Step 1
The purpose of the first phase of the project is to study stormwater formation in selected target areas.
The work involves flow and quality measurements and analysis of stormwater samples in cooperation with the environmental laboratory. The suitability of the measurement point for practical measurement arrangements is taken into account when selecting the sites. During the study, possible emission sources and their impact on stormwater in the formation area are investigated.
Research topics
The research target for spring 2023 is two different stormwater formation areas and discharge points (water bodies where stormwater ends up). In addition to the research target areas, comparative data will be collected more widely from different areas and city districts.
Area 1
Stormwater generation area 1 is approximately 25 hectares in size. Stormwater from the area is channeled through a stormwater drain into an open ditch, from where the water is further directed into Kirkkojärvi.
The stormwater drainage system in the area covers the small industrial area of Hevoshaa and part of the city center. One of the city's entrance routes passes through the area, so traffic is quite busy. There is a fuel distribution station along the road. The small industrial area includes, among other things, a car wash, a tire shop, a volunteer fire department station, shops and various warehouses.
Area 2
The extent of formation area 2 is approximately 420 hectares and extends from the forest and field area north of the motorway all the way to Savilahti (bay of the sea). There is a busy road area and a train track along the ditch. A small waste station and a sports centre are also located in the area.
Stormwater flows along open ditches, through the culverts under the motorway to the residential areas of Ruissalo and Salmenkylä, and discharges through a large open drain into Savilahti, near the Salmenvirta swimming area.
Implementation and results of the work
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Phase 1 studies were conducted between April 13 and July 4, 2023.
Handheld meters were used to measure the general quality of stormwater, measuring pH, temperature, electrical conductivity, salt, solids and ORP (or reduction potential). The purpose of the measurements was to collect information on water quality in different areas and look for possible deviations.
The spring measurement results were mostly very similar at different measurement points. However, some deviations were observed and measurements were continued in the autumn until the waters remained thawed.
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For more detailed laboratory analyses, water samples were taken twice from two different discharge ditches. In addition, samples were taken from water bodies (Kirkkojärvi wetland and Salmenvirta beach). The substances to be analyzed were selected in cooperation with an expert from the environmental laboratory.
The concentrations of pollutants in stormwater samples examined from various points were clearly below the minimum guideline values set by Stockholm County and the environmental quality standards specified in the Government Decree (Vn 1022/2006).
The results were also compared to values measured in the central areas of Helsinki, Lahti and Espoo. Similar pollutants occur in urban waters, but concentrations are generally higher in large cities. In the Hamina results, only the May sample of the open channel discharging into the Salmenvirta River (measuring point 2_1) nitrogen and nickel content exceeded the average concentrations in large cities. An explanatory factor may be the extent of the catchment area of the Hamina sampling point, which also extends into agricultural and forestry areas.
The results of samples taken from the discharge water bodies (Salmenvirta and Kirkkojärvi) were compared with a seawater sample from Paksuniemi, which was taken in the summer of 2021. The samples from Salmenvirta and Kirkkojärvi copper content was slightly higher than in the Paksuniemi seawater sample. Similarly chemical oxygen demand (COD) and solid were higher than in the sample taken from the harbour front. At the time of sampling in June, the water in Salmenvirta was visually very clear. According to the analyses turbidity number At that time, the FTU was 4,1 (FTU 1-5 slightly turbid, not visible to the eye). In the Kirkkojärvi sample, the turbidity number was 8,3 (FTU 5-10 slightly turbid). The FTU of clear water is less than 1.
The quality data of the discharge water bodies were also compared with the results of seawater research from Hamina Bay, which are available in the annual publications of the Kymijoki Water and Environment Association. The seawater research in Hamina Bay monitors water visibility depth, turbidity, electrical conductivity, oxygen content ja nitrogen and phosphorus concentrations. Research is carried out during the winter season in February-March and the growing season in May-September. Compared to the surface water of Hamina Bay, the water of Salmenvirta and Kirkkojärvi is turbid and nitrogen and phosphorus concentrations are clearly higher. In the outer Hamina Bay, the seawater contains more salts, which is reflected in higher electrical conductivity.
Laboratory analysis provides information about the quality of the stormwater sample at the time of sampling. Therefore, stormwater quality should be monitored systematically over the long term. One of the goals of quality studies is to develop a sampling plan according to which stormwater quality could be monitored in the future.
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In the spring, we also tested the Drone purchased for the Land Use Unit. The drone provides high-quality video and image material that can be used, for example, to examine runoff routes at different times of the year.
