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.
Method and coverage
Regional considerations
A nuclear density gauge is the first tool we carry onto a Savannah paving job because density is the metric that makes or breaks the design. The AASHTO 93 structural number calculation assumes the base and asphalt layers hit their target densities, but on a humid August morning with the subgrade sweating moisture, achieving 98 percent modified Proctor takes more than just roller passes. We see contractors rush the compaction sequence and leave the bottom lift of asphalt at 91 percent density, which triggers top-down fatigue cracking within three years. The other failure mode we track is stripping in the asphalt layer: Savannah's frequent afternoon thunderstorms combined with marginal aggregate mineralogy can delaminate the binder from the stone. Our design specs always include an anti-strip additive and a minimum tensile strength ratio of 80 percent per AASHTO T 283 for the mix.
Standards that apply
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), GDOT Standard Specifications, Section 815 (Graded Aggregate Base)
Complementary services
Pavement structural section design
AASHTO 93 layer thickness and material specification for flexible pavements, including resilient modulus input from laboratory triaxial or CBR correlation.
Subgrade evaluation and stabilization
In-situ strength testing, soil classification, and lime or cement stabilization recommendations for Savannah's high-plasticity clays.
Drainage analysis for pavement systems
Permeability testing of subgrade and base materials, edge drain design, and drainage coefficient determination for the structural number calculation.
Construction QA and density testing
Nuclear density gauge verification, asphalt core extraction, and compaction compliance reports per GDOT and AASHTO standards.
Typical parameters
Q&A
How much does flexible pavement design cost for a commercial parking lot in Savannah?
For a typical commercial parking lot project within Chatham County, the fee for pavement structural design, subgrade investigation, and construction QA typically falls between US$1,450 and US$4,780 depending on the number of borings, the traffic loading analysis required, and whether MEPDG modeling is included.
Why does Savannah need a different pavement design than inland Georgia cities?
Savannah's high groundwater table, low elevation, and prevalence of soft alluvial clays create subgrade conditions that are fundamentally different from the Piedmont residual soils found in Atlanta or Macon. The design must account for near-surface saturation, reduced subgrade resilient modulus during wet seasons, and the risk of base course pumping, none of which is as critical on well-drained upland sites.
What asphalt binder grade is appropriate for Savannah's climate?
We specify PG 70-22 for most Savannah flexible pavements. This grade covers the high pavement surface temperatures reached during July and August afternoons on unshaded asphalt, while the low-temperature grade handles the occasional hard freeze that can occur on winter nights. For heavily trafficked intersections, we sometimes step up to PG 76-22 to resist rutting under standing loads.