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Remediation Technologies Screening Matrix, Version 4.0  
Chapter 16 Precipitation
Table of Contents


16-2 Hazard Analysis

Principal unique hazards associated with precipitation include:

Physical Hazards Chemical Hazards Radiological Hazards Biological Hazards

a. Physical Hazards

(1) Description: Solids from the precipitation process may plug waste lines if the rate of precipitation exceeds the rate of solids removal.

16-1 Typical Process Flow for Precipitation

Plugged waste lines may cause tanks to overflow, causing slippery conditions. Also, due to the wet environment and the use of electrical equipment, workers may be exposed to electrocution. Overpressure in lines may also rupture piping or pumps.

Control: Equipment to help prevent lines from plugging, such as auger-equipped waste lines or flow controls, may be used to help prevent plugged lines and overflowing tanks. Hazard warning alarms may be installed to alert operators of system over-pressurization. Adequate spacing should be left between equipment so that it can be safely maintained. Verify that the hazardous area classifications, as defined in NFPA 70-500-1 through 500-10, are indicated on the drawings. All controls, wiring, and equipment, both temporary and permanent, should be in conformance with the requirements of EM 385-1-1, Section 11.G and NFPA 70 for the identified hazard areas. Equipment should be grounded and/or provided with ground fault interrupter circuit (GFIC) protection if required by EM 385-1-1, Section 11 or NFPA 70 requirements. Only trained and experienced workers should be permitted in the areas. CONTROL POINT: Design, Operations, Maintenance

(2) Description: Emergency shower/eye wash equipment required per 29 CFR 1910.151 is not always provided with adequate floor drains, thereby creating potential electrical hazards or walking surface hazards during required testing/use.

Control: Showers/eye wash equipment should be equipped with accompanying functional drains to isolate and collect the shower/eye wash water from unprotected electrical equipment and walking surfaces that, when wet, create slipping hazards. CONTROL POINT: Design

b. Chemical Hazards

(1) Description: Precipitation treatment may expose workers to corrosive chemical reagents (e.g. HCL, lime, sodium hydroxide, carbonate salts, sulfide salts, etc.) used in the process. The reagents may be in powder or liquid form, and may pose an exposure hazard through either inhalation, dermal and/or ingestion routes. These reagents may corrode piping system components. Some chemicals used in the precipitation process are hygroscopic (water absorbing), and may develop unwanted reactions in the presence of moisture.

Control: Controls to help minimize worker exposures may include the delivery of chemical reagents (e.g. lime, sodium hydroxide solutions, etc.) through a closed system, and/or the use of personal protective equipment (e.g. an air-purifying respirator using cartridges appropriate to the reagents). Material Safety Data Sheets (MSDS) should be consulted prior to handling reagents to determine the specific chemical hazards associated with the chemicals. Hygroscopic chemicals should be stored separately from other chemicals in air-tight containers. Design considerations should also include the appropriate materials for piping and system components. CONTROL POINT: Design, Operations, Maintenance

(2) Description: If the addition of chemical reagents in oxidation/reduction reactions is not properly controlled, then the reaction may proceed uncontrollably, causing a buildup of heat and pressure that causes a release from the system. The release may involve worker exposure to chemical reagents or waste material. Exposure may cause irritation or chemical burns to eyes, skin, and respiratory tracts.

Control: Flow controls may be needed to help prevent addition of excessive amounts of chemical reagents (e.g, hydrochloric acid, sodium hydroxide, lime, etc). The oxidation/reduction reagents should be stored in separate areas under cool, dry conditions. Pressure-relief systems and over- pressurization alarms must be part of the process design. An automatic shutoff should be installed to prevent the overflowing of storage tanks. Chemical piping should be located low to the ground, if possible, in case of rupture. If pipes are subject to moisture buildup, provide insulation on pipes to prevent slipping hazards. CONTROL POINT: Design

(3) Description: Sludge from the treatment process may have a high pH, which may cause skin burns for workers handling the material.

Control: Controls for this hazard may include neutralization of the sludge prior to handling, or the use of personal protective equipment such as rain gear, rubber gloves (e.g. butyl rubber for hydrochloric acid or sodium hydroxide), and splash shields. CONTROL POINT: Design, Operations, Maintenance

(4) Description: The process may form metal sulfides, which may generate toxic gases (including hydrogen sulfide), or the sulfide sludge may spontaneously combust.

Control: Controls to help prevent worker exposure to hydrogen sulfide include local ventilation to remove the gas from the work area, process tanks and vessels, pH control to keep the sulfides alkaline, and water control systems to keep sulfide filter cakes moist. Due to the potentially fatal consequences of overexposure to hydrogen sulfide gas, a hydrogen sulfide monitor should be installed in these areas where the generation of H2S is most probable. Monitors should be set to alarm at 10 ppm. Emergency escape respirators should be available for all operators in the event of a catastrophic system rupture or uncontrolled reaction that would liberate excessive amounts of H2S. CONTROL POINT: Design, Operations, Maintenance

(5) Description: Workers may be exposed to acids or bases used for pH adjustment.

Control: The secondary containment storage areas for acids and bases should be constructed of materials compatible with storage of these materials and clearly marked. Acids and bases should be stored in separate areas. Emergency showers and eye wash stations that comply with 29 CFR 1910.151(c) and the design requirements specified in ANSI Z358,1 (1990) should be located near the reagent storage areas. Handling of pH agents should be automated to the extent practical. An emergency plan should be prepared and facility personnel should be trained to safely handle acids and bases. Manual handling of acids and bases should be done by personnel familiar with their properties and equipped with personal protective equipment (PPE), such as leather or rubber acid-resistant boots, chemical-resistant coveralls, goggles and face shields, air-purifying respirators (as indicated by the reagent), and rubber or other acid and base resistant gloves (e.g. nitrile) or gauntlets. CONTROL POINT: Design, Operations, Maintenance

(6) Description: Permanent or semi-permanent treatment buildings may present life safety hazards such as inadequate egress, fire suppression systems and/or emergency lighting systems.

Control: Permanent and semi-permanent treatment system buildings should be constructed in accordance with ANSI 58.1: Minimum Design Loads for Buildings and Other Structures; the National Fire Code; the National Standard Plumbing Code; Life Safety Code; and the Uniform Building Code. Depending on where the project is located, the structures must also comply with either the Air Force Manuals on Air Force bases, the USACE Technical Manuals on Army installations, or Local Building Codes on Superfund, BRAC, or FUDS sites. CONTROL POINT: Design, Operations

c. Radiological Hazards

Description: Many radioactive materials and naturally occurring radioactive materials (NORM) are metals, and if present in the water may be precipitated out and concentrated. This hazard may be considered out of the ordinary for this technology. Some radioactive materials may present an external exposure hazard. All radioactive materials may present an internal exposure hazard through inhalation or ingestion.

Control: Should elevated levels of radioactive contaminants be present in the groundwater, a qualified health physicist should be consulted to determine the exposure potential and any necessary engineered controls or PPE. CONTROL POINT: Maintenance

d. Biological Hazards




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