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Q&A about soil remediation work at Old Town Hall

61 Main Street – Soil Remediation Plan

Q1 – Why is this remediation project being conducted?
A – The City of Ottawa has conducted several environmental investigations at 61 Main Street to characterize soil and groundwater quality at the site. The site assessments identified elevated levels of several polycyclic aromatic hydrocarbons (PAHs) in surface and subsurface fill material at concentrations exceeding the Ontario Ministry of the Environment (MOE) 2011 Table 3 Site Condition Standards for residential/parkland/institutional land use and coarse textured soil. In order to address the PAHs found in the soil at the site, the city’s Environmental Remediation Unit will be undertaking a remedial program that will involve removal of all exposed shallow soil to a depth of 30 cm across the site, and replacement with a non-woven geotextile layer and cap of clean soil/grass or playground sand. This project is being undertaken in conjunction with the addition of a new accessibility ramp at the facility that will be constructed during August and September 2014.

Q2 – What are PAHs?
A – Polycyclic Aromatic Hydrocarbons (PAHs) are a group of more than 100 chemicals that are produced during the incomplete burning of fuels, garbage or other organic substances such as tobacco, plant material or charbroiled meats. PAHs are also contained in asphalt, crude oil, coal,
coal tar pitch, creosote and roofing tar, and are found throughout the environment in the air, water and soil. They can occur in the air, attached to dust particles, or as solids in soil or sediment.

Q3 – What is the source of contamination at this site?
A – No obvious sources of PAH contamination have been identified based on the historic or current use of the site, given that the property has been occupied by the current community building since it was constructed in the late 1800s. Possible sources of the PAHs found in the soil at this site are historic railway related activities along the current path of Highway 417 north of the site, fill quality brought to the site at the time of building construction, or historic use of coal fired heating equipment at the building.

Q4 – Why are PAHs in soil a potential health risk?
A – PAHs can be harmful to human health under some circumstances. Several of the PAH compounds are potential cancer-causing agents and benzo(a)pyrene is a known carcinogen. PAHs can also be skin irritants. Everyone is exposed to small amounts of PAHs through air, soil, household dust, food, drinking water and various consumer products. In order for PAH-contaminated soil to become a hazard, there must be direct contact with or disturbance of the contaminated soil. Appropriate measures should be taken to ensure that adequate groundcover, e.g., grass, patio, etc., is in place so that the ground surface is not bare soil.

Q6 – What is the city’s remedial action plan for the contaminants at 61 Main Street?
A – It should be noted again that PAH contamination has been identified in the soil and direct contact or significant disturbance of the soil must occur in order for the risks above to occur. As a result, remediation of the site will focus on preventing direct contact with the soils and will involve removal of shallow soil to a depth of 30 cm across all exposed portions of the site. Areas of the site that are already covered with an impermeable surface, such as patio stone walkways and the splash pad, will be left in place, as there is no direct exposure of soil in those areas. In areas where more significant ground disturbance is expected (such as below the swing set), soil will be removed to a depth of 60 cm.

Q7 – How will the site be monitored to ensure that the risk management measures are successful?
A – The soil at the site will be inspected and maintained on a regular basis to ensure the continued integrity of the cap. Any required repairs will be made forthwith and a record of all inspections, deficiencies and repairs will be maintained by the city.

Q8 – Does the contamination currently pose a human health risk?
A – A Human Health Risk Assessment (HHRA) has been completed to assess the potential human health risks associated with the elevated PAHs found in the soil. The HHRA identified a risk estimate associated with direct contact to PAHs in soil that was slightly greater than the level
used by the MOE to denote a potential unacceptable risk (i.e., one in one million or 10-6). It is noted that the risk estimate is based on a number of conservative assumptions regarding the duration and intensity of exposure and that actual risks are likely to be lower than those estimated in the HHRA. The remedial program to be implemented at the site will further reduce the level of risk at the site by removing all exposed shallow soil and limiting exposure to the remaining soil below.

Q9 – Will the community be exposed to unacceptable levels of contaminants during redevelopment?
A – No. The Health and Safety Plan will include plans for dust control and soil tracking to prevent excessive dust emissions at the site and adjacent properties as well as to prevent vehicle tracking of contamination onto municipal roadways and private properties. An environmental consultant retained by the city will be on-site during the duration of the project to ensure that dust mitigation measures are being implemented.

Q10 – Is Public Health involved in this project?
A – No, Public Health is only engaged when the city identifies contamination conditions that pose an immediate or imminent risk to human health. Public Health has been notified of this project, and a copy of this fact sheet has been provided for their reference.

Q11: What is the estimated cost of this remediation program?
A – As of the end of June 2014, the procured costs for this remediation project are approximately $104,000 (excluding taxes). This includes the preparation of the tender, the construction contract and environmental oversight during the remediation project. A portion of the budget has also
been allocated to providing additional environmental support as needed during the construction of the new accessibility ramp.

Q12: When is remediation work expected to begin?
A – The remediation project will begin on July 2, 2014, and is expected to be finished the week of July 28, 2014. Construction of the accessibility ramp along the south side of the facility will then begin in August 2014, and is expected to be finished in early October 2014.