Miss. Code § 65-17-201
[With regard to any county which is exempt from the provisions of Section 19-2-3, this section shall read as follows:]
The boards of supervisors of the several counties of the State of Mississippi are authorized and empowered at their discretion to employ, as county engineer, a civil engineer or person qualified to perform the duties of a county engineer, and such assistant engineers as may be necessary. On all projects for the construction or reconstruction of a bridge which will cost more than Five Thousand Dollars ($5,000.00), or for the construction or reconstruction of roads which will cost more than Five Thousand Dollars ($5,000.00) per mile, the employment of an engineer qualified under the chapter on engineers shall be obligatory, whether the work is being done by the county or by a separate district, and whether the work is to be done by contract or otherwise; however, in obligatory cases the employment may be for the particular work, rather than for a term.
Miss. Code § 65-17-201