substation construction, substructure installation, construction of tower footings and/or foundations, pole and tower installations, pipeline installations, welding, concrete and/or pavement repair or replacement, and stockpile/ borrow locations. 3. Sediment Sensitive Receiving Water Body Defined as a water body segment that is listed on EPA s approved CWA 303(d) list for sedimentation/siltation, turbidity, or is designated with beneficial uses of SPAWN, MIGRATORY, and COLD. 4. Sediment Sensitive Watershed Defined as a watershed draining into a receiving water body listed on EPA s approved CWA 303(d) list for sedimentation/siltation, turbidity, or a water body designated with beneficial uses of SPAWN, MIGRATORY, and COLD DWQ 3 September 2, 2009