05-0531 Peer Review No. 1 041607
April 16, 2007
Mr. Jim Gibson, P.E.
Development Review Engineer
City of Yelm Community Development Department
P.O. Box 479
Yelm, WA 98597
Re: Peer Review – Site Construction Documents
Rainier View Estates
Dear Jim:
Per you request, Shea, Carr & Jewell, Inc. has performed a peer review of Rainier View Estates construction plans, stormwater drainage report, storm drainage maintenance manual, and
erosion control report. Our comments are as follows:
Storm Drainage Report:
Section 3 – Infiltration testing needs to be completed for the civil engineering review of the plans and report. Please provide soil testing information for the site at the proposed
location of the stormwater facility. Review of the storm calculations will be based on the presumed rate used during this analysis. Once testing is complete, the report may require
revision, including sizing computations.
Section 6 – Sub-Basin Description – What is meant by “conservative” in terms of the assumed roof area? Is this assumed to be a high or a low number? If it is high, this assumption
will result in undersizing the wetpond and infiltration pond. If it is low, it will result in the undersizing of the roof drain systems. It is understood that the building sizes are
unknown at this time. However, information on sizes of similar subdivisions in the area should be easily obtained. Please provide a more accurate assessment of expected roof size for
roof drainage system sizing. If this results in a change of area, please revise all other sizing computations accordingly.
Stormwater Maintenance Manual:
References to commercial and multi-family should be removed. This is a single family project.
Construction Plans:
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.
The plan set as currently shown is not stakable. Information needs to be provided to tie this site to an existing structure such as a benchmark.
Sheet 1 of 14:
Please provide the Hearing’s Examiner Conditions of Approval on the cover sheet.
Sheet 3 of 14:
Please revise the call out at the sediment trap that indicates a 2:1 max slope. As this is a fill area, 2:1 slopes would not be allowed. Further, the slope shown appears to be 4:1.
Indicate a typical cross section for the interceptor ditches proposed.
Sheet 4 of 14:
Please add notes for inlet protection.
Sheet 5 of 14:
Please add proposed spot elevations where indicated.
Proposed contours need to be shown in the steep slope area between lots 1-4 and the road. Many of these lots will have steep (20-26%) yard areas.
Will the proposed buildings encompass the entire building envelope shown? If so, the grading between the building and the retaining wall on lot 4 appears to exceed 2:1 and on lot 5
it appears to exceed 3:1. Fill slopes need to be 3:1 or flatter. Further, a few feet of gradual slope area is needed around the building in order to provide adequate stability for
foundations. Please clarify grading in this area. If the proposed building foot print is unknown, notations need to be added directing the contractor regarding grading limitations
on these lots.
The grading on lots 1-4 and the storm drain do not seem possible as currently shown. The wall proposed does not appear to address the tie in and continuity issues. This should become
clear once contour information is added.
Sheet 6 of 14:
According to MDNS condition #2, a cul-de-sac is required at the north end of the interior street. Please revise the design to include the required cul-de-sac.
The utility crossing information between crossing #1 and crossing #2 is inconsistent. On crossing #1, the crown of the 10 inch storm drain pipe is called out as 342.45 feet (making
the invert approx. 341.61). At crossing #2, the invert of the same pipe is called out as 343.83 feet. The slope of the storm pipe is 0.0441 ft/ft. The slope represented by the crossing
information would be about 22%. Please revise the information given for the 10 inch pipe in crossings #1 and #2.
Provide call outs indicating the dimensions of the road right-of-way, size of planter strip, sidewalk, road, etc. The road surface scales to only about 35 feet. Per COY Standard Detail
4-7, a local access road requires 37 feet of road paving. It appears that the planter strip is about 8 feet when it is only required to be 6 feet. Please revise the road section to
match the standard detail. Please revise storm drainage calculations as required to account for the increase in impervious area.
Please provide additional information on the horizontal curves within the roadway including radius, delta, length, etc.
Sheet 7 of 14:
Please revise the notation in the roof drain drywell detail. This appears to be sizing requirements from the Thurston County Drainage Design Manual. Sizing for drywells to be per the
1992 DOE Manual and should match what was calculated in the drainage report.
Sheet 8 of 14:
It does not seem that the overflow pipe from the wet pond to the infiltration pond will be stable with only some rip rap to keep it in place. The overflow can be a weir which may be
a better application.
Sheet 9 of 14:
Please add station call outs on the water fittings indicated.
Please change the water fitting at Station 6+82.46 to a blow off assembly.
Move the hydrant valve to be at the main prior to the bend.
The water valves shown before the 90 degree bend and after the hydrant are not required for any of the fittings shown. However, one valve is required for every 1,000 feet of water main.
Although the site has less than 1,000 feet of water main, one valve should be located on the main at this site. Therefore, one of the valves may be removed.
Please call out what type of water fitting joints (FLxMJ, MJxFL, etc.). This is not consistently referenced.
If the driveway for lots 8 and 10 will be installed and paved as part of the initial site development, the sewer laterals should be extended to beyond the pavement as part of the site
work. This should be done for the water too if it will be within the private driveway area. These should be shown on this plan.
The two gate valves shown at the 90 degree bend for the STEP sewer are not required.
The automatic air pressure valve shown at Station 0+09.00 is not required. Please remove.
It appears that lowering the STEP main to avoid conflicts with the storm system will require pipe deflection. The City of Yelm does not allow pipe deflections. Please revise to include
vertical bends.
All of the water and sewer fittings should be referenced on the profile view.
The irrigation meter will require adequate backflow prevention.
Should you have any questions or comments, please contact me at (360) 352-1465 at your earliest convenience.
Sincerely,
Shea, Carr & Jewell, Inc.
Amy M. Head, P.E.
Project Manager
N:\Projects\605 City of Yelm\605-05 Civil Plan Reviews\Phase 07 - Rainier View Estates\Correnspondence\041007 firstreviewcommentltr.doc