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.