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Home My WebLink About15.D.1. Delay of Aggregate Industries Quarry Acquisition . "' Is-, O. I, . CITY OF SHAKOPEE MEMORANDUM To: Mayor and City Council Mark McNeill, City Administrator From: Mark Themig Meeting Date: January 4, 2005 Subject: Delay of Aggregate Industries Quarry Acquisition INTRODUCTION I am writing to update you on the delay of the acquisition ofthe Aggregate Industries quarry, and to discuss what additional steps may be needed to move forward with this project. BACKGROUND The purchase of the Aggregate Industries quarry in Shakopee for park, recreation, and open space uses was conditioned by Council on the successful completion of the Phase 2 environmental site inspection. Council appointed Councilors Helkamp and Menden to acton behalf of the entire Council if there were any questions regarding the Phase 2 results; DISCUSSION The city received a draft of the executive summary of the Phase 2 on Tuesday, December 28. The Phase 2 identified a concern related to diesel range organic (DRO) concentrations in several areas of the site. I was able to circulate the report to Councilors Menden and Helkamp, as well as the city's attorneys for their review. We cOl1curredthat a conference call withBonestroo, Rosene, and Anderlik was needed to discuss the significance of this finding, and the overall Phase 2. On December 29th, we held a conference call with Councilors Helkamp and Menden,Jim Thomson and Bonnie Wilkins (city attorneys), and Stuart Krahn, Dave Anderson, and Tim Modjeski (staff from Bonestroo). Mr. Anderson and Mr. Modjeski provided us with an overview of the Phase 2 study, and discussed the diesel range organic results in detail. Diesel Range Organic (DRO) As explained by Bonestroo, a DRO reading indicates some level. of heavy fuel oil contamination somewhere on the property. Soil boring GP-1 (northwest portion of the site) detected a DRO rating of 640 parts per billion (ppb) in the ground water. GP-4 and the SW Corner sampled the lake surface water and detected DRO readings at 130 ppb and 150 ppb respectively. These results raise two questions: 1. What is the source of the contamination? 2. Is there. any risk associated with exposure to the levels of DRO that have been identified:on the site? , . . Contamination Source Since this is an industrial area, detecting ORa is not entirely surprising. However, the work' that has been done to date can not identify the contamination source, and additional investigation would be needed. Possible sources include previous documented or undocumented spills on the property, documented or undocumented spills on adjacent property, or some migration of contamination through the groundwater system from properties that are further away. Risk The next question is whether or not the ORa levels raise concerns for those that might come in contact with ORa, especially in the lake water. The state does not list a "health risk limit" for ORa that sets standards for exposure like it does for other materials. However, it does list a "health based value" for ORa that some use as a guideline. The health based value is 200 ppb, according to Bonestroo. With questions regarding the source of the contamination and risks, there was consensus to delay the closing until we had more information to report back to Council in the future. Future Steps Further investigation is needed, but we have not yet received the complete Phase 2 report to fully understand the issues. Some possible steps that could be considered include the following: 1. Solicit a proposal from Bonestroo regarding how they would investigate the ORa source, and what that additional work would cost. 2. If the source is identified, determine whether or not it can be remediated. 3. Research and gather additional information on ORa levels to help determine whether or not there are any short or long-term risks associated with exposure to the levels in the lake water that have been identified. 4. Discuss what assistance Aggregate Industries is willing to provide in this work. and what responsibility they would have in remediation if the source is found to be on the property. (The current version of the purchase agreement requires that the city be satisfied with the condition of the property.) REQUESTED ACTION At this point, this report is intended to be informational and no specific action is requested. We would return to a future meeting with more information. , , . Executive . Summary City of Shakopee Quarry Lake Project Phase II Investigation On December 16,2004, as a follow up to Phase 1 findings for the QuarryLake project site, a representative of Bonestroo, Rosene, Anderlik & Associates (BRAA) observed the advancement of six soil borings at areas of potential concern as described in the Phase I report. At Recognized Environmental Condition (REC) number 1, three borings, GP-l,GP-2 and GP:..3, were advanced in the NWcorner of the property were Stellar Construction has stored construction materials and demolition debris. Of visible concern was the large amount of concrete with rebar and wire/cable debris used as fill. Three soil and two groundwater samples were collected from this area. One soil boring, GP-4, was completed at REC number 3 at the end ofthe lake access road from the Bituminous Roadways Plant. The material thought to be a potential spill containment boom is a used canvas filter bag, per plant personnel. A shallow soil and a surface water sample were collected from near the debris. Two borings, GP-5 and GP-6, were completed in the area ofREC number 2. No obvious staining was noted and no tank was located. One groundwater and two soil samples were collected from this area. Closer to the edge of the lake from this location a groundwater seep was noted. Finally, a surface water sample was collected at REC number 4. No visible evidence of a scummy substance was noted. At this SW comer location, two bedrock groundwater seeps were also observed. Based on the limited subsurface information gathered to date, analytical results indicate diesel ranged, organic (DRO) concentrations in shallow soils from "non-detect" to 141 parts per million (ppm) in the NW comer, and 13.6 to 19.2 ppm in and around the batch plant to the NE. Groundwater samples indicated DRO concentrations from "non-detect" to 640 parts per billion (Ppb) in the NW comer, 150 ppb in the SW comer, 130 ppb from GP~4 and "non-detect" from GP-5. Toluene was detected in the groundwater collected from GP:..5 ata concentration of 1.1 ppb. All other analytes (gasoline ranged organics, volatile organic compounds) were not detected. Metals concentrations in the soils were not detected or were within natural occurring concentrations and are below their respective ,Soil Reference Value. (SRV) for the more stringent residential use scenario. The state has set a Health Based Value (HEV) of 200 ppb for DRO in groundwater. The HBV is a guideline number, but since GRO was detected at 640 ppb in the NW comer, it is. recommended that this'area be investigated further to determine the extent and magnitude of the product. The seeps are a natural feature and should also be protected during site. development. J:, . Table 1 Soil Analytical.Results (mgIKg) Parameter GP-l GP-2 GP-3 GP-4 GP-5 GP-6 Tier 1 SRV Arsenic 6.1 <0.45 1.1 <0.5 0.46 <051 10 Barium 39.9 38.7 31 12.1 14.7 13.7 1,200 Cadmium 0.26 0.14 <0.045 0.38 0.49 0.39 35 Chromium 8.7 6.5 6.6 2.3 3.8 2.9 34,300 Lead 10.7 2.6 2.2 1.6 5.7 4.0 400 Mercurv 0.021 <0.019 <0.019 <0.020 <0.020 <0.021 0.7 Selenium <0.68 <0.67 <0.68 <0.74 <0.69 <0.76 170 Silver 0.68 0.69 <0.45 <0.5 1.4 1.3 170 DRO 71.1 141 <10.2 19.2 16.6 13.6 NA GRO <5.4 <5.6 <5.3 <5.6 <5.4 <0.54 NA Benzene <0.054 <0.056 <0.053 <0.056 <0.054 <0.054 1.5 Toluene <0.054 <0.056 <0.053 <0.056 <0.054 <0.054 NA Ethvlbenzene <0.054 <0.056 <0.053 <0.056 <0.054 <0.054 NA Total Xvlene <0.16 <0.17 <0.16 <0.17 <0.16 <0.16 NA Notes: SRV: Soil Reference Value for residential scenario Table 2 Water Analytical (ug/L) Detected Parameters GP-l GP-3 GP-4 GP-5 SW Corner DRO 640 <110 130 <110 150 Toluene ND ND ND 1.1 ND Notes: DRO: Diesel Range Organics I I I I I I I I I \ I I I I I I I I I r -ofJl.4l:' Noa,V_ III' ~ .-"0.' ,ClLS1' I -.0 ElL_"OOOOOT1I e.t...._.~~\.<<.oo UL".,UI Otl,(f ITT _nmc .IlONESTROO. ~ENE.AHO[Ilt./I(.l: ~SSOCj&.1ES. ~c 1002 [)O,TE ut.HO. .