The most expensive mistake we see on Savannah projects is a flexible pavement section designed from a textbook without accounting for the local water table. The city sits barely 15 meters above sea level, and the surficial aquifer can rise to within inches of the subgrade during a wet summer. A pavement that looks fine on a FWD deflection basin will pump fines and rut within two seasons if the base course is saturated. We approach flexible pavement design here as a drainage problem first and a structural problem second. The CBR road testing we run on the subgrade tells only part of the story; without understanding how the in-situ permeability of the untreated subgrade interacts with Savannah's 1,270 mm of annual rainfall, the layer coefficients you plug into the AASHTO 93 equation are just guesses.
A flexible pavement in Savannah is a hydraulic system as much as a structural one: if water cannot escape the base course, the section fails from the bottom up.
Process and scope
Local ground factors
On a Savannah paving project, the initial tool we bring is a nuclear density gauge because density is the critical metric determining design success. The AASHTO 93 structural number calculation expects base and asphalt layers to meet target densities, yet during a humid August morning when the subgrade is releasing moisture, reaching 98 percent modified Proctor requires more than just roller passes. We observe contractors rushing the compaction sequence, resulting in the bottom asphalt lift achieving only 91 percent density, which leads to top-down fatigue cracking within three years. Another failure pattern we monitor is stripping in the asphalt layer: Savannah's frequent afternoon thunderstorms paired with marginal aggregate mineralogy can separate the binder from the stone. Our design specifications always incorporate an anti-strip additive and a minimum tensile strength ratio of 80 percent per AASHTO T 283 for the mix.
Reference standards
The standards and guidelines referenced include the AASHTO Guide for Design of Pavement Structures (1993), AASHTOWare Pavement ME Design (NCHRP 1-37A), ASTM D1557 (Modified Proctor), AASHTO T 283 (Tensile Strength Ratio), and GDOT Standard Specifications, Section 815 (Graded Aggregate Base).
Other technical services
Pavement structural section design
For flexible pavements, AASHTO 93 specifies layer thickness and material requirements, incorporating the resilient modulus derived from laboratory triaxial tests or CBR correlation.
Subgrade evaluation and stabilization
Recommendations for in-situ strength testing, soil classification, and stabilization with lime or cement are provided for Savannah's high-plasticity clays.
Drainage analysis for pavement systems
To determine the drainage coefficient for the structural number calculation, permeability testing of subgrade and base materials, edge drain design, and analysis are performed.
Construction QA and density testing
Compaction compliance reports, asphalt core extraction, and nuclear density gauge verification are carried out in accordance with GDOT and AASHTO standards.
Typical parameters
Frequently asked questions
How much does flexible pavement design cost for a commercial parking lot in Savannah?
For a typical commercial parking lot project in Chatham County, the fee for pavement structural design, subgrade investigation, and construction QA generally ranges from US$1,450 to US$4,780, depending on the number of borings, the required traffic loading analysis, and whether MEPDG modeling is included.
Why does Savannah need a different pavement design than inland Georgia cities?
Savannah's subgrade conditions are fundamentally different from the Piedmont residual soils in Atlanta or Macon due to the area's high groundwater table, low elevation, and prevalence of soft alluvial clays. The design must address near-surface saturation, reduced subgrade resilient modulus during wet seasons, and the risk of base course pumping—factors that are far less critical on well-drained upland sites.
What asphalt binder grade is appropriate for Savannah's climate?
Most Savannah flexible pavements are specified with PG 70-22 binder. This grade accommodates the high pavement surface temperatures experienced during July and August afternoons on unshaded asphalt, while the low-temperature grade handles the occasional hard freeze that may occur on winter nights. For heavily trafficked intersections, we sometimes upgrade to PG 76-22 to resist rutting under standing loads.