Scope of Work
The Historic Landfill Assessments included the following tasks:
Study Area Identification
Historic aerial photographs were reviewed to estimate the extent of solid waste-filled areas and the approximate period of operation for each landfill. For this task, aerial photographs obtained from the following sources, were reviewed as appropriate:
A qualified and experienced environmental professional performed interpretation of these photographs. The standard recognition elements of shape, texture, pattern, size, shadow, tone and/or color were examined to estimate the probable historic solid waste-filled area(s) of each site. The solid-waste filled area(s) were identified on a current aerial photograph of each site. Study areas were established that included the waste-filled area(s) and adjacent areas where visual clues suggested that debris may have been disposed (for example, disturbed soil areas and along access roads). The actual landfill area does not necessarily occupy the entire study area. Surface water bodies and land uses located within ¼ mile of the site were also noted.
An HSA environmental professional, specifically trained in the observance of recognized environmental conditions performed a reconnaissance of the solid waste-filled areas identified under Task I. During the site reconnaissance, particular attention was afforded to site features that may be indicative of landfill activities. Such site features include exposed solid waste or construction and demolition debris, discolored or stressed vegetation, subsidence, stained soils, odors, or other surface or subsurface inconsistencies or anomalies. These features were located on a sketch of the site and photographed when warranted. The name, street address, and apparent use of buildings, utility vaults or other structures within the solid waste-filled area(s) were identified on the site sketch and reported. The building construction style (e.g., slab or stilt construction, single or multi-story, basements, etc.) were observed and noted. The site reconnaissance was confined to publicly accessible and authorized areas.
Visual surveys surrounding the study areas were performed to identify other activities or businesses whose operations could be associated with discharges resulting in contamination of the environment (e.g., dry cleaners and service stations). These activities were identified on a map of the study area.
Potential users and uses of groundwater in the vicinity of the landfills were identified, by researching the City Utility Department account records, reviewing Well Completion Reports maintained by the Southwest Florida Water Management District (SWFWMD), and reconnaissance of the study areas. The computerized account records located at the City Utility Department were accessed to identify locations with active accounts for some services (for example, sewer and refuse collection) but not for water. These residences and other establishments may have individual supply wells. For landfill sites outside the City service area, the SWFWMD Well Completion Reports were used to locate establishments with individual wells. Personnel employed at the Florida Department of Health were interviewed and publicly available, practically reviewable, and reasonably ascertainable available data files were examined. The information obtained, where possible, was field verified. Monitor wells installed at and near the landfill were also identified and analytical data from these wells is included.
The locations of wells best suited for water quality sampling were then identified. The highest priority wells were ones that were close to, and downgradient of, the landfill, and which provided potable water for residences and commercial establishments. Other wells to be sampled included wells that are used for irrigation or other non-potable purposes. The presumption of the direction of groundwater flow was based on previous on-site investigations, if available, or estimated from features depicted on USGS topographic maps and identified during field inspections.
The owners of the wells were identified where feasible. Letters discussing the results of the groundwater survey were transmitted to the City. The owners of the wells were then contacted to detail the Historic Landfill Assessment Program and to requested permission to collect samples from the wells. After receiving approval, water samples were collected and analyzed.
The samples were analyzed for constituents identified as Florida Primary and Secondary Drinking Water Standards, and other constituents of concern including chlorinated herbicides (EPA Method 8150), chlorinated pesticides and PCBs (EPA Method 8080), organophosphorus pesticides (EPA 614), volatile organics (EPA Methods 8240 and 8260), semi-volatile organics (EPA Method 8270), metals (EPA Method 6010 and 7470), and nitrates (EPA Method 353.2).
Landfill Gas Survey
Landfill Gas (esp. methane) concentrations were measured in and around buildings. Where site conditions were favorable (open areas without buildings, standing water or dense vegetation) thermal infrared imagery (thermography) was employed to identify potential locations of gaseous emissions from the landfill. The infrared surveys were conducted using an Inframetrics, TV compatible, Model 600L Imaging Radiometer. This instrument is capable of detecting subtle temperature variations (+/-5 0F), and the readings are recorded on videotape.
The identified "hot spots" were verified and measured in the field. Temperature measurements were gathered at ground surface using a hand-held temperature probe. Hand auger borings were drilled to depths of between two and six feet. The tops of the borings were then sealed and insulated with a Styrofoam disk and the gas was allowed to accumulate for at least one half hour. The temperature probe inserted though the disk and the temperature of the atmosphere in the boring was measured. Next, the intake tube from the gas analyzer was inserted through the plate and measurements of carbon dioxide, oxygen, and methane were recorded.
Buildings located on or near the landfills were tested for methane concentrations. The readings were gathered in confined areas, especially in areas that were not air-conditioned and/or included conduits entering from below ground.
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