[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"doc-seo-178009-105":3,"detail-sidebar-cat-1-en-105":81,"doc-detail-178009-en":127},{"code":4,"msg":5,"data":6},0,"ok",{"site_id":7,"language":8,"slug":9,"title":10,"keywords":11,"description":12,"schema_data":13,"social_meta":74,"head_meta":76,"extra_data":78,"updated_unix":80},105,"en","mrc-addressing-the-13-design-standards-5-15-2019","MRC-addressing-the-13-design-standards - 5-15-2019","","Design standards guidance for MRC (multi-stage runoff controls) specifies how to capture and manage runoff from a 1.2-inch/2-hour storm, filtered through vegetated media or treated through on-site soils or other acceptable systems, with release consistent with MRC Standard 2. It also defines allowable release rates (0.01 cfs per equivalent impervious acre), the need for routing to show compliance, internal water storage depth to promote ET/infiltration/denitrification, liner use criteria, and peak flow attenuation requirements for the 2-year/24-hour event. Licensed professionals must document compliance in the PCSM Report.",{"@graph":14,"@context":73},[15,34,56],{"@type":16,"itemListElement":17},"BreadcrumbList",[18,23,27,31],{"item":19,"name":20,"@type":21,"position":22},"https://docshare.wps.com","Home","ListItem",1,{"item":24,"name":25,"@type":21,"position":26},"https://docshare.wps.com/template/","Template",2,{"item":28,"name":29,"@type":21,"position":30},"https://docshare.wps.com/template/paper-templates/","Paper Templates",3,{"item":32,"name":10,"@type":21,"position":33},"https://docshare.wps.com/template/mrc-addressing-the-13-design-standards-5-15-2019/178009/",4,{"url":32,"name":10,"@type":35,"image":36,"author":41,"headline":10,"publisher":44,"fileFormat":47,"inLanguage":8,"description":12,"dateModified":48,"datePublished":49,"encodingFormat":47,"isAccessibleForFree":50,"interactionStatistic":51},"DigitalDocument",{"url":37,"@type":38,"width":39,"height":40},"https://docshare.wps.com/thumbnails/mrc-addressing-the-13-design-standards-5-15-2019/178009.png","ImageObject",442,249,{"name":42,"@type":43},"Oliver","Person",{"url":19,"name":45,"@type":46},"DocShare","Organization","application/vnd.openxmlformats-officedocument.wordprocessingml.document","2026-10-07","2026-09-02",true,{"@type":52,"interactionType":53,"userInteractionCount":55},"InteractionCounter",{"@type":54},"ViewAction",7,{"@type":57,"mainEntity":58},"FAQPage",[59,65,69],{"name":60,"@type":61,"acceptedAnswer":62},"How should runoff from the 1.2-inch/2-hour storm be handled in an MRC BMP?","Question",{"text":63,"@type":64},"It should be captured and managed by the MRC BMP, typically filtered through vegetated media or treated and filtered through undisturbed on-site soils or other acceptable treatment systems, then released as indicated by the referenced standard.","Answer",{"name":66,"@type":61,"acceptedAnswer":67},"What is the maximum allowable release rate for the 1.2-inch/2-hour storm?",{"text":68,"@type":64},"The MRC BMP release rate should not exceed 0.01 cfs from the equivalent impervious area. Compliance requires determining the runoff volume for the event and routing to demonstrate adherence to the release-rate standard.",{"name":70,"@type":61,"acceptedAnswer":71},"What are the internal water storage (IWS) and liner requirements?",{"text":72,"@type":64},"Provide IWS at least one foot deep below the lowest structural outlet to encourage ET, infiltration, and denitrification, with overall soil media depth not exceeding four feet. An impervious liner should not be installed unless environmental or geological conditions require it or an existing structure would be damaged without lining.","https://schema.org",{"og:url":32,"og:type":75,"og:title":10,"og:site_name":45,"og:description":12},"article",{"robots":77,"canonical":32},"index,follow",{"doc_id":79,"site_id":7},178009,1790292563,{"code":4,"msg":82,"data":83},"success",[84,89,94,99,104,109,114,119,123],{"id":85,"doc_module":22,"doc_module_name":25,"category_name":86,"show_sort_weight":87,"slug":88},11,"Presentations",90,"presentations",{"id":90,"doc_module":22,"doc_module_name":25,"category_name":91,"show_sort_weight":92,"slug":93},12,"Resumes",80,"resumes",{"id":95,"doc_module":22,"doc_module_name":25,"category_name":96,"show_sort_weight":97,"slug":98},14,"Invoices",70,"invoices",{"id":100,"doc_module":22,"doc_module_name":25,"category_name":101,"show_sort_weight":102,"slug":103},15,"Posters",60,"posters",{"id":105,"doc_module":22,"doc_module_name":25,"category_name":106,"show_sort_weight":107,"slug":108},16,"Social Media",50,"social-media",{"id":110,"doc_module":22,"doc_module_name":25,"category_name":111,"show_sort_weight":112,"slug":113},17,"Forms",40,"forms",{"id":115,"doc_module":22,"doc_module_name":25,"category_name":116,"show_sort_weight":117,"slug":118},18,"Letters",30,"letters",{"id":120,"doc_module":22,"doc_module_name":25,"category_name":29,"show_sort_weight":121,"slug":122},21,5,"papers-templates",{"id":124,"doc_module":22,"doc_module_name":25,"category_name":125,"show_sort_weight":4,"slug":126},158,"General","general-158",{"code":4,"msg":82,"data":128},{"doc_id":79,"user_id":129,"nickname":42,"user_avatar":130,"doc_module":22,"category_id":120,"category_name":29,"doc_title":10,"doc_description":12,"doc_content":131,"file_id":132,"file_url":133,"file_type":134,"file_size":135,"view_count":55,"is_deleted":4,"is_public":22,"is_downloadable":22,"audit_status":22,"page_count":136,"language":137,"language_code":8,"site_id":7,"html_lang":8,"table_of_contents":138,"faqs":139,"seo_title":140,"seo_description":12,"update_tm":141,"read_time":33},8796095461610,"https://ap-avatar.wpscdn.com/davatar_276721f389ce27ea32af1340a28f341c","Runoff Capture – The runoff from the 1.2-inch/2-hour storm from the contributing watershed that the MRC is intended to treat should be captured and managed by the MRC BMP, filtered through vegetated media or treated and filtered to the extent practicable through the on-site undisturbed soils or other acceptable treatment systems, and released as indicated in MRC Standard 2. The MRC may be designed for offsetting when contributing non-regulated earth disturbance is present in the contributing drainage area, but the total volume managed may not exceed the volume of runoff generated in the 2-year/24-hour storm.  Uncompacted pervious surfaces outside the disturbed area should be bypassed to the maximum extent practical.\nNOTE – Runoff from existing similar impervious and compacted pervious areas can be used to offset undetained areas. The runoff volume for the 1.2 inch/2-hour storm from the two areas must be equivalent (See Figure 4).   In addition, the pollutant contribution as determined through land use of the two areas should be similar.\nIn the space below, the licensed professional should document and demonstrate how this design standard was specifically addressed in the PCSM Report (Narrative, Calculations, H&H Model, etc.).\n\u0003Click here to enter text.\u0004\nIn the space below, the licensed professional should provide the cross reference (i.e. page number) to the specific location in the PCSM Report that addresses this design standard.\n\u0003Click here to enter text.\u0004\nRelease Rate for the 1.2-inch/2-hour storm – The stormwater release rate from the MRC BMP for the 1.2inch/2-hour storm should not exceed 0.01 cubic feet per second (cfs) from the equivalent impervious area.  To obtain the equivalent impervious area being managed by a MRC BMP, determine the total volume of runoff generated during the 1.2-inch/2-hour event from all pervious and impervious areas contributing to the MRC and divide by 0.0833 feet. This release rate is rounded to the nearest hundredth of a cfs (e.g., 1.576 ac. is 0.01576 cfs, rounded to 0.02 cfs).  Routing is necessary to demonstrate compliance with the standard for release rate.\nNOTE – This release rate (0.01 cfs / equivalent impervious acre) is approximately the expected rate of interflow (lateral movement of stormwater to a stream) after a 2-year/24-hour storm event for a Pennsylvania non-karst watershed based on the NRCS curvilinear unit hydrograph. Releasing at this rate will produce a condition where baseflow contributions will be similar to that of an undeveloped area during and after storm events. As the level of outflow would be similar to what would be expected during and after the storm, it would not be expected to impact the storm event’s effects on flooding and erosion.  This rate should also be used for karst watersheds unless it can be demonstrated that interflow on a particular project site differs from this standard (such a demonstration would be considered an alternative to the MRC Design Standard).\nIn the space below, the licensed professional should document and demonstrate how this design standard was specifically addressed in the PCSM Report (Narrative, Calculations, H&H Model, etc.).\n\u0003Click here to enter text.\u0004\nIn the space below, the licensed professional should provide the cross reference (i.e. page number) to the specific location in the PCSM Report that addresses this design standard.\n\u0003Click here to enter text.\u0004\nInternal Water Storage (IWS) – A volume for IWS should be provided that is at least one foot deep below the lowest structural outlet (i.e. the outlet for the underdrain) in the MRC BMP to encourage ET, infiltration and denitrification.  To encourage ET, the overall soil media depth of a facility including the IWS can be no deeper than four (4) feet, and up to 50% of the IWS void volume can be included (only for vegetated MRC BMPs) as available storage during hydrologic routings to demonstrate compliance with the standards for the release rate (No. 2 above) and peak flow attenua","cbCairV2YS5nnjHR","https://ap.wps.com/l/cbCairV2YS5nnjHR","docx",38759,10,"English","# Runoff capture and release\n## Runoff capture requirements\n## Stormwater release rate (1.2-inch/2-hour)\n# Internal water storage and routing\n## Internal water storage (IWS)\n## Use of liners\n# Peak flow attenuation\n## Peak flow back to pre-construction level","[{\"question\":\"How should runoff from the 1.2-inch/2-hour storm be handled in an MRC BMP?\",\"answer\":\"It should be captured and managed by the MRC BMP, typically filtered through vegetated media or treated and filtered through undisturbed on-site soils or other acceptable treatment systems, then released as indicated by the referenced standard.\"},{\"question\":\"What is the maximum allowable release rate for the 1.2-inch/2-hour storm?\",\"answer\":\"The MRC BMP release rate should not exceed 0.01 cfs from the equivalent impervious area. Compliance requires determining the runoff volume for the event and routing to demonstrate adherence to the release-rate standard.\"},{\"question\":\"What are the internal water storage (IWS) and liner requirements?\",\"answer\":\"Provide IWS at least one foot deep below the lowest structural outlet to encourage ET, infiltration, and denitrification, with overall soil media depth not exceeding four feet. An impervious liner should not be installed unless environmental or geological conditions require it or an existing structure would be damaged without lining.\"}]","MRC-addressing-the-13-design-standards - 5-15-2019 | DOCX",1788330080]