Ecological adapted stormwater treatment in Kretinga town, Lithuania
Year of issue
2025
Summary
Kretinga is located 12 km east of the popular Baltic Sea resort town of Palanga, and about 25 km north of Lithuania's 3rd largest city and principal seaport, Klaipėda. The Stormwater Special Plan developed introduces a new approach towards more sustainable stormwater solution from an environmental perspective. This type of ecologically adapted stormwater investments have been implemented in Lithuania for the first time. If they function as well as predicted and can be disseminated through appropriate channels, there should be good possibilities to introduce similar investments in other Lithuanian towns.
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Location
55.8897, 21.24267
Project
NWRM
National ID
Lithuania_02
Sector
Hydromorphology
Installation Date
2013
Overview
Location of the project
In the southern part of Kretinga town, Lithuania, near the Akmena-Danė River, close to the main road Šiauliai–Palanga (Route A11).
Country
Lithuania
NUTS2 Code
Latvija
Sponge measures implemented in the case study
Basins
Objectives
1) reduction of formation and collection of stormwater;
2) reduction of the amounts of stormwater, centrally discharged into the environment;
3) reduction of pollution levels in stormwater;
4) ensure that stormwater is managed separately form domestic, industrial.
2) reduction of the amounts of stormwater, centrally discharged into the environment;
3) reduction of pollution levels in stormwater;
4) ensure that stormwater is managed separately form domestic, industrial.
Involved partners
| Authority type | Authority name | Authority role | Comments | Authority responsibility |
|---|---|---|---|---|
| Local water authority | Kretinga town municipality | Initiation of the measure | — | Responsible |
| Research institute / University | Baltic Coastal Research and Planning Institute | Monitoring | Baltic Coastal Research and Planning Institute is a division of Klaipėdos university | Supporting |
| Local water authority | Kretinga WWTP | — | — | — |
| National water authority | Environmental Protection Agency of Lithuania (AAP / AAD) | Monitoring | Carries out inspections and environmental quality assessments (e.g. after overflows or pollution incidents). | Supporting |
Site Information
Climate Zone
Cool temperate moist
Temperature (°C)
8.90 °C
Elevation range
27
WFD Ecological status
Moderate
WFD Chemical status
Unknown
Design and Implementation
Project scale
Micro
Project scale specifications
This project is implemented at the city-district level within Kretinga town and focuses on the treatment of stormwater from a specific urban catchment (18 ha) using ecological infrastructure such as retention ponds and vegetated zones. It addresses localised water quality and urban runoff issues and does not extend to a regional or river basin scale.
Project area
18
Area subject to Land use change or Management/Practice change (ha)
18.00 ha
Size
100.00
Size unit
m
Basis of design
Planned water retention time in the ponds is ~ 48 hours; under heavy rains, the time can be ~ 24 hours.
Constraints
1) some planning constrains regardin local cultural ceritage, but problem solved; 2) there were some problems with planning paths for leasure zone near retention ponds, as there are building restrictions in such wastewater treatment areas, but the problem was successfully solved.
Financing
Costs investment
188000.00 €
Costs investment information
Cost effectiveness estimations have not been calculated. It would be interesting to compare e.g. construction and operation costs of wetland/retention pond (such stormwater treatment facilities are under construction in Kretinga town) with conventional oil-sludge separator, taking into account removal of pollutants per unit costs.
Evaluations will be carried out of the decrease of nutrients (P and N), hazardous substances, suspended solids and BOD from stormwater outlets after the construction of the treatment facilities.
Evaluations will be carried out of the decrease of nutrients (P and N), hazardous substances, suspended solids and BOD from stormwater outlets after the construction of the treatment facilities.
Compensations
No
Policy and Governance
Policy description
The measure was designed to address the problem of untreated urban stormwater runoff being discharged directly into the Akmena-Danė River, carrying high loads of pollutants such as sediments, nutrients, heavy metals, and pathogens. Rapid urban development in Kretinga had increased impermeable surfaces, leading to higher runoff volumes, reduced infiltration, and elevated risks of water pollution and ecological degradation in the river system. The project aimed to reduce these impacts through nature-based stormwater treatment solutions.
Land ownership
The land used for the stormwater treatment system in Kretinga is publicly owned, under the authority of the Municipality of Kretinga.
Policy targets
Oher Societal Benefits
Runoff control
Peak-flow reduction
Pollutants Removal
Part of a wider plan
Yes
Wider plan
| Name | Comments |
|---|---|
| Kretinga town special plan | Local scale plan, including all the town focuses |
Public consultation
Yes
Has contractual arrangements
Yes
Contractual arrangements
| Arrangement type | Responsibility | Name | Role | Comments |
|---|---|---|---|---|
| Contractual agreement | Supporting | SWECO | Implementation | Technical project |
| Contractual agreement | Supporting | GreenWorks Indusrty | Implementation | Construction |
Impacts and Monitoring
Monitoring System
Monitoring requirements
The system is subject to monitoring by Kretingos Vandenys and national environmental authorities to ensure compliance with pollutant reduction goals and regulatory standards.
Monitoring parameters
The monitored parameters focus on water quality and pollution control, including suspended solids, total phosphorus, total nitrogen, and heavy metals such as cadmium, copper, lead, and zinc. Microbiological indicators like pathogenic bacteria (e.g., E. coli) are also monitored. During overflow or pollution incidents, additional parameters such as biological oxygen demand (BOD), chemical oxygen demand (COD), and ammonium nitrogen are assessed to evaluate environmental impact. These data help guide both routine maintenance and responses to extreme weather events or illegal discharges.
Maintenance
Maintenance requirements
Regular maintenance is carried out by Kretingos Vandenys, including sediment removal, vegetation management, and inspection of stormwater infrastructure.
Impact Assessment Methodology
Performance impact assessment method
Edge of Field/Plot
Performance impact estimation information
Estimated reduction of contaminants in the designed and constructed facilities:
1) SS 80 percent.
2) Total phosphorus 50 percent.
3) Total nitrogen 30 percent.
4) Metals cadmium, copper, lead and zinc †“ 50 percent.
5)Pathogenic bacteria 70 percent.
1) SS 80 percent.
2) Total phosphorus 50 percent.
3) Total nitrogen 30 percent.
4) Metals cadmium, copper, lead and zinc †“ 50 percent.
5)Pathogenic bacteria 70 percent.
Socio-economic Impacts
Direct benefits information
Improved public health and safety
Enhanced aesthetic and recreational value
Cost-effective pollution reduction
Increased local awareness and institutional capacity
Enhanced aesthetic and recreational value
Cost-effective pollution reduction
Increased local awareness and institutional capacity
Biophysical impacts: Hydrology
Retained water
7776.00
Retained water unit
m3/day
Information on retained water
90 l/s in total (40 l/s in one and 50 l/s in another retention pond)
Information on increased water storage
The design mimics natural wetland processes, creating small aquatic zones and vegetated basins that act as temporary storage.
Biophysical impacts: Biodiversity
Improved biodiversity
Yes
Information on improved biodiversity
The project created new vegetated and aquatic habitats in a previously sealed urban environmentHowever, no quantitative data on flora or fauna diversity, abundance, or ecological indices is available.
Biophysical impacts: Water & Soil Quality
Water quality overall improvements
Positive impact-WQ improvement
Information on water quality overall
Due to natural sedimentation, filtration, and biological processes in the retention ponds and vegetated treatment areas.
Water quality improvements - Phosphorus (P) - Unit
% reduction pf pollutant
Water quality improvements - Nitrogen (N)
30.00
Water quality improvements - Nitrogen (N) - Unit
% reduction pf pollutant
Water quality improvements - Total Suspended Solid (TSS)
80.00
Water quality improvements - Total Suspended Solid (TSS) - Unit
% reduction pf pollutant
Water quality improvements - Copper (Cu)
50.00
Water quality improvements - Copper (Cu) - Unit
% reduction pf pollutant
Water quality improvements - Zinc (Zn)
50.00
Water quality improvements - Zinc (Zn) - Unit
% reduction pf pollutant
Water quality improvements - Escherichia Coli (E.coli)
70.00
Water quality improvements - Escherichia Coli (E.coli) - Unit
% reduction pf pollutant
Water quality improvements - Faecal Coli (F.coli)
70.00
Water quality improvements - Faecal Coli (F.coli) - Unit
% reduction pf pollutant
Biophysical impacts: Others
Information on ecosystem impact climate regulation
The vegetated stormwater system contributes to urban cooling, carbon capture (vegetation), and increased evapotranspiration, but again, no quantified estimates are available.
These impacts are assumed as typical co-benefits of nature-based stormwater solutions, but not specifically measured here.
These impacts are assumed as typical co-benefits of nature-based stormwater solutions, but not specifically measured here.
Lessons Learned
Key lessons
1) reduction of formation and collection of stormwater, for example installation of impervious surfaces shall be avoided (except in potentially polluted territories), clean stormwater absorbing soil facilities should be installed, projected areas of potentially polluted territories shall be as small as possible, etc.,
2) reduction of the amounts of stormwater, centrally discharged into the environment, e. g. allow utilization of stormwater in the production process, watering of green areas, fire extinguishing, etc., and
3) reduction of pollution levels in stormwater, e.g. implement dry cleaning of potentially polluted territories, construct sheds in most hazardous areas.
4) Capacity must be resilient to extreme weather events. An overflow incident in 2023, due to intense rainfall, resulted in the discharge of untreated water. While no major environmental damage was reported, it highlighted the vulnerability of even ecological systems under climate-induced extreme events, and the need for emergency capacity and adaptive infrastructure.
2) reduction of the amounts of stormwater, centrally discharged into the environment, e. g. allow utilization of stormwater in the production process, watering of green areas, fire extinguishing, etc., and
3) reduction of pollution levels in stormwater, e.g. implement dry cleaning of potentially polluted territories, construct sheds in most hazardous areas.
4) Capacity must be resilient to extreme weather events. An overflow incident in 2023, due to intense rainfall, resulted in the discharge of untreated water. While no major environmental damage was reported, it highlighted the vulnerability of even ecological systems under climate-induced extreme events, and the need for emergency capacity and adaptive infrastructure.
Drivers
| Driver type | Comments |
|---|---|
| Legal obligations | Might be also other reasons, but the stormwater discharge in Kretinga town did not in some parameters comply with the pollution requirements before the construction of the two retention ponds |
Success factors
| Success factor type | Success factor role | Comments |
|---|---|---|
| Attitude of decision makers | Main factor | — |
| Financing possibilities | Main factor | EU funding was a big help. |
| Available support tools | Main factor | During the MOMENT project, it was possible to gain knowledge about the similar retention ponds in Sweden. As this was one of the first (pilot) retention ponds in Lithuania, therefore, knowhow was very usefull. |
| Legal obligations | Main factor | — |
Transferability
This measure is highly transferable to other urban areas facing stormwater pollution, especially in small to mid-sized towns. Its success depends on strong local governance, public utility involvement, and integration with land use planning. Key aspects to watch include illegal drainage connections, maintenance capacity, and resilience to extreme rainfall, which can undermine system performance if not properly addressed.
Sources
Sources