October 1, 2018 Mr. Eric J. DeDominicis, P.E. Deputy Practice Leader, Aviation Urban Engineers, Inc. 1 South Street, Suite 1275 Baltimore, MD 21202 Ref: RDM Job No. 1751: Runway and Taxiway Rehabilitation at College Park Airport, College Park, Maryland. Dear Mr. DeDominicis: RDM International Inc. (RDM) was retained by Urban Engineers, Inc. (Urban) to perform functional evaluations for the Runway 15-33, parallel taxiway, and associated connectors at College Park Airport (CGS) College Park, MD. The primary objective of the project is to evaluate the functional condition and assist Urban with developing design alternatives for pavement rehabilitation. Runway 15-33 is 2,607 feet long by 60 feet wide and is asphalt concrete (AC) surfaced. However, both runway ends are displaced and the total pavement length is approximately 2,983 feet long. The project limits identified for the runway and taxiways are shown in Appendix A. RDM’s scope of this project consisted of a pavement condition survey and functional evaluation considerations. Nondestructive testing or other forms of physical testing for the structural analysis pavements were not performed. All repair / rehabilitation recommendations are based on visual inspection of pavements. Following procedures detailed in FAA Advisory Circular 150/5380-7B, “Airport Pavement Management Program” and ASTM D 5340, “Standard Test Method for Airport Pavement Condition Index Surveys” , RDM performed a pavement condition survey for the runway and taxiway pavements within the project limits. The survey consisted of a visual inspection to identify pavement distresses at the surface resulting from the influence of aircraft traffic loading, environment weathering or erosion, and other factors relating to potential construction material deficiencies. To obtain a reliable estimate of distress repair quantities, 100% sampling was conducted. A hand-held GPS survey device was utilized to record the location, quantity, and severity for each distress. The collected data was used to develop detailed distress maps to identify areas that require repair. The distress maps can be found in Appendix A. The standard categories of distresses and causative Runway and Taxiway Rehabilitation at College Park Airport, MD Page 2 of 6 mechanism are shown in Table-1, "Airfield Distress Mechanisms". The distress type, severity rating, and quantity were measured and recorded according to the procedures outlined in ASTM D 5340. Table-1 Airfield Distress Mechanisms Asphalt Surfaced Airfield Pavements CODE DISTRESS MECHANISM 41 Alligator Cracking Load 42 Bleeding Other 43 Block Cracking Climate 44 Corrugation Other 45 Depression Other 46 Jet Blast Other 47 Joint Reflection Cracking Climate 48 Longitudinal/Transverse Cracking Climate 49 Oil Spillage Other 50 Patching Climate 51 Polished Aggregate Other 52 Raveling Climate 53 Rutting Load 54 Shoving Other 55 Slippage Cracking Other 56 Swell Other 57 Weathering Climate The specific objectives of the condition survey are: To determine the present functional condition of the pavement surface. To provide a common index for comparing the condition and performance of pavements, using the Pavement Condition Index (PCI). To develop pavement rehabilitation measures using functional evaluation results. For condition survey purpose, runway and taxiway pavements are subdivided into sections, based on pavement composition, construction history, aircraft traffic, and condition. Sample unit sizes generally consist of 5,000 square feet. Upon completion of the inspection, the recorded distresses were entered into the PAVER program to calculate the Pavement Condition Index (PCI) and distress quantities. PAVER is a pavement management system (PMS) software developed by the US Army Corps of Engineers, Construction Engineering Research Laboratory (CERL). Runway and Taxiway Rehabilitation at College Park Airport, MD Page 3 of 6 The PCI is based on a number of distinct distress types, quantities, and severities commonly found in airport pavements. After all distresses are measured and catalogued, the PCI is computed as a numerical rating index between 0 to 100, with a PCI of 100 being a pavement in "Good" condition (no distress) and a PCI of 0 being a pavement in “Failed” condition. This rating is assigned following the procedures detailed in ASTM and Advisory Circular. The PCI rating range with subjective description is shown below: RANGE CONDITION 86-100 Good 71-85 Satisfactory 56-70 Fair 41-55 Poor 26-40 Very Poor 11-25 Serious 0-10 Failed RESULTS The PCI values for each section of runway and taxiways are shown in Table 2, “Section Condition Report”. The PAVER re-inspection report is included in Appendix B. The re-inspection report includes the distresses recorded for each sample unit that was inspected. As shown in Table 2, the average PCI of Runway 15-33 is 58 or is rated as a “Fair” condition. The taxiway pavements within the project limits have average PCI values ranging from 27 to 96, with an overall area weighted average of 44 or is rated as a “Poor” condition. The section and sample PCI maps are included in Appendix A. Table 2 Section Condition Report True Section Branch ID Surface Use Area PCI ID (SqFt) RW1533 01 AC RUNWAY 180,532 58 TW1 01 AC TAXIWAY 42,410 33 TW1 02 AC TAXIWAY 30,690 32 TW2 01 AC TAXIWAY 7,453 42 TW3 01 AC TAXIWAY 4,933 68 TW3 02 AC TAXIWAY 2,093 27 TW3 03 AC TAXIWAY 7,111 96 TW3 04 AC TAXIWAY 9,706 92 TW4 01 AC TAXIWAY 2,285 37 TW4 02 AC TAXIWAY 10,532 44 Runway and Taxiway Rehabilitation at College Park Airport, MD Page 4 of 6 Runway 15-33 The primary distresses recorded on runway pavements were varying severities of longitudinal and transverse (L&T) cracking, depression, and raveling. Both L&T cracking and raveling usually indicate standard material aging from the hardened / oxidized asphalt and is not considered a structurally related concern. Overall, the condition survey data identified an insignificant quantity of structurally related distresses; therefore, functional condition repair will govern the rehabilitation. To correct the functional deficiencies, a mill and replace surface rehabilitation would normally be recommended. However, the core data suggests that the runway pavements are only 3 to 5.25 inches thick and an overlay of the existing AC surface would minimize potential construction impacts created by the thickness variation. A nominal AC scratch mill and overlay is recommended. The majority of high severity L&T cracks were measured to be approximately 2 to 3 inches wide. Therefore before milling, all high severity and other medium severity distresses identified should be repaired with deep patching. Using the above criteria, the patching location are identified and included in Appendix A. Taxiway The AC pavements within the parallel taxiway and connectors exhibit the following types of distresses: alligator cracking, depressions, L&T cracking, patching, rutting, and raveling. The majority of the AC pavement within the parallel taxiway and connector taxiways exhibit load related distresses such as alligator cracking and rutting. These distresses are an indication of structural failure. While, repair options like a mill and replace, crack sealing, or patching would repair the surface condition, it does not address the structural concern indicated by the distresses recorded. These areas need to be addressed with strengthening of the pavement to prevent further damage incurred by traffic loading. Therefore, it is recommended that a structural evaluation be performed to analyze the structural adequacy of the existing pavement section, including subgrade strength considerations, for proposed future aircraft and vehicular traffic data. The evaluation would also assist with the development of appropriate rehabilitation options based on the current structural and functional conditions. If the airport or Urban selects the prescribed scratch mill and overlay option, similar to runway pavements, all high severity and medium severity distresses should be repaired with deep patching before milling. Runway and Taxiway Rehabilitation at College Park Airport, MD Page 5 of 6 Table 3 shows the recorded distresses and proposed repair type for the runway and taxiway pavements and Table 4 identifies the minimum patching quantities recommended for each facility, the locations are mapped on the drawing “Patching Areas”, included in Appendix A. Table 3 Recorded Distresses and Repair Types Facility Distress Description Severity Quantity Units Repair Type RW1533 41 Alligator Cracking Medium 11 SqFt Deep Patching RW1533 45 Depression Medium 774 SqFt Deep Patching RW1533 48 L&T Cracking Medium 12,671 Ft Crack Sealing RW1533 48 L&T Cracking High 556 Ft Deep Patching RW1533 52 Raveling Medium 142 SqFt Deep Patching RW1533 52 Raveling High 234 SqFt Deep Patching Taxiway 41 Alligator Cracking Medium 849 SqFt Deep Patching Taxiway 41 Alligator Cracking High 758 SqFt Deep Patching Taxiway 45 Depression Medium 552 SqFt Deep Patching Taxiway 45 Depression High 28 SqFt Deep Patching Taxiway 48 L&T Cracking Medium 2,900 SqFt Crack Sealing Taxiway 48 L&T Cracking High 1,731 SqFt Deep Patching Taxiway 50 Patching Medium 375 SqFt Deep Patching Taxiway 52 Raveling Medium 193 SqFt Deep Patching Taxiway 52 Raveling High 758 SqFt Deep Patching Identified Patching Quantities Identified Patching Facility Unit Quantity RW1533 5,344 SqFt TW1 30,752 SqFt TW2 673 SqFt TW3 1,046 SqFt TW4 4,061 SqFt APPENDIX A MAPS RW1533_01 TW4_01 TW3_02 TW3_01 TW2_01 TW1_02 TW1_01 TW4_02 TW3_03 TW3_04 0 200 400