Cost Estimate for Removal and Disposal of Contaminated Soil

Transcription

1 14432 SE Eastgate Way, Suite 100 Bellevue, WA tel: Mr. Mark Menard Sound Transit 401 South Jackson Street Seattle, Washington Subject: Cost Estimate for Disposal of Contaminant-Impacted Soil Roosevelt Station Parcel NL Roosevelt Way NE, Dear Mr. Menard: The purpose of this letter is to provide a planning level cost estimate for disposal of soil containing low level contaminants that may be encountered during redevelopment at the northwest corner of the Roosevelt Station parcel located at 6600 Roosevelt Way Northeast site). The parcel is known as Sound Transit Parcel NL705. The location of Parcel NL705 is shown on the attached Figure 1. Background The subject property was purchased by Sound Transit to allow for construction of Sound Transit s Roosevelt Link Light Rail Station. A prior Phase 1 environmental site assessment ESA) conducted for the site on behalf of Sound Transit identified an historical gas/service station at the northwest corner of Parcel NL705 in the area shown on Figure 2. This was considered a Recognized Environmental Condition REC). To investigate this REC, CDM Smith conducted a Phase 2 ESA at the site during January and February, The scope of the Phase 2 ESA involved drilling a series of borings using a hollow stem auger to observe subsurface soil conditions and to collect soil samples for laboratory analysis. The results of the Phase 2 ESA identified the presence of diesel-range petroleum hydrocarbons and carcinogenic polyaromatic hydrocarbons cpahs) in some of the shallow fill soils, specifically at borings B-04 and B-06 Figure 2). While the concentrations of these compounds were not found to exceed their respective Model Toxics Control Act MTCA) Method A cleanup levels for unrestricted land use, their presence will need to be considered in the event that these soils are excavated and require offsite disposal. Cost Estimate for Removal and Disposal of Contaminated Soil The estimated total cost for contaminated soil removal and disposal is summarized in the table below. Assumptions and calculation information follows.

2 Mr. Menard Page 2 Range of Contaminated Soil Estimates Cost to Dispose of Contaminated Soil Low $14,000 High $20,000 Assumptions It is assumed that this effort will be an incremental cost to construction work already under way, such the required equipment to conduct the excavation of contaminant-impacted soil is already in use and is included in the construction budget. Further, it is assumed that erosion and sediment control measures are already in place, and that the removal of the contaminated soil does not trigger other potential construction controls such as utility replacement, utility protection, or shoring. It is also assumed that, since the contaminants are limited to petroleum compounds and cpahs no chlorinated compounds, for example) and the contaminant concentrations do not exceed applicable soil cleanup levels, the contractor will not apply a surcharge for Hazwoper-trained construction personnel. In short, the cost estimate is compared to the option of disposing of the soil as clean fill. Estimated Soil Quantity CDM Smith reviewed the available data from the Phase 2 ESA to estimate the lateral and vertical extent of contaminated soil at the locations of borings B-04 and B-06. Given that only low level contaminants were identified and at only two of the seven boring locations, the lateral extent is expected to be limited. For purposes of this cost estimate we estimate an area from 100 to 225 square feet at each location, as indicated on Figure 2. Based on a review of the laboratory data, boring logs and an assessment of the subsurface fill soil types, the vertical extent of contamination is not expected to extend beyond 5 feet below ground surface bgs). The range of the potential volume and tonnage of contaminated soil was estimated by using the above estimates of lateral and vertical extents of contaminated soil and is summarized in the table below.

3 Mr. Menard Page 3 Range of Contaminated Soil Estimates Volume cubic yards) Quantity tons) Excavation Dimension Assumptions Low x 10 lateral x 5 deep High x 15 lateral x 5 deep Assumptions: Expansion factor = tons/cubic yard Estimate for Trucking and Disposal Assumptions to develop costs for trucking and disposal are as follows: Three to six truck loads Estimated travel time for trucking is 1.5 hours per truck round trip for Republic Services Transfer Station in Seattle. Hourly trucking cost of $155/hour Disposal rate of $45/ton Stockpile segregation, cover, loading at $5/ton 30 tons per truck load Contractor mark-ups of 25% for taxes, insurance, bonding, fees Using the above figures, the cost per ton for soil disposal is roughly $75. Given the estimated total weight range of 80 to 160 tons, the total cost of transportation and disposal of contaminated soil is estimated to range from $6,000 to $12,000. Consultant Oversight It is assumed a consultant will also oversee the soil excavation, collect confirmation soil samples, from the excavation limits, assist with soil profiling for disposal and provide a brief report that documents the work. Consultant oversight costs are based on the following assumptions: $1,500 per day for oversight during soil excavation and removal. 6 profiling and confirmation soil samples collected for analysis.

4 Mr. Menard Page 4 $250 per soil sample for analysis Documentation and assistance with soil profiling: $2,500 Project management, about 15% of the total fee. The total cost for two days of consultant oversight, soil sampling, a letter report or memo, and project management is estimated to be $8,000. We appreciate the opportunity to provide this cost estimate. Please feel free to call either of us at 425) if you have any questions. Sincerely, August Welch, LG Geologist CDM Smith Inc. Pamela J. Morrill, LG, LHG Project Manager CDM Smith Inc. Attachments

5 SITE LOCATION SITE VICINITY Phase 2 ESA Roosevelt Station Parcel NL705 Seattle, Washington 0.4 Miles Figure 1 Vicinity Map

6 NE 67th Street Former Dewatering Pit Approximate Location of Former Station Building Former QFC Building Excavation for the Roosevelt Station Apparent Former UST Cavity 12th Avenue NE B-04 B-07 B-02 B-06 B-03 B-01 B-05 Roosevelt Way NE CDF Backfill Estimated areas of contaminated soil identified during Phase 2 ESA at locations B-04 and B-06 to be removed and disposed of at an approved facility. NE 66th Street vacated) Legend Site Boundary Boring Location and ID Phase 2 ESA Roosevelt Station Parcel NL705 Seattle, Washington Estimated Area of Contaminated Soil Removal Figure 2 0 Boring Locations and Estimated Areas of Boring Locations Contaminated Soil Removal Feet