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SWP272264(17)
5 EPA 1 Project Description For Corps Permit Applicatio 1 Maplewood Creek Flooding and 1 Habitat Improvement Projects ' November 1995 Prepared for City of Renton, Washington 1 1 Prepared by HARZA i 1 1 Project Description For Corps Permit Application p p pp i 1 Maplewood Creek Flooding and 1 Habitat Improvement Projects November 1995 Prepared for ' City of Renton, Washington 1 Pr epared by ' HARZA Project Description for Corps Permit Application i TABLE OF CONTENTS ' I. Executive Summary..................................................................I II. Background Information............................................................I Description of Maplewood Creek ...................................................................2 Fisheries Information..................................................................................2 ' Hydrology and Flooding ..............................................................................3 Relationship of the Proposals to Recent Planning Efforts.......................................4 III. Project Descriptions..................................................................5 ' Low-Flow Fish Passage Channel Project ..........................................................5 Introduction ......................................................................................5 Proposed Project Elements ....................................................................6 Impacts Due to Construction..................................................................8 FutureMaintenance.............................................................................8 Sedimentation Basin Reconstruction and Improvements Project...............................8 Introduction ......................................................................................8 Proposed Project Elements ....................................................................9 Impacts Due to Construction................................................................ 12 FutureMaintenance........................................................................... 13 Maplewood Creek High-Flow Capacity Improvements ....................................... 13 Introduction .................................................................................... 13 Impacts Due to Construction................................................................ 14 ' Future Maintenance........................................................................... 15 IV. Benefits ............................................................................... 15 V. Impacts........................................................... i Figures la. Project Vicinity Map lb. Project Vicinity Map 2a. Schematic Site Plan 2b. Adjacent Property Ownership Information 3a. Low-Flow Fish Passage Channel Conceptual Planting Design Plan View Maplewood Creek Flooding and Habitat Improvement Projects Page ii WPC\95PRO1 V 163G\FLOODHAB.DOC\01/23/%6 9:08 AM\SDC 1 Project Description for Corps Permit Application 3b. Low-Flow Fish Passage Channel Section View of Channel Design 4a. Proposed Sedimentation Basin Improvements Site Plan and Sections 4b. Proposed Sedimentation Basin Improvements Site Plan and Sections (cont.) 5. Proposed Sedimentation Basin Spillway and Outlet Plans, Sections and Details 6. Proposed Sedimentation Basin Fishway Outlet Plans, Sections and Details 7. Proposed Improvements to Existing Creek Channel Plan and Sections ' Maplewood Creek Flooding and Habitat Improvement Projects Page iii WPC\95PROJ\7167G\FLOODHAB.DOC\01/27/96\9:08 AWSDC Project Description for Corps Permit Application MAPLEWOOD CREEK FLOODING AND HABITAT IMPROVEMENT PROJECTS i I. Executive Summary The City of Renton is proposing three projects along lower Maplewood Creek in Renton, Washington (Figures 1 and 2). All three projects are located on the City of Renton's ' Maplewood Golf Course. The three projects include: 1) construction of a new low-flow fish passage channel across the golf course, 2) reconstruction and improvement of two existing sediment ponds, and 3) high-flow capacity improvements to the existing Maplewood Creek channel. The first two projects are planned to be constructed this year. The third project, the ' high flow capacity improvements is not currently scheduled for construction. Complete descriptions of the three projects are provided in Section III of this document. The projects are intended to mitigate flooding and so protect public and private property, to improve instream habitat conditions and the opportunity for upstream fish migration past the golf course, and to reduce sediment deposition in the creek channel below the sediment basin. Construction of the new low-flow fish passage channel will not involve any dredging or filling of surface water or wetlands. Therefore, this construction activity is not a part of the Corps permit application. However, the City is aware that water cannot be diverted from Maplewood Creek to the new channel until a Corps permit is issued, authorizing ' this diversion. The sedimentation basins and existing Maplewood Creek are also subject to regulation by the Corps of Engineers. Therefore complete descriptions of all three projects 1 are included in this Project Description. Wetlands along Maplewood Creek meet the City of Renton's criteria for Category 3 wetlands, due to channelization of the creek and alteration of the soils. Effects on the wetland buffer area ( 25 feet on either side of the wetland boundary, based on urban zoning) will be temporary, and no adverse impacts are anticipated. The existing and future sedimentation basins do not meet the City's definition of regulated wetlands because they are managed as stormwater facilities. II. Background Information Maplewood Creek is a minor tributary of the Cedar River. The confluence of Maplewood Creek is located at about Cedar River mile 3.3. (Figures la and lb show the iMaplewood Creek Flooding and Habitat Improvement Projects Page I WPC\95PR03\7163G\FLOODHAB.DOC\01/23/96\9:03 AM\SDC Project Description for Corps Permit Application general site location of the projects.) The total basin area contributing to Maplewood Creek is ' small, about 1,100 acres. One-third of the basin (primarily the south and west) is within the City of Renton's corporate limits. The remainder of the basin is in unincorporated King ' County (within the Urban Growth Area). The total length of Maplewood Creek is 1.8 miles, 1.4 miles long to the top of the plateau above the Cedar River valley. ' The project reach for the low-flow fish passage channel would extend from RM 0.0 to 0.4 across the golf course (from RM 0.0 because the low-flow channel to the fish ladder would ' bypass the existing 900-foot culvert described below). The project reach for sediment pond reconstruction would be the area of the existing sediment ponds between RM 0.4 and 0.5. The project reach for the high-flow capacity improvements would include that portion of the existing Maplewood Creek channel between RM 0.1 and 0.4. (Figure 2a shows the relationships of each project to one another.) Description of Maplewood Creek Conditions found along the length of Maplewood Creek vary widely. The first part of the creek above the Cedar River is contained within a 900 foot long 72-inch diameter culvert. The creek reaches the north side of SR 169 and the Maplewood Golf Course at RM 0.2, and then crosses the golf course in a drainage ditch to meet the existing sediment ponds at RM 0.4 Along the golf course reach the creek banks are vegetated primarily with grasses and forbs typical of disturbed areas, and the reach is devoid of in-channel structure. The area has been ' landscaped and undergoes heavy use as part of the golf course. (Photos of this reach are included in the Wetland Delineation Report submitted with the Corps permit application.) Two existing sediment ponds are located above the golf course in the mouth of the ravine. Hillsides surrounding the ponds are wooded, but slopes east of the ponds are unstable and contribute large amounts of coarse sands and silts directly into the ponds. From the upstream sediment pond (RM 0.5 to the top of the plateau at RM 1.4), the stream is confined in a steep, heavily wooded ravine. ' Maplewood Creek generates a significant sediment load for a creek of its size. This sediment load adversely impacts downstream habitat, land uses, and property. The creek's primary source of sediment is the canyon that Maplewood Creek drops through (more than 300 feet vertically) from the Renton Plateau to the Cedar River. As the creek descends the ravine it cuts through highly erodible soils and transports those soils to the Cedar River floodplain. Above the golf course, the creek deposits those sediments in the two existing ponds. Once those ponds are tilled to capacity with sediments (this currently occurs several Maplewood Creek Flooding and Habitat Improvement Projects Page 2 WPC\95PR01\71 G3C\FLOOD HAB.DOC\01/23/96\9:03 AM\SDC Project Description for Corps Permit Application times a year), sediments are then transported down into the golf course reach where the sands 1 and silts settle in the creek channel and downstream culvert under SR 169. The sediment reduces the system's conveyance capacity and chokes gravels that would otherwise be suitable for salmon spawning. ' Fisheries Information Use of Maplewood Creek by salmon and other anadromous fish is limited by the ' culvert system at the confluence of the creek and the Cedar River. The culvert's outfall blocks fish access to the creek except during high Cedar river flows. The old water supply dam at 1 the downstream end of the upper sediment pond has also probably blocked anadromous fish use of upper Maplewood Creek since its construction, in about 1930. According to the Lower Cedar River Current and Future Conditions Report (King County, 1993), the lower portion of the ravine (RM 0.5-0.75) contains good habitat. Habitat in higher stream reaches (generally in the upper 0.2 miles of the ravine) is heavily affected by channel scour and lateral bank sliding. ' Most of the middle portion of the stream is under the control of the Maplewood Homeowners Association, which has worked to protect the area and its habitat. Despite the presence of the dam and the adverse conditions at the SR 169 culvert outfall, the Current and Future Conditions Report does identify Maplewood Creek as one of nine major fish-bearing tributaries along the Lower Mainstem Cedar River. Sockeye use of the creek is limited because of the poor habitat conditions found in the lower reaches. However, coho salmon use the lower 0.4 miles of the creek up to the outlet of the lower sediment retention pond. ' Cutthroat trout, which have been isolated above the sediment ponds, thrive in the ravine above the dams up to about RM 1.0. Hydrology and Flooding Both the City of Renton Draft Maplewood Creek Basin Plan (Parametrix, 1989) and the Lower Cedar River Current and Future Conditions Report (King County, 1993) used hydrologic models to estimate expected peak discharges from the basin for various storm events. The results presented in these reports are summarized in the table below: tMaplewood Creek Flooding and Habitat Improvement Projects Page 3 WPC\95PROA7163G\FLOODHAB.DOC\01/23/96\9:03 AM\SDC Project Description for Corps Permit Application Expected Maplewood Creek Peak Discharges Based on Modeling Results ' Storm Event Recurrence Maplewood Creek Basin Plan Current and Future Conditions Interval (Yr) (HEC-1) Report (HSPF, 15 min. data) Current Future Current Future 2 118 173 59 132 10 202 275 104 207 25 251 333 135 257 100 300 392 197 349 The capacity of the golf course channel to convey Maplewood Creek flood flows to the Cedar River is limited by the size of the channel and the capacity of the downstream culvert system under SR 169. Sections of the existing golf course channel reach bankful capacity at 150(±) cfs. This is far less than the expected 100-year peak flow, estimated to be 200-300 cfs for existing land use conditions and 350-400 cfs for future conditions. As shown in the table above, most estimates of the expected peak flows predict that channel capacity will be exceeded with the 10-year event under existing land use conditions, and as frequently as the 2- year event under future conditions. Existing capacity of the downstream culvert system under tSR 169 is also approximately 150 cfs, but with flooding of the Cedar River, the capacity of this system is probably reduced to about 100 cfs due to high tailwater conditions at the culvert outfall. Capacity of the system is further reduced by a combination of two factors: sedimentation and the presence of baffles installed in the 72-inch highway culvert to facilitate upstream fish passage. Large amounts of sediment from the ravine routinely escape the ' existing sediment ponds and settle in the golf course channel. Sediment has reduced the channel's slope and cross-sectional area, resulting in a reduction of the channel's conveyance 1 capacity. Baffles in the 72-inch pipe reduce the pipe's capacity by reducing the cross-sectional area. The baffles also collect sediment. Due to flow resistance and sediment storage, the baffles have reduced the culvert's peak flow capacity significantly below its potential maximum. Flow reductions in the culvert also reduce flow velocities in the channel upstream and therefore encourage additional sediment deposition within the golf course reach. Relationship of the Proposals to Recent Planning Efforts Both the City of Renton Maplewood Creek Basin Plan (Parametrix, 1989) and the Draft Lower Cedar River Basin Plan (King County, 1995) include recommendations for stormwater Maplewood Creek Flooding and Habitat Improvement Projects Page 4 WPC\95PROJ17163G\FLOODHAB.DOC\01R3/96\9:03 AWSDC Project Description for Corps Permit Application conveyance and sediment mitigation projects to improve flooding, sedimentation conditions, and fish habitat across the golf course. Both plans recommend reconstruction of the sediment ponds in combination with other improvements to stabilize the ravine. Both plans also recommend increasing the capacity of the channel across the golf course and the downstream culvert to reduce flooding. The Draft Lower Cedar River Basin Plan specifically proposes both the sediment pond reconstruction project and habitat improvements associated with the ' proposed low-flow fish passage channel. As discussed in the Basin Plan: ' "The improved sediment pond and stabilized stream banks would not only allow anadromous fish to pass to upstream reaches, it would reduce the frequency of sediment removal with its associated costs and habitat impacts. Enhancement of the reach within the golf course (RM 0.2 - 0.4) would encourage the use of the relatively good habitat of the Maplewood ravine by anadromous salmonids," The need for these projects was also addressed when the Washington State Department of Transportation (WSDOT) proposed widening of the highway and concurrent improvement ' of the Maplewood Creek culvert system (completed in 1995). The City of Renton asked WSDOT at that time to upgrade the culvert system under the highway to relieve flooding 1 across the golf course. WSDOT proposed to remove the 4 inch x 4 inch timber baffles from the culvert, which could increase capacity of the culvert system to as much as 370 cfs (assuming no tailwater). In order to mitigate for impaired fish passage through the culvert, WSDOT proposed and built a fish ladder under SR 169. In turn, the City of Renton ' committed to build a low-flow fish passage channel across the golf course to connect the fish ladder with the City's planned sediment pond improvements above the Golf course. WSDOT has agreed not to remove the baffles from the culvert until the City's low-flow channel is ' completed. III. Project Descriptions I As introduced above, the proposal consists of three separate projects: the Maplewood Creek Low-Flow Fish Passage Channel Project, the Maplewood Creek Sedimentation Basin Reconstruction and Improvement Project, and the Maplewood Creek High Flow Capacity tImprovements. The projects are described in more detail below and are shown schematically on Figure 2a. r Maplewood Creek Flooding and Habitat Improvement Projects Page 5 WPC\95PROJ\71630\FLOODHAB.D000I/23/96\9:03 AM\SDC 1 Project Description for Corps Permit Application Low-Flow Fish Passage Channel Project Introduction The proposed fish passage channel will extend from the downstream end of the proposed sediment pond (RM. 0.4), across the Maplewood Golf Course, to the existing (but unused) fish ladder that was constructed by WSDOT under SR 169 (RM 0.0)(Figure 2a). The outfall of the fish ladder would also be established as RM 0.0 because the low-flow channel to the fish ladder would bypass the existing 900-foot culvert. The project will improve habitat ' along the reach of the creek through the Maplewood Golf Course and, in combination with the improved sediment pond, will allow fish passage above the sediment pond for the first time since the 1930s. Additional engineering design information for this project is contained in the Draft Nlaplewood Creek Fish Passage Channel Riparian and Instream Habitat Report (Harza ' NW, 1995) (copy included with Corps permit application.) Information on the types of vegetation to be affected is provided in the enclosed Wetland Delineation Report. Proposed Project Elements iSpecific project elements include the following: • Excavation of an 1850 foot channel across the golf course. Maplewood Creek low flows would be diverted into the channel at the outlet of the sediment pond. The new channel would replace the existing channel for conveyance of low flows. The new channel will be shaped to provide a narrow baseflow channel within a broader trapezoidal channel (see Figure 3b). The overall channel will be sized to convey the design flow, with 1 to 2 feet of freeboard. The bottom of the channel will be lined 1 - 2 feet deep with a gravel/cobble matrix. The shape and specific location of the narrow baseflow channel will be determined by flow dynamics through the channel and the placement of in-stream habitat features, described below. • Installation of an impervious clay or geomembrane barrier under the channel. • An impervious liner would be installed below the creek to prevent exfiltration loss of water from the creek into the alluvial soil matrix underlying the golf course. The liner will ensure that adequate baseflow remains in the channel to preserve fish habitat and allow passage through the reach. Maplewood Creek Flooding and Habitat Improvement Projects Page 6 WPC\95PROJV 163G\FLOODHAB.DOC\OU23/96\9:03 AWSDC Project Description for Corps Permit Application • Placement of instream habitat features such as drop-logs, boulders, large woody debris (LWD), and spawning-suitable gravels. Habitat features will be included in the channel to provide cover and a diverse hydraulic environment. Logs and ' boulders will be used to form pools and, in certain locations, to avoid detrimental scour of channel banks. • Planting of vegetation in the channel that can both provide habitat structure for fish and an aesthetic complement to existing golf course landscaping. Construction of the proposed low-flow channel would not affect wetlands, but would convert approximately one acre of uplands that are now maintained as fairways, tees, greens, and cart paths to 0.34 acres of perennial stream and 0.68 ' acres of palustrine shrub wetland (see Figures 3a, 3b, and the enclosed wetland delineation report). In addition to improving flow capacity and maintaining appropriate depth and flow conditions for fish, the channel cross-sections are designed to allow for creation of palustrine shrub wetland. Species selected for planting include willow, dogwood, spiraea, twinberry, mock orange, Pacific ninebark and vine maple, located at appropriate elevations above the ordinary high water line. Overhanging vegetation will be included on channel banks to iprovide additional cover and aesthetic benefit. • Inclusion offish ladders in steep reaches below the proposed sediment pond. The fish ladders will facilitate movement of fish into and above the sediment pond. In stream reaches of 4-6 percent, this will be accomplished with drop logs and ' plunge pools. Just downstream of the sediment pond a concrete structure may be used to raise the creek above existing grades. Construction of the low-flow channel would produce an 1,850-foot sinuous channel with gravel substrate, significant vegetation and in-channel structure, stable banks, and ' sufficient capacity to pass the design flow (45 cfs) without flooding. ' The channel would be constructed using three standardized sections (see Figures 3a and 3b). Section A, for steep sections of the channel with an average slope of between 3 percent and 10 percent, would be of trapezoidal cross-section and would be an average of 20 feet wide, 4 feet deep, and have a 4-foot bottom width. Section B, for sections of the channel with average slopes of between 0.5 percent and 3 percent, would have a benched section with an overall width of about 26 feet, a low bottom width of 4 feet, a benched width of about 16 feet, and an overall depth of about 6 feet. Section C would be used at crossings of the golf course ' fairways. Section C would utilize half-sections of 4-foot diameter pipe. Steeper sections of ' Maplewood Creek Flooding and Habitat Improvement Projects Page 7 WPC\95PROl\7163G\FL(x)DHAB.DOC\01/23/96\9:03 AM\SDC f Corps Permit Co s or tion Project Description Application J PP the channel would use to drop structures to create pools and stabilize th g p p e channel substrate. All sections of the channel would utilize 12- to 24-inch boulders, large woody debris (LWD), 3 to 6 inch cobbles, and 1 to 2 inch gravel to provide instream structure and suitable substrate for salmonids. Flow conditions in the reach will be favorable for fish passage, spawning, and rearing. ' Flow velocities in the channel will vary between 0.15 fps at extreme low flow (1 cfs) to 4 fps at the maximum design flow (45 cfs). Flow depths will vary between 1 foot and 3 feet. (Note ' that these values represent average conditions, with areas of faster flow and slower flow). In- channel structures such as log weirs, boulders, and large woody debris will create complex flow conditions in the channel. With such features, and a moveable substrate, eddies, pools, riffles, and chutes, will be formed, especially in low to moderate flow conditions. Flow velocities during peak events should be sufficient to transport finer sediments through the channel reach and/or scour a large proportion of accumulated fine sediments from the gravel substrates. The channel would be constructed using an clay or geomembrane liner to prevent loss of baseflows into the sand and gravel aquifer that underlies the golf course. The top edge of the channel bank would be bermed to provide a 2 percent minimum slope away from the channel to reduce the potential for fertilizer or pesticide residues that maybe present from recent applications on golf course areas from entering the channel in stormwater runoff. Channel side slopes will be 2:1 minimum. Vegetation will be selected for the channel banks to ' provide shade and structural cover and to minimize required maintenance. Areas requiring ground cover will be hydroseeded with a mix of native seeds and wild flowers. Impacts Due to Construction No significant adverse impacts are anticipated due to construction. Creation of the new fish passage channel will provide mitigation for wetland impacts to the existing high flow channel and sedimentation basins, at an acreage compensation ratio of over 3:1. Construction of the low-flow channel is scheduled to occur in the spring or early summer. All construction areas will be isolated from Maplewood Creek and the Cedar River. No flows from Maplewood Creek will be diverted into the low-flow channel until construction is completed and disturbed areas have been stabilized. BMPs and erosion control techniques as described in the KCSWDM (silt fences, hay bales, etc.) will be implemented in order to prevent the generation and transport of turbidity to offsite or downstream areas. Connection of the low- ' ' Maplewood Creek Flooding and Habitat Improvement Projects Page 8 WPC`,95PRO1\7163G\FLOODHAB.DOC\0123/96\9:40 AM\SDC Project f Description or Corps Permit p p Application flow channel to Maplewood Creek and the Cedar Riv er would not occur until after the new sediment basin is completed Construction of the low-flow channel would require the excavation of up to 8,000 cubic yards of material from upland area on the golf course. Material that would not meet the specifications for the sediment pond berm fill would be hauled to an off-site location for ' proper disposal. Up to 1,600 cubic yards of bentonite clay (for the impervious liner) and 400 cubic yards of select cobble and gravels (for channel habitat substrate) would be imported to the site for the project. In total, about one acre would be disturbed by the construction and grading activity associated with the low-flow channel. ' Future Maintenance Minimal channel maintenance is expected to be required in the future. Vegetation may have to be pruned, the channel will require monitoring for scour and deposition of sediments, ' and removal of undesirable materials such as litter. Sedimentation Basin Reconstruction and Improvements Project Introduction ' The two existing ponds on lower Maplewood Creek within the golf course are owned by the City of Renton and maintained by the City of Renton Parks Department. The upper pond was an old 1930s irrigation diversion, built to support the original orchard which preceded construction of the golf course. The newer pond, located downstream and closer to ' the municipal golf course, was built for sediment control. However, the two ponds working together have proven to be inadequate for this purpose. In addition, the stability of the upper ' concrete dam is a concern. The facility has been damaged by floods, which have undermined the existing dam structures. Till embankments (60 to 70% slope) adjacent to the ponds are ' also a problem, as they slough into the ponds when undercut by storm flows. Reconstruction of the lower sediment pond qualified for FEMA Hazard Mitigation Grant Funds. Fifty percent of the sediment pond reconstruction costs will be funded by FEMA (Federal Emergency Management Agency), 25 percent by WDCTED (Washington Department of Community, Trade, and Economic Development) and 25 percent by the City of Renton. ' The project reach for sediment and reconstruction would be the area of the existing P J P g ' sediment ponds between RM 0.4 and 0.5 (see Figure 5). The lower dam will be replaced by a ' Maplewood Creek Flooding and Habitat Improvement Projects Page 9 WPC\95PROI\7163G\fLOODFIAB.DOC\01/23/96\9:03 AWSM' Project Description for Corps Permit Application flood diversion structure and fish ladder. This project is described in detail in the Maplewood ' Creek Sedimentation Basin Reconstruction and Improvement Project Phase I Design Report (Harza Northwest, 1994) (copy included with Corps permit application). In general, the ' project would include excavation and replacement of a total of up to 7,000 cubic yards of materials. This includes removal of accumulated sediments from behind the upper concrete dam, stabilization of slopes adjacent to the creek, and the removal and reconstruction of the retaining berm for the sediment pond. The enclosed Wetland Delineation Report provides more detailed information on the types of vegetation to be affected by this work. As noted ' previously, wetlands in these areas do not meet the City's definition of wetlands, because they are maintained for the purposes of stormwater management. Proposed Project Elements The proposed project involves reconstructing and improving the existing sedimentation ponds on Maplewood Creek near the golf course. This reconstruction will create a larger ' storage volume for sediment and debris. Enlargement of the pond, together with the construction of new outlet controls, will enable the facility to trap fine-grained sediments. The new basin will have a sediment storage capacity nearly three times that of the existing facility. The existing access road running along the west side of the basin and creek will be improved with a new gravel road surface. It is anticipated that up to 1,000 cubic yards of material would be removed from behind the upper concrete dam. A majority of the concrete dam would be removed (notched) after the sediments have been removed. A sill will be established in the old dam about a foot below the proposed stream grade. The notch will be 10 feet wide at the bottom. The sides of the notch will extend up to the top of the dam at a 1:1 (45 degree) angle. Stabilization of potentially unstable slopes adjacent to the upper concrete dam would require excavation of about 250 cubic yards of material from the toe of the slopes. The excavated material would be replaced with about 200 cubic yards of specialized fill, such as 12- to 30-inch rock and or riprap. Special fill material would come from special off-site ' quarry sources. Construction of the new sedimentation basin would involve excavation of up to 3,500 ' cubic yards of material from the existing sediment pond and the northernmost portion of a parking lot which exists immediately south of the pond. Approximately 3,000 cubic yards of ' material would then be placed for the downstream berm to contain the reconstructed sediment ' Maplewood Creek Flooding and Habitat Improvement Projects Page 10 WP095PROJ\7163G\FLOODHAB.DOC\OI123/96\9:03 AM\SDC Project Description for Corps Permit Application basin. Portions of the previously excavated material which meets the design specification for the berm fill would be reused. The remaining fill, would be imported to the site. Excavated material which cannot be reused for reconstruction of the pond would either be used on the site for golf course landscaping, or hauled to an off-site location for proper disposal. After construction, the sedimentation basin would have sufficient storage capacity to hold the total sediment load that would be expected to be delivered to the facility over a 1-year period. Vegetation that will be affected by slope stabilization activities at the upper concrete dam is primarily swordfern and Himalayan blackberry. A few small-diameter (2 to 6 inch) alder and western hemlock trees may be removed. The area that would be disturbed includes approximately 0.06 acres on the east bank, where the slope will be graded back and stabilized with rip-rap. An area just downstream of the existing dam will be treated similarly, affecting 0.04 acres of upland vegetation. Herbaceous wetland vegetation that has established on ' recently deposited sands and gravels in the pond will be removed. Vegetation that will be affected at the lower sediment pond includes upland shrub and fern species on the east bank (primarily Himalayan blackberry and swordfern); herbaceous ' wetland species on recently deposited silt, sands, and gravels within the ordinary high water mark (reed canary grass and creeping buttercup); and a mix of upland and wetland plants on the dike (common and giant horsetail, thistle, mullein, dandelion, clovers, hairy cat's ear). A rfew small-diameter (2 to 6 inch) alder, Douglas fir and western hemlock trees may be removed during construction of the new fishway abutment. The total area disturbed is expected to be ' approximately 0.16 acres, which includes upland forbs and grasses along the access road and paved parking area. Native and native hybrid shrub species are proposed for landscaping, with a grass/wildflower mix for erosion control. Two small slide areas (one on the east bank of the upper concrete dam and one just downstream of the dam) would be repaired using rip-rap joint-planted with willow and dogwood cuttings to improve stability and provide palustrine shrub wetland. The west and south margins of the expanded lower sediment pond would also be planted with willow and dogwood cuttings, and rooted stock of Pacific ninebark and Nootka ' rose at higher elevations. Gradual slopes at the upper end of the pond on the west bank will allow for planting of emergent wetland species in shallow water and saturated soils. A mix of burreed, rush and sedges are proposed for a small area that would be affected by construction ' of the maintenance ramp into the pond. tMaplewood Creek Flooding and Habitat Improvement Projects Page 11 WpC95pROJ\7163G\FLOODHAB.DOC',01/23/96\9-03 AM\SDC Project Description for Corps Permit Application Specific features of the new sediment :basin would include the following: g • Reconstruction and expansion of the existing sedimentation basin with an outflow weir to provide for fish passage (Figures 4a and 4b). The new basin will have a pool surface area of approximately 12,000 square feet and a volume of 1,300 cubic yards. It is expected to capture a larger portion of fine sand, and trap ' efficiency should increase from an existing 25 percent to 50 percent, or 600 cubic yards. The pond and channel construction may involve up to 4,000 cubic yards ' (CY) of excavation and recompacted fill. • Construction of a rectangular bathtub overflow spillway (Figure 5), a 24-foot long by 12-foot-wide reinforced concrete structure. It is estimated that the frequency of water flowing over the main spillway will be approximately 7 days ' per year on average, primarily during the winter high flow months. A concrete outlet pipe, 30 feet long and 72 inches in diameter will be connected to the spillway. Excessive hydraulic energy of the flows will be dissipated within the ' spillway, pipe and outlet structural system. • Construction of a fishway outlet on the west side of the sedimentation basin ' embankment (Figure 6). This structure would direct water to the future low-flow fish passage channel. Two concrete weirs would be connected by a 32-foot-long by 42-inch-diameter concrete pipe buried under the dam embankment. • Construction of a maintenance bypass pipe (300 feet long by 12 inches diameter), ' including a small inlet and gate structure, will be buried along the west side of the sedimentation basin and access road. This bypass pipe will be used to ' temporarily divert water from the sedimentation basin when sediment is being removed from the basin for maintenance purposes. Sediment removal may take one to two weeks during the summer. This bypass pipe may also be used to divert flows around the pond during the reconstruction work. • Notching of the existing upstream concrete dam 500 feet upstream of the lower sedimentation pond, and removal of accumulated sediments upstream of this dam. The banks along this stretch, 60 feet from the dam, will be secured by riprap. These improvements will facilitate anadromous fish passage into the upper creek area. Fish passage is now prevented by the dam. Maplewood Creek Flooding and Habitat Improvement Projects Page 12 WPC\95PROJ\7163G\FLOODHAB.DOC\OI/23/96\9:03 AM\SDC Project Description for Corps Permit Application • Improvement of the existing access road along the west side of the existing sediment pond. The 10- to 12-foot wide roadway will be stabilized and then resurfaced with crushed rock. Impacts Due to Construction ' Although wetlands in the sediment pond areas do not meet the City's definition of wetlands, mitigation will be needed to meet Corps. requirements. Notching and excavation behind the upstream dam will affect 0.05 acres of recently-developed palustrine emergent wetland and 0.02 acres of perennial stream. After construction, approximately 0.06 acres of palustrine shrub will be planted to help stabilize the bank on the east side of the pond. Improvement of the lower sediment pond will involve excavation of 0.06 acres of existing pond, and removal of 0.03 acres of palustrine emergent vegetation. These losses will be compensated by expansion of the pond to 0.28 acres of open water, with 0.07 acres of palustrine emergent and palustrine shrub plantings. ' Reconstruction of the sediment pond would probably occur in the late summer or early fall fisheries construction window. Expansion of the pond would affect minimal upland area, an existing access road to the west and an existing parking lot to the south. During construction, all flows would be routed around the area where work is taking place. BMPs and erosion control techniques as described in the KCSWDM (silt fences, haybales, etc.) will be implemented in order to prevent erosion-induced sediment generation and transport to ' downstream areas. ' Future Maintenance The new basin will trap particles coarser than about 0.1 to 0.2 mm diameter. It is estimated that the trap efficiency of the new basin will increase to 40 to 50 percent and will trap 500 to 600 cubic yards of sediment annually. Based on the proposed basin configuration, the trapped sediments should consist primarily of gravel and sand which will be readily dewatered. Small amounts of coarse silt and clay (less than 10 percent) should have no real effect on large scale dewatering. • In order to retain the optimum settling characteristics in the basin, at least 2 feet of ' water depth should be provided for settling during high flow events when the basin pool level reaches the proposed spillway crest at El. 109. This means that the basin floor should be deeper than 107 feet at all times. If the basin is designed with a bottom elevation of 105 feet, Maplewood Creek Flooding and Habitat Improvement Projects Page 13 WPC\95PRGJ\7163G\FLOODHAB.DOC\01231%k9:03 AM\SDC Project Description for Corps Permit Application this will allow 600 CY of the total 1,300 CY to act as sediment storage volume and will require cleaning on an average of once a year. If less frequent cleaning is desired, the bottom elevation could be cleaned to 104 feet to provide a total of 900 CY of storage. (Note: all of the 1,300 cubic feet of available storage would not be used so that some amount of freeboard is maintained). As with the present basin, depending upon the storm frequency and intensity, the basin may need to be cleaned after a single large storm, or may not require cleaning for several years if there are no high flow events. The City will coordinate the timing of maintenance activities with WDFW so that impacts on fish would be avoided or minimized, much as it does ' under current conditions. Maplewood Creek High-Flow Capacity Improvements Introduction High Flow Capacity Improvements are not currently scheduled for construction, but are included as part of the overall plan for improvements to the system. The High Flow Improvements may be constructed in the future when funds are available. The proposed high- flow capacity improvements would extend from the outlet of the reconstructed sediment basin ' to the inlet of the existing culvert system under SR 169 (that portion of the existing Maplewood Creek channel between RM 0.1 and 0.4). The improvements would provide sufficient capacity to convey flows greater than baseflow (> 20 cfs) up to the anticipated 100- year storm event flow (392 cfs) with freeboard. The high-flow channel would be designed to ' convey storm-related flows across the golf course to the Cedar River. In general, the alignment of the high flow capacity improvements would be the same as ' that of the existing creek channel (see Figure 7). The channel will be widened to handle higher flows with 1 to 2 feet of freeboard. Currently, the channel width varies between ' approximately 12 feet and 18 feet. The proposed improvements will result in widening the upper end of the channel from approximately 12 feet to approximately 24 feet. The width will ' increase from approximately 18 feet to approximately 40 feet at the lower end, where it might be combined with the golf course fairway. The width of the middle section of the channel will increase from approximately 18 feet wide to approximately 34 feet wide. Side-slopes along ' the entire channel would be sloped a minimum of 3:1. Overall, grading and earth moving to widen the channel would affect up to 1 acre of the golf course and require the handling of up ' to 3,000 cubic yards of material. All materials would either be disposed of on-site as part of ' Maplewood Creek Flooding and Habitat Improvement Projects Page 14 WPC\95PROJ\7163G\FLOODIfAB.DO('\01/23/96\9 03 AWSDC ' Project Description Application J Ption for Corps P Permit PP ongoing landscaping activitie s at the golf course or removed by the contractor to a commercial disposal site.. Vegetation along the creek that would be removed due to construction is currently affected by regular maintenance (mowing), the addition of quarry spalls to stabilize sloughing banks, and scouring and deposition of sediments during flood events. Within the riparian zone, Himalayan blackberry, reed canary grass, turf grasses, creeping buttercup and smartweed predominate, with scattered soft rush and small-fruited bulrush, and a few alder seedlings and saplings. (Photos of portions of the existing Maplewood Creek Channel are included in the Wetland Delineation Report submitted with the Corps permit application.) Approximately 0.17 acres of wetland vegetation and no more than 0.69 acres of adjacent ' upland (existing golf course features, such as fairways and cart paths) would be affected by construction of the high-flow channel. The high-flow channel would be graded and landscaped to be consistent with golf course fairway areas. Side slopes would be gradual, allowing easy maintenance such as mowing. Impacts Due to Construction Diversion of water and recontouring of the existing channelized creek will affect approximately 0.09 acres of perennial stream and 0.17 acres of disturbed palustrine emergent wetlands. These impacts will be compensated by creation of the new low-flow channel, including approximately 0.34 acres of perennial stream, and 0.68 acres of palustrine shrub ' wetland. Construction of the high-flow channel would probably occur in the late summer or early fall fisheries construction window, when no water would be flowing through the high ' flow channel. BMPs and erosion control techniques as described in the KCSWDM (silt fences, haybales, etc.) will be implemented in order to prevent the generation and transport of turbidity to downstream areas. Future Maintenance Minimal maintenance is expected to be required for the channel. Vegetation may have to be pruned, and the channel will require monitoring for scour and deposition of sediments, and removal of undesirable materials such as litter. ' Maplewood Creek Flooding and Habitat Improvement Projects Page 15 WPC\95PROJ\7163G\FLOODHAB.DOC\01/23/96\9:03 AM\SDC ' Project Description for Corps Permit Application ' IV. Benefits The projects discussed herein would work together to increase the capacity of the Maplewood Creek drainage system across the golf course, to prevent flooding and reduce ' related property damage and maintenance costs, while also mitigating existing adverse sediment transport conditions and providing higher quality habitat for use by anadromous fish. The low-flow channel would permanently convey Maplewood Creek low flows to the Cedar River and allow upstream fish migration past the existing 900-foot SR 169 culvert via the WSDOT fish ladder. It would also create approximately 0.68 acres of palustrine shrub ' wetland, providing new forage cover and nesting habitat for songbirds, small mammals, reptiles and amphibians. Capacity of the low-flow channel would be limited to about 45 cfs ' (the maximum flow capacity of the fish ladder). Flows into the low- and high-flow channels would be regulated by improved weir outlet structures from the new sedimentation basin. The new outlet structures would be designed to enable the reconstructed sediment basin to capture and store a much higher portion of the ' suspended and bedload sediment from the creek than can be handled by the existing facility. By preventing more sediment from reaching the downstream channels, habitat and conveyance ' capacity along those reaches would be preserved. Sediment pond reconstruction would also stabilize the failing slopes south of the pond and reduce a source of sediment input at that ' location. The capacity of the existing Maplewood Creek channel would be increased to accept ' higher flows of up to 392 cfs through the proposed high-flow capacity improvements. However, flows would be directed down the high-flow channel only during storm events. V. Impacts ' The projects would affect approximately 0.42 acres of wetlands. The projects would compensate for this impact by creating approximately 1.45 acres of wetlands with higher values than currently exist, at a compensation ratio of over 3:1. It is anticipated that the proposed mitigation, which will be initiated on-site, will be adequate to satisfy Corps ' requirements. Construction of the projects would be sequenced to avoid adverse impacts to fisheries resources in Maplewood Creek and the Cedar River, and to take advantage of ' seasonal reductions in golf course play. The low-flow channel would be built entirely in upland area that is currently part of the ' golf course. The low-flow channel would connect to the existing fish ladder on the north side ' Maplewood Creek Flooding and Habitat Improvement Projects Page 16 WPC\95PROI\7163G\FL(3UDHAB.DOC\0123i96\9:03 AWSDC Project Description for Corps Permit Application of SR 169 and to the new sedimentation basin via a second m s aller fish ladder to be located ' on the south side of the new basin. Construction of the fish passage channel may occur in the spring or early summer of 1996. Proper erosion and sedimentation controls would be ' provided to prevent the discharge of eroded sediments to either Maplewood Creek or to the Cedar River from the construction site. (A Shoreline Substantial Development Permit will be required for the proposal because the connection to the fish ladder would be located within 200 ' feet of the Cedar River.) No impact to fisheries or other resources in the Cedar River is expected from this diversion because the outfall of the fish ladder is located within 20 feet of the outfall of the existing SR 169 culvert. Construction of the Sediment Basin Reconstruction and Improvement Project would probably not begin until after June 1996, and would be completed during the fisheries construction window (or other approved time period). During construction Maplewood Creek ' would be diverted around the construction area and would be directed into the existing channel across the golf course. After the new basin is completed, base flow would permanently be ' directed to the low flow passage channel. The Sediment Basin Reconstruction and Improvement and High-Flow Capacity ' Improvement Projects would be constructed within low-quality riparian areas that are adjacent to the existing ponds and the golf course channel. The table below shows the area of each ' type of wetland that would be affected by the project. Effects of the Project on Wetlands ' Type Existing Acres Future Acres Open water 0.06 0.28 ' Perennial stream 0.11 0.36 Palustrine emergent 0.25 0.02 Palustrine shrub 0.00 0.79 Total 0.42 1.45 Existing banks of the sediment pond and lower channel (through the course) are ' currently impacted by regular maintenance activities, by disturbance due to mass-wasting (in the area of steep slopes adjacent to the pond), sediment deposition, scour, and bank sloughing, ' and wetland functions are significantly impaired. Minor expansion of the sediment pond to the west would be into an area that is currently used as an access road along the edge of the existing ponds. Expansion of the pond to the south would be into an existing parking lot. ' Maplewood Creek Flooding and Habitat Improvement Projects Page 17 WPC\95PR01\7163G\FL00DHAB-DOC\01/23/960:03 AM\SDC ' Corps of Engineers Permit Application ' -6 S:(' C}�y/��''y�. Y y 7. St sE'v 0 yNew•me oL ES 4. 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'aft r •N• i C• NE ba a I i n N �' N a _ •' s npnon� Err F3 4 ` < I `4 S 11>Z s 51]95l N 4 s 2? wa•'lrew w•E 3 8 fi ' +r Cww Cww � .,� rv+a ei 1Js' sry a, Sr„y sr S f i 5 R n R MS' H ^ae �6 Ew S IiI� H Y 2 Ore _K 'd > •'drloN U S �` 5- sEi1AA W aT• Rrwon .Ir,n N {.ih� 169 a1+••o„e <_..L 5\ V IJ� Sdr w ' •Y SE p J,SE T}- _` - .+QSi�<f.—.'. S, ' S1eJ Sf F/C `S7M SI N• S< �iVae,l'•o0�� Black,,a 3 GoeE f —_ "fllve I N a `3 G d e«e..cu sE Ids. .�RSnop+gwQ"wwN. PROJECT SITE .�rw -c•,6er ter— ; �� � U � � � 1 'ry' �a�� � A.: �� -A`H 1 ,55, • < °'J p� e � d t ♦ e 't„'E teP J'S' 1 O I s r Wirer r'ew, .sl gVl SW to St Ell, a pp 3S •� �� p A ' :�€ a �r. , , 1.c � Maplewood y �L E ss i; a ,gyp � ••en r a�� 0 , f'`/�' �? sw a .e �� 9 _ 3 U� .' SE•9 QS``�_ --y& p•''1`�"' P� N e, Or SEr, a "y�`z�LONGACRES y r u b , , E we Reerq Irsa s J SI ci \iE reo 51 �' 3 cJacs°e sE'sr r �5� 'rs* C Erewwo °a es <7 rt1 z<• i'67 irG�2•��'s'''"��--aS, s^ `. 1 f �33 'Ns ,E 35�<y sE'6J 9' vu 6 9 Cascade_ ;E .,, 1— ;^M t = , S2t •� l - r655, 5E•66A' SE•5J ( .v�,•"9y` \�.' tI '1 I N ' L i SOURCE: King of the Road Map Service Inc. Bellevue City Map 1 MILE Figure la Project Vicinity Map ' Lower Maplewood Creek Flooding and Habitat Improvement Projects ' Corps of Engineers Permit Application JIL_____� 1 • ■ • .. . .. '• \\ i 406 i 11 1 ■' r ' West Branch 40 • •• •• •• •• • •• • ' 1\ • • ••• •• •so - East Branch \\ •• ••••••.•• • eI A ■ ■ —� U Maplewood Creek �-3Q� • p / . . •_• '•.� Upper Dam . . • ii•.• • • Existing Sedimentation . • - • • - it : •' Basin (RM 0.4) � - \\ 40ij _ • . .. •.. - 10 CEDE Coe . � •`\�� f se - _ _ • C� i1,�. • � o 0 c ' °� \ .• % — o 14 lST A • • . . . //� // FATE RO � A so • • 9 • OT \ /�Q • t • • • // • \ I I 1 N SOURCE: U.S.G.S.RENTON SHEET, 1:24,000 11� Latitude= 122°09'15" 1000, Longitude=47928'06" Figure lb Project Vicinity Map ' Lower Maplewood Creek Flooding and Habitat Improvement Projects t- 1623059126 1623059022 L'—'—''—'--'—•I •—•� COMMON PROPERTY TYPE II (D --•—•— ._.— . K 1623059065 w •_ ' 1523059169 ° /-I UPPER SEDIMENT POND `�-- 5126900280 .'— •— •—• — _) 00 CL �£fT1 1623059018 y 51269OP70 1523059014 rl' (D CD PIT' \ EXISTING CONCRETE DAM TO BE REMOVED ,. EXISTING CONCRETE � DAM TO BE NOTCHED' 5126900355 !, EXISTING SEDIMENT PONOI PTgC 5k2f8A0435 . j F PROPOSED FISH LADDER I � %%' 4 T PROPOSED IMPROVEMENTS \ TO SEDIMENT POND 512700210 Q Fry I ,F. + , - EXISTING TO BEABANDONED) A BPAANROKOINNGE OL) 690040„ 51 2' 70-5 EXISTING CLUBHOUSE 0200/ ./ �.. / ,, ._.____.. (TO BE REMOVED) ^-iT�.,a. —. _ I ._ 1523059088 2223059090 _ fFr r 2123059023 W % 2223059069 —I— ,_' MMON TYPE II r" 2223059008 51 2 6 9 00500 PROPOSED LOW FLOW / \ ` _ LEGEND FISH PASSAGE CHANNEL I 1� :, y 2223059010 TAX PARCEL NUMBER It EXISTING MAPLEWOOD L ;.• $ I r y \\ �f 1 CREEK ALIGNMENT _ = j` •�® 'I♦ ,�a\�. /,' (PROPOSED HIGH FLOW CAPACITY IMPROVEMENTS) y \ ,�. •\, / PROPOSED LOW-FLOW / O 1 .. / \ `•, j:�- I� FISH PASSAGE CHANNEL CIO \�� `—i1y`. \'` a j .�►�« r EXISTING MAPLEWOOD CREEK ' U� EXISTING GOLF COURSE GREENS 0�q \ / 2223059010 f. EXISTING TREES , C-t- ••,`• - J \ r / r ) PROPOSED BRIDGE (TYPICAL) n B EXISTING WSDOT ��G / I EXISTING CONTOURS M PROPOSED RICH-FLOW n FISH LADDER \ / i (2.0 FT INTERVALS) J � •., I--1• F, 1'c:5�' f CAPACITY IMPROVEMENTS F••S 1 NOTE:}- a 300 2223059026 b i -- -- ( SEE FIGURE 2b FOR NAMES, ADDRESSES l s j� \ AND PHONE NUMBERS OF TAXPAYERS/ $cola rsel `(?� \ OWNERS BY PARCEL NUMBER. R Corps of Engineers Permit Application ' NOTE: Parcel locations are shown on Figure 2a. ' Parcel Taxpaper or Owner 1523059088 Beulah E. McCarty 2223059090 4012 Maple Valley Hwy Renton, WA 98055 (206) 255-5519 ' 1523059014 City of Renton 1523059169 Parks Department 1623059065 200 Mill Avenue South ' 2123059023 Renton, WA 98055 2223059010 (206) 277-5549 ' 1623059018 City of Renton 1623059126 Finance Department 200 Mill Avenue South Renton, WA 98055 (206) 235-2558 ' 1623059022 West Coast Management Inc. Sunnydale Mobile Home Park ' 5339 Prospect Road#261 San Jose, CA 95129 2223059026 Burlington Northern Railroad Property Tax Department 777 Main Street#1206 ' Fort Worth, TX 76102 2223059069 Philip Charboneau ' 14636 SE Jones Place Renton, WA 98055 (206) 432-1466 5126900280 A M Rhodes 3624 SE 5th Street Renton, WA 98055 (206) 255-6689 5126900355 Jeffery D. &Dawn M. Van Keulen 3624 SE 5th Place Renton, WA 98055 (206) 255-5384 ' Figure 2b Adjacent Property Ownership Information ' Lower Maplewood Creek Flooding and Habitat Improvement Projects Corps of Engineers Permit Application Parcel Taxpaper or Owner 5126900370 Eileen M. & Timothy A. Bishop 3629 SE 5th Street Renton, WA 98058 ' 5126900410 John H. Sea9 uist 111 SW Victoria Street ' Renton, WA 98005 ' 5126900435 Douglas R. Horvth 512 NE 71st Seattle, WA ' 5126900500 Steven E. &Elaine D. DeForrest 3705 SE 6th Street Renton, WA 98057 5127000200 Lawrence Vickers ' 13419 SE 141 st Renton, WA 98055 (206) 255-7592 5127000210 David M. Yamamoto 13420 SE 141 st Renton, WA 98055 Common Property Type II Liz Menzel, President ' Maplewood Heights Homeowners Assoc. 13803 SE 144th Street ' Renton, WA 98059 SR 169 Washington Department of Transportation Attn: Real Estate Services P.O. Box 47300 Olympia, WA 98504-7300 (360) 705-7000 Figure 2b Adjacent Property Ownership Information ' Lower Maplewood Creek Flooding and Habitat Improvement Projects ' Corps of Engineers Permit Application SetlmenI Pond � I existing wooded slope • , . , G8 Section A F8 T6 F6 • • 1 • ' G3 ' Section • . . . • • • • • . F3 • _._...._�._..___. ...• • • • T4 • • • f4 :_ i ction C ' F G2 2 • Section B ' .. F l .. Section C • • • • • • N •a western tea cedar ❑ tall-growing native CPOvine mope.Oregon grape. 5aat group ❑ low-growing native ° 00' 200 Pacific nk,eaark.mock orange, willow, hybrid s. block tv neberry group ® turf grasses Cart Path ♦Alternate Cart Pam Figure 3a Low-Flow Fish Passage Channel Conceptual Planting Design Plan View Lower Maplewood Creek Flooding and Habitat Improvement Projects ' Corps of Engineers Permit Application ' EX15T.GRADE 20'MIN. SLOPE 27 MIN. SLOPE 2%MIN. TO EX15T.GRADE E-- Z, h TO EXI5T GRADE 4' o 1.0 c--4 --r ' 3"-6"TOPSOIL LOG DROP STRUCTURE &HYDR015EED 3'-6"COBGRAVELBLE R 2"1" IMPERV105 CLAY LINER 12"-24"BOULDE SECTION A 26'MIN. 6' 3' 10'-- 3' 6' EX15T.GRADE SLOPE 2%MIN. SLOPE 2%MIN. TO EX15T.GRADE e--I ! H TO EXIST.GRADE 3' - � 1.0' 3"-6"TOP501L &HYDR05EED ' 12"-24"BOULDER IMPERVIOU5 CLAY LINER 3'-6"COBBLE LWO INSTALLED V-2"GRAVEL IN CHANNEL SECTION 5 ' r--12'MIN. 5LOPE 2%MIN. 5LOPE 2%MIN. ' TO EX15T.GRADE H — H TO EX15T.GRADE 1' ' Y-6"TOP501L&HYDR05EED 1/2 4'PIPE ' SECTION C Figure 3b ' Low-Flow Fish Passage Channel Section Views of Channel Design ' Lower Maplewood Creek Flooding and Habitat Improvement Projects Corps of Engineers Permit Application CL ACCESS ROAD AND 12.0 / 1 12 MIN DAM CREST ADS N-12 BYPASS PIPE BYPASS PIPE INLET EL 111 5 (MIN.PIPE SLOPE IX) / / SEE FIG.8 DOWNSTREAM r / \ 11 S UPSTREAM SIDE /-� SIDE EXISTING ACCESS / n ® // \\© ROAD TO BE IMPROVED \ SEE NOTE 1.FIG, b � _/ T iJ,. / '6 J ALL FILL COMPACTED TO 981L / M., .ORY DENSITY AND ®�COMPACTED FROM OPTIMUM MOISTURE VARIES FILL MATERIALS CONTENT TO PLUS 27L ' TMCAL DAM SECTION ©�LOCALLY DERIVED SCALE: I" IV(MORIZ.AND VERT.) FILL / 0 M B'8 X 75'LC ADS HEAVY DUTY PERFORATED DRAIN " '• / h-/J 11 "'+� / PIPE SEE DETAIL 2•FIG.6 SLOPE TO BE REVEGETATED NTII A MIX OF EROSION CONTROL GRASSES N ! /�'./`6 AND NATIVE SHRUBS(TYP.) - DAM CREST EL 111.5 SEE TYPICAL DAM SECTION ! _ ! ! / / EXISTING 9'0 WOOD PIPE TO BE REMOVED f FISHWAY OUTLET / ! 111. SEE FIG,8 1O'' METAL PIPE TO BE EXISTING •REMOVED f 12-0 ADS N-12 BYPASS PIPE EXISTING 4'0 PVC PIPE TO BE REMOVED J FUTURE `0 CHANNEL$NWA7 / -- ». ` ti 7• N EL OB I / Nf COTTONWOOD BO OM EL 105-0 IRRIGATION ETIONpIINLET STING AND PIPE UPSTREAM OF NEW INLET WA TER { 4 I j1 / j s' •f r' ,xr "" }: m' EXISTING CONCRETE •/ / 3 3 mac. f£ - £r WEIR TO BE REMOVED EXISTING RIPRAP '.�/ �/_ I— -� 11 � EST-:. 'Ff/.,?I' l• , 5`�i�a�?E = = 10 BE REMOVED WAY CR F l' NEW INLET TO EXISTING ! Q'• :5 r ",� ''�.�" i •o IRRIGATION PIPE .! ��t J fi} fir•�' C SPILLWAY AND / 4 ILET SEE FIG.5 APPROXIMATE LOCATION S OF EXISTING IRRIGATION REMOVE E7IS71NG PAVEMENT. / / PIPE SEWER MH•PIPE AND TRENCH TD MATERIAL FROM BASIN AND I 091DR DAM. CUT AND CAP PIPE EXISTING SEDIMENT POND \� EDGE OF EXISTING PA\IBIFHT(TYP. / a ORDINARY HIGH WATER LINE IORDIN ROv HIGH WATER LINE P I" a/ 41 SCALE 0 25 50 FEET I 50' Figure 4a ' Proposed Sedimentation Basin Improvements Site Plan and Sections ' Lower Maplewood Creek Flooding and Habitat Improvement Projects ' Corps of Engineers Permit Application ' CENTER NOTCH SECTION OF UPPER 120'LG SEDIMENTATION ZONE DAM TO BE REMOVED AT REMOVE ACCUMULATED SEDIMENT ELEVATION LEAST TO EL 122.5 OR ONE FOOT PRIOR TD__..5:' B0.0W DOWNSTREAM GRADE OF CREEK SCOUR ZONE BOTTOM A- A 120 LONGITUDINAL PROFILE AT MAPLEWOOD CREEK ACROSS UPPER CONCRETE DAM ' SCALE i' 1' 20'H 710 10'V A 4 MAN ROCK 2{'-30'DIA. t STREAM B 2 MAN ROCK 12'-18'DIA 1•LENGTH OF REPAIR SECTION- 70 FEET CHANNEL LENGTH QF REPAIR SECTION-80 FEET /• TOE OF SLIDE WILL REWIRE-60 4 BEDDING GRAVEL • TOE OF SLOUGH WILL REWIRE 40 MAN ROCK 30 4 MAN ROCK: IS CUBIC YARDS OF CUBIC YARDS OF B — B 2 MAN ROCK; ID CUBIC YARDS OF / 2 MAN ROCK.20 SCALE: 1'-10• CRUSHED ROCK(2-R1CH). / CUBIC YARDS OF CHANNEL / CRUSHED ROCK • MINOR RESHAPING OF UPPER AANN // •CRUSHED. SLOPE AND DISPOSAL OF VEGETATION AND SURFACE RESHAPED SLOPE SOLI. WILL REWIRE EXCAVATION AND DISPOSAL OF 25 C — C CUBIC YARDS OF END Of EXISTING ACCESS SCALE1.-10. VEGETATION AND ROAD TO BE IMPROVED. SURFACE SOILS. SEE NOTE 1 _ A-4 MAN ROCK 24'-30'DIA. -2 MAN ROCK 12-18'DIA SILT TO BE REMOVED BEFORE C-RESHAPE SLOPE REMOVING CONCRETE DAM \�'=��--� Op-REMOVE ACCUMULATED SECTION —=` SEDIMENTS CENTER NOTCH SECTION OF EXISTING CONCRETE DAM TO BE REMOVED.NOTCH SECTION MIN.10'BOTTOM WIDTH AT �' 1y" O i]O FOUAN OR TITLES TATING ESAIARE 45'CUT BOTH SIDES - �.- Q ONLY AND NOT TO BE USED ' �- FOR BIDDING PURPOSES. ' \ / CONTRACTORS MUST BOULDERS OF 2'TO 3' // PREPARE INDEPENDENT SIZE TCPMO BE PLACED ON / QUANTITY ESTIMATES TTo 10..SPACINGBOTTOM(TIP.) // •� \ ___ FROM UPSTREAM END OF THE SEDIMENTATION BASH / � 10. TO 100'UPSTREAM OF THE '- UPPER DAM EDGE OF EXISTING ACCESS ROAD(TYP.) g- O / o .l/ /! u"CECAR���� FIR MEVL3C1 4�r / �0 SCALE 0 25 50 FEET I I NOTE:Rf l i l '6 1' - 50' t. ACCESS ROAD SURFACE TO BE 4' DEEP 7/8' CRUSHED ROCK ROLLED ON A CROWNED EARTH SURFACE FOR A MINIMUM ROAD MOTH 12'. ' 2. ® EXCAVATE TO RESHAPE THE SLOPE. QSLOPE TO IT OVER EXCAVATED, REPLACE WITH ROCKERY AND RIPRAP WITH GRAVEL DRAIN. Figure 4b ' Proposed Sedimentation Basin Improvements Site Plan and Sections (cont.) ' Lower Maplewood Creek Flooding and Habitat Improvement Projects B•EMERGENCT C p DRAIN GATE JOIry7 TO MATCH CM 72.6 PIPE F� . b D II D ----- --------------- } L Q K —= f SPILLWAY 172•0 OUTLET PIPE i L 4 J I 1 4 �• 1'-0•SLOT 1.p Q� 6•SU80RNN F 47 I' GATE PLAN 5 0 00 26'-0' 1 5'-0• 12'-0' G• B•FLAT BACK LIGHT DUTY SLUICE GATE PROMDE TEE 14'-O• HANDLE FOR GATE OPERATION Jy L.111.5 100 YR.FLOOD MAX. E DAM CREST EL. 111.5 DAM CREST EL.111.5 I"1 V POOL EL 110.5 2.5 OSPILLWAY CREST EL.109.0 1 `� VO 2 i i 0 1 El. 107.0 MATCH EEK BED Cw�<D EL 98.5 BASIN BOTTOM EL 105 _ / 2 CREEK BED P r^ EL 90.5 EL. 104.0 CD V/ I 1 p ^n � i j 72•0%30'lG CONCRETE PIPE 1 1 rb Q I ASTM-C-76 CL 11 I EL.97.5 Sv B•o PERFORATED DRAIN r'F PIPE IN GRAVEL FILLED • D D — 1'-0• 7 w. _ E - E R SE0 LON.DET PIPE SLOPE Tom• d RPRAP SECnON CUTTING y ►+ Trn FILTER FABRIC TO BE USED AS A PLANE �-+• MARKERRWC POND CLEAN OUT AS ♦♦��� 3' .) WELL AS A FILTER EL.107.0 VJ lYP BA BOTTOM EL. 105.0 DU • p �'.,y(,-. BACKFILL 'AROUND B6 PPE USING 101.0 H. I•-'u YIf 1 1/2 IN NOMINAL DIAMETER WASHED O Z 0. GRAVEL PERFORATIONS SHOULD BE ON LOWER PART OF PIPE .`� 1.97.5 ►+ '-0•MIN. Q.. ►� SCALE 0 { B 12 FEET In. 171 SEDIMENTA71ON POND SUBDRAIN I I I I I I 1 I G d O (m DETAIL 1 b G NOT TO SCALE F _ F 1•- 12' 1T p.t EXCEPT AS NOTED l7 �. Mom—• CD Lv r� + Uh �. E -- 120 BYPASS PIPE ED - -, , H---1 w II G ------ --------------- g i I _ _ >p.�eTE.err_._._ F FUTURE FIS-4 I CHANNEL g FISHWAY A H OUTLET \o 6 `STAFF GAUGE TO 00 DAM CREST BE INSTALLED 12.0 BYPASS _ 4•-0• PIPE 6. M I 'W DAM CREST EL 111.51 42"A PIPE El.111.5 .. 6- 100 YR.FLOOD MAX SEE DETAIL J '�C 109.5 POOL EL.110.5 r. EL.IGO. -NORYAt.POOL(ORDINARY y INV.EL.107.0 2 .EL 107 5 HIGN WATER LINE)EL.108.5 ti = 441%}]•LCQ CONCR€jE PIPE I EL 101' SEE DETAIL J I ( I 6"FILLET(TYP.) BASIN ROTTOM EL.105.0 BASIN TT 4 MATCH BOTTOM OF 103. -- 0 �Oy FUTURE FISHWAY CHANNEL --- CDI SECTION CUTTING PLANE a ,._p. Tom. o H — H a m ROADWAY F 6•COVER MIN. ►►►yyy� (� �j''�+F��+'-y1', BACK AROUND US ADS N-12 PIPE USING 1 w Ip 1 Il L_1JJ � u r r uwNc �.- cN CRUSHED ROCK. f"f o MpN MIN A YWIYUY pF J6-INCHES Of COVER y 3//B•STAINLESS ►•�• 1'-6• WITH LOCALLY DERIVED FILL,ALIGNMENT. 10 S1FfL PLATES Q 5'-0• _ c � OVER PIPE WITHIN ROADWAY AUGNMENT. W/BEVELS y _ �• WHERE COVER IS LESS THAN 36-INCHES. Yl PLAN ;: 1 q BACKFRl WITH LEAN MIT(-50 LB M +' CEMENT 350 LB FLYASH PER YARD J-6• 3-6- BYPASS PIPE INLET a (WITHIN ROADWAY ALIGNMENT ONLY).En �o N• FINISHED GRADE TYPICAL FISHWAY TYPICAL TOP OF �' p' ►►+�4 12 BYPASS PPE PROVIDE TEE HANDLE BYPASS PIPE 6 BED MIN. WEIR ELEVATION FISHWAY WEIR jJ MIN.SLOPE 1% FOR GATE OPERATION SCALE: I"- 3'-0' y TYPICAL DETAIL 2 EEL.1TWG5GRADE N.T.S. DETAIL 3 C 12'FLAT BACK I.E.113.5 ►+ C EIGHT DUTYEL.113.0 w. a ♦�1 Oil SCALE GATE \ SCALE 0 4 8 I[ It,I CD F� r- tr � CD I-o 1CD 'F J — J EXCEPT AS NOTED - Corps of Engineers Permit Application PROPOSED FISH LADDER F BEGIN PROJECT AT OUTFALL OF ! RECONSTRUCTED SEDIMENT POND ! - l 2. �J71, WS ! S(AS gND) _ �� i• 9' Ifi' g' >y ` ! 3, )Ubl :a7 WIND so F115N OR atals t� J a 150 0 150 Scale in Feet ' END PROJECT ' Figure 7 Proposed Improvements to Existing Creek Channel Plan and Sections Lower Maplewood Creek Flooding and Habitat Improvement Projects 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1