m |
|||
(7 intermediate revisions by the same user not shown) | |||
Line 4: | Line 4: | ||
[https://public.govdelivery.com/accounts/MNPCA/subscriber/new?qsp=MNPCA_1 Subscribe to the email list here]. | [https://public.govdelivery.com/accounts/MNPCA/subscriber/new?qsp=MNPCA_1 Subscribe to the email list here]. | ||
+ | |||
+ | ==July 2022== | ||
+ | Although it has been several months since the last update to the Stormwater Manual wiki, we have not added a lot of new material. However, we are beginning a review and reorganization process for the wiki. | ||
+ | |||
+ | ===Updates to the Manual wiki (July 2022)=== | ||
+ | *'''Planning green stormwater infrastructure (GSI) projects and practices''': We continue to add information to the [https://stormwater.pca.state.mn.us/index.php?title=Green_Stormwater_Infrastructure_(GSI)_and_sustainable_stormwater_management green infrastructure section of the manual]. A new page called [[Planning green stormwater infrastructure projects and practices]] was created. The page provides information on how to plan for incorporating GSI into new development and retrofit projects. Several links are included, including links to ordinances, checklists for identifying barriers to implementing GSI, planning case studies, cost information, potential funding sources, and more. | ||
+ | *'''Operation and maintenance considerations for vegetation in stormwater management''': We've begun incorporating information on vegetation into the manual. A recently created page called [[Operation and maintenance considerations for vegetation in stormwater management]] provides information on establishing vegetation at a site and creating a vegetation management plan. This page is still under review. | ||
+ | *'''Stormwater wiki reorganization''': The wiki has over 2000 pages and over 1500 images. It has become disorganized. We've begun the process of evaluating a better structure for organizing the content. This process will include deleting several hundred pages and condensing information. We hope to have a draft structure within the next month or two. | ||
+ | *'''Stormwater wiki page updates''': We are in the process of going through every page in the wiki. Revised pages will include updating links, updating information as needed, providing definitions where appropriate using hover boxes, improving tables and visuals if appropriate, and creating pdfs of most pages. Some pages may contain video summaries. Remember that pdfs are static. To see when the last update occurred, scroll to the bottom and view the date of the last update or go to the Page Information link in the left toolbar. | ||
+ | |||
+ | ===What are we working on (July 2022)=== | ||
+ | *Continue reorganizing the wiki and updating pages over the next 9 months | ||
+ | *Create new content on street sweeping. We are working with the University of Minnesota to develop content focusing on establishing a street sweeping program for water quality purposes. New material will include | ||
+ | *Iron-enhanced sand filters | ||
+ | *Vegetation | ||
+ | *Green infrastructure | ||
+ | |||
+ | ===Featured article - Green stormwater infrastructure and alphabet soup (July 2022)=== | ||
+ | [[File:Terminology.png|400px|thumb|alt=schematic for stormwater terminology|<font size=3>Schematic illustrating different concepts</font size>]] | ||
+ | |||
+ | We are continually bombarded with new terminology and acronyms. These days, an important focus of stormwater is green infrastructure, anture-based solutions, and sustainability. What do these mean and is it important to know the distinction between these? | ||
+ | |||
+ | To begin, there is no universal definition of these. So this featured article provides our view on this topic. If you want some basic definitions, we have a page called [[Green infrastructure and green stormwater infrastructure terminology]]. | ||
+ | |||
+ | The core concept is that we receive all our resources, needs, and provisions from nature. Examples include clean air and water, nutrient cycling, pollination, and minerals. These may become depleted or impaired as we utilize these ecosystem services, making them unavailable for future generations. This is not sustainable, since at some point lack of one or more ecosystem services will make life untenable. To become sustainable, we must utilize ecosystem services in a way that keeps them useable into the future. | ||
+ | |||
+ | One way to achieve sustainable development is to design and build systems that mimic nature. This is done by conserving resources or engineering systems that retain or simulate natural processes. These systems include transportation, buildings, utilities, air and water management, waste management, and so on. Concepts incorporating these different features typically occur at the watershed, city, or large development scale and include the following. | ||
+ | *Large scale design (e.g. city, watershed) | ||
+ | *Small- and medium scale design (sub-watershed, large development): Better Site Design, Conservation Design | ||
+ | *Built: Green infrastructure, Nature-based solutions | ||
+ | |||
+ | Stormwater is one factor to consider in sustainable development. | ||
+ | *Planning stormwater management: Low Impact Development (infiltration, underground storage/retention) | ||
+ | *Built stormwater management: Green stormwater infrastructure (e.g. bioretention, permeable pavement, green roofs) | ||
+ | |||
+ | ===In the news and events (July, 2022)=== | ||
+ | |||
+ | ===[https://stormwater.pca.state.mn.us/index.php?title=Stormwater_quizzes#Vegetation_quiz Take the vegetation quiz]=== | ||
==February 2022== | ==February 2022== | ||
Line 21: | Line 59: | ||
**Credits for dissolved phosphorus (DP). TP credits are currently limited based on the assumption the devices are not removing dissolved phosphorus. The credit scheme includes three tiers. Tier 3 will include credits for removing DP. Before Tier 3 credits can be determined, however, we must develop methods for calculating the performance of a device with respect to DP. Ultimately, DP credits may be given for devices that have a mechanism for removing DP (e.g. an amendment) or that retain runoff water (e.g. through infiltration). | **Credits for dissolved phosphorus (DP). TP credits are currently limited based on the assumption the devices are not removing dissolved phosphorus. The credit scheme includes three tiers. Tier 3 will include credits for removing DP. Before Tier 3 credits can be determined, however, we must develop methods for calculating the performance of a device with respect to DP. Ultimately, DP credits may be given for devices that have a mechanism for removing DP (e.g. an amendment) or that retain runoff water (e.g. through infiltration). | ||
**'''Time frame''': We anticipate completing guidance for calculating annual loads and for assigning Tier 3 credits by this summer. | **'''Time frame''': We anticipate completing guidance for calculating annual loads and for assigning Tier 3 credits by this summer. | ||
+ | *We created a page called [[Guidance and recommendations for storing transported snow and for on-site snow storage]]. This page provides recommendations for managing and storing snow, including information for snow collected from impervious surfaces and transported to a storage location as well as information on storing snow on-site. The recommendations focus on protection of surface waters (lakes, rivers, wetlands), except where otherwise noted. The page is largely populated but will be undergoing some additions in February, 2022. | ||
===What are we working on (February 2022)=== | ===What are we working on (February 2022)=== | ||
− | *[https://stormwater.pca.state.mn.us/index.php?title=Iron_enhanced_sand_filter_(Minnesota_Filter) Iron enhanced sand filters]. In 2019 we compiled a spreadsheet containing information on | + | *[https://stormwater.pca.state.mn.us/index.php?title=Iron_enhanced_sand_filter_(Minnesota_Filter) Iron enhanced sand filters]. In 2019 we compiled a spreadsheet containing information on 166 <span title="Iron-enhanced sand filters are filtration Best Management Practices (BMPs) that incorporate filtration media mixed with iron. The iron removes several dissolved constituents, including phosphate, from stormwater. Iron-enhanced sand filters may be particularly useful for achieving low phosphorus levels needed to improve nutrient impaired waters. "> [https://stormwater.pca.state.mn.us/index.php?title=Iron_enhanced_sand_filter_(Minnesota_Filter) '''iron-enhanced sand filters''']</span> (IESFs) in Minnesota. At the time there was limited performance information for these bmps. We have executed a work order to revisit a subset of these bmps and analyze their performance. The resulting information will be used to update guidance on design, construction, operation, and maintenance of IESFs. Projected timeline - late summer 2022. |
*Vegetation: We have created a new page in the wiki called [[Plant and vegetation information for stormwater management]]. This page provides a framework for information on plants and vegetation that will eventually be incorporated into the wiki. We have a current work order to develop information on site assessment, preparation, design considerations and recommendations for vegetation in stormwater management and on operation and maintenance considerations for vegetation in stormwater management. We anticipate this information will be available in late summer, 2022. | *Vegetation: We have created a new page in the wiki called [[Plant and vegetation information for stormwater management]]. This page provides a framework for information on plants and vegetation that will eventually be incorporated into the wiki. We have a current work order to develop information on site assessment, preparation, design considerations and recommendations for vegetation in stormwater management and on operation and maintenance considerations for vegetation in stormwater management. We anticipate this information will be available in late summer, 2022. | ||
*[https://stormwater.pca.state.mn.us/index.php?title=Green_Stormwater_Infrastructure_(GSI)_and_sustainable_stormwater_management Green infrastructure]: A long-term project to improve information on Green Stormwater Infrastructure in the Manual started in 2021. This work will be completed in phases. A current work order addresses design considerations for green stormwater infrastructure best management practices. We anticipate this work being completed by late summer, 2022. | *[https://stormwater.pca.state.mn.us/index.php?title=Green_Stormwater_Infrastructure_(GSI)_and_sustainable_stormwater_management Green infrastructure]: A long-term project to improve information on Green Stormwater Infrastructure in the Manual started in 2021. This work will be completed in phases. A current work order addresses design considerations for green stormwater infrastructure best management practices. We anticipate this work being completed by late summer, 2022. | ||
Line 61: | Line 100: | ||
When snowmelt runs off from a surface or snow storage area, routing the meltwater across a permeable surface allows some infiltration and may slow the rate of delivery to the conveyance system. This may spread the delivery of chloride-rich water to receiving waters and smooth the peaks in chloride concentration in the receiving water. | When snowmelt runs off from a surface or snow storage area, routing the meltwater across a permeable surface allows some infiltration and may slow the rate of delivery to the conveyance system. This may spread the delivery of chloride-rich water to receiving waters and smooth the peaks in chloride concentration in the receiving water. | ||
− | ===In the news ( | + | ===In the news and events (February, 2022)=== |
[[File:Doug Snyder.png|300px|thumb|alt=photo of Doug Snyder]] | [[File:Doug Snyder.png|300px|thumb|alt=photo of Doug Snyder]] | ||
Line 68: | Line 107: | ||
*[https://www.wateronline.com/doc/urban-greening-not-a-panacea-for-dealing-with-extreme-weather-study-finds-0001 Urban Greening ‘Not A Panacea' For Dealing With Extreme Weather, Study Finds]. The authors summarize [https://www.nature.com/articles/s41467-022-28160-8 a study (Cuthbert et al., 2022)] pointing out that green stormwater infrastructure is just one piece of the urban hydrology puzzle. By itself, it cannot simultaneously solve issues of flooding and heat island mitigation. | *[https://www.wateronline.com/doc/urban-greening-not-a-panacea-for-dealing-with-extreme-weather-study-finds-0001 Urban Greening ‘Not A Panacea' For Dealing With Extreme Weather, Study Finds]. The authors summarize [https://www.nature.com/articles/s41467-022-28160-8 a study (Cuthbert et al., 2022)] pointing out that green stormwater infrastructure is just one piece of the urban hydrology puzzle. By itself, it cannot simultaneously solve issues of flooding and heat island mitigation. | ||
*'''LOCALLY''': [https://www.mwmo.org/news/mwmo-executive-director-doug-snyder-announces-retirement/ The Doc is leaving the house]. Mississippi Watershed Management Organization (MWMO) Executive Director Doug Snyder will retire at the end of February 2022, after nearly 20 years of service at the MWMO. We'll miss you Doug. | *'''LOCALLY''': [https://www.mwmo.org/news/mwmo-executive-director-doug-snyder-announces-retirement/ The Doc is leaving the house]. Mississippi Watershed Management Organization (MWMO) Executive Director Doug Snyder will retire at the end of February 2022, after nearly 20 years of service at the MWMO. We'll miss you Doug. | ||
+ | *Events: For a full list of events, [https://stormwater.pca.state.mn.us/index.php?title=Events see this link]. Here are some events of interest. | ||
+ | **U of MN P8 training on the use of the P8 software. P8 is a free software package for modeling stormwater pollutant management in urban watersheds. This training will be offered online through zoom in the afternoons of March 2 and March 3, with a short session on February 23 to confirm software installation and access. For more information on this training, [https://erosion.umn.edu/courses-registration/ed8001-using-p8-software-model go to this link]. | ||
+ | **[https://www.eventscribe.net/2022/IECA2022/ International Erosion Control Association Annual Conference], Minneapolis, MN, February 15-18, 2022 | ||
+ | **[https://ccaps.umn.edu/minnesota-water-resources-conference Water Resources Conference], October 18-19, 2022 | ||
===[https://stormwater.pca.state.mn.us/index.php?title=Stormwater_quizzes#Chloride_quiz '''Take the chloride/deicer quiz''']=== | ===[https://stormwater.pca.state.mn.us/index.php?title=Stormwater_quizzes#Chloride_quiz '''Take the chloride/deicer quiz''']=== |
Over the past several years we've heard from people suggesting they be notified when updates are made to the Minnesota Stormwater Manual. We have also identified several stormwater management concerns and felt that focused communication on these specific issues might be useful. We therefore decided that periodic emails to subscribers would be one way of notifying practitioners about updates to the Manual and focus on specific stormwater issues. Emails are sent periodically, roughly every 6-12 weeks.
The emails contain only a short description of updates and other information. This page provides more detailed information. It is organized by the approximate dates when emails are sent to subscribers. We welcome recommendations for featured topics and links to case studies and other items of information. Please contact Mike Trojan at the MPCA..
Subscribe to the email list here.
Although it has been several months since the last update to the Stormwater Manual wiki, we have not added a lot of new material. However, we are beginning a review and reorganization process for the wiki.
We are continually bombarded with new terminology and acronyms. These days, an important focus of stormwater is green infrastructure, anture-based solutions, and sustainability. What do these mean and is it important to know the distinction between these?
To begin, there is no universal definition of these. So this featured article provides our view on this topic. If you want some basic definitions, we have a page called Green infrastructure and green stormwater infrastructure terminology.
The core concept is that we receive all our resources, needs, and provisions from nature. Examples include clean air and water, nutrient cycling, pollination, and minerals. These may become depleted or impaired as we utilize these ecosystem services, making them unavailable for future generations. This is not sustainable, since at some point lack of one or more ecosystem services will make life untenable. To become sustainable, we must utilize ecosystem services in a way that keeps them useable into the future.
One way to achieve sustainable development is to design and build systems that mimic nature. This is done by conserving resources or engineering systems that retain or simulate natural processes. These systems include transportation, buildings, utilities, air and water management, waste management, and so on. Concepts incorporating these different features typically occur at the watershed, city, or large development scale and include the following.
Stormwater is one factor to consider in sustainable development.
It's been several months since our last update, as we were wrapping up a number of projects.
It is widely acknowledged the most effective strategy for protecting receiving waters from chloride pollution is by reducing use of chloride-deicers. But elimination of deicers is not practical in the foreseeable future. Are there ways to manage urban runoff having elevated chloride concentrations?
A workgroup of stormwater and groundwater professionals recently produced a white paper, published by the Minnesota Groundwater Association, that addresses this topic. The paper, titled Impacts of Stormwater Infiltration on Chloride in Minnesota Groundwater, provides a discussion of chloride in stormwater runoff and potential groundwater impacts associated with infiltration of stormwater runoff.
Chloride concentrations in stormwater runoff are highly variable and seasonally dependent. Concentrations in winter range from several hundred mg/L to as high as 40,000 mg/L, with typical concentrations being closer to 1000 mg/L. Concentrations outside the deicing season are typically less than 50 mg/L, with concentrations decreasing from spring into fall. Chloride is toxic to aquatic life, with the aquatic life standard being 230 mg/L. The drinking water standard is based on taste and is 250 mg/L. Chloride is also toxic to vegetation, can corrode materials, and can inhibit lake mixing, which may in turn result in changes in phosphorus cycling.
Though chloride is not retained in soil, studies indicate it is attenuated in soil. As a result, there is a lag time between chloride entering soil, including a media-based stormwater best management practice, and its eventual movement to a receiving water, be that a lake, stream, river, or aquifer. Understanding this process and the eventual receiving water can help us manage runoff containing chloride. The white paper provides the following conclusions.
The white paper also provides several recommendations for managing stormwater runoff that contains elevated concentrations of chloride.
When snowmelt runs off from a surface or snow storage area, routing the meltwater across a permeable surface allows some infiltration and may slow the rate of delivery to the conveyance system. This may spread the delivery of chloride-rich water to receiving waters and smooth the peaks in chloride concentration in the receiving water.
The MIDS Calculator and MPCA Simple Estimator
The Minimal Impacts Design Standards (MIDS) Calculator and MPCA's Simple Estimator (Estimator) are two tools used to estimate volume and pollutant load reductions associated with implementation of stormwater control measures, also known as best management practices (BMPs). Each of these tools is widely used. The MIDS Calculator, for example, has had over 8000 downloads in the past 3 years, while the Estimator is used by many MS4 permittees to assess progress toward or determine if they are meeting a TMDL Wasteload Allocation. The advantage of these tools is they are relatively easy to use and understand. However, with simplicity comes the potential for inaccuracy. This article provides a high level discussion of these two tools, including their advantages and potential pitfalls. The closing paragraph in this article provides a discussion of how MPCA hopes to move forward in providing a better understanding and application of these tools.
MIDS Calculator
The MIDS Calculator was originally designed as a tool for determining how to meet the MIDS performance goal of 1.1 inches at development sites. Detailed discussion of the Calculator and MIDS performance goal are found on the following pages.
Despite the original intent, the Calculator is being used for purposes other than assessing volume reduction at individual sites. It was and continues to be widely used for water quality determinations, including at sub-watershed scales. This presents a number of challenges since the Calculator is not easily modified or is inflexible in addressing water quality at these larger scales. Examples of some limitations of the Calculator include the following.
These are just examples of limitations.
Fundamentally, the MIDS Calculator is limited by its platform. It is built in Excel and addressing these various issues would be challenging. Additionally, as these issues get addressed, the tool becomes more complex to use, defeating one of its original intentions.
MPCA Simple Estimator
The 2013 MS4 permit required quantification of pollutant reductions to demonstrate a permittee was making progress toward achieving or had achieved a TMDL ( total maximum daily load) wasteload allocation. The tools available, such as P8, WinSLAMM, SWMM, and even the MIDS Calculator, were accessible only to "modeling experts". As a result, the MPCA developed a simple Excel spreadsheet that employed the Simple Method. This spreadsheet was readily accessible to most practitioners and could be used to demonstrate progress toward meeting a WLA.
The tool was intended to be used for demonstrating progress toward reducing pollutant loads, since it only considered a single watershed and there was limited guidance on modifying defaults in the spreadsheet. To make the tool more robust and rigorous, the Excel workbook was updated to include up to 10 subwatersheds (as separate worksheets), default values were updated based on literature reviews, and guidance for using the tool was expanded. The tool was again widely used by permittees during the 2020-21 permit cycle. Questions and submittals we received indicated the tool continues to have limitations and is not being correctly applied in some situations. Some of the limitations in the tool include the following.
Addressing these issues
MPCA hopes to conduct a more rigorous analysis of how these tools are being used and develop appropriate guidance. Additional training is likely. The Estimator may undergo modifications based on this analysis. Unfortunately, changes to the MIDS Calculator are unlikely as the Excel platform is limiting in terms of adjusting the Calculator for water quality modeling. We are in the process of documenting some of these issues and hope to have more detailed guidance and training in place in 2022.
Alternative models may be used. The Minnesota Stormwater Manual provides a detailed summary of available water quality models. These models typically require greater modeling expertise and lack extensive documentation in the Manual, though many have user guides. The MPCA will also accept other modeling approaches, but it is recommended that permittees consult the MPCA prior to using alternative models.
Take the green infrastructure O&M quiz
The Minnesota Construction Stormwater Permit requires pretreatment for filtration and infiltration practices. Forebays or other pretreatment practices are highly recommended for constructed stormwater ponds. The permit, however, does not specify the type of or sizing for pretreatment practices. We are discovering that many stormwater best management practices (bmps, also often called stormwater control measures or scms) are not performing as designed, often due to heavy sediment loads to the bmp and to poor design.
Proper pretreatment can extend the life and improve performance of downstream bmps. But we frequently hear stories about inadequate or improperly designed pretreatment. This is unfortunate, since the Manual contains a wealth of information on pretreatment. For example, did you know the Manual contains the following?
Below are examples of some design issues that have been brought to our attention.
The information in the manual could be better organized and made more accessible. So, we hope to execute a work order this summer to better organize the information on pretreatment. You can help by providing the following (NOTE: We cannot endorse or promote specific commercial products, processes, or services).