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TECHNICAL MEMORANDUM
Project: Renton School District’s Hazen High School Portables Placement
Subject: Transportation Analysis
Date: March 1, 2023
Author: Tod S. McBryan, P.E.
This memorandum summarized the transportation and parking analyses for the proposed placement of
portable classrooms at Hazen High School. Please contact Tod McBryan at (206) 527-8410 with any
questions regarding this memorandum.
1. Project Description
1.1. Site Description
Hazen High School is located at 1101 Hoquiam Avenue NE in Renton and the site is comprised of nine
parcels that total over 33 acres in size; the area of improvements is located on parcel #1023059278, which
is 4.10 acres in size. The overall site is bounded by Hoquiam Avenue NE on the east, NE 10th Street on
the south, Duvall Avenue NE and private residential parcels on the west, and City of Renton (City) and
private residential parcels on the north. Figure 1 shows the site location and vicinity.
1.2. Project Proposal
Hazen High School was last expanded in 2011; after the classroom addition it had listed capacity of 1,643
students.1 However, in response to student-teacher ratio reduction requirements (class-size reductions) in
2017, the school’s reported capacity was reduced and is currently listed at 1,462 students;2 however, the
school has had higher enrollment levels for the past several years—averaging 1,650 students during the
2021-22 school year.3 To temporarily address the existing over-enrollment capacity need, the RSD
proposes to place four (4) portable buildings with two classrooms each (for a total of 8 new classrooms)
on the Hazen High School site. Each added portable classroom is assumed to accommodate an average of
29 students—the target capacity for RSD high schools. With the added portables, the school capacity
would increase by 232 students from 1,462 to 1,694 students. This future capacity is expected to
accommodate the anticipated future average enrollment at the school. No increase in the number of
employees (155) is anticipated.
All four of the portable buildings would be placed in the northern-most parking lot, which would displace
and make unavailable 51 parking stalls. The portable placement project is planned for summer 2023 with
occupancy expected by fall 2023. Figure 2 shows the site plan with the proposed locations of the
portables and the parking that would be made unavailable.
1 Renton School District, Capital Facilities Plans, 2011-2016.
2 Renton School District, 2022 Capital Facilities Plan, June 2022.
3 Renton School District enrollment data. Reflects average of October and June enrollment levels for each year since number
of students in high schools typically declines over course of the year.
Renton School District’s Hazen High School
Portables Placement – Transportation Analysis
March 1, 2023 | 2
Figure 1. Site Location and Vicinity
Source: Google Earth, February 2023. Annotations by Heffron Transportation, Inc.
Figure 2
Site Plan with Proposed Portable Locations
Source: Greene-GasawayArchitects, February 23, 2023.
Project Area
1023059278
Renton School District
Hazen High School
Portable Placements
N
Renton School District’s Hazen High School
Portables Placement – Transportation Analysis
March 1, 2023 | 4
2. School Trip Generation
As outlined in City’s Traffic Impact Analysis Policy Guidelines for New Development,4 the City requires
trip generation estimates for development projects be derived using rates and equations in the most
current edition of the Institute of Transportation Engineers’ [ITE] Trip Generation Manual.5 For High
Schools (Land Use Code 525), the current edition provides rates and equations based on either number of
students or number of employees. Because the proposed project would influence the student capacity with
no expected changes to employees, rates and equations based on students were selected for this analysis.
As described, the proposed project involves placement of four double portables that would increase
school capacity to 1,694 students. The project would also include minor parking lot paving repairs, but no
other changes. Table 1 summarizes the forecast trip generation for Hazen High School with the added
capacity provided by the portable classrooms. The trip estimates for the added portables are compared to
its listed capacity at the time of the last permitted classroom addition in 2011—1,643 students, since that
is the level of enrollment assumed for previous SEPA review and permitting by the City. As shown,
compared to its previously-permitted capacity level, the portable placement project is forecast to result in
net increases of about 100 trips per day, 17 morning peak hour trips, 12 afternoon peak hour trips, and 7
PM peak hour trips. As noted, the proposed portables are planned to address an existing condition and
trips being generated by the school on surrounding roadways already effectively reflect enrollment at the
future capacity level.
Table 1. Trip Generation Estimates – Hazen High School With Portables
Capacity
AM Peak Hour
(6:30 to 7:30 A.M.)
Afternoon Peak Hour
(2:00 to 3:00 P.M.)
PM Peak Hour
(4:00 to 5:00 P.M.)
Site Condition (Students) Daily In Out Total In Out Total In Out Total
School with Portables 1 1,694 3,286 546 257 803 161 343 504 114 123 237
Existing School 2 1,643 3,187 534 252 786 157 335 492 110 120 230
Net Change 51 99 12 5 17 4 8 12 4 3 7
Source: Heffron Transportation, Inc., February 2023 using rates published for High Schools (Land Use 525) in ITE’s Trip Generation Manual,
11th Edition, Sept. 2021.
1. Capacity of Hazen High School with eight (8) portable classrooms added and reflecting class-size reductions in place since 2017.
2. Capacity of Hazen High School, 2011 Capital Facilities Plan, 2011.
3. Parking Analysis
3.1. Supply and Code Requirements
Based on counts and observations conducted at the site in February 2023, the existing school site has a
total of 465 striped parking stalls located in six separate areas on campus as listed below:
117 stalls in the northwestern lot between the school building and the baseball field;
101 stalls north of the school buildings;
62 stalls in the staff and visitor lot east of the main school building;
46 stalls in the lot south of Hazen Pool building;
86 stalls in the student lot south of the main school building; and
53 stalls in the south lot adjacent to the tennis courts (excludes one stall occupied by shed).
4 City of Renton, 2020.
5 ITE, 11th Edition, September 2021.
Renton School District’s Hazen High School
Portables Placement – Transportation Analysis
March 1, 2023 | 5
The above values exclude unstriped parking that occurs adjacent to the service/delivery area. The
portable-placement project would make unavailable the northerly three rows of parking (51 stalls) in the
north lot. The south two rows of parking in that lot would remain with minor re-striping to create a
pedestrian access path, but would maintain the same number of stalls (33 stalls) by converting them to
compact. At project completion, the entire site would have a total of 414 parking stalls.
The Renton Municipal Code (RMP) §4-4-080.F.10.d outlines the parking requirements for a variety of
land uses, including high schools. The City requires a minimum of 1 parking stall per employee plus 1
stall for every 10 students. With the portables in place, the school is expected to have the same number of
employees (155) and would have capacity for up to 1,694 students. Based on these values, the City would
require a minimum of 325 parking stalls (155 + (1,694 ÷ 10)). The parking supply that would remain after
the portable placement would meet the City code requirement.
3.2. Typical School-Day Demand
Parking demand counts were performed at the existing school on Wednesday, February 8, 2023 at 9:00
A.M. and at 12:30 P.M. These counts found a total of 341 parked vehicles in the mid-morning and 370
parked in the early afternoon. It is noted that 61 stalls (including 35 in the lot south of the Hazen Pool
building and 26 stalls in the student lot south of the main building) were unavailable during the school-
day counts due to temporary construction fencing. Based on these counts and current enrollment levels,
the existing school generates parking demand of about 0.20 to 0.21 vehicles per student. For comparison,
demand counts were performed using aerial images of Hazen High School from May 2017 and May
2019. Those counts found a total of 394 and 336 vehicles parked on site, which correspond to rates of
0.24- and 0.20-vehicles-per-student for 2017 and 2019, respectively.6 Based on the range of parking
demand rates derived specifically for Hazen High School, which already account for the target level of
enrollment, the on-site parking supply of 414 stalls that would remain after portable placement would
continue to accommodate the typical school-day parking demand.
4. Summary and Conclusions
Compared to its previously-permitted capacity level, the portable placement project is forecast to result in
net increases of about 100 trips per day, 17 morning peak hour trips, 12 afternoon peak hour trips, and 7
PM peak hour trips. However, the portable placement project is not expected to change the school’s
current trip generation or parking demand levels because the school is already enrolled to the level that
would be accommodated by the site with portables. The modified parking supply of 414 stalls would
continue to meet the City’s minimum code requirement for parking, and accommodate the observed
school-day parking demand.
TSM/tsm
RSD HHS Portables Placement Transportation Memo_FINAL
6 Based on enrollment of 1,618 students reported for 2017 and 1,706 students in 2019, Office of Superintendent of Public
Instruction (OSPI), Report Card Enrollment Data for the beginning of each school year.