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The recommended improvements were designed considering the effects of a planned detention basin upstream (see Sheet 8)., The berming north and east of the hi gh schoo I tenni s courts and the connect i ng emergency spi 11 way channel were also designed in conjunction with the detention facility. The detention facility cost estimate reported for this sheet reflects the berming and the proposed spillway channel as shown on Sheet 7 of 12. ITEM COST I I I I I I I I I I I I I I I I I I I COMMENTARY - SHEET 7 OF 12 Maintenance agreements or easements should be firmed up by the City for privately-owned reaches of channel downstream of 23rd Street. The channel reach between 23rd and 24th Streets is currently City-owned with the recommended maintenance access shown on the drawing. The recommended plan for thi s reach i ncl udes 100-year channel i zat i on through the Golden High School property to a point approximately 300' downstream of 23rd Street. The 23rd and 24th Street crossings will be replaced with 100- year capacity culverts. Drop structures will provide velocity control for high and low flows. Floodplain regulations should continue to be enforced until improvements have been constructed. Private property owners should be encouraged to purchase flood insurance. Individual floodproofing should also be encouraged. COST ESTIMATE - SHEET 7 OF 12 The plan focuses on keeping 100-year flows tributary to the West Fork channel area as opposed to the existing condition of wide overbank flooding upstream of the high school and flow separation at the 23rd and 24th Street crossings. This condition would reduce the amount of flow tributary to the shallow flooding area along Jackson Street. Channel Improvements Street Crossings Utility Relocation Detention Facility $165,000 142,000 9,600 56,100 Subtotal Contingencies (15%) Engineering, Legal & Administrative (15%) 372,700 55,905 55,905 TOTAL CONSTRUCTION COST 484,510 Options are available for the West Fork channel along the Golden High School property, including the do-nothing alternative or a softer solution, such as construct i ng a ri prapped channel to handl e 10-year fl ows and a grass-l i ned bank for higher flows. A softer solution would be less expensive to construct, but would require repairs in the event of a major flood. The do- nothing alternative could also be justified knowing that upstream improvements do not serve to worsen the existing condition. It is recommended that replacement of the foot bridge be strongly considered since the existing structure obstructs a high percentage of the channel area. Costs for the hi9h school channelization are reported as City of Golden costs followin9 this commentary. Right-of-Way Acquisition 161,000 TOTAL CAPITOL COST OF IMPROVEMENTS 645,510 TOTALS IN EACH JURISDICTION City of Go I den Jefferson County 645,510 -0- Annual Operation and Maintenance Costs (2,700)