Appendix D Revised Transportation Impact Analysis. Heffron Transportation, Inc. May 2008

Transcription

1 Appendix D Revised Transportation Impact Analysis Heffron Transportation, Inc. May 2008

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3 TECHNICAL MEMORANDUM Project: Subject: Denny Middle School and Chief Sealth High School Redevelopment Date: May 1, 2008 Authors: Tod S. McBryan, P.E., Principal & Vice President This technical memorandum evaluates the transportation impacts of the proposed Denny Middle School and Chief Sealth High School redevelopments. It evaluates possible impacts from increased student enrollment capacity, site reconfiguration, and changes to parking supply and access. Specifically, this memorandum includes analyses of impacts to the roadway system, intersection operations, parking, traffic safety, site access, transit, non-motorized facilities, and event conditions that could occur with the redeveloped school facilities. This revised memorandum reflects revisions based on comments received through the public comment process that ended May 9, Project Description The project would construct new school buildings on the eastern portion of the Chief Sealth High School site at 2600 SW Thistle Street in Seattle to serve as a new Denny Middle School. Denny Middle School would be relocated to this site from its existing site approximately 1,00 feet to the southwest at th Avenue SW. The project would also renovate Chief Sealth High School consolidating its operations predominately to the western half of the existing Chief Sealth site. Figure 1 (attached) shows the proposed site plan of the Chief Sealth site. The project site (currently occupied only by Chief Sealth High School) is bounded by SW Thistle Street to the south, 27th Avenue SW to the west, SW Kenyon Street to the north, and by unimproved City right-of-way (2th Avenue SW alignment) and the Seattle Parks Longfellow Creek Greenspace to the east. For the 2007/2008 school year, enrollment at Chief Sealth High School is 90 students 1 ; current enrollment at Denny Middle School is 630 students. 2 The current start time for both schools is 7:0 A.M. and dismissal time is 2:1 P.M. The existing Denny Middle School site to the southwest and across SW Thistle Street would also be redeveloped. The existing buildings would be demolished, the site would be re-graded, and new recreational facilities and parking would be constructed. The recreational facilities could include up to twelve tennis courts and a softball field. These facilities would replace the facilities that would be lost with the construction of the new Denny Middle School on the northern portion of the Chief Sealth site. The new softball field is planned to be constructed in the southwest corner of the existing parking lot that serves the Southwest Athletic Complex. As a result, the softball field would displace about 180 of the existing 300 parking spaces. The District is proposing to replace those parking spaces at the northwest corner of the redeveloped Denny Middle School site. The two parking lots a smaller lot adjacent to the athletic fields and the new lot at the corner of SW Thistle Street and 30 th Avenue SW would provide the same parking capacity as currently exists. Both lots would be used for athletic activities at the complex, but also as overflow parking for some larger events at Chief Sealth High School. The new lot may also be used by visitors to the existing Southwest Community Center that 1 Bassetti Architects communication with Chief Sealth High School Principal John Boyd, October Bassetti Architects communication with Denny Middle School Principal Jeff Clark, October NE 61st Street, Seattle, WA 9811 Phone: (206) Fax: (206) 23-99

4 would be located immediately to the east of it. The exact configuration of the redeveloped Denny site has not been determined. One possible configuration for the redeveloped Denny Middle School site is shown on Figure 2 (attached). The redeveloped schools are expected to be complete and occupied by the school year with Chief Sealth High School planned to be completed by fall of 2010 and Denny Middle School planned to be completed by fall/winter of Redevelopment of the Denny Middle School site is expected to begin in the summer of 2011 and be complete by spring of Specific components of the proposed project are listed below. The existing Chief Sealth school buildings would be renovated with no planned changed to its existing building size of 212,29 square feet (sf). New Denny Middle School buildings would be constructed on the eastern portion of the site to provide total building space of 11,76 sf. The renovated Chief Sealth High School could house up to 1,200 students an increase of 20 students compared to existing conditions. This analysis accounts for 1,200 students. The relocated Denny Middle School could house up to 900 students an increase of 270 students compared to existing conditions. This analysis accounts for 900 students. Parking on the overall site would be redeveloped to provide a total of about 17 on-site parking spaces. Of these, about 60 spaces would be for Denny Middle School and would be located at the northwestern corner of the site. About 11 on-site spaces would be provide for Chief Sealth High School with about 93 spaces in the reconfigured main parking lot and about 22 parking spaces in the southwestern employee parking lot. The proposed Denny Middle School parking lot would also have automobile loading / unloading space for about 21 vehicles simultaneously; the Chief Sealth High School main lot would have loading / unloading space for about 1 vehicles simultaneously. A new service drive and bus pick-up/drop-off area would be provided along the eastern side of the site. It would function as a one-way drive aisle with the entrance from SW Kenyon Street and exit onto SW Thistle Street. This drive would be used for school buses serving Denny Middle School as well as for deliveries to the school s loading dock. The existing loading dock for Chief Sealth High School north of the small western staff parking lot would remain in its current location. Vehicular access to the new Denny Middle School parking and passenger loading areas would occur from the existing northern site access driveway that is opposite 26 th Avenue SW. A new inbound-only access driveway is proposed to the east for the one-way southbound service drive and bus loading/unloading area. The service and bus lane would exit directly to SW Thistle Street at the southeast corner of the site immediately adjacent to and east of the inbound driveway for the main Chief Sealth parking lot. Vehicular access to the Chief Sealth site would occur from three driveways along SW Thistle Street. Students, visitors, and pick-up/drop-off vehicles would enter using the eastern inbound driveway (relocated slightly westward from its existing location) and exit using the existing middle outbound driveway opposite 26 th Avenue SW. The staff parking lot and loading dock would be accessed from the existing westernmost driveway. Pedestrian access to the site for both schools would occur from SW Thistle Street, SW Kenyon Street, and using stairways from 27 th Avenue SW. The new Denny Middle School would include a gymnasium with bleacher seating capacity of about 1,000 persons to accommodate the full student body and staff for an assembly. -2- May 1, 2008

5 The Chief Sealth High School renovation is not expected to change the existing seating capacity of the gymnasium (2,171 persons), auditorium (about 1,000 seats), or the Little Theater (86 seats). The southwest corner of the existing Southwest Athletic Complex parking lot would be redeveloped to provide a softball field. The new field would displace about 180 parking spaces. The existing Denny Middle School site would be cleared and re-graded to provide up to twelve tennis courts, and about 180 parking spaces to replace parking that would be lost to the new softball field. The softball field would also not be lighted and would be available for District athletic uses only. Table 1 summarizes the key transportation-related elements of the existing and proposed uses at the Chief Sealth High School site. Table 1. Chief Sealth & Denny Middle School Redevelopment Project Site Summary School Existing Proposed Net Change Denny Middle School Enrollment 1 Buildings On-Site Parking On-Site Vehicle Loading 630 students 119,286 sf 2 ~ spaces (unstriped) None, uses street 900 students 11,76 sf 3 ~60 spaces ~ 21 spaces students + 22,78 sf + spaces + 21 spaces Chief Sealth High School Enrollment Buildings On-Site Parking 90 students 212,29 sf 3 ~ 197 spaces (172 striped, ~ 2 unstriped ) 1,200 students 212,29 sf 3 ~11 spaces + 20 students No Change - 82 spaces (- 7 striped, - 2 unstriped) On-Site Vehicle Loading ~ 12 spaces ~ 1 spaces + 3 spaces Sources: Bassetti Architects, 2007; King County Assessor Website Parcel Viewer, November 2007; Heffron Transportation, Inc. 1. Existing enrollment provided by Bassetti Architects in October 2007 based on discussions with principals of both schools. 2. This is the amount of total building space listed by the King County Assessor for the site. 3. Source: Bassetti Architects, November Includes about 20 unmarked spaces along west side of tennis courts/softball fields and about unmarked spaces in the southwest lot. 2. Background Conditions This section describes the existing and future background (without-project) conditions. It includes descriptions of the surrounding roadway network, traffic volumes, transit facilities and service, parking, pedestrian facilities, and event conditions. This section serves as a basis of comparison to determine the impacts of the planned project Roadway Network The study area for this analysis was determined based on the potential effects that could occur from the relocation of Denny Middle School, the increased enrollment from both schools, and other elements of the redevelopment project. The study area intersections and roadways were selected based on routes expected to be used to access both schools and the potential for project-related impacts. These potential effects are described in detail later in this report. The proposal is not expected to substantially change traffic volumes or access routes far outside of the project study area, since both schools already exist in the community. The study area for the transportation analysis includes the following roadways: -3- May 1, 2008

6 SW Thistle Street is a minor arterial that provides east-west access between 3 th Avenue SW and Delridge Way SW. This roadway segment has two travel lanes (one in each direction) and parallel onstreet parking allowed on both sides along most of the street. West of 3 th Avenue SW, SW Thistle Street becomes a collector arterial. Near the project site, on-street parking is permitted on the north side of the street adjacent to the Chief Sealth High School. However, approximately 12 spaces are restricted to school loading only between 7:00 A.M. and :00 P.M. SW Thistle Street has curbs, gutters, and paved sidewalks on both sides. Traffic signals control its intersections with 3 th Avenue SW and Delridge Way SW. Marked and signed crosswalks are located at the 32 nd Avenue SW, 30 th Avenue SW, and 26 th Avenue SW/Chief Sealth High School. At the 26 th Avenue SW/Chief Sealth High School intersection the roadway has been narrowed with curb-bulbs at crosswalk to shorten crossing distance and enhance pedestrian visibility to drivers. SW Kenyon Street is a two-lane, east-west residential access street that connects between 2 th Avenue SW and 3 th Avenue SW. It represents the northern site boundary of the Chief Sealth High School site. There are curbs, gutters, and sidewalks on both sides of the street and parking is allowed on both sides. Traffic circles control movements at intersections with 28 th and 30 th Avenues SW. Its approach to 3 th Avenue SW is controlled by a stop sign. Its intersections with 27 th Avenue SW and 26 th Avenue SW are uncontrolled. In the study area, SW Kenyon Street terminates at 2 th Avenue SW just east of the Chief Sealth High School site. 27 th Avenue SW is a two-lane, north-south residential access street that connects SW Thistle Street to SW Kenyon Street. It represents the western site boundary of the Chief Sealth High School site. There are curbs, gutters, and sidewalks on both sides of the street and parking is allowed on both sides. The sidewalk along the east side of the street is in fair condition, but weeds and grasses are growing up through cracks in much of the pavement. Stop signs control the 27 th Avenue SW intersection with SW Thistle Street. Its intersection with SW Kenyon Street is uncontrolled. 26 th Avenue SW is a north-south residential access street that extends north from SW Kenyon Street opposite the Chief Sealth High School north parking lot access driveway and connects to SW Holden Street. South of the school, it extends south to provide access to multi-family residences south of SW Thistle Street, but does not connect through to SW Trenton Street. 2 th and 28 th Avenues SW are north-south residential access streets that also provide connections between SW Kenyon Street and SW Holden Street. 30 th Avenue SW is a north-south residential access street that extends though SW Kenyon Street to the north, crosses SW Thistle Street, and extends south through SW Trenton Street. It represents the western boundary of the existing Denny Middle School site. Its approaches to SW Thistle, Trenton, and Kenyon Streets are stop-sign controlled. SW Cloverdale Street is a two-lane, east-west residential access street that connects from 29 th Avenue SW west to 3 th Avenue SW. It represents the southern site boundary of the existing Denny Middle School site. There are curbs, gutters, and sidewalks on both sides of the street and parking is allowed on both sides. 3 th Avenue SW is a principal arterial that provides for north-south access throughout West Seattle. For most of its length, it has four travel lanes (two in each direction) with on-street parking and turn pockets in many locations. Near the project site, its intersections with SW Thistle Street, SW Holden Street, and SW Trenton Street are signalized. Delridge Way SW is a principal arterial that provides for north-south access from the West Seattle Bridge to White Center. For most of its length, it has two travel lanes (one in each direction) with on -- May 1, 2008

7 street parking and turn pockets in many locations. Near the project site, its intersections with SW Thistle Street, SW Holden Street, and SW Trenton Street are signalized. Within the City of Seattle, the speed limit on arterials is 30 mph, unless otherwise posted; the speed limit on other roadways is 2 mph. Several planning documents were reviewed to determine what transportation improvements might be made near the Chief Sealth High School site by the school year when both schools would be complete and re-occupied. These documents included: the Westwoood & Highland Park Neighborhood Plan and the Delridge Neighborhood Plan (the neighborhood plans encompassing the area surrounding Chief Sealth High School); the Plan Matrices for the Westwoood & Highland Park Neighborhood Plan and the Delridge Neighborhood Plan; the City of Seattle Adopted Capital Improvement Program; and the City of Seattle Proposed Capital Improvement Program. The following describes each document and the parts pertinent to the Chief Sealth site area. Some of the recommended improvements in the plans (prepared in 1999) have already been implemented or reviewed and considered by the City of Seattle. The Westwood & Highland Park Neighborhood Plan includes a policy to Seek to enhance east/west pedestrian linkages with pedestrian improvements along SW Trenton Street and SW Thistle Street. The Plan Matrix for Westwoood & Highland Park Neighborhood Plan included measures to link Westwood/Highland Park together through the Longfellow Creek Legacy Trail. As part of this, a recommended measure was to create a pedestrian and bicycle trail loop beginning at Hughes Playground then south to SW Thistle Street, adjacent to the western edge of Chief Sealth High School, then one block east on SW Kenyon Street, then south on 27th Avenue SW. Other measures were also suggested as part of the trail plan including marking the trail west along SW Thistle Street to Denny Middle School and the Southwest Community Center, adding pavement patterns, and pedestrian-scale lighting. Some improvements recommended by the plan for crosswalks (such as curb bulbs and signage) and intersection improvements (such as traffic signals and turn lanes) have been implemented. The Delridge Neighborhood Plan includes Goal 3 to create an integrated system of regional and local oriented on and off-road bicycle routes that access local residential neighborhoods, parks, schools, community facilities, business districts and regional employment, commercial, and recreational destinations. A key recommendation included identifying SW Thistle Street between 3 th Avenue SW and 9 th Avenue SW as an east-west segment of a community loop for bicycles. It also included a goal for public facilities and recommended that the neighborhood cooperate with the City of Seattle, Seattle School District, Port of Seattle, King County, South Seattle Community College, Washington State Department of Social & Health Services, and other public and private agencies to provide quality public services and facilities for residents of the Delridge community. The plans can be viewed at The Delridge Neighborhood Plan and Westwood/Highland Park Plan Implementation Priority Reports (City of Seattle, 200 Priority Updates) include several actions being undertaken by the SDOT as a result of recommendations in the plans. However, none are expected to change the vehicular capacity or operations in the immediate site vicinity of Chief Sealth High School or Denny Middle School. There were no specific funded transportation projects within the local site vicinity included in the Transportation project summaries of either the Adopted Capital Improvement Program or the Proposed Capital Improvement Program. Therefore, existing intersection and traffic control conditions were assumed to remain for future-year conditions ( school year). There are several general projects that would fund neighborhood pedestrian improvements, but no specific locations or improvements are identified. -- May 1, 2008

8 2.2. Traffic Volumes The following sections summarize existing (2007) and future (2012) without-project traffic volumes. This future without-project condition assumes that the existing schools would not change location or enrollment. Year 2012 was selected as the future analysis year because it is when both schools would be complete and occupied Chief Sealth High School by fall of 2010 and Denny Middle School by fall/winter of School Traffic Traffic generation estimates for the existing Chief Sealth High School were developed from new manual turning movement counts performed at the school s site driveways in late September Trips turning into and out of the school s driveways were counted in the morning and afternoon. Based on field observations, some additional school-related trips occur as students load or unload along both sides of SW Thistle Street. The turning movement counts were combined with estimated on-street loading/unloading trips to determine total site trip generation. Based on these analyses, the existing Chief Sealth High School generates 390 AM peak hour trips (7:00 to 8:00 A.M.), 20 trips during the school s afternoon peak hour (2:00 to 3:00 P.M.), and 12 trips during the PM peak hour of the adjacent roadways (:00 to 6:00 P.M.). A summary of the school s existing trip generation is presented in Table 1. The school s existing trip generation was compared to nationally published rates for high schools (Land Use Code 30) in Trip Generation. 3 The observed trip generation rates at Chief Sealth High School are identical to published national rates for the AM peak hour (0.1 trips per student) and similar but slightly lower than published rates for the afternoon time periods (0.22 trips per student at Sealth compared to ITE s 0.28 trips per student during the school s afternoon peak hour and 0.13 trips per student at Sealth compared to 0.1 trips per student during the PM peak hour of the adjacent streets). Since Denny Middle School relies almost entirely on local neighborhood streets for parking, bus loading/unloading, and automobile loading/unloading, it was not possible to determine existing school trips generation from counts. Therefore, rates published in Trip Generation based on enrollment were selected to estimate traffic generated by the existing school. Based on the current (2007/2008) enrollment figure of 630 students, the existing Denny Middle School generates 33 AM peak hour trips, 190 trips during the school s afternoon peak hour, and 9 trips during the PM peak hour of the adjacent streets. Table 2 also summarizes the trip generation estimates for Denny Middle School. Table 2. Existing Traffic Generation Chief Sealth High School & Denny Middle School Period AM Peak Hour (7:00 to 8:00 A.M.) School PM Peak Hour (2:00 to 3:00 P.M.) Chief Sealth High School 1 In Out Total Denny Middle School 2 In Out Total Commuter PM Peak Hour (:00 to 6:00 P.M.) Source: Heffron Transportation, Inc., November Trip generation determined from counts performed at the school in September Trip generation determined using rates from ITE s Trip Generation, 7 th Ed, 2003, Middle School/Junior High School - LU Code 22. Note: Classes at both schools begin at 7:0 A.M. and students are dismissed at 2:1 P.M. 3 Institute of Transportation Engineers, 7 th Edition, May 1, 2008

9 The routes that drivers use to access both schools are related to the location of primary access streets in the site vicinity, the location of parking, and the areas where bus and automobile loading and unloading typically occurs. Currently, the focus of most inbound and outbound access for both schools is SW Thistle Street. However, some drivers approach the schools from local residential streets that make up the grid system. For Chief Sealth High School, these include 26 th Avenue SW, 27 th Avenue SW, and SW Kenyon Street. For Denny Middle School, these include 30 th Avenue SW, SW Cloverdale Street, and 29 th Avenue SW. Existing Street Traffic Traffic volume data were collected at several locations surrounding the project site. It is important to note that the existing volumes in the study area are affected by school-related traffic generated by both Chief Sealth High School and Denny Middle School. To document the level of traffic with the schools in session, new 72-hour machine counts were commissioned on Tuesday, Wednesday, and Thursday, September 2, 26, and 27, 2007 on SW Thistle Street between 26 th and 27 th Avenues SW. The 72-hour machine counts were compiled to better understand traffic patterns along SW Thistle Street in front of Chief Sealth High School. Figure 3 shows the average weekday traffic volumes during each hour of the day. As shown, the highest volume occurs during the AM peak hour (7:00 to 8:00 A.M.) when students arrive at both schools. The volumes during the time when both schools are dismissed (2:00 to 3:00 P.M.) are lower (by 33%). Volume during the commuter PM peak hour (:00 to 6:00 P.M.) are about 6% lower than the AM peak hour volumes, but school traffic is much lower during this time (between 68% and 72% lower than AM peak hour volumes). Traffic operations analyses for the proposed project were performed for the two hours when the schools would generate the highest amount of traffic AM peak hour and school PM peak hour. Figure 3. Total Hourly Traffic Volumes on SW Thistle Street at Chief Sealth HS Traffic Volume (vehicles per hour) AM Peak Volume = 9 Eastbound Westbound Total PM Peak Volume = :00 AM 1:00 AM 2:00 AM 3:00 AM :00 AM :00 AM 6:00 AM 7:00 AM 8:00 AM 9:00 AM 10:00 AM 11:00 AM 12:00 PM 1:00 PM 2:00 PM 3:00 PM :00 PM :00 PM 6:00 PM 7:00 PM 8:00 PM 9:00 PM 10:00 PM 11:00 PM Time of Day (hour begin) Source: 8-Hour machine traffic counts commissioned by Heffron Transportation, Inc. and performed by Traffic Count Consultants April &, May 1, 2008

10 In addition to the new machine counts and manual site access counts described previously, new manual peak period turning movement counts were performed at the SW Thistle Street/27 th Avenue SW intersection. The counts were performed from 6:30 to 8:30 A.M. and from 1:30 to 6:00 P.M. Counts performed in the surrounding area by the City of Seattle along SW Holden Street and SW Thistle Street were also obtained and utilized to determine existing traffic volumes. Figures and (attached) show the existing (2007) AM peak hour and school PM peak hour traffic volumes. These counts include traffic that is currently generated by both Denny Middle School and Chief Sealth High School with current enrollments of 630 students and 90 students, respectively. Future Street Traffic The Denny Middle School and Chief Sealth High School project is proposed to begin construction in late 2008 with both schools complete and occupied by the 2011/2012 school year. Therefore, to represent conditions when the project will likely be fully complete and occupied, year 2012 was selected for all future year analyses. To estimate future year-2012-traffic conditions without the proposed project, a compound annual growth rate was applied to existing traffic volumes at study area intersections. The growth rate was selected based on review of historical City of Seattle traffic count data in the study area. Traffic volumes along some streets including SW Thistle Street declined between 200 and Changes in traffic along other streets has been mixed increased in some directions but declined in others (e.g. northbound traffic on Delridge Way declined from 2002 to 2007, but increased in the southbound direction by between 1% and 1.% per year). For this analysis, traffic volumes were increased using a 1% compound annual growth rate to account for general background traffic increases and traffic from potential development in the area that could occur by This rate is consistent with rates approved for numerous other projects within the City of Seattle. The 1% annual growth rate was applied to existing 2007 volumes in order to estimate 2012 traffic volumes. Figures 6 and 7 (attached) show the forecast 2012-without-project traffic volumes for the AM peak hour and school PM peak hour, respectively Traffic Operations The quality of traffic flow and intersection operations are defined by levels of service (LOS). Levels of service are qualitative descriptions of traffic operating conditions and are designated with letters ranging from A, which is indicative of good operating conditions with little or no delay, to F, which is indicative of stop-and-go conditions with frequent and lengthy delay. Operating conditions of LOS D or better are acceptable within the City of Seattle. The existing traffic operating conditions in the study area were analyzed using the methodology outlined in the Highway Capacity Manual 2000 (Transportation Research Board, 2000). All level of service analyses were performed using the Synchro 6.0 analysis software, which is widely used by the City of Seattle for evaluating traffic operations. The existing and forecast 2012-without-project LOS analysis results are summarized in Table 3. As shown, all study area intersections currently operate at LOS A overall. However, turns from the outbound driveway onto SW Thistle Street operate at LOS F and are expected to continue operating at LOS F in 2012 without the project. This occurs because a large fraction of the peak hour school traffic and thru traffic on SW Thistle Street occurs in a short portion of the AM peak hour. This is common for school driveways where students arrive in the 1 to 20 minutes before school begins. In addition, the large volume of pedestrians that cross the driveway approach and SW Thistle Street at this location add delay to vehicles turning at the intersection. Similar conditions exist during the school PM peak hour, but since traffic volumes are lower, the delays are not as severe. -8- May 1, 2008

11 Table 3. Level of Service Summary Existing and 2012-Without-Project Unsignalized Intersection SW Kenyon St/26 th Ave SW (yield) 3 SW Holden St/26 th Ave SW (overall) Northbound from 26 th Avenue SW Westbound left from SW Holden St SW Kenyon St/27 th Ave SW (yield) 3 SW Thistle St/27 th Ave SW (overall) Southbound from 27 th Avenue SW Eastbound left from SW Thistle St SW Thistle St/West Access (overall) Southbound from West Access Eastbound left from SW Thistle St SW Thistle St/Dwy/26 th Ave SW (overall) Southbound from Dwy Northbound from 26 th Ave SW AM Peak Hour (7:00-8:00 A.M.) 2012 Existing (2007) Without Project LOS 1 Delay 2 LOS Delay A 7.7 A 7.7 A 1.8 A 1.8 B 12.1 B 12. A 1.3 A 1. A 7.3 A 7.3 A 1.2 A 1.2 B 1.9 B 1.0 A 1.2 A 1.2 A 0. A 0. B 1.1 B 1. A 0.2 A 0.2 C 16.6 C 17.7 F 77. F 8.6 C 19.1 C 19.6 SW Thistle St/Inbound Dwy (overall) Eastbound left from SW Thistle St A A A A Source: Heffron Transportation, Inc., November Level of service 2. Average seconds of delay per vehicle. 3. For uncontrolled intersections the yield control methodology was applied. School PM Peak Hour (2:00-3:00 P.M.) 2012 Existing (2007) Without Project LOS Delay LOS Delay A 7.9 A 8.0 A 1. A 1. B 11.7 B 11.8 A 0.3 A 0.3 A 7. A 7.6 A 2.0 A 1.9 B 12.7 B 12.8 A 0.9 A 0.8 A 0. A 0. C 23.8 D 2.2 A 0.2 A 0.2 A.3 A. C 2.2 D 2.2 D 32.8 E 3.3 A 0.8 A 0.7 A 1.1 A Safety Accident data for SW Thistle Street and SW Kenyon Street (the two east-west arterials most likely to be used by school traffic) were obtained from the City of Seattle Department of Transportation (SDOT). These data were examined to determine if there are any unusual traffic safety conditions that could affect or be impacted by the proposed project. Signalized intersections with 10 or more accidents per year and unsignalized intersections with five or more accidents per year are considered high accident locations by the City of Seattle. There are no specific standards for high accident locations with regard to roadway segment accident rates. The City of Seattle data reflecting the period between January 1, 200 and October 18, 2007 are summarized in Table. None of the intersections included in the data review met the criteria for high accident locations. One of the reported accidents (at SW Thistle Street/2 th Avenue SW) involved a vehicle striking a bicyclist or pedestrian. However, the data do not provide any contributing cause information for these accidents. Based on the accident data presented above, none of the other intersections or roadway segments appears to show unusual safety conditions. -9- May 1, 2008

12 Table. Intersection Accident Summary (January 1, 200 October 18, 2007) Fixed Rear- Side- Right Left Right Ped/ Total for Average/ Intersection Object End Swipe Turn Turn Angle Bike Other 3.8 Years Year SW Thistle/3 th Ave (signal) SW Thistle/Delridge Wy (signal) SW Kenyon/3 th Ave SW SW Thistle St/2 th Ave SW SW Thistle St/27 th Ave SW SW Thistle St/30 th Ave SW SW Kenyon/3 th Ave SW SW Thistle St/2 th Ave SW SW Thistle St/26 th Ave SW SW Thistle St/31 st Ave SW SW Thistle St/3 th Ave SW SW Kenyon/29 th Ave SW Fixed Rear- Side- Right Left Right Ped/ Total for Average/ Roadway Segment Object End Swipe Turn Turn Angle Bike Other 3.8 Years Year SW Thistle St Delridge Way SW to 22 nd Ave SW SW Thistle St 22 nd Ave SW to 2 th Ave SW SW Thistle St 2 th Ave SW to 2 th Ave SW SW Thistle St 2 th Ave SW to 26 th Ave SW SW Thistle St 26 th Ave SW to 27 th Ave SW SW Thistle St 27 th Ave SW to 28 th Ave SW SW Thistle St 3 th Ave SW to 3 th Ave SW SW Kenyon St 2 th Ave SW to 26 th Ave SW SW Kenyon St 26 th Ave SW to 27 th Ave SW SW Kenyon St 27 th Ave SW to 28 th Ave SW SW Kenyon St 29 th Ave SW to 30 th Ave SW Source: City of Seattle Department of Transportation, October One of these accidents resulted in a single fatality. 2. This accident involved a vehicle striking a bicyclist operating in a traffic way. 2.. School Parking Demand & Supply Based on field counts, there are 172 striped on-site parking spaces on the Chief Sealth High School site. In addition, there is room for between 20 and 2 additional vehicles on paved areas that are not striped for parking but that are commonly used for parking. Most of the unstriped parking is located west of the tennis courts and softball fields May 1, 2008

13 Parking demand counts were performed at the site in September Demand during mid-morning (9:30 A.M.) averaged 170 vehicles; demand in the afternoon (1:00 P.M.) averaged 160 vehicles. Based on observations of on-street parking conditions surrounding the site, nearly all of the schools parking demand during the school day is accommodated on site. A small amount of school-related parking demand likely occurs on 27 th Avenue SW and for short periods along SW Thistle Street. Overall, Chief Sealth High School s peak parking demand is 0.18 vehicles per student and occurs mid-morning. Parking demand for Denny Middle School is primarily accommodated by on-street parking surrounding the school. A small number of cars (about ) park on the site in areas not formally striped for parking. Therefore, total school parking demand was determined from counts of the limited onsite parking as well as on-street parking surrounding the school. On-street parking counts were performed with school in session in September 2007 and compared to summer conditions with no school. Based on these counts, school-related demand during mid-morning (9:30 A.M.) averaged 67 vehicles; demand in the afternoon (1:00 P.M.) averaged 62 vehicles. Overall, Denny Middle School generates an estimated parking demand of 1.03 vehicles per employee during mid-morning. This is slightly lower that the published parking demand rate for a middle school in Parking Generation. However, it is consistent with the current number of employees on the site (6 employees) and reflects about one vehicle per employee plus some additional vehicles of parents or volunteers. This slightly lower rate is expected for a school in an urban neighborhood with access to transit On-Street Parking Utilization Since some of the future school parking demand could occur off-site and along study area roadways, an on-street parking utilization study was performed. The study area for the on-street parking utilization study was determined based guidelines outlined in the City of Seattle s Client Assistance Memorandum (CAM) #117. Based on those guidelines, the on-street parking utilization study included all on-street parking within a 00-foot walking distance of the subject property. The property was defined by the project site s property boundaries. The site is a rectangular area bounded by SW Kenyon Street to the north, 27 th Avenue SW to the west, SW Thistle Street to the south, and by unimproved City right-of-way (2th Avenue SW alignment) and the Seattle Parks Longfellow Creek Greenspace to the east. Figure 8 (attached) shows the study area for the parking utilization study. On-Street Parking Supply The on-street parking supply within the study area was determined based on the methodology described in CAM #117. The study area described above was separated into individual block faces. A block face consists of one side of a street between two cross-streets. For example, the west side of 27 th Avenue SW between SW Thistle Street and SW Elmgrove Street is one block face (block face Y ). Each block face was then measured and analyzed to determine the number of available on-street parking spaces. First, all common street features such as driveways, fire hydrants, and special parking zones were noted. Second, certain distances adjacent to the common street features were noted. No on-street parking was assumed within 30 feet of a signalized or marked intersection, 20 feet of an uncontrolled intersection, 1 feet on either side of a fire hydrant, or five feet on either side of a driveway or alley. The remaining unobstructed lengths of street, between street features, were converted to legal on-street parking spaces using the following chart shown in Table. Institute of Transportation Engineers, 3 rd Edition, 200, LU May 1, 2008

14 Table. Number of Legal On-Street Parking Spaces Unobstructed Distance 0 1 feet feet 32 3 feet 69 feet feet feet feet feet feet feet feet Source: Number of Parking Spaces Unobstructed Distance feet feet 2 29 feet feet feet feet feet feet feet feet feet Number of Parking Spaces Unobstructed Distance feet 3 9 feet 0 71 feet feet feet 10 2 feet 26 7 feet 8 63 feet 6 8 feet feet feet Number of Parking Spaces City of Seattle, CAM #117. The numbers of parking spaces for unobstructed lengths over 319 feet were derived by Heffron Transportation using the City s methodology. Street features that were identified in the field that are not specifically addressed in CAM 117: Block faces C and D Along the southern 2/3 of 27 th Avenue SW, the pavement width is between 16 and 18 feet. There is also a to foot wide dirt shoulder. In general, for roadway widths between 20 and 28 feet, parking capacity is assumed on one side of the street so that adequate width is maintained for moving vehicles. Dense overgrowth on the northern portion of this street reduces the combined pavement and shoulder width to less than 20 feet and thus it was assumed to have no parking capacity. Block faces G, H It was observed that vehicles parked at an angle in the cul-de-sac on SW Chicago Court. An estimate of the supply was based on the observed angle parking instead of parallel parking measurements. Bock face M SW Kenyon Street dead-ends just east of 2 th Avenue SW. The dead-end falls within the study area but was not included in the supply. Block faces M, Q, Y There are curb cuts without driveways on these block faces. Based on discussions with City of Seattle DPD review staff (May 2007), curb cuts not currently serving an access can be considered as available for on-street parking. Block faces AE, AF Due to narrow pavement width (10 feet) and plant growth on the west side of the street, parking is allowed only on the east side of 26 th Avenue SW. On the east side of the street there is a gravel parking shoulder and wheel stops for angle parking. There are a total of 33 wheel stops within the supply area, however, due to a small planting island blocking access to five c-curb wheel stops and a fire hydrant within the study area, the number of available parking spaces was counted as 2 angle spaces. Block faces AH, AI There is a gravel parking shoulder with wheel stops on both sides of 26 th Avenue SW. However, the width of the gravel shoulders is not adequate for angle parking. It was observed that vehicles are parallel parked on the shoulder and the supply at this location was evaluated based on CAM 117 curb length measurements. Using the methodology described above, there are a total of 37 unrestricted on-street parking spaces within the study area. Along the three roadways that bound the site, there are 163 unrestricted on -12- May 1, 2008

15 street parking spaces (96 are located on the school s side of the streets; 67 are located on the opposite side of the street). In the evenings, an additional 12 use-restricted spaces (school-load only from 7:00 A.M. to :00 P.M.) are available along the north side of SW Thistle Street in front of the high school. On-Street Parking Demand On-street parking demand was surveyed within the study area for two weekday time periods 9:30 A.M., and 1:00 P.M. The weekday morning and midday surveys were performed to determine parking conditions during times when school is typically in session. Parking demand surveys were conducted on September 19 and 20, 2007 (Wednesday and Thursday). These days were selected to capture weekday parking demand on days with school in session. The results of the on-street parking surveys are summarized in Table 6. In addition, a parking demand count was conducted during a varsity football game Chief Sealth hosted Cleveland High School on Friday, October 12, This count was performed to document on-street parking demand in the study area during an evening with a varsity football game at the nearby Southwest Athletic Complex. Detailed count results of the on-street parking demand for each block face are attached. Table 6. Total On-Street Parking Demand Survey Results September 2007 Time Period Surveyed Morning, 9:30 A.M. Wednesday, September 19, 2007 Thursday, September 20, 2007 Average Midday, 1:00 P.M. Wednesday, September 19, 2007 Thursday, September 20, 2007 Average Evening With Football Game, 7:30 P.M. Friday, October 12, 2007 Source: Heffron Transportation, Inc., October, Parking Supply Total Number of Vehicles Parked % Utilization 13% 1% 13% 13% 13% 13% 2% On-street parking utilization was calculated using the methodology described in CAM #117. The City determines the on-street parking utilization rate as the average number of on-street parked vehicles divided by the number of legal on-street parking spaces within the study area. The on-street parking utilization within the study area during the school day time periods remained fairly consistent throughout the school day at 13%. Parking demand during the evening football game increased to about 2%. Most of the additional demand occurred at the south end of the study area near the athletic complex such as along SW Thistle Street Event Conditions As described previously, the existing Chief Sealth High School site includes an auditorium with seating for about 1,000 people, a gymnasium with bleacher seating for more than 2,100 people, and a little theater with seating for about 86 people. These facilities are used for a variety of events including interscholastic athletics, performing arts, and for community use such as youth and adult recreational sports and activities. According to the school s principal, the largest events occur during school-related winter and spring concerts, varsity basketball games, and open houses. Occasionally, -13- May 1, 2008

16 the facilities are rented for large community events. During these events, the on-site parking lots as well as adjacent on-street parking are typically used. The Southwest Sports Complex is located southwest of the project site across SW Thistle Street. The Southwest Sports Complex includes an artificial surface football/soccer field with a surrounding track and bleacher seating, softball and baseball fields, a multi-purpose field, parking for approximately 300 vehicles, and buildings for tickets, concessions, and restrooms. The Southwest Sports Complex serves as the home field for Chief Sealth High School athletics and also serves Denny Middle School and other schools in the District as well as Seattle Parks and Recreation Department activities. As described for the on-street parking analysis in the previous section, a parking demand count was conducted during a varsity football game Chief Sealth hosted Cleveland High School on Friday, October 12, In addition to the on-street parking demand counted, parking demand in lots was also counted. The counts were performed at 7:30 P.M. 30 minutes after the game started. A total of 26 vehicles were parked in the lots closest to the football field (71 in the Southwest Community Center lot and 17 in the larger southern lot). The Community Center lot was over capacity (with vehicles parking in undesignated areas). The larger southern lot was about 9% full. The on-site parking lots at Chief Sealth High School were also counted. The main lot and the western staff parking lot had a combined total of 30 vehicles (about 2% of their capacity). The northern lot was empty. The on-street parking conditions were described in the previous section. About 27 vehicles were parked along SW Thistle Street near the sports complex, but overall on-street parking utilization was about 2% during the football game. On-street parking beyond the study area defined in the previous section, was also counted during the Friday night event. Counts along the frontage of the Denny Middle School site (along SW Thistle Street, 30 th Avenue SW, SW Cloverdale Street, and 29 th Avenue SW) found very little demand 6 vehicles. These did not appear to be related to football game Transit The site vicinity is served by King County s Metro Transit bus service. Bus stops are located on both sides of SW Thistle Street at approximately 2 th Avenue SW. The stops are served by Route 22, which provides serves between Downtown Seattle and White Center through much of West Seattle. Route 22 operates seven days per week with 30-minute headways (time between consecutive buses) on weekdays. Less than ½ mile to the west at the Delridge Way/SW Kenyon Street intersection, Route 120 stops and provides service between Downtown Seattle and Burien. Beginning with the school year, bus transportation for Chief Sealth High School was changed. Instead of providing yellow school bus transportation, the District now provides eligible students with bus passes for use on regular Metro bus routes Non-Motorized Transportation Facilities As described in the Roadway Network section above, all roadways in the immediate site vicinity have sidewalks including those along the project site frontage. SW Thistle Street has marked and signed crosswalks located at the 32nd Avenue SW, 30th Avenue SW, and 26th Avenue SW/Chief Sealth High School. The crosswalk at 26th Avenue SW/Chief Sealth High School has been narrowed with curb bulbs and experiences the largest number of crossings before and after school. Based on observations at this crossing, the curb bulbs, signage, and crosswalk marking are effective and drivers were observed stopping for waiting pedestrians. Although this crosswalk seems to consolidate much of the pedestrian activity crossing SW Thistle Street, a large number of pedestrians were observed crossing at various points along the SW Thistle Street frontage of Chief Sealth High School. The crossing pedestrians -1- May 1, 2008

17 included students from Chief Sealth High School, Denny Middle School, and parents of students. As described previously, the historical accident data for the SW Thistle Street corridor did not indicate any reported pedestrian accidents. The King County Bicycling Map (King County and Group Health Cooperative, April 2006) identifies roadways by color as to their usefulness as a bicycling route and the type of bicycling facilities available on that roadway. None of the roadways adjacent to the site are highlighted on the map. However, the Seattle Bicycling Guidemap (City of Seattle, winter 2003) identifies SW Thistle Street as an arterial street commonly used by bicyclists. 3. Project Impacts The following sections describe the anticipated impacts to each element of the transportation system roadway network, traffic volumes, traffic operations, safety, parking, transit, and nonmotorized facilities Roadway Network The relocation of Denny Middle School to the north side of the Chief Sealth site would introduce a large amount of new traffic at the SW Kenyon Street/26 th Avenue SW/Access Driveway intersection. This intersection is currently uncontrolled (no stop signs are posted). With the project, it is likely that the City will require traffic control to be installed. The operations analysis assumed that the northsouth approaches would be controlled by stop signs and the east-west approaches would flow freely. This control arrangement would encourage inbound automobiles and buses to approach from the west using 27 th Avenue SW and SW Kenyon Street and help to reduce impacts along 26 th Avenue SW. The project would include a new one-way southbound service and bus loading/unloading lane along the eastern side of the site. It would have a right-turn only inbound driveway from SW Kenyon Street and a full-access exit onto SW Thistle Street. The service and bus drive would result in two new driveway curb cuts. The outbound driveway for the service/bus driveway onto SW Thistle Street would be located immediately east of the inbound driveway for the main parking lot and automobile drop-off/pick-up area. The close proximity of these driveways and the reverse direction orientation could lead to driver confusion. To minimize avoid driver confusion and prevent vehicles entering the wrong way on the bus exit lane, both driveways should be well marked and signed. Do Not Enter signs should be placed facing SW Thistle Street at the bus exit point. Parking entry signs and pavement parking should be included for the automobile entrance. Redevelopment of the Denny Middle School site would include construction of a new parking lot with about 180 spaces located at the southeast corner of the SW Thistle Street/30 th Avenue SW intersection. Access to the new lot would occur from two driveways on SW Thistle Street. There are existing curb cuts along SW Thistle Street that provide limited access for vehicles to the Denny Middle School site and a small amount of on-site parking. The new parking lot would increase the volume of traffic using access driveways in this area. No other changes to the existing roadway network would occur as part of the Denny site redevelopment Traffic Volumes The proposed project would construct a new middle school on the site and reconfigure on-site parking to serve both the relocated Denny Middle School and the renovated Chief Sealth High School. In addition, the potential for increased enrollment at both schools would also increase traffic volumes in -1- May 1, 2008

18 the area. Finally, the re-allocation of parking will shift some trips to on-street parking in the site area. This analysis documents how all of these changes would affect traffic volumes, operations, and parking in the site vicinity. Since Denny Middle School exists in the area to the southwest of the Chief Sealth site, the majority of its traffic already uses many local roadways and intersections. However, the relocation combined with the potential increased enrollment will generate new trips on the local roadways and intersections immediately surrounding the Chief Sealth site including along residential streets such as 26 th Avenue SW, 27 th Avenue SW, SW Kenyon Street, and 2 th Avenue SW. While the District cannot control the routes used by parent drivers arriving and departing the school area, it is recommended that the District encourage bus drivers to use SW Thistle Street, 27 th Avenue S, and SW Kenyon Street to minimize new impacts from bus traffic on local residential streets. Redevelopment of the Denny Middle School site would include construction of up to twelve tennis courts and a softball field. Since the softball field would replace one that would be lost at the Chief Sealth site, it is not expected to generate new traffic in the overall site area. The softball field would be used for District athletics similar to the existing field on the Chief Sealth site. Its new location would shift existing traffic from the Chief Sealth site south to the redeveloped Denny site. Six of the possible twelve tennis courts would replace courts that would also be lost on the Chief Sealth site. However, the additional six courts would likely result in increased users and a related increase in traffic generation in the area. Trip Generation for Proposed Project Vehicular traffic generation estimates for both schools were developed using the rates described previously in section 2.2 Traffic Volumes and the potential enrollment capacities for both proposed schools. Table 7 summarizes the trip generation estimates for the proposed schools. The trip generation for the existing schools and the resulting net change in traffic is also shown for each time period. Table 7. Future Traffic Generation Chief Sealth High School & Denny Middle School Period Chief Sealth High School 1 Enrollment In Out Total Enrollment Denny Middle School 2 In Out Total AM Peak Hour Proposed Schools 1, Existing Schools Net Change School PM Peak Hour Proposed Schools 1, Existing Schools Net Change Commuter PM Peak Hour Proposed Schools 1, Existing Schools Net Change Source: Heffron Transportation, Inc., November Trip generation determined from rates developed from counts performed at the school in September Trip generation determined using rates from ITE s Trip Generation, 7 th Ed, 2003, Middle School/Junior High School - LU Code May 1, 2008

19 In order to reduce the potential traffic volume impacts of both schools, the Seattle School District has committed to changing the start times of the schools. Currently, both schools have the same start and dismissal times 7:0 A.M. and 2:1 P.M., respectively. This results in all traffic for both schools arriving in the area at the same time and magnifying the traffic and pedestrian flows during these peak hours. After the project is complete, the District plans to start classes at Denny Middle School at 7: A.M. and start classes at Chief Sealth High School at 8:1 A.M. This change in schedules would separate the peak traffic flows to each school by a half hour and would better allow Chief Sealth students to access the site using Metro bus routes. The effect of the schedule change can be seen in Figure 9. As shown in red (dashed), if the two schools were to continue to operate with the same schedules, the peak period traffic flows would be much higher than with the half-hour separation between start times depicted in blue (solid) and proposed by the District. Figure 9. Total Site Traffic from Both Schools With Existing and Proposed Start Times 00 0 Peak traffic for future site traffic with current start times 00 Traffic Volume (vehicles) Peak traffic for future site traffic with proposed start times :30 A 6: A 7:00 A 7:1 A 7:30 A 7: A 8:00 A 8:1 A 1:30 P 1: P 2:00 P 2:1 P 2:30 P 2: P 3:00 P 3:1 P 3:30 P Morning and Afternoon Peak Periods (1-minute period begin) Source: Heffron Transportation, Inc., 2007 The change in start times would also shift the time of the peak hours for the overall site by fifteen minutes. Instead of occurring from 7:00 to 8:00 A.M., the morning peak hour would occur from 7:1 to 8:1 A.M.; the afternoon peak hour would occur from 2:1 to 3:1 P.M. instead of from 2:00 to 3:00 P.M. The total combined site traffic generation for both schools was determined based on the proposed schedules and the shift in the overall site s peak hour. Since Chief Sealth High School is remaining in its current location, only the net change in traffic was considered. Since Denny Middle School is relocating to this site, all of the school s traffic was considered new to the site access and the local roadways in the immediate site vicinity. The resulting net increases in school traffic for each peak hour are summarized in Table May 1, 2008

20 Table 8. Future Net Increases in Site Traffic With Proposed Schedule Change Period In Chief Sealth High School Out Total In Denny Middle School AM Peak Hour School PM Peak Hour Source: Heffron Transportation, Inc., November 2007 Out Total Since the softball field is planned to be used for District athletics, it would most often be used by students of Chief Sealth High School. Softball season occurs in spring and typically extends from late February to early May. During this period, there are typically daily practices and about eight home games that could attract a small number of spectators. The relocated softball field would shift the existing activities from the north side of the Chief Sealth site to the redeveloped Denny site. Overall, the softball field would not generate new traffic in the site vicinity. Trip generation estimates for the tennis courts at the redeveloped Denny site were estimated using rates and equations in Trip Generation (Land Use 90). On days with good weather, the proposed tennis courts could generate about 20 AM peak hour trips, and about 7 PM peak hour trips. Half of these trips (10 AM, and 2 PM) would be new the site vicinity since six of the courts would be new to the area (six of the twelve would replace existing courts that would lost as part of redevelopment of the Chief Sealth site). Traffic destined to the new tennis courts is expected to use the new parking area proposed at the northwest corner of the Denny site. The courts would be actively used for Chief Sealth tennis team activities, which occur on weekday afternoons (typically at 3:00 P.M.) during spring (typically on about six or seven weekdays in March and April) Traffic Assignment The changes in traffic described in the previous section were assigned to the site access driveways and the adjacent roadways. The distribution of trips was based on the proposed access configuration, on-site and on-street parking supply, and the existing local access patterns. As described previously, the location and use of on-site parking will be rearranged on the site. The on-site parking for Chief Sealth High School will be limited to the southern side of the site and access from SW Thistle Street. Total on-site parking available to Chief Sealth students and staff would be reduced from about 172 striped spaces to 11 spaces. As a result, excess parking demand is expected to occur along adjacent streets with most occurring along both sides of 27 th Avenue SW. Details regarding parking impacts are presented later in this memorandum. Denny Middle School will have an on-site parking lot with 60 spaces and an automobile loading/unloading area accessed from SW Kenyon Street. Some automobile loading/unloading may also occur from the adjacent streets such as 27 th Avenue SW and SW Kenyon Street. However, to represent worst-case conditions for local traffic operations, all site traffic was assigned to the access driveway opposite 26 th Avenue SW. Bus loading/unloading for Denny Middle School (expected to include 11 full-sized buses and six to eight half-sized special-needs buses) would occur on site with buses arriving from SW Kenyon Street and exiting southbound onto SW Thistle Street. The resulting net change in traffic volumes at the access driveways and the adjacent roadways and intersections due to the project are shown in Figures 10 and 11 (attached). These figures reflect the total net changes in traffic including shifts associated with the relocated Denny Middle School and the added enrollment capacities of both schools. As shown, although the existing schools are accessed primarily from SW Thistle Street, the new location of Denny Middle School would likely result in more trips arriving -18- May 1, 2008

21 from SW Holden Street. The assignments reflect this likelihood. The project traffic assignments were added to 2012 without-project traffic forecasts described previously to represent year 2012 conditions with the proposed project. Users of the tennis courts who drive to the site are expected to park in the new parking lot that would be accessed from two driveways on SW Thistle Street east of 30 th Avenue SW. Spectators and participants at the softball field are expected to use the adjacent athletic complex parking lot and the existing access onto SW Thistle Street east of the Southwest Community Center. 3.. Traffic Operations Level of service analysis was performed for conditions with the redeveloped schools. As described in section 3.1 Roadway Network, it was assumed that traffic control would be installed at the SW Kenyon Street/26 th Avenue SW/Site Access intersection. It was assumed that stop signs would be placed on the north and south approaches of the intersection. This would serve to focus the desired traffic patterns and discourage use of 26 th Avenue SW as a primary route to the schools. The results of the LOS analysis are presented in Table 9. As shown, relocating Denny Middle School and increasing the enrollment capacity of both schools would degrade operations of the site access intersection with SW Kenyon Street opposite 26 th Avenue SW. This intersection serves relatively light volumes currently, but would serve nearly all of the schools vehicular traffic with the project. While it would operate at an overall LOS C, delays and queues leaving the site during morning and afternoon periods could result in more parents picking up and dropping off from local on-street parking. This is common at many schools throughout Seattle. The added thru traffic on SW Thistle Street combined with the potential for additional pedestrian crossings would further degrade operations of the Chief Sealth parking lot egress opposite 26 th Avenue SW. Although this intersection would operate at LOS F in the AM peak hour with or without the project, delays would increase somewhat with the increase in enrollment capacity. The impacts shown are partially mitigated by the assumed change in school schedules and the relocation of Denny Middle School to the north. Both of these actions would result in slightly lower through volumes on SW Thistle Street and improved peaking characteristics compared to conditions with the project and current school schedules. Delays at the two intersections along 27 th Avenue SW would also increase with the project. This is expected since the schools would increasingly rely on this street for access and parking capacity. However, these intersections are expected to operate at LOS D or better during both AM and school PM peak hour conditions. The increases in morning and afternoon traffic along 26 th Avenue SW also would add delay at the SW Holden Street intersection. However, all movements are expected to operate at LOS C or better during both peak hours. Overall, the project would add delay to several locations during the morning and afternoon peak hours. The largest increases in delay would affect drivers leaving the school site onto SW Kenyon Street and SW Thistle Street. Delays at these access points would be similar to conditions at many school access points during morning and afternoon periods. Delays to other locations would not represent significant adverse impacts. However, some measures are recommended to minimize the potential for schoolrelated traffic to impact residential streets. These are outlined in the Mitigation section May 1, 2008

22 Table 9. Level of Service Summary 2012-Without and With Project Unsignalized Intersection SW Kenyon St/26 th Ave SW 3 Northbound from Site Southbound from 26 th Avenue SW Westbound Left from SW Kenyon St SW Holden St/26 th Ave SW (overall) Northbound from 26 th Avenue SW Westbound left from SW Holden St SW Kenyon St/27 th Ave SW (yield) 3 SW Thistle St/27 th Ave SW (overall) Southbound from 27 th Avenue SW Eastbound left from SW Thistle St SW Thistle St/West Access (overall) Southbound from West Access Eastbound left from SW Thistle St SW Thistle St/Dwy/26 th Ave SW (overall) Southbound from Dwy Northbound from 26 th Ave SW SW Thistle St/Inbound Dwy (overall) Eastbound left from SW Thistle St SW Thistle St/Bus Exit (overall) Southbound turns from Access Dwy AM Peak Hour Without Project With Project LOS 1 Delay 2 LOS Delay A 7.7 C 16.9 A 8.1 E 38.2 A 7. B 13.6 A 7. A 2. A 1.8 A.2 B 12. C 19.1 A 1. A 2.8 A 7.3 C 1.3 A 1.2 A 7.9 B 1.0 D 26.1 A 1.2 A.0 A 0. A 0. B 1. B 1.0 A 0.2 A 0.2 C 17.7 D 26.3 F 8.6 F C 19.6 C 19. A 1.3 A 1.0 A 2.2 A 2.0 A 1.0 C 23.3 School PM Peak Hour Without Project With Project LOS Delay LOS Delay A 8.0 C 19.0 A 8.2 E 38.9 A 7.7 C 1. A 8.0 A 6.9 A 1. A.8 B 11.8 C 1.2 A 0.3 A 1.6 A 7.6 A 9.3 A 1.9 A 7.6 B 12.8 C 20.8 A 0.8 A 3.3 A 0. A 0. D 2.2 B 13. A 0.2 A 0.1 A. A 8.2 D 2.2 D 32. E 3.3 E 7. A 0.7 A 0.8 A 1.1 A 1.3 Source: Heffron Transportation, Inc., November Level of service 2. Average seconds of delay per vehicle. 3. Assumed traffic control would be installed with the project to include stop signs on the north and south approaches. A 0.9 C 18.1 Traffic operations were also evaluated at the driveways that would provide access to parking for the redeveloped Denny site. All movements at the driveways are expected to operate at LOS B or better during typical morning and afternoon peak hours. 3.. Safety The proposed project would result in additional turning movements entering and leaving SW Thistle Street at 27 th Avenue SW, the Chief Sealth access driveways, and the new bus egress. Similarly, the project would increase turning movements to and from 26 th Avenue SW at SW Holden Street. Although the increase in turning movements could result in a proportionate increase in accident experience, neither of these roadway corridors appear to have unusual safety patterns that would adversely affected by the expected increase in traffic May 1, 2008

23 3.6. Parking Demand and Supply Parking demand for the total project was determined using the rates developed for each school and presented previously in section 2. School Parking Demand & Supply. The potential for increased enrollment and employees at both schools was considered in the future parking demand estimates. Mid-morning parking demand for Chief Sealth High School is expected to increase from about 170 vehicles to about 21 vehicles with the full 1,200 student enrollment. Mid-morning parking demand for Denny Middle School is expected to increase from 67 vehicles to 7 or 80 vehicles depending on the future staffing levels of the school. Total mid-morning parking demand on an average day would be about 29 vehicles for both schools. A total of 17 on-site parking spaces are planned for the project 60 for Denny Middle School and 11 for Chief Sealth High School. As a result, about 120 vehicles would spill over most likely to nearby on-street parking. As described in section 2.6 On-Street Parking Utilization, there are a total of 37 unrestricted onstreet parking spaces within the study area that are typically about 13% occupied during school days. In addition, along the three roadways that bound the site, there are 163 unrestricted on-street parking spaces (96 are located on the school s side of the streets; 67 are located on the opposite side of the street) that are typically about 8% occupied. Therefore, the existing on-street parking utilization conditions indicate that the parking overspill can be accommodated on-street on the roadways surrounding the project site. With the potential overspill of 120 vehicles all occurring on the three surrounding streets (27 th Avenue SW, SW Kenyon Street, and SW Thistle Street), parking utilization on these three streets could increase to 80%. However, parking utilization in the larger parking study area (00-foot walking distance commonly studied for similar projects) would be about 6%. The 180 parking spaces proposed at the redeveloped Denny site would replace parking that would be lost to the new softball field on the southwest corner of the existing athletic complex parking lot. As a result, the new lot is expected to be used when there are large events, such as high school football games, track meets, or other sports tournaments at the athletic complex. However, on most days, the lot will likely remain nearly empty. This is similar to conditions observed at the existing parking lot adjacent to the Southwest Athletic Complex. The lot would be used and would easily accommodate demand generated by the new tennis courts. The lot may also be used by visitors to the Southwest Community Center. The relocation of approximately 60% (180 of 300 total spaces) of the Southwest Athletic Complex parking to the northwest corner of the Denny site would likely have some effect on how the parking is used for larger events at the athletic complex and in the site vicinity. Some of the new parking would be farther away from the entrance to the athletic complex than the spaces that they would replace. Drivers may be more likely to park closer by using on-street spaces along SW Thistle Street and along 27 th and 28 th Avenues SW, than they might with the current parking supply arrangement. In addition, some of the proposed parking on the Denny site would be about 200 feet farther from the Chief Sealth High School site. This would reduce the attractiveness of the lot for overflow parking at the high school during large events such as basketball or performing arts. Based on parking demand observations conducted during a Chief Sealth High School football game at the athletic complex, there is on-street parking capacity to accommodate the additional demand. However, some measures could be considered to reduce parking impacts to on-street spaces and increase use of the off-street parking lots. The suggested measures are outlined in the Summary and Mitigation section of this memorandum Event Conditions The proposed project would maintain the existing event capacity at Chief Sealth High School. The gymnasium, auditorium, and little theater would have the same seating capacity as currently exists May 1, 2008

24 As a result, traffic and parking conditions with events at Chief Sealth are not expected to increase in magnitude. However, the renovation project would likely improve the facilities and make them more desirable for more frequent use. As a result, the frequency of events could increase with the project. In addition, the proposed Denny Middle School relocation to the site would add another assembly space that could also be used for events. Due to the potential for increased event frequency and the overall increase in assembly space, it is recommended that the District require both schools to coordinate event schedules (for both scholastic and community use) and ensure that only one large event be held at the site at any one time. In addition, for large events, it is recommended that the schools ensure that all on-site parking lots (at both schools) are open and available for use and that attendees are notified that off-street event parking is available in the parking lot adjacent to the Southwest Sports Complex south of SW Thistle Street Transit As described previously, the site vicinity and Chief Sealth students are served by King County s Metro Transit bus service. In the future with the project, King County Metro Transit is expected to continue providing transportation service for Chief Sealth High School students. This action would occur with or without the proposed project. The increase in enrollment at Chief Sealth may increase transit ridership. The additional passenger demand from the project is not expected to adversely affect transit service Non-Motorized Transportation Facilities The highest volume of pedestrian crossings occurs on SW Thistle Street at the schools outbound driveway opposite 26 th Avenue SW. Pedestrian volumes are very heavy just prior to the start of school and just after school is dismissed. The new location of Denny Middle School together with potential increases in school enrollment capacity would likely increase pedestrian crossings at this and other crossing locations along SW Thistle Street. The District has indicated that Denny Middle School students would not be required to cross SW Thistle Street during the school day to participate in Physical Education (PE) classes. Rather, those classes would be taught in the gymnasium or on the multipurpose playfield planned at the northeast corner of the site. However, after-school activities, such as those occurring at the Southwest Community Center or Southwest Sports Complex, could result in new pedestrian crossings that do not currently occur. While the current crossing appears to be functioning effectively, a variety of measures could be considered to further enhance safety and visibility of the crossing. Measures such as flashing beacons, overhead signage and lighting, establishment of a school speed zone, and possibly a pedestrian actuated traffic signal could be considered. For a pedestrian actuated signal, the City of Seattle typically requires that locations meet minimum warrant requirements outlined in the Manual on Uniform Traffic Control Devices (MUTCD) and in the Seattle Department of Transportation (SDOT) Director s Rule Based on the current and forecast future traffic conditions along SW Thistle Street, the crossing would not likely meet the minimum warrants for a pedestrian actuated signal. However, the other measures to improve visibility and signage at the crossing would be beneficial. Pedestrian signage and crosswalk locations should also be identified on SW Kenyon Street at the proposed main access to Denny Middle School. This access will be the focal point for vehicular traffic MUTCD, Federal Highway Administration, 2003 Edition 6 Seattle Transportation Department, SMC (N); May 1, 2008

25 at the school and volume passing through the intersection will increase compared to current conditions. Signage, crosswalks, and school speed zones could be included at this location. In addition, if required as part of the construction processes, the project may reconstruct the damaged segments of sidewalk along the site frontage Construction Activities Construction activities on the Chief Sealth site are planned to begin in June 2008 and extend through fall/winger The most noticeable construction activity in terms of transportation-related elements will likely be related to the import and export of material to and from the site. Some existing site features (such as portables, selected site stairs, parking lots, tennis courts, and softball field) will be demolished and material will be removed from the site. There would also be some earthwork activities (cut and fill) at the site. The project would require excavation and export of approximately 12,000 cubic yards of soil and import of approximately 1,000 cubic yards of fill soil. In total, the demolition and earthwork would result in movement of about 27,000 total cy of material. Assuming an average of 18-cubic yards per truck and about three months for the demolition and earthwork efforts, this activity will generate approximately 12 truck loads per week. With five days per week and typical construction hours, this would equate to between 3 and truckloads per hour (6 to 8 truck trips per hour with a truck in and out for each load). Trucks are expected to arrive at the Chief Sealth site from the east on SW Thistle Street, turn north on 27 th Avenue SW, and enter the site from SW Kenyon Street. Trucks leaving the site are expected to exit onto SW Thistle Street east toward Delridge Way SW. While this activity will likely be noticeable to drivers and residents along nearby roadways, it would occur for a relatively short period and would not result in significant adverse impacts to traffic operations or capacity. Construction employee traffic and parking would be accommodated either on-site or on-street along the site frontage. Construction activities on the Denny Middle School site are planned to begin in summer 2011 and be complete by spring of As with the Chief Sealth site, the most noticeable construction activity in terms of transportation-related elements will be the import and export of material to and from the site. The existing Denny Middle School buildings will be demolished and material will be removed from the site. It is estimated that about 11,600 yards of building demolition debris would be removed. Most of the debris is expected to be removed using 100-yard containers, requiring about 112 loads. A small portion of the debris (about 00 yards) would be hazardous (asbestos) and would be removed in smaller 0-yard containers. In total, the demolition is expected to require about 122 loads and would take about six weeks. This would equate to roughly loads (8 truck trips) per day. After demolition, there would also be earthwork activities (cut and fill) at the site as part of the grading required to develop the tennis courts and parking area. The Denny site redevelopment would require excavation and export of approximately 18,000 cubic yards of soil and import of approximately 1,000 cubic yards of fill soil. In total, the earthwork would result in movement of about 32,000 total cy of material. Assuming an average of 18-cubic yards per truck and about six weeks for the earthwork efforts, this activity will generate approximately 300 truck loads per week. With five days per week and typical construction hours, this would equate to between 7 and 8 truckloads per hour (1 to 16 truck trips per hour with a truck in and out for each load). Trucks are expected to arrive at the Denny site from the southeast using Trenton Street and 29 th Avenue SW. Exiting trucks are expected to exit the Denny site onto SW Thistle Street and head east back to Delridge Way. The demolition and site grading activity will be noticeable to drivers and residents along nearby roadways. However, it would occur for a relatively short period (about six weeks for demolition and about six weeks for site grading activities) in the summer months of 2011 and would not result in significant adverse impacts to traffic operations or capacity May 1, 2008

26 A construction management plan (CMP) should be developed for both the Chief Sealth site and the Denny site to identify site access measures, truck haul routes, construction and hauling schedules, and parking plans that minimize impacts to nearby residential streets. Where practical, haul routes should be focused to arterial streets and away from residential streets. The plan should identify and address temporary lane and sidewalk closures as well as bus-stop relocations, if any are required.. Summary and Mitigation The following summarizes the impacts described above and recommends measures to minimize the impacts of the school project on transportation and parking in the site area: The project would construct one new egress driveway onto SW Thistle Street and one new ingress driveway on SW Kenyon Street to serve the service/bus drive. Recommendations: 1. To minimize/avoid driver confusion and prevent vehicles entering the wrong way on the bus exit lane, both driveways should be well marked and signed. Do Not Enter signs should be placed facing SW Thistle Street at the bus exit point. Parking entry signs and pavement parking should be included for the automobile entrance. 2. Work with SDOT to control the SW Kenyon Street/26 th Avenue SW/Site Access intersection. It is recommended that stop signs be placed on the northbound and southbound approaches to this intersection. The proposed project would result in a net increase in overall traffic volumes generated at the site compared to existing conditions. However, the project is not expected to result in significant adverse impacts to traffic operations at the site access or nearby off-site intersections. The project would add new traffic to SW Kenyon Street, 27 th Avenue SW, and 26 th Avenue SW with the relocation of Denny Middle School to the site. However, these roadways would continue to operate at acceptable levels of service with the project. Similar to most schools, parent pick-up and drop-off at the site will likely result in noticeable congestion and delay at site access driveways, within parking lots, and at pickup/drop-off areas during times just before and after school. As a result, parking conditions on the site and along nearby roadways are expected to be congested during those times. Recommendations: 3. Encourage bus drivers to arrive at the site using SW Thistle Street, 27 th Avenue S, and SW Kenyon Street to minimize new impacts from bus traffic on local residential streets.. In the first year of operation and each September thereafter, review on-site parking, site access, pick-up/drop-off activities and bus loading operations and determine if changes are desired. Changes that could be considered include: a. Notifying parents through school newsletters or other media about appropriate locations for student drop-off and pick-up. Parents should be reminded regularly not to park in bus loading areas or block crosswalks. b. Using school staff or volunteers in the parking lots during arrival and dismissal times to assist children and parents with arrival and departure and to help reduce vehicular/pedestrian conflicts. -2- May 1, 2008

27 The proposed project would result in an increase in typical weekday peak parking demand at the site. An estimated 120 vehicles could be required to find parking off-site during typical peak weekday demand times. All of the excess demand is expected to be accommodated by nearby on-street parking and the on-street supply within 00 feet of site would accommodate the excess demand while remaining at less than 0% utilized. Recommendations:. Develop an agreement between Denny Middle School and Chief Sealth High School to avoid scheduling events with large attendance on the same day/evening. On days/evenings with large events, all on-site parking should be made available to attendees and participants. 6. For large events, provide signage or other notification that off-street parking is available in the large parking lot adjacent to the Southwest Sports Complex. The new location of Denny Middle School together with potential increases in school enrollment capacity would likely increase pedestrian crossings at this and other crossing locations along SW Thistle Street. Recommendations: 7. Work with SDOT to define measures to improve visibility and signage at the SW Thistle Street crossing. These could include flashing beacons, overhead signage and lighting, and/or establishment of a school speed zone. 8. Pedestrian signage and crosswalk locations should also be identified on SW Kenyon Street at the proposed main access to Denny Middle School. Signage, crosswalks, and school speed zones could be included at this location. 9. If required, reconstruct damaged segments of sidewalk along the site frontage. Redevelopment of the Denny Middle School site and relocation of about 180 parking spaces from the Southwest Athletic Complex parking lot to the northwest corner of the Denny site could result in increased use of on-street parking capacity during large events at the athletic complex. It would also provide less convenient off-street parking for use as overflow capacity during large events at Chief Sealth High School. Recommendation: 10. Work with the Southwest Community Center to share parking during large events at the athletic complex. The proposed western lot may provide more reliable capacity for the community center during large events, while the eastern lot (currently used by the community center) could be better suited for the athletic facility. Signage and other notification could be used to direct drivers to the appropriate parking locations for each of the uses during events at the athletic complex, Chief Sealth High School, and the community center. Drivers could be encouraged, through District communications, to use the off-street lots instead of on-street parking in the residential neighborhood. -2- May 1, 2008

28 Construction activities such as demolition and hauling, material deliveries, and earthwork would generate a noticeable amount of truck traffic. Recommendation: 11. Prepare construction management plans (CMP) for both the Chief Sealth and Denny sites to identify site access measures, truck haul routes, construction and hauling schedules that minimize impacts to local residential areas. The plan should identify and address temporary lane and sidewalk closures as well as bus-stop relocations, if any are required. Attachments: Figure 1. Proposed Site Plan Figure 2. Proposed Site Plan Denny Site Figure. Existing (2007) AM Peak Hour Traffic Volumes Figure. Existing (2007) School PM Peak Hour Traffic Volumes Figure 6. Forecast 2012 Without Project AM Peak Hour Traffic Volumes Figure 7. Forecast 2012 Without Project School PM Peak Hour Traffic Volumes Figure 8. On-Street Parking Utilization Study Area Figure 10. AM Peak Hour Net Project Traffic Assignment Figure 11. School PM Peak Hour Net Project Traffic Assignment Parking Utilization Summary by Block Face TSM/tsm Denny-Sealth Schools - Transportation Impact Analysis - REV FINAL -26- May 1, 2008

29 93 N Source: Bassetti Architects, October 28, 2007 Denny Middle School and Figure 1 Chief Sealth High School Redevelopment Project Proposed Site Plan