05-0601 Review letter No. 1 112706
City of Yelm
Community Development Department
105 Yelm Avenue West
P.O. Box 479
Yelm, WA 98597
November 27, 2006
Robert Connolly
Skillings Connolly Inc
5016 Lacey Blvd. SE
Lacey, WA 98503
RE: The Hutch Subdivision – SUB-05-0601-YL
Initial Review of Civil – Site Construction Documents
Mr. Connolly:
The City of Yelm has completed the initial review of the proposed subdivision. Your application included:
Civil Application
Construction Plans dated 10/13/06
Stormwater Report dated 10/13/06
Infiltration Report
We have reviewed the plans for compliance with the City of Yelm Development Guidelines, the DOE Stormwater Manual and general standards of civil engineering practice. In an effort to
expedite the review of this project we have sent this project out for Peer Review. The following comments need to be addressed before the plans may be approved for construction. The
comments are summarized below:
Peer Review Comments from Shea and Carr (Amy Head):
Storm Drainage Report:
Storm Drainage Report Section 9 – Facility Sizing and Downstream Analysis – According to this section, a detail of the AquaShield Aqua-Swirl Concentrator Model AS-5 has been provided
in Appendix B. This detail has not been provided. Please include.
Storm Drainage Report Section 9 – Facility Sizing and Downstream Analysis – The calculations of infiltration gallery volume do not take in to account the 12 inch pipes. Please revise.
Erosion Control Report Section 1 – Sequence and Procedure – Please provide more detail in this section.
Erosion Control Report Section 5 – Inspection Sequence – Please provide more detail in this section.
Erosion Control Report Section 6 – Control of Pollutants Other Than Sediment – Construction activities will likely introduce pollutants. Please address.
Storm Drainage Report Appendix B – Please provide calculations on how Darcy’s Law was applied to establish the pond stage discharge rating curve(Discharge D1 and D2). Typically, this
value would increase with pond height.
Storm Drainage Report Appendix B – Please provide pipe sizing calculations. I performed some quick spot checks of pipes with flat slopes and large contributing areas and they appear
to be undersized.
Storm Drainage Report – Please provide further information on maintenance responsibility as well as a maintenance schedule and required activities for all storm drainage systems.
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.
Blue line drawings are difficult to read and make assessment of plans difficult. For future submittals, please submit black line plans to aid in review.
All Roadway Plan and Profile Sheets:
The following comments apply to all the roadway plan and profile sheets:
Please provide flow arrows on storm pipe to indicate direction of flow.
Align stations with the profile grid so stations fall on major grid lines. This helps with plan clarity.
A minimum of 6 inches of clearance between storm and water crossings should be provided. When the minimum is provided, a sand cushion is required.
All Water and Sewer Plan and Profile Sheets:
The following comments apply to all the water and sewer plan and profile sheets:
Align stations with the profile grid so stations fall on major grid lines. This helps with plan clarity.
The sewer pipe material for 4 inch STEP sewer main shall be PVC 1PS 1120 SDR 21 Class 200. Please revise all pipe material call outs to reflect this pipe type.
The City of Yelm does not allow pipe deflections. It would appear that deflection may be needed in order to provide the alignments shown for both water and sewer. Please revise or
provide commentary if deflection will not be required.
Sheet 1 of 29:
Please provide the Hearing’s Examiner Conditions of Approval on the cover sheet.
Please complete the earthwork quantities section.
Sheet 3 of 29:
Silt fence shall be installed along the entire property boundary on the north, south, and west property lines as shown.
Key note #3 is never called out on the plan. A typical notation can be used for proposed catch basins. However, if there are existing catch basins that require protection, please note
all of these locations.
Given the project size and amount of on-site slopes, additional sedimentation measures should be taken such as sediment ponds, diversion swales, etc. Please provide design calculations
and show these elements on the construction plans.
Since Road D is not proposed as a construction entrance, please provide a physical barrier preventing its use once constructed.
There should be a sheet showing the lot numbers and dimensions. Please either add these to this sheet or provide an additional sheet showing this information.
Sheet 5 of 29:
There is an area along the north property line that should be filled. Please revise grading to fill this low area.
There are several areas on site where grading is steep. One block on Mountain View Road has slopes of as much as 14%. How will homes be constructed in this area? Please provide a
discussion on proposed construction of lots in these steep areas.
There is an area on road A (see plans) that has steep slopes that grade down from the road. Given the steepness of the slopes, runoff from the roadway is likely to flow in to the proposed
driveways. Please address how road drainage will be kept out of the driveways for these homes.
There is an additional area on Road A between Road A and Killion Road where the lots are below the adjacent roadway. Please address how road drainage will be kept out of the driveways
of these homes.
The grading plan is incomplete. Several contours in the area of Road E do not tie back to an existing grade. Please complete grading in this area.
At both intersections of Road B and Road A, there are contours that would indicate low spots. It does not appear that these low spots correspond with any drainage structures. Please
revise the grading to prevent future ponding in these low areas.
Sheet 6 of 29:
Not Used.
As the design of Mountain View Road frontage improvements are not complete, they were not reviewed. However, the cross section for Mountain View Road from stations 307+59 to 314+18
does not match the plan view shown on Sheet 29 of 29. Specifically, the sidewalk is shown to be directly adjacent to the right-of-way line. The cross section shows 2 feet in between
the sidewalk and the right-of-way line. According to City of Yelm Standard Detail 4-5, the additional 2 feet between the sidewalk and right-of-way is not required.
Sheet 7 of 29:
Many of the notes have missing information. Please complete.
The design for Road D is incomplete. Please complete design prior to resubmitting the plan set.
Construction note #2 and the location of the call outs in the plan view of Road D do not match. Please revise.
Please ensure no trees or light poles are proposed where storm drain crosses in the planter areas at the bulb outs.
Catch basin #1 is too shallow to be a type 2. The minimum depth of a type 2 catch basin with 12 inch pipe is about 4.8 feet. Please revise.
According to the Drainage Report, Mountain View Road drainage will be separate from the on-site drainage. It appears in the plan view of Road D, some Mountain View Road drainage will
connect to the on-site system. If off-site drainage connect to the on-site system, the system will have to be sized to accommodate this additional flow.
Sheet 8 of 29:
According to Detail 4-7 of the City of Yelm Development Guidelines, local access roads require bulb outs at intersections. Please revise the layout to include the required bulb outs
at all intersections. (See sheet 3 for marked up locations of bulbouts. JEG)
The bulb out on Road A, where indicated, is not required.
The maximum spacing between catch basins is 500 feet. A catch basin needs to be added along the north side of Road A.
The storm drain line between CB #17 and #7 crosses into the planter strip. Please ensure that no trees or light poles are proposed for this area.
Please ensure no trees or light poles are proposed where storm drain crosses in the planter areas at the bulb outs.
Sheet 9 of 29:
The rim elevation for catch basin # 35 (note #8) appears to be in error. Please revise.
Sheet 10 of 29:
A structure should be added between catch basin #19 and #21 to move the storm drain pipe out of the planter strip.
The symbol for catch basin #19 should be changed to a type 2 symbol. Please revise.
Catch basin #21 should be a type 2. Please revise.
The rim elevation for catch basin #16 does not match the rim elevation referenced on sheet 8. Please revise.
Add required bulb outs at intersection with Road A and Road C.
The invert elevation of catch basin #31 is 335.64 feet. It appears it is meant to flow to catch basin #23, which has an invert elevation of 336.26 feet. This invert
is too high for gravity flow. Please revise including the slope information on the pipe connecting these catch basins.
Sheet 11 of 29
Add required bulb outs at intersection with Road A and Road C.
The symbol for catch basins #24, #25, and #26 should be changed to a type 2 symbol. Please revise.
A structure should be added between catch basin #25 and #26 to move the storm drain pipe out of the planter strip.
Revise the indicated notation to reference local residential street standards rather than neighborhood collector.
Sheet 12 of 29:
The intersection grading for the intersection of Road D and Mountain View Road is incomplete. Please complete prior to resubmittal.
Sheet 14 of 29:
The following comments pertain to the west drainage basin:
Note #9 calls out a tee. I believe this should be a cross.
Note #10 should call out 62 feet of pipe, not 68 feet.
For the Aqua-Swirl, the inlet pipe should be offset from the outlet pipe per the detail in the storm drainage report.
The pipe referenced in note #13 should not be perforated. Please revise.
Notes #21 and #22 call out PVC pipe. Throughout, ADS N-12 pipe is used. Is this supposed to be ADS?
The pipes referenced in notes #15, #17, #19, # 21, and #22 are lacking slope information. Further, the perforated PVC pipe within the infiltration gallery should be called out to have
zero slope.
The following comments pertain to the east drainage basin:
All of the pipe call outs are lacking slope information.
For the Aqua-Swirl, the inlet pipe should be offset from the outlet pipe per the detail in the storm drainage report.
Sheet 17 of 29:
The cleanout detail shows an ADS pipe. I believe this should be PVC.
Sheet 18 of 29:
How will the sewer service for lots 46 and 47 connect? As shown, the water and sewer main lines are at basically the same elevation. How will the sewer service cross the water? If
the sewer service crosses over the water main, it will require encasement.
How will the water services for lots 41 through 44 connect? Again, the water and sewer main lines are at the same elevation through this area which will make crossings for services
difficult.
The profile information for Road D is incomplete and cannot be reviewed at this time. Please complete prior to resubmittal.
The tee referenced in note #3 (water) should have a valve on the main in Road D. Please revise.
The tee referenced in note #3 (sewer) should have a valve on the main in Road D. Please revise.
Sheet 19 of 29:
From station 22+22 to about station 26+50, the sewer main and water main are at similar elevations. Connection of services that must cross one of these mains may require encasing or
could present crossing difficulties.
Sheet 20 of 29:
The tee referenced in note #4 (sewer) should have a valve on the main in Road E. Please revise.
l
For the notes regarding connecting to the existing mains, the note content (other than notes about pavement restoration) should be the same as on Mountain View Road.
The profile for Road E should show existing utility crossings.
The connection to existing utilities at Road E is confusing. Is the connection out in Killion Road or were mains stubbed to the site? The line type would suggest stubs were brought
to the site but the notations for connection reference out in the street. Please revise or clarify.
There does not appear to be 18 inches of vertical separation between water and sewer where the water main for Road E crosses the sewer main for Road A. Encasement may be required.
See note from Sheet 22.
Sheet 21 of 29:
The tee referenced in note #7 (sewer) should have a valve on the main in Road C. Please revise.
Sheet 22 of 29:
The notes regarding sewer encasement should be revised to read, “Center the maximum standard length of sanitary sewer main below water main so joints will be equidistant from water main
crossing. Encase sanitary sewer main in a minimum one quarter inch thick continuous steel, ductile iron, or pressure rate PVC pipe with a dimension ratio (DR) of 18 or less with all
voids pressure grouted with sand-cement grout or bentonite.”
Sheets 28 and 29 of 29:
The road improvements for Mountain View Road were not provided. Please complete prior to resubmittal.
Public Works Review – Water and Sewer Departments:
Sewer (Randy Hatch):
1. Need ARV at high point, Sta. 24+00 Road A
2. Why does sewer mainline need C900 pipe if there is 12’ separation, or am reading this wrong?
3. Some water/sewer crossings do not appear to have 18” of vertical separation. Does this reflect reality?
Water (Edward Smith):
1. Sheet 18 Notes 1. The blow off assembly needs an eight inch gate valve at the end of the main for the future extension.
2. The water meter for lot 45 may need to be moved more North, so it will not be in a driveway.
3. All the water main needs to be eight inch pipe.
4. Sheet 18 Notes 5. The fire hydrant should be moved North too the water meters box’s side, and not in the center of the lot 50.
5. Can the water meter for lot 106 be moved to / with lot 107 to make it a double and too get it away from the sewer box?
6. Can the water meter for lot 105 be moved to / with lot 104 to make it a double and too get it away from the sewer box?
7. The water meter for lot 1 may need to be moved more North, so it will not be in a driveway.
8. Sheet 20 Notes 8. The blow off assembly needs an eight inch gate valve at the end of the main for the future extension.
9. Sheet 20 Notes 9 and 10. The water main is not stubbed out in this area. This needs to be hot tapped.
10. Why is the sewer and water at the same elevation on this project in a lot of the same area?
11. The storm drain ponds water meters have to have a Double Check Valve Assembly on these water meters.
12. The existing fire hydrant at Sprage Street looks like it will have to be moved.
13. The air/release need to exit thru the side or the back of the box. (Not the lid)
14. Sheet 27 of 29. Street Lighting (per Tim) see print.
15. Any Pocket Parks, street frontage on Killion Road and Mountain View Road with irrigation meters and Double Check Valve Assembly’s?
16. Change Signature block to Development Review Engineer.
It is the applicant/engineer responsibility to verify that all Conditions of Approval are met and addressed on the construction plans.
Please review and revise the plans to address the above referenced comments. When the project is resubmitted you will need to submit 4 sets of plans, 2 stormwater reports. The project
engineer is required to include a written response with the resubmittal, indicating how all the review comments above have been addressed or responded to. This will significantly expedite
our review of the project. If you have any additional questions or comments please do not hesitate to call or contact me at jimg@ci.yelm.wa.us.
Community Development Department
Respectfully,
Jim Gibson P.E.
Development Review Engineer