E1592 V 6 Non Technical Summary

Project Overview

Public Disclosure Authorized The town of Ogulin in northern has long-held problems of wastewater and stormwater treatment and disposal. At present the majority of the households discharge their wastewater without prior treatment into septic tanks or directly into the nearby sinkholes where it enters the local groundwaters. Stormwater drainage is disposed of in a similar manner, and the increase in hard surfaces that has accompanied urbanisation has resulted in not only a considerable increase in the flow of stormwaters, but also in their levels of pollution. Heavy precipitation also commonly results in clogging of sinkholes and local flooding, which in turn impacts on local hygiene, ecology and economy.

The proposed project would involve the establishment of a 13 km trunk sewer and associated branch lines for the collection of domestic and industrial sewage effluent from the town of Ogulin and stormwater from high flood risk area. Effluent from the

Public Disclosure Authorized proposed sewer infrastructure will flow to a new tertiary wastewater treatment plant which will use biological means to treat the sewerage effluent to an acceptable standard before discharge to the groundwater environment via an adjacent sinkhole1. The plant will produce a stabilised sludge, which will be disposed of to an appropriately engineered domestic landfill.

The proposed sewer system and wastewater treatment plant will be developed in a number of stages:

Phase 1: An initial trunk sewer has already been installed to collect stormwater from high risk flood areas of the town. The stormwater effluent will be pumped in phase 2 to the wastewater treatment plant, where it will be treated mechanically via an oil and sand trap before discharge to the adjacent Public Disclosure Authorized sinkhole.

Phase 2: Under this phase further sewers will be built, together with the wastewater treatment plant to allow the treatment of wastewaters to a tertiary standard. The plant will use an activated sludge and membrane filtration methodology before discharge of treated effluent to the adjacent sinkhole. The sewers constructed in phase 1 will be extended in phase 2 to become a partly combined sewerage system.

Subsequent to the commissioning of the phase 2 tertiary treatment plant it is envisaged that further domestic houses and industrial premises will continue to connect to the sewer infrastructure thereby decreasing the regions current reliance on septic tank infrastructure. It is envisaged that during the transition phase contents of septic tanks will be able to be treated in the plant. Public Disclosure Authorized

1 Such solution has been confirmed by exploring the underground and testing ground absorption in abysses, presented in the study “Geomehaniko-geofiziki istrani radovi - ure aj za proišavanje otpadnih voda grada Ogulina“, prepared by “Geokon“, (October 1999, no. E-090-99), as well as by previously prepared studies and tests conducted on the field.

Project Setting

The town of Ogulin is located in the Ogulin-Plaški valley, a hilly area some 300 m above sea level, and rising to 500-600 m in higher elevations. The valley is comprised of two karst fields, the Ogulin and Plaški Fields, made of highly pervious layers of limestone and dolomite, characterized by long cave systems such as the ula’s Precipice- Medvednica Cave complex.

The Ogulin administrative region covers an area of 542 km2, comprising about 15% of the total area of the County of . The town itself belongs to a sparsely populated area of Croatia and according to the 1991 Population Census had a population of some 16,732 people (9.1% of the county’s population). The town’s economy is based primarily on transportation, and, traditionally on forestry and agriculture, although tourism is becoming increasingly important, with the Croatian Olympic Centre Bjelolasica and Lake Sabljaci located nearby.

Ogulin lies within the catchment of the River, which flows into the town from the west in a deep gorge, before sinking underground in a large sinkhole, known locally as the ula ponor. Once underground, the river flows through an extensive cave system before emerging approximately 4km to the north-east and flowing in a general north-easterly direction towards Karlovac, approximately 40km distant. The area is considered highly sensitive and the potentially grave consequences of local pollution mean that the construction of the sewerage system and wastewater treatment works have been long been a priority of the town. In addition, and approximately once per year after intense rainfall events and Spring snow melt, the capacity of the Dobra sinkhole is insufficient to cope with the high river flows generated, resulting in flooding of the town centre.

With the exception of the drainage features associated with the Dobra River, the surface drainage network tends to be poorly developed due to the permeability of the surface soils and underlying bedrock. Less intense rainfall tends to infiltrate the ground rapidly, where it causes dissolution of the carbonate substrata and results in the formation of dissolution features and the typical karst topography. As a result, most of the drainage infrastructure within the town, such as from rooftops and highways, has historically been to soakaway, and emerges as springs in the valley of the Dobra River, although some is also known to emerge in the valley of the Mrenica River, to the south-east.The current discharge of wastewater and sewage to solution features, is reflected in the water quality of the main springs around the town, which show evidence of high concentrations of faecal bacteria2.

Croatia is amongst one of the most biologically rich countries in Europe and supports an unusually high concentration of endemic species, with the karst ecosystems considered especially valuable. The aquatic habitats within the system support a unique flora and fauna with several endemic species of fish, invertebrates and amphibians of particular note (for example some 11 species of fish are known to live

2 Data from five of the main springs located in the vicinity of the town (ica, Bistrac, Peina, Gojak and Kukaa) indicate consistent contamination by faecal coliforms, at times in excess of 2400 counts/100ml. As these bacteria do not live long outside the gut, the data also suggest a relatively rapid transportation of the contamination from ground surface to the spring sources (ie of the order of a few days only), consistent with groundwater movement through mature karst systems. only within the karst region of Croatia, with the cave dwelling species even more unique, diverse and restricted in their range). The flora and fauna of the Karst areas are threatened by numerous activities including the following:

• changes in water regimen (drainage, regulation of watercourses, etc.) • physical changes (eg. backfilling or natural overgrowing, particularly related to smaller wetland habitats) • biological changes (excessive exploitation of certain resources or introduction of foreign species) and • pollution of watercourses.

The proposed wastewater treatment plant would be located within an area of secondary regrowth and ephemeral scrub3 at the outskirts of the town. The designated land is within a state-owned area of the “Krpel” hunting-ground, a large area of some 3000 ha of forest and agricultural land which supports such species as deer, boar, brown bear, hare, partridge, duck, pheasant fox, badger, pine marten, and polecat. The scrub habitats present at the proposed WTW site are however common within the Ogulin area and not considered to be of significant ecological value and no uncommon species have been recorded from the site itself.

3 the invasive plant species Japanese Knotweed was also present on several areas of the site, and should be controlled during construction Project Impacts & Mitigation

Impacts arising during construction of the sewerage network and wastewater treatment plant will be primarily restricted to nuisance impacts (including noise, dust, traffic impacts) as well as physical impacts. Careful planning and scheduling of the works will be used to minimise such impacts, whilst project design (eg drainage profiling) has been undertaken for optimal functionality and minimal impact, including protection of neighbouring facilities from physical damage and planning of post construction environmental restoration.

During operation, the properly ventilated sewerage systems should have no significant adverse impacts. Careful grading of the system and good sewer maintenance will be used to avoid the risk of odours arising from the retention of wastewaters in anaerobic conditions in the pipelines, or from sludge deposition within the pipelines arising from low wastewater flows. The engineering design has also been undertaken to avoid the need for overflow disposal of rainwaters under general storm conditions, and care has also been taken to design protection of concrete and equipment from the corroding effect of aggressive wastewater.

Potential impacts arising from the operation of the wastewater treatment plant are likely to be limited to the following: liquid wastes, solid wastes, odours and noise impacts. The key environmental mitigation for the operational WWTP has been the development of an adequate engineering design, and the siting of the plant at the outskirts of the town. Specific issue mitigation is proposed as follows:

• Water Quality: The aquatic ecology of the caste ecosystem is both unique and fragile, and local water resources are highly valued. The operation of the plant will greatly improve existing conditions, and the acceptable effluent standards has been set by the regulators with regard to the high sensitivity of the receiving environment. These stringent requirements have in turn dictated the selection of the wastewater treatment technology required to achieve the tertiary levels of treatment in accordance with the National Water Protection Plan.

• Sludge Disposal. The treatment and final disposal of waste sludges is a potential issue for all wastewater treatment plants, and the selection of an appropriate location for the ultimate sludge disposal is critical to prevent secondary environmental pollution. Waste sludge, has the capacity to bind potentially toxic organic and inorganic substances including heavy metals and organic chemicals and can lead to both bacteriological and chemical pollution of groundwaters. Estimated sludge quantities arising from this project are expected to be small (maximum expected levels are 3.53 m3/d at 20% dry matter) and will be collected and transported (in an enclosed environment to prevent odour issues) on a regular basis to a Class 1 disposal site in line with the Regulations on Waste Handling Conditions. Oils and fats from the fat trap will also be collected in closed storages and transported for incineration, in line with the Regulations on Waste Types.

• Noise. The operational facility will use either compressors or blowers for aeration and this combined with the operation of the various mechanical parts of the plant as well as the “wastewater” medium itself will result in the generation of round- the-clock noise. The use of an enclosed system will however help ensure that permitted daily and nightly noise limit levels of 55 and 45 dBA respectively at the site boundary will not be exceeded.

• Odours. The primary mitigation for odours has been the siting of the plant an adequate distance and downwind from the nearest inhabited areas to reduce exposure. In addition the aeration basins and primary sedimentation tanks have been designed to be covered to reduce emissions, and the sludge will also be treated in enclosed plants. Sludge dehydration and thickening can also be a major source of odours, and the plant has been designed with enclosed facilities, and intensive absorption of waste air. The wastewater sewers and sludge treatment line will remain as potential odour sources however and waste matter from the grid, sand filter and grease trap can also result in odours. To mitigate against the latter such wastes will be removed regularly in enclosed compact units and disposed of at a sanitary landfill.

Hazardous substances in the wastewater can adversely affect the functioning of wastewater treatment works and a long-term functioning break of the biological unit in the plant could result in insufficiently treated water being released into the underground streams. Whilst no significant quantities of potentially hazardous materials (acids, alkalis, etc) will be used during operation of the plant, there is always a risk of hazardous materials entering the wastewater stream as a result of industrial accidents upstream. To avoid such a risk, and in addition to wastewater influent quality being continuously monitored at the plant, all industries and small enterprises connected to the central plant, will be required to have the approval of "Vodovod i kanalizacija" d.o.o. (Water Supply and Sewerage), the company for provision of municipal services, or the manager of the central plant, prior to a potential change in the technological process of individual segments. Local industries will also be required to work out a system of measures to ensure a timely break in draining wastewater toward the Ogulin plant should an accident occur, whilst the stormwater overflow would provide additional protection at the plant. Should any of the units break down due to a partial or complete loss of biological activity, the plant construction using four independent modular technical units (parallel structures), will allow the facility to continue in operation. Automatic backup power generation is also provided, together with a system of permanent monitoring of quality and quantity of inflowing/outflowing wastewater. Environmental Monitoring

During construction and susequent plant operation, it is necessary to follow and monitor the environmental status in order to determine potential unfavourable and undesirable impacts. Monitoring results will be used for possible additional environmental protection measures, in cases of increased quality requirements for parts of the environment, or the inefficiency of planned protection measures.

Surface waters

Surface waters will be monitored at four locations (upstream and downstream of the treated water discharge locations, and at the plant entrance and exit) to ensure appropriate levels of environmental protection and ensure that the plant is operating efficiently. Surface water monitoring will also be carried out at the spring sources identified at the tracer tests and the plant will liaise with Croatia Water with regard to the monitoring of river water quality on the Dobra River downstream of Ogulin. Indicators will include: • water flow (m3/s) • water temperature (°C) • pH • dissolved oxygen (mg O2/I) • dissolved matter (mg/l) • five-day biochemical oxygen demand (mg O2/I) • chemical oxygen demand (mg O2/l) • total nitrogen (mg N/l) • total phosphorus (mg P/l) • total chromium (mg Cr/1) (only in wastwater) • total oils and fats (mg/l) • mineral oils (mg/l)

Water samples will be collected in proportion to the 24-hour flow of water, and sound laboratory practices will be used to preserve samples in accordance with the requirements of the State Office for Standardization and Metrology. Effluent waters will be tested at least weekly and stormwater discharges will also be monitored regularly on an as and when required.

Groundwaters

Groundwater quality monitoring will be undertaken to determine the potential impacts of the plant on groundwater quality using three piezometers located within the boundaries of the plant’s plot, one upstream of the plant and two downstream of the plant in the direction of the flow of groundwater along the boundaries of the plot. The piezometers will be located deep enough to enable monitoring water quality in upper water-bearing layer. Piezometers will register the following data4:

• water level (m) • water temperature (°C) • turbidity (mg SiO2/l) • pH • KmnO4 demand (mg O2/l) • electroconductivity ( S/cm) • ammonia (mg N/l) • nitrites (mg N/l) • nitrates (mg N/l) • mineral oils (mg/l)

Groundwater monitoring will be undertaken on a monthly basis following the standard method prescribed by the State Office for Standardization and Metrology. Monitoring will start at least a year prior to the start of plant operation, in order to determine the state of groundwater quality, not influenced by the plant.

Sludge Quality

4 Listed parameters have been specifically selected to determine the influence of the proposed plant on the groundwater; therefore, all parameters typically used to monitor groundwater quality are not included To safely monitor potential unfavourable impacts on the environment, it is necessary to permanently monitor the contents and concentrations of hazardous substances in the processed sludge. The monitoring program will include the following parameters:

• daily quantity of processed and dehydrated sludge (m3/d) • daily mass of dry matter in sludge (t/d) • concentration of total nitrogen (mg N/kg of dry matter) • concentration of total phosphorus (mg P/kg of dry matter) • concentration of total potassium (mg K/kg of dry matter) • concentration of cadmium (mg Cd/kg of dry matter) • concentration of chromium (mg Cr/kg of dry matter) • concentration of lead (mg Pb/kg of dry matter) • concentration of zinc (mg Zn/kg of dry matter) • concentration of harmful organic substances (PCB, HCH, etc.) (mg/kg of dry matter)

Initially sludge samples will be taken on a monthly basis from tanks for stabilized, dehydrated sludge prepared for transport. Reference parameters for permanent sludge monitoring will be determined one year after connection of all present water users to the plant.

Air Quality

The influence of the plant on the surrounding air quality will be monitored at two stations located along the boundaries of the proposed plant. The air monitoring program will monitor the following parameters:

• direction and velocity of wind (m/s), • air temperature (°C), • air humidity (%), • precipitation (mm/min), 3 • ammonium (ug NH3/m ), 3 • hydrogen-sulphide ( g H2S/m ), 3 • mercaptanes ( g C2H5SH/m ), 3 • sulphur dioxide ( g SO2/m )

Samples will be tested at least quarterly according to the methods prescribed by the Regulation on the Recommended and Limit Air Quality Values (The Official Gazette, Narodne novine, No. 101/96). Monitoring will commence at least a year before the plant starts functioning in order to determine the impact of other air pollutants surrounding the plant.

Noise

Noise levels will be recorded at the western boundary of the plant to ensure that the limits permitted for industrial areas are not exceed in accordance with Article 6 Paragraph 3 of the Regulations on the Highest Permitted Noise Level in People’s Living and Working Environment (The Official Gazette, Narodne novine, No. 37/90). The measuring of noise level (dBA) shall be performed night and day during working hours. Four measurements a year are suggested, starting one year before the plant starts functioning.