Subsurface Drainage Practices in Pavement Design, Construction, and Maintenance (2022)

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76 A P P E N D I X A Agency Survey Questionnaire NCHRP SYNTHESIS PROJECT 20-05, TOPIC 52-10, “SUBSURFACE DRAINAGE PRACTICES IN PAVEMENT DESIGN, CONSTRUCTION, AND MAINTENANCE” SURVEY OF AGENCY PRACTICE Dear Agency Representative, The Transportation Research Board (TRB), through the National Cooperative Highway Research Program (NCHRP), under the sponsorship of the American Association of State Highway and Transportation Officials (AASHTO), and in cooperation with the Federal Highway Administration (FHWA), is preparing a synthesis report on subsurface drainage practices in pavement design, construction, and maintenance. The purpose of this survey, which we estimate should take no more than 30 minutes to complete, is to identify and summarize current practices for design, construction, and maintenance of subsurface drainage systems for new pavement construction and reconstruction, pavement preservation, and/or pavement rehabilitation. The results of the survey will be incorporated into a synthesis of highway agency practice, with the intent of helping agencies evaluate and improve their current subsurface drainage practices. This survey of practice is being sent to each state highway agency representative currently serving as a voting member on the AASHTO Committee on Materials & Pavements. The survey consists of four parts: A) Subsurface Drainage System Design, B) Subsurface Drainage System Construction, C) Subsurface Drainage System Performance, and D) Subsurface Drainage System Testing/Maintenance. If you feel that you are not the appropriate person at your agency to complete one or more of the parts of this survey, or if you wish to solicit additional expertise in your agency, you may freely forward this survey to the correct person(s) in your agency for partial/full completion. Please ensure that the entire survey is completed and returned on or before March 30, 2021. Instructions for submitting the completed survey are provided on the final page. If you have any questions, please contact the principal investigator: Kathleen T. Hall Thank you for your time and expertise in completing this important survey.

Agency Survey Questionnaire 77   Definitions The following definitions are used in conjunction with this survey of practice: • Subsurface Drainage – an integrated system used to intercept, collect, and discharge water that infiltrates into the pavement section • Pavement Section – any combination of surface, base/subbase above the natural or chemically treated subgrade, located within the right of way and intended to provide safe, efficient, long-term support to vehicular traffic • Drained Asphalt Pavement – any asphalt pavement section that includes a permeable base layer • Drained Concrete Pavement – any concrete pavement section that includes a permeable base layer • Surface Infiltration – water that enters vertically into the pavement section through longitudinal and transverse joints and cracks in and between the travel lanes and the curb/shoulder • Subsurface Infiltration – water that migrates into the pavement section through lateral groundwater seepage, fluctuations in groundwater levels, and/or through capillary action • Drainage Layer – a porous aggregate layer within the pavement section that provides a means to remove infiltrated water (may be unstabilized, asphalt-stabilized, or cement-stabilized, and may be referred to as a permeable layer, an open-graded layer, or a free-draining layer) • Underdrain – a conduit to remove water from a drainage layer • Edgedrain – an underdrain along the longitudinal edge of the pavement • Crossdrain – an underdrain running transversely under the traffic lanes • Filter Layer – a layer below the drainage layer designed to allow water to drain through freely but prevent soil/aggregate particles in the underlying layer (subbase or subgrade/embankment) from infiltrating into the drainage layer

78 Subsurface Drainage Practices in Pavement Design, Construction, and Maintenance Instructions for Completing Survey The survey must be completed in Adobe Acrobat, Adobe Reader, or other compatible pdf reader software and may be saved on local computers and completed in multiple sessions. The survey may also be forwarded to others within your agency for review and/or partial/full completion. This survey has been prepared in a multiple-choice format that allows one or more responses to be selected from each of 20 questions. For each question, multiple responses have been developed to provide answers with the appropriate depth and breadth of coverage while minimizing the time required to complete the survey. If you feel that the provided responses do not adequately address your agency’s practice, separate fill-in spaces are provided at the bottom of each question to allow for the entry of alternate responses and/or additional information or clarifications to selected responses, as desired. This fillable pdf survey form allows for the simple checking of one or more responses, as appropriate, for each question. Questions are provided in a one-page-per-question format and navigation buttons for “Previous Question”, “Save File”, and “Next Question” are provided at the bottom of each page. Standard Adobe Acrobat navigation tools may also be utilized. A “Save File & Submit Survey” button is provided on the last page. You will be prompted to save the completed survey and to select your desired email server, after which a stock email script will be generated with the completed survey automatically attached.

Agency Survey Questionnaire 79   Part A – Questions Related to Subsurface Drainage Design 1. This survey of practice has been developed to obtain information related to the use of subsurface drainage systems. Please include the following respondent information: Name: DOT Agency: Phone: Email: If your agency currently uses subsurface drainage systems, please continue to the next question. If subsurface drainage systems are not currently used, please carefully review the following choices and select ALL that apply to your agency practices: Subsurface drainage systems have never been used by our agency. Subsurface drainage system usage discontinued due to poor performance. Subsurface drainage system usage discontinued due to construction issues. Subsurface drainage system usage discontinued due to maintenance issues. Subsurface drainage system usage discontinued due to cost issues. Other (please specify): Additional Comments/Clarifications (Optional) If subsurface drainage systems are not currently used, you may continue to answer questions related to previous subsurface drainage practices, if any, or you may skip ahead to the end of the survey to submit your response.

80 Subsurface Drainage Practices in Pavement Design, Construction, and Maintenance 2. As illustrated in these figures, subsurface drainage systems of various types may be installed during pavement (re)construction to remove water that infiltrates into the pavement section. Please carefully review the following choices and select ALL that apply to your agency practices: Subsurface drainage components are installed: o During ALL new concrete pavement construction. o During ALL new asphalt pavement construction. o Only when their usage meets established criteria. o In all sag locations. o In all cut/fill transitions. o Only where existing pavement is adjacent to full-depth roadway widening that contains an existing subsurface drainage system. o A decision to incorporate subsurface drainage is pending based on current research. o Other (please specify) o Additional Comments/Clarifications (Optional) ShoulderPavement HMA or PCC Outlet Subbase Open-graded base Collector pipe No Groundwater With Groundwater and/or Frost Protection ShoulderPavement HMA or PCC Outlet Subbase Open-graded base Collector pipe

Agency Survey Questionnaire 81   3. The need for subsurface drainage in pavement repair/(re)construction projects may be assessed based on numerous pavement design considerations. Please carefully review the following choices and select ALL that apply to your agency practices: Subsurface drainage needs are assessed by evaluating: Overall surface drainage pa rns. Climatic in uences. Highway geometrics. Groundwater levels. Soil types. Proposed base materials. Historical roadway distresses. The structural capacity of the existing pavement section. Potenti l impacts on adjacent wetlands. Other (please specify) Additional Comments/Clarifications (Optional)

82 Subsurface Drainage Practices in Pavement Design, Construction, and Maintenance 4. Subsurface drainage system components may be designed based on site-specific conditions or may be standardized to apply to more generalized regional/soil conditions. Please carefully review the following choices and select ALL that apply to your agency practices: o Subsurface drainage system components are designed using the Drainage Requirements in Pavements (DRIP, DRIP2) software. o Subsurface drainage system components are designed using in-house software. o Subsurface drainage system components are selected using standardized designs. o Other (please specify) o Additional Comments/Clarifications (Optional)

Agency Survey Questionnaire 83   5. Water from a variety of sources may be intercepted by subsurface drainage systems. Please carefully review the following choices and select ALL that apply to your agency practices: Subsurface drainage is used to intercept: rainwater entering vertically through joints and cracks. snow meltwater entering vertically through joints and cracks. vapor movements that increase moisture levels in base/subbase/subgrade layers. groundwater entering horizontally. groundwater rising vertically through capillary action. groundwater rising vertically due to seasonal and/or long-term uctuations. Other (please specify) Additional Comments/Clarifications (Optional) Water table Capillarity Seepage Lateral moisture transfer Seepage ReservoirLandscape irrigati n Precipitati n Infiltrati n

84 Subsurface Drainage Practices in Pavement Design, Construction, and Maintenance 6. The choice to incorporate subsurface drainage in pavement repair/(re)construction projects may be based on economic and non-economic factors. Please carefully review the following choices and select ALL that apply to your agency practices: Subsurface drainage is incorporated when in-house decision criteria are satisfied. The decision to incorporate subsurface drainage is based on: The results of a life-cycle cost analysis. Pavement type. Proposed base materials. Historical pavement distresses. Continuous maintenance issues where trapped water in the pavement structure is known to have contributed to a structural pavement failure. Projected traffic levels. Subgrade properties. Precipitation rates (e.g., 1-hr-duration / 1-yr-frequency). Other (please specify) Additional Comments/Clarifications (Optional)

Agency Survey Questionnaire 85   7. As indicated in the figure, the minimum thickness of the permeable base must be sufficient to provide for the maximum depth of flow (Hm) within the permeable base, which is influenced by the coefficient of permeability, k d, in the direction of flow, and can occur during prolonged rainfall events or continuous flows from groundwater movements. Please carefully review the following choices and select ALL that apply to your agency practices: Permeable base layers are not used by our agency. Permeable base thickness requirements are established based on infiltration computations. Permeable base thickness is standardized at 100 mm. Permeable base thickness is standardized at 150 mm. The permeable base is designed as a structural component of the pavement system, and its thickness is determined based on agency design standards. Other (please specify) Additional comments/clarifications (optional) L S 1 q = Design inflow raten k = Coefficient of permeabilityd Outlet Hm

86 Subsurface Drainage Practices in Pavement Design, Construction, and Maintenance 8. Where permeable base layers are utilized, the aggregate gradation (e.g., AASHTO #8, #57, #67) and/or layer stabilization (e.g., cement, asphalt) may be selected based on considerations that apply during construction and/or during the service life of the pavement. Please carefully review the following choices and select ALL that apply to your agency practices: Permeable base layers are not used by our agency. Permeable base layers are currently constructed using: Unstabilized aggregates. Cement-stabilized aggregates. Asphalt-stabilized aggregates. Permeable base layers were previously constructed using unstabilized aggregates; cement stabilization is currently allowed/required. Permeable base layers were previously constructed using unstabilized aggregates; asphalt stabilization is currently allowed/required. Permeable base layers were previously constructed using a highly permeable aggregate gradation; a denser gradation with reduced permeability is currently specified. Permeable base layers are only permitted within the roadway shoulders. Other (please specify) Additional comments/clarifications (optional)

Agency Survey Questionnaire 87   9. The maximum aggregate size and gradation of the permeable layer is directly related to its permeability (i.e., hydraulic conductivity), with uniformly sized gravel gradations providing high levels of hydraulic conductivity and uniformly sized sands and dense gradations providing lower levels of hydraulic conductivity. Please carefully review the following choices and select ALL that apply to your agency practices: Permeable base layers are not used by our agency. Permeable base layers are currently constructed using a moderately permeable aggregate gradation (e.g., < 1,000 ft/day). Permeable base layers are currently constructed using a highly permeable aggregate gradation (e.g., > 1,000 ft/day). Permeable base layers were previously constructed using a highly permeable aggregate gradation; a denser gradation with a moderate to low permeability is currently specified. Permeable base layers are currently utilized, and: No specifications for in-place hydraulic conductivity are utilized. In-place hydraulic conductivity > 100 ft/day is specified. In-place hydraulic conductivity > 500 ft/day is specified. In-place hydraulic conductivity > 1,000 ft/day is specified. The required in-place hydraulic conductivity is determined based on the time to 50% drainage. The required in-place hydraulic conductivity is determined based on the time to 85% drainage. Other (please specify): Additional comments/clarifications (optional)

88 Subsurface Drainage Practices in Pavement Design, Construction, and Maintenance 10. As shown in these figures, various methods may be utilized to transmit water collected by the permeable base layer to side ditches and away from the pavement section. Please carefully review the following choices and select ALL that apply to your agency practices: Permeable base layers are not used by our agency. Permeable base layer with underlying geotextile or wicking geotextile daylighted to the side slope. Longitudinal edge drains with porous aggregate backfill and slotted pipe conduits. Longitudinal edge drains with porous aggregate backfill and preformed geocomposite edge drain (PGED) conduits. Longitudinal preformed geocomposite edge drain (PGED) conduits used with no porous aggregate backfill. Transverse outlets with concrete headwalls spaced at intervals up to 250 ft. Transverse outlets with concrete headwalls spaced at intervals greater than 250 ft. Transverse outlets with unprotected pipe ends spaced at intervals up to 250 ft. Transverse outlets with unprotected pipe ends spaced at intervals greater than 250 ft. Other (please specify) Additional comments/clarifications (optional) Permeable Base with Longitudinal Trench Drain Permeable Base Daylighted to Side Slope Pavement surfaceShoulder Transverse outlet pipe Longitudinal edge drain w/pipe or PGED Permeable base Separator (Filter) aggregate or geotextile Pavement surface Daylighted edge Permeable base Separator (Filter) aggregate or geotextile

Agency Survey Questionnaire 89   Part B – Questions Related to Subsurface Drainage System Construction 11. Permeable base layers with high hydraulic conductivity have been reported to have poor stability under construction/vehicular traffic. To combat this detrimental effect, some agencies have modified the properties of the permeable layer and/or allowed/required the use of stabilizers. Please carefully review the following choices and select ALL that apply to your agency practices: Permeable base layers are not used by our agency. No modifications to our standard specifications for permeable base layers have been made in the past 5 years. A denser gradation with reduced permeability is now utilized to enhance stability under traffic loads. A higher fractured face count is now utilized to enhance stability under traffic loads. A minimum resilient modulus is now required to enhance stability under traffic loads. Asphalt stabilization of the permeable layer is now required to enhance stability under traffic loads. Cement stabilization of the permeable layer is now required to enhance stability under traffic loads. Asphalt stabilization of the permeable layer is now allowed at the contractor’s discretion to enhance stability under traffic loads. Concrete stabilization of the permeable layer is now allowed at the contractor’s discretion to enhance stability under traffic loads. Other (please specify) Additional comments/clarifications (optional)

90 Subsurface Drainage Practices in Pavement Design, Construction, and Maintenance 12. To provide for effective drainage, permeable base layers should be protected from contamination during construction. Please carefully review the following choices and select ALL that apply to your agency practices: Permeable base layers are not used by our agency. No specific requirements for permeable base protection are enforced during construction. Construction and/or local traffic on unprotected permeable base layers is restricted prior to final surfacing. Construction and/or local traffic on unprotected permeable base layers is prohibited prior to final surfacing. Other (please specify) Additional comments/clarifications (optional)

Agency Survey Questionnaire 91   13. Aggregate and geotextile filters have been utilized to prevent clogging of permeable base layers during service. Please carefully review the following choices and select ALL that apply to your agency practices: Filter l yers are not used by our agency. A standard gradation for aggregate filter layers is utilized. Aggregate filter l yer particle size and gradation are determined based on an lysis of the particle size/gradation of the permeable layer and underlying layer (subbase or subgrade/embankment soil). A standard geotextile filter fabric is utilized. Piping resistance of geotextile filter fabrics is selected based on analysis of soil gradation. Clogging resistance of geotextile filter fabrics is selected based on an lysis of soil gradation. Other (please specify) Addition l comments/cl rifications (optional) Permeable base with separator layer Separator layer Surface layer Subgrade Permeable base without separator layer Permeable base Surface layer Permeable base with subgrade contamination

92 Subsurface Drainage Practices in Pavement Design, Construction, and Maintenance 14. Longitudinal edge drains may be installed to drain water away from a permeable base layer and/or to lower the level of the water table below the pavement structure. As shown in the example figures, these edge drains may be installed during pavement (re)construction or retrofitted to existing pavements. Please carefully review the following choices and select ALL that apply to your agency practices: Longitudinal edge drains are not used by our agency. Longitudinal edge drains are installed during new construction/reconstruction, prior to final surfacing of the driving lanes. Longitudinal edge drains are installed during new construction/reconstruction, after final surfacing of the driving lanes. Longitudinal edge drains may be retrofitted into existing pavements. Longitudinal edge drains were previously used but have been discontinued due to maintenance issues. Other (please specify) Additional comments/clarifications (optional) PCC PCC shoulder Embankment Separator layer Permeable base Drainage pipe Geotextile Drainage pipe Geotextile PCC PCC shoulder Embankment Separator layer Permeable base AC pavement AC shoulder Subbase/Subgrade Aggregate base Geocomposite drainSand backfill Pre-pave Installation Post-pave Installation Retrofit Installation

Agency Survey Questionnaire 93   Part C – Questions Related to Subsurface Drainage System Performance 15. Performance studies have been conducted to establish parameters useful for determining the expected service life and/or cost-effectiveness of subsurface drainage systems. Please carefully review the following choices and select ALL that apply to your agency practices: Performance studies of drained pavements have not been conducted by our agency. Performance studies of drained pavements have been conducted by our agency, and: Published reports are available. Published reports are not yet available. Have been utilized to establish service life expectancies for drained pavement systems. Have been utilized to establish design costs for drained pavement systems. Have been utilized to establish construction costs for drained pavement systems. Have been utilized to establish maintenance costs for drained pavement systems. Other (please specify) Additional comments/clarifications (optional)

94 Subsurface Drainage Practices in Pavement Design, Construction, and Maintenance 16. The expected service lives of drained pavement sections, compared to undrained pavement sections, have been established by various agencies and are used within the context of life-cycle cost analysis. Please carefully review the following choices and select ALL that apply to your agency practices: Compared to undrained asphalt pavement sections, drained asphalt pavement sections: Are not expected to have a longer service life prior to first rehab. Are expected to have a 1-10% longer service life prior to first rehab. Are expected to have an 11-20% longer service life prior to first rehab. Are expected to have a 21-30% longer service life prior to first rehab. Are expected to have a >30% longer service life prior to first rehab. Compared to undrained concrete pavement sections, drained concrete pavement sections: Are not expected to have a longer service life prior to first rehab. Are expected to have a 1%–10% longer service life prior to first rehab. Are expected to have an 11%–20% longer service life prior to first rehab. Are expected to have a 21%–30% longer service life prior to first rehab. Are expected to have a >30% longer service life prior to first rehab. Other (please specify) Additional comments/clarifications (optional)

Agency Survey Questionnaire 95   Part D – Questions Related to Subsurface Drainage System Testing/Maintenance 17. Various in-place tests/inspections, conducted by staff, contractors and/or external vendors have been utilized to monitor the functionality of subsurface drainage components. Please carefully review the following choices and select ALL that apply to your agency practices: Subsurface drainage system inspections are not conducted by our agency nor by contractors/external vendors. Visual inspections of outlets/headwalls are conducted: On an annual basis. At 2- to 3-year intervals. At 4- to 5-year intervals. At intervals of more than 5 years. Probing of drainage pipes/conduits to confirm that no blocking exists is conducted: On an annual basis. At 2- to 3-year intervals. At 4- to 5-year intervals. At intervals of more than 5 years. Camera inspections of drainage pipes/conduits to confirm that no blocking or collapses exist are conducted: On an annual basis. At 2- to 3-year intervals. At 4- to 5-year intervals. At intervals of more than 5 years. Water flow testing to confirm water flows from pavement surface to transverse outlets is conducted: On an annual basis. At 2- to 3-year intervals. At 4- to 5-year intervals. At intervals of more than 5 years. Other (please specify) Additional comments/clarifications (optional)

96 Subsurface Drainage Practices in Pavement Design, Construction, and Maintenance 18. Proper location and maintenance of transverse outlets may be considered necessary for the long-term functionality of subsurface drainage systems. Please carefully review the following choices and select ALL that apply to your agency practices: Transverse outlets are not used by our agency. Transverse outlets/headwalls are used, but no specific location markers are utilized. Transverse outlet/headwall locations are identified by paint marks applied on the pavement edge/shoulder. Transverse outlet/headwall locations are identified by delineator posts adjacent to the outlets. Other (please specify) Additional comments/clarifications (optional)

Agency Survey Questionnaire 97   19. These photos illustrate common problems observed with subsurface drainage components. Please carefully review the following choices and select ALL that have been documented by your agency: Transverse outlet pipes collapsed. Longitudinal drainage pipes collapsed. Transverse outlets/headwalls buried. Transverse outlets/headwalls damaged or missing. Transverse outlets/headwalls missing rodent screens. Other (please specify) Additional comments/clarifications (optional) Crushed outlet pipe Buried outlet pipe Buried outlet headwallMissing rodent screen

98 Subsurface Drainage Practices in Pavement Design, Construction, and Maintenance 20. Various survey methods have been used to evaluate the influence of subsurface drainage on the functional and structural capacity of the pavement system. Please carefully review the following choices and select ALL that apply to your agency practices: o No evaluation of the influence of subsurface drainage on the functional and structural capacity of the pavement system has been conducted. o Visual pavement distress surveys are utilized to identify moisture-related distress in pavements with subsurface drainage. o Visual surveys of water flow are utilized to assess functionality of subsurface drainage systems. o Falling weight deflectometer testing is conducted to assess the structural capacity of existing pavements with subsurface drainage. o Impact echo testing is conducted to assess the structural capacity of existing pavements with subsurface drainage. o Falling weight deflectometer testing is conducted to assess the uniformity of support provided by permeable base layers. o Impact echo testing is conducted to assess the uniformity of support provided by permeable base layers. o Ground-penetrating radar is used to assess the uniformity of support provided by permeable base layers. o Other (please specify) o Additional comments/clarifications (optional)

Agency Survey Questionnaire 99   Agency Policy Documents Please provide links to as many documents and sources of information as necessary to accurately convey your agency’s subsurface drainage design practices. These may include contract documents, agency reports, agency manuals (guidelines), policies, research reports, etc. If desired, you may also submit files as email attachments. Please provide contact information for the person primarily responsible for completing this survey: Name: Organization: Phone Number: E-mail Address: Follow-Up Case Examples The synthesis will include case examples illustrating subsurface drainage practices from selected agencies. During the development of case examples, phone/Zoom interviews will be conducted. Selected agencies will be provided the opportunity to review their case example write-ups for accuracy. Would your agency be interested in participating in a case example? Yes No Please provide contact information for the person responsible for discussing the case example: Name: Organization: Phone Number: E-mail Address: Survey Completion and Submission Thank you for completing this survey of practice for subsurface drainage system design, construction, and maintenance. You may submit your completed survey using the “Save File & Submit Survey” button below, which will prompt you to save the completed survey and then to select your desired email server. A stock email script will be generated with the completed survey automatically attached. Please check your Drafts folder to be sure the email was sent. You will receive a confirmation email once your completed survey is received. As an alternative, you may simply save the completed survey on your local computer and send it as an email attachment to the researchers at NCHRP52-10@charter.net.

100 Subsurface Drainage Practices in Pavement Design, Construction, and Maintenance Follow-Up Interviews Upon review of the agency survey responses as well as the literature reviews, the contractor will conduct phone/Zoom interviews with selected agencies that indicated the current/past usage of subsurface drainage systems and a willingness to participate in the case examples. Follow-up questions/topics will be sent by email for review prior to the phone/Zoom interview to the contact person identified in the agency survey. Contacts will be asked to indicate preferred date(s) and time(s) for conducting the phone/Zoom interview. Dear Agency Representative, Thank you for your willingness to participate in the case studies of subsurface drainage practices. We would like to conduct a phone or Zoom interview, which we estimate should take no more than 30 minutes to complete, to learn more about your current practices for design, construction, and maintenance of subsurface drainage systems. Your information will be incorporated into a synthesis of highway agency practice, with the intent of helping other agencies to evaluate and improve their current subsurface drainage practices. The following represent the follow-up questions/topics that we will cover during our interview: 1. Describe your selection process for projects to include subsurface drainage systems. 2. What are the cost impacts (e.g., percent increase/decrease in pavement costs) of pavements with subsurface drainage systems? 3. How much is pavement performance improved (e.g., life extension) by the use of subsurface drainage systems? 4. Identify challenges your agency has faced in incorporating subsurface drainage systems into pavements. 5. How is subsurface drainage evaluated at the network level? 6. Are other strategies used to minimize water from being trapped in the pavement structure? 7. What type(s) of subsurface drainage system have worked well for your agency? 8. Have you modified your practices to improve performance of subsurface drainage systems? Please indicate your preferred style, date(s), and time(s) for this interview: Zoom Interview Phone Interview 1st Preference of Date & Time 2nd Preference of Date & Time 3rd Preference of Date & Time 4th Preference of Date & Time