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iii. After backfill and placing a tack coat on the existing asphalt edges, the final <br /> patch shall be constructed with 6-inches of compacted HMA placed in the <br /> window cut up to finished grade per WSDOT Standard Specifications Section <br /> 5-04. <br /> 3. Any trench in a roadway that is to be resurfaced by the County Overlay Program <br /> within 12 months shall be backfilled to the bottom edge of the existing asphalt <br /> or within 4-inches of existing road grade, whichever is greater, with bank run <br /> gravel or CSTC, compacted to 95% of maximum density, or with Controlled <br /> Density Fill (CDF) when required by the Engineer in accordance with Section 8- <br /> 07 of this chapter, to minimize settlement. The backfill shall be covered by <br /> temporary asphalt as specified in Section 8-05.C.(1),ii or 8-05.C.(2).11 above. <br /> 4. Water settling of backfill in trenches under existing roadways is not permitted. <br /> 5. Temporary restoration of trenches for overnight use shall be accomplished by <br /> using asphalt or steel plates. Asphalt used for temporary restoration may be <br /> dumped directly into the trench, bladed out, and rolled. After rolling, the trench <br /> shall be filled flush with asphalt to provide a smooth riding surface. Asphalt <br /> materials used for temporary patching must be removed prior to placement of <br /> the permanent patch. <br /> 6. Final patches shall conform to the requirements of this chapter and shall be <br /> completed as soon as possible but no later than 30 days after first opening the <br /> trench, multiple window cuts, or a single window cut. Any delay in placement of <br /> the final patch shall be approved by the Engineer. <br /> 7. Work located outside the paved portion of the roadway (i.e. in the sidewalk, <br /> walkway, planter strip, or gravel shoulder) regardless of how close to a window <br /> cut (single or multiple) or trench in the paved portion of the roadway (i.e. curb <br /> to curb, shoulder to shoulder, or curb to shoulder) is subject to the restoration <br /> requirements of sub-sections 8), 9), or 10) below as applicable. <br /> 8. Concrete pavement shall be restored in accordance with WSDOT/APWA Standard <br /> Specifications Section 5-05. If concrete panels in an existing road are cut by a <br /> trench, the Engineer may require removal of the panels to ensure road stability. <br /> 9. Gravel shoulders disturbed by excavation shall be replaced full width with 6 <br /> inches of crushed surfacing top course (CSTC) meeting the specifications of the <br /> WSDOT/APWA Standard S ecifications Section 9-03.9(3). <br /> 10. Any cut or damage to permeable pavement shall be restored with the same <br /> permeable pavement, to an equivalent or better condition as determined by the <br /> Engineer. Paving over permeable pavement with conventional asphalt, concrete <br /> or other impermeable material invalidates prior stormwater design assumptions, <br /> creates the potential for runoff to exceed a conveyance or infiltration system, <br /> and shall not be allowed unless approved by the Engineer. Permeable pavement <br /> shall be restored in accordance with manufacturer's specifications by contractors <br /> qualified either by previous experience (at least three permeable pavement <br /> projects within the past five years) or certification by an appropriate trade <br /> organization, such as the National Ready-Mix Concrete Association. The <br /> pavement restoration plan shall be approved by the Engineer. <br /> 8-12 Engineering Design and Development Standards <br /> September 17, 2021 <br />