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HomeMy WebLinkAboutCouncil Reading File - 13267 Letter June 13, 2016 Derek Johnson VIA ELECTRONIC MAIL AND CERTIFIED MAIL City of San Luis Obispo Certified Mail No. 7015 0640 0001 9856 0969 990 Palm Street San Luis Obispo, CA 93401 Email: djohnson@slocity.org Dear Mr. Derek Johnson: WATER CODE SECTION 13267 TECHNICAL REPORT ORDER, ACTIVITIES TO DETERMINE STORMWATER PROGRAM MODIFICATIONS, PHASE II MUNICIPAL STORMWATER MANAGEMENT PROGRAM This letter requires traditional Central Coast Municipal Separate Storm Sewer Systems (MS4s), enrolled under the Phase II Municipal Stormwater Permit (Permit),1 to provide reports to the Central Coast Regional Water Quality Control Board. The Permit required Permittees to submit Program Effectiveness Assessment and Improvement Plans (PEAIPs) by October 15, 2015. Central Coast Water Board staff reviewed the submitted PEAIPs. In order to find Permittees in compliance with the requirement to submit adequate PEAIPs that sufficiently assess stormwater pollutant load reductions, and to ensure Permittees can develop a meaningful Stormwater Program Modifications Fifth Year Report (pursuant to Permit Provision E.14.b), Central Coast Water Board staff issues this letter requiring Permittees to report on implementation progress of completing key activities relating to spatially-based stormwater volume and pollutant loading estimates. Spatially-based Stormwater Volume and Pollutant Loading Estimates Provision E.14 of the Permit makes clear that the Stormwater Program Modifications Fifth Year Report must include: 1) an assessment of Best Management Practice (BMP) performance, 2) an estimation of stormwater volume and pollutant loading, and 3) a prioritization process for allocating program resources. These three elements are most effectively completed at the urban subwatershed, or catchment scale. In July of 2014, Central Coast Water Board staff provided minimum expectations to Permittees on preparing PEAIPs to achieve compliance with Permit Section E.14. Those expectations included these three elements and communicated the imperative of completing them on a catchment scale. Upon review of the Central Coast Permittees’ PEAIPs, Central Coast Water Board staff concluded the wide range of Permittees’ commitments to conducting effectiveness assessment 1 State Water Resources Control Board Water Quality Order No. 2013-0001-DWQ, National Pollutant Discharge Elimination System (NPDES) General Permit No. Cas000004, Waste Discharge Requirements for Storm Water Discharges From Small Municipal Separate Storm Sewer Systems (Permit). Traditional Phase II Permittees June 13, 2016 - 2 - necessitated both additional guidance and clarification to support Permittees’ compliance with Permit Section E.14. In coordination with Central Coast Water Board staff, the Central Coast Low Impact Development Initiative developed guidance, included in a Technical Memo, outlining a framework for Catchment Scale Stormwater Volume and Pollutant Loading Analyses. The Technical Memo articulates how pollutant loading information plays an essential role informing stormwater program modifications. On May 6, 2016, via email, Central Coast Water Board staff informed Central Coast stormwater program interested parties of the Technical Memo posted to the Central Coast Low Impact Development Initiative’s website: http://www.centralcoastlidi.org/mspap.php. To further clarify Central Coast Water Board expectations for completing the Stormwater Program Modifications Fifth Year Report (due October 15, 2018), this letter requires Permittees to submit information documenting progress on key activities relating to completing spatially- based stormwater volume and pollutant loading estimates. Permittees shall submit Technical Reports outlined in Table 1 documenting progress on these activities. Pursuant to Water Code Section 132672, the Permittee is hereby required to provide Technical Reports by the due dates identified in Table 1. Table 1 – Reporting Requirements for Activities to Support Development of Stormwater Program Modifications Fifth Year Report: Activity Description Due Date Report #1 Catchment Delineation and Relevant Attributes Catchment delineation, of the Permittee’s entire Permit coverage area, to sufficiently support catchment scale stormwater volume and pollutant loading analysis. The map(s) shall at a minimum include the attributes specified in Component No. 1 [The Spatial Framework] of Attachment 1 [Fundamental Components of a Municipal Catchment Scale Stormwater Volume and Pollutant Loading Analysis]. August 12, 2016 Report #2 BMP Inventory At a minimum, choose one of the below options for creating and populating an inventory of structural BMPs located within the Permittee’s Permit coverage area. 1. Inventory Option 1 – a. Create an inventory of the following structural BMPs, whose pollutant reduction capacity can be reasonably quantified and that contribute to reductions of stormwater volume and pollutant loading: i. Centralized BMPs3 (including publically and privately owned); and June 30, 2017 2 Water Code section 13267, subdivision (b), allows the Water Boards to conduct investigations and to require technical or monitoring reports from any person who has discharged, discharges, or is suspected of having discharged or discharging, or who proposes to discharge waste in accordance with the conditions in the section. 3 Centralized BMPs – One of two structural BMP categories designed to reduce urban stormwater volumes and/or pollutant concentrations generated from a mixed land use (e.g., residential, commercial, industrial, roads) catchment. (footnote continued on next page) Traditional Phase II Permittees June 13, 2016 - 3 - ii. Decentralized BMPs4 (including, at a minimum, publically owned). Catch basin assessment is optional. b. At a minimum, the Permittee shall populate the following attributes for each inventoried BMP: i. Location ii. Identifier iii. Type iv. Catchment name v. Public or privately owned vi. Land use(s) of contributing drainage area vii. Tributary area of contributing drainage area viii. Relevant treatment and/or retention capacity information. 2. Inventory Option 2 – The Permittee may conduct an alternate approach for inventorying BMPs, so long as the Permittee can demonstrate its approach yields equivalent or more meaningful data for informing the Stormwater Program Modifications Fifth Year Report than Option 1 above. The Permittee shall obtain Central Coast Water Board Executive Officer approval prior to pursuing Option 2. Data Management: Permittee shall manage BMP inventory within an information management system/database. Provide Central Coast Water Board staff access to the Permittee’s information management system/database. Stormwater Volume and Pollutant Loading – Unmitigated Condition Stormwater volume5 and pollutant loading estimates for all catchments under an unmitigated scenario (i.e., pollutant loading estimates assuming no BMPs) that provides a starting point for comparing loading estimates once BMPs (both existing and future) are included. Permittee shall use a catchment scale load modeling approach for quantifying average annual stormwater discharge and pollutant loading from all municipal catchments to the designated receiving waters. The approach shall be technically defensible and (footnote continued from previous page) The contributing drainage areas typically exceed one acre of impervious area. Examples of centralized BMPs include dry basins, detention basins, wet basins, infiltration basins, treatment vaults, media filters, and bed filters. 4 Decentralized BMPs – One of two structural BMP categories designed to reduce urban stormwater volumes and/or pollutant concentrations generated from a single land use. The contributing drainage areas are typically less than one acre of impervious area. Examples of decentralized BMPs include infiltration features, bioretention, bioswales, biofiltration, porous pavement, and trash capture devices. Catch basins designed to capture material through variable flow modifications or passive settling, that result in vertical accumulation of material at base of BMP reservoir, are also decentralized BMPs. 5 This letter requires Permittees to obtain stormwater volume estimates because, in addition to volume being a relevant proxy for the range of urban pollutants, stormwater volume estimates are necessary to calculate pollutant loading estimates. Traditional Phase II Permittees June 13, 2016 - 4 - sufficiently accurate to produce a credible relative ranking to inform program priorities and decisions. At a minimum, Permittee shall incorporate the necessary components of a catchment scale pollutant loading analysis identified in Component No. 2 [Runoff Characteristics], Component No. 3 [Computational Requirements], and Component No. 4 [Standardized Protocols] of Attachment 1. The Permittee may use an alternate approach to conducting a catchment scale stormwater volume and pollutant loading analysis for the unmitigated condition, so long as the Permittee can demonstrate its approach will result in outputs that are equally defensible to the approach identified in Attachment 1. The Permittee shall obtain Central Coast Water Board Executive Officer approval prior to pursuing an alternate approach. Catchment Ranking – Unmitigated Condition At a minimum, for the unmitigated condition, the Permittee shall submit the following relative rankings of all municipal catchments: 1. Ranking based on stormwater volume – ranked from greatest potential annual stormwater volume generation to least potential annual stormwater volume generation; and 2. Ranking based on pollutant loading estimates – ranked from greatest potential annual pollutant loading to least potential annual pollutant loading. The Permittee shall conduct a separate ranking for each pollutant it has collected data for. Report #3 BMP Assessment Central Coast Water Board staff acknowledges that a comprehensive BMP assessment is a significant task; therefore, the following options are available: At a minimum, choose one of the below options for obtaining BMP performance data, based on field assessments, to inform current load reductions. 1. Assessment Option 1 – For all inventoried BMPs, using an effective approach for assessing structural BMP performance, estimate stormwater volume and pollutant load reduction based on: 1) intended BMP function; and 2) current BMP condition based on empirical data (i.e., BMPs ability to function relative to intended design). 2. Assessment Option 2 – The Permittee may conduct an alternate approach for obtaining empirical BMP condition data, based on field assessments, so long as the Permittee can demonstrate its option yields equivalent or more meaningful data for informing the Stormwater Program Modifications Fifth Year Report than Option 1 above. The Permittee shall obtain Central Coast Water Board staff approval prior to pursuing Option 2. June 30, 2018 Traditional Phase II Permittees June 13, 2016 - 5 - Data Management: Permittee shall manage BMP performance data within an information management system/database. Provide Central Coast Water Board staff access to the Permittee’s information management system/database. Stormwater Volume and Pollutant Loading – Loading Reductions Based on BMP Assessment Stormwater volume and pollutant loading estimates for selected catchments based on BMP performance assessment. Permittee shall use a catchment scale load modeling approach for quantifying average annual stormwater discharge and pollutant loading from all municipal catchments to the designated receiving waters. The approach shall be technically defensible and sufficiently accurate to produce a credible relative ranking to inform program priorities and decisions. At a minimum, Permittees shall incorporate the necessary components of a catchment scale pollutant loading analysis identified in Component No. 2, Component No. 3, and Component No. 4 of Attachment 1. The Permittee may use an alternate approach to conducting a catchment scale stormwater volume and pollutant loading analysis based on BMP performance assessment, so long as the Permittee can demonstrate its approach will result in outputs that are equally defensible to the approach identified in Attachment 1. The Permittee shall obtain Central Coast Water Board Executive Officer approval prior to pursuing an alternate approach. Catchment Ranking – Loading Reductions Based on BMP Assessment At a minimum, after accounting for reductions from implemented BMPs, the Permittee shall submit the following relative rankings of all municipal catchments: 1. Ranking based on stormwater volume – ranked from greatest potential stormwater volume generation to least potential stormwater volume generation; and 2. Ranking based on pollutant loading estimates – ranked from greatest potential pollutant loading to least potential pollutant loading. The Permittee shall conduct a separate ranking for each pollutant for which it has collected data. Report #4 Stormwater Program Modifications Fifth Year Report Using the information gained from the above activities, as well as other data and information that informs program priorities, the Permittee shall submit a report including the following components: 1. Summary of BMPs and/or program modifications to improve compliance with permit conditions and improve program effectiveness at reducing pollutant loads, achieving the maximum extent practicable, and protecting beneficial uses. The summary shall identify the following: a. Improvements to underperforming BMPs, b. Continuation of effective BMPs, and October 15, 2018 Traditional Phase II Permittees June 13, 2016 - 6 - c. Discontinuation of ineffective BMPs. 2. Priority areas for program improvements; 3. Modifications to shift priorities to make more effective use of resources; and 4. Time schedule, scope, and frequency of BMP modifications. Annual Reporting Complete the Stormwater Volume and Pollutant Loading Annual Report form found in SMARTS. Starting in October 2016, Permittees must complete this form every year for the remainder of the Permit term. The Central Coast Water Board requires the Permittee to submit the information described in this letter pursuant to Provision 9 in Attachment F of the Permit. The Central Coast Water Board reserves the right to take any enforcement action authorized by law. The Technical Reports are necessary for the Central Coast Water Board to determine the state of compliance with the Permit. The Technical Reports are also necessary to determine the potential or actual harm to human health or the environment from non-compliance. The burden, including costs of the reports, bears a reasonable relationship to the need for the reports and the benefits to be obtained from them. Failure to comply with the requirement to submit the Technical Reports required in this letter and made pursuant to Water Code section 13267, subdivision (b), may result in administrative civil liability pursuant to Water Code section 13268 up to $1,000 per day. Central Coast Water Board staff is available to work with Permittees to achieve stormwater management programs that are increasingly effective at reducing the discharge of pollutants to the maximum extent practicable and protecting water quality. If you have any questions regarding this letter, please contact Tamara Anderson at (805) 549- 3334 or at Tamara.Anderson@waterboards.ca.gov, or Dominic Roques at (805) 542-4780. Sincerely, John M. Robertson Executive Officer Traditional Phase II Permittees June 13, 2016 - 7 - Attachment 1: Fundamental Components of a Municipal Catchment Scale Stormwater Volume and Pollutant Loading Analysis cc: Freddy Otte, fotte@slocity.org R:\RB3\Shared\SW\Program\_Municipal Prog\Phase II\Program Effectiveness\June2016_13267_Order\June2016_13267_Order_final_1.docx Traditional Phase II Permittees Attachment 1: Fundamental Components of a Municipal Catchment Scale Stormwater Volume and Pollutant Loading Analysis - 8 - 1. The Spatial Framework Catchment delineations and relevant catchment attributes create the spatial framework for estimating stormwater volume and pollutant loads. a. Catchment delineations and associated areas (e.g., acres). To conduct catchment scale pollutant loading analyses, the municipality needs to be divided into spatially explicit units defined by municipal drainage catchments. The catchments are reasonable representations of actual drainage areas where stormwater discharges through an identified outfall. In the instance where many outfalls exist within a small area, drainage areas can be combined to minimize the total number of catchments mapped within the municipality. Delineating catchments of relatively similar size will be helpful when ranking and comparing catchments. A good target size for a catchment is approximately 100 acres. A catchment can possess either a single discrete discharge point (i.e., discharges either to another catchment or to a receiving water via a single outfall), or distributed discharge points to the receiving water (e.g., several small outfalls and/or sheet flow). The municipality should assign identifiers (e.g., name/label) to each catchment. Field verification of delineated catchments is encouraged. b. Catchment outfalls and determination of receiving waters to which each catchment discharges. The United State Geological Survey’s National Hydrography Dataset (USGS NHD) contains publically available surface water designations and should be used to identify receiving waters accepting stormwater from the municipal outfall. (http://nhd.usgs.gov/). The municipality should assign identifiers (e.g., name/label) to each catchment outfall. Use of more accurate local information and field verification is encouraged. c. Hydrologic connectivity for each catchment. For this analysis, hydrologic connectivity is the percentage of rainfall within a catchment that becomes stormwater runoff, and is then delivered to the receiving water. Catchments with high hydrologic connectivity are those where most of the stormwater generated within the catchment reaches the receiving water as opposed to catchments with low hydrologic connectivity where much of the stormwater runoff generated in the catchment does not reach the receiving water. Two aspects of hydrologic connectivity are used to understand the overall connectivity of the catchment to the receiving water: 1) hydrologic connectivity within the catchment to the catchment discharge point (e.g., outfall), and 2) hydrologic connectivity from the catchment discharge point to the actual receiving water. Clear guidance on how to determine hydrologic connectivity is a critical element in providing reasonable estimates of pollutant loads delivered to the receiving water from each catchment. d. Land use designations should include the following categories within each catchment and the associated impervious area (in acres): Traditional Phase II Permittees Attachment 1: Fundamental Components of a Municipal Catchment Scale Stormwater Volume and Pollutant Loading Analysis - 9 -  Single family residential  Multi-family residential  Industrial  Commercial  Cultivated  Paved Roads (high traffic density, moderate traffic density, low traffic density)  Unpaved Roads  Other (typically open space) 2. Runoff Characteristics Runoff characteristics of each catchment are used with the spatial framework to calculate stormwater volume and associated pollutant loading. Catchment precipitation, imperviousness, and soil permeability are all critical elements in estimating stormwater volume and pollutant loads. a. Precipitation. Precipitation characterization should be based on a reasonable representation of the historic range of precipitation conditions for the catchment that includes both small (common) and very large (infrequent) precipitation events to generate average annual runoff estimates. b. Imperviousness and soil permeability. The National Land Cover Database (2011; http://www.mrlc.gov/nlcd2011.php) can be used to estimate the percent of imperviousness of each land use (e.g., commercial, residential) within each catchment. Use of generic runoff coefficients based on land use type, is generally insufficient to adequately estimate stormwater runoff volumes. In addition to impervious coverage by land use, incorporation of the relative permeability and native soil retention coefficients should be used to adjust runoff generation from each land use type. c. Pollutant types for evaluation. Pollutant types selected for the loading analyses should be relevant and serve as a reasonable proxy for the range of urban pollutants. The effort should be made to base pollutant selection on characteristics including, but not limited to, primary land uses, source of pollutants, fate and transport of pollutants in stormwater, and data availability. Pollutants such as Total Suspended Solids (TSS) and stormwater volume are examples of proxies for the broader suite of pollutants in urban runoff. Alternatively, a suite of representative urban pollutants of concern (e.g., trace metals, nutrients, hydrocarbons, etc.) may be modeled. Traditional Phase II Permittees Attachment 1: Fundamental Components of a Municipal Catchment Scale Stormwater Volume and Pollutant Loading Analysis - 10 - d. Urban runoff pollutant data. Pollutant concentrations associated with various land use types are often used to calculate pollutant loads. Existing urban pollutant models employ a wide array of approaches to generate these pollutant concentrations. The objective in selecting land use pollutant concentrations is to choose values that adequately reflect the conditions being modeled without being overly concerned with the need for absolute accuracy. There is an abundance of credible urban stormwater quality data available online that can be used to estimate pollutant concentrations by urban land use type. The analysis should consistently apply the selected data to all catchments and BMP performance estimates to ensure results are directly comparable among catchments. e. Pollutant reduction estimates resulting from stormwater program actions. Pollutant reduction estimates should be based on BMPs whose pollutant reduction capacity can be reasonably quantified. Additionally, reduction estimates should be based on an assessment of actual BMP performance. Methods to assess and quantify actual BMP performance include direct measurements of pollutant removal such as conventional water quality input/output monitoring of a BMP or weighing of sediment collected from street sweeping activities; and, indirect measurements such as field observations that serve as credible proxies for BMP performance and pollutant load reduction effectiveness. “Desktop” quantification of pollutant reduction that assumes structural BMPs are performing as designed may not be accurate since the actual constructed project and/or the maintenance condition of the BMP affects actual water quality performance. 3. Computational Requirements The computational tool (i.e., model) provides the ability to generate loading estimates and other required outputs. Selection or development of the model requires consideration of all desired outputs including data, tables, figures, and reports. a. Ability to estimate average annual stormwater volume and pollutant loads delivered from each catchment to the receiving water in a manner that is reliable, repeatable, and allows for comparison of results among catchments and over time. b. Ability to estimate average annual stormwater volume and pollutant load reductions as a result of BMP implementation and performance by catchment in a manner that is reliable, repeatable and comparable among catchments and over time. c. Ability to track and compare data on a spatial (single or multiple catchments) and temporal (year to year) basis. d. Ability to generate output in the desired reporting format(s). Traditional Phase II Permittees Attachment 1: Fundamental Components of a Municipal Catchment Scale Stormwater Volume and Pollutant Loading Analysis - 11 - 4. Standardized Protocols Development and implementation of standardized protocols is, in some respects, one of the most import elements of the analytic approach as these protocols lend credibility to the overall analyses. a. Consistent methodology within and across each catchment. Use of a consistent methodology to estimate annual volume and pollutant load reductions should be employed to ensure the results are indicative of structural and non-structural BMP performance and not due to variation in methodology. For example, precipitation inputs driving the hydrologic analysis must be held constant between the Unmitigated Catchment scenario and any subsequent scenarios based on load reduction estimates. b. Normalization to allow comparisons among catchments. Converting stormwater volume and pollutant load into volume and load per unit area per time allows for comparison among catchments. By ranking catchments within the municipality by loading rates, (e.g., high to low), catchments with the greatest risk to receiving waters can be identified.