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Chapter 6
Maintenance Facilities Management
6.3. Yard and Floor Drain Management

Many DOT facilities have floor drains in buildings and surface drains in the "yard" that discharge washwater and stormwater through underground pipes or open ditches, a ditch, or a right-of-way culvert, or off-site to a neighboring property and, potentially, to the waters of the state. Shop floor drain effluent can include motor vehicle fluids spilled as a result of vehicle maintenance and repair, and washbay washwater, especially from salt truck and salt bed washing during snow and ice season. Flows off of maintenance yards may ultimately reach waters of the state, either indirectly or via direct discharge into a side ditch.

Discharges from floor drains to surface and groundwaters are generally regulated through the National Pollutant Discharge Elimination System (NPDES) and state administered NPDES programs, often called SPDES. NPDES/SPDES permits are issued and required for discharges to waters of the state. Some facilities have installed oil/water separators as interceptors; however, such separators are not effective in removing soluble contaminants such as salt from the discharge.


6.3.1 Procedural Practices and Other Non-Structural BMPs
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Stormwater/Washwater BMPs for Surface Runoff

Much of the impact from surface stormwater/meltwater runoff can be significantly reduced by removing contaminants from the path of the sheet flow and point discharges.

  • The salt/sand mixing/loading area should be swept clean after each load.
  • The salt/sand mixing/loading area should be bermed to contain the material until it can be cleaned or the mixing/loading is performed inside the salt storage facility or under a roof. Where paved berms have not been installed, Indiana DOT recommends that A windrow of abrasives [sand] should be placed around all outside stockpiles [salt, salt/sand mix piles]. [N] While minimally effective as a deterrent to stormwater/meltwater runoff, especially from a sloped surface, on level surfaces such windrows can allow pooling that would otherwise sheet flow around stockpiles causing migration of salt-contaminated stormwater off-site.
  • Containers of petroleum and liquid wastes stored outdoors are on a roofed pad enclosed by secondary containment.
    • Herbicide and paint mixing and loading should be done in designated, bermed areas, preferably on a pad.
    • Any spill or residue should be immediately cleaned up.
  • Right-of-way trash and construction debris should be taken to a permitted landfill and not allowed to accumulate on site.
  • Salt bed washing should be performed in a washbay, not outdoors, and salt bed oiling, paint chipping and painting, if performed at the salt bed rack, should be done with the ground protected by a tarpaulin.

Structural BMPs

Structural BMPs are installed at most DOT facilities to reduce the offsite impacts of contaminated stormwater/washwater migration, though most of these have been added since construction.

  • Standard specifications for new salt storage buildings should include sufficient area for:
    • sand storage and salt/sand mixing/loading indoors
    • brine making
    • storage and bulk tank loading outdoors on a pad protected with secondary containment. [N]
  • The exterior pad (to the salt storage building) should be sloped away from the building to its outer limits and the water retained by means of a curb or slope reversal of the pad itself in order that the runoff may be directed into a collection system.
    • The design of the exterior pad (where the mixing/loading operations are performed) should be mandated, not recommended, because the lack of exterior pad curbing has created over half of the salt contaminated stormwater problems observed in at least one DOT survey. [N]
    • The curbing should only be used to allow pooling or to direct stormwater to a collection system. It should not be employed to direct stormwater offsite, as a point source discharge.
  • Roofs should be extended on old salt domes to provide a protected area for mixing/loading and for replacement of smaller salt storage facilities.
  • Design and specification of structural BMPs should include central office staff and adherence to specification, with input from field personnel to avoid stormwater/washwater collection/discharge problems resulting from poor design.

The following practices are recommended for stewardship of water quality, runoff from maintenance yards and potential discharges from floor drains.


6.3.2 Floor Drain Management
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Caltrans, Maine DOT, and NYSDOT utilize some of the following environmental stewardship practices for floor drain management. [N] [N]
  • Direct discharges from floor drains to groundwater through leach fields, septic systems, or dry wells should not be allowed.
  • Consider whether a floor drain discharge is truly necessary. If not, plug the floor drains with a plumber's plug or concrete. If the drain is permanently closed and no discharge can occur, a grit collector, oil/water separator and NPDES/SPDES permit would not be required. A permit would be required for a grit collector and oil/water separator that discharge floor drain waters to surface water. Such permits may involve requirements to change vehicle parking patterns and perform vehicle maintenance only in areas away from the floor drains.
  • At facilities that do not discharge shop floor drain effluent to a Publicly Owned Treatment Works (POTW), oil/water separators should be used for washwater. Oil/water separators are effective at removing nonsoluble oil and other petroleum products, but do not remove substance in solution, such as antifreeze and chlorides from road salt. At some facilities, the oil/water separator is connected to a tank, catch basin or holding pond where the washbay effluent collects before being conveyed offsite. A hazardous waste or liquids recycling contractor pumps the contents of the separator or the holding tank, when needed.
  • Shop floor drains should be segregated from washbay drains and the flow should terminate at the oil/water separator or, beyond, at a holding tank. Shop floor drains are intended to capture any spills of automotive fluids occurring during vehicle maintenance. No other liquids, including washwater, should be allowed to enter the drain.
  • Centralize vehicle repair and maintenance at a subdistrict or district shop where possible, to avoid contamination of facility stormwater discharge.
  • Where possible install a grit collector and oil/water separator and connect to a municipal sewer system which eliminates the need for a NPDES/SPDES permit.
  • All floor drains should be are constructed with an oil/water separator as part of the system. All floor drain effluent must be forced to pass through an oil/water separator prior to being discharged from the system (i.e. before flowing to a tank, sewer district pipe, or infiltrated onto the surrounding grounds).
  • Division Managers/Engineers are responsible for knowing where floor drains discharge, and for compliance with the Department Floor Drain Policy. Division Engineers/Managers should keep a current database of the method for managing wastewater from garage floors. This database should include, at a minimum, the presence and type of construction for floor drains and the method of managing effluent. Any changes to the construction or management of this effluent must be reported to the Highway Maintenance Engineer.
  • Hazardous waste containers should be provided with secondary containment where risk of damage is high ( such as from vehicles ) or where impacts from a spill would be severe ( such as spills to floor drains that discharge to the ground ) . Secondary containment must be capable of holding 110 percent of the waste container volume.
  • Weekly inspections of hazardous waste storage areas should be performed.
  • An Emergency Action Plan should be developed in accordance with Bureau of Labor Standards/OSHA (29 CFR 1910.38) requirements for Hazardous Waste Operations and Emergency Response (29 CFR 1910.120(a)(i)(v)) state Emergency Response Planning Procedures for each facility storing hazardous waste.
  • Good spill prevention practices should be used. These include, at a minimum:
    • Keeping waste containers closed when not in use;
    • Protecting containers from damage from vehicles or other equipment;
    • Use of containers that are in good condition (not severely dented or rusty);
    • Use of funnels when pouring liquids into waste containers; and
    • Conducting periodic inspections of waste storage area

Management of Oil/Water Separators

Oil/water separators are tanks that collect oily vehicle wash water that flows along corrugated plates to encourage separation of solids and oil droplets. The oily solids or sludge can then be pumped out of the system through a different pipe. The sludge can be hauled off site, and the wash water can be discharged to vegetated areas or to a treatment plant. There are two types of oil/water separators, one that removes free oil that floats on top of water, and one that removes emulsified oil, a mixture of oil, water, chemicals, and dirt. Choose the separator that fits the needs of the vehicle wash facility.

Each oil/water separator should be cleaned of all liquid and grit at least annually.

  • Once all free-floating petroleum products are absorbed, the liquid may be decanted to the municipal sewer system or to a tank, for final disposal at a waste water treatment facility or hazardous waste location.
  • If there is reason to believe that hazardous materials, other than oils, are in the liquid portion of the oil/water separator, then the Division Engineer/Manager must be notified and arrangements made by a licensed hazardous waste contractor to collect the liquid.
  • All grits are to be treated as special waste and disposed of at a special waste landfill (Norridgewock, Hampden, etc.)
  • Once empty, oil/water separators must be filled with clean water above the bottom of the outflow pipe.
  • Oil-only absorbent materials are to be used to capture free-floating oils that may accumulate in the oil/water separator.

Management of High Risk Effluent

Stewardship practice calls for both high risk and low risk effluent to be managed in one of the following ways:

  • Discharged directly to a municipal sewer system, with knowledge and permission of the local district.
  • Captured in a tank, then transported off-site for final disposal.
    • Highway/Bridge/Traffic Superintendents are to make arrangements for the transport and disposal of the tank contents with either a waste water treatment facility or hazardous waste contractor. Superintendents make arrangements for any analytical testing of the effluent, as may be required by the waste water treatment facility or hazardous waste contractor.
    • Within 4 days of a tank alarm sounding, Crew Supervisors should notify their Superintendent that the contents of a tank need disposal.
    • Bills of Lading, manifests, or other receipts for disposal should be kept at the Division Office for a minimum of 3 years.
  • Crew Supervisors should test the tank alarm system monthly. A log of such tests will be kept on-site for a minimum of three years.
  • The floor drain can be eliminated and the shape of the floor modified such that no liquids exit the garage through a drain system.

Further options exist and are detailed below for management of low risk effluent.

Management of Low Risk Effluent

In addition to the options available for high risk effluent, low risk effluent can also be managed in one of the following ways:

  • When Division Engineers/Managers choose to manage floor drain effluent by separation of activities and bays, the Division Engineer/Managers are to ensure that garage areas where activities could create High Risk liquid effluent are physically separated from the areas where activities create Low Risk liquid effluent. Physical separation includes walls and concrete or polyethylene berms. Berms should also be constructed in a manner that does not allow any waste that could be considered high risk to enter the areas where liquid effluent could be considered low risk. These berms must be constructed in a way that meets OSHA standards for tripping hazards (i.e. meet slope requirements of ADA and are striped as a hazard).
  • Captured in a melt-water only holding tank, pumped to the surface of the ground, and allowed to infiltrate only if the following conditions are met:
    • Connection to a municipal sewer system is not an option.
    • The infiltration area must be accessible for inspection.
    • The effluent must not discharge directly into a ditch, stream, wetland, pond or other surface water body.
    • There must be no significant potential for pollutants to drip, leak, spill or wash into the floor drains from which the effluent originates. Engine maintenance activities are prohibited from areas which feed floor drains discharging to pipes on top of the ground or melt-water only holding tanks. All containers of oils, engine fluids, cleaning products or other liquid pollutants must be removed or separated by means of an impermeable berm from the area containing the floor drain.
    • Oil-only absorbent materials are to be used to capture free-floating oils that may accumulate in the melt-water only holding tank.
    • Discharges must be done in a way that prevents erosion and the creation of pools of standing water. Discharge onto frozen ground is not allowed.
    • Effluent must not be discharged within 300 feet of a private well or water intake or within 2500 feet of a public well or water intake.
    • If there is reason to believe that the contents of the melt-water only holding tank has received oil, diesel or other hazardous materials due to a spill or leak, then the contents cannot be discharged on the surface of the ground. The contents of the tank must them be treated as high risk effluent and disposed of in a manner as described in the previous section.
  • Discharged directly from the floor drain onto the surrounding ground (daylighted) only if the following are met:
    • Connection to a municipal sewer system is not an option.
    • The pipe must discharge on top of the ground to an infiltration area that is accessible for inspection.
    • The pipe must not discharge directly into a ditch, stream, wetland, pond or other surface water body.
    • There must be no significant potential for pollutants to drip, leak, spill or wash into the floor drains. Engine maintenance activities are prohibited from areas which feed floor drains discharging to pipes on top of the ground or melt-water only holding tanks. All containers of oils, engine fluids, cleaning products or other liquid pollutants must be removed or separated by means of an impermeable berm from the area containing the floor drain.
    • Proper erosion control methods are used at the end of the pipe.
    • Effluent must not be discharged within 300 feet of a private well or water intake or within 2500 feet of a public well or water intake.

Floor Drain Maintenance and Sludge Removal

  • Supervisors at garages that contain floor drains are to ensure that floor drains are cleaned a minimum of once per year. The residue removed from the floor drains is assumed to be special waste. Bills of Lading for this disposal are to be kept at the Division Office for a minimum of three years.
  • Crew Supervisors should be responsible for ensuring that all floor drains, oil/water separators, and melt-water only holding tanks have oil absorbent socks maintained in them at all times. These petroleum socks, placed in the floor drains, oil/water separators, and melt-water only holding tanks, are to be changed when they show evidence that oil has been absorbed.

Holding Tanks and Maintenance

Environmental stewardship practice for holding tanks may include: [N]

  • The minimum holding tank capacity must be 1,000 gallons.
  • Holding tanks and piping must be watertight and sealed with materials compatible with the liquid or sludge being stored.
  • Access must be provided to each compartment of the tank for inspection and cleaning by means of either a removable cover or manhole (minimum diameter 20 inches). Manholes must extend to finished grade.
  • The tank must be designed for the expected maximum structural load and ballast must be provided when necessary to prevent structural damage when the tank is emptied.
  • The volume between inlet cover and the maximum water depth must be equal to approximately 20 percent of the liquid volume stored below the maximum water depth. An alarm with both visual and audio signals must be activated once the water level reaches the maximum water depth.
  • A year-end record of pumping events should be produced each year the holding tank is in operation.

Leaks into Floor Drains

If, in the unlikely event, a spill or major leak occurs that allows petroleum or antifreeze liquid to enter a floor drain that was considered low risk, steps must be taken immediately to insure that none of the liquid contaminates the environment through the daylighted pipes, or, tank overflows. If contamination occurs, the steps for major spills must be followed.


6.3.3 Vehicle Washing
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After a storm, equipment cleaned to reduce corrosion damage and to prepare for the next storm. Water used in washing cars, trucks, and other vehicles may contain a wide range of contaminants, including oil, other hydrocarbons, metals, detergents, road salt, and grit. Discharged into surface waters, these contaminants can degrade water quality and harm aquatic life. Discharged into groundwater, potable water may be rendered unpotable.

Various states (e.g., Georgia , Wisconsin , California , Virginia ) are currently conducting studies designed to test the effectiveness of various structural BMPs and investigate the costs of design or purchase, as well as installation and maintenance. State DOTs are exploring some of the following options and environmental stewardship practices: [N]

  • Reduce the sources of potential contamination throughout the state by centralizing saltbed and truck washing at facilities already connected to POTWs amenable to accepting brine discharge. This involves extra driving, and POTWs to which washing facilities are connected may have imposed limits on the volume of washwater or the levels of chloride and cyanide discharged from the facility. Washing facilities may be at such a distance from the others that moving trucks for washing is inconvenient or impractical, regardless of the cost; however, when usable facilities are accessibly located, this is a cost effective option.
  • Connect every truck washing facility to an amenable POTW. Costs of extending the line can be shared with other dischargers in some cases, though some facilities are too remote to make this a practical option.
  • Contain wash water in holding tanks and haul to an amenable POTW. INDOT found this is the most cost effective option for facilities that 1) cannot afford to connect to a POTW; 2) cannot discharge washbay effluent to a POTW because of prohibitions; 3) will install brinemaking equipment and can use washwater as "make-up" solution or 4) will continue to spread road salt for all or some snow/ice events. Vacuum trucks or bulk tank trucks (with a pump), if available, can be used to reduce hauling costs. While some POTWs will not accept transported liquids, a pick-up service might be arranged where amenable POTWs can be located. [N]
  • Line existing and newly constructed holding ponds with a clay layer or plastic impervious liner and design the structure to hold the maximum volume of meltwater, washwater and precipitation that can conceivably collect while evaporation is depended upon to reduce the volume (no overflow is allowed).
  • Install catch basins, settling tanks and holding ponds to remove suspended particles. Dissolved chlorides cannot be removed in this fashion. According to an INDOT/Purdue study, the holding pond should be sized to hold the maximum volume of washbay effluent, surface area stormwater/meltwater runoff (unless the pond is bermed) and precipitation (roofing over a holding pond retards evaporation). Difficulties are encountered removing sediment from any holding pond, but especially one lined with plastic. Unless properly maintained, holding ponds can collect debris and serve as a harbor for algae blooms, wild fowl and reptiles. The cost of constructing a holding pond as a BMP must be weighed against the costs of cleaning and maintenance and the potential for groundwater contamination via a perforated or breached liner. Also, evaporation cannot be relied on to reduce the total volume contained because it is periodically replenished by precipitation. Prohibiting any discharge from a pond will mean that the contents will need to be pumped and hauled to an amenable POTW every other year; a longer cycle will increase the probability that no POTW would accept the contents because of the increased brine concentration. Alternatively, the unevaporated content can be pumped to tanks, if available, and used as brine makeup solution or hauled to another facility for this purpose. [N]

Design and Operation of Washing Facilities

New Hampshire, Oregon, and other states have identified environmental stewardship practices for vehicle washing facilities. [N] [N]The following environmental stewardship practices can be added to existing and or new DOT facilities to minimize the potential for environmental contamination from polluted runoff:

  • Warning signs should be posted for customers and employees instructing them not to dump vehicle fluids, pesticides, solvents, fertilizers, organic chemicals, or toxic chemicals into catch basins. Catch basins are chambers or sumps which collect runoff and channel it to the stormwater drain or to the sanitary sewer. Vehicle wash facilities should stencil warnings on the pavement next to the grit trap or catch basin . All signs should be in a visible location and maintained for readability .
  • Care should be taken to minimize wash water run-off from cleaning operations.

    • Minimize water use to reduce potential for unpermitted non-stormwater discharges (e.g., provide a positive shutoff type of hose nozzle).
    • When possible, truck beds should be cleaned using a dry cleanup technique (sweep up or shovel out).
    • Use low pressure (brush and hose with nozzle only. no power booster or steam cleaning)
    • Exterior and frame wash only
  • No detergents should be used , as they emulsify oil in the oil/water separator and make the separator ineffective and may violate a DOT's NPDES/SPDES permit by introducing new chemicals. Using alternative cleaning agents such as phosphate-free, biodegradable detergents for vehicle washing can also reduce the amount of contaminants entering storm drains.
  • Where possible, indoor wash facilities with controlled floor drainage should be utilized. Where wastewater is not to be disposed to a sanitary sewer, grassed swales (shallow, vegetated ditches) or constructed wetlands (retention ponds with emergent aquatic vegetation) can be used to hold wastewater and allow contaminant removal through infiltration and filtration.
  • Washwater may otherwise be collected in a sump, grit trap, or containment structure to be pumped or siphoned to a vegetated area so that complete percolation into the ground occurs. A portable collection system will provide the collection of the contaminants provided the collection system is large enough to capture significant amounts of the overspray. Washwater runoff can also be disposed of into an infiltration basin/trench. The use of a bioswale with an oil/water separator will virtually eliminate the total suspended solids, oil and grease, and heavy metals discharged provided both are properly sized. [N]
    • Disposal of washwater should occur on ground surfaces with vegetated cover, preferably grasses, a minimum of 250 feet in length before a surface water body. A distance of 250 feet was based on a hydraulic conductivity of 0.2 gal/ft/day, volume per day of 150 gallons, and a swale with a width of 3 feet.
    • Complete percolation in the swale should occur with no direct discharge to the surface water. Discharge into a grassy swale for treatment should not occur within 24 hours after a rainfall event or if water remains ponded in the swale.
  • Wash areas should be located on well-constructed and maintained, impervious surfaces ( i.e., concrete or plastic ) with drains piped to the sanitary sewer or other disposal devices. The wash area should extend for at least four feet on all sides of the vehicle to trap all overspray. Enclosing wash areas with walls and properly grading wash areas prevent dirty overspray from leaving the wash area, allowing the overspray to be collected from the impermeable surface.
  • The impervious surfaces should be marked to indicate the boundaries of the washing area and the area draining to the designated collection point.
  • Washing areas should not be located near uncovered vehicle repair areas or chemical storage facilities ; chemicals could be transported in wash water runoff.
  • Regularly inspect and maintain the designated areas , facility wash racks, designated cleaning areas, wash pads, clarifiers, oil-water separators, sumps and sediment traps. Regularly clean wash areas, grit traps, or catch basins to minimize or prevent debris discharge, such as paint chips, dirt, cleaning agents, chemicals, and oil and grease into storm drains or injection wells.
  • A washwater treatment sequence may include such elements as a grit trap, an oil/water separator, a dosing tank with siphons or pumps, and a multi-media filter bed with underdrains.

    • Discharge from underdrains must meet effluent limitations.
    • Maintenance of a multi-media filter should consist of cleaning, removing the top inch of sand once every six months; when the total depth of filter sand fall below 18-inches, the sand should be replaced. If clogging and/or short circuiting occurs as observed by uneven infiltration in the filter or formation of surface cracks, the sand should be replaced.
    • A Spill Prevention, Control and Countermeasure (SPCC) Plan, in accordance with 40 CFR 112, should be prepared and implemented to prevent the entry of pollutant loads beyond the capabilities of the treatment system.
  • Contractual provisions should require contractors to use cleaning practices consistent with DOT requirements .

Recycling Wash Water

Recycling systems reduce or eliminate contaminated discharges to stormwater drains and injection wells by reusing the wash water until the water reaches a certain contaminant level. The wastewater is then discharged to a collection sump or to a treatment facility. Collection sumps are deep pits or reservoirs that hold liquid waste. Vehicle wash water accumulates in the collection sumps, and is pumped or siphoned to a vegetated area (such as a grassed swale or constructed wetland). Sediment traps can also be used to strain and collect the vehicle wash water, prior to pumping or siphoning the wash water to a vegetated area. The use of a recycling system can reduce or eliminate the contaminant discharge to stormwater or sanitary sewer while greatly reducing the amount of water used in the process. Some DOTs are installing brinemaking at truck washing facilities so washwater can be used as "make-up" solution. This solution can also be used to "spray the load" of salt/sand mix and/or to fill saddle tanks for spraying the mix as it passes through the salt spreader. The cost of brinemaking equipment is relatively affordable, though adding brine application equipment to existing trucks is more costly.

A recycled wash water has been successfully used by one of the largest bus transport companies operating in Borsod County , Hungary . In 1985, they installed a new, water-saving wastewater treatment facility for wastewaters resulting from washing at the central service plant. The commercial transportation system uses detergent-free, high pressure, hot water to remove dirt and grime from the car bodies and engines of the buses. The resulting wastewater is mechanically treated with filters consisting of sand and activated carbon. For disinfection, a 1 to 3 mg/l NaOCl solution is used. The filters are backwashed with recycled water every 3 to 4 days. The polluted backwash water is returned to the treatment plant. Oily rainwater from the yard is also directed into the treatment plant. The system uses fine sand filtration after pretreatment of the wastewater to remove grit, sand and oil. After this pretreatment, about 15 percent to 20 percent of the wastewater is discharged into a conventional sewerage system. This discharge prevents the accumulation of TDS and organic substances in the remaining water which is recycled for use in the carwash. This discharged water meets the water quality requirements for all categories. The remaining water that is to be recycled is subjected to ozonation to prevent anaerobic digestion of organic materials which produces foul odors. After ozonation, the remaining, pretreated water is conveyed through a fine sand filter by pump. Once filtered, the water is resupplied to the carwash by means of a rubber membrane hydrophore at a pressure of between 2 and 8 bar. For the commercial vehicle washing recycling facility, the initial investment costs are about $80,000, with a further investment of $1,600 for reconstruction after about ten years of operation. Maintenance costs were about $4,000/year. The estimated period for recovery of this investment is about 1.3 years based upon typical usage within the region. The technology achieved 80 percent recycling of water. [N]

In addition to the recycling of washwater, environmental stewardship practices associated with recycling washwater include: [N]

  • Recycling treatment equipment should be properly operated and maintained to achieve compliance with all conditions of the permit.
  • Backwash water or concentrate water should be properly discharged to sanitary sewer.
  • Liquid concentrate discharged to the sanitary sewer should meet all pretreatment standards and other requirements of the local Sewer Authority.
  • Solids, grit, or sludge should be disposed in a manner that complies with State administrative rules.


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Table of Contents
Chapter 6
Maintenance Facilities Management
6.1 Planning and Prioritizing Environmental Improvements at Maintenance Facilities
6.2 Facility Housekeeping Practices
6.3 Yard and Floor Drain Management
6.4 Energy Conservation
6.5 Under and Above-Ground Storage Tanks
Lists: Examples | Tables | Figures
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