Cities of the metropolitan class in the State of Nebraska are hereby authorized and empowered to issue and sell special assessment sewer bonds, said bonds not to exceed two hundred thousand dollars, without a vote of the electors, and to use the proceeds of such bonds for the purpose of constructing or reconstructing storm or sanitary sewers where at least five-sixths of the cost of same will be borne by some agency of the government of the United States of America. All principal and interest of such bonds shall be payable solely from the proceeds of special assessments levied and collected on real estate within special assessment sewer districts and, as shall be recited in such bonds, such city shall incur no liability, obligation, or indebtedness of any kind or nature thereon, and the city shall not pledge its credit, its general taxing power, or any part thereof to support or pay the same. Such bonds shall be sold or exchanged for not less than the par value thereof and shall bear interest at a rate not to exceed the rate of interest specified in section 45-104.01, as such rate may from time to time be adjusted by the Legislature, payable semiannually. Special assessments levied for the purpose of paying such bonds shall be made payable in ten equal annual installments. The first installment shall be due and delinquent fifty days from the date of levy, the second, one year from date of levy, and a like installment shall be due and delinquent annually thereafter until all such installments are paid. Each of said installments, except such as are paid within fifty days from the date of levy, shall draw interest at a rate not to exceed the rate of interest specified in section 45-104.01, as such rate may from time to time be adjusted by the Legislature, from date of levy aforesaid until the same shall become delinquent, and after the same shall become delinquent, shall draw interest at the rate specified in section 45-104.01, as such rate may from time to time be adjusted by the Legislature. Such assessment shall be collected and enforced as in other cases of special assessments. All such special assessments and all interest accruing thereon in any district in which such bonds are issued and sold shall constitute a sinking fund and shall be used solely for the purpose of paying the interest on the bonds so issued and sold as the same accrues and for paying the principal sum of such bonds at the maturity thereof. All powers herein granted are further and in addition to any other powers which may now have been or hereafter may be conferred upon any such city.