3.15.18 Eng Response to footing drain evaluation.pdfRivera, Chris
From:
Rivera, Chris
Sent:
Thursday, March 15, 2018 5:29 PM
To:
'John Yuen'
Cc:
'Christopher Lyon'; 'Jacob Lyon'
Subject:
City of Edmonds - Engineering Comments to Evaluation letter addressing footing drains
- Brackett's Corner, BLD20160598
Hello,
Below are items of concern noted by our stormwater engineer regarding the evaluation letter dated 3/6/18, provided by
John Yuen with LSA.
Lots With Issues:
Lot 5 — Does not matter if that connection point is below footing drain since water if infiltration trench is above both
elevations; water will back up through both connection point & footing drain from trench. Design water storage is 0.7S'
above footing drain invert.
Lot 6 & 7 — Overflow install incorrectly; overflow elevation should be 445.40 but appears to be 444.45. Loss of volume
and function; requires revision. Corrected overflow puts storage 0.10' above footing drain invert.
Lot 8 — Does not matter if that connection point is below footing drain since water if infiltration trench is above both
elevations; water will back up through both connection point & footing drain from trench. Design water storage is 0.75'
above footing drain invert.
Lot 9 — Overflow installed incorrectly; overflow elevation should be 445.40 but appears to be 444.45. Loss of volume and
function; requires revision. Footing drain okay once corrected; footing drain 0.5' above storage elevation.
Lot 10 — Overflow installed incorrectly; overflow elevation should be 444.80 but appears to be 444.67. Loss of volume
and function; requires revision. Footing drain okay once corrected; footing drain 0.5' above storage elevation.
Lot 11 thru 14 —All require revisions because the overflow pipes were set (roughly V) too low; there is a loss of volume
and function. All of these lots appears will have footing drains below the corrected overflow elevations and will
backwater the footing drains.
The items that require revisions can be addressed by either:
Re -constructing items (overflow elevations) per plan,
Adjust overflow elevations to plan with tees/risers (requiring a new plan to be submitted 1"), or
submit updated calculations showing equivalent drainage functions achieve in as -built condition.
Other lots which have issue not noting specific revisions, simply need to be constructed per plan. While one-way valves
will protect the structures from backflow; they still leave nowhere for runoff in the footing drains to go when they are
backwatered to the valve.
If you have any questions, feel free to contact me.
Thank you,
Chris B. Rivera
Engineering Technician
City of Edmonds
1215 Ih Ave. N.
Edmonds, WA 98020
425.771.0220 ext. 1339
Chris.Rivera@edmondswa.gov