The following activities are exempt from the letter of authorization, permit, and mitigation requirements of this subtitle: Forestry activities. Agricultural activities in COMAR 26.23.05.01B. All other agricultural activities are exempt from the permit requirements of this subtitle, but are subject to the mitigation requirements of COMAR 26.23.04.01 and COMAR 26.23.04.03—.07. Approved mitigation projects required under this subtitle. Any proposed regulated activity conducted by a person who has applied to the U.S. Army Corps of Engineers by December 31, 1990, for a permit under §404 of the Clean Water Act, provided that the following conditions are satisfied: The U.S. Army Corps of Engineers ultimately issues a permit or other document under §D(3) of this regulation; The applicant does not alter the scope of the regulated activity originally applied for without authorization from the U.S. Army Corps of Engineers; A person submits the following information to the Department, as may be applicable, and as may be requested by the Department: A copy of a dated application for a permit under §404 of the Clean Water Act; A copy of the plans for the project which were submitted to the U.S. Army Corps of Engineers; A letter from the U.S. Army Corps of Engineers describing the project and proposed activity and stating one of the following: The project and proposed activity is authorized by the U.S. Army Corps of Engineers; The proposed activity is exempt from §404 of the Clean Water Act permit requirements. Activities within farmed nontidal wetlands and their buffers, excluding farmed nontidal wetlands with 15 or more consecutive days of inundation during the growing season, and their buffers. The duration of inundation is determined by the Department consistent with federal agency procedures adopted pursuant to the Food Security Act of 1985, 16 U.S.C. §3801 et seq. The following activities, if they do not result in cumulative direct or indirect adverse impacts: Construction of additions, outbuildings, and accessories to existing structures within a landscape management area which impacts less than 1,000 square feet of nontidal wetlands; Construction placed on existing impervious surfaces or on structures within the buffer or expanded buffer; Removal of 30 percent of the trees in the buffer, provided that: The density but not the areal extent of the trees is reduced; and Not more than 30 percent of the understory is removed; Mowing or other forms of vegetation control on existing rights-of-way; The control of State-designated noxious weeds; Landscape management in the nontidal wetland, buffer, or expanded buffer; Soil investigations; Percolation tests for sewage disposal fields; Survey markers or survey monuments; Other similar activities with minimal adverse impacts as approved by the Department; The maintenance of the following serviceable structures or fills: Aboveground and underground utilities; Structures in rights-of-way; Railroad beds; Road beds, roadside ditches, culverts, outlet ditches, wash ponds, and temporary sediment control structures; Bridges; Dams; Dikes; Levees; Water and wastewater control structures; and Facilities designed for storm water management; Within the Critical Area, a cumulative removal of 10 percent of the trees within the buffer or expanded buffer, if: The density but not the areal extent of the trees is reduced; and Not more than 10 percent of the understory is removed.