Ind. Code § 8-23-6-2
If the construction of a street necessitates the construction of adequate connecting facilities outside the limits of the street to provide for drainage of the street, the necessary mains, laterals, and connections shall be provided for in the plans, included as part of the construction cost, and paid out of the department's appropriation. However, if the drainage facilities outside the street are to be used for a purpose or purposes in addition to that of draining the street, a proportionate share of the cost of construction shall be paid by the beneficiaries of the drainage other than the department in a ratio of the amount of waste water attributable to the other users as compared with the total capacity of the drainage facilities. The department shall determine the ratio. The department need not proceed with construction until the time that an agreement with the municipality has been effected concerning the payment of costs for drainage use other than that which is required for state highway drainage. If the construction of a street in the state highway system within the boundaries of a city or town necessitates the construction of a bridge, overhead or subway structure, and sidewalks are required as a part of the structure, the sidewalks shall be provided for in the plans, included as part of the construction cost, and paid out of the department's funds.
IC 8-23-6-2