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Design Information Bulletin Number 84 (DIB 84) - Guidance for the Removal and Disposal of Concrete Pavement Grooving and Grinding Residues.
This document provides information and guidance to the Project Engineer and the Project Development Team (PDT) regarding the removal and disposal of residues from grooving or grinding operations on portland cement concrete (PCC) pavement (otherwise known as rigid pavement). The goal of this document is to provide background information to designers and specification writers during the PS&E process when considering the removal and disposal of these residues. This bulletin is intended to assist the PDT to develop cost-effective contracts and to comply with local water quality requirements.
This document is not a textbook or a substitute for engineering knowledge, experience or judgment. Many of the instructions given herein are subject to amendment as conditions and experience may warrant. Special situations may call for variations from the procedures described.
Guidance for the Removal and Disposal of Concrete Pavement Grooving and Grinding Residues
This document provides information and guidance to the Project Engineer and the Project Development Team (PDT) regarding the removal and disposal of residues from portland cement concrete (PCC) pavement grooving or grinding operations. PCC pavement is also referred to as rigid pavement or concrete pavement in the Highway Design Manual and other support guidance. PCC pavement is divided into two types: Jointed Plain Concrete Pavement and Continuously Reinforced Concrete Pavement. Further discussion on these types can be found in Topic 621 of the Highway Design Manual. The goal of this document is to assist the PDT during the PS&E process to develop cost-effective contracts and to comply with water quality requirements; these requirements are incorporated into an SSP that should be used with these projects, SSP 42-600, “Disposal of Portland Cement Concrete (PCC) Pavement Grooving and Grinding Residues.”
Due to the potentially large volumes of residues that can be generated during PCC pavement grooving and grinding operations, the PDT early in the design process should assess the feasibility of allowing temporary storage and treatment of residues within the State right-of-way, and the optimum method for disposal of these residues; this assessment should include a thorough cost analysis, including both short and long-term costs.
A team consisting of Project Delivery functions, with the Division of Design as lead, prepared these guidelines. These guidelines do not constitute a standard, and the issuance of these guidelines does not eliminate the need for sound engineering judgment. Special situations may call for methods, procedures, or techniques not discussed in this guidance and for editing of the SSP, for which approval must be obtained from the Project Manager of the Pavement Standards Program. (See the nSSP Process Guidance for pavements at http://www.dot.ca.gov/hq/oppd/pavement/nssps.htm for procedures.) General guidance on pavement design may be found in the Highway Design Manual Chapters 600 to 670 and pavement rehabilitation strategies are discussed in Pavement Tech Notes: Interim PCC Pavement Rehabilitation Guidelines. Specific guidance on these topics is otherwise beyond the scope of this document.
If you have any questions, please contact your Project Manager or Design Coordinator.
Many of the design issues that are presented below result from regulatory issues that affect the disposal of PCC pavement grooving and grinding residues, as such, the regulatory issues are discussed first.
The California State Water Resources Regional Water Quality Control Board (SWRCB) has regulatory authority related to protection of water quality from waste discharges, and this is administered for an individual project through the applicable Regional Water Quality Control Board (RWQCB). The Department has conducted characterization studies of residues from pavement grooving and grinding operations that indicate PCC pavement grooving and grinding wastes are non-hazardous, but contain constituents that may have the potential to impact water quality and therefore are subject to regulation by the applicable RWQCB.
When temporary storage or permanent disposal within the State right-of-way is considered, the Project Engineer should seek assistance from District/Region NPDES Coordinator or District Environmental who will coordinate with the local RWQCB for approval (permit, waiver, or letter of instruction). Adequate lead-time is necessary to allow the local RWQCB to consider the application, as the RWQCB has up to 30 days to respond initially to an application, but up to 180 days for final resolution. Temporary storage or disposal of the residues may be subject to conditions imposed by the RWQCB, and such conditions would have to be clearly indicated in the contract documents and implemented during the work. Another potential condition is a requirement for monitoring of the residues if disposed with the State right-of-way; such monitoring can significantly increase the construction and long-term costs of the project. Permits obtained for the temporary storage, disposal, or reuse of PCC pavement grooving and grinding residues does not exempt the project from adherence to the Department’s statewide storm water permit requirements. General guidance on this and other construction site BMPs are found in Reference 6.
PCC pavement grinding is an operation used to preserve pavement ride quality/friction, rehabilitate pavements, or facilitate construction widening by removing or reducing undulations in the pavement from curling within a slab or step offs between slabs (a.k.a. faulting).
PCC pavement grooving is used to increase friction by imparting grooves that act to improve the performance of tires when the pavement is wet. Grooving may also be performed on new pavements to increase the coefficient of friction, and grinding and grooving are being investigated as potential methods for reducing tire/pavement noise. Further discussion on PCC grinding and grooving can be found in the Pavement Tech Notes: Interim PCC Pavement Rehabilitation Guidelines and HDM Topic 635, and on the “Quieter Pavements” website.
Grooving or grinding operations can be performed as an item of work during a construction contract (and SSP 42-600, “Disposal of Portland Cement Concrete (PCC) Pavement Grooving and Grinding Residues,” should be used in the contract special provisions) or can be performed as a mitigation measure by the Contractor (non-pay work item) if friction and roughness (‘high points’) requirements do not meet Standard Specifications 40-1.10, “Final Finishing.”
Large motorized equipment is used for both grooving and grinding operations, employing multiple diamond-studded blades operating on a single shaft, to impart a groove of varying depth (typically between ¼ inch to ½ inch [6 mm and 13 mm]). The equipment uses water applied to the pavement both as a cooling agent for the cutting blades, and to capture the dust generated for later collection by vacuum equipment (usually using a separate piece of equipment). This combination of grindings is known as grinding (or grooving) residue and must be disposed of in a safe and environmentally friendly manner. This section discusses measures that should be taken to address the disposal of these residues.
As a rough guide, the volume of residues generated is four to six times the volume of the pavement material to be removed during grooving and grinding operations. Volumes of residues (mixed solids and liquid) between 1,400 to 2,100 ft3 (40 and 60 m3) per work shift would not be uncommon, assuming no recycling of water. As can be noted using these rates, PCC pavement grooving and grinding contracts have the potential to generate large quantities of wastes, however, the quantities may vary depending upon: the condition of the pavement; the Contractor’s operations, methods and equipment; the allowed hours of work; the number of lanes that may be worked at one time; and the aggregate hardness. Due to these variables, District Construction should be consulted for likely production rates.
The preferred permanent disposal location of the residues is outside of the State right-of-way. However, to minimize project costs, the Project Engineer may consider permanently incorporating these residues within the project (e.g., into an embankment) or within the right of way. To do so, the Department must obtain prior approval (permit or waiver) from the applicable RWQCB. When disposal within the State right-of-way is considered, the Project Engineer should seek assistance from District Environmental or the District/Region NPDES Coordinator for obtaining RWQCB approval (permit, waiver, or letter of instruction). Reuse of solid and liquid components of the residues may be subject to conditions imposed by the RWQCB, such as depth of cover over the residues, type of cover material (e.g., using a pavement structural section), and vertical separation of residues from groundwater; such conditions would have to be clearly indicated in the contract documents and implemented during the work. Another potential condition is a requirement for monitoring of the residues, which might significantly increase the short and long-term costs of the project. Adequate lead-time is necessary to allow the local RWQCB to consider the application, as the RWQCB has up to 30 days to respond initially, but up to 180 days for final resolution. Items required along with the application may include, but are not limited to, application fee, project description, location of the temporary storage or disposal site, section drawing of the site, characterization of the waste stream, and quantity of wastes. RWQCBs typically consider such environmental factors as depth to ground water, soil cover, and protection from surface waters as well as the characteristic of the waste, and it is advisable that this information be developed for the project.
Residues have high initial moisture content and will typically be reduced by evaporation or dewatering prior to disposal of the solid residues. Evaporation can occur in temporary storage facilities but evaporation is more effective when the impoundment is constructed as shallow as possible. The evaporation process also proceeds faster in dry, arid conditions than cool and humid conditions. One or more impoundments may be placed to optimize evaporation; if placed as a series, the first in the series being used primarily for the initial placement and settling of the heavier solids, then the clearer liquid is decanted to succeeding impoundments. The liquid may be reused several times prior to disposal as long as it is relatively free from the solids generated by the work. Water remaining at the end of the project can be decanted when sufficiently free of sediments, and given disposal at a waste (non-sewage) treatment/reprocessing facility and some Class II landfills, although in some instances arrangements can be made with a sewer treatment plant for handling and treatment. Information concerning the ‘pan evaporation rates’ for the project area may be obtained from several sources (e.g., Reference 9) to estimate the evaporation that may occur.
Numerous other techniques besides impoundments (temporary ponds) are also available to separate the liquids from the solid material, and these techniques are usually more efficient than impoundments at separating the liquids from the solids (for example, using centrifuges, filters, or chemical precipitation). However, these other techniques are not yet commonly used for PCC pavement grinding or grooving projects. An advantage to these techniques is that they often require a smaller physical space than a large impoundment, usually between ½ and 1 acre (0.20 and 0.40 ha) and can treat a large amount of waste in a shorter period of time than evaporation. One separation technique applicable to these residues employs in series a dewatering tank, sand media particulate filter, pressurized bag filter, and/or cartridge filter. Several separation techniques are discussed further in the Department’s Construction Site Best Management Practices (BMP) Manual under “NS-2, Dewatering Operations” and the Department’s Field Guide to Construction Site Dewatering.
Air-dried residues may have some degree of surface drying and hardness within a short period of time once the free water is removed, while still retaining considerable moisture below the surface. For the residues to be accepted as a non-liquid waste at a Class III landfill there must be no free water present during spreading or compaction, and actions such as disking of the residues may be needed to sufficiently remove the remaining moisture.
If residues are not handled using the separation techniques mentioned above, ponds are usually used as the temporary storage facilities to allow settlement of solids to occur. The water separated from the solids may be reused to minimize the total volume of waste (solids and liquid) for disposal. By allowing temporary storage of the residues within the State right-of-way, project costs will be reduced because the Contractor would not need to rent and obtain regulatory approval for land outside of the State right-of-way. Use of State right-of-way for temporary storage must be in accordance with the Highway Design Manual Topic 111, “Materials Sites and Disposal Sites,” and Topic 112, “Contractor’s Yard and Plant Sites.” It is also in accordance with Public Resources Code Section 42920, wherein the Department is required to recycle and reduce the amount of waste sent to landfills.
The entirety of the residues from the project should be estimated when considering the size of the temporary storage facility, and more than one impoundment may be needed for the project. When considering locating temporary storage facilities within the project limits, other issues that should always be considered are traffic safety, and local environmental agency requirements.
Smaller temporary storage facilities should follow the requirements of SSP 07-405, “Temporary Concrete Washout Facility,” and its associated Standard Detail sheet, “Water Pollution Control Sheet: Temporary Water Pollution Control Details (Temporary Concrete Washout Facility)” as listed in the References section of this document (1). Several temporary facilities could be placed, if siting allowed, and each would contain about 360 ft3 to 880 ft3 (10 to 25 m3) of wastes, however, PCC pavement grooving or grinding operations can generate these quantities very quickly. Ideally, the entire estimated volume of residues from the project would be contained within the area allowed for the temporary storage facility. Allowance within the project limits or right of way of temporary storage does not imply nor obligate the Department to provide as much area as might be required.
Smaller PCC pavement grooving and grinding projects should consider listing the Temporary Concrete Washout Facility as an item of work, rather than as part of the Lump Sum payment made for Water Pollution Control (SSP 07-340 or 07-345), which should result in better bidding and more efficient contract administration.
Where a sufficiently large area within the State right-of-way is available for use as a temporary storage facility, the Project Engineer should consider including in the contract package a design for a larger temporary storage facility to be paid as an item of work, while recalling that all impoundments may be subject to requirements imposed by a RWQCB, including liner requirements more typically used at a liquid containment facility. Preliminary design guidance for these large impoundments is provided below. If design assistance if required it should be requested and coordinated through the HQ Design Office of Storm Water Management and DES Geotechnical Services. The plans and specifications for the larger temporary facility would be based upon SSP 07-405, “Temporary Concrete Washout Facility,” with consideration typically given to these additional items:
The Project Engineer should consider the cost and effects of contract time for the removal of the dried PCC residues and liner to an approved disposal facility at the end of the contract (assuming disposal outside of the State right-of-way is required).
(1) It may be preferable to rename the contract special provisions and the contract detail sheet showing the facility as “Temporary PCC Grinding [Grooving] Residue Facility”.
The disturbed soil area (DSA) for the PCC pavement grooving or grinding projects would not include the paved areas that will receive the work, as the underlying soils will not be exposed and the residues are required to be picked up concurrent with the work. However, areas allowed for temporary storage and any other areas exposing soils as a result of construction activities within the construction limits (e.g. often construction entrances/exits) should be included in the calculation of the DSA. Once the DSA is determined the appropriate “Water Pollution Control” standard special provision would be selected for the project based on DSA: SSP 07-340 for DSAs up to 1.0 acre [0.4 ha] (which requires a WPCP) or SSP 07-345 for greater DSAs (which requires a SWPPP). As the RWQCB may require a SWPPP in some situations even if the project does not meet the DSA threshold, the Project Engineer should consult with the District/Region NPDES Coordinator.
Under Standard Specification 15-3.02, "Removal Methods," hardened concrete may be buried into adjacent embankments if certain construction and regulatory requirements are met. This practice is not affected by the new SSP 42-600, “Disposal of Portland Cement Concrete (PCC) Pavement Grooving and Grinding Residues.” However, commingling of washout from transit mix trucks carrying concrete (i.e., concrete used for pavement slabs or structures) and PCC grooving and grinding residues will not result in a hardened material that would qualify under this Standard Specification. Commingling of these wastes may be allowed at the option of the Contractor, with the understanding that all residues/wastes must be removed while meeting the requirements of SSP 42-600, “Disposal of Portland Cement Concrete (PCC) Pavement Grooving and Grinding Residues.” As the Construction Site Best Management Practices (BMPs) Manual indicates that washout from transit-mix trucks and residues from grooving and grinding operations can be directed to “WM-8, Concrete Waste Management,” no changes are needed to the contract special provisions or detail sheets (if included in the contract plans).
Yellow paint stripes and thermoplastic markings may be present within areas proposed for grooving or grinding operations. Some of these markings in prior years consisted in part of chromium or other constituents which are classified as a hazardous waste in high concentrations. Removal of yellow paint strips and thermoplastic stripping are addressed in the Instruction Notes to SSP 15-300, “Remove Traffic Stripe and Pavement Marking,” and this SSP should be included as needed in the contract special provisions.
The Basic Engineering Estimating System (BEES) estimate for the unit cost of PCC pavement grooving or grinding can be obtained from the Contract Cost Data Book. However, while the construction industry is adapting to the new disposal requirements in SSP 42-600, “Disposal of Portland Cement Concrete (PCC) Pavement Grooving and Grinding Residues,” an additional 20% should be added to the unit cost for either item of work to account for disposal, pending the reflection in the Contract Cost Data Book of contracts fully employing the new requirements.
Costs for the smaller temporary storage facilities should be based upon information obtained in the latest Contract Cost Data Book, if listed as an item of work. Costs for larger temporary storage facilities, when listed as an item of work, should be based upon the latest Contract Cost Data Book and should include all associated costs such as Roadway Excavation.
The type of contract employed for large PCC pavement grooving or grinding projects can affect the project in various ways, such as:
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