1405 Yelm Ave E - Drainage Rev Ltr Olympic Engineering 04292014PO Box 12690
Olympia,WA 98508
360705.2474
360.705.2443 fax
E#V G I W E E R I N G www.olyeng.com
April 29, 2014
Cheryl Sojak
PO Box 138
Yelrn, WA 98597
csojak@farmersagent.com
Re: 1405 Yelm Ave. E, Yelm, WA
Storm Drainage Maintenance for l.andscape Supply Business
OE No. 07014
Dear Ms. Sojak:
It is my understanding that a landscape supply business will be leasing a parcel located at 1405 Yelm
Ave. E and that the City of Yelm has raised some concerns about the potential for landscape supply
debris entering the on-site storm drainage system and possibly causing premature failure of the
system.
The existing drainage system consists of a grassy biofiltration strip that provides for treatment of
stormwater runofF from the paved area along with an infiltration trench that provides for temporary
storage and infiltration of the treated runoff. The purpose of the biofiltration strip is to help prevent
the solids and pollutants in stormwater runoff from entering into the infiltration system, eventually
causing premature failure and allowing pollutants to reach groundwater. These facilities are located
along the west side of the parcel.
Based on the site plan you provided, it appears the landscape supply bins (bark, topsoil, etc.) will be
placed along the east side of the paved area, furthest away from the drainage system. The proposed
use will create an increased potential for sediments to enter the drainage system and cause
premature failure. In order to prevent premature failure of the existing drainage system, I
recommend that the attached maintenance plan be implemented. In addition to the maintenance
checklists, it is imperative that the pavement surface be swept on a regular basis as needed to keep
the pavement surface clean of debris. This is extremely critical prior to any major storm event.
The proposed landscape supply use will not have an adverse impact on the existing storm drainage
system as long as the recommended maintenance is routinely followed.
If you have any questions, please call me at (360) 705-2474 or e-mail me at chris@olyeng.com.
Sincerely,
Olympic Engineering
1
Chris Merritt, PE
Principal Engineer
G:File Cabinet Business\Olympic ProjedsWrchive 2007W7014-Sojak Car Lot Sojak 042914 Maintenance Letter.docx
STORMWATER FACILITIES
MAINTENANCE PROGRAM
for
140 5 Ye I m Ave. E
Yelm, WA 98597
Prepared by:
OLYMPIC
ENGINEERFNG
PO Box 12690
Olympia WA 98508
360.705.2474
360.705.2443 fax
www.olyeng.com
Instructions for Use of Maintenance Checklists
The following pages contain maintenance tables for most of the applicable Best Management
Practices (BMPs). The owner should plan to complete a checklist for all system components on the
following schedule:
M) Monthly from October through April.
A)Annually, once in late summer(preferably September)
S) Storm-based, after any major storm(use 1 inch in 24 hours as a guideline).
The following tables may be used as checklists. Maintenance personnel may use photocopies of these
pages and check off items inspected and problems noted during each inspection. Actions taken and
corrective action recommended should also be noted.
You may call the Jurisdiction for technical assistance. Please do not hesitate to call,especially if you
are unsure whether a situation you have discovered may be a problem.
In addition to the following maintenance checklists the owner should sweep the naved areas on a
frequent basis as needed to keep the avement surface clean of debris.
Page 1 of 5
STORMWATER FACILITY MAINTENANCE PROGRAM
COVERSHEET
Inspection Period:
Number of Sheets Attached:
Date Inspected:
Inspector's Signature:
Page 2 of 5
Maintenance Checklist for Infiltration Trench
Drainage
Systems Conditions that Shall
Frequency Feature Problem Conditions to Check For Exist
M,S General Trash and Dumping of yazd wastes such as grass clippings Remove trash and
Debris buildup and branches into basin. Unsightly accumulation debris.
in basin ofnon-degradable materials such as glass,plastic,
metal,foam,and coated paper.
M Poisonous Any poisonous vegetation which may constitute a Remove poisonous
Vegetation hazazd to the public. Examples ofpoisonous vegetation. Do not
vegetation include:tansy ragwoR,poison oak, spray chemicals on
stinging nettles,devilsclub.vegetation without
obtaining guidance
from the Thurston
County.
A Tree Growth Tree growth in pond or swale bottoms,side Trees removed from
slopes and maintenance access azeas. facility bottom,side
slopes and maintenance
access areas.
Remove species that aze
not part of recorded
planting plan.
M,S Fire Hazazd or Presence of chemicals such as natural gas,oil, Find sources of
Pollution and gasoline,obnoxious color,odor,or sludge pollution and eliminate
noted. them. Water is free
from noticeable color,
odor,or contamination.
M Vegetation not Grass cover is spazse and weedy or is overgrown. Selectively thatch,
growing or is Plants are sparse or invasive species are present. aerate,and reseed
overgrown ponds. Grass cutting
unnecessary unless
dictated by aesthetics.
Contact the Thurston
County Noxious Weed
program for direction
on invasive species
such as purple
loosestrife and reed
canary grass. Pond
bottoms shall have
uniform dense coverage
of desired plant species.
M Rodent Holes If the facility is constructed with a dam or berm, Rodents destroyed and
look for rodent holes or any evidence ofwater dam or berm repaired.
piping through the dam or berm. Contact the Thurston
County Public Health
i and Social Services
IDepartment for
guidance.
M Insects When insects such as wasps and hornets interfere Insects destroyed or
with maintenance activities,or when mosquitoes removed from site.
become a nuisance. Contact Cooperative
E ension Service for
guidance.
Page 3 of 5
Drainage
Systems Conditions that Shall
Frequency Feature Problem Conditions to Check For Exist
A Storage Area Sediment A soil texture test indicates facility is not working Sediment is removed
buildup in at its designed capabilities or was incorrectly and/or facility is
system designed.cleaned so that
infiltration system
works according to
design. A sediment
trapping azea is
installed to reduce
sediment transport into
infiltration azea.
A Storage area A soil texture test indicates facility is not working Additional volume is
drains slowly at its designed capabilities or was incottectly added through
more than 48 designed.excavation to provide
hours)or needed storage. Soil is
overflows aerated and rototilled to
improve drainage.
Contact the County for
information on iu
requirements regarding
excavation.
M Sediment Any sediment and debris filling azea to 10 Clean out sump to
trapping azea percent ofdepth from sump bottom to bottom of design depth.
outlet pipe or obstructing flow into the connector
pipe.
One time Sediment Stormwater enters infiltration area directly Add a trapping azea by
trapping azea without treahnent.constructing asump for
not present settling of solids.
Segregate settling azea
from rest offacility.
Contact County for
more guidance.
M Rock filters Sediment and By visual inspection little or no water flows Replace gravel in rock
debris through filter during heavy rain storms. filter.
If you are unsure whether a problem exists,please conta.ct Thurston County and ask for technical
assistance.
Kev:
A=Annual (March or April preferred)
M=Monthly(see schedule)
S =After major storms
Page 4 of 5
Maintenance Checklist for Biofiltration Strip
Drainage
Systems Conditions that Shall
Frequency Feature Problem Conditions to Check For Exist
M General Sediment Sediment depth exceeds 2 inches. Remove sediment
Accumulation on deposits,re-level so slope
Grass is even and flows pass
evenly through strip.
A Trees Trees growing in swale bottom or side slopes. Trees removed from
swale bottom and slopes.
Trees removed that aze
not part of planting plan.
M General Vegetation When the grass becomes excessively tall Mow grass,control
greater than 10 inches);when nuisance weeds nuisance vegetation,such
and other vegetation starts to take over that flow not impeded.
Grass should be mowed
to a height beriveen 3-4
inches.
M General Trash and Debris Trash and debris accumulated on the filter strip. Remove trash and Debris
Accumulation from filter.
M General Erosion/Scouring Eroded or scoured areas due to flow For ruts or baze areas less
channelization,or higher flows. than 12 inches wide,
repair the damaged area
by filling with crushed
gravel. The grass will
creep in over the rock in
time. Ifbare azeas are
lazge,generally greater
than 12 inches wide,the
filter strip should be re-
graded and re-seeded.
For smaller bare azeas,
overseed when baze spots
aze evident.
M General Flow spreader Flow spreader uneven or clogged so that flows Level the spreader and
are not uniformly distributed through entire clean so that flows aze
filter width. spread evenly over entire
filter width
If you are unsure whether a problem exists, please contact Thurston County and ask for technical
assistance.
A=Annual (March or April preferred)
M=Monthly (see schedule)
S =After major storms
Page 5 of 5
I