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   Section 3307 of the CBC is adopted by reference, except Section 3307.1 of the CBC is not adopted; and, in lieu, LAMC Subsections and Subdivisions 91.3307.1, 91.3307.2, 91.3307.2.1, 91.3307.2.2, 91.3307.3, 91.3307.3.1 and 91.3307.3.2 are added. (Amended by Ord. No. 185,587, Eff. 7/16/18.)
91.3307.1. Protection Required. Adjoining public and private property shall be protected from damage during construction, remodeling and demolition work. Protection must be provided for footings, foundations, party walls, chimneys, skylights and roofs. Provisions shall be made to control water runoff and erosion during construction or demolition activities.
   For excavations, adjacent property shall be protected as set forth in Section 832 of the Civil Code of California.
   Prior to the issuance of any permit, which authorizes an excavation where the excavation is to be of a greater depth than are the walls or foundation of any adjoining building or structure and located closer to the property line than the depth of the excavation, the owner of the site shall provide the Department of Building and Safety with evidence that the adjacent property owner or owners have been given a 30-day written notice of the intent to excavate. This notice shall state the depth to which the excavation is intended to be made and when the excavation will commence. This notice shall be by certified mail, return receipt requested.
91.3307.2. Underpinning.
91.3307.2.1. General. In constructing underpinning, all portions of the structure shall be supported so that no structural material is stressed beyond the yield point.
91.3307.2.2. Closure. All spaces between the existing footing and the underpinning shall be packed full of mortar conforming to the provisions of CBC Section 2103 and having no slump when tested by the method specified in ASTM C 143.
91.3307.3. Temporary Excavations and Shoring.
91.3307.3.1. General. Excavations shall not remove the lateral support from a public way, from an adjacent property or from an existing structure. For the purpose of this section, the lateral support shall be considered to have been removed when any of the following conditions exist:
   1.   The excavation exposes any adverse geological formations, which would affect the lateral support of a public way, an adjacent property or an adjacent structure.
   2.   The excavation extends below a plane extending downward at an angle of 45 degrees from the edge of the public way or an adjacent property.
   EXCEPTION: Normal footing excavations not exceeding two feet in depth will not be construed as removing lateral support.
   3.   The excavation extends below a plane extending downward at an angle of 45 degrees from the bottom of a footing of an existing structure.
91.3307.3.2. Removal of Lateral Support. (Amended by Ord. No. 186,488, Eff. 12/27/19.) Approval of the Department of Public Works shall be obtained prior to the issuance of a permit for any excavation that would remove the lateral support from a public way.
   The slopes of excavations adjacent to an existing structure, an adjacent property or public way may exceed one horizontal to one vertical where either:
   1.   A soil report recommending that the slope may be in excess of one to one has been approved by the Department and the Department of Public Works when the excavation is adjacent to a public way.
   When justified by the soils engineer, the Department may approve the use of the proposed building and/or shoring to support an adjacent structure on an adjoining property in lieu of underpinning, provided:
   (i)   Evidence is submitted that the adjoining property owner has been notified in advance of the proposed excavation in compliance with Section 832 of the Civil Code of California.
   (ii)   The owner of the site records a sworn affidavit with the Office of the County Recorder, which will inform future owners of the site that the lateral support of a portion of the building footings on the adjoining property is provided by the subterranean walls of the building on the site.
   2.   Underpinning is designed to support adjacent structures, temporary shoring is designed to support the excavation, and plans are approved and permits are issued by the Department.
   Temporary shoring shall be designed for an earth pressure recommended by a soils engineer and approved by the Department, equivalent to that exerted by a fluid weighing not less than 24 pounds (11 kg) per cubic foot plus all surcharge loads.
   Soils bearing values shall be those specified in Division 18, Article 1, Chapter IX of the LAMC or those recommended by a soils engineer and approved by the Department.
   The design of the required temporary shoring and necessary underpinning shall include a sequence of construction and installation.
   Allowable stresses used in the design of temporary shoring may be increased 33-1/3% for structural and reinforcing steel and 25% for wood. No increase will be permitted for concrete. Other values shall be those prescribed by this Code.