Infiltration trenches in Kungsbacka, Sweden

General

National Id:

Sweden_02

Site name:

Kungsbackaån catchment area, Kungsbacka

Summary:

The study is carried out by flow weighted sampling at the inlet and outlet of one infiltration trench in Kungsbacka south of Gothenburg, located under the parking lot of a supermarket. The observations and sampling were conducted during April to June 2012 and the results from five storm events were analyzed.

NUTS Code:

Västsverige

RBD code:

SE5

Transboundary:

Data provider:

Mats Ivarsson, Enveco

Source(s):

Pollutant Removal Efficiencies and Flow Detention of Infiltration Trenches

NWRM(s) implemented in the case study:

Infiltration Trenches

Longitude:

12.069297

Latitude:

57.514515

Site information

Climate zone:

cool temperate moist

Mean rainfall:

900

Mean rainfall unit:

mm/year

Average temperature:

Mean runoff:

500

Mean runoff unit:

450 - 600 mm

Average runoff coefficient:

0,560000002384186

Type:

Actual Test Site

Light or indepth?:

Light

Monitoring maintenance

Monitoring impacts effects:

Performance

Performance impact estimation method:

Laboratory

Performance impact estimation information:

The experimental procedure consisted of stormwater sampling at the infiltration trench in Kungsbacka. Five storm events from April to June, in 2012, have been analysed. After sampling, water quality analyses have been performed; such as heavy metals, total suspended solids (TSS), volatile solids (VS), total inorganic nitrogen (TIN) and phosphate-phosphorous (PO4 3-). The pollutant removal efficiencies have been determined using a mass balance approach, based on flow-weighted samples collected from the inlet and the outlet of the infiltration trench. Moreover, Event Mean Concentrations (EMC) have been calculated for each storm event. The flow detention of the infiltration trench has been measured by flow meter devices installed at the inlet and outlet of the infiltration trench and the results are presented as hydrographs. Based on the observed detention characteristics, the flow detention function has been evaluated and compared to the design capacity.

Biophysical impacts

Information on retained water:

The infitration trench and associated retention pond can therorethically contain 243 m3.

Information on increased water storage:

The therorethical maximum volume stored per area equates to 202,5 m3/ha.

Information on runoff reduction:

The maximal allowed discharge of stormwater from the parking lot and area for loading to the stormwater ponds is 15 l/s of detained flow

Water quality overall improvements:

Positive impact-WQ improvement

Information on Water quality overall improvements:

Reduction in discharge of nutrients and hazardous substances

Soil quality overall soil improvements:

N/A info

Lessons, risks, implications...

Key lessons:

The pollutants; suspended solids, heavy metals, nitrogen and phosphorus were analyzed. The results show that the pollutant concentrations of the inlet are in accordance with typical stormwater pollutant concentrations in Gothenburg and the outlet mean concentrations are below the compared discharge guideline values. The results also show that the infiltration trench has an average removal efficiency of 80% for suspended solids, approximately 50% for total inorganic nitrogen and all removal efficiencies for heavy metals wereover 50%. Zinc, lead, copper and chromium have removal efficiencies of 70-80% while cadmium and nickel have removal efficiencies of 50-60%. The observed flowhydraulics showed good flow detention since the outflow hydrographs were generally significantly lower than the inflow hydrographs for all storm events.

Success factor(s):

Type	Role	Comments
Existing technical standards	main factor

Financing:

Type	Comments
Private funds

Barrier:

Driver:

Type	Role	Comments
Legal obligations	main driver	In Sweden, the responsibility for adressing the issue of storm water is delegated to the municipalities. The actions are regulated in a number of policy frameworks; the Swedish environemntal code, containing the national implementation of WFD plus a number of other national regulations, the Plan and buildning act regulating the planning process which also covers stormwater issues, the Swedish Road act and the Water services act.

Socio-economic

Direct benefits information:

There are no monetary valuation of the direct benefits accruing from the infiltration trench available. Qualitatively, the direct benefits can be described as reduced risk for flooding of the parking lot in connection to the supermarket, and adjacent areas, during events of extreme precipitation.

Ancillary benefits information:

The aditional benefits from this measure are connected to reduced eutrophication in the Kungsbackaån and in the coastal water receiving the river discharge, strengthened biodiversity in both the Kungsbackaån and in the coastal water due to reduced discharce of pollutants and harmful substances. Positive effects can also be anticipated on cultural ecosystem services such as recreation in the affected areas.

Costs investment:

19255

Costs investment information:

The figure is an estimate based on the proxy 700 SEK/m3 (79,2 €/m3) from the Swedish consultancy firm Norconsult (À-Prislista Markarbeten, Gothenburg 2010-06-01: Norconsult 2010)

Costs operation maintenance:

1925

Costs operation maintenance:

The general estimation is that the maintenance costs are ranging between 5 and 20 percent of the construction costs. The value in the field represents 10% of the construction cost.

Costs total:

19255

Costs total information:

Maintenance costs are not included.

Ecosystem improved biodiversity:

Information on Ecosystem improved biodiversity:

Reduction of nutrients and hazardous substances will improve the overall ecological status in Kungsbackaån and the coastal water receiving the river discharge.

Ecosystem provisioning services:

Ecosystem impact climate regulation:

Not relevant for the specific application

Policy, general governance and design targets

Policy description:

The main function of infiltration trenches is to control the stormwater flow and to reduce the pollutant load of the stormwater. The measure targets the WFD pressure 2.1 Diffuse - Urban run-off by reducing the discharge of nutrients and hazardous substances carried by stormwater.

Part of wider plan:

Policy pressure:

Policy requirement directive:

Policy impact:

Policy wider plan:

Policy area:

Policy area type	Policy area focus	Name	Comments
Primary	Water Policy - WFD	Stormwater, policy and guidelines

Policy target:

Target purpose
Peak-flow reduction
Pollutants Removal

Design & implementations

Application scale:

Plot

Lifespan:

Age:

Performance timescale:

Immediate

Area (ha):

1,20000004768372

Design capacity description:

Maximum volume of stormflow that can be retained is 243 m3. Studies from the Swedish road administration and others show show that reduction (%) of pollutants in infitration trenches varies according to: TSS 50-90, TP 10-50, TN 55-84, Zn 15-90, Cu 10-90, Pb 30-80, Cd 10-50, Oil and Greas 100, BOD COD DOC 89-93, Bacteria 90, NOx 82.

Constraints:

Null

Favourable preconditions:

The measures was constructed as part of the development of the industrial and commersial area.

Design contractual arrangement:

Design consultation activity:

Design land use change:

Design authority:

Authority type	Role	Responsibility	Name	Comments
Other	Initiation of the measure		The municipality of Kungsbacka

Last updated: 12 Jan 2015 | Top

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Infiltration trenches in Kungsbacka, Sweden

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