Timelines shown below are approximate. We update this page infrequently.

Information: Updated March 28, 2022

Iron Enhanced sand filters

Iron enhanced sand filters (IESFs) incorporate iron into sand filter design for the purpose of removing dissolved phosphorus. Because dissolved phosphorus is much more bioavailable than particulate phosphorus and because few stormwater best management practices effectively remove dissolved phosphorus, IESFs are an important practice in locations where receiving waters are impacted by phosphorus.

We executed a work order to collecting information for IESFs and will use that information to update guidance in the Manual on design, construction, and O&M of IESFs. In 2019 we developed a spreadsheet listing over 150 IESFs in Minnesota. The spreadsheet with this information can be found here. We collected primarily location and general information about the IESFs.

This new work is intended to collect additional information pertaining to the performance of these practices. The tasks for this work order are summarized below.

  • Task A: Determine data to be collected. Identify the parameters to be collected for Task B. Examples include but are not limited to information on iron content, organic matter content, infiltration rate, drying time, pretreatment method, groundwater flow, the ratio of watershed to treatment practice, whether the water application was uniform, appropriateness of the practice, amount of shade, and whether the practice is online or offline.
  • Task B: Solicit existing data. Collect quantitative and qualitative data on design, siting, construction, performance, and maintenance, using the parameters identified in Task A. The data will be incorporated into the recently completed Iron Enhanced Sand Filter Database (MPCA 2019b).
  • Task C: Analyze Existing Data. Analyze the existing data to identify gaps and initial relationships between collected variables and performance. Analysis methods may include time series analysis, percent exceedance, linear and non-linear regressions, statistical comparisons (paired and unpaired, ANOVA, etc.), and other methods for quantitative/qualitative analyses, as applicable.

Timeline: January 10, 2022 – December 31, 2022
Deliverables: Excel spreadsheet populated with info, an interim report summarizing the data analysis including assessment of site-specific parameters identified as risk factors for poor performance.

Green Infrastructure

Over the past two years we have been building information on Green Infrastructure (GI) into the stormwater wiki. See the What's New page in the wiki to see recent updates.

We currently have a work order to update information on planning for GI. Using publically available resources, we will research and compile planning content for GI in the stormwater manual. This content could include, but is not limited to:

  • General description of planning as it relates to GI practices
  • Steps involved in the planning process
  • Regional considerations
  • Who should be involved in the planning process
  • Common and perceived roadblocks for GI implementation
  • How to incorporate GI into ordinances
  • How GI can complement stormwater systems
  • Explanation of the costs and benefits of planning
  • The role planning for GI can play in climate resiliency
  • Links to external planning guidance and resources

Timeline: January 2022 – June 2022 or December 2022
Deliverables: A new Planning Page in the stormwater manual populated with planning content


We executed a work order to update information on vegetation into the stormwater wiki. The goals are summarized below.

  • Develop guidance and recommendations for assessing existing vegetation, including but not limited to the following.
    • Existing vegetation to preserve (heritage trees, threatened and endangered species, desired plants)
    • Wetland delineation
    • Historic plant community (or wetlands) to identify within project area or potentially replicate. Link to appropriate resources, such as Marshner’s Map and Historical Aerial resources such as Minnesota Historical Aerial Photos Online (MHAPO) and Mississippi River Commission Maps
    • Existing plant community classifications to identify within project or potentially replicate
    • Invasive species identification and removal, including invasive species removal strategies, considerations, and regulations
    • Mitigation considerations (e.g. tree replacement, wetland permits)
  • Develop guidance and recommendations for assessing existing soil health and function, including but not limited to the following.
    • Ability for soil to support vegetative growth, considering but not limited to
      • nutrient status
      • pH
      • bulk density and
      • microbial function in rhizosphere (fungi, algae, bacteria, protozoa).
    • Soil testing, considering but not limited to the following.
      • Conducting soil tests on indicators as they may relate to vegetation establishment and long term planting success, including water content, water holding capacity, infiltration rates, compaction, nutrient and organic matter content, soil composition/structure, bulk density, soluble salts, metals and minerals, pH, and soil biotic assessment.
      • Interpreting soil test results, including soil ecological function, ability to support vegetative growth, and ability to support hydraulic/hydrologic function.
      • Amending soils based on test results for plant establishment, including modifying soil pH, adding organic or inorganic amendments, and soil loosening or stabilization techniques.
      • Develop guidance and recommendations for selecting appropriate soil mixes for certain design conditions (e.g. low organic media, salt tolerance, high iron, etc.)
      • Develop guidance and recommendations for assessing individual vegetation impacts (e.g., N-fixers effect on nutrient status, deep rooters effect on hydrology, etc.)
  • Develop guidance and recommendations for creating a vegetation management plan for future maintenance for future maintenance, including but not limited to the following.
    • Establishment goals and objectives, including resilient designs
    • Site description, including management zones
    • Site preparation
    • Vegetation monitoring and adaptive management, including performance criteria
    • Documentation and reporting, including figures and maps

Timeline: March-December 2022
Deliverables: Memo(s) summarizing guidance on design considerations and recommendations, site assessment, and site preparation when incorporating vegetation at a development or redevelopment site, and for creating a site management plan.

Bioretention media waste management

Executed a work order to provide information on characterization of soil and engineered media in stormwater treatment practices, including disposal recommendations.

Timeline: March-July, 2022
Deliverables: Documents and/or memos providing recommended updates to the Minnesota Stormwater Manual.

This page was last edited on 3 December 2022, at 19:02.