Updated standard concentrations for the following land uses

Updated standard concentrations for the following land uses

– Block without road (changed the most of the 13 first substances for stormwater and baseflow after calculations and investigations)
– Block without road with local disposal of stormwater (changed the most of the 13 first substances for stormwater and baseflow)
– Leisure houses (only increased P concentration)
– Roofs (only increased P concentration)
– Yard area within block (only increased P concentration)
– Residential area without roads (only reduced concentration of PAH16)

GIS data import implemented in StormTac Web

GIS data import implemented in StormTac Web

Users now have the ability to import area values per land use and subwatershed area from GIS.
This is the first step to facilitate the work between GIS and StormTac Web.

The next step is to visualize calculated data into GIS from StormTac Web. A work in progress.

Irreducible concentration – new paper to download

Irreducible concentration – new paper to download

Irreducible concentrations (Cirr) is the minimum outflow concentrations, a Stormwater Treatment Facility´s (STF’s) inability to reduce pollutant concentrations below a certain level.

Site-specific design parameters, such as Cirr, have great impacts on the design
and choice of type of stormwater treatment facilities.

This is described further in the reviewed conference paper “Modelling different types of stormwater treatment facilities considering irreducible concentration”, by Larm T. and Wahlsten A., presented during the conference “11th International Conference on Urban Drainage Modelling” (UDM), Palermo, Italy, Sept. 23-26, 2018.

Updated values of Cirr for many different substances and types of facilities are presented in the StormTac database and are limplemented in the stormwater & recipient model StormTac Web.

The paper and the updated database can be downloaded from this web page.

Release notes v18.3.2

Release notes v18.3.2

More detailed design of smaller underground retention basins with filters, larger underground retention basins without filters and macadam basins.

The dimensioning of larger underground retention basins without filters and macadam basins now takes direct account of the calculated required flow detention, integrated in the box, with the option of specifying maximum outflow in the box. The length, width and depth of the basins are dimensioned and these are presented in the picture below the box indicating if the depth becomes too large. You may then need to increase the volume or outflow of the basin. Warning triangles appear if you go beyond normal recommendations.
The dimensioning of smaller underground retention basins with filters has basically no flow detention (such as drain inlet filters and oil separators which can also be specified in the box), but now the dimensions in the picture below the box are shown.

Updated land use specific standard concentrations, including new functions…

Updated land use specific standard concentrations, including new functions of traffic intensities versus pollutant concentrations for roads. Updated reduction efficiencies.

A comprehensive literature search and update of the database has been performed, with more data on land use specific concentrations and reduction efficiencies for different types of facilities for many different substances. A comparative study between different land uses and different types of facilities has also been performed, which resulted in some changed values to get reasonable data. Two new rows have been added to the database for each land use, presenting the estimated minimum and maximum concentration used in StormTac Web when changing the “density factor” for a specific land use.
The functions between measured traffic intensities and measured pollutant concentrations have been updated to include all data, with the exception of excluding data of Pb previous to 1995 (Pb-free petrol). Before, the functions were based on only Swedish data from a 10-year period of time since that data resulted in higher fit to the data than if all data are included. These functions are described in the guide in StormTac Web, with references. In the guide, the description of the land use roads has also been updated with description of what kind of traffic intensity (e.g. for both driving directions) should be used for what road area.
The changed standard concentrations and reduction efficiencies have been marked in the database and implemented in StormTac Web. This improves the accuracy of the predictions of pollutant loads.

Release notes v18.3.1

Release notes v18.3.1

Max water velocity through ponds and wetlands. Calculation of the cross-sectional area at maximum water depth in ponds and wetlands, as well as the maximum water velocity flowing through this cross-section, compared to velocities at risk of erosion. These data are reported in Result report 4.2.

The Table Stormwater concentration (ug/l) per land use in Result Report 3.1 has been updated and does not any longer show overall standard concentrations per land use, but now calculated concentrations per land use based on specified factors for traffic intensities and density factors that increase / decrease the land use specific concentrations depending on input site-specific properties. These are those used in the pollutant calculations, as was the case earlier, but these were not previously reported per land use. If no such factors are specified in the Stormwater box, the table shows the same data as before, i.e. general standard concentrations.

Revised calculation of the total volume of underground macadam basins, where the previous parameter of design rain depth, which included the share of pores in macadam, is now replaced by a lower rain depth with a separate indication of the share of pores as input in the basin box. This gives a clearer and more accurate calculation of the total volume of the basin, which, however, becomes the same as before at a share of pore of 0.33 (default value in the box). The equation presented at the value in the flowchart has also been revised to contain this input share of pores (porosity for macadam).

Revised equations for baseflow and runoff presented in the flowchart, now presenting flow in l/s and concentration in ug/l.

Updates StormTac Web

Updates StormTac Web

– New calculated cross-sectional velocity in transport ditches, with recommended max velocities (see Result report 2.2).

– Added a possibility to save different flow reduction factors (box Flow detention facility) in different areas, A1, A2, …

– Revised section of wet ponds & wetlands, in which the embankment is deleted but instead mowed to the guide as recommended solution for a facility with a forebay.

– Revised section of ditches and swales for designs with no raised bypass (parameter h8).

Updated irreducible concentrations in StormTac database and in StormTac…

Updated irreducible concentrations in StormTac database and in StormTac Web

The values affect the maximum treatment effect that can be achieved by stopping the treatment when these minimum levels are reached. The difficulty in achieving lower levels is due to e.g. the decomposition of plants, sedimentation due to high flows and that vegetation beds (soil) and filters contain materials that can leak nutrients and pollutants. You can test different facilities and combinations of facilities with different irreducible concentrations if lower outlet concentrations are required.

The update is a result of a comprehensive investigation and literature review and the preparation of a reviewed paper for presentation at the International Conference UDM, Palermo, 24-26 September, 2018. However, further investigation will take place in August-September 2018 by developing flow-weighted outlet concentrations for a large number of facilities in the BMP Database, after which a new update of the irreducible concentrations will be made.

Implementation in StormTac Web of new guidelines for stormwater…

Implementation in StormTac Web of new guidelines for stormwater treatment in existing areas or areas of exploitation

Measures need to be investigated regarding what is required to achieve good water status in lakes and streams. Treatment requirements must be made when planning areas for new building and rebuilding. The requirements differ depending on in which recipient catchment area the study area is located. To know if pollutant treatment is necessary in existing and exploited areas, calculated acceptable load (kg/year) per recipient and substance should be used. This acceptable load has been calculated since many years in StormTac Web. However, in this new development of the model the acceptable load (kg/year) is distributed over the total area (ha) in the watershed area to the recipient, to be used as guideline for treatment of an existing or planned area. This results in specific calculated acceptable load (kg/year) for the area of exploitation which is a much more relevant and effective criteria to work against when designing treatment facilities for the area, compared to working against outlet concentration criteria (µg/l).

If the calculated load from the area is greater than its calculated acceptable load, a treatment action is required to decrease the load from the area. An action type can be any type of stormwater treatment facility, supplemented with a flow detention function if necessary. To get adequate treatment, different types and series-coupled facilities of the same or different types can be tested in different combinations. Another type of action to cope with required treatment may be to reduce the rate of exploitation.

This new feature of StormTac Web can be used as an effective tool for municipalities working with their action plans to design treatment facilities in their planned areas of exploitation to achieve good water status in the receiving waters.