Section 58. It is hereby declared (a) that there exist in certain cities and towns in the commonwealth substandard dwelling houses in urban renewal project areas which constitute a serious and growing menace and create a housing shortage, injurious to the public health, safety, morals and welfare of the residents of the commonwealth, and the declarations heretofore made in this chapter with respect to such areas are hereby reaffirmed; (b) that while many of such dwelling houses may require acquisition and clearance as provided in this chapter because their state of deterioration may make impracticable their reclamation by conservation or rehabilitation, others in such areas are in such condition that they may, through the means provided in section fifty-nine, be conserved or rehabilitated in such a manner that the conditions and evils hereinbefore enumerated may be alleviated or eliminated so that such dwelling houses may be returned to or remain in private ownership and be available as decent, safe and sanitary housing; and (c) that all powers conferred by said section fifty-nine are for public uses and purposes for which public money may be expended.