News – StormTac

New equation for designing required detention volume at heavily…

1 April, 20193 April, 2019

New equation for designing required detention volume at heavily throttled outlets

The rain intensity I was previously calculated with Dahlström’s equation (Dahlström, 2010) for all durations, but at extremely throttled outflows, it may be the question of durations that are 24 hours or longer before the required maximum detention volume is obtained.

For such long durations, from one to four days, the intensity is now calculated according to Dahlström (1979). This procedure is in accordance with P110 (Svenskt Vatten, 2016).

This results in lower intensity at design durations ≥ 24 hours than previous method gave, but the same as before in most cases (<24 hours). Before, the maximum required level of flow detention could not be achieved up to 4 days, but the new values for rain intensity (l/s/ha) mean that maximum volume can be achieved at lower outflows. This results in a lower detention volume being required than before at extremely throttled outlets where the design rain duration is ≥ 24 hours.

Automatical calculation of studied flow (l/s) from input share…

27 March, 20193 April, 2019

Automatical calculation of studied flow (l/s) from input share of the yearly runoff volume.

Before, different values of the studied flow were tested in the box Design flow until it resulted in a certain share of the yearly runoff volume. A new function has now been created which automatically calculates the flow for a given share. This is done by clicking on a symbol to the right of the Design flow box. In the form that is then opened, you fill in the share by which the flow is automatically calculated and will be entered in the model’s box Design flow.

Normally, the studied flow is set to include 90% (80-90%) of the yearly runoff volume.

New standard concentrations and revised min and max reduction…

21 March, 2019

New standard concentrations and revised min and max reduction efficiencies

– Reduced standard concentrations for phosphorus from Meadows and Woodland and meadows after comparing with other land uses.

– Revised min and max treatment effects of various types of treatment facilities for certain substances after an investigation of all values. The revisions are reported in the database.

These changes apply to new projects created from 2019-03-21. The changed values are also displayed in the updated database. You can enter the values for the standard phosphorus levels manually in existing projects.

Relase notes v19.1.2

10 March, 201910 March, 2019

Relase notes v19.1.2

Revision of standard concentrations for phosphorus (P)

Updated values for phosphorus for several land uses:
– reduced for e.g. terraced house area and multi-family area.
– increased for roof, yard area within block and park grounds.

Management of existing or planned actions upstream is added.

Area on watershed area upstream
A new input field for areas upstream has been added to the “Recipient data” box.
Affects only the area’s acceptable load (Lacc,area) and listed as Arec.ext “Extra catchment area upstream (ha)”

Cost model in StormTac data base

25 February, 2019

Cost model in StormTac data base

A cost model for all designed facility types is now available in Stormtac database, with references and a large number of facility details, e.g. pipes, wells (drain inlets), plants (vegetation), filling materials, shafts and pumping stations. These can be cost-calculated at a general level, without regard to site-specific conditions.

Standard, minimum and maximum costs are calculated based on input data in the form of number, length, area (m2) or volume (m3). The calculation is performed directly in the database.

Updated and revised function of studied flow and its…

13 February, 2019

Updated and revised function of studied flow and its share of calculated yearly runoff volume

The new function is more advanced and gives more accurate results of the share of total annual volume of stormwater included in both small, medium and high reduced flows (l/s/ha,red). By specifying a studied flow, this proportion is obtained which is now also based on new input data. The resulting rain depth is now also calculated and presented in the results report.

Updated standard concentrations for the following land uses

12 February, 2019

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

29 November, 2018

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

8 October, 2018

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

14 September, 201814 September, 2018

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.