PSA - Groundwater Remedy and Quarterly Sampling Plan - Oliver Industrial Park - Hull and Assoc.

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Mr. Chris Dressel July 25, 2016 SBI074.300.0001 Page 4 Monitoring wells will be constructed of two-inch inside diameter Schedule 40 PVC slotted screens and risers. Once the targeted depth has been reached, the well column will be slowly lowered to the base of the borehole. A clean silica quartz sand filter pack will be placed around the screen and will extend no more than two feet above the top of the screen. Sodium bentonite chips or pellets will then be placed on top of the sand pack. Above the chips or pellets, a thick bentonite slurry will be pumped into the annular space using a tremie pipe to a depth of approximately three feet below ground surface. The remaining three feet will be filled with concrete to anchor either a flush -mount manhole or above -grade protective casing. Monitoring wells will be developed following installation to remove fines that may have entered the well screen or filter pack during installation. Well development activities will continue until pH, temperature, and conductivity have stabilized for three consecutive well volumes, or until five well volumes have been removed, whichever is greater. Development waters will be collected and stored in a DOT approved 55- gallon drum. Costs to remove, transport, and dispose of approximately 25 55-gallon drums of containerized groundwater and drill cuttings (which are presumed to be non -hazardous) are included in this task. Following the installation of the new monitoring wells, the top of casing and ground elevations of the new wells will be surveyed so that the groundwater elevations measured in these wells can be compared relative to the other wells in the monitoring network. Costs include a surveying event from Jones Petrie Rafinski to tie the new wells into the monitoring network. Task 3 Implement Groundwater Remedy Following interim approval from IDEM of the groundwater remedy proposed in the December 2015 RWP, Hull will retain the services of IET to introduce a groundwater remedy into the subsurface that will stimulate the degradation of VOCs in groundwater beneath the Site. A pre -remedy on -Site meeting will occur between Hull, IET, the City, and affected property owners to coordinate staging of materials prior to the injections; to secure a water supply for the injections; and to present the overall scope and schedule of the events to all stakeholders. Hull will provide limited oversight during the groundwater remedy but is not proposing to remain on -Site full time for the duration of the injection event, currently projected to take nine (9) days to complete. As summarized in IET's proposal included in Attachment A, a groundwater remedy consisting of injection of three permeable reactive barrier (PRB) walls at three locations is proposed. IET's scope involves reviewing certain groundwater data collected by Hull to establish a baseline and evaluate the effectiveness of the remedy after it is initiated. Before the remedy is initiated, and 180 days, 365 days, 545 days, and 730 days following the remedy event, Hull will collect groundwater samples from monitoring wells in the vicinity of and downgradient from the PRB walls and analyze the samples for the parameters presented in Task 1 a above. The laboratory data will be provided to IET and a brief summary of the continued efficacy of the groundwater remedy will be prepared by IET and included in Hull's quarterly reports as presented in Task 4 below. Finally, as requested by the City, Hull's standard subcontractor markup will be reduced to 5% for IET's costs. Task 4 Prepare Quarterly Reports and Various VRP Documents This task is proposed to assist with a public notice of the intent of the City to proceed with the proposed remedy, should it be required by IDEM. This task also includes effort to prepare quarterly reports summarizing data collected during each pre- and post -remedy sampling event, for a total of nine quarterly reports. The quarterly report summarizing data collected following the 180-day post remedy sampling event as presented in Task 1 a above will include a summary of the groundwater injection event. Also, the quarterly report summarizing data collected following the monitoring well replacement event will contain a narrative and monitoring well construction diagrams summarizing monitoring well installation activities.