TURNAGAIN STREET & TURNAGAIN BOULEVARD UPGRADE

Transcription

1 TURNAGAIN STREET & TURNAGAIN BOULEVARD UPGRADE SPENARD RD. TO NORTHERN LIGHTS BLVD. TURNAGAIN STREET TURNAGAIN BOULEVARD UPGRADE Design Study Report DRAFT December 2015 MOA Project No Prepared for: Municipality of Anchorage, Public Works Department, Project Management & Engineering Division, 4700 Elmore Road, Anchorage, Alaska Prepared by: CRW Engineering Group, LLC 3940 Arctic Blvd. Suite 300 Anchorage, Alaska

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3 Table of Contents I. Introduction... 1 Concept Report Summary/Project Goals... 1 II. Existing Conditions... 5 Area Context... 5 Facility Description... 5 Land Use and Ownership... 6 Geotechnical Summary... 6 Environmental... 6 Lighting... 8 Streetscape/Landscape... 8 Utilities Water Sewer Natural Gas Electric Telephone Cable Television Traffic Systems III. Drainage Existing Conditions Storm Water Model IV. Traffic and Safety Analysis Traffic Volume Traffic Characteristics Speeds Traffic Operations Crash Data Side Street Intersections/Access Control V. Design Criteria Design Standards Municipality of Anchorage State of Alaska Federal Design and Posted Speed Accessibility Guidelines Roadway Cross Section Roadway Clear Zone Lighting Landscaping Design Criteria Summary VI. Design Alternatives December 2015 Page i

4 Design Challenges Roadway Cross Section Vertical and Horizontal Alignment Geotechnical Recommendations Turnagain Boulevard (S) Turnagain Street (N)/West 34 th Avenue Subdrains Traffic Calming Lighting Landscaping Cluster Mailboxes Parking VII. Drainage Improvements Proposed Storm Drain System Stormwater Treatment VIII. Right-of-Way Impacts Overview Right-of-Way Easements/Permits IX. Utility Impacts X. Quantity and Cost Estimate XI. Stakeholder/Public Involvement XII. Design Recommendations Summary Phased Construction Preferred Alternative Drainage Traffic Calming Landscaping December 2015 Page ii

5 List of Figures Figure 1 Location Map... 3 Figure 2 Project Vicinity Map... 4 Figure 3 Area Zoning, Roadway Classifications, and Bus Stops... 7 Figure 4 Wetlands Map... 9 Figure 5 Existing Drainage Map (Turnagain Street (N)) Figure 6 - Existing Drainage Map (Turnagain Boulevard (S)) Figure 7 Drainage Basin Boundaries Figure 8 Existing and Projected Traffic Conditions Figure 9 Design Alternatives Figure 10 - Alternatives 1-6 Typical Sections Figure 11 - Alternatives 1 & 2 Typical Sections Figure 12 - Alternatives 3, 4 & 5 Typical Sections Figure 13 Proposed Drainage Map (Turnagain Street (N) Alternatives 1-3) Figure 14 Proposed Drainage Map (Turnagain Boulevard (S) All Alternatives) December 2015 Page iii

6 List of Tables Table 1 Summary of Existing Drainage Basin Runoff Table 2 Summary of Existing Peak Pipe Flows (Turnagain Street (N)) Table 3 Summary of Existing Peak Pipe Flows (Turnagain Boulevard (S)) Table 4 Existing AADT Traffic Data Table 5 Existing and Future (2035) Traffic Characteristic Summary Table Crash Summary for Intersections Table 7 Design Criteria Summary Table 8 Estimated Right-of-Way Easements/Permits Table 9 Summary of Estimated Project Costs Appendices Appendix A: Appendix B: Appendix C: Appendix D: Appendix E: Appendix F: Appendix G: Appendix H: Concept Report and Public Involvement/Comments Roadway Plan and Profile Drawings Existing Utilities Traffic Analysis Report and Data Geotechnical Analysis Drainage Analysis Right-of-Way Analysis Cost Estimates December 2015 Page iv

7 Abbreviations AADT AASHTO AASHTOGB ACS ADA ADEC ADF&G ADNR ADT ADOT&PF/DOT AFD AMATS AMC ASD ATP AWWU BOC CEA cfs CMP DCM DHV DIP DSR EB EOP GCI EPA ESCP HDPE IESNA ITE LOS MOA MPH MUTCD NB OS&HP PCM PCMP PM&E PUE Annual Average Daily Traffic volume (vehicles per day) American Association of State Highway Transportation Officials AASHTO Policy on Geometric Design of Highways and Streets Alaska Communication Systems Americans with Disability Act Alaska Department of Environmental Conservation Alaska Department of Fish and Game Alaska Department of Natural Resources Average Daily Traffic volume (vehicles per day) Alaska Department of Transportation and Public Facilities Anchorage Fire Department Anchorage Metropolitan Area Transportation Solutions Anchorage Municipal Code Anchorage School District Areawide Trails Plan Anchorage Water and Wastewater Utility Back of curb Chugach Electric Association Cubic foot per second Corrugated Metal Pipe Municipality of Anchorage Design Criteria Manual Design Hour Volume Ductile Iron Pipe Design Study Report Eastbound End of Project General Communications, Inc. Environmental Protection Agency Erosion and Sediment Control Plan High density polyethylene pipe Illumination Engineering Society of North America Institute of Traffic Engineers Level of Service Municipality of Anchorage Miles per hour Manual of Uniform Traffic Control Devices Northbound Official Streets and Highways Plan ADOT&PF Pre-Construction Manual Pre-coated Corrugated Metal Pipe Project Management and Engineering Public Use Easement December 2015 Page v

8 ROW SB sf SWMM SWPPP TCP UDC USACE vpd WB Right-of-way Southbound Square feet Storm Water Management Model Storm Water Pollution Prevention Plan Temporary Construction Permit Urban Design Commission US Army Corps of Engineers Vehicles per day Westbound December 2015 Page vi

9 I. Introduction The Municipality of Anchorage Project Management and Engineering (MOA PM&E) has contracted with CRW Engineering Group, LLC to provide professional services to evaluate alternatives to upgrade Turnagain Street & Turnagain Boulevard East to municipal standards. This Design Study Report analyzes the following roadway segments: Turnagain Street from West Northern Lights Boulevard to West 35 th Avenue. This segment of roadway is referred to as Turnagain Street (N) in this report. Turnagain Boulevard East from West 35 th Avenue to Spenard Road. This segment of roadway is referred to as Turnagain Boulevard (S) in this report. See FIGURE 1 for Project Location map and FIGURE 2 for Project Vicinity map. The scope of work includes a determination of appropriate design criteria to be used for the proposed improvements. This Turnagain Street (N) and Turnagain Boulevard (S) project respectively, were the number one and number two priorities for the Turnagain Community Council in Initially the project was funded with a $400,000 state grant for work on the preliminary design study. Additional funding has been acquired for final design study, detailed design, preconstruction tasks and right-of-way acquisition. Additional funding will be necessary for construction. Concept Report Summary/Project Goals Using the MOA Context Sensitive Solutions (CSS) Policy as a guideline, the Turnagain Street and Turnagain Boulevard Upgrade Concept Report was prepared. The goal of the CSS process is to collaborate with all stakeholders to improve the safety and mobility of the corridor, balance diverse interests, and to find areas of compromise that address budget and environmental concerns. The full Concept Report and range of stakeholder activities can be found in APPENDIX A. The CSS process will continue throughout the design phase of the project with additional opportunities for stakeholders to obtain information and provide feedback through the web page, e-newsletter updates, open houses, community council presentations, and direct feedback through phone calls and . Based on public and agency stakeholder input received during the Concept Report phase, the primary goals of this project are as follows: Upgrade Turnagain Boulevard (S) & Turnagain Street (N) to current MOA road standards, including new roadway surface, pedestrian facilities, and improved drainage; Evaluate and balance impacts to local accesses, businesses and adjacent properties. To achieve these goals, the Design Study Report (DSR) evaluates the need for the improvements to the roadway and pedestrian facilities, surface and subsurface drainage, pedestrian and vehicular connectivity, landscaping, signalization, and lighting. The DSR evaluates a range of conceptual design December 2015 Page 1

10 alternatives. The No Build alternative is not considered in this report as it is not supported by project stakeholders and does not address the problems that need to be resolved. December 2015 Page 2

11 Figure 1 Location Map December 2015 Page 3

12 Figure 2 Project Vicinity Map December 2015 Page 4

13 II. Existing Conditions Area Context The Turnagain neighborhood is one of the older areas of Anchorage with a diversity of housing types and residential densities. Kiwanis Fish Creek Park on Turnagain Boulevard (S) is a neighborhood park that also serves the greater Turnagain area. A portion of the Fish Creek Trail follows the western boundary of the park as it parallels Turnagain Boulevard (S). School-aged children in the area attend Northwood, Lake Hood or Turnagain Elementary Schools. Except for Lake Hood Elementary (a walking school), students attending elementary, middle and high school are bussed from stops along Turnagain Boulevard (S) and Turnagain Street (N). Fish Creek along with associated wetlands meanders adjacent to the project area. The topography of the area is generally flat. Vegetation along the two road corridors includes birch, alder, white spruce and cottonwoods. Facility Description Turnagain Street (N) from Northern Lights Boulevard to West 35 th Avenue and Turnagain Boulevard (S) from West 35 th Avenue to Spenard Road are both classified as neighborhood collectors in the 2014 Official Streets and Highway Plan (OS&HP). Neither of the roads meet current Municipal design standards. West Northern Lights Boulevard and Spenard Road are both Municipally-owned minor arterial roadways. Turnagain Street (N) is north-south roadway with two 11-foot wide, strip-paved lanes and a 2-foot wide gravel shoulder on both sides. Turnagain Street (N) ends at West 34 th Avenue, but resumes southward 150 feet west and ends at West 35 th Avenue. The public right-of-way (ROW) is approximately 40 feet for Turnagain Street (N), and 40 feet for West 34 th Avenue between the Turnagain Street (N) intersections. East and west of the Turnagain Street (N) intersections the West 34 th Avenue ROW narrows to 30 feet. The posted speed limit is 25 MPH and there are no existing pedestrian facilities. Turnagain Boulevard (S) is also a north-south roadway that has two 11-foot wide, strip-paved lanes with 2-foot wide gravel shoulders on both sides. There is a pathway that follows Turnagain Boulevard (S) from Spenard Road connecting to the Fish Creek Greenbelt through Fish Creek Park. There are no other pedestrian facilities along Turnagain Boulevard (S). ROW is approximately 60 feet wide. People Mover Transit does not currently serve Turnagain Street (N) or Turnagain Boulevard (S). The nearest transit routes are Route 36 along West Northern Lights Boulevard and Route 7 along Spenard Road. The Anchorage School District has school bus stops along Turnagain Street (N) and Turnagain Boulevard (S). Bus stop locations on Turnagain Street (N) are at West 30 th, 31 st, 32 nd and 34 th Avenue. Bus Stops on Turnagain Boulevard (S) are located at Borland Drive, Bennett Avenue, and Merrill Drive. December 2015 Page 5

14 Land Use and Ownership Land uses within the corridor are predominately residential (a mix of single family, two-family and multi-family), with commercial uses near the intersections of Spenard and West Northern Lights Boulevard. Turnagain Arts is at the south end of the Turnagain Boulevard (S) near Spenard Road. The Rustic Goat restaurant with residential living units was recently built at the southwest corner of Turnagain Street (N) and West Northern Lights Boulevard. Parcel 57 on the east side Turnagain Street (N) was recently rezoned and use change from a church to senior housing. Zoning is R3, R2D, R2M, R2M-SL, R1 and B3-SL, see FIGURE 3. Most of the area is built-out with some parcels with redevelopment potential including the trailer park on Turnagain Street (N) between West 30 th and 31 st Avenues. Geotechnical Summary Initially in 2011 a pavement reconnaissance and existing geotechnical data review was completed. In the fall of 2015, 18 boreholes were advanced throughout the project limits and a draft geotechnical investigation report was completed. The reconnaissance report and draft geotechnical report can be found in APPENDIX E. Turnagain Street (N) was repaved in 2009 and only showed minimal signs of distress in the form of thermal traverse cracking. The subsurface conditions were generally consistent, with some variability in material thicknesses and the depths. The subsurface conditions generally consisted of asphalt overlying sandy fill, followed by sand and clay. Groundwater was either not observed, or was observed between 9.5 to 15 feet below ground surface in a few boreholes. During the geotechnical boring operations, three boreholes were terminated at depths of 3.8 feet, 1.0 feet and 1.0 feet, respectively, due to indicators of potential hydrocarbon contamination in the soil. Drilling was ceased at these locations because the geotechnical engineer s scope did not include collecting petroleum contaminated soil in accordance with Alaska Department of Environmental Conservation (ADEC) guidelines and requirements, and therefore, no analytical testing was performed on the potentially contaminated soil. Further investigation is required to determine the presence of petroleum hydrocarbons or other chemicals of concern (COC) that exceed the ADEC cleanup levels. Approximately 100 feet of Turnagain Boulevard (S), near the intersection of McRae Road was recently resurfaced during the West 35 th Avenue & McRae Road project. The remaining section of Turnagain Boulevard (S) shows signs of pavement distress in the forms of transverse and longitudinal cracking, with several areas exhibiting fatigue cracking. The subsurface conditions were generally consistent, with some variability in material thicknesses and the depths. The subsurface conditions generally consisted of asphalt overlying sandy fill, overlying sand and clay. Groundwater was observed in most boreholes, and was within 5 feet of the road surface on average. Environmental Fish Creek parallels the east side of Turnagain Boulevard (S), north of the park to West 35 th Avenue. As part of the recently constructed 35 th Avenue and McRae Road project, a portion of the creek was re-routed and a new culvert crossing December 2015 Page 6

15 Figure 3 Area Zoning, Roadway Classifications, and Bus Stops December 2015 Page 7

16 installed under West 35 th Avenue. Based on a review of the Anchorage Wetlands Management Plan and the MOA Wetlands Atlas, 2008 Edition, the only designated wetlands within the project area are Class A wetlands associated with the Fish Creek corridor, see FIGURE 4. Lighting Existing lighting conditions are summarized for each road segment below: Turnagain Boulevard (S): There are light poles at each side street intersection with the exception of West 36 th Avenue. There are two additional light poles between Borland Drive and Bennett Avenue. The poles have High Pressure Sodium (HPS) fixtures. Turnagain Street (N) (West 35 th Avenue to West 34 th Avenue): Intersection lighting is provided at West 35 th Avenue and West 34 th Avenue. Fixtures are HPS and attached to wooden electrical power poles. West 34 th Avenue: Lighting is provided at the two intersections with Turnagain Street (N). Fixtures are HPS and attached to wooden electrical power poles. Turnagain Street (N) (West 34 th Avenue to West Northern Lights Boulevard): There are light poles at each side street intersection. The poles are standard metal light poles with mast arms and LED fixtures. Streetscape/Landscape Turnagain Street (N) An existing lawn area with tree/shrub landscape plantings, a pedestrian connection to an adjacent transit stop, and numerous above ground utility pedestals exist at the southeast corner of the Turnagain Street (N) and West Northern Lights Boulevard intersection. The Rustic Goat parking lot was also recently constructed in this quadrant of the intersection and includes a pathway from the parking lot to the intersection and pedestrian fencing between the pathway and back of curb. A multi-use trail connection and an established single family residential neighborhood can be accessed from the north portion of Turnagain Street (N) across West Northern Lights Boulevard. From West Northern Lights Boulevard, Turnagain Street (N) travels south through an established residential neighborhood consisting of multi-family and single-family structures. It includes parking areas, existing mature spruce and birch trees, fencing and mailboxes immediately adjacent to the edge of pavement. These existing elements are associated with private homes and multifamily residences and generally located at the edge of ROW. Turnagain Boulevard (S) Turnagain Boulevard (S) continues south from West 35th Avenue into a residential, public park and commercial area. The recently constructed West 35 th Avenue and McRae Road project improvements included a new pedestrian overlook space to the north of the Turnagain Boulevard (S) intersection. A series of neighborhood streets access Turnagain Boulevard (S) from the west including December 2015 Page 8

17 Figure 4 Wetlands Map December 2015 Page 9

18 West 36th Avenue, Wiley Post Avenue, Gilliam Circle, Bennett Avenue, Borland Drive and West 42nd Avenue. Kiwanis Fish Creek Park stretches along the east side of the roadway and includes portions of the Fish Creek Trail and a parking area. This park is a well-used community green space that includes a large lawn area, basketball court, tennis courts (recently resurfaced), a shelter, a play area and parking lot. Fish Creek itself borders east side of the park and bends to the west where it runs alongside Turnagain Boulevard (S), flowing north towards McRae Road. South of Fish Creek Park, uses transition from multi-family to commercial and light industrial uses closer to Spenard Road. The Turnagain Arts Building is a well-visited community arts and education center located on the east side of Turnagain Boulevard (S) between Borland Drive and West 42nd Avenue. A portion of the Fish Creek Trail splits immediately south of the Turnagain Arts Building to allow for bicycle and pedestrian travel along the eastbound and westbound lanes of Spenard Road. The existing roadside parking along the southwest length of Turnagain Boulevard (S) and at the Turnagain Arts Building addresses the desire for convenient vehicle access but creates conflicts with pedestrians and bicyclists traveling on the Fish Creek Trail and vehicles traveling on Turnagain Boulevard (S). The undefined asphalt and compacted gravel shoulders extend from the road edge to individual parking areas and up to building entries in numerous instances. Utilities Existing utilities within the project area include water, sanitary sewer, natural gas, electric, telephone, cable television, and fiber optic (See APPENDIX C for the location of the existing utilities). Utility locations shown are based on utility company facility maps. Field locates and surveys of existing utility lines were not performed for this report. Locations are considered conceptual at this phase. A utility conflict report will be prepared during the design phase. Scoping letters have been sent to the utility companies requesting additional information on existing facilities and any plans for future upgrades. Water Anchorage Water and Wastewater Utility (AWWU) owns and operates water facilities in the area. An 8-inch cast iron water main runs along the west side of Turnagain Boulevard (S) from the beginning of the project at Spenard Road to Borland Drive. An 8-inch ductile iron water main runs along Turnagain Boulevard (S) just south of Bennett Avenue (Station 20+25) to Wiley Post Avenue. This water main is not connected to the 8-inch cast iron pipe further south and AWWU may wish to connect these two mains to provide a looped system. Five of the parcels on Turnagain Boulevard (S) are still on private well systems. This includes two parcels (Parcel No. 22 and 73) in the Broadmoor Heights Subdivision and the majority of the parcels on the east side of the roadway in the Willard Addition 2 Subdivision. Residents should be given the opportunity to connect to AWWU s water system during this project to minimize the impacts to the roadway from future connections after the road is improved. December 2015 Page 10

19 An 8-inch asbestos concrete water main runs along the west side of Turnagain Boulevard (S) between McRae Road and West 34th Avenue and along the north side of West 34th Avenue. This 8-inch line continues north along the east side of Turnagain Street (N) to West Northern Lights Boulevard. This water main provides service to many of the neighborhoods in the project area. Six to eight inch asbestos concrete water mains branch off this line at all side streets. Sewer AWWU owns and operates the sanitary sewer facilities in the project area. Many of the parcels along Turnagain Boulevard (S) are served by mains that either front streets parallel to the project or in easements that run along the back of properties. A 30-inch sewer main runs along the east side of Turnagain Boulevard (S) from the beginning of the project at Spenard Road to Borland Drive. This main collects wastewater from neighborhoods south of Spenard Road. An 8-inch ductile iron sewer main runs along the east side of Turnagain Boulevard (S) from Bennett Avenue to McRae Road. An 8-inch asbestos concrete sewer runs along the east side of Turnagain Street (N) and the south side of West 34th Avenue from McRae Road to Station These lines collect wastewater from neighborhoods west of the project area. Eight-inch asbestos sewer mains cross Turnagain Street (N) at Stations 64+90, 67+90, 70+95, 71+25, and A 48-inch reinforced concrete sewer main runs along the centerline of Turnagain Street (N) from West 29th Avenue to an interceptor manhole at Station This manhole picks up wastewater from a force main that runs from the north. Natural Gas ENSTAR Natural Gas Company (ENSTAR) owns and operates natural gas facilities in the project area. ENSTAR has a gas main that runs along Turnagain Boulevard (S) and Turnagain Street (N) for the extent of the project. This main runs on the west side of Turnagain Boulevard (S) and Turnagain Street (N) except between McRae Road and West 34th Avenue where it runs on the east side of the roadway. The main is 4-inch plastic between Spenard Road and Bennett Avenue, 3-inch steel between Bennett Ave and McRae Road, and 6-inch steel between McRae Road and West Northern Lights Boulevard. Numerous services and mains branch off this main to provide natural gas service to the surrounding neighborhoods. These include twenty five services on Turnagain Boulevard (S), two services on West 34th Avenue, and fifteen services on Turnagain Street (N). Parcels on Borland Drive, West 34 th, 33 rd, 32 nd, 31 st, 30 th, and 29 th Avenues, are served by 1-1/4-inch steel gas mains. Electric Chugach Electric Association (CEA) owns and operates electrical facilities within the project area which include overhead and underground single and three phase electric lines. The majority of the parcels on Turnagain Boulevard (S) and Turnagain Street (N) are served by overhead electrical lines that run in easements along the back of December 2015 Page 11

20 property lines. CEA also provides lighting, primarily at intersections, on Turnagain Boulevard (S) and owns approximately eight utility poles with lights along the street. A three phase underground electric line runs in a private easement on the west side of Turnagain Boulevard (S) between Spenard Road and Borland Drive. Overhead single phase lines cross Turnagain Street (N) at Stations 40+20, 52+82, 64+85, and Underground single phase and three phase electric lines cross Turnagain Street (N) at Stations 41+75, 79+55, and Two three phase underground electrical lines run in an easement along the east side of Turnagain Street (N) from Station to West Northern Lights Boulevard. CEA also provides lighting for West 34 th Avenue via overhead power. The existing light pole at the intersection of West 34 th Avenue and Turnagain Street (N) will be impacted by street construction. This pole will need to be relocated to ensure overhead power is maintained to the other poles along West 34 th Avenue. Telephone Alaska Communication Systems (ACS) and General Communications Inc. (GCI) own and operate telephone facilities, including lines and pedestals, in the project area. Telephone service for parcels along Turnagain Boulevard (S) and Turnagain Street (N) is provided from underground and overhead telephone lines that run in easements along the back of property lines. Underground telephone crossings include a 2400 pair telephone line at Station An existing 100 pair telephone line runs north of McRae Road on the west side of Turnagain Street (N). ACS owns a duct system that consists of six 4-inch PVC conduits. This duct system crosses Turnagain Street (N) at Station and heads north on the west side of Turnagain Street (N) to West Northern Lights Boulevard. This duct system will be used for future underground telecommunications lines and should be protected during construction. Overhead 100 pair and 200 pair telephone lines cross Turnagain Boulevard (S) at Station and Turnagain Street (N) at Station The CEA pole impacted by construction at the intersection of West 34 th Avenue and Turnagain Street (N) also carries overhead telephone lines. Cable Television General Communications Inc. (GCI) also owns and operates cable TV facilities within the project area, consisting of underground/overhead coaxial cable lines, fiber optic lines, and pedestals. Television services for parcels in the project are provided primarily by underground and overhead coaxial cable lines that run in easements along back property lines. Underground coaxial cable lines cross Turnagain Street (N) at Station Overhead coaxial cable lines cross Turnagain Street (N) at Stations and The CEA pole impacted by construction at the intersection of West 34 th Avenue and Turnagain Street (N) also carries GCI s overhead coaxial cable. December 2015 Page 12

21 An underground fiber optic line crosses Turnagain Street (N) at Station and heads north to West Northern Lights Boulevard. This line should be protected during construction. Traffic Systems The Municipality of Anchorage owns and maintains a traffic signal at the intersection of Turnagain Street (N) and Northern Lights Boulevard. This signal system is a 4-leg intersection with Northern Lights Boulevard being the primary movement. Pedestrian crossings are allowed across the west, north, and south legs of the intersection. To increase pedestrian access, consideration should be given to the addition of a pedestrian crossing across the east leg of the intersection. Construction on Turnagain Street (N) will require replacement of the existing loop detectors. Additionally, a Type II junction box located at the south east corner will need to be relocated outside of the proposed street section. This junction box should be relocated behind the sidewalk to prevent any ADA issues. The existing traffic controller cabinet is located approximately 10 feet from the back of curb on the south east side of the intersection. Improvements to the intersection will widen Turnagain Street (N) reducing the clearance between traffic controller cabinet to the back of curb to 5 feet. This cabinet should be relocated to minimize the probably of being hit by an errant vehicle. December 2015 Page 13

22 III. Drainage Correcting problems with the existing storm drainage systems for Turnagain Street (N) and Turnagain Boulevard (S) is one of the primary goals of this project. The existing drainage facilities are inadequate to handle the high volume of runoff during spring and mid-winter thaw events, as well as high intensity rainfall in the summer months. Significant water ponding and glaciation at intersections creates difficult conditions for turn movements onto side streets. Areas of poor drainage have saturated the road subgrade resulting in heaving, cracking and general pavement failure. A drainage analysis was performed for the existing drainage system. The primary purpose for this analysis is to identify any existing drainage features that are not properly sized to convey peak flows during the design storm. Refer to APPENDIX F for the results of the drainage analysis. Existing Conditions The project area is located within the Fish Creek watershed. Turnagain Street (N) and Turnagain Boulevard (S) are primarily characterized by single family and multi-family residential developments. Several larger commercial lots are located along the south end of Turnagain Boulevard (S). Fish Creek Park is situated along the east side of Turnagain Boulevard (S). The majority of the project area has been fully developed; therefore the land characteristics for the contributing drainage basins for the pre- and post-development condition will not change beyond the proposed road and pathway improvements. The existing drainage systems along Turnagain Street (N) and Turnagain Boulevard (S) consist of several different sub-systems that convey storm runoff to Fish Creek. Each of these sub-systems are described in more detail below. In general, the topography in the project area slopes west to east towards Fish Creek, which parallels the east side of the project area and flows in a northerly direction. The existing storm drain systems for Turnagain Street (N) and Turnagain Boulevard (S) are shown in FIGURE 5 and FIGURE 6 respectively. From a drainage analysis perspective, the project area is divided into two sections: Turnagain Street (N) and Turnagain Boulevard (S). Turnagain Street (N) Drainage along Turnagain Street (N) generally flows from the north near West Northern Lights Boulevard to the south towards West 34 th Avenue. However, there are no clearly defined storm drain conveyance systems on either side of Turnagain Street (N), which currently does not have curb and gutter. As a result, storm runoff is conveyed alongside the roadway via shallow swales or overland. A combination of 12-inch and 15-inch CMP storm drain piping extends down the center of Turnagain Street (N) from West 29 th Avenue to West 33 rd Avenue. Curb inlets situated at each side street, primarily on the west side of the roadway, connect into this piped system. The curb inlets intercept the majority of runoff from Turnagain Street (N) on the west side of the roadway. Runoff on the east side of the roadway flows towards Fish Creek, either overland, through ditches and swales, or down the side streets. December 2015 Page 14

23 Figure 5 Existing Drainage Map (Turnagain Street (N)) December 2015 Page 15

24 Figure 6 - Existing Drainage Map (Turnagain Boulevard (S)) December 2015 Page 16

25 The contributing side streets to the east are outfitted with Type 2, rolled curb that convey runoff west to east. West 29 th, 31 st and 32 nd Avenues have piped storm drain systems and intermediate catch basins that connect to the piped system on Turnagain Street (N) previously described. West 30 th and 33 rd Avenues have catch basins located just west of Turnagain Street (N) that collect curb and gutter flow and direct it to the Turnagain Street (N) piped system. The piped system along Turnagain Street (N) continues to the west along West 33 rd Avenue. The West 33 rd Avenue storm drain consists of 15-inch CMP and an oil and grit separator upstream of the Fish Creek outfall. A separate 12-inch CMP piped storm drain system along West 34 th Avenue extends from Turnagain Street (N) to the west to Turnagain Street (N). This system continues south and connects into the recently re-constructed storm drain improvements on McRae Road. The McRae Road storm runoff is treated by a new oil and grit separator prior to discharging into Fish Creek, upstream of the roadway crossing culvert. Turnagain Boulevard (S) The existing storm drainage conveyance systems along Turnagain Boulevard (S) from Spenard Road to McRae Road are generally poorly defined. Similar to Turnagain Street (N), the majority of Turnagain Boulevard (S) does not have curb and gutter therefore, drainage is conveyed alongside the roadway via shallow drainage ditches and crossing culverts. In certain areas, runoff from these drainage ditches is intercepted by separate side street systems that outfall into Fish Creek. In many low lying areas, particularly near side street intersections, there are no catch basins or other means of intercepting runoff. In such cases, significant ponding and glaciation have been an issue. An 18-inch CMP piped system near the intersection of West 42 nd Avenue and Turnagain Boulevard (S) collects runoff from West 42 nd Avenue via several curb inlets. The 18-inch CMP extends to the east across Turnagain Boulevard (S), flows through an oil and grit separator and outfalls into Fish Creek. The oil and grit separator also serves as a stormwater treatment structure for larger systems extending west along Spenard Road, Wisconsin Street and adjoining areas. Storm runoff from these larger piped systems combine into one main and are routed through a diversion structure on the west side of Turnagain Boulevard (S) near the Spenard Road intersection. The diversion structure conveys flows to a common manhole with the West 42 nd Avenue system and is then directed to the aforementioned oil and grit separator. During larger storm events, runoff is directed to a 24-inch CMP overflow line from the diversion structure that discharges into Fish Creek just south of the outfall connected to the oil and grit separator piping. The two piped systems were not analyzed for this project. A 10-inch culvert collects runoff from the curb on the east side of Merill Drive and extends towards the east within an existing utility easement between Parcels 6 and 7. This culvert outfalls into Turnagain Boulevard (S). South of this outfall, a 15-inch culvert collects runoff from ditches on the west side of Turnagain Boulevard (S) just north of Borland Drive. The culvert extends to another culvert on the east side of Turnagain Boulevard (S) and continues east through private property and outfalls into Fish Creek. This culvert resides on Parcel 94 but there is no easement for this culvert on this parcel. There is a 5-foot drainage easement on Parcel 93 which is the parcel to the north or Parcel 94. The culvert is likely collapsed as it doesn t drain the area properly. During significant rain December 2015 Page 17

26 events, typically Turnagain Boulevard (S) is closed because of standing water that accumulates on the roadway between Borland Drive and this culvert. MOA Street Maintenance typically pumps out the area during these rain events. This process requires high pumping and labor costs. See pictures below from recent roadway flooding and MOA Street Maintenance operations. Turnagain Boulevard (S) Road Closure & MOA Maintenance Pumping during Rain Event in Fall 2015 A piped storm drain system along Bennett Avenue from Crosson Drive to Turnagain Boulevard (S) ranges in size from 12-inch to 24-inch CMP. Each side street slopes towards Bennett Drive and conveys runoff via Type 2, rolled curb to curb inlets located at each intersection. The Bennett storm drain system is failing due to corroded pipes and separated joints. MOA Street Maintenance has been making repairs to the existing storm drain system for the last 10 years. Runoff from the main on Bennett Avenue is directed across Turnagain Boulevard (S) to an oil and grit separator, crosses Fish Creek Park and outfalls into Fish Creek. A 36-inch trunk storm drain pipe runs east along West 36 th Avenue and discharges into Fish Creek on the west side of Turnagain Boulevard (S). This system covers a vast area including Wisconsin Street and extends as far west as Aero Avenue, collecting runoff from the majority of the adjoining neighborhoods. A large, concrete oil and grit separating chamber with a bypass configuration is located just west of Turnagain Boulevard (S) on West 36 th Avenue prior to the outfall. Culverts intercept runoff on either side of 36 th Avenue on the west side of December 2015 Page 18

27 Turnagain Boulevard (S). The West 36 th Avenue storm drain system was also not analyzed for this project due to its extensive contributing area and the proposed drainage improvements do not intend to utilize this system. Fish Creek flows through a 48-inch CMP driveway culvert downstream of the West 36 th Avenue outfall and upstream of the McRae Road culvert. A report titled Fish Creek Improvements Phase IV (HDR Alaska, Inc., January 2003) identifies the driveway culvert as undersized to pass the 10-year storm event. The report recommends replacing the culvert with two 48-inch CMP culverts or one culvert equivalent in capacity to accommodate the 100-year storm event to meet current MOA PM&E Design Criteria Manual (DCM) requirements. The McRae Road culvert was replaced with the recently completed 35 th Avenue & McRae Road Improvements project. Storm Water Model A storm water model was assembled and computed to analyze the capacity of the existing storm drainage conveyance systems in the project area. The drainage analysis approach is consistent with industry standards and the current MOA PM&E DCM and accompanying current Drainage Design Guidelines. Supporting data, figures and modeling results for the drainage analysis can be found in APPENDIX F. Refer to SECTION VII for drainage model information and results for the post-development condition. The storm drainage systems for the pre-development condition were modeled with Bentley CivilStorm V8 computer modeling software. The SCS Curve Number method was used to develop the rain-runoff response. As published in the MOA PM&E DCM, the SCS Type I, 10-year, 24-hour duration storm distribution was modeled to calculate and evaluate the peak discharge conveyance for all pertinent stormwater systems in the project area. Based on the location of the project area, the base storm volume of 1.77-inches for the design storm did not require adjusting for orographic factors. The peak flows from this storm event were analyzed to determine any deficiencies in the existing stormwater conveyance systems. The MOA is in the process of adopting a new Anchorage Stormwater Manual to replace the current Drainage Design Guidelines and MOA DCM Chapter 2 Drainage section. During reviews of this new document there have been discussions of increasing the storm volumes from the current guidelines. If changes to the storm volumes occur, the storm water model will need to be updated. The contributing drainage basins were developed and adjusted for the project area based on multiple sources of information. The computer software ArcMap by ESRI was used to view and analyze GIS data obtained from MOA Information Technology Department and Watershed Management Services. The GIS drainage basin boundaries developed for the Anchorage area are typically broader in scale than required for the smaller project area. As a result, these larger drainage basin boundaries were refined to appropriately reflect the contributing runoff to the project site. In conjunction with the GIS data, aerial imagery, record drawings, and survey information were utilized to define the drainage basins and associated characteristics, such as imperious area, slope, time of concentration and land cover type. Once the drainage basin data was December 2015 Page 19

28 compiled, Microsoft Excel was used to compute the necessary input parameters required for the CivilStorm modeling software. A total of 11 contributing drainage basins have been identified and analyzed for runoff response for the pre-development condition. The stormwater generated from each sub basin is summarized below in TABLE 1. Refer to FIGURE 7 for a map defining the drainage basin boundaries. Table 1 Summary of Existing Drainage Basin Runoff Basin Area Peak Runoff (cfs) 10-yr, 24-hr SCS Type 1 Storm ID (Acre) (cfs) (cfs/ac) B B B B B B B B B B B Turnagain Street (N) Peak pipe flows for the existing storm drainage system along Turnagain Street (N) and segments of the contributing side street systems are shown below in TABLE 2. Peak flows are based on the 10-year, 24-hour storm event. Based on the model results, several pipes along Turnagain Street (N) surcharge during the peak of the storm. Additionally, several manholes also surcharge during the design storm, two of which overtop at the intersections of West 30 th and West 31 st Avenues and Turnagain Street (N). Surcharging conditions are primarily due to insufficient pipe size and type, as well as relatively flat pipe slopes ( %). A reduction in downstream pipe diameter (E-P3&5, 12-inch CMP) from the upstream segment (E-P2, 15-inch) is also decreasing the overall capacity of the system. Refer to FIGURE 7 for locations of pipe segments listed in TABLE 2. December 2015 Page 20

29 Table 2 Summary of Existing Peak Pipe Flows (Turnagain Street (N)) Pipe Segment Pipe Description Pipe Diameter & Type Peak Flow (ft 3 /s) Pipe Surcharged E-P1 W 29th Avenue 15" CMP 1.19 Yes E-P2 Turnagain Street (N) 15" CMP 1.18 Yes E-P3 Turnagain Street (N) 12" CMP 1.64 Yes E-P4 W 31st Avenue 12" CMP 1.16 Yes E-P5 Turnagain Street (N) 12" CMP 2.51 Yes E-P6 W 32nd Avenue 12" CMP 1.51 Yes E-P7 Turnagain Street (N) 15" CMP 3.77 Yes E-P8 W 33rd Street 15" CMP 4.92 No E-P9 W 33rd Street 15" CMP 4.92 No E-P10 W 33rd Street 15" CMP 4.92 No E-P11 W 33rd Street - Outfall 15" CMP 4.92 No E-P12 Turnagain Street (N) 12" CMP 0.79 No Turnagain Boulevard (S) Peak pipe flows for the existing storm drainage system along Turnagain Boulevard (S) and segments of the contributing side street systems are shown below in TABLE 3. Peak flows are based on the 10-year, 24-hour storm event. Refer to FIGURE 6 for locations of pipe segments listed in TABLE 3. Table 3 Summary of Existing Peak Pipe Flows (Turnagain Boulevard (S)) Pipe Segment Pipe Description Pipe Diameter & Type Peak Flow (ft 3 /s) Pipe Surcharged E-C1 Wiley Post - Culvert 12" CMP 0.29 No E-P13 Bennett Avenue 18' CMP 4.53 No E-P14 Bennett Avenue 24" CMP 4.50 No E-P15 Bennett Avenue 24" CMP 4.47 No E-P16 Bennett Avenue 24" CMP 4.46 No E-P17 Bennett Avenue - Outfall 24" CMP 4.47 No E-C2 Turnagain Boulevard (S) - Culvert 12" CMP 1.33 No E-P18 Turnagain Boulevard (S) - Outfall 12" CMP 1.33 No E-P19 W 42nd Avenue 18" CMP 1.42 No E-P20 W 42nd Avenue 18" CMP 1.42 No E-P21 W 42nd Avenue - Outfall 18" CMP 1.41 No December 2015 Page 21

30 Figure 7 Drainage Basin Boundaries December 2015 Page 22

31 IV. Traffic and Safety Analysis A Traffic and Safety Analysis was completed by Kittelson and Associates (KAI). A summary of the analysis is below and the complete report is included in APPENDIX D. Traffic Volume MOA staff conducted daily traffic volume counts on Turnagain Boulevard (S) in 2008 and Turnagain Street (N) in Additional daily volumes were gathered from the Alaska Department of Transportation and Public Facilities (ADOT&PF). The 2035 AMATS regional travel demand model was consulted to determine the forecasted future daily traffic volumes for the study roadways. Turnagain Street (N) and Turnagain Boulevard (S) were not included in the model, but several adjacent roadways were modeled. The neighborhoods adjacent to both roadways are fully built-out residential districts. As a result, it is unlikely to see much further development and corresponding traffic growth in the future. McRae Road, a road with similar character and function was included in the AMATS model, but the 2035 volumes were slightly less than the 2007 volumes. To be conservative, volumes were estimated to grow at 0.5 percent per year. Annual growth rates for West Northern Lights Boulevard (1 percent) and Spenard Road (1.3 percent) were developed from the AMATS Model. McRae Road was also assumed to grow at 0.5 percent per year. The following TABLE 4 summarizes the AADT for the major streets in the project area: Table 4 Existing AADT Traffic Data Roadway Location 2008/11 Observed Daily Traffic Volumes Turnagain Street (N) Turnagain Blvd (S) West Northern Lights Blvd to West 34 th Avenue West 34 th Avenue to West 35 th Avenue Spenard Road to McRae Road 2035 Projected Daily Traffic Volumes FIGURE 8 shows the existing and projected 2035 AADTs. December 2015 Page 23

32 Figure 8 Existing and Projected Traffic Conditions December 2015 Page 24

33 Traffic Characteristics Design hour volume is used for capacity and equivalent single axle load computations for roadway sections. The design hour volume was estimated using existing traffic counts and total Average Annual Daily Traffic (AADT) for the streets. Directional distribution was estimated using the link counts for the peak hour of traffic. Peak Hour Factors (PHF) are a measure of the uniformity of the traffic and used to convert volumes to 15 minute design flow rates for capacity analyses. As the peak hour factor approaches 1.00, the traffic becomes more uniform. A peak hour factor of 0.92 was assumed for all movement during both the AM and PM peak periods. Table 5 Existing and Future (2035) Traffic Characteristic Summary Traffic Characteristic Turnagain Street (N) Turnagain Blvd East Design Hour Volume 11% 10% Peak Hour Factor Directional Distribution 31/69 58/42 Speeds The posted speed limit along both roadways is 25 MPH. The MOA Traffic Department conducted speed studies on Turnagain Boulevard (S) in 2008 and Turnagain Street (N) in The 85th Percentile speeds varied from 31 to 33 miles per hour. Two speed humps are installed on Turnagain Boulevard (S), 100 feet north and 500 feet south of Bennett Avenue. The continued use of speed humps or other vertical traffic calming measures are discussed further in SECTION VI Traffic Operations The MOA intersection operation standard for urban areas is level-of-service (LOS) D. Based on the traffic volumes shown in TABLE 4 and field observations, the intersections along the study corridor are anticipated to operate at LOS D or better under existing conditions and through the 2035 design year the exception of the Turnagain Boulevard (S)/Spenard Road intersection during the P.M. peak hour, during which the southbound left-turn operates at LOS F. Additionally, the unique nature of the existing geometry and traffic control at the two intersections on 35th Avenue-McRae Road does not allow the operations to be analyzed directly with the methodology described in the Highway Capacity Manual. To estimate the existing traffic operations, these intersections were analyzed under both one-way and all-way stop control with similar results. To confirm the study intersections would meet intersection operation standards, the project team analyzed the intersection with highest traffic volumes under 2035 A.M. and P.M. peak hour conditions. December 2015 Page 25

34 Crash Data Crash records have been obtained for the most recent 5 years ( ). See APPENDIX D. TABLE 6 below summarizes the intersection crashes. No fatalities were reported in the project area. ADOT&PF provides statewide average crash rates at a variety of intersection configurations based on the number of approaches and traffic control types. The average crash rate represents the approximate number of crashes that are expected at a study intersection. TABLE 6 includes the observed crash rates as well as the critical crash rate for each intersection. Table Crash Summary for Intersections Total Crashes ( ) Crash Rate (per MEV) Control State Average (per MEV) Critical Crash Rate West Northern Lights Blvd Signalized West 29 th Avenue way stop West 30 th Avenue way stop West 31 st Avenue way stop West 32 nd Avenue way stop West 33 rd Avenue way stop West 34 th Avenue way stop West 35 th Avenue way stop McRae Road way stop Bennett Avenue way stop West 42 nd Avenue way stop Spenard Road way stop Note: Intersections with no crash history are not recorded in this table. No intersections exceed the critical crash rate within the project area. Crash rate analysis is further summarized in APPENDIX D. Side Street Intersections/Access Control No median currently exists on Turnagain Street (N) at West Northern Lights Boulevard to separate northbound and southbound traffic. A median should be added at this intersection to separate traffic and improve the efficiency of the intersection. Most of the developed side streets along Turnagain Boulevard (S) intersect at a tee. With the exception of McRae Road, side streets connect to the west side of Turnagain Boulevard (S) and include: West 42 nd Avenue Borland Drive December 2015 Page 26

35 Bennett Avenue Gillam Circle Wiley Post Avenue West 36 th Avenue McRae Road West 35 th Avenue Most of the developed side streets along Turnagain Street (N) are four way intersections. These side streets include: West 33rd Avenue West 32 nd Avenue West 31 st Avenue West 30 th Avenue West 29 th Avenue These side streets are all stop controlled intersections with the primary movement on Turnagain Street (N) and Turnagain Boulevard (S) and the stop-controlled secondary movement on the side street (east-west traffic). Traffic volumes along the side streets are well below the requirement for the addition of turn lanes. The east and west approaches of West 31 st 30 th, and 29 th Avenues are offset by approximately 25 feet. There are approximately 31 driveways on Turnagain Street (N) and 24 on Turnagain Boulevard (S) that have direct access. Several of the parcels include wide access points and parking areas across site frontage. These configurations make access and circulation unclear to drivers and increase conflict points between vehicles utilizing the driveways and street traffic. The proposed design should incorporate MOA access standards wherever possible to improve the safety and operations of the corridor. December 2015 Page 27

36 V. Design Criteria Design Standards Project design criteria are a function of the roadway characteristics and the design standards used. The owner of the facility often dictate the design standards that are used. Since these are MOA owned and maintained roads, the design criteria are based on MOA design standards. The documents listed below provide the design guidance, standards and requirements for this project. Official Streets and Highways Plan (OS&HP), 2014 MOA Metropolitan Transportation Plan, 2012, MOA. Design Criteria Manual (DCM), 2007, MOA, Project Management and Engineering Department. Areawide Trails Plan (ATP), 1997, MOA, Department of Community Planning and Development. Anchorage Pedestrian Plan (APP), 2007, MOA, Traffic Department A Policy on Geometric Design of Highways and Streets, 6th Edition (AASHTOGB), 2011, American Association of State Highway and Transportation Officials (AASHTO). Roadside Design Guide (RDG), 4 th Edition, 2011, American Association of State Highway and Transportation Officials (AASHTO). Manual on Uniform Traffic Control Devices (MUTCD), 2009 Edition Including Revisions 1 and 2, 2012, U.S. Department of Transportation, FHWA. Guide for the Development of Bicycle Facilities, 4th Edition, 2012, American Association of State Highway and Transportation Officials (AASHTO). Alaska DOT&PF Preconstruction Manual (PCM), 2005, Alaska Department of Transportation and Public Facilities (ADOT&PF). Traffic Calming Protocol Manual, 2001, MOA Traffic Department. Traffic Calming Policy Manual (TCPM), 2005, MOA, Traffic Department. Alaska Traffic Manual (ATM), 2012, Alaska Department of Transportation and Public Facilities (ADOT&PF). Anchorage Bicycle Plan, 2010, MOA Traffic Department, AMATS Transportation Planning. Proposed Accessibility Guidelines for Pedestrians in Public Right-of-Way, 2011, United States Access Board. Anchorage Municipal Code Title 21 Land Use Planning. TABLE 7 at the end of this section provides a listing of the design criteria pertinent to this project. If required, the proposed variances from the DCM for this project will be justified and approved under a separate document during the design process. December 2015 Page 28

37 Municipality of Anchorage The 2014 Official Streets and Highways Plan (OS&HP) provides policies and standards for the transportation needs within the MOA. The OS&HP lists the functional classification for primary roadways located within Anchorage, Eagle River and Girdwood based on the Long-Range Transportation Plan. The OS&HP provides general roadway design standards based on functional classification including the number of lanes, width of ROW, and distance between intersections. According to the 2014 OS&HP, Turnagain Street (N) and Turnagain Boulevard (S) are designated as neighborhood collectors. A collector facility is designed to better accommodate bicycle and pedestrian activity. Collector streets are also designed to discourage on-street parking and limit direct access (the number of individual driveways). MOA collector standards require: Two travel lanes, with shoulders and curb and gutter; Pedestrian facilities on both sides Piped storm drain system (underground, collected by curb and gutter); and Street lighting. State of Alaska The ADOT&PF Highway Preconstruction Manual (PCM) provides detailed design criteria for federally-funded roadway projects within the State of Alaska. The PCM is intended to interpret and amend the goals and objectives of the AASHTO Policy on Geometric Design of Highways and Streets, the Green Book, (AASHTOGB). The PCM references other documents, including AASHTOGB, for many design parameters including alignment, intersection design, sight distance, design speed, grades, lane width and shoulder width. Federal AASHTOGB is a comprehensive reference manual for planning and design of highways and streets in the United States. The most current publication year for the AASHTOGB is The manual provides roadway design recommendations and standards based on functional classification. Design and Posted Speed The design speed affects the length of sight distance available along the roadway s horizontal alignment and vertical profile, particularly at intersecting roadways and pedestrian facilities. As design speeds increase, longer sight distances are required to provide more reaction time and braking distance to respond to roadway obstacles. Additionally, higher design speeds require a more gradual change in horizontal and vertical alignment, which typically increases the extent of cut and/or fill near hills. It is important that the design speed is slightly higher than the posted speed (typically 5 to 10 MPH higher) to provide a margin of safety for drivers driving at the speed limit in unfavorable conditions such as poor weather. December 2015 Page 29

38 Turnagain Street (N) and Turnagain Boulevard (S) have a current posted speed of 25 MPH. The DCM requires a design speed of 35 MPH for neighborhood collectors. Accessibility Guidelines The currently adopted requirements for accessibility in the MOA are based on the Americans with Disabilities Act (ADA). The project uses guidelines published in Proposed Accessibility Guidelines for Pedestrian Facilities in Public Right-of- Way- July 26, 2011 (ADA Guidelines) by the United States Access Board. A summary of some of the ADA design criteria pertinent to the Turnagain project is provided below: R The continuous clear width of pedestrian access routes shall be 4.0 feet minimum. R Where the clear width of pedestrian access routes is less than 5.0 feet, passing spaces shall be provided at intervals of 200 feet maximum. R Where pedestrian access routes are contained within a street or highway right-of-way, the grade of pedestrian access routes shall not exceed the general grade established for the adjacent street or highway. R Where pedestrian access routes are contained within pedestrian street crossings, the running grade of the pedestrian access route shall be 5% maximum. R302.6 The cross slope of pedestrian access routes shall be 2% maximum. R304.3 Parallel curb ramps shall comply with figure provided in the ADA Guidelines and include a turning space with minimum dimensions of 4.0 feet x 4.0 feet at the bottom of the ramp. R The running slope of the curb ramp shall be in-line with the direction of sidewalk travel and shall be 5% minimum and 8.3% maximum but shall not require the ramp length to exceed 15.0 feet maximum. The running slope of the turning space shall be 2% maximum in any direction. R The clear width of curb ramp runs and turning spaces shall be 4.0 feet minimum. R Grade breaks at the top and bottom of curb ramp runs shall be perpendicular to the direction of the ramp run. R The cross slope of curb ramps and turning spaces shall be 2% maximum. The Public Rights-of-Way Accessibility Guidelines recognize that it is not always possible for altered elements (reconstruction of existing facilities) to fully comply with new construction requirements because of existing physical constraints. The guidelines state: Where existing physical constraints make it impractical for altered elements, spaces, or facilities to fully comply with new construction requirements, compliance is required to the extent practicable within the scope of the project. Existing physical constraints include, but are not limited to, underlying terrain, right- December 2015 Page 30

39 of-way availability, underground structures, adjacent developed facilities, drainage, or the presence of a notable natural or historic feature. All elements included in the project that cannot meet the requirements of ADA due to technical infeasibility should be documented. ADA requirements will be analyzed in detail during the design process to determine if there are any elements that cannot meet the requirements. Roadway Cross Section The typical lane width for a neighborhood collector street is between 10 and 11 feet depending on existing and forecasted neighborhood densities, zoning, and traffic volumes. Shoulder widths vary between 3.5 and 5 feet on neighborhood collectors. Per the DCM, pedestrian improvements are to be provided on both sides of a collector street. Pathways and sidewalks are typically separated from the roadway to provide pedestrian comfort and safety, increase intersection sight distances, and provide room for snow storage. Snow storage area is required by Anchorage Municipal Code : All street rights-of-way shall include an open area, which may contain sidewalks, for snow storage. The open area (buffer) shall extend 7-feet outward from the back of the curb. Having the landscaping buffer behind the curb becomes even more important when using a narrow 3.5 foot (or less) shoulder cross section. This narrower shoulder provides little room for snow storage on the street, and snow will need to be temporarily placed behind the curb. Lack of an adequate landscape buffer could mean pedestrian passage is blocked partially or completely during major snow events. Roadway Clear Zone The DCM defines the roadway clear zone to be: the total roadside border area, starting at the edge of the traveled way, available for safe use by errant vehicles. The desired width of the clear zone is dependent on the traffic volume, design speed, and roadside geometry. The DCM references AASHTO s Roadside Design Guide (RDG) for rural conditions (i.e. no curb and gutter) but it is unclear as to the applicability of the clear zone concept to curbed urban roadways. In 2011, FHWA published the following guidance regarding clear zone along curbed roadways on their website: Since curbs are now generally recognized as having no significant containment or redirection capability, clear zone should be based on traffic volumes and speeds, both without and with a curb. The recommended clear zone width is a function of the design speed, traffic volume, functional classification of the roadway, and the side slope of the roadway. The clear zone required for a rural roadway with a design speed of <40 MPH and an ADT of 1,500 to 6,000 is 12 to 14 feet, with a foreslope of 1V:6H or flatter. December 2015 Page 31

40 However, the AASHTOGB, similar to the DCM, recognizes the impracticability of constructing a full clear zone, in accordance with the RDG, in urban areas. Where establishing a full-width clear zone in an urban area is not practical due to right-of-way constraints, consideration should be given to establishing a reduced clear zone or incorporating as many clear zone concepts as practical, such as removing roadside objects or making them crashworthy. The typical minimum roadway cross section for a neighborhood collector roadway will meet the minimum clear zone width of 12 feet specified in the RDG (3.5 foot wide shoulder + 2 foot wide curb + 5 foot wide sidewalk foot wide sidewalk shoulder = 12 feet). Lighting When installed, lighting systems shall be designed to the DCM s Chapter 5 criteria, enhancing traffic and pedestrian safety. A properly designed lighting system will: Provide the minimum maintained average luminance and illuminance levels specified for roadways, sidewalks, and intersections. Provide a uniformity of lighting that does not exceed the maximum ratios specified for roadways, sidewalks, and intersections. Minimize construction and maintenance costs. Avoid adverse impacts to adjacent properties. Reveal hazards to pedestrians and vehicular traffic. The MOA has retrofitted many existing luminaire poles with luminaires that use light emitting diodes (LEDs) as the light source and new roadway projects with lighting improvements now incorporate LED lighting into the design. The new proposed LED lighting system will be designed to provide the light levels specified in the DCM as shown in TABLE 7. The luminaires should also provide a full cutoff light distribution to reduce the negative effects of casting light on nearby properties (especially residences) and illuminating the night sky. To minimize the trespass of light on adjacent properties and reduce glare, luminaires are to be installed 30 feet above the pavement and fixtures in certain areas should have backlight control optics. Landscaping According to Chapter 3 of the DCM, landscaping efforts for collector streets should provide plantings that integrate new improvements with those of adjacent residential properties to provide an attractive transition between the street and the buildings. A 7-foot separation is desired between back of curb and any pathway or sidewalk to provide for temporary snow storage. Consideration should be given to placing underground utilities as close to the curb as possible to minimize conflicts with area residents. The 7-foot buffer width may be reduced or deleted if a 5-foot shoulder is provided at the street. The strip between the travel way and sidewalks/trails should be grass and used for runoff treatment during those periods that snow is not stored. Landscaping should be placed to December 2015 Page 32

41 the outside edge of the right-of-way adjacent to the property lines to take advantage of landscape improvements in the front yard setbacks. December 2015 Page 33

42 Design Criteria Summary Table 7 Design Criteria Summary CRITERIA Design Standard Value Reference Design Life 20 years Functional Classification Neighborhood Collector OS&HP Traffic Data AADT to 2100 vpd Field Data AADT to 2300 vpd Modeling Design Vehicle WB-50 DCM 6.4 B Design Structural Loading HS-20 Design Speed 35 MPH DCM 1.6 C Posted Speed 30 MPH DCM 1.6 C Horizontal Curve Radius, Minimum, No Superelevation Horizontal 600 ft DCM Table 1-9 Alignment Stopping Sight Distance, Min 250 ft DCM 1.9 D Clear Sight Triangle Length 390 ft DCM 1.9 E Vertical Grade, Maximum 8.0% (hillside) for roads w/ 2,000 or DCM 1.9 D greater AADT Vertical Vertical Curve K-Values, Min Alignment Crest Curve 29 DCM 1.9 D Sag Curve 49 DCM 1.9 D Number of Lanes 2 DCM Table 1-4 Lane Width ft DCM Table 1-4 Shoulder Width ft DCM Table 1-4 Cross On-Street Parking One or two sides DCM Table 1-4 Section Curb & Gutter Type 1 DCM 1.9 F Side slopes 2:1 maximum DCM 1.9 D 5 Clear Zone 12 ft See Section V.E Sidewalk Width 5.0 ft DCM Table 1-4 Pathway Width 8.0 ft DCM Table 1-4 Separation from Back of Curb ft DCM Table 1-4 Maximum driveway width, up to 7-plex 20 ft, 28 ft w/ DCM Appendix restrictions 1D Misc. Maximum driveway grade, up to 7-plex ± 10% DCM Appendix 1D Maximum landing grade/length, up to 7-plex ± 2% for 12 ft DCM Appendix 1D Maximum driveway width, 8-plex and greater 34 ft DCM Appendix 1D Maximum driveway grade, 8-plex and greater ± 8% DCM Appendix 1D Maximum landing grade/length, 8-plex and greater *Lighting design criteria is discussed in Section VI.F of this DSR. ± 2% for 20 ft DCM Appendix 1D December 2015 Page 34

43 VI. Design Alternatives Design Challenges Significant design challenges include: Turnagain Street (N) 40 foot wide ROW limits the width of the proposed roadway cross section, substantial property acquisitions are required to provide two pedestrian facilities. Most driveways have full frontage access and currently use the ROW for parking. Several structures are close to the ROW. Turnagain Boulevard (S) Turnagain Arts Building (Parcel 97) is constructed very close to the ROW and currently uses ROW for parking. The apartment complex on Parcel 3 utilizes ROW for parking. The proximity of Fish Creek poses limitations on the depth of any proposed storm drain facility. Roadway Cross Section The standard cross section for a neighborhood collector roadway has two 11-foot lanes, 3.5 to 5-foot shoulders, barrier curb and gutter, a 5-foot wide separated sidewalk and an 8-foot wide separated pathway shoulder width can be minimized where pedestrian facilities are separated from the roadway with a buffer. Five foot wide shoulders are appropriate for locations where sidewalks are attached to the back of curb. Wider shoulders can encourage on-street parking which is typically not desirable on collector roadways. However parking lanes are allowed on one or two sides of the roadway when warranted. When a parking lane is provided, the lane width shall be 7. In order to dissuade drivers from parking onstreet where parking is not warranted, a 3.5-foot wide shoulder is recommended. Type 1 barrier curb and gutter provides a greater safety measure for pedestrians on the sidewalk & pathway, discourages parking on buffers and pedestrian facilities, and also discourages full frontage width vehicular access of adjacent properties by defining specific driveway curb cuts. A two foot wide shoulder clear zone will be included on the outside of the pedestrian facilities. The pedestrian facilities will be delineated where it is adjacent to paved parking areas for businesses. Typical delineation will include either a grassed buffer or imprinted colored concrete and is discussed in more detail in the landscaping section. Pedestrian facilities will conform to ADA requirements for width, grade and cross slope as much as technically feasible and include detectable warnings at all roadway crossings. The following roadway cross section alternatives were developed for the various sections of the project, see FIGURE 9 for a plan view layout of the various alternatives. The main difference between the alternatives are the December 2015 Page 35

44 Figure 9 Design Alternatives December 2015 Page 36

45 number of pedestrian facilities and separation from curb. The addition of a pathway and pedestrian facility separation along Turnagain Street (N) yields significant property impacts. The alternatives 1-3 below all include a continuous sidewalk connection from Spenard Road to West Northern Lights Boulevard. For these alternatives, two 11-foot lanes, 3.5-foot shoulders and Type 1 barrier curb and gutter is provided, unless otherwise noted. 1. Alternative 1 This alternative was developed specifically to minimize impacts to adjacent properties on Turnagain Street (N) where minimal ROW exists. Typical sections of Alternative 1 are shown in FIGURE 10 and FIGURE 11. Plan and profile drawings can be found in APPENDIX B. a. Turnagain Street (N) (from West Northern Lights Boulevard to West 34 th Avenue): Attached sidewalk on west side. b. West 34 th Avenue: 1-foot shoulders and attached sidewalk on north side. c. Turnagain Street (N) (from West 34 th Avenue to West 35 th Avenue): no shoulders and attached sidewalk on west side. d. Turnagain Boulevard (S) (all sections): See Alternative Alternative 2 This alternative was developed to provide a roadway cross section that adheres closer to the DCM requirements of a neighborhood collector. Typical sections of Alternative 2 are shown in FIGURE 11 and plan and profile drawings can be found in APPENDIX B. a. Turnagain Street (N) and West 34 th Avenue: Detached sidewalk and pathway. b. Turnagain Boulevard (S) (all sections): See Alternative Alternative 3 This alternative was developed to provide a roadway cross section that adheres closer to the DCM requirements of a neighborhood collector and provides a more direct route from Turnagain Street (N) to Turnagain Boulevard (S). Typical sections of Alternative 3 are shown in FIGURE 12 and plan and profile drawings can be found in APPENDIX B. a. Turnagain Street (N): Detached sidewalk and pathway. b. West 34 th Avenue: Not improved, because of alternative alignment of Turnagain Street (N). c. Turnagain Boulevard (S) (all sections): See Alternative 6. Two additional alternatives have been developed for the north portion of the project to provide a pedestrian facility within the 40-foot ROW without the economic impact of a full road roadway reconstruction. The north project segment will benefit from a neighborhood collector configuration, but reconstruction, property acquisition and utility relocation costs could significantly delay these improvements. To provide a pedestrian facility in the shorter term, while minimizing project costs, these alternatives do not include complete roadway reconstruction and would not include storm drain replacement or lighting improvements on Turnagain Street (N) or West 34 th Avenue: 4. Alternative 4 This alternative was developed to provide an attached sidewalk facility along Turnagain Street (N). This would be accomplished by December 2015 Page 37

46 adding a curb along the west side of the roadway. Typical sections of Alternative 4 are shown in FIGURE 12. a. Turnagain Street (N): Addition of curb and sidewalk on west side only, existing pavement would be reclaimed and pavement would be widened to the east to match location and overall pavement width of Alternative 1. Reclaiming the pavement would provide additional design life for the driving surface. b. West 34 th Avenue: Addition of curb and sidewalk on north side only, existing pavement would be reclaimed and pavement would be widened to match location and overall pavement width of Alternative 1. c. Turnagain Boulevard (S) (all sections): See Alternative Alternative 5 This alternative was developed to provide an at-grade pedestrian facility along Turnagain Street (N). This would be accomplished by widening the existing pavement edge on the west side of the roadway by 5 feet. Typical sections of Alternative 5 are shown in FIGURE 12. a. Turnagain Street (N): Addition of 5 feet of pavement on west side for at-grade pedestrian facility. b. West 34 th Avenue: Addition of 5 feet of pavement on north side for at-grade pedestrian facility. c. Turnagain Boulevard (S) (all sections): See Alternative 6. The last alternative includes only improvements on Turnagain Boulevard (S) and was developed to reconstruct the worst part of roadway within the project limits and fix the flooding issues caused by insufficient drainage facilities. It also provides a lower ROW impact and overall cost alternative. Turnagain Street (N) was recently rehabilitated in 2009 which makes it a better candidate for reconstruction after Turnagain Boulevard (S) is reconstructed. 6. Alternative 6 This alternative was developed to provide improvements on Turnagain Boulevard (S) and to fix the current flooding problems along the roadway. a. Turnagain Boulevard (S) (McRae Road to Wiley Post): attached sidewalk on west side. b. Turnagain Boulevard (S) (Wiley Post to Gillam Circle and south of Bennett Avenue to West 42 nd Avenue): attached sidewalk on west side with separated (where feasible) pathway on east side. c. Turnagain Boulevard (S) (Gillam Circle to south of Bennett Avenue): On-street 10 parking lane with attached pathway on east side and attached sidewalk on west side. December 2015 Page 38

47 Figure 10 - Alternatives 1-6 Typical Sections December 2015 Page 39

48 Figure 11 - Alternatives 1 & 2 Typical Sections December 2015 Page 40

49 Figure 12 - Alternatives 3, 4 & 5 Typical Sections December 2015 Page 41

50 Vertical and Horizontal Alignment The intent for the roadway vertical alignment is to lower it to the maximum extent possible while minimizing adverse effects on adjacent driveways and intersections. By lowering the roadway, more overland drainage can be directed to the roadway and storm drain collection system and away from surrounding properties and building foundations. The proposed horizontal alignment for Turnagain Street (N) differs between the alternatives based upon the overall footprint of the roadway cross section. Below is a summary of the horizontal alignments for each alternative: 1. Alternative 1 The horizontal alignment for Turnagain Street (N) and West 34 th Avenue is shifted to the east to center the overall improvements in the ROW corridor in order to minimize impacts to adjacent properties. a. Turnagain Street (N) (from West Northern Lights Boulevard to West 34 th Avenue): The roadway centerline is approximately 2 feet east of the ROW centerline. b. West 34 th Avenue: The roadway centerline is approximately 1 foot south of the ROW centerline. c. Turnagain Street (N) (from West 34 th Avenue to West 35 th Avenue): The roadway centerline is approximately 1 foot east of the ROW centerline. d. Turnagain Boulevard (S) (all sections): See Alternative Alternative 2 - The widened footprint of Turnagain Street (N) cross section results in significant property impacts along the east side. A property acquisition analysis was performed and found acquisition costs and number of properties were both lower for expanding the facility east. a. Turnagain Street (N) (from West Northern Lights Boulevard to West 34 th Avenue): The roadway centerline is 10 feet east of the ROW centerline. b. West 34th Avenue: The roadway centerline is approximately 3 feet south of the ROW centerline. c. Turnagain Street (N) (from West 34 th Avenue to West 35 th Avenue): The roadway centerline is 18 feet east of the ROW centerline. d. Turnagain Boulevard (S) (all sections): See Alternative Alternative 3 The horizontal alignment is identical to Alternative 2 on Turnagain Street (N) from West Northern Lights Boulevard to West 34 th Avenue. At West 34 th Avenue, Turnagain Street (N) will continue south in a new roadway alignment that requires acquisition of 3 properties impacted. The property owner of 2 of the 3 properties has approached MOA about selling the properties. This alternative would eliminate two tee intersections and replace them with one four way intersection. a. Turnagain Boulevard (S) (all sections): See Alternative Alternative 4 The horizontal alignment of Turnagain Street (N) would match the layout of Alternative 1 except no curb would be installed on the east side of the roadway. December 2015 Page 42

51 a. Turnagain Boulevard (S) (all sections): See Alternative Alternative 5 The existing pavement would be widened on the west side, the centerline and east pavement location would remain the same. a. Turnagain Boulevard (S) (all sections): See Alternative Alternative 6 No improvements planned on Turnagain Street (N). For all the alternatives 1-6 Turnagain Boulevard (S) follows the existing roadway, with the overall improvement footprint shifted towards the east to provide adequate space to match into existing residential driveways on the western side of the ROW. Geotechnical Recommendations The MOA s Design Criteria Manual states that road sections should be designed to minimize the following: frost penetration into frost susceptible subgrade soil, movement of fine grained soil into the structural section, and differential frost heaving. This requires that the structural section either be designed to provide complete frost protection using the Complete Protection Method or allow for limited subgrade frost protection (subgrade frost protection may be up to 10 percent of the structural section thickness per the MOA DCM) using the Limited Frost Penetration Method. Turnagain Boulevard (S) After completing the BERG2 analysis along this section of roadway, the Complete Protection Method frost penetration depth is 8 feet. Therefore, excavation and replacement of existing subgrade soils with NFS materials to a depth of 8 feet is required to meet this design option. The Limited Subgrade Frost Penetration Method incorporates board insulation to greatly reduce the structural section thickness. Based on this, the recommended structural section is presented below: 3.5 inches Asphalt Pavement (note this is miss-labeled as 2 inches in Draft Geotechnical Report in APPENDIX E) 2 inches Leveling Course 18 inches MOA Type ll-a Board Insulation (R9) 24 inches MOA Type ll Turnagain Street (N)/West 34 th Avenue After completing the BERG2 analysis along this section of roadway, the Complete Protection Method frost penetration depth is estimated to be 8.5 feet. However, based upon the soil borings the subgrade soils within the upper 8.5 feet along this section of the alignment are considered low to non-frost susceptible. Therefore the recommended minimum thickness of the structural section in non-frost susceptible material is presented below: 3.5 inches Asphalt Pavement (note this is miss-labeled as 2 inches in Draft Geotechnical Report in APPENDIX E) December 2015 Page 43

52 2 inches Leveling Course 12 inches MOA Type ll-a 12 inches MOA Type ll For Alternatives 4 and 5 the Turnagain Street (N)/West 34th Avenue improvements do not include complete reconstruction of the roadway cross section. Alternative 4 will only include a new structural section below the proposed sidewalk/curb & gutter and the widened pavement areas. Alternative 5 will only include a new structural section below the proposed widened pavement section. Subdrains Based upon relatively deep groundwater levels along Turnagain Street (N), subdrains are not required for this section of the alignment. However it is recommended that roads along Turnagain Boulevard (S) be built with subdrains installed. In general, water level readings suggest the groundwater table is within or just below the anticipated structural section thickness. Installing a subdrain will help to improve overall road performance where groundwater has the potential to infiltrate into the structural section. Traffic Calming Based on speed studies and comments from local residents, speeding is a concern. Various methods for traffic calming were investigated, including: Vertical traffic calming measures (ex. speed hump, raised crosswalks) Horizontal traffic calming measures (ie: neckdowns) Colored crosswalks Roadway striping Both Turnagain Street (N) and Turnagain Boulevard (S) meet the guidelines for many of the traffic calming measures put forth in the MOA Traffic Calming Protocol Manual (Reference 7). The need for vertical traffic calming on Turnagain Boulevard (S) has been shown in past studies, and the continued use near Bennett Avenue as well as installing a raised crosswalk at the proposed Wiley Post Avenue intersection crosswalk is recommended. The design and specific location of these traffic calming treatments will be determined in the design phase. Though Turnagain Street (N) will be widened slightly with Alternatives 1, 4 & 5 the narrow right-of-way and existing buildings contribute to a constricted feeling, thus the need for traffic calming in the future is not certain. A speed study should be conducted upon completion of the proposed improvements to evaluate the need for traffic calming measures. For Alternatives 2 and 3, the proposed roadway and ROW footprint would require additional traffic calming considerations. The increased ROW would possibly allow for horizontal traffic calming measures to be incorporated. Roadway striping will be installed along the entire project corridor, including shoulder stripes, which will effectively reduce the visual appearance of the travel lane widths. The visual appearance of narrower lanes, as compared to feeling December 2015 Page 44

53 comfortable utilizing the entire roadway surface, reduces traffic speed. Shoulder stripes can also serve a dual purpose by designating the shoulder as a bike lane and reducing the visual dimensions of the travel lane. Lighting A new lighting system needs to be installed to achieve the light levels and uniformity ratios on the roads, sidewalks, and at the intersections. The system is to include round, tapered steel poles that provide a 30-foot luminaire mounting height and include mast arms that locate the luminaires in the positions determined by the lighting analysis. The luminaire pole bases are fixed as recommended in the DCM for streets with a posted speed limit less than 30 MPH with pedestrians present. The system also includes light emitting diode (LED) luminaires that provide a full cutoff light distribution. The poles are to be located on property corners, where feasible, to reduce the light trespass into adjacent homes. Light levels and uniformity ratios on roads, sidewalks, and at the intersections are summarized below: Roadway: The lighting system is to be designed to collector standards with low pedestrian conflict. The DCM recommends a minimum maintained average of 0.6 foot-candles with an average-to-minimum uniformity ratio no greater than 4:1 and a veiling luminance ratio no greater than 0.4. Pedestrian Facilities: Pedestrian activity meets the low criteria provided in Chapter 5 of the DCM. The DCM recommends a minimum maintained average of 0.4 foot-candles with an average-to-minimum uniformity ratio no greater than 4:1. Intersections: For collector/local intersections, the DCM recommends a minimum maintained average illumination of 1.0 foot-candles with an average-to-minimum uniformity ratio no greater than 4:1. Landscaping The overall goal of the landscape design is to limit impacts to existing vegetation where feasible and provide new landscaping where space allows. The existing ROW can accommodate road and pedestrian improvements but provides limited opportunity for new landscape improvements. The project design will strive to protect existing mature trees on private property that are adjacent to the proposed improvements; however, given the root systems of large trees it is likely some will be adversely impacted by the road improvements. Turnagain Street (N) Because of existing narrow ROW, there are few opportunities for landscape improvements. However, Alternatives 2 and 3 allow for additional landscaping improvements to be considered with the wider proposed ROW footprint. The intersection of West Northern Lights Boulevard and Turnagain Street (N) includes existing pedestrian amenities and landscape improvements. This project provides an opportunity to improve the pedestrian connectivity while maintaining a consistent identity with the neighborhood. The intersection might include similar December 2015 Page 45

54 landscape plantings and incorporate design language established as part of the West Northern Lights Boulevard project completed in recent years. Turnagain Boulevard (S) Opportunities for improvements within the ROW adjacent to Fish Creek Park includes delineation and enhancements to the pedestrian facilities and paved on-street parking to improve access to the park. The space between the Fish Creek Park lawn and proposed on-street parking could include street tree Turnagain Arts Building Concept plantings in a mounded planting bed. This mounded bed planted with large tree species will define the edge of the park, discourage vehicles from driving onto the lawn, prevent balls from rolling into the street, and provide a tree canopy along the proposed walkway. By using large trees, the canopies will be high enough not to impede views into and out of the park that if blocked might be a security concern. Conceptual Streetscape Improvements around the Turnagain Arts Building Further to the south, patterned concrete bands would better delineate the pedestrian facilities from the parking areas and driveways associated with the commercial properties. Traffic calming measures and associated landscape improvements may also be considered. Traffic calming measures provide an opportunity to enhance the corridor with additional landscaping and create a safer experience for pedestrians. Adjacent vertical elements along the corridor provide additional cues to drivers to reduce speeds. These cues can consist of planters, bollards, lighting or sculptural elements. It is important that vertical elements do not impede visibility of pedestrians or vehicles and must be installed so that they are compatible with maintenance needs, such as snow removal and snow storage. December 2015 Page 46

55 The use of neighborhood gateways has become a common way to add interest to streetscapes, provide neighborhoods with a unique identity and provide visual clues to drivers that they are entering a neighborhood. Gateways have been very successful in some neighborhoods and less so in others. Typically, the gateway features are most successful in neighborhoods that already possess a strong identity within the community. The most appropriate location for a gateway for this project would be at the southwest corner of Turnagain Boulevard (S) and Spenard Road. The Spenard Road intersection should include landscape plantings and adopt design language aesthetics from the ongoing Spenard Road reconstruction project between Chester Creek and West 29th Avenue and the West 35th Avenue and McRae Road reconstruction projects which also intersects with Spenard Road. There exists the potential to demarcate the Turnagain Boulevard (S) intersection with a design element similar to the wayfinding columns being installed on those projects to incorporate a unique community art piece that utilizes current design language. The goal will be to continue to establish identifiable neighborhoods within the larger Spenard community at major intersections for improved wayfinding. Wayfinding Examples Cluster Mailboxes Cluster mailboxes are desirable to the United States Postal Service as they facilitate maintenance, reduce delivery times, and provide a secure receptacle for the residents. Use of cluster mailboxes will be investigated further during design process. Parking December 2015 Page 47

56 On-street parking is typically discouraged on collector roads. However, during the public open house meeting many residents along both roadway corridors mentioned on street parking would be a desired feature. On Turnagain Boulevard (S) vehicles often park along the side of the road in front of the Fish Creek Park, and sometimes even drive into the park during crowded events. While Turnagain Street (N) lacks sufficient ROW to provide parking, there is room along Turnagain Boulevard (S). From Bennett Avenue to Gillam Circle, a parking lane could be added to the east side of the roadway. This would provide approximately 400 feet of on street parking, or roughly space for 20 vehicles. The east side pathway would be attached to the roadway curb through this area. Preliminary discussions with MOA Parks Department were favorable to this concept. Other areas for possible on street parking will be investigated during design. Conceptual On-Street Parking Layout at Fish Creek Park December 2015 Page 48

57 VII. Drainage Improvements Proposed Storm Drain System The proposed Turnagain Boulevard (S) storm drain system is the same for all the design alternatives. The proposed Turnagain Street (N) storm drain system varies between Alternatives 1-3 and no proposed storm drain improvements are proposed for Alternatives 4 & 5. The proposed drainage systems for Turnagain Street (N) and Turnagain Boulevard (S) are comprised of several different sub-systems that eventually discharge into Fish Creek. Each of these sub-systems are described in more detail below. The proposed roadway improvements for both Turnagain Street (N) and Turnagain Boulevard (S) will include the addition of curb and gutter along the entire length of each roadway. The curb and gutter will be designed to direct runoff to intermediate curb inlets that connect to piped systems. The proposed storm drain systems for Turnagain Street (N) and Turnagain Boulevard (S) are shown schematically in FIGURE 13 and FIGURE 14, respectively. Turnagain Street (N) Based on the drainage model results from SECTION III, the existing 12-inch and 15-inch CMP storm drain pipe along Turnagain Street (N) from West 29 th Avenue to West 33 rd Avenue is undersized to convey the 10-year storm. As a result, the proposed pipe diameter was increased to 18-inch smooth walled corrugated polyethylene pipe (CPEP, Type S). The 18-inch storm drain main will be installed in the same location as the existing pipe along Turnagain Street (N). Due to conflicts with utilities, the storm drain cannot be installed behind the back of curb, the standard location per the MOA Standard Specifications (MASS). Storm runoff from the contributing side street systems (West 29 th, 31 st & 32 nd Avenues) will be intercepted via new manholes and catch basins that connect to the proposed main. Additional catch basins will be installed along Turnagain Street (N) to collect intermediate runoff. In addition to upsizing the pipe along Turnagain Street (N), the existing 15-inch CMP on West 33 rd Avenue to the Fish Creek outfall also requires 18-inch CPEP to convey the 10-year flows. The proposed pipe will be installed in the same location as the existing pipe. The existing 12-inch CMP piped system that extends east to west along West 34 th Avenue down to McRae Road will also be increased to 18-inch CPEP. Turnagain Boulevard (S) There are several storm drain systems along side streets that cross Turnagain Boulevard (S) prior to discharging into Fish Creek as discussed in SECTION III; however there are no existing piped systems along Turnagain Boulevard (S) to collect runoff from the roadway or adjacent areas. The proposed improvements include installing an 18 inch CPEP storm main along Turnagain Boulevard (S) from Borland Drive to West 36 th Avenue, located at the back of curb on the east side of the roadway per MASS standards. It also includes installing a subdrain down the center of the roadway at the bottom of the structural section to resist groundwater infiltration into the structural section. The addition of a subdrain was December 2015 Page 49

58 recommended in the recently published draft geotechnical report and therefore the subdrain flows have not yet been included in the proposed storm water model but will be added for the Final DSR. The storm drain system along Bennet Avenue will be removed and replaced. The Bennett system will be modeled to ensure the storm drain main is appropriately sized. Storm runoff from the Bennett Avenue system and the 10-inch culvert north of Borland Drive from Merill Drive will be intercepted via a new manhole and inlet structure that connect to the proposed main. Additional catch basins will be installed along Turnagain Boulevard (S) at all side street intersections, intermediate points and designed low points in the roadway to collect runoff. The existing 48-inch driveway culvert north of West 36 th Avenue will be replaced with a pipe capable of passing the 100-year flood event. The existing 18-inch and 24-inch CMP piped systems near the intersection of West 42 nd Avenue and Turnagain Boulevard (S) will remain in place. As discussed in SECTION III, these two systems serve as water quality treatment and overflow for larger systems serving Spenard Road and Wisconsin Street. If required, the curb inlets at the intersection of 42 nd Avenue and Turnagain Boulevard (S) may be replaced to match the proposed curb and gutter. Stormwater Treatment Stormwater treatment facilities have been incorporated into the storm drain design to minimize potential water quality impacts to Fish Creek and downstream accepting water bodies. The design of the treatment facilities are based on the requirements of MOA and the State of Alaska Department of Environmental Conservation (ADEC). The proposed stormwater treatment design assumes oil and grit separators will be required prior to discharging storm runoff into Fish Creek at each outfall. The proposed design has primary outfalls at the east end of West 33 rd Avenue and south of West 34 th Avenue for the Turnagain Street (N) improvements. The outfall south of West 34 th Avenue will be routed through the recently installed oil and grit separator installed with the 35 th Avenue & McRae Road project. For the Turnagain Boulevard (S) improvements there will be an outfall east of West 36 th Avenue. The oil and grit separators will be sized to convey the 2-year, 24-hour storm. Refer to APPENDIX F for complete modeling results and storm water treatment product information. Design flows at each outfall are as follows: West 33 rd Avenue Outfall (Turnagain Street (N) System): 1.46 CFS West 36 th Avenue Outfall (Turnagain Boulevard (S) System): 1.48 CFS A bypass system will likely be installed around each oil and grit separator to convey the 10-year design storm. December 2015 Page 50

59 Figure 13 Proposed Drainage Map (Turnagain Street (N) Alternatives 1-3) December 2015 Page 51

60 Figure 14 Proposed Drainage Map (Turnagain Boulevard (S) All Alternatives) December 2015 Page 52