The active remediation phase starts after the site assessment approval order has been issued. Active remediation for the Petroleum Restoration Program is governed by Chapter 62-780, Florida Administrative Code (F.A.C.), and other rules, laws, and documents referenced therein. Specifically, Chapter 62-780.700, F.A.C. Active Remediation, although requirements listed in other sections of the rule may also apply.
The goal when addressing a petroleum discharge either through source removal, active remediation or natural attenuation monitoring is to reach closure and the issuance of a Site Rehabilitation Completion Order (SRCO). The risk management options level I, II and III (RMO I, II and III) found in Chapter 62-780.680, F.A.C., are authorized in Section 376.30701(5), F.S., Site Selection and Cleanup Criteria, and were developed to provide equivalent levels of protection to human health and the environment. Whenever possible the selection of a closure option should be established prior to the implementation of a Remedial Action Plan (RAP) and upon consultation with the property owner and/or responsible party. Site mangers should be familiar with the criteria for No Further Action and No Further Action with Controls as specified in Ch. 62-780.680, F.A.C.
Risk Evaluation and Conceptual Site Model (CSM)
Closure strategies for a site must be based on an understanding of site conditions. The Conceptual Site Model (CSM) is a tool used to assist in making site management decisions. Site conditions and assessment data can be compiled into a CSM. The CSM should evolve as site conditions become better defined and as remedial progress occurs. The CSM is composed of the following components:
Description of the source of contamination
The extent of contamination of the soil and groundwater (plume depth and horizontal extents)
The characteristics of the physical/geologic/chemical/environmental setting below grade and on the ground surface.
A description of risk to humans and the environment posed by exposure to the contamination
A description of the current and potential exposure pathways to the contamination
An evaluation of remedial strategies suited for the site
Pilot Testing and Remedial Action Planning
The first scope of work in the active remediation phase will be for pilot testing (if necessary) and remedial action planning. Remedial Action Plans (RAPs) must be prepared in accordance with DEP guidance and Chapter 62-780.700, F.A.C. Specific guidance for RAPs can be found on the PRP Remediation Guidance webpage. The ATC includes two levels of RAPs and four levels of limited scope RAPs or RAP Modification along with detailed descriptions of what level of RAP is appropriate. A Pre-RAP meeting is typically scheduled before a RAP is prepared to discuss the CSM and remediation goals including proposed technology, need for a pilot test, and the level of RAP required.
The first task in the scope will be for Pay Item 1-2 a. No cost HASP. The second task may consist of supplemental site assessment (SSA) needed for preparation of the RAP or a pilot test plan. Pilot testing is usually not performed if there is a nearby site that has similar CSM, particularly lithology and contaminant conditions, and has had successful remediation results. Data from the nearby site may be used in lieu of performing a new pilot test for remedial action planning. If a pilot test is deemed necessary it can be added via change order based on the specifications in the approved pilot test plan. The last two tasks will be for the completed RAP and Construction Drawings and other applicable Schedule of Pay Items (SPI).
Air sparging (AS) is the most common technology used to remediate petroleum contamination. AS systems use compressed air directed into treatment wells screened below the water table. The air causes the dissolved petroleum to volatize. The vapors created will collect in the soil above the water table. A vacuum extraction (VE) system is used to remove the vapors from the soil. Typical components of a AS system include an air compressor, a heat exchanger (to reduce temperature of compressed air), filters to remove particulates and potential oil carryover from the compressor, air distribution piping, AS wells, system meters and gauges, and backflow prevention (to prevent water from entering compressor when not running). AS systems may use vertical, angled or horizontal wells.
An underground injection control (UIC) notice is required for sparging wells. See the UIC Notice Air Sparge Wells. This notice can be completed by the contractor or site manager, should be included in the RAP, and is attached to the RAP approval order.
Bio Sparging (BS) systems are low-flow AS systems, generally less than 4 ft3/min. Flow rates are selected to minimize the generation of vapors in favor of providing oxygen to native bacteria in order to promote biological degradation of petroleum contaminants. BS systems have the same components as an AS system. BS may be equipped with a VE system to ensure vapors are controlled.
Vacuum Extraction (VE) systems use blowers or compressors to apply a vacuum to soil above the water table causing air to flow through the soil and vapors to be collected and treated. Typical components of a VE system include a vacuum blower/compressor, an air-water separator, groundwater collection tank/treatment/disposal system, system piping, treatment wells, off-gas treatment, and system meters and gauges.
Multi-Phase/Dual-Phase Extraction (MPX/DPX) systems use high vacuum blowers and/or in-well (submersible) pumps to extract contaminated vapors, groundwater and free product in one stream to the treatment system. These technologies are used at sites with less transmissive lithology and where it is desirable to lower the water table in order to access more vadose soil. Typical components of a MPX/DPX system include a vacuum blower or liquid ring pump, submersible pumps, groundwater collection tank/treatment/disposal system, system piping, treatment wells, and system meters and gauges.
Injection Systems may use chemical oxidation or biological enhancements to reduce contaminant levels. Injectants are delivered below ground using a pump or compressor and treatment points or wells. This technology is highly specialized and most vendors have a proprietary product and/or application method. Typically, these technologies are applied by means of direct push technology.
The Site Manager should use the information from the approved RAP, construction drawings and SPI submitted by the contractor to create the remedial action construction (RAC) purchase order. This scope of work will cover treatment point installation, system installation, baseline sampling, startup, and one quarter of operation and maintenance (O&M).
A system startup report should include data to document that the remediation is in accordance with the approved RAP, Chapter 62-780, F.A.C., and requirements of the purchase order. A checklist of startup items is available in the PRP Remediation Checklist workbook. This report is critical for the remediation stage because it verifies that the remedial activity is performing as designed. The Site Manager should consult with the team P.E. during review in order to ensure that all necessary data has been collected and reported.
Conventional excavation involves the use of an excavator or a backhoe. Shoring and or dewatering of the area to be excavated may be required depending on the soil types, depth to water, adjacent buildings or roads, and depth of excavation. Shoring may be done with sheet piling, trench boxes, or LDAs. Clean overburden often can be combined with imported backfill. Also, it is not uncommon to apply biological or chemical enhancements during backfill operations. Proper compaction is critical to avoid subsidence and cracks after the excavation.
Large Diameter Auger (LDA)
LDA rigs historically used to install pilings can also be used to remove contaminated soil. The most common design is overlapping 5-foot diameter holes, although other auger sizes are available. Flowable fill, which is a type of lower strength concrete, is used to fill the borings. Flowable fill can be mixed onsite or be brought in from a batch plant.
Source Removal SOW/SPI
The Site Manager should use the information from the approved RAP, Construction Drawings and SPI submitted by the contractor to create the Source Removal purchase order. This scope of work will cover backfill screening, well abandonment, source removal, and site restoration including well replacement.
The source removal report should include data to verify that source removal was performed in accordance with the approved RAP, Chapter 62-780 F.A.C., and purchase order. This report is critical to document that the source removal was performed as planned. The information in this report may include weigh tickets/manifest, disposal volumes and tonnage, backfill compaction results, site restoration documentation, analytical testing results (backfill and confirmatory soil), monitoring well logs dewatering treatment system sampling results, and NPDES reporting. The Site Manager should consult with the team P.G. or P.E. during review in order to ensure that all necessary data has been collected and reported.
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