This work shall consist of modifying the subgrade with water and a modifier to increase resiliency.
(A) All city streets shall be constructed with an improved subgrade, which will consist of a 12 inch thick layer of lime, cement modified subgrade, or aggregate granular material as recommended by a geotechnical engineer.
(B) Construction specifications. The contractor is responsible to prepare modified subgrades properly graded to the lines and grades shown on the plans for the given project and according to IDOT Standard Specifications § 302 except as otherwise noted.
(C) Proportioning. If lime or cement modified soil is proposed, a mix design for the proportions of modifier, soil, and water is required. The mix design should be based on actual soil samples and prepared by a geotechnical engineer licensed in the State of Illinois. Modifiers shall be proportioned within a range of 2% to 6% of the weight of soil based on the oven dry basis.
(D) Lime or cement modifiers shall not be applied when wind conditions are such that blowing modifiers become objectionable to adjacent property owners, or creates a hazard to traffic on adjacent highways. In a densely developed area - especially a residential area - the code enforcement official may require lime or cement modifiers be applied in a slurry form to avoid blowing.
(E) A rotary speed mixer is required for tilling the modifier (i.e., lime or cement).
(F) Water and the modifier shall be directly injected into the soil with equipment capable of measuring the application rate to ensure adherence to the mix design.
(G) Substitutions. If subgrade soil modification is impractical, the City Engineer may allow a 12 inch thick granular (i.e., rock) subbase according to § 153.038.
(Ord. 2016-29, passed 11-7-2016)