Frederick_PL-8159_Byron_ADD_BLD20090479_4.pdf
City of Edmonds
TH
121 5 AVENUE NORTH EDMONDS, WA 98020 • (425) 771-0220 FAX(425) 771-0221
Website: www.ci.edmonds.wa.us
DEVELOPMENT SERVICES DEPARTMENT
Planning • Building • Engineering
Engineering Plan Review Comments
Permit Application :Date:
# BLD20090479 12/30/09
Project Name/Address:
Larson – 8159 Frederick PL
Contact Person/Address, Fax or E-mail:
Yakov Shadyrya – yshadyrya@yahoo.com
Reviewer: JENNIFER COLLINS Division:
ENGINEERING
During review of the subject submittal, it was found that the following information, corrections, or
clarifications would need to be addressed. All Handouts referred to in these comments can be accessed at
our website: www.ci.edmonds.wa.us under City Government / Development Services Department /
Engineering Division then scroll down to Handouts:
ST
1 Review – 8/11/09
nd
2 Review – 9/16/09
rd
3 Review – 10/2/09
th
4 Review – 12/30/09
1.OK
1)OK
2)OK
3)OK
4)OK
5)OK
6)12/30/09 – Comment was partially addressed. Due to the amount of impervious surface area on
the site, code requires one of the following:
a.Collect storm water runoff from new impervious surfaces (added after 1977) and route it to
a detention system (see handout E72). From the detention system, release the water to a
spreader trench (see E5.1). There will need to be a minimum of 30’ between the spreader
trench and the property line, or
DATE E-MAILED 12/30/2009 PAGE()
1
City of Edmonds
TH
121 5 AVENUE NORTH EDMONDS, WA 98020 • (425) 771-0220 FAX(425) 771-0221
Website: www.ci.edmonds.wa.us
DEVELOPMENT SERVICES DEPARTMENT
Planning • Building • Engineering
Engineering Plan Review Comments
b.Remove existing impervious surface area such that you have less than 2,000 sq ft of new
impervious surface area (constructed after 1977).
10/2/09 Comment: Per Edmonds Community Development Code (ECDC) Chapter 18.30, there are
requirements for drainage control when over 2000 sqft of new impervious surface has been constructed
after July 7, 1977.
a.If there is over 2000sqft of new impervious surface, please provide a drainage plan.
Please resubmit 3 copies of the revised site drawings and associated documents with a written response to
each item to an Engineering Technician. Please contact me at 425-771-0220 ext 1321 or by e-mail at
collinsj@ci.edmonds.wa.us if you have specific questions regarding these plan corrections.
DATE E-MAILED 12/30/2009 PAGE()
2
#E72
STORM WATER MANAGEMENT (SWM), DRAINAGE PLANNING
AND
EROSION AND SEDIMENTATION CONTROL (ESC) PLANNING
On July 6, 1977, the City Council passed Ordinance #1924 requiring storm drainage detention on
all new developments and on, February 17, 1995, amended that ordinance with Ordinance 3013
requiring storm water quality control on any new or redevelopment with more than 2000 square
feet of new impervious surface area. Engineering Interpretive File #95-E01, dated January 30,
1995, clarified the intent of the two ordinances in that all impervious surface area from July 7,
1977, shall be cumulative in nature (see attached examples) and when the impervious surface
quantity exceeds that 2000 square feet threshold, an on site detention will be required.
The Edmonds Community Development Code (ECDC) Chapter 18.30 outlines the requirements
for drainage control on all construction with over 2,000 square feet of new impervious surface.
All activities that necessitate a clearing or grading permit, and all utility projects, consisting of
more than 500 linear feet of trench excavation, shall be required to control erosion and sediment
during construction. Upon completion of construction, all exposed soil shall be permanently
stabilized.
Under the new 2004 International Building Code, footing drains are now required. Footing
not
drains shall connect to the detention system but may connect to the outflow side of the
detention system or other approved drainage source.
Materials considered as impervious:
Gravel, concrete, asphalt, brick, stone pavers, etc.
Areas considered impervious:
Driveways, roofs, patios, porches, pool decks, solid surface decks, sidewalks, etc.
S:\\ENGR\\HANDOUTS, POLICIES & PERMITS\\Old Handouts\\Pre-2009 Handouts\\Storm Water Mgmt & ESC E72 Revised 08.06.DOC
1
#E72
PROCEDURES:
Prior to any permitted construction, the applicant/developer shall submit plans for review and
approval. If the new construction creates more than 2000 square feet of impervious surface area,
a storm drainage detention plan must be submitted with the permit application for review and
approval.. Once the building permit is issued, the drainage system shall be installed concurrently
with site development and shall be completed as shown on the approved plans. DETENTION
SYSTEM REQUIREMENTS
1. Construction with less than 2000 square feet of impervious surface area (new or cumulative)
does not require a detention system.
2. Construction with more than 2000 square feet of impervious surface (new and or cumulative
from July 7, 1977 to present) will require a storm detention system to handle the total amount of
the new cumulative surface area
Detention systems designed to accommodate between 2000 and 5000 square feet
o
of impervious area can be sized according to this handout.
Systems designed to accommodate over 5000 square feet of impervious surface
o
area must be designed and stamped by a licensed Engineer.
If the location of development is in a critical, an environmental, or in special
o
problem areas, the detention system must be designed and stamped by a licensed
Engineer, regardless of the size of the system.
Standard/Preferred Plan Approach
The remainder of this document describes the standard plans. Preprinted sheets are included in
this packet which can be used to determine the size of the detention system, for those impervious
surface area less than 5000 square feet, and should be submitted with the permit application. If
you have questions of a technical nature, please call the Hydraulics Engineer at (425) 771-0220
The standard plan approach uses an enclosed subsurface detention system discharging to an
acceptable outfall location. Any other type of plan must be prepared by a licensed engineer.
There is no assurance that the proposal you submit will be subsequently approved.
S:\\ENGR\\HANDOUTS, POLICIES & PERMITS\\Old Handouts\\Pre-2009 Handouts\\Storm Water Mgmt & ESC E72 Revised 08.06.DOC
2
#E72
BASIC ESC REQUIREMENTS
A temporary sediment and erosion control plan is required. Section 18.30.050 of the ECDC
delineates the requirements of the plan. The location of the sediment and erosion control
practices or devices and the limits of disturbed area must be shown on the plan view. Examples
of temporary sediment and erosion control practices and devices include:
Earth dike diversion to rout clean off site water around the disturbed area.
o
Straw bale barriers
o
Stabilized construction entrance
o
Temporary seedin practices
o
Practices used to minimize soil exposure.
o
Details of the erosion and sediment control devices are to be provided with the
drainage plan.
A sequence of construction must be provided. The sequence must
o
stipulate that the temporary sediment and erosion measures will be in
place and inspected prior to any construction or site clearing.
Furthermore, it must address the requirement for the sediment and erosion
control practices and/or devices to be maintained until the permanent
vegetation is established.
Basic Drainage Requirements
Submit three (3) drainage plans to scale, at a scale of 1”=10’ or 1”=20’. The drainage plan can
be placed on the grading or plot plan submitted with their building permit. The following
elements must be included with the drainage plan:
1.Show locations where concentrated surface water enters the property, the route it now
takes through the property and the locations where it leaves the property. A
description of the type and magnitude of flow should be noted on the plan – for
example, “intermittent flow during storms in shallow grass swale”. Show all other
surface waters.
2.Show locations and scaled dimensions of all existing and proposed buildings and
other impervious surfaces.
3.Show the route and the types of channel to be provided for any concentrated flow that
is to be changed. Note that structures are to be set back at least ten (10) feet from any
closed drainage facility and fifteen (15) feet from the top of the bank of any channel,
pond or stream. Additional setbacks or native growth protection easements may be
S:\\ENGR\\HANDOUTS, POLICIES & PERMITS\\Old Handouts\\Pre-2009 Handouts\\Storm Water Mgmt & ESC E72 Revised 08.06.DOC
3
#E72
required through the SEPA process. Structures must be at least one (1) foot above the
maximum water level in the channel. Work in streams, ponds or channels require
State Department of Fisheries or Department of Wildlife hydraulics permit.
4.Profile the elevations of the existing utilities and proposed drainage system (inverts,
pipe sizes and ground cover).
if surface water enters the property from off site
5.Topography shall be shown .
Plan must show all drainage areas that contribute surface water to the site. Contour
interval shall be two (2) feet; however, five (5) feet may be acceptable in some cases.
(Aerial photos with five (5) foot intervals are available from the City.)
6. Show all improvements or other methods of handling surface water runoff in
accordance with the requirements of Section 18.30.060 of the ECDC and this handout .
7. Calculations must be submitted when plans are prepared by a Civil Engineer.
8. The detention worksheet must be completed and submitted when standard plans are
used for systems under 5000 square feet of impervious surface area.
9. Show locations of roof tightline(s) and footing drains and their connection points to
the storm system.
Standard Plan Detention System
1.Select the outflow location. It must be low enough to allow the detention pipe to
drain completely.
a) If a public storm drain or public drainage ditch is within or adjacent to the
property, direct the outflow pipe to these facilities.
b) When there is no public system available, direct the outflow to a well defined
drainage channel that drains through the area to be developed. The outlet pipe
and the channel at the discharge location must be within the property.
2.Determine an on-site location for the underground detention pipe. The detention pipe
must be placed downhill of all impervious surfaces so the surface water runoff can be
detained.
3. Tightline(s) from roof drains and driveway drains shall connect to the detention
system and can connect to either end of the system. Footing drains shall not be
connected to the roof tightline drain pipe. Neither roof drains nor footing drains shall
be connected to the sanitary sewer. Footing drains shall not connect to the storm
detention system but shall connect to the outflow side of the control structure.
S:\\ENGR\\HANDOUTS, POLICIES & PERMITS\\Old Handouts\\Pre-2009 Handouts\\Storm Water Mgmt & ESC E72 Revised 08.06.DOC
4
#E72
(Discharging groundwater through footing drains to storm water systems can impact
fish resources by reducing the low flow volumes of water in streams.)
4.Complete detention work sheet (for 5000 sq. ft. or less and not in critical,
environmental or other sensitive areas).
a) Compute the impervious surface area that will drain to the detention system
and enter on the detention work sheet.
b) Indicate the detention pipe diameter and specify the required detention pipe
length for impervious surface area using Table 1. Enter the pipe diameter and
length on the work sheet.
c) Indicate the required outlet orifice size for the impervious surface area using
Table 2. Enter the outlet orifice size on the work sheet.
Indicate the pipe invert elevations of the detention pipe and the outflow
d)
pipe and rim elevations of the catch basins.
e.) Provide invert elevation at the connection point to the City storm System.
Maintenance of Detention Systems
Material must be removed from the catch basins and detention pipe to prevent clogging,
especially at the outlet control system. Catch basins should be cleaned at least twice per year.
Frequent catch basin cleaning will reduce the need for the more difficult task of cleaning the
detention pipe. The system should be kept clean during construction. Material must be
physically removed and not just flushed downstream.
______________________________________________________________________________
EXAMPLES :
Determination of impervious surface area based on the July 1977 ordinance:
Example 1:
Existing house built prior to July 7, 1977 – 1800 square feet existing impervious surface area;
1999- Constructed 400 square foot addition- since house was built prior to ordinance
date, the existing impervious surface area is grandfathered and since the proposed new
impervious surface is less than 2000 sq. feet a detention system is not required.
Example 2
S:\\ENGR\\HANDOUTS, POLICIES & PERMITS\\Old Handouts\\Pre-2009 Handouts\\Storm Water Mgmt & ESC E72 Revised 08.06.DOC
5
#E72
Existing house built prior to July 7, 1977 – 1800 square feet existing impervious surface area;
1999
- Constructed 400 square foot addition- since house was built prior to ordinance
date, the existing impervious surface area is grandfathered and because the proposed
new impervious surface area is less than 2000 sq. feet, a detention system is not required.
2001
- Constructed 800 square foot addition- With addition, total impervious surface area
is now (400+800)= 1200 sq feet, again no detention required.
2004
- Propose 1000 sq ft garage- With this addition, the cumulative total impervious
surface area now exceeds 2000 sq ft (400+800+1000)=2200 sq ft., therefore a detention
system will be required for all 2200 sq ft.
S:\\ENGR\\HANDOUTS, POLICIES & PERMITS\\Old Handouts\\Pre-2009 Handouts\\Storm Water Mgmt & ESC E72 Revised 08.06.DOC
6
#E72
Example 3
after
Existing house built July 7, 1977- has 1800 square feet of impervious surfaces area;
1999- Constructed 400 square foot addition -
- since the house was built after the ordinance date, but had less than 2000 sq ft
impervious surface area, no detention was required, however, with the proposed 400 sq ft
addition, the cumulative total impervious surface area now exceeds 2000 sq ft. A
detention system will be required for the total (1800+400) = 2200 sq ft.
Example 4
Existing house built after July 7, 1977- has 1800 square feet of impervious surfaces area;
1999-Constructed 400 square foot addition- detention system sized and installed for 2200 sq ft.
2004-Proposed 1500 square foot addition- because the existing detention system was sized for
only 2200 sq ft and, a separate detention system will have to be constructed for the new 1500 sq
ft or the existing system will have to be modified to handle 3700 sq ft.
S:\\ENGR\\HANDOUTS, POLICIES & PERMITS\\Old Handouts\\Pre-2009 Handouts\\Storm Water Mgmt & ESC E72 Revised 08.06.DOC
7