Recommended basin plans were formulated based on the analysis results discussed in Chapter 4. The narrative plans are presented by geographic region: Northwest, Northeast, Central, Southwest, and Southeast.  They include both the recommendations and specific steps that should be undertaken next.  The summary table (Table 5-1), at the end of this chapter, contains brief descriptions and costs of all of the recommendations for the study area.

• Northwest Region
• Northeast Region
• Central Region
• Southwest Region
• Southeast Region

The Northwest Region lies outside of the Florence city limits.  It is made up of largely residential neighborhoods south of Heceta Beach Road.  The region is characterized by small, rolling dunes ending in steep bluffs overlooking the North Jetty Recreation Area and Heceta Beach.  Stormwater flows generally east to west in this area.

Recommendations

The main objective in this neighborhood is to protect private and public property in both the
immediate area of the flooding and along the downstream conveyance route.  Recommendations for the NW-A project show in Figure 5-1 include the following steps.  Pumping out of the Gullsettle Court area will be required for the long-term solution.  (It is not the City of Florence’s responsibility to design and construct a pump station in this area.  The 12-inch-diameter culvert under Rhododendron should be replaced with a 21-inch pipe extended upstream to connect directly to the two incoming 12-inch pipes.  This improvement would lessen maintenance problems and increase hydraulic capacity by eliminating the short ditch segment.  The ditch, which leads west from Rhododendron along the North Jetty Road, needs to be improved.  It should also be extended to the west.  A pipe will be required at the west end of the ditch to provide a positive grade to the edge and down the face of the bluffs.  A flow dissipater (large riprap) should be placed at the bottom end of this pipe to minimize erosion.

Table 5-1 lists the details of the improvements recommended for the Northwest Region conveyance system.  The capital cost of Project NW-A is estimated at $******.  The City of Florence cannot complete these improvements since the study area lies outside of the city limits.  The City recommends that the improvements be made through a cooperative effort involving the local developers, neighborhood associations, individual homeowners, and Lane County representatives.

Next Steps

Planning is under way to devello0p a large parcel of property south of Saltaire Street within the next few years.  The developer needs to work with Lane County and the City of Florence to determine where to discharge the resulting runoff in order to ensure compatibility with an overall plan for the area.

The Northeast Region covers an area extending from north of Munsel Lake Road to south of
Florentine Estates and from the ridge just to the west of Highway 101 to Munsel Creek to the east.  Its southern boundary is at approximately 32nd Street.  The area contains the residential development of Florentine Estates, an auto salvage yard north of Munsel Lake Road, and undeveloped property north of the salvage yard and west of Florentine Estates.

Most of the area north of Munsel Lake Road drains to the southwest, where it enters the northwest corner of Florentine Estates.  It flows through a combination of ponds and pipes through the Florentine Estates development and joins Munsel Creek near 45th Court.

Recommendations

Recommendations for the Northeast Region include three projects, as show in Figure 5-2.  The first, NE-A, is to create a vegetated swale along the north side of Munsel Lake Road to divert flows to the east.  The diversion route would limit flows through the existing undersized system in Florentine Estates.  Because of the topography, the swale cannot extend all the way to Munsel Creek but must be routed south along the eastern edge of Florentine Estates.  This improvement will require a 36-inch-diameter culvert under the road.  Because of cost and habitat considerations, it is recommended that the flows be conveyed in an open channel as far as possible toward Munsel Creek.  A pipe will be required along this route near the junction with Munsel Creek because of higher elevations near the creek.  It is estimated that a 36-inch-diameter pipe will be required.

The second project, NE-B, involves several steps.  The first step is to survey the two Spruce Street culverts to confirm their negative slope.  Then, the area should be monitored to determine if problems develop as upstream development occurs.  Replacement of the existing culvert is not recommended at this time unless problems are reported or unless the culvert replacements are undertaken as part of a future infrastructure project.

The third project, NE-C, is an extension of the conveyance improvements of NE-A to allow
development of privately owned land to the north of Munsel Lake Road.  This recommendation calls for the construction of over 1,300 feet of open channel.  Construction of NE-A must precede NE-C; otherwise, the NE-C improvement may increase the potential for flooding in Florentine Estates.

Projects NE-D and NE-E provide a stormwater conveyance system to the commercial area along U.S. Highway 101.  NE-D would run parallel to both sides of the highway and drain into the existing system near the east end of 42nd Street.  Project NE-B is located downstream of NE-D and is required to be completed prior to NE-D.  Project NE-E would serve the area to the north of the intersection of Munsel Lake Road with U.S. Highway 1201.  NE-E is shown in Figure 5-2 to tie-in to the NE-C improvements.  As a result, the NE-C improvement must be completed prior to the NE-E project.

Table 5-1 lists the details of the improvements recommended for the Northeast Region conveyance system.  The estimated capital costs are $****** for Project NE-A, $****** for Project NE-B, and $****** for Project NE-C.

Next Steps

The importance of preserving existing wetland storage capacity in the undeveloped areas to the north of Munsel Lake Road should be emphasized.  This will help lessen future flooding problems, improve water quality in Munsel Creek, provide aquatic and wildlife habitat, and provide a source of high quality water as recharge to the aquifer.

The preservation and possible enhancement of the natural area along the west edge of Florentine should be considered.  Although the larger flows will be diverted east along Munsel Lake Road, maintaining a low base flow through this natural area is important for preserving its habitat and natural resources.

The Central Region extends from 32nd Street to approximately the city limits to the north and is bounded to the east by the ridge of dunes just west of Highway 101.  It contains large expanses of undeveloped property to the north (most of it publicly owned), a golf course to the south and east, and partially developed, single-family residential development to the south and west.  Surface water flows are generally from the northeast to southwest in this area.

Recommendations

The recommended plan for the Central Region consists of two projects, as shown in Figure 5-3.  The first project (CEN-A) is the construction of a permanent channel to the west of the golf course development.  The channel would run along Rhododendron Drive in an easement acquired by the City.  The channel should be lined to limit the infiltration of stormwater into the ground.  The channel would terminate at the corner of 35th Street and Rhododendron Drive.  At that point, flows would enter a pipe passing underneath Rhododendron Drive and connect with the large ravine to the west.  The ravine’s side slopes should be reinforced, as necessary, to stabilize the natural slopes and prevent erosion from occurring.  This recommendation would improve the hydraulic capacity of the collection system, which will help lessen the potential for flooding in this area.  This system should be sized to include the flows carried in the channel described as Project CEN-B.

Project CEN-B is a concrete lined channel extending along the east side of Mariners Village to the northeast corner of the development.  Construction of this channel is recommended to provide a pathway for flows originating from public land to the northeast.  CEN-B should be undertaken only after the downstream improvements are finished.  The existing temporary detention pond should be removed from service and flows routed to this new channel.

Table 5-1 lists the details of the improvements recommended for the Central Region conveyance system.  The capital cost of Project CEN-A is estimated at $******.  The length of the concrete-lined channel accounts for the majority of the project’s cost.  Project CEN-B, the channel extension along the east side of Mariners Village, has an estimated capital cost of $******.  Its smaller size and lack of roadway crossings result in a much lower cost.

Next Steps

A predesign investigation is required to better define the most cost-effective solutions available for this study area.  Specifically, additional survey information is required along the route of the CEN-A channel as well as information about the condition of the ravine at the downstream end.  During the predesign phase, opportunities for detention/wetland facilities north of Sandpines and Mariners Village should be investigated.  Such facilities could decrease flooding and improve water quality downstream.  Much of the land is public, so land acquisition costs are not a barrier.  Emphasis should be placed on restoring or enhancing degraded habitat.  However, wetlands should not be created at the expense of upland habitat that is in good condition.

Another opportunity may exist for a detention facility in the vacant lot at the corner of 35th Street and Rhododendron Drive that could enhance water quality or moderate peak flows downstream in the ravine.

The pipes along Oak Street should be inspected for signs of surcharging.

The Southwest Region stretches from 32nd Street to the north, to the Siuslaw River to the south and west, and to Highway 101 to the east.  It includes the Florence Airport and the Greentrees development.  The central portion of this region drains directly to a ditch that runs south between the airport and the Greentrees development.  The ditch continues south of 9th Street past the Florence Wastewater Treatment Plant to the Siuslaw River.  The other major  drainage system is a series of pipes that runs along Kingwood Street, crosses south of the airport runway, reemerges as a channel running south from the runway, and then is piped along 9th Street to the drainage ditch south of Greentrees.  The Greentrees development is served by an internal drainage system.

Recommendations

Two projects are recommended for the Southwest Region, as shown in Figure 5-4.  Project SW-A involves construction of a channel north from the point where the drainage ditch turns and runs south along the Greentrees property line.  This channel would intercept runoff from the property to the east.

Project SW-B requires the upsizing of the pipes along Kingwood Street to accommodate the
projected flows from the 25-year storm after future development occurs.

Table 5-1 lists the details of the improvements recommended for the Southwest Region conveyance system.  The capital cost of Project SW-A is $******.  The estimated capital cost of SW-B is $******.

Next Steps

The pipes in the downtown area should be inspected for signs of surcharging, but they do not need to be replaced unless they are in poor condition or cause flooding.  Coordination with regulatory agencies should be encouraged to ensure that the regular maintenance of the drainage ditch continues to be an approved activity.

The Southeast Region lies between 32nd Street to the north, the Siuslaw River to the south, Highway 101 to the west, and the hills to the east.  Munsel Creek is its most defining feature, along with the large wetland area between the hills and the creek.  The wetland has formed a deflation plain, where the sand was scoured away by the wind.  There is no natural drainage outlet for the area.

Recommendations

The Southeast Region contains one recommended project, as shown in Figure 5-5.  A pump station installation at the east end of Pine Court is designated as Project SE-A.  The pump intake would be set at a elevation to maintain the health and vitality of the existing wetlands.  When the groundwater level exceeds this elevation, the pump would be activated and discharge the flow into Munsel Creek.

Table 5-1 lists the details of the improvements recommended for the Southeast Region conveyance system.  The capital cost of Project SE-A is estimated at $******.

Next Steps

The delineated wetlands occurring in the Southeast Region are somewhat degraded.  Opportunities to work with local residents to enhance or restore the wetland should be pursued and, in fact, may be a permit condition required by state and federal regulatory agencies.

The Munsel Creek culvert should be investigated for indications of adverse impacts from backwater conditions at Highway 126 and on upstream culverts and property.

Draft Report – Use or disclosure of data contained on this sheet is subject to the restrictions specified at the beginning of this document.