Title: Introduction Text: Navy experience has shown that groundwater remediation poses a number of challenges, especially at sites with difficult conditions such as large, low concentration plumes, deep alluvial aquifers, fractured bedrock, and low permeability formations. In the past, pump-and-treat was often used to address groundwater impacts, but this approach has been largely ineffective in reaching final cleanup levels in a reasonable timeframe and often results in high operation and maintenance costs. For this reason, Navy Remedial Project Managers (RPMs) should consider the use of risk management strategies to guide the decision-making process at their groundwater sites. Risk management strategies are based on an evaluation of the contaminated groundwater plume, exposure pathways, and impacts to current and potential future human and ecological receptors. Risk management can be used to assist in determining whether or not a site requires remedial action, or if it is technically feasible to achieve cleanup goals at a site. It is important to consider risk management options first because of the difficulty in addressing challenging groundwater sites with existing and innovative technologies. This Web tool will provide an overview of risk management strategies for groundwater sites. Visual Description: 3-D graphic of a base map with a large, dilute plume, overlaid with pictures of IAS/SVE and biobarrier treatment technologies applied for cleanup of the plume.

Title: Challenging Site Conditions (1 of 3) Text: Certain site conditions may limit the effectiveness of subsurface remediation and result in elevated contaminant concentrations over a long time period regardless of whether or not treatment is applied. Factors that inhibit groundwater cleanup include contaminant and hydrogeological factors. Contaminants in the source zone may be relatively immobile and sorbed or lodged within soil or present as dense nonaqueous phase liquids (DNAPLs). This can result in low, but persistent concentrations within the resulting groundwater plume. Adequate remediation may be inhibited by hydrogeological factors. These include complex sedimentary deposits, aquifers of very low permeability, certain types of fractured bedrock, and other conditions that make extraction or in situ treatment difficult. Also, the geochemical environment over an entire plume tends to vary widely. Visual Description: Graphic illustration of contaminants in the source zone

Title: Site Conditions - Contaminants (2 of 3) Text: Contaminant factors refer to contaminant properties that reduce the efficiency of extraction procedures or in situ treatment processes. These challenges include site use, chemical properties, and contaminant distribution. Site Use: Single contaminant releases are easier to control. Continual releases over time produce a more complex plume that is more of a challenge to remediate. Chemical Properties: Some contaminants may be easier to degrade by biotic or abiotic mechanisms. A contaminant's potential to become sorbed to the soil or rock matrix also contributes to its remediation potential. DNAPLs can penetrate deeper parts of the aquifer, making the source zone difficult to locate and remediate. Contaminant Distribution: Challenges arise during site remediation when the volume of the contaminated media is large and the contamination is deep in the subsurface. Large dilute plumes tend to form under conditions where the subsurface becomes aerobic due to an influx of electrons making reducing conditions difficult to maintain. Large and dilute plumes also occur in subsurface areas where attenuation processes are slow. Visual Description: Table entitled, "Generalized Remediation Difficulty Scale". Contaminant characteristics for site use, chemical properties and contaminant distribution challenges are compared on a generalized remediation difficulty scale.

Title: Site Conditions - Hydrogeologic (3 of 3) Text: Hydrogeological factors that provide challenges during site remediation include site factors such as complex sedimentary deposits and low permeability aquifers. Both the geology and the hydrogeology of the subsurface must be considered when assessing the ease of remediation. Geology: Subsurface areas with interbedded or discontinuous strata are more difficult to remediate. Aquifers of low permeability and some types of fractured bedrock also make site cleanup difficult. Large and dilute plumes are formed in permeable aquifers with low organic carbon content. Aquifers where diffusion into less-transmissive compartments like silt and clay occurs also contribute to the formation of large and dilute plumes. Hydraulics: The above mentioned geological factors are important because they determine the flow and hydraulic conductivity of the subsurface. High hydraulic conductivity and low temporal variation in the groundwater allow transport of the contaminant to microbes and mineral surfaces that can facilitate contaminant degradation. Visual Description: Table entitled, "Generalized Remediation Difficulty Scale". Hydrogeologic characteristics for geology and hydraulics/flow considerations of the subsurface are compared on a generalized remediation difficulty scale.

Title: Conceptual Site Model - Overview (1 of 2) Text: A critical component in identifying the optimal strategy for management of a groundwater plume is defining the Conceptual Site Model (CSM). All CSMs should include the following components: Contaminant source and release information Geologic and hydrogeologic information Contaminant distribution, transport, and fate parameters Land use information Potential receptors and exposure pathways The CSM depicts the working hypothesis of the site by defining the relationship between the source area(s), transport mechanisms, and all of the potential receptors and routes of exposure. The CSM should be described in text and portrayed graphically or in a tabular format to provide a clear understanding of site conditions. Identification of current and reasonable potential future land and groundwater use is important for selecting appropriate exposure pathways and scenarios to depict on the CSM. The CSM should be updated as additional data are collected and for older sites as the understanding of the fate and transport mechanisms change. Also, the CSM may require updating as land development and groundwater usage in adjacent properties changes. Visual Description: A conceptual site model graphics illustrates disposal area landfill, LNAPL, diffusion-controlled mass transfer of contamination, groundwater contaminant plume, vapor from the plume arising to a house above surface, surface water and impacted sediment. Potential receptors are a human consuming drinking water and the fish above the impacted sediment.

Title: Conceptual Site Model - Exposure Pathways (2 of 2) Text: There must be a complete exposure pathway from the source of chemicals in the environment to receptors for chemical intake to occur. Common exposure pathways are shown here. In order to determine if a complete exposure pathway exists for contaminants in groundwater, it first must be determined if the receptor can come into contact with contaminants in groundwater. The use of groundwater within and around the site needs to be examined. Click here to review factors to assess the completeness of the groundwater exposure pathway. Click here to review factors that indicate an incomplete groundwater exposure pathway. Visual Description: Graphics illustrates exposure model. Typical GW exposure pathways are GW ingestion, GW-to-Indoor air, and GW-to-Surface water. Evaluation procedure includes pathway screening, risk-based standards, and risk management.

Title: Factors to Assess Pathway Completeness Text: Presence of domestic, public, or industrial wells Productivity and yield of the aquifer Presence and nature of impermeable zones Natural or background groundwater quality (e.g., salinity, total dissolved solids[TDS]) Contaminant source characteristics Nature and extent (horizontal and vertical) of groundwater contamination Future plans for groundwater use in the area, including local water resource planning, zoning ordinances, land-use planning, and institutional controls that would regulate groundwater uses State/federal groundwater classifications.

Title: Factors that Indicate Incomplete Pathway Text: An exposure pathway is considered incomplete when: Concentrations are below detection limits Concentrations are below regulatory criteria (e.g., maximum contaminant level [MCL]) or risk-based levels for the specific exposure pathway There is not an identified point of exposure in the environmental medium Site-specific data demonstrate that there is no transport mechanism in the identified media to move the chemical from the source area to a point of exposure Use restrictions enforceable by local government or regulatory agencies exist that will eliminate a point of exposure (e.g., drinking water supplied by public water system and groundwater beneath the site is restricted for potable purposes) Land use restrictions enforceable by local government or regulatory agencies exist that will eliminate a point of exposure (e.g., local zoning ordinances).

Title: Risk Management Strategies Text: Risk management is the process of evaluating and selecting among alternative actions to reduce risk to current and future receptors. It is driven by an evaluation of the contaminated media, exposure pathways, and impact to current and future receptors. Important factors are evaluated such as land use, groundwater use, and groundwater point of compliance (POC) assumptions. It also involves an evaluation of cleanup goals for a site, which may be based on regulatory criteria (e.g., MCLs, background values, or site-specific, risk-based criteria). Risk management will also help to determine the remedial strategy for a given site such as deciding between source containment and treatment/removal. The availability of options (such as allowing contamination to remain in place at concentrations exceeding risk-based criteria and using institutional controls to prevent exposure) will depend on applicable State and local laws and regulations. This section of the Web tool discusses risk-based State programs, exposure control, source control, and other plume management strategies.

Title: Federal and State Risk-Based Approaches Text: The U.S. EPA expects groundwater to be returned to its beneficial uses wherever practicable and requires that remedial actions attain cleanup levels that comply with Federal and more stringent state standards or reflect site-specific, risk-based cleanup standards. Therefore, the development of the remedial strategy should include a review of current State regulations for evolving risk management provisions. Several states, including Florida, Texas, and Pennsylvania, have adopted tiered "Risk Management Options," which recognize the technical impracticability and high cost of remediation for groundwater plumes that may pose little risk. These approaches can require a significant amount of characterization and analysis to meet the criteria and demonstrate no unacceptable risk, but in some cases the remedy can be limited to land use controls (LUCs) with limited long-term monitoring. However, several states have an anti-degradation policy, which classifies all groundwater as high priority and/or as a potential drinking water source, regardless of actual or likely future use. This may limit the use of a risk-based approach for groundwater remediation in some states. RPMs should refer to the State-specific program under which their site is regulated for more information. Links are available at the left which summarize State-specific programs. Visual Description: Graphic shows less flexible "No Degradation Policy" states being NJ and WI, and more flexible "Risk Management Policy" states being PA, TX and FL.

Title: Exposure Control - Groundwater Use (1 of 2) Text: It is important to consider the groundwater resource classification when designing a plume management strategy because it could significantly affect the need for exposure controls and/or remedial action (e.g., groundwater may not be potable). The groundwater resource classification can be used to evaluate the quality of groundwater at a given location and assist in determining whether current or potential future exposure risks are present. Several states have implemented a system that classifies/designates all groundwater-bearing units based on current and potential use, water quality, and/or vulnerability. Under this system, groundwater quality standards are established for each class that commonly indicate whether the groundwater is potable, non-potable without treatment, or non-potable regardless of treatment. Groundwater classification should be completed as a partnership between the Navy, U.S. EPA, and state agencies to ensure that the potentially different regulatory systems for groundwater classification are integrated and appropriately applied to federal lands, considering water use and development factors unique to federal facilities. Visual Description: Groundwater Classification includes three classes. Class I: irreplaceable source of drinking water or ecologically vital, and characterized by high yield and low TDS. Class II: current or potential source of drinking water or a water body that has other beneficial uses. Class III: groundwater body is not potential source of drinking water and is of limited beneficial use, and characterized by very low yield (e.g., <150 gpd) or high TDS.

Title: Exposure Control - Land Use Controls (2 of 2) Text: LUCs are used if exposure control is required at a given site. LUCs are restrictions and administrative tools used to protect human health and the environment from potential exposure to residual contamination. LUCs are appropriate when a site cannot support unrestricted use and unlimited exposure. When considering LUCs as part of the remedial strategy, consideration is given for the existence and purpose of the LUC, where they will be necessary, and the entities responsible for implementing, monitoring, reporting on, anticipated future land use, and enforcing the LUCs. There are two categories of LUCs: engineering controls (ECs), which consist of engineered or physical controls, and institutional controls (ICs), which consist of administrative and/or legal mechanisms. As shown here, there are four main categories of ICs: governmental controls, proprietary controls, enforcement and permit tools with IC components, and informational devices. Visual Description: Table listing the type of institutional controls, purpose, example and enforcement.

Title: Source Control Text: Source control is a key element to consider because the source acts as a reservoir for continued contaminant migration. If sources are identified, risk can be reduced by ensuring the source is either contained/treated or viewed to be stable and not contributing to the existing plume. Partial source zone treatment should be evaluated for the potential to reduce both the timeframe and cost of downgradient plume treatment. It is sometimes a cost-effective approach to first accomplish partial source zone treatment with an active mass removal/destruction technology and to subsequently use monitored natural attenuation (MNA) as a polishing step. The potential benefits of partial source zone treatment include reduced contaminant mass flux, reduced time of remediation, and more favorable conditions for MNA. Visual Description: Graphic illustrating DNAPL source zone, control plane, dissolved plume and compliance plane for (1) pre-remediation, (2) partial source zone mass removal, and (3) partial source zone mass removal plus enhanced attenuation.

Title: Plume Management Strategies - POCs (1 of 4) Text: There are several strategies that may be applied for managing risk associated with groundwater plumes, including establishing points of compliance (POCs), alternate concentration limits (ACLs), performing mixing zone analyses, technical impracticability (TI) waivers, and ARAR waivers. POCs are the points at which the remedial action objectives are applied, and at which groundwater monitoring is conducted to demonstrate compliance. POCs can be designated at mutually agreed upon locations that are consistent with the CSM and linked with in-place plume management strategies (i.e., monitored natural attenuation). RPMs should evaluate whether or not a POC strategy is applicable to their site. Visual Description: Graphic illustration shows a top view of source zone, plume boundary, point of compliance property boundary, and groundwater flow direction which is from the source zone to the property boundary.

Title: Plume Management Strategies - ACLs (2 of 4) Text: ACLs can be proposed under CERCLA for contaminants in groundwater. ACLs can be applied if: 1) there is a point of entry where groundwater discharges to surface water (e.g., near the mixing zone), 2) there is no statistically significant increase of constituents in the surface water, and 3) enforceable measures exist that will preclude human exposure. ACLs are often developed using groundwater fate and transport models and mixing zone analyses for sites where the primary exposure pathway is discharge to surface water. Where ACLs are established as part of a remedy, the Record of Decision (ROD) should identify the applicable standards for which the ACLs have been substituted, and should document specifically how the site meets the specific conditions required by the statute. The ROD also should explain the process used to establish the ACLs and how the ACLs are protective of human health and the environment. Visual Description: Graphic illustration shows a top view of source zone, plume, groundwater flow direction toward surface water, plume, Qplume and Qstream.

Title: Plume Management Strategies - Mixing Zone (3 of 4) Text: If the groundwater plume is expected to discharge to a surface water body, consideration must be given to the impact of the discharge on surface water quality. Groundwater fate and transport modeling may be used to simulate discharge to surface water, but can also be used in conjunction with field measurements to ensure accurate predictions. One management option available for groundwater plumes discharging into surface waters is the use of a mixing zone analysis. A mixing zone is described as a limited area or volume where the initial dilution of a discharge occurs. Many State surface water regulatory programs allow for mixing zones for National Pollutant Discharge Elimination System (NPDES)-permitted discharges into surface waters. Although this is commonly applied to point source discharges, groundwater discharge to surface water is a similar process that can be considered for application. Visual Description: Aerial photograph of a contamination site with source and contaminant plume area highlighted.

Title: Plume Management Strategies - Waivers (4 of 4) Text: Restoration of contaminated groundwater to drinking water quality may not always be achievable due to limitations of available remediation technologies and hydrogeologic conditions. A TI waiver may be invoked during a remedial action if restoration of groundwater to cleanup levels (e.g., ARARs) is technically impracticable from an engineering standpoint, based on the feasibility, reliability, and cost of the engineering methods required. TI waivers generally will be applicable only for ARARs used to establish cleanup performance standards or levels, such as chemical-specific MCLs or state groundwater quality criteria. TI decisions may be made either during development of the decision document or after the remedy has been implemented and monitored for a period of time.

Title: Remediation Strategies (1 of 3) Text: If it is determined that treatment technologies are required and feasible, several strategies can be applied to remediate and manage groundwater plume sites. Often remediation efforts can be optimized by utilizing a treatment train approach that combines active and passive technologies and relies upon well-defined performance objectives and exit strategies. Source zone treatment alternatives can also be evaluated to determine if reductions in the overall timeframe and cost of plume cleanup can be achieved by targeting hot spots to remove a large amount of mass in a relatively short time period. These strategies can be used to develop appropriate remedial action objectives for a site and to optimize the overall remedial approach. Typically, No Further Action (NFA) or risk-based closure is the preferred approach for sites where the risks posed are low. If, however, remediation is required due to high site risks, remedial options should be evaluated from passive to active technologies as shown here. Visual Description: Graphic listing of treatment technologies from passive to active technology: NFA, MNA, In Situ Passive (e.g., emulsified vegetable oil injection), In Situ Active, Low to Moderate Intensity (e.g., air sparging, bioremediation through groundwater recirculation), In Situ Active, High Intensity (e.g., thermal surfactant), and Ex Situ, Active (e.g., pump and treat).

Title: Target Treatment Zones (2 of 3) Text: A target treatment zone is the volume, area, or media for which the remedial action is determined to best apply. The target treatment zones are defined by the CSM and remedial action objectives, considering risk reduction, exposure routes, capabilities of existing remediation technologies, and the nature and extent of contamination. Target treatment zones for a groundwater plume may include: Source zone Dissolved plume Localized areas with elevated concentrations within the plume Localized areas within plume where exposure is occurring (e.g., impacted drinking water supply well) Downgradient boundary of the dissolved plume Groundwater/surface water interface Visual Description: Table of target treatment zones, treatment technologies, and management strategies.

Title: Treatment Trains and Exit Strategies (3 of 3) Text: Treatment trains can include the use of multiple remedial technologies over time in the same target treatment zone or the concurrent use of multiple remedial technologies over various locations of a large plume. Performance objectives should be developed and clearly defined for each stage if a treatment train approach is implemented. This will allow for transition from more active to more passive treatment technologies over the life of the project. Defining a quantifiable performance objective can sometimes be challenging. Click here for one example for a light non-aqueous phase liquid (LNAPL) site. The series of performance objectives defined for each stage of the project then form the basis of the overall exit strategy for the site. The exit strategy will determine when it is time to stop, modify, or change a particular technology, or terminate all remedial actions. Performance objectives for each technology in the treatment train and the overall exit strategy should be developed and documented in the Feasibility Study (FS), ROD, and RD phases. Visual Description: Aerial photograph of source zone and plume with color coded area for source area (50-100+ mg/l), high dissolved (20-40+ mg/l) and fringe, low dissolved (5-1300 ug/l).

Title: Example Performance Objective for LNAPL Site Text: For LNAPLs, a performance objective might be defined as "Recovering LNAPL to the extent practicable," but practicable is not defined up front. A possible alternative performance objective that is quantifiable would be as follows: "Recover LNAPL until the price of recovery is two orders of magnitude higher than the price of crude oil." Quantifiable metrics can be developed for other COCs.

Title: NAS Jacksonville - Introduction (1 of 4) Text: Operable Unit (OU) 3 at Naval Air Station (NAS) Jacksonville is located on the western bank of the St. Johns River. Historical site activities conducted at OU 3 included rework, repair, and modification of aircraft engines and aeronautical components. As part of the industrial activities, there were reports of past releases of hazardous substances onto or into the ground at OU 3. Several investigations and removal actions have been undertaken throughout OU 3 since 1982, and two interim remedial actions were implemented at Buildings 106 and 780 in 1998. Building 106 was the site of a former dry cleaner and Building 780 was the site of a former paint shop and chemical stripping facility. In addition to contamination at Buildings 106 and 780, seven named groundwater plumes were identified (Areas A through G) at OU 3. Visual Description: Aerial photograph of OU3 at the Naval Air Station, Jacksonville. Building 780 and former building 106 are labeled.

Title: NAS Jacksonville - CSM (2 of 4) Text: OU 3 is underlain by interbedded layers of sand, clayey sand, sandy clay, and clay. Groundwater, and the migration of contaminants, is controlled by a complex stratigraphy. The surficial aquifer is divided into an upper and lower zone by an extensive low permeability clay layer. The upper groundwater zone is slower moving and influenced by storm sewers, while the lower groundwater zone is faster moving and discharges to St. Johns River. The primary contaminants of concern (COCs) identified at OU 3 include tetrachloroethene (PCE), trichloroethene (TCE), 1,1-dichloroethene (1,1-DCE), and vinyl chloride (VC). Elevated contaminant concentrations in groundwater indicate the potential for residual DNAPL in the vicinity of Buildings 106 and 780. Current and anticipated future land use is industrial, and there is currently no groundwater use at the site. The primary exposure pathway is groundwater discharge to surface water in St. Johns River. Visual Description: Cross sectional graphic view of the underlay at OU3 shows interbedded layers of sand, clayey sand, sandy clay and clay. Leaking stormwater drains, top of water table, sea wall, upper layer, river, sand/clay, low-permeability clay, intermediate layer, and sand/clay are illustrated.

Title: NAS Jacksonville - Plume Management (3 of 4) Text: Remedies for Buildings 106 and 780 were implemented as interim remedial actions and later selected in a final ROD for OU 3. Air sparging with soil vapor extraction was implemented at Building 106 and groundwater extraction and treatment with soil vapor extraction was implemented at Building 780. Performance based interim remedial action objectives were established, rather than quantitative cleanup goals. The remedial action objectives included: Reduce present or future risks posed to human health and the environment; and Reduce contaminant concentrations in hot spots or source areas to adjacent levels of contamination. After six years of operation, COC concentrations remained elevated compared to concentrations measured during preparation of the Engineering Evaluation and Cost Analysis (EE/CA); therefore, the 5-year review concluded that the treatment systems were not achieving the design goal of source removal and would be ineffective as a final remedy. Visual Description: Aerial photograph of OU3 at the Naval Air Station, Jacksonville. AS/SVE area and GW extraction/SVE area are highlighted.

Title: NAS Jacksonville - Plume Management (4 of 4) Text: An optimized remedial strategy is now being developed for OU 3 which includes a risk management approach. Discharge of groundwater to St. Johns River as the primary receptor is the focus of the new risk management approach. In order to support the new approach, a direct push technology and membrane interface probe (DPT/MIP) investigation was completed as shown here to update the CSM by compiling additional information regarding site geology and extent of contamination in the soil and groundwater. Under Florida's risk-based cleanup rule, the updated CSM will be used in the groundwater fate and transport model and to perform a mixing zone analysis, which will be the basis for developing ACLs as new groundwater cleanup standards. ICs will also be developed for OU 3 to prevent exposure to contaminated soil and groundwater remaining at the site. Visual Description: Results from a direct push technology and membrane interface probe (DPT/MIP) investigation shows total VOCs concentration levels near the former building 106 and building 780.

Title: NSWC Crane - Introduction (1 of 4) Text: Naval Surface Warfare Center (NSWC) Crane is located in south central Indiana and encompasses approximately 62,463 acres. It is located in a rural, sparsely populated area and most of the facility and surrounding area is forested. Industrial activities that have taken place there include production and operations related projectiles, bombs, mines, pyrotechnics, and rockets. Other operations have included demilitarization, ordnance disposal (through demolition and burning), solid waste disposal, small arms ranges, vehicle maintenance, and other activities. Solid Waste Management Unit (SWMU) 3 is designated as the Ammunition Burning Grounds (ABG). Since the 1940's, pyrotechnics, explosives, and propellants were disposed of using the "Open Burning"(OB) method. In the past, the material was burned directly on the ground in pad/pits and prior to 1982 unlined impoundments existed for liquid waste disposal. RDX, TCE, and metals (barium) were identified as COCs in groundwater during the RCRA Facility Investigation. Visual Description: Map of Naval Surface Warfare Center (NSWC) Crane showing the main treatment area, Karst Conduit, Little Sulphur Cr., and Spring A, A'.

Title: NSWC Crane - CSM (2 of 4) Text: SWMU 3 is underlain by Big Clifty Sandstone and Beech Creek Limestone formations. It has been demonstrated with hydrologic and dye tracer studies that groundwater from SWMU 3 converges toward a karst conduit that subsequently discharges through surface springs to nearby Little Sulphur Creek. Surface water samples along portions of Little Sulphur Creek have indicated trace levels of RDX. RDX concentrations have been shown to decrease downstream of the springs due to dilution/mixing effects. Visual Description: Cross sectional graphic of the main treatment area showing precipitation, surface soil, infiltration pathway of contaminant, fractured bedrock, bedrock surface, groundwater table surface, groundwater flow and contaminant migration through bedrock (minor pathway), Karst Channels, collapse zone, and layers (Overburden, Big Clifty Sandstone, Beech Creek Limestone).

Title: NSWC Crane - Plume Management (3 of 4) Text: Several remedial option alternatives were considered for SWMU 3 as follows: Constructed Wetlands This option was eliminated due to seasonal effectiveness issues (e.g. slow plant growth/biological activity in winter); potential for washout with 10,000 gpm peak flows; and limited land availability. Pump-and-Treat This option was eliminated due to challenging lithology with a fractured bedrock and karst system; highly variable flows; and potential for high O&M costs over long-term. Risk Management This option was accepted by the regulatory stakeholders and included LUCs to protect current uses of ABG and Little Sulphur Creek, along with ACLs based on a site-specific risk assessment. Visual Description: Map of NSWC Crane site with contaminant concentration level sample points.

Title: NSWC Crane - Plume Management (4 of 4) Text: There were several considerations that contributed to stakeholder acceptance of the risk management strategy. Significant natural attenuation of the existing contamination was occurring over time. The current and future land use is a RCRA-permitted OB treatment unit on property owned by the Navy. This will facilitate implementation of LUCs to prevent exposure for on-site workers and exclude groundwater use. In addition, SWMU3 is not a viable ecological habitat due to ongoing use of the OB treatment unit. ACLs for the springs were then calculated in order to achieve Indiana Water Quality Standards (WQS) for point source discharge limits. The proposed water quality based limits for RDX are a maximum of 140 ppb for RDX discharging from the spring, 240 ppb for surface water (non-potable), and 3 ppb for public water supply located 11 miles downstream (at point of intake). Visual Description: Graphic plot of RDX, TCE concentration versus distance.

Title: Conclusions Text: For more detailed information on the risk management concepts discussed in this Web tool, click here to download the companion handbook. In conclusion, several challenges may arise during the development and implementation of a risk management approach and additional resources to meet these challenges are below. Regulatory Acceptance. Each state has its own risk-based methodology and specific criteria for risk management approaches. Some states have “anti-degradation” policies, which limit the use of risk-based cleanup strategies. For information regarding risk assessment issues, view the Navy Environmental Health Center (NEHC) Guidance for Conducting Human Health Risk Assessments. Planned Use of the Property. For BRAC facilities, previous land use could change, potentially resulting in changing exposure risks. Where contamination remains onsite, it is important to anticipate long-term legal and financial factors related to the presence of contamination and how changing land use or site alteration may affect exposure risks. However, when evaluating future land use scenarios, only reasonably anticipated future land use should be considered. Use of Institutional or Engineering Controls. The willingness and ability of the appropriate entity to implement, maintain, and monitor the ICs or ECs is another factor of importance. In some cases, a third party is responsible for LUC maintenance, although the Navy retains the overall responsibility for the site. Even where the Navy remains in control of the site, LUCs may need to remain in place for many years spanning multiple personnel responsible for LUC maintenance. To assist the RPM in maintaining LUCs, the Navy has developed LUC Tracker, which is a Web-based management tool that has been deployed as part of the Naval Installation Restoration Information System (NIRIS). Community Acceptance. Community acceptance of the selected approach should be evaluated. For information regarding risk communication, visit the NEHC Risk Communication Navy Health, Operational and Environmental Web site.

Title: Contact Text: For more information, please contact: NAVFAC ESC POC PRTH_NFESCT2@navy.mil