This page provides a summary of significant recent changes to this website. We anticipate this page will be updated infrequently. You may also access our responses to comments that have been submitted via the comment box found on each page of the website.
- December 20: The phosphorus removal efficiency for bioretention BMPs has been changed. Previously, a single value of 60 percent was given for this BMP. The new values are 100 percent for water that is infiltrated, 25 percent for water that passes through an underdrain, and 0 percent for water that bypasses the bioretention BMP. See Pollutant removal percentages for bioretention BMPs. This change is likely temporary as a technical workgroup is evaluating phosphorus removal rates for bioretention BMPs. Factors such as initial soil/media phosphorus content, depth above an underdrain, and presence of P-sorbing amendments in the soil/media will affect the removal efficiency of the BMP. It is anticipated the recommendations of the workgroup will be incorporated into the Manual in mid- to late January.
- December 16: Following a meeting of technical experts, an infiltration rate of 0.45 inches per hour was established for SM soils. The rate for these soils was previously 0.3 inches per hour. In the original Manual the rate for these soils was 0.6 inches per hour. See Design infiltration rates.
- December 4: We added information to the section on trees. This includes an overview, several tables listing properties for several tree species, and supporting material. We have additional information on trees that will be added in the next couple months, including design guidelines, construction specifications, and more.
- October 9: The section on Vegetated filter strips has been updated.
- September 26: We added two links in the left toolbar. The first is Categories, which provides a shortcut to the list of categories. Categories are basically an index of similar webpages. For example, one of the categories is Photos, which shows all the photos in the wiki. Results of our recent survey suggest people frequently use the Categories feature. The second link in the left toolbar is Response to comments. Unfortunately there is no easy way to display our responses to comments submitted via the Comment box on each page. Clicking on the comment link in the left toolbar shows most comments we receive along with our reply. We encourage people to submit comments using the Comment box on the bottom of each page. Comments can be on content of a page, suggested edits, errata, comments on wiki functionality, etc.
- August 2: A section on filter strips (as pre-treatment) has been added.
- July 16: A section on green roofs has been added. The section includes several pages (articles) discussing different aspects of green roofs, including general terminology, information on design, construction and maintenance, plant lists, references, case studies, and more.
- July 16: A separate page has been created called Information on pollutant removal by BMPs. The page contains links to tables showing data on pollutant removal, sections that contain information on pollutant removal, and external links to information on pollutant removal. The page was created to provide easy access to this data.
- May 21: Information on infiltration practices at contaminated (Brownfield) sites was added.
- May 21: References on canopy interception and evapotranspiration from trees was added.
- May 7: A new section on iron enhanced sand filters was added. It will be open for review through June, 2013.
- April 15: Table with design infiltration rates
- The table now contains one value for B soils (0.3 inches/hour). The previous version of the manual included rates of 0.3 and 0.6 inches/hour based on texture. The value of 0.6 was not supported by literature and a technical group determined there should be one value for B soils.
- The design rate for D soils is 0.06 inches/hour. This replaces the previous value of <0.2 inches/hour and is in line with the Minimal Impact Design Standards calculator.
- A/D, B/D, and C/D soils are assigned infiltration rates of 0.06 inches/hour, corresponding with a D soil. These soils are subject to seasonal high water tables, at which time they behave like a D soil.
- April 15: Safety factors - safety factors, previously called correction factors, are applied to field measured infiltration rates. They are intended to account for natural variability in infiltration rates of soils and in decreased infiltration performance of a BMP over time. A safety factor of 2 shall be applied to infiltration BMPs other than permeable pavement. A safety factor of 2.5 shall be applied to permeable pavement. For example, a measured infiltration rate for a bioretention system of 1.0 inches per hour shall be divided by the safety factor of 2, resulting in an infiltration rate of 0.5 inches per hour. In Version 2.X of the Manual, safety factors were calcualted using information in a table.
We completed migration of content from the 2008 Manual to this website during the last week of March. We do not anticipate further significant changes in Manual content during the wiki website rollout in April. Following that, we hope to incorporate the following changes into the Manual:
- new information on green roofs in May and June;
- updates to the bioretention section in early to mid summer
- incorporation of information on trees in late summer and early fall;
- new sections on stormwater Minimal Impact Design Standards; and
- new information on iron-enhanced filters this summer.
Information: Mediawiki automatically saves all edits mad to any page in this website. Viewers can therefore see all edits made to the website by visiting the Recent changes page, which can be accessed via a link in the left toolbar.