News – StormTac

Release notes v18.3.1

17 July, 201817 July, 2018

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

11 July, 2018

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…

1 July, 2018

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…

27 May, 2018

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.

Updated StormTac database v. 2018-05-09

9 May, 201811 May, 2018

Updated StormTac database v. 2018-05-09

1. Complemented reference data of stormwater from different land uses. Especially complemented with by StormTac compiled flow proportional data as mean values from many US sites from the data base NSQD (2015), with much data from a large number of substances.

2. Added land uses (since earlier included in StormTac Web) with stormwater standard concentrations:

– Multi-family area with street trees in a skeletal soil (macadam-soil mixture) without Local disposal of stormwater in the block.

– Multifamily area with street trees in a skeletal soil (macadam-soil mixture) with Local disposal of stormwater in the block.

– Multifamily area with biofilter without local disposal in block

– Multifamily area with biofilter with local disposal in block

– Office area with street trees and skeletal soil (macadam-soil mixture) and blocks without local disposal

– Block without road with local disposal of stormwater.

3. Updated BaP-values in stormwater from the land uses:

– Residential area with total local disposal of storm water

– Terraced area with total local disposal of storm water

Relase notes v18.2.1

19 April, 201823 April, 2018

Relase notes v18.2.1

– Included area names in the scroll list when selecting area (A1, A2, etc.) in the flow chart.

– The box “Retention basin” has been made clearer regarding which parameters can be used for different selection of facilities. Those who do not belong to the selected facility are highlighted in blue in the input fields and can not be changed.

– The box “Biofilter”. In the header at the top left is now showing what facility is selected. After saving your changes, you can see which type of facility it is instead of having to go to the flow chart and look at the facility picture below the box.
The facilities grass ditch / swale are explained as separate facilities. These are now also shown individually in the facility picture below the box.

– Some minor bug fixes have been made.

– Small design and layout changes have been made.

Updated function for natural ground for smaller areas than…

3 April, 201823 April, 2018

Updated function for natural ground for smaller areas than 10 hectares

For areas less than 20 hectares, the maximum flow at a 5-year rain corresponds to 40 l/s/ha (P110, Swedish Water, 2016), whereby the equation has been adapted to this, resulting in smaller flow than previous in smaller areas than 10 hectares. However, the same equation as earlier is valid for areas > 10 ha.

Updated concentrations for phosphorus, nitrogen and benzo(a)pyrene from woodland,…

12 March, 2018

Updated concentrations for phosphorus, nitrogen and benzo(a)pyrene from woodland, farmland and other open land uses

Results of a comprehensive literature study and comparison between different references and measurement data. The update is particularly important in calculating load before exploiting an area and if the load should not increase after exploitation. The concentration data have been reduced for phosphorus and nitrogen but increased from zero to small levels for benzo(a)pyrene. This applies to both concentrations of stormwater and baseflow, with total calculated phosphorus and nitrogen concentrations being lowered more for woodland and farmland than the standard stormwater concentrations. Reference data is shown in blue text in the database from 2018-03-11 and implemented for new projects that start after 2018-03-11.

Updated database v. 2018-02-26

26 February, 2018

Updated database v. 2018-02-26

New data of zinc surfaces and copper surfaces, e.g. copper facades or roofs, zinc rails or roofs, which can be calculated in StormTac Web by using the land use “Own”, see Guide Description of land uses 2018-02-26.

Updated flow detention functions in serial facilities

13 February, 201814 February, 2018

Updated flow detention functions in serial facilities

Updated and revised functions have been developed for calculating required volumes for flow detention in serial facilities. These take into account factors for flow reduction in both previous and subsequent facilities.

The revisions affect both existing and new projects but do not make any changes in individual facilities and the first facility in a series of facilities.
They provide relatively small changes in subsequent facilities if the flow is not reduced as much between the facilities, but major changes if large flow is passed (no or less throttle) with greater flow detention downstream.

The functions take into consideration that, as before, the flow from the previous facility reduces the outflow up to some longer rainfall duration, after which all lower flows flow further downstream.
If long duration will be dimensioning downstream and there is strong flow reduction downstream, this may result in the upstream facility, in some cases, not will be as effective as you might think for reducing the required detention volume downstream.
This because a flow below the reduced flow could be dimensioning for long duration.
Then you can try to increase the flow reduction factor, which results in shorter design rain duration and reduces the required detention volume.
In practice, this means that you use a flow regulator in the outlet.
All this can now be simulated better than before by using the updated and revised functions.