The City Engineer may authorize in writing the release of a portion of the security in conjunction with the acceptance of the satisfactory completion of a part of the improvements as the work progresses upon application by the subdivider.

No such release shall be for an amount less than ten percent of the total improvement security given for faithful performance and the security shall not be reduced to an amount less than fifty percent of the total improvement security given for faithful performance. In no event shall the City Engineer authorize a release of the improvement security which would reduce such security to an amount below that required to guarantee the completion of the improvements and any other obligation imposed by this title, the Subdivision Map Act, or the improvement agreement. (Ord. 5793-NS § 2 (part), 1987)