Currently, industrial hygiene does not appear to be as fully integrated into the planning, pre-job, execution, and post job ALARA review to the same extent as the radiological control program. Moreover, the industrial hygiene group does not have a dedicated professional that reviews pre-job plans as his/her main function. The current staffing and skills training level of the industrial hygiene function at WRPS does not make available adequate industrial hygiene expertise necessary to assure issues relating to chemical vapors in the tank farm are properly addressed and consequently industrial hygiene expertise is not always recognized as a valuable asset to the success of an overall work plan.
In addition to not being able to participate in all critical work activities, some focus group members voiced concerns that the industrial hygiene function lacks the expertise, training, empathy, and monitoring tools to recognize acute, episodic vapor events and the fact that vapor events are occurring. The strong adherence to occupational exposure levels (OELs) or a fraction thereof and relying on results of sampling performed well after the event as evidence that episodic exposures have or have not occurred undermine the credibility of the function and their ability to ultimately protect workers. Similar observations have been made by past evaluations of the industrial hygiene program. Breysee and Stenzel (2010) similarly concluded that some industrial hygiene staff may not fully appreciate the possibility for over exposures at the site, and therefore may not be open to considering that ill effects reported by the workers could be job related.
Recommendation RM4
Adequately staff the industrial hygiene function to assure proper resources is deployed in the planning, pre-job, job execution, and post-job ALARA review in a similar fashion to that of the radiological control function.
This should include a team of industrial hygiene professionals dedicated to the work planning activities.
In addition, the industrial hygiene function must be properly trained to recognize that the current reliance on 10% OELs and long term or after-the-fact monitoring results is insufficient to properly characterize all vapor exposures that are occurring at the Hanford tank farms. The communication skills of the industrial hygiene staff must also be improved to properly explain the meaning and limitations of industrial hygiene assessments and to show a proper degree of empathy for worker concerns regarding vapor events. To this end, management and industrial hygiene staff should frequently engage staff to solicit feedback regarding the industrial hygiene function performance and areas where communications can be improved. One method to achieve this is to create frequent employee focus groups, different from normal working groups such as CVST and IH Technical Committee, so as to receive general employee feedback on program performance, communications, employee concerns, etc.
RM TECHNICAL ISSUE 5: METHODS FOR DEFINING, COMMUNICATING, AND MANAGING RISK Observations:
As discussed in the previous chapters, WRPS has generally defined unacceptable exposure and risk to tank vapors as greater than 10% of the established or assigned Occupational Exposure Limit (OEL), associated with what has been identified as chemicals of potential of concern (COPCs). Most OELs are based on the American Conference of Governmental Industrial Hygienists’ TLV-TWA or derived 8-hr TWA OELs and have been established to minimize chronic health risk and are typically assessed via long-term monitoring techniques. The vast majority of worker exposure reports are associated with very short exposure events that may exist for just seconds or a few minutes.
The current exposure assessment strategy, while appropriate for longer-term and more chronic conditions, is not suitable for short-term, episodic and acute chemical exposures that may occur in the tank farms. In addition, the current exposure assessment strategy for long-term and short-term assessments depends to a great extent upon monitoring results associated with a select number of known chemicals and in the case of vapor incidents, results from samples often collected well after an event has occurred. The industrial hygiene function is appropriately using 8-hr TWA OELs to characterize chronic exposures in accordance with 10 CFR 851; however, it is the TVAT’s belief that the currently established OELs are not necessarily applicable to the short-term, episodic exposures occurring on the tank farms. (See Chapter 5, “Exposure Assessment,” and Chapter 6, “Dose-Response Assessment.”)
Recommendation RM5
Redefine unacceptable chemical exposure risk to include short-term, episodic exposure to chemicals that can result in adverse health impacts.
The definition of potential health impacts should take into consideration observable physiological signs of exposure and symptoms experienced by workers.
WRPS should further characterize chemicals that may be released into the tank farm and evaluate their potential to cause adverse health impacts as defined above, after episodic, short term and long term exposures, as discussed in Chapter 5, “Exposure Assessment,” and Chapter 6, “Dose-Response Assessment.”)
The industrial hygiene function should modify its exposure assessment strategy and more appropriately
characterize and assess potential short term, acute exposure risks in addition to long term, chronic exposure risks. Some of the resources associated with long term monitoring could be redirected to short term assessments. The industrial hygiene function should utilize the most technologically advanced fixed and portable direct reading instrumentation to assess vapor events and predict vapor events in order to establish appropriate controls to assure workers are not adversely impacted by tank farm vapors. In addition, the industrial hygiene function should work with equipment manufacturers to develop more effective, direct and continuous monitoring instrumentation for assessing episodic vapor events on a real-time basis.
WRPS and DOE should develop a long term research and development plan to address the technical gaps in our understanding of the health risk associated with episodic exposure to tank farm vapors and develop more effective methods to assess and control risk associated with worker exposure to vapor from DOE tank farms.
RM TECHNICAL ISSUE 6: ENGINEERED CONTROLS: ENGINEERED CONTROLS TO MANAGE EXPOSURE AND HEALTH RISK
Observations
The emphasis with respect to investigation of engineered controls has been on end-of-pipe stack controls in conjunction with active ventilation of the tank head spaces. There has been a prevailing assumption that the exposure events are related to vapor releases directly from the tank head spaces and that these releases could be
controlled by actively venting the tank head spaces and either routing the vapors to control devices or expelling the vapors through stacks having exhaust outlets farther removed from the work space (either vertically or
horizontally) than is presently the case. For example, the CH2M Hill Feasibility Study for Control of Vapors from
Waste Storage Tanks evaluated numerous technologies, and all but one was an end-of-pipe control option for
actively vented stacks (Baker 2004). The Baker report expressed the belief that maintaining negative pressure in the tank head space would prevent release of tank vapors from all locations except the exhauster stacks. However, this was in the context of evaluating the operation of active tank ventilation and as such did not address passively vented tanks, nor did it address potential sources of vapor release other than the tank head spaces.
The Baker study noted that end-of-pipe control options had been previously evaluated in terms of environmental compliance, and all of the technologies considered were determined to exceed the cost criteria established by the Washington Department of Ecology for best available control technology for toxics. The Baker study further concluded that most of the then-available technologies did not appear to be technologically feasible for the Hanford tank situation, but identified three alternatives to be advanced for sizing and estimation of capital and operation and maintenance costs (Baker 2004). These alternatives were
1. A thermal oxidizer: The suggested scheme included an ammonia scrubber in front of the thermal oxidizer, and a quencher and acid scrubber after the thermal oxidizer.
2. A carbon adsorption system: The suggested scheme included an ammonia scrubber in front of the carbon system, followed by a cooler to reduce temperature and absolute humidity of the vent stream prior to entering the carbon adsorption system.
3. A biofiltration system: There was scant description of this alternative.
To date, no end-of-pipe controls have been installed on the exhauster stacks, but there are active investigations of engineered controls currently under way. Both the Engineered Controls and the New Technology sub-teams of the Chemical Vapor Solutions Team are engaged in these investigations.
The Baker study considered one alternative that was not strictly an end-of-pipe control, but rather was an area- wide measure. This alternative was the use of orchard fans to maintain a sweep of air across the tank farms during calm weather periods. Baker noted that this would involve relatively low capital cost with short delivery and installation time, but concluded that it would likely not eliminate odor concerns and would not remove contaminants from the air (Baker 2004). However, the report failed to address the potential of these fans for minimizing short-term exposure to isolated vapor puffs having high chemical concentrations.
The only engineered control that has been selected for implementation to date has been to increase the height of the vent stacks. A 2010 study, reported by Breysse and Stenzel in the Independent Review Panel Report on
Chemical Vapors Industrial Hygiene Strategy, recommended consideration of scrubbers or extending stack
heights (Breysse 2010). The site subsequently investigated these recommendations and concluded that stack extensions would be more effective than scrubbers. Some of the active venting stacks have subsequently been extended from about 25 feet to about 40 feet in height, and stack extensions for other exhausters are stored on site waiting for installation.
There are several fundamental flaws to the hypothesis that stack controls would entirely solve the vapor exposure problem. First, stack controls rely on active venting, and active venting relies on uninterrupted power supply. In reality, power to the exhausters is sometimes interrupted. Some interruptions are intentional, such as for switching between exhauster trains, while others are unplanned, such as loss of power due to a power pole collapsing in the wind. When power to an exhauster is interrupted, vapors may escape through alternative pathways, resulting in episodic fugitive emissions. Given the frequency of power interruptions, a control system that relies on
uninterrupted power supply cannot, by itself, prevent episodic uncontrolled releases of vapors.
Another flaw inherent to reliance on stack controls is that certain exposure incidents have been associated with maintenance activities, such as removing foam from cover blocks or removing wrapping from RCEs. Exposures due to incidents such as these would not have been prevented by stack controls.
Furthermore, there are potential fugitive sources that would not be subjected to negative pressure by active ventilation of the tank head spaces. These include but may not be limited to waste isolation disposal sites, RCEs, transfer lines, and valve pits. These potential fugitive sources would not be expected to be continuous sources of emissions, and many of them may not be likely sources of emissions at all. At best, emissions from these fugitive sources would be expected to be infrequent and episodic. Given, however, that the vapor incidents also have been infrequent and episodic, these potential fugitive sources should be considered.
Recommendation RM6
Investigate and implement best available technologies to detect and control vapor plumes from fugitive sources as well as from vents and stacks.
Improved detection technology and procedures are needed in order to better define the origins of the short-term episodic releases, thereby informing the effective use of engineered controls. Include continuous surveillance of the tank farms by platform-mounted optical gas imaging cameras among the technologies to be evaluated, and investigate equipping this detection technology with an alarm or warning system. In the absence of knowledge as to the origins of the releases, a great deal of money could be spent on speculative measures that may have little benefit for protecting workers.
Continue to investigate control options for active venting and stack controls, and develop separate strategies for exhauster downtime and fugitive sources. Active venting has the benefit of maintaining a negative pressure in the tank head space, thereby preventing loss of head space gases through fugitive pathways, and routing the vapors either to a control device or to a safe exhaust location. Options to be investigated include using exhausters (permanently or temporarily, as appropriate) for actively venting tanks that are presently passively vented, increasing stack heights, using air flow promoters on the stacks to enhance dispersion of the stack exhaust,
relocating stacks away from the work areas (“stack in the sticks”), and routing exhaust from the stacks to a control device. Resolve the efficacy of the three control technology alternatives identified in the 2004 Baker study (Baker 2004), as well as other promising technologies that may have been identified more recently. However, given that stack controls alone will not entirely eliminate short-term vapor exposures; develop separate strategies for exhauster downtime and for fugitive sources. Strategies to consider include the use of large fans to sweep air across the tank farms (orchard fans), and box fans at passive vents to enhance dispersion. Certain potential exposure scenarios, such as during various maintenance operations, may be outside the realm of engineered controls altogether and require procedural controls.
Investigate detection devices which are triggered by changes in the concentrations of selected chemical species in real time, and which are equipped with an alarm system to warn personnel of an increased level of vapor
concentration. Evaluate these alarming devices for use as ambient monitors in areas of known fugitive emissions, and as in-line monitors for vent and stack emissions, and implement appropriate devices upon being demonstrated to be effective.
RM TECHNICAL ISSUE 7: MANAGEMENT OF ADMINISTRATIVE CONTROLS AND PERSONAL