Office Memorandum. ta regulate discharges assaciated with canstructian activity because all constructian activity invalves. Division Director ~,

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1 DEPARTMENT: POLLUTION CONTROL AGENCY DATE: March 15, 2013 STATE OF MINNESOTA Office Memorandum Sf Q5(4/86) TO: MPCA Citizens' Board FROM: Lisa Thorvig j) -,..,~~ Division Director ~, Municipal PHONE: Division SUBJECT: Construction Stormwater NPDES/SDSGeneral Permit Reissuance The purpase.of this memarandum is ta pravide Minnesata Pallutian Cantrol Agency (MPCA) Citizens' Baard (Baard) members with infarmatian an the MPCA's canstructian starmwater program and the draft Natianal Pallutant Discharge Eliminatian System/State Dispasal System (NPDES/SDS) Canstructian Starmwater (CSW) General Permit (Draft Permit) that came.off public natice an March 20, Stormwater Program Background In 1990, the U.S. Environmental Protectian Agency (EPA) promulgated rules establishing Phase I.of the NPDES starmwater pragram. Phase I addressed, amang ather discharges, discharges fram large canstructian activities disturbing 5 acres.or mare.of land. In 1999, Phase II.of the NPDES starmwater program expanded the scape.of the existing NPDES permit pragram far canstructian activities to include discharges.of starmwater fram canstruc~ian activities of.one acre.or mare. The Minnesata CSW NPDES/SDS General Permit Na. MNR100001, was geveloped ta regulate canstructian activity discharges and was first issued on September 3, 1993, then reissued every 5 years an September 4, 1998, August 1, 2003, and August 1, The current permit will expire August 1, The gaal.of the starmwater program far canstructian activity is ta pratect and imprave water quality in Minnesata's surface waters through the management and treatment.of canstructian site starmwater runaff. The primary pallutant that is treated and cantrolled under this permit is sediment. Other pallutants assaciated with canstructian activity include phaspharaus, nitrogen, bacteria, metals and inarganics, pesticides, constructian chemicals, petraleum pro~ucts and volatile.organic chemicals. This permit alsa cantrols the direct and indirect pallutian resulting from the uncantrolled discharge.of large valumes.of starmwater fram imperviaus surfaces. P,olluted starmwater cantributes ta swimming-beach c1asings, fish-eating advisaries, excess algae,grawth, and paar water clarity in water resaurces, especially lakes. Paarly managed canstructian sites can cantribute ta neighbarhaad flaading, drastically\ alter the natural flaw and infiltratian.of water, scaur stream banks, and harm.or eliminate aquatic.organisms and ecasystems. General permits are autharized under 40 CFR and Minn. R. ch The MPCA is specifically autharized ta issue a general permit ta any categary.of paint saurce starm water discharges by Minn. Stat , subd. 5c (2012). The MPCA has determined that a general permit is apprapriate ta regulate discharges assaciated with canstructian activity because all constructian activity invalves substantially similar processes that disturb and expase tapsail and that result in discharges.of sediment and potentially ather pallutants assaciated with canstructian. Canstructian activity usually canverts perviaus areas ta imperviaus areas, which results in increased valume and velacity.of runaff, causing TDD (for hearing and speech impaired only): 612: Printed on recycled paper containing at/east /O%fibersfrom paper recycled by consumers

2 MPCA Citizens Board Page 2 degradation of surface waters. Because the pollutants associated with construction activity are substantially similar regardless of the size and location of the construction activity, substantially similar standards, limitations, and operating requirements can be imposed on all construction activities subject to the permit. This Draft Permit is proposed to replace the existing NPDES/SDS General Permit No. MNR and provides a mechanism to continue to regulate construction activity discharges of stormwater pollutants associated with construction activity. Like the previous permit, this permit will require each Permittee to develop and implement a Storm Water Pollution Prevention Plan (SWPPP) in compliance with the permit prior to application submittal and to implement the SWPPP prior to conducting the construction activity. The SWPPP will address the potential for discharge of sediment and/or other potential pollutants from the construction site and will allow each Permittee to choose the appropriate Best Management Practices or BMPs to address the potential discharge of sediment and other potential pollutants from the construction site, and to control the indirect pollution and degradation of surface waters resulting from the uncontrolled discharge of volumes of stormwater from impervious surfaces. This permit is required when construction activity that results in land disturbance of equal to or greater than one acre occurs and authorizes, subject to the terms and conditions of this permit, the discharge of stormwater associated with construction activity. Construction activity includes clearing, grading, filling, and excavating. Construction activity does not include a disturbance to the land of less than five acres for the purpose of routine maintenance that is performed to maintain the original line and grade, hydraulic capacity, and original purpose of the facility. Reissuance of the Construction Stormwater General Permit Permit Changes The MPCA has modified the existing NPDES/SDS General Permit No. MNR100001, to meet new federal requirements promulgated in the (2009) Effluent Limitations Guidelines and Standards for the Construction and Development (C&D) Point Source Category Rule in the Code of Federal Regulations at 40 CFR pt The EPA C&D Rule requirements include non numeric effluent limitations that apply to all permitted discharges from construction sites (40 CFR ). These nonnumeric effluent limitations are required by EPA to be addressed in the state s issuance of NPDES stormwater permits. These EPA rule requirements include added BMP design and site considerations, buffer requirements during construction, temporary sediment basin floating discharge devices and pollution prevention considerations. While the permit must meet the requirements of the EPA C&D rule it must also meet our own state Antidegradation requirements. The draft permit revisions also address issues the MPCA identified as needing revision and/or updating in this reissuance including electronic applications, refresher training requirements, inspection requirements, and expanded permanent treatment requirements for volume control. The draft permit also includes numerous clarifications, permit language reorganization, added definitions and minor language changes to make the permit more concise, cut duplicative or unneeded language and to improve permit readability and understanding. (See the attached fact sheet titled Changes to construction stormwater permit.)

3 MPCA Citizens Board Page 3 Volume Control Permanent Treatment These modifications to the existing permit that the MPCA identified as necessary or that were required to address state requirements, including the requirements to develop design standards to promote low impact development as required by Minn. Stat , subp. 5c. The current permit requires ½ inch of runoff to be infiltrated when the project discharges to and within one mile of special or impaired waters. The permanent treatment proposal for the reissued permit requires that where a project s ultimate development replaces vegetation and/or other pervious surfaces with one or more acres of cumulative impervious surface, the Permittee(s) must design the project so that the water quality volume of one inch of runoff from the new impervious surfaces created by the project is retained on site. This can be done by the use of infiltration (except where prohibited by permit requirements) and/or by other volume reduction practices (i.e.; pervious surface reduction, evapotranspiration, water harvesting). When infiltration or volume reduction cannot account for the entire one inch to be retained on site then other standard methods must be used, such as wet sedimentation basin, filtration system, regional ponding or equivalent methods prior to the discharge of stormwater to surface waters. In the natural, undisturbed environment, precipitation is intercepted by trees and other vegetation, stored in natural depressions until evaporated, or absorbed by soils and humus on the surface of the ground. This moisture is then used by plants, recharges shallow groundwater that enters streams, lakes and wetlands, or infiltrates more deeply to recharge deeper aquifers. During most storms, very little rainfall becomes stormwater runoff. Traditional development practices, however, disrupt the water holding capacity of the natural environment. Development results in impervious surfaces such as roads, driveways, sidewalks, and buildings. Remaining soils, even those under vegetated areas, are often heavily compacted and relatively impervious. As a result, even a small rainfall event creates stormwater runoff that is carried away by curb and gutter systems. The collective force of the increased stormwater flows can scour streambeds, erode stream banks, inundate wetlands and cause large pulses of sediment and other entrained pollutants, such as metals, nutrients and trash, to enter downstream receiving waters. Research shows a high correlation between the area of impervious surface in a watershed and the degree of overall degradation of downstream water quality and aquatic habitats. (See Over the past three years, the MPCA has examined scientific research and looked at standards employed by other states and governmental units to determine what would constitute reasonable performance and design standards that would promote the implementation of low impact development that mimics a site s natural hydrology as the landscape is developed. The conclusion of this research was that treatment of about the first 1 inch of impervious surface runoff represents a volume that appears to reasonably represent the volume that is fully infiltrated in a modern day natural condition and thus should be managed onsite to restore and maintain the pre development hydrology of receiving waters. The MPCA finds that management of this volume is generally feasible, and that this requirement has been successfully implemented by various Water Management Organizations in the Twin Cities Metro Area and in many locations around the nation under a wide variety of climates and conditions. However, the MPCA recognizes that, for a particular site, a permittee may not be able to comply fully with the new requirement because of unique conditions, for example, where infiltration is prohibited or limited due to the presence of contamination or shallow bedrock, or some linear sites (roads with limited right of way). For this reason, the MPCA has provided that other permanent treatment methods, such as grassed swales,

4 MPCA Citizens Board Page 4 filtration systems, smaller ponds, or grit chambers, can be utilized prior to discharge to surface waters in lieu of infiltration. The SWPPP must document this determination. The MPCA finds that there are a number of models that developers can employ to determine whether the one inch standard is being met on the site. Because models are always under refinement, the MPCA has chosen not to require permittees to utilize a particular model to document compliance with the permit requirement. The proposed permanent stormwater management requirement to manage water on the development site is consistent with the federal effluent guidelines for stormwater management during construction. See 40 CFR (a)(1). To date, post construction stormwater management approaches generally have been focused primarily on rate controls for flood management, with a heavy reliance upon extended detention controls (i.e., collecting water short term, usually in a large basin, and discharging it to the receiving water over the period of one to several days, depending on the size of the storm) or on in pipe or end of pipe treatment systems. Extended detention approaches are intended to reduce downstream flooding to the extent necessary to protect public safety and private and public property. End of pipe systems are typically intended to provide pollutant sedimentation and filtration. However, as noted by the National Research Council in their 2008 report, these traditional stormwater treatments do not sufficiently reduce the suite of pollutants in stormwater, particularly dissolved and colloidal compounds such as phosphorus, to the extent necessary to prevent downstream degradation. Further, rate control practices generally do not address aquatic habitat degradation attributable to increased discharge volumes (stream bank erosion, incision and shock loading). Public Involvement and Public Notice of the Draft Permit A stakeholder meeting was held by the MPCA, on December 17, 2012, to provide information and gather feedback from stakeholders on the issues that needed to be addressed in the reissuance of the construction stormwater permit. The MPCA placed the draft permit on public notice for 45 days from February 4, through March 20, The MPCA also held a public information meeting on March 8, 2013, to facilitate the public in seeking clarification and understanding the draft permit. Current Status of Permit Reissuance The public notice of the draft permit ended on March 20, The MPCA is currently in the process of organizing, evaluating and responding to all comments received. Once the MPCA responds to all comments, the staff will return to the MPCA Citizens Board for a final decision on the draft permit. Attachment: Fact Sheet titled Changes to construction stormwater permit

5 Changes to construction stormwater permit MPCA re issuing general permit for construction stormwater The Minnesota Pollution Control Agency (MPCA) issues the Construction Stormwater General Permit to protect water resources from contaminants in runoff from construction sites. The MPCA issues a general permit that requires controls for construction stormwater runoff. When construction site owners and operators apply for coverage under the general permit, they agree to develop a Stormwater Pollution Prevention Plan (SWPPP) that will comply with the conditions set in the permit. The current permit expires on August 1, Because federal rules have changed since the last permit was issued in 2008, the MPCA must update the general permit to comply with these federal changes. Based on research and experience, the federal government continues to make changes to ensure that adequate best management practices (BMPs) are in place. While the primary changes concern federal rules, the MPCA is also revising the permit to modify the permanent treatment requirements; clarify and streamline existing language; better align with the municipal stormwater program; address defects; and incorporate changes needed to enhance compliance with the permit. In addition, the agency will require that permit applications be submitted electronically for greater efficiency. For a copy of the draft permit or more information, visit the construction stormwater permit page linked from Federal Construction and Development rules Stormwater controls help protect lakes and streams from sediment and other pollutants. In December 2009, the U.S. Environmental Protection Agency (EPA) proposed a numeric effluent limitation in its Construction and Development rule (40 CFR pt. 450) for runoff from construction sites. The numeric limit was based on the allowable level of turbidity, which is a measure of sediment in water runoff from a construction site. Originally, the Construction and Development rule also required monitoring runoff from the site by collecting samples to test whether the site was complying with the limit. However, due to problems identified with the data used to calculate the numeric limit, the EPA delayed these requirements until new data are available. Therefore, there will be no numeric turbidity limit or monitoring and reporting requirements for turbidity in the MPCA 2013 general permit. However, the MPCA is required to address certain enhanced Best Management Practices (BMPs) known as non numeric effluent limitations in order to prevent the mobilization of sediment and limit the generation of dissolved pollutants from construction sites. For more information on the Construction and Development requirements, visit the EPA website: Minnesota Pollution Control Agency TTY or March 2013 Available in alternative formats

6 New requirements in draft general permit To comply with the federal Construction and Development rule, the MPCA plans to address the new requirements in the Minnesota 2013 general permit as follows. Site considerations during construction Maintain a 50 foot natural buffer or use redundant sediment controls near surface waters if a buffer is not feasible. Control flow rates and the total stormwater volume from the site to minimize downstream impacts. Use conveyance channels to route water around unstabilized areas, including erosion controls and velocity dissipation devices to limit potential for erosion. Direct discharges from stormwater controls to vegetated areas and use velocity devices if necessary to prevent erosion. Minimize the disturbance of slopes 3:1 or steeper. Initiate soil stabilization immediately by taking action as soon as practicable, but no later than the end of the next work day when earth disturbing activities will cease for at least 14 days. Minimize soil compaction and preserve topsoil at the site. Temporary sediment basins outlet structure must be designed to withdraw water from the surface. Sediment basins must be located outside of any natural buffers. Design of stormwater controls The BMPs in the SWPPP include requirements to control both peak flow rates and total stormwater volume at basin outlets and other water channelized from the site to minimize downstream channel and streambank erosion. Therefore, factors to be considered in design of controls include: o Stormwater runoff and run on at the site. o Expected flow from impervious surfaces, slopes and site drainage features. o The expected amount, frequency, intensity and duration of precipitation. The SWPPP will also need to address the range of soil particle sizes expected at the site. Pollution Prevention (P2) measures All potential pollution generating activity locations, such as chemical storage, washout activities, fueling areas, etc. will need to be shown on the SWPPP site map. Storage areas for potential pollutants on the site, such as building materials, hazardous products or materials, soaps, detergents, wastes, etc. must minimize exposure to stormwater. All liquid and solid wastes generated by washout operations (concrete, stucco, form release oils, curing compounds, and others) at the site must be contained for treatment or proper disposal. The SWPPP must have a fueling operation plan and emergency spill plan. Natural vegetative buffer helps filter sediment from runoff. Portable toilets on the site must be secured and sanitary waste must be properly disposed of. Page 2 of 3

7 Additional changes The MPCA is also considering changes to improve permanent stormwater treatment to address state anti degradation requirements, clarify existing language, remove redundancy, and enhance compliance with the permit. Notable changes include the following: That all permit applications are submitted electronically with permit coverage within 7 days. That trained individuals attend refresher training every 3 years. Site inspection requirements, including site inspections after a rainfall event greater than ¼ inch (rather than the current ½ inch) in 24 hours. That 1 inch of stormwater runoff from new impervious will be held on site via infiltration, harvesting or reuse, unless prohibited. That chemicals used for purposes of flocculation will be documented in the SWPPP and that a chemical treatment plan will be included for the site. That filter backwash waters are properly disposed of or returned to the beginning of the treatment process, and that filter media at the site are maintained and cleaned. That soils are stabilized within 24 hours for activities that are adjacent to and drain to Public Waters (as designated by the Minnesota Dept. of Natural Resources) with work restrictions during fish spawning times. The permit will allow projects located in an NPDES permitted MS4 community to follow the current MS4 permit permanent treatment requirements. The previous permit requirement for a DNR approval letter for discharges to calcareous fens was deleted from the draft permit and Appendix A BMPs applied. Important dates March 8, 2013: Public notice meeting at 9:00 a.m., in the MPCA Citizens' Board Room, lower level, 520 Lafayette Road North St. Paul, Minnesota. This meeting will be webcast: March 20, 2013: Deadline to submit comments on draft Construction Stormwater General Permit. Interested persons are invited to submit written comments on the draft permit. Any comments received before 4:30 p.m. on March 20, 2013, of the comment period will be considered before the draft permit is finalized. March 26, 2013: MPCA staff members are scheduled to present the draft Construction Stormwater General Permit as an informational item to the MPCA Citizens' Board meeting. This meeting will be webcast. May 28, 2013: MPCA staff plan are tentatively scheduled to ask the MPCA Citizens' Board to approve the draft Construction Stormwater General Permit at this meeting, which will be webcast. August 1, 2013: Current permit expires. Deadline for re issuing updated permit. Contacts One way to hold stormwater on-site is to store it in cisterns for later use as irrigation. Lawrence Zdon, , Lead Permit Writer and technical questions. Comments, which must be in writing, should be submitted by 4:30 p.m. March 20, 2013, to Lawrence Zdon at lawrence.zdon@state.mn.us or 520 Lafayette Road North St. Paul, Minnesota Brian Livingston, , Supervisor, MPCA Stormwater Program, brian.livingston@state.mn.us. March 2013 Page 3