20100129 Peer Cmts 03182011March 18, 2011
Mrs. Karen T. BennettAdministrative SupportCity of Yelm Community Development Department105 Yelm Avenue WestYelm, WA 98597
Re: Peer Review - Site Construction Documents America's Credit Union
SCJ Project #0605-05/24
Dear Karen:
As you requested, Shea Carr Jewell has performed a peer review of the America’s Credit Union engineering construction plans and stormwater drainage report.
The review documents included:
Civil engineering plans signed December 29, 2010
Stormwater Technical Information Report dated December 2010
Our comments are as follows:
Storm Drainage Report:
The modeling of the infiltration trench is incorrect. No porosity factor was used in the set up the infiltration trench parameters. Typically a porosity of about 0.33 would be used
for this type of system. Please revise the modeling parameters and remodel the system. This could require revisions to system sizing.
As a note, the current modeling of the proposed infiltration trenches places an overflow riser at 1.1 feet. As only 1 foot of freeboard is necessary, the riser could be set at 3 feet
for the proposed 4 feet high trenches. This will likely help with facility sizing as modifications are made to address other model comments. .
According to Section 3.3.7 of Volume III, the site does not meet all of the site suitability criteria:
Site suitability Criteria 1 (SSC-1 Setback Criteria) – the infiltration facilities shall be set back at least 20 feet downslope of a building foundation and 100 feet upslope. The infiltration
facility in the building vicinity does not meet this requirement.
Site Suitability Criteria 5 (SSC-5 Soil Depth to Bedrock, Water Table, or Impermeable Layer) – the infiltration systems shall have at least 5 feet between the bottom of the facility
and
groundwater, bedrock or other impermeable layer. It is not known if these facilities meet the criteria as the test pits were not dug to a sufficient depth. The bottom of the infiltration
trenches 1a and 1b, for instance, are at an elevation of about 332.87. The existing ground is at an elevation of about 340 feet putting the bottom of the facilities just over 7 feet
below existing ground. Therefore, in order to assess whether this criteria has been met, the test pits should have been dug to be just over 12 feet deep. According to the geotech report,
the explorations were only 9 feet in depth. SSC-5 can be verified at the start of construction.
Construction Plans:
General:
Per Condition of Approval Number 4, a left turn restriction is required through installation of restrictive curbing or other means. Currently this has not been provided.
Per Condition of Approval Number 5, details of the bus stop need to be included in the plan set. These were not included.
Per Condition of Approval Number 8, evidence of proper abandonment of the existing well and septic system shall be provided prior to civil plan approval. Please provide this information.
Per Condition of Approval Number 13, LeMay must approve the location and access of the dumpster. Please provide this approval.
Per Condition of Approval Number 15, landscape and irrigation plans shall be provided. Please provide.
All Sheets:
The following comments apply to all sheets:
Some minor redline comments have not been called out in the letter but need to be addressed in the revised plans.
Sheet 1 of 12:
Please include the conditions of approval on the cover sheet.
Sheet 2 of 12:
Extend silt fence as marked on the plan.
Sheet 3 of 12:
According to Condition of Approval Number 9, all stormwater facilities must be set back 10 feet from the property line. The biofiltration swale does not meet this condition. Please
revise.
The landscaping along the west property line should be 8 feet in width. Please revise.
Please provide elevation information at both ends of the grade breaks.
The cross slopes of the sidewalk between the handicap ramp at the accessible parking and the front door appear to exceed 2% based on the limited information provided in this area. Please
revise if cross slopes exceed 2%.
Insufficient information has been provided to verify the cross slopes between the public sidewalk and the point of entry. Please ensure that a 2% cross slope is not exceeded.
Sheet 4 of 12:
Calculations have not been provided for the STEP tank sizing. Please provide.
Please provide stationing information for all proposed structures.
The Yelm East Avenue blow up only addresses revisions to the existing grass swale. What will happen with the infiltration trench? According Sheets ADR2, MDD1 and MDD2 of the WSDOT
construction plans for the SR507 project (included for your convenience), there is a storage drain that runs in the swale bank along the entire property frontage. This storage drain
is approximately 6 inches below the existing ground surface. The proposed driveway connections will essentially remove these trenches for the entire width of the driveways. Per Condition
of Approval Number 10, the removal of these storage drains need to be addressed.
How is backflow prevention being provided on the domestic water service? A RPBA is required behind the meter.
Please provide a call out for connection of proposed domestic water service line to existing.
What is proposed for the domestic water line that is no longer part of the proposed service? No direction has been provided on how this will be addressed.
The domestic water meter on the east side adjacent to the frontage appears to be in the way of the proposed fire line. Will this be removed?
The fire line does not require metering.
The Carson Box on the STEP service line shall be moved closer to the property line.
Please show the required City easement over all STEP tanks and piping.
Please identify the rim and invert elevations for the STEP tank. The City of Yelm’s depth requirements is 5 feet from finish grade to the tank invert. This needs to be verified and
shown on the plans.
Please indicate the size of the existing STEP and water service connections to the site. Please also indicate the size of the existing water meter.
The limits of the proposed sidewalk construction along the property frontage are unclear. Please indicate where sidewalk construction begins and ends.
Only one water meter is shown on the plans. How will irrigation be provided?
Sheet 5 of 12:
Please remove the City of Yelm curb ramp details and replace with WSDOT or AADAG details for curb ramps.
Sheet 9 of 12:
Please remove the COY Detail 6-10. Connection to the main does not apply as connection to the existing service stub is proposed.
Sheet 10 of 12:
Please remove COY Detail 7-1. Connection to the main does not apply as connection to the existing service stub is proposed.
As this is a commercial site, specific details of the selected STEP tank need to be provided. H20 loading will be required. The detail shall demonstrate the available detention, storage,
and working volumes.
Sheet 11 of 12:
Please remove COY Detail 7-2. It is not applicable to this project.
Please add City of Yelm sewer addendum notes to the plans.
Please add City of Yelm sewer inspection notes to the plans.
Should you have any questions or comments, please contact me at (360) 352-1465 at your earliest convenience.
Sincerely,
Shea Carr Jewell
Amy M. Head, PE, LEED AP
Associate Principal
N:\Projects\0605 City of Yelm\605-05 Civil Plan Reviews\Phase 24 - America's Credit Union\Correspondence\L-2011-0308 Bennett commentltr.doc