Completed database with updated stormwater concentrations during different seasons…

Completed database with updated stormwater concentrations during different seasons and months

The sheet “Monthly and seasonal conc” already presents 5 case studies with flow-weighted sampled concentrations every month for a year, which is considered unique. These have now been adjusted with additions for total concentrations and an introductory table that presents calculated average percentages of total annual concentrations that a month or season gives.

Examples of use:

A stormwater sampling has taken place during the summer and it is desired to get an estimate of which annual average concentrations this corresponds to, taking into account whether there are higher or lower concentrations during the summer than the annual average. Based on the percentages in the table (e.g. 117% of P during the summer compared with the annual average), it is possible to roughly (!) calculate which annual average concentration the sampled concentrations are deemed equivalent, e.g. which annual average concentration of the sampled concentration 120 ug/l P corresponds to as annual average value.

These recalculated annual average concentrations, e.g. 120 / 1.17 = 103 ug/l, can then e.g. be used in StormTac Web to replace estimated values ​​from the area where sampling took place. Then these can be used to calculate pollutant loads, design treatment facilities, etc., taking into account the site-specific conditions. This presupposes that the sampling took place in proportion to the flow with a sufficient number of collected samples (we recommend at least 7 samples).

Updated database regarding new references, stormwater concentrations, reduction efficiencies…

Updated database regarding new references, stormwater concentrations, reduction efficiencies and concentrations for overflow water

There is now an updated version of StormTac’s database with a lot of new data from a large number of new references. Several sheets have been updated with new data, which means a larger basis for the development of new typical concentrations for stormwater, treatment effects and concentrations for overflow water. The work of producing new typical concentrations and treatment effects from this data is in progress. Recently, the typical concentrations of TBT and the treatment effect of phosphorus (P) from ponds were changed. More changes are planned in the near future, first regarding irreducible (minimum possible outlet) concentrations and typical concentrations for different land uses.

Updated database with a large number of new volume-weighted…

Updated database with a large number of new volume-weighted land-use specific concentration data and BMP reduction efficiencies

Introduction
StormTac’s database has been updated with a large number of new volume-weighted concentrations (ug/l) and treatment effects (%) from various references (case studies), not least from all data that is considered to be reliable from the recognized International Stormwater BMP Database, http: // www.bmpdatabase.org/. Many other reference data have also been entered after an extensive literature study focused on finding data for substances and land uses as well as types of treatment facilities where there was previously a lack of data in StormTac’s database.

Only flow-weighted data has been entered, thus excluding grab sample data. Concentration data from base flow from different land uses have also been added to StormTac’s database, after volume weighting from obtained raw data from various case studies.

The references for runoff coefficients have also been updated and more clearly divided between volume runoff coefficients and design runoff coefficients. A large number of new case studies with data of irreducible concentrations (outlet concentrations) has been added.

For the case studies with data from treatment facilities, various site-specific parameters that affect the treatment effect have also been compiled, e.g. data on filter material and hydraulic conductivity for biofilters.

This data should now be used to update the typical land-use specific concentrations and calculated treatment effects in StormTac Web.

Data from BMP Database
Data from hundreds of stormwater treatment facilities (BMPs) from the International Stormwater BMP Database of a wide variety of types have been processed by transferring them from Access to Excel and by performing a volume-weighted calculation of both inlet and outlet concentrations from all runoff events, after which volume-weighted treatment effects were calculated for a large number of substances and types of stormwater facilities. To our knowledge, this calculation has not been performed and compiled in any other database or documentation. A quality assurance has been carried out by studying extreme values whereby uncertain data were marked or removed. In cases where the inlet concentrations come from areas with single land uses, these data are used as typical land-use specific concentrations, which are added to the database.

Examples of interesting new data are that treatment effects from Storm drainage filter (catch basin inserts) were expanded from 5 to 10 case studies and data from underground retention filter basins were expanded from 5 to 16 case studies. This provides a much more secure basis for calculating the treatment effects in StormTac Web. Facility types that you may not have previously dared to use in a project due to uncertain data, may now be able to start using as more data is available which shows the treatment effect that can be achieved for different types of treatment facilities.

Site-specific parameters
For the case studies with data from treatment facilities, various site-specific parameters affecting the treatment effect have also been compiled for further updating of the treatment effect calculations in StormTac Web. Examples of such parameters are permanent water surface, the catchment area and runoff coefficient, water depth for different facilities of different types as well as information on filter material and hydraulic conductivity for biofilters.

Update of typical land-use specific concentrations
For the many added typical concentrations per land use, this will provide a base for continued update of typical concentrations for different land uses, after an analysis and comparison of data from different similar land uses.

Availability
The many added typical concentrations from different land uses are available to everyone, but data in the form of baseflow concentrations, runoff coefficients and treatment effects (%) from different types of stormwater facilities are only available to those licensed on StormTac Web.

Extent
Through this update, StormTac’s database includes all relevant compiled and volume-weighted data from the large international databases NSQD and BMP database for concentrations and treatment effects for stormwater and stormwater facilities, respectively. The aforementioned databases contain all raw data from all rain events, but StormTac’s database is now probably the most comprehensive database of calculated volume-weighted compiled data per land use and facility type. The other databases contain only raw data, while these raw data are volume weighted and compiled into StormTac’s database, broken down by substance, land use and facility type.

Continued evaluation of data and updating of the database
The data can already be used to further study uncertainties by substance, land use and type of treatment facility, where these concentrations and treatment effects are used in projects. During the fall of 2020, StormTac will use this data to update the land-use specific typical concentrations of stormwater and baseflow per land use. StormTac will also, based on added data and site-specific parameters, update the calculations of treatment effects for all types of treatment facilities, taking into account more site-specific parameters, such as hydraulic conductivity and material in biofilters, for the parameters and substances where sufficient data is available.

Together with Luleå Technological University (LTU), the quantification of uncertainty of calculated concentrations and quantities of pollutants and treatment effects will be improved and performed specifically per substance based on compiling relative standard errors from all reference data. A second international scientific paper on quantification of uncertainty has been started in collaboration with LTU for scientific review of the calculations and used data.

During the summer and autumn 2020, the database will be converted to a web application available from the website and fully integrated into StormTac Web.

Updated method description

Updated method description

General method description for StormTac Web has been updated on this homepage and more detailed in the guide to the application, incl. addition of a new introductory chapter.

The description of quantified uncertainty has been updated incl. added equations in the guide.

Description of the recipient model has been updated, incl. a section on calculating new distributed acceptable load and on how to calculate acceptable load for e.g. urban areas and agricultural land, which provides the opportunity to distribute the treatment needs to several actors (the Transport Administration, municipalities, operators, etc.). The distribution of the treatment needs is based on the amount of pollutant load the individual operator contributes to in the catchment area.

Improved function for calculating distributed acceptable load on receiving…

Improved function for calculating distributed acceptable load on receiving waters

Previous method in StormTac Web of producing distributed acceptable load (kg/ha/year), for the watershed to the recipient, has meant that the recipient’s acceptable load (kg/year) has been distributed over the total area (ha) of the watershed area. The new method is based on the fact that the distributed acceptable load is instead based on the recipient’s treatment needs (kg/year), the total load on the recipient (kg/year) and the area of the watershed area (ha).

It is the pollution load via the drainage (such as stormwater and baseflow) that stormwater measures refer to and therefore the new calculation of distributed acceptable load (kg/ha/year) is based on the total load via only stormwater and baseflow from the watershed area, and does not include the part that comes as direct atmospheric deposition on the recipient surface and not as the part of the groundwater that flows directly into the recipient.

The improved function and description in the guide provides the opportunity to distribute the treatment needs to several actors (the Transport Administration, municipalities, operators, etc.). The distribution of the treatment needs is based on the amount of pollutant load the individual operator contributes to in the catchment area.

 

Improved functions for quantification of uncertainties after scientific review

Improved functions for quantification of uncertainties after scientific review

The revised and improved functions are the result of ongoing work in collaboration with Luleå Technical University with a scientifically reviewed publication on quantification of uncertainties in the StormTac Web application (Wu et al., 2020). The features use a method based on The Law of Propagation of Uncertainties (Taylor, 1994), where absolute uncertainties are calculated from relative uncertainties. This is described in the guide, with reference to the publication (Wu et al., 2020) for more detailed description.

The improvement uses a new function when different values are summed, which reduces uncertainty, while a multiplication gives increased uncertainty, according to a scientifically reviewed paper by Hedbrant and Sörme (2001). This new breakdown using different equations gives changed resulting relative uncertainties for total flow, total load and total concentration before and after treatment, respectively, with consequent changes in calculated absolute uncertainty.

As before, various absolute uncertainties for different substances are obtained, but based so far on assumed relative general uncertainties for concentrations and runoff coefficients from literature values. However, there is a continued collaboration with Luleå Technical University to develop specific uncertainties that take into account the uncertainty in concentrations for each substance and land use from StormTac’s database, as well as for runoff coefficients per land use. That work will be described in a new paper that will also be scientifically reviewed. Implementation of this more advanced uncertainty model is expected to take place within a few months.

18th of March, at the conference VAK2020 Jönköping

18th of March, at the conference VAK2020 Jönköping

Come and meet four of us, on the 18th of March, at the conference VAK2020 (Vatten avlopp kretslopp) in Jönköping, Sweden. There you get the opportunity to ask us questions about StormTac Web and see us show the application live. We will be in Monter 35. Hope to see you there!

/StormTac Team

Updated land-use specific runoff coefficients per land use

Updated land-use specific runoff coefficients per land use

The volume runoff coefficients and the design runoff coefficients have been investigated through supplementary literature studies and compared, after which revisions of the typical template values ​​and interval values ​​have been performed for some land uses. These changed runoff coefficients have also been compiled in the database.

These adjustments refer to typical recommended values, but both of these types of runoff coefficients can still be changed according to site-specific conditions. This e.g. applies to the land use Forest with increased typical runoff coefficients that have been adjusted after extensive empirical studies in Sweden and the US, but which also show large variations between different locations. More about this can be read in a new section in the Guide, under Design Flow.

In the same chapter there is also news from an international study which indicates that there is no significant relationship between the runoff coefficient and the size of the catchment area, which also means that there is no upper value for the catchment area for employing the rational method in the model, so it can be used without a specific upper limit area, provided that site-specific conditions such as longest runoff transport (concentration) time are carefully considered.

Updated typical concentrations for stormwater and baseflow from road…

Updated typical concentrations for stormwater and baseflow from road areas

Updated (reduced) typical concentrations for stormwater for Hg from the following land uses:

– Office area
– Residential area without road ditches, min
– Residential area without road ditches, max
– Multifamily 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 in a skeletal soil (macadam-soil mixture) without Local disposal of stormwater in the block
– Yard area within block
– Artificial turf field

Updated typcical concentrations regarding all substances and the land uses:
– Local street with curbstones
– Local street after reduction in open ditch.

Updated (reduced) baseflow concentrations from road areas for the following substances:
– N, Zn and Cr.