20140205155859428.pdfAugust 2, 2012
TGG Project #155-4
City of Edmonds
Development Services
121 5th Avenue North
Edmonds, WA 98020
Subject: Final Drainage Letter
870 Northstream Lane
Edmonds, Washington
BLD 20110059
Attention: Jennifer Lambert
The Galli Group monitored the installation of the drainage system for the above referenced project and
permit number. The improvements consisted of a catch basin directing stormwater runoff from the bridge
and aprons to a dispersion trench. The installation of the collection and dispersion system was in general
conformance with our recommendations and the approved plans.
One minor variation from our original submittal had to do with the surface mounted drains from the
abutment subdrains shown on the plans. The Corps of Engineers would not allow direct discharge to the
stream, so the backwall drains from the modular abutments were eliminated with our approval. Because
the aprons are covered, the site soils are relatively granular, the abutments allow water to pass through the
modular units, and there was no evidence of seepage all led us to conclude that the drains would not be
necessary. In addition a high quality free -draining backfill was used behind the abutment walls.
The site appeared well on its way to final stabilization from established vegetation as of our last site visit.
Sincerely,
THE GALLI GROUP
110
Paul L. Stoltenberg, P.E.
Project Geotechnical Engineer
?012
5034 — 18t" Avenue NE, Seattle, WA 98105 Phone: 206.525.5097 Fax: 206.525.5091