Dear Port of Seattle Commission,

We’re requesting the Port of Seattle make a procedural change in how the data from your system of port owned Larson Davis

831 noise monitors is collected and retained. This is particularly timely given that the contract with the vendor who provides

services associated with the monitors, L3Harris, is due for renewal as per Item 6e in today’s commission meeting.

Currently the Port does not retain the raw second by second measured sound level data but instead contracts the data

monitor, which is tiny by today’s standards.

At the UC Davis Aviation Noise & Emissions Symposium in March I spoke with L3Harris, who was a sponsoring vendor and had

a booth there. Samuel Carter, their Training & Solutions Manager, indicated it would be a simple modification of the

procedure to deliver the raw data with the processed results. The Port simply has to request it. I didn’t ask, nor did he say, if

there would be an extra cost for that. However, again, this is Port owned data on Port owned noise monitors so the Port can

simply download this data themselves periodically before L3Harris purges it.

This raw data is absolutely essential for any rigorous analysis of the aviation noise levels at the site. As a real-world example, I

was looking over the processed data from last December and came across an interesting anomaly. Here is a map of six noise

separated from the runways which could explain its low count. However site #12 doesn’t have a good explanation for being

so low.

By looking at the runway data and focusing on the triangle of sites North of the airport (#11, #12, and #13) we can see the key

difference for site #12.

Unsurprising for December, Southflow was much more common than Northflow. In Northflow, these departures are high

throttle (i.e. loud) and the three sites give similar numbers, or at least the same order of magnitude. In Southflow however

something emerges. The big discrepancy with site #12 is due to 16R Southflow arrivals.

Site #11 is the most centered of the three and its numbers tell the story of runway use for Southflow arrivals. By a large

margin 16R, the “Third Runway”, is the most commonly used. As an aside, during the legal battles over building the third

runway, the community was assured it would only be used in rare circumstances, but that’s another story. So, site #12, being

East of the airport is the furthest from 16R, but we’re talking about a two orders of magnitude reduction in events from Site

#11 to Site #12 even though Site #12 is only ~3300 feet East of Site #11.

With this data it became clear why site #12 was reporting so many fewer events.

Note that only KAL019 was recorded by both SEA11 and SEA12 and were separated by about 21 seconds. These events are

attached to the sound level graph below, with the flights detected by SEA12 written in black above the peaks and the flights

only detected by SEA11 written in gray under the smaller peaks. So small in fact, that the algorithm did not consider them to

be events:

We filed Public Records Request 20-314 asking for a copy of the proposed contract in item 6e, and we request that this item

be removed from today’s Unanimous Consent Calendar until we’ve had a chance to review the changes to the contract.

Thank you,

David Goebel

President, Vashon Island Fair Skies