In lieu of the required improvements, the city's traffic engineer may accept from any responsible person a contract to make such improvements. The improvements shall be completed within the time specified in the agreement to improve, except that the city's traffic engineer may grant such additional time as he or she deems necessary if, in the opinion of the city's traffic engineer, a good and sufficient reason exists for the delay.

Such contract shall be accompanied by a deposit with the city of a sum of money or negotiable bonds or savings and loan certificates or shares in an amount which, in the opinion of the traffic engineer, equals the cost thereof. If savings and loan certificated or shares are deposited, the owners shall assign such certificates or shares to the city.

If the estimated cost of the improvements equals or exceeds $1,000, in lieu of such deposit the applicant may file with the city a corporate surety bond guaranteeing the adequate completion of all of the improvements, in a sum equal to such estimated cost.

Upon the failure of the responsible person to complete any improvement within the time specified in an agreement, the city council may, upon notice in writing of not less than 10 days served upon the person, firm or corporation signing such contract, or upon notice in writing of not less than 20 days served by registered mail addressed to the last known address of the person, firm or corporation signing such contract determine that the improvement work or any part thereof is incomplete, and may cause to be forfeited to the city such portion of deposits or bonds given for the faithful performance of the work, or may cash any instrument of credit so deposited in such amount as may be necessary to complete the improvement work.

Property adjoining on both sides of the subject property is developed with lawfully existing buildings or structures which, were they not already existing, would be subject to the provisions of this chapter, and the requirement to dedicate, pave or improve would require a greater width than is the highway or street in front of the existing buildings or structures on the said adjoining properties;

The lot or parcel of land adjoins a parkway, major or secondary highway or street for a distance of 100 feet or more, and only a portion of the lot or parcel of land is to be used for such building or structure or occupied by such use;

There is in existence or under negotiation a contract between the city and a contractor to install the required improvement;

The city engineer is unable to furnish grades within 120 days;

The city engineer has determined that the required construction would adversely affect drainage or traffic;

The construction will be isolated from a continuous roadway which may not be improved for many years; or

There are in existence partial improvements satisfactory to the city's traffic engineer, and he or she deems construction of additional improvements to be unnecessary or constitute an unreasonable hardship.