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[[File: Preserver Photo 1.JPG|thumb|300 px|alt=image of Preserver pretreatment device|<font size=3>Heavy Leaf and Debris Loading in Pretreatment Manhole Sump [Ramsey Conservation District, 2017]. </font size>]] | [[File: Preserver Photo 1.JPG|thumb|300 px|alt=image of Preserver pretreatment device|<font size=3>Heavy Leaf and Debris Loading in Pretreatment Manhole Sump [Ramsey Conservation District, 2017]. </font size>]] | ||
{{alert|The Minnesota Pollution Agency (MPCA) received a request to provide information on management and disposal of sediments collected by pretreatment practices. We conducted a cursory review of the literature and developed this page. In developing this page, the MPCA is not providing recommendations for managing sediment and other materials captured by stormwater pretreatment practices. This page provides guidance and general information that can be used for managing these materials.|alert-warning}} | {{alert|The Minnesota Pollution Agency (MPCA) received a request to provide information on management and disposal of sediments collected by pretreatment practices. We conducted a cursory review of the literature and developed this page. In developing this page, the MPCA is not providing recommendations for managing sediment and other materials captured by stormwater pretreatment practices. This page provides guidance and general information that can be used for managing these materials.|alert-warning}} | ||
+ | {{alert|Though street sweeping is not included with other pretreatment practices in this manual, information on street sweepings is included on this page since the material collected by sweepers is likely to be similar to material captured by pretreatment practices.|alert-info}} | ||
This discussion focuses on <span title="Pretreatment reduces maintenance and prolongs the lifespan of by removing trash, debris, organic materials, coarse sediments, and associated pollutants prior to entering structural stormwater BMPs. Implementing pretreatment devices also improves aesthetics by capturing debris in focused or hidden areas. Pretreatment practices include settling devices, screens, and pretreatment vegetated filter strips."> [https://stormwater.pca.state.mn.us/index.php?title=Pretreatment '''pretreatment''']</span> practices. Pretreatment reduces maintenance and prolongs the lifespan of <span title="a stationary and permanent BMP that is designed, constructed and operated to prevent or reduce the discharge of pollutants in stormwater"> '''structural stormwater BMPs'''</span> by removing trash, debris, organic materials, coarse sediments, and associated pollutants prior to entering structural stormwater BMPs. Implementing pretreatment devices also improves aesthetics by capturing debris in focused or hidden areas. | This discussion focuses on <span title="Pretreatment reduces maintenance and prolongs the lifespan of by removing trash, debris, organic materials, coarse sediments, and associated pollutants prior to entering structural stormwater BMPs. Implementing pretreatment devices also improves aesthetics by capturing debris in focused or hidden areas. Pretreatment practices include settling devices, screens, and pretreatment vegetated filter strips."> [https://stormwater.pca.state.mn.us/index.php?title=Pretreatment '''pretreatment''']</span> practices. Pretreatment reduces maintenance and prolongs the lifespan of <span title="a stationary and permanent BMP that is designed, constructed and operated to prevent or reduce the discharge of pollutants in stormwater"> '''structural stormwater BMPs'''</span> by removing trash, debris, organic materials, coarse sediments, and associated pollutants prior to entering structural stormwater BMPs. Implementing pretreatment devices also improves aesthetics by capturing debris in focused or hidden areas. | ||
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==Monitoring results== | ==Monitoring results== | ||
+ | [[File:St Cloud sweeping debris.png|300px|thumb|alt=photo street sweeping debris|<font size=3>Photos of street sweeping debris. Top - prior to screening. Center - screening. Bottom - after screening (foreground and background). Photos courtesy St. Cloud, Minnesota.</font size>]] | ||
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There is limited information for sampling of sediments and other materials captured by pretreatment practices. The Excel spreadsheet below summarizes results from sampling studies. '''NOTE''': This spreadsheet may be updated periodically and includes a date at the top of the spreadsheet. | There is limited information for sampling of sediments and other materials captured by pretreatment practices. The Excel spreadsheet below summarizes results from sampling studies. '''NOTE''': This spreadsheet may be updated periodically and includes a date at the top of the spreadsheet. | ||
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*[https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=2ahUKEwiw7MWMz_jhAhUIlawKHSQTD5oQFjABegQIBBAC&url=https%3A%2F%2Frosap.ntl.bts.gov%2Fview%2Fdot%2F19525%2Fdot_19525_DS1.pdf%3F&usg=AOvVaw2YVEIn2s9ktI2uiiX-lf0B Yu and Stopinski, 2001] | *[https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=2ahUKEwiw7MWMz_jhAhUIlawKHSQTD5oQFjABegQIBBAC&url=https%3A%2F%2Frosap.ntl.bts.gov%2Fview%2Fdot%2F19525%2Fdot_19525_DS1.pdf%3F&usg=AOvVaw2YVEIn2s9ktI2uiiX-lf0B Yu and Stopinski, 2001] | ||
**Concentrations of metals other than chromium were below criteria for Isolator and Stormceptor pretreatment devices. '''NOTE''': the criteria for hexavalent chromium was used in this analysis | **Concentrations of metals other than chromium were below criteria for Isolator and Stormceptor pretreatment devices. '''NOTE''': the criteria for hexavalent chromium was used in this analysis | ||
+ | *City of Lakeville, Minnesota - street sweepings | ||
+ | **Concentrations of RCRA metals were below residential soil reference values | ||
+ | **No detections of metals for TCLP analysis | ||
+ | **DRO (diesel range organics) concentration (175 mg/kg) exceeded site screening criteria (10 mg/kg) | ||
+ | *Village of St. Anthony, Minnesota - street sweepings | ||
+ | **Concentrations of RCRA metals were below residential soil reference values | ||
+ | **DRO (diesel range organics) concentration (124 mg/kg) exceeded site screening criteria (10 mg/kg) | ||
*Excel file with data on metal concentrations in street sweepings: [[File:Metals in street dirt-sweepings.xlsx]] | *Excel file with data on metal concentrations in street sweepings: [[File:Metals in street dirt-sweepings.xlsx]] | ||
This discussion focuses on pretreatment practices. Pretreatment reduces maintenance and prolongs the lifespan of structural stormwater BMPs by removing trash, debris, organic materials, coarse sediments, and associated pollutants prior to entering structural stormwater BMPs. Implementing pretreatment devices also improves aesthetics by capturing debris in focused or hidden areas.
Because pretreatment practices remove material from stormwater runoff, they must be periodically cleaned to maintain their function. This page provides information on management of material collected in pretreatment practices, including disposal options.
For information on pretreatment, link here.
Below is a brief summary of the types of materials typically found in these practices.
The type of material collected in a pretreatment practice depends on the source of stormwater runoff. Primary constituents include sand, salt, leaves, and other litter and debris washed off streets, parking lots and sidewalks.
See the discussion below for results of sampling for materials collected by these practices.
There is limited information for sampling of sediments and other materials captured by pretreatment practices. The Excel spreadsheet below summarizes results from sampling studies. NOTE: This spreadsheet may be updated periodically and includes a date at the top of the spreadsheet.
File:Pretreatment sampling data.xlsx
In general, concentrations of metals and organic pollutants are below levels of concern. The following bullets summarize results for these studies.
Comparisons of results from these studies with Minnesota criteria, maximum concentrations of all metals except arsenic and lead are below industrial soil reference values.
Analysis of stormwater runoff and sediments collected by pretreatment practices indicate that "typical" concentrations of pollutants do not warrant testing and the material can be disposed at a permitted landfill.
The following steps are typically found in guidance for handling these materials.
Visual screening of water in a sump is recommended for the following.
For more information on screening, link here
Testing is recommended for the following.
The following links generally align with the section heading, although there may be some overlap at a specific site. For a summary of our literature review, [File:Pretreatment waste disposal literature review.docx link here].
Pretreatment sizing for basins and filters strips
Guidance for managing sediment and wastes collected by pretreatment practices
Tables
Other information and links