This chapter shall not require installation of any particular improvement as to any particular property, or portion thereof, nor the posting or maintenance of any particular guaranty of installation, where the city council determines, after favorable recommendation by the director of public works, that such requirement would impose an unusual hardship upon the property owner because of the nature of neighboring development, or for other proper reasons would not carry out the policy of this chapter, but in such cases, the city council may require other appropriate guarantees. (Ord. 711 NCS §1; prior code §21.78(3).)