Any county or city which elects to construct and operate therein a separate sewage disposal system in accordance with the foregoing provisions of § 21-203 shall, within the period hereinafter limited for the construction of such sewage disposal system, construct and provide and have in operation in such county or city a sewage disposal system sufficient in the opinion of the State Health Commissioner to prevent the pollution of any and all tidal waters of the district, and any and all tidal waters within the county or city, from industrial wastes and sewage arising in or discharged from the county or city; and the commission is authorized and empowered to proceed by appropriate court action to require the county or city and the governing body thereof to provide therein such required sewage disposal system. From and after the expiration of such period, no such county or city nor any public body or person therein shall discharge or suffer to be discharged directly or indirectly into any tidal waters of the district, or tidal waters in such county or city, any sewage, industrial wastes or other refuse which may or will cause or contribute to pollution of any such tidal waters; this provision shall be enforceable in the manner provided for by § 21-220. The period for the construction of such sewage disposal system, as hereinabove referred to, shall be three years from the creation of the district and such further period of time, not exceeding an additional two years, as the commission, upon application of the governing body of the county or city and after public hearing which shall be held by the commission upon such public notice as the commission may determine to be reasonable, may find to be necessary for completion of such construction by reason of causes which shall not be or have been within the control of such county or city or the governing body thereof.