Istokpoga Marsh Water Improvement District. Water Quality Improvement Project. Copper Corrective Actions. Soil Management Plan.

Transcription

1 Istokpoga Marsh Water Improvement District Water Quality Improvement Project Copper Corrective Actions Soil Management Plan Prepared by South Florida Water Management District West Palm Beach, Florida May 27,

2 Contents 1.0 Introduction Background Soil Management /Re -Use Area Successfully Remediate Area pending Remediation Earthen Berms Confirmation Sampling Reporting... 7 Figures Figure Figure

3 1.0 Introduction The South Florida Water Management District (District) is pleased to present the Istokpoga Marsh Water Improvement District (IMWID) Soil Management Plan (SMP) to address copper impacted soils in the project area. The SMP requires that all soils excavated onsite are document within the approximate 308 acres IMWID Water Quality Improvement Project area during construction. Previous environmental assessments conducted on behalf of the District have identified residual concentrations of agrochemicals, specifically copper, within surficial soils that if not remediated would pose an unacceptable risk to the United State Fish and Wildlife Service (Service) trustee species. In addition, to ensure worker safety onsite the contractor shall review the previous environmental assessment completed by Professional Services Incorporated (PSI) dated January 15, 2009, and URS Corporation report, dated January, To assess workers safety and OSHA Health and Safety requirements during the construction, it is recommended that the contractor develop a Site Specific Health and Safety plan. 1.1 Background The District in conjunction with Highlands County, Florida Department of Agriculture and Consumer Services (FDACS) and the Florida Department of Environmental Protection (FDEP) plan to convert the current and former agriculture lands to a water retention area to improve water quality and reduce flow downstream. The project site is located within Section 1, Township 37 South and Range 30 East of Highlands County. The project can be accessed from Highlands County Highway 621 located to the north of the subject site. See Figure 1 for project location. The project has been improved for the cultivation of various crops including citrus, palms, caladium and sod. To assess the concentration of residual agrochemicals the District conducted a Phase I and II Environmental Assessment (EA) and Limited Screening Level Ecological Assessment (SLERA) in (PSI, 2009). The EA included the collection and analysis of 32 soil samples across the project area. The site wide soil analysis detected concentrations of organochlorine pesticides (OCP), arsenic, barium and cooper in the surficial soil samples (0-6 inches below land surface. For the proposed restoration project copper was identified as a constituent of concern (coc), at concentrations above the Service s interim copper sediment quality guideline of 85 milligram per kilogram (mg/kg). Copper concentrations in surficial soils ranged from less than 1 mg/kg to 310 mg/kg. The mean concentration was 134 mg/kg while the median concentration was calculated at 120 mg/kg. The FDEP 95 Upper Confidence Level site wide average was calculated at 206 mg/kg. See Figure 2 for the site wide surficial sampling data. The project site has three unique current /former agriculture uses. The northern section of the project area consists of an approximately 75 acres of bedded citrus grove. The EA included the collection of seven shallow soil samples for analysis of copper within this area. The soils in this area consisted of loose sandy material with a lower percentage of natural occurring muck as compared to the southern section of the project. The second former agriculture use area onsite consisted of an approximately 46 acre palm tree farm. This area is rectangle in shape located south of the citrus tree area. Again this area consisted of loose sandy material with a lower percentage of natural occurring muck compared to the southern section of the property. The EA included the collection of 5 soil samples for analysis of copper. The third agricultural use area consists of 168 acre of active sod and fallow caladium fields located on the 3

4 southern section of the project boarding the palm farm to the north. The EA included the collection of 20 samples from the former caladium farm. The maximum concentration detected in the former caladium field was 310 mm/kg. The mean concentration was 171 mg/kg and the median 140 mg/kg. The FDEP 95% UCL was calculated at 254 mg/kg. See Figure 3 for the crop uses. 2.0 Soil Management /Re -Use In the event that impacted soils are excavated along the perimeter berm or for other earth work projects the contractor is required to obtain prior approval from the District. The following is a partial list of onsite and offsite reuse methods for impacted soils that are excavated. Off- site Reuse Off-site Disposal Impacted Soil Approval Reuse or Disposal / Staging Requirements Type Method Relocation to Staging Area on Northern Project Boundary Onsite Soil Blending Ditch Fill Material Dry Side of Berm Any soils transported offsite will require a plan which identify the proposed off site use and appropriateness of re-location. Offsite reuse will need to be approved by the District, FDEP and Highlands County. The prefer offsite reuse would include spreading on local or adjacent agricultural farms. Use for residential or commercial property is considered a non-prefer option. It is likely that the presence of residual c agrochemicals would cause this option to be not allowed. The District would consider the offsite disposal of impacted soil as a non-prefer option based. Prior District approval of offsite for disposal is necessary The cost for transportation and offsite disposal would cause this option to be not acceptable. The relocation of impacted soil to onsite staging areas is consider a prefer option. The contractor will need to provide the District a plan which identifies the volume of soil relocated to the staging area. The plan should identify those areas where soil was excavated from and relocated to. The onsite reuse of soil by blending is a prefer option. Reuse of soil in the earth berm will require a plan from the contractor that documents that soil reuse will meet both engineering and environmental requirements. A copy of the plan will be submitted to the FDEP and the Service for approval.the District will support the contractor, however soil blending must result in a soil copper concentration of less than 85 milligrams per kilogram Reuse of soil for fill material in ditches or other uses will require prior approval by the District. Soil use for fill would at a minimum need to be capped with one foot of nonimpacted soils. Additionally these soils would need to be below copper leach ability standards. The contractor will need to submit a plan to the District prior to filling which will require FDEP concurrence. The reuse of soil on the dry side of the earthen berm is a prefer option. Impacted soil can be used on those sections of the berm specifically the dry side of earth berm with limited approval. The contractor will need to provide a plan indicating the location of the soil placement which demonstrates that impacted soil will not be inundated. 2.1 Area Successfully Remediate The District has remediated the southernmost 40 acres of the project area (see Figure 2). During the proposed future construction, the selected contractor shall not implement earth work in the previously remediated areas that would allow copper impacted soils to be exposed to the surface without prior approval from the District. In the event that earth work is necessary in previously remediated areas the contractor shall provide a plan which details how impacted soil will be handled. A copy of the plan shall be submitted to the Service and FDEP for review and concurrence. 4

5 2.2 Area pending Remediation In those areas where soils have not been remediated the contractor shall handle those soils top 12 inches as impacted. Impacted soil shall be placed outside of the proposed inundation area, capped in place or remediated insitu to reduce copper concentrations. In the event that construction activities will disturb impacted soils the contractor shall notify the District prior to implementing site activities. The notification shall include a plan to address impacted soils. The District will need to approve site activities in the copper impacted areas. Upon the completion of the site work, the District shall collect confirmation soil samples to document that the soil copper concentrations are less than 85 mg/kg. In the event that copper samples are detected above 85 mg/kg additional excavation or remediation would be necessary to reduce copper soil concentrations below 85ppm. 2.3 Earthen Berms Copper impacted soil could be used to construct earthen berms pending approval by the District of the contractor plans if: Soil are adequately tested to meet geo- technical requirements Soil that pose either surface water or ground water leaching or ecological risk are placed on the dry side of the earthen berm, within the soil berm or are placed in a staging area located outside of the inundation area. Impacted copper soils could be blended with non-impacted soil to reduce copper concentrations below 85 mg/kg Copper impacted soil could be capped with one foot of non-impacted soils Copper impacted soil could be remediated insitu to reduce copper concentration below 85 mg/kg i.e. soil plowing Site clearing /grubbing All handing and movement of soils within the project areas must be tracked as to where soil are relocated. A tracking sheet shall be completed by the contractor. The contractor is responsible for coordination between District remediation team and the selected prime and sub-contractor to ensure that remediated areas are not disturbed during construction and any excess muck from areas above the threshold is properly incorporated into soil berms capped treated insitu or stockpiled outside or above inundation levels. Due to existing leases expiration on September , no additional remediation shall be implemented until these leases expire. Once the design/build contract is awarded, one of the first construction activities to be implemented shall include the clearing and grubbing of trees in the northern half of the project area. This work is necessary to allow the District to remediate copper impacted soils within the tree farm and former groves. The land clearing within the tree farm and grove shall remove trees below grade leaving no portion of the trees or root in place 5

6 Once the contractor completes the trees clearing process the District remediation contractor will remove 1-2 inches of soil followed by plowing and tilling. This scraped material will be stockpiled outside the impoundment or above inundation levels or buried in the existing farm ditches and capped. The contractor may use this scrap material for earthen project upon receiving prior approval by the District. Once the sod lease expires, the District remediation contractor will scrape 1-2 inches of soil from the blue areas without tress. This scraped material will be stockpiled outside the impoundment or above inundation levels or buried in the existing farm ditches and capped with clean soils. The contract may use this scrap material for earthen project upon receiving prior approval by the District. The contractor may not excavate or disturb soil from remediated areas without prior approval from the District. Excavation of remediated soil or impacted soil will need to be placed outside the embankment or above the inundation depth of +/ feet NGVD. Additional confirmations shall be collected to confirm that soil copper concentrations are less than 85 mg/kg. 3.0 Confirmation Sampling Upon completion of the soil remediation the District contractor will collect confirmation soil samples. The confirmation sampling will consist of dividing remediated areas into 5 acre grids. One close proximity sample will be collected from each 5 acre grid. Each of the collected soil samples will be submitted for analysis of copper. However each remediated area will consist of a minimum of ten samples. Based on the review of site conditions the surficial soils impacted within the project foot print vary based on current and historical site conditions. The former citrus and palm tree farm located on the north middle section of the site have relatively minor soil impacts compared with the southern section of the property used for the cultivation of caladiums and sod. The soil remediation in the northern section of the property has not been completed to date. Once the contractor is authorized the removal of trees in the tree farm and former citrus grove should be implementing early in the construction process. Upon removal of the trees and site clearing the District remediation contract will remove 1-2 inches of soil or approximately 20,000 cubic yards of soils. This scraped material will be stockpiled onsite within the project foot print. The contract will need to reuse or relocate this material. The stockpile material may be used within the earthen project upon receiving prior approval by the District or relocated to areas that will not be inundated. See table above which describes onsite soil reuse options The former sod field located in the north central project area has also not been remediated to date. Once the sod lease expires the District contractor will remove 1-2 inches of muck soil or approximately 10,000 cubic yards. This scraped material will be stockpiled onsite within the project foot print. The contract will need to reuse or relocate this material. The stockpile material may be use within the earthen project upon receiving prior approval by the District or relocate to areas that will not be inundated. See the table above which describes onsite soil reuse options 6

7 The southern 40 acres of the project area has been remediated. Surface soils within this area should not be disturbed without prior District approval. If the contractor needs to excavate soil in the southern area the contractor will need to obtain prior approval from the District. The District will need to collect confirmation samples upon completion of any earth work the area of previous soil remediation. 4.0 Reporting Upon completion of all earthwork associated with construction of the project, the contractor shall l provide the District with a report. The report shall identify the movement of all soil onsite. The report shall include tables and figures which demonstrate the approximate volume (cubic yard) of soils relocated onsite and the final locations. The report will provide a comprehensive description of the site activities and methodology, and results. A copy of the report will be submitted to the Service and FDEP for review and concurrence. Please contact Robert Taylor or Jeff Needle with the South Florida Water Management District if you have questions or require additional information (561) or

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