10-10-1988 - Agenda Packet City Council - regular meeting

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comment. 5_6 Soil Treatment and Samolin¢ We propose to thinspread contaminated soil excavated during the trench installation. An ideal area for thinspreading is along the southern edge of the proposed trench (Figure 4). There are no residential buildings or industrial buildings within 200 feet of this area. In addition, the prevailing winds are westerly across this area and there are no downwind dwellings or structures for approximately 2,500 feet. We anticipate that approximately 500 to 700 yards of contaminated soil will be excavated during the installation process. The soil will be stockpiled on -site and covered with plastic immediately after excavation. Samples will be collected and `orwarded to PACE Laborcories for analysis (EPA 601/602). The soil will be spread along the southern eon a of the trench approximately six inches thick. The soil will be aerated with a field disc or comparable equipment one time each month until it becomes frozen. Aeration tillage would resume again the following spring. Soil samples will be collected 30 days after thinspreading has been completed. After the initial month, we propose sampling quarterly. Samples will be analyzed for EPA 601 / 602 parameters. After the first year the sampling schedule will be reevaluated. All analytical and operational reports will be forwarded to the MPCA for review. 6.0 METHODS AND PROCEDURES 6.1 Soil Samolin¢ Soil sampling was done in accordance with ASTM:D 1586-84. Using this procedure, a 2 inch O.D. split barrel sampler is driven into the soil by a 140 pound weight falling 30 inches. After an initial set of 6 inches, the number of blows required to drive the sampler an additional 12 inches is known as the penetration resistance, or the "N" value. The "N" value is an index of the relative density of cohesionless soils and the consistency of cohesive soils. 6,,,1_; oil C a-sification As the samples were obtained in the field, they were visually and manually classified by the crew chief in accordance with ASTM:D 2488-84. Representative portions of the samples were then returned to the laboratory for further examination and for verification of the field classification. Logs of the borings indicating the depth and identification of the various strata, the N value, water level information and pertinent infot oration regarding the method of maintaining and advancing the drill hole were made.