20100177 Peer Cmt #1 02082011February 7, 2011
Mrs. Karen T. Bennett
Administrative Support
City of Yelm Community Development Department
105 Yelm Avenue West
Yelm, WA 98597
Re: Peer Review -Site Construction Documents
Salmon Run Apartments
SCJ Project #0605-05/25
Dear Karen:
As you requested, Shea Carr Jewell has performed a peer review of the Salmon Run Apartments
engineering construction plans, STEP tank calculations, and stormwater drainage report.
The review documents included:
• Civil engineering plans signed January 6, 2011
• STEP System Report dated January 4, 2011
• Drainage and Erosion Control Plan Report dated January 10, 2011
Our comments are as follows:
Storm Drainage Report:
1. Because the 2005 DOE stormwater Manual is being followed, the stormwater report should follow
the requirements and format of Chapter 3 of Volume I of the manual. Please also update the report
to follow the layout and informational requirements Section 3.1.7. This includes preparation of a
stormwater pollution plan (SWPPP).
2. According to Section 2.1 of Volume III, all treatment BMPs, except wetpool-type facilities, should be
ci~arl ucina an annrnvarl rnntinunuc runoff mnrlal Rarauca ~niatnnnl-t~ma treatment is not
Mrs. Karen Bennett
February 7, 2011
Page 2 of 9
should be demonstrated that the 91St percentile runoff volume can infiltrate within 48 hours and
that the maximum ponded water depth can infiltrate within 24 hours.
4. 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. Most of the
proposed infiltration systems do not meet this requirement.
• Site Suitability Criteria 4 (SSC-4 Soil Infiltration Rate/Drawdown Time) -the short-term soil
infiltration rate should be 2.4 inches per hour or less. Only along-term infiltration rate has
been identified in the geotechnical report. Please update the report to identify whether
expected short-term rates meet the criteria for infiltration treatment.
• Site Suitability Criteria 6 (SSC-6 Soil Physical and Chemical Suitability for Treatment) -the
soil texture and physical and chemical characteristics should be evaluated to determine
suitability for use as treatment. No information regarding the soil properties and suitability
for treatment have been provided.
Please make the required modifications to meet the site suitability criteria. Further, please identify
in the report how all criteria are met.
5. The geotechnical report does not identify where infiltration tests were performed on the site unless
it was performed at each test pit. Please identify where infiltration testing was performed. In
addition, the geotechnical report states that further testing might be necessary once facility
locations are identified. Please confirm whether the geotechnical engineer requires additional
testing based on facility locations.
6. There is an area on the drainage basin map that is included in Basin C, which appears to be part of
Basin B per the provided grading plan. Please either revise the map and associated calculations or
clarify the grading if the current basin plan is the intent.
7. The calculations included in Appendix D appear to include sizing computations for both the water
quality systems and the flow control systems. Further, the flow control and treatment facilities
appear to be sized by the "Bowstring Method," which is not an approved method of calculation.
This section also refers to use of the WSDOT Hydraulics Manual. Please delete all computations that
are no longer applicable.
8. The WWHM output in Appendix E is confusing and hard to follow. Typically, each basin would be
Mrs. Karen Bennett
February 7, 2011
Page 3 of 9
10. It appears that the riser height for each infiltration trench was set at the very top of the facility. This
does not provide for freeboard. The DOE manual calls for 1 foot of freeboard, but 0.5 feet would be
acceptable. Revise all riser heights to allow for minimum freeboard.
11. According to Section 7.2 of Volume V, infiltration treatment systems a typically installed with
pretreatment systems to avoid clogging. It does not appear pretreatment has been proposed. How
will clogging be avoided?
STEP System Report:
12. Per Page C1-32 of the DOE Criteria for Sewage Works Design, working volume is also required in the
STEP tank. Currently only detention and storage volumes have been addressed. Please include
calculations of the working volume.
13. The entire required volume must be located below the float switch of the STEP tanks. Please
demonstrate how this is met for each building. The amount of volume available below the float
switch is manufacturer dependent; therefore, information specific to the selected STEP tanks should
be provided.
Construction Plans:
All Sheets:
The following comments apply to all sheets:
14. Some minor redline comments have not been called out in the letter but need to be addressed in
the revised plans.
15. Revise the approval block to be approved by the development services engineer and not the
director of public works. Approval block to be provided on all sheets.
Sheet 1 of 25:
16. Please include the conditions of approval on the cover sheet.
Sheet 2 of 25:
17. The erosion control notes indicate that ponds shall be operational prior to construction of
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February 7, 2011
Page 4 of 9
20. There is a missing detectable warning atone of the ramps.
21. Insufficient clear width has been provided on the flush sidewalks. The sidewalk width is 4 feet, and
the detectable warning area is 2 feet wide with a 6- to 8-inch setback. This provides less than 2 feet
of clear width. A minimum of 3 feet of clear width is required.
22. The dumpster enclosures appear not to have gates. Please revise to provide enclosure gates.
Sheet 4 of 25:
23. A detail of the curb ramps at the driveway entrances from the roadway needs to be provided.
24. Please revise detail number 7 to show the proposed detectable warnings at the top of the ramps
and reference detail 13.
Sheet 5 of 25:
25. If drainage will be allowed to enter the infiltration swales during construction, you need to take
measures to prevent plugging of those systems per the geotech report.
Sheet 6 of 25:
26. Please show the grading contours within the proposed swales. Currently, it is unclear how these are
graded.
27. Please provide cross sections of all proposed swales. The cross section should demonstrate the
Swale cross sectional geometry as well as information on the soil. According to the requirements of
BMP T7.30, the treatment soil must be at least 18 inches thick and meet specific parameters.
Currently, it is unclear if the proposed swales meet the BMP requirements.
28. Provide erosion control pads or similar devices at all of the curb inlets.
29. Please identify the limits of retaining wall construction through callouts or line type. It would
appear that the thick line type is the wall, but this is inconsistent between sheets.
30. Please identify bottom of wall elevations in addition to the top of wall elevations.
Mrs. Karen Bennett
February 7, 2011
Page 5 of 9
33. Please provide a cleanout where roof drain piping connects to the infiltration gallery pipe if not
connecting at a catch basin.
34. Please provide top and invert elevations for each of the galleries.
35. Although sufficient grading information has not been provided to accurately estimate gallery
depths, it appears, based on the information that was provided, that the gallery bottoms could be as
much as 9 or 10 feet below existing grade. Soil test pits were only dug to a maximum depth of 10
feet. Therefore, for some of the proposed facilities, the explorations performed were insufficient to
determine whether there is adequate separation from groundwater or what the infiltration rate is
for soils below the galleries. Please provide additional soil investigations with exploration depths
exceeding 5 feet below gallery bottom elevations to determine if all of the site suitability criteria are
met.
36. For the gallery on the west side of the site, how will the transition be made from perforated to non-
perforated pipe?
37. It appears that the retaining wall location on the westernmost Swale is not consistent between this
sheet and the grading sheet. If a wall is not proposed along the south side of the Swale, it is not
likely that the Swale will have a flat bottom in the areas where the Swale width is reduced (a flat
bottom is a requirement of this BMP). Please clarify.
38. Based on the cross section of the infiltration gallery provided on the detail sheet, there should be 3
feet from the bottom of the Swale elevation to the pipe invert in the gallery. The gallery on the
north side of the site has only 2.5 feet based on the information provided.
39. What is happening with the roof drainage from Building F?
40. The landscape plans show proposed trees on top of storm lines. Please coordinate with the
landscape designer to move the trees or the storm lines.
Sheet 8 of 25:
41. The filter fabric should not wrap along the bottom of the gallery. The infiltrative characteristics of
the fabric are often less than the surrounding soil and typically can cause plugging of the system.
Sheet 10 of 25:
Mrs. Karen Bennett
February 7, 2011
Page 6 of 9
46. Please provide pipe slope information for those portions of the sewer system that are gravity
systems (from building to STEP tanks). As many of these pipes cross the roof drainage system, this
information is required to assess potential conflicts.
47. Please show the required City easement over all STEP tanks and piping.
48. Based on estimations, it appears that several of the crossings of sewer and storm piping have less
than 6 inches of separation. Provide sand cushions where there is less than 6 inches of separation.
49. There appears to be a conflict between the storm pipe and sewer pipe upstream of STEP tank #2.
Please verify and correct if necessary.
50. Typically the Carson Boxes are located closer to the force main. The Carson Boxes should be moved
for STEP tanks 1, 3, and 5. These boxes are proposed in traffic areas; therefore, they will need to be
rated for H2O loading.
51. Please delineate the required sawcuts and pavement removal and subsequent patching of the
existing roadway for force main line installation.
52. It appears that there may be a mix up in labeling. A control panel is required for STEP tank #6, the
pumping tank, and not tank #8 as currently indicated. A control panel is not required for STEP tank
#7 as it is not a pumping tank. Further, the control panel for STEP tank #6 should be located close to
the tank.
53. Please call out the fittings at the force main including bends and tees. Callout should include
required valves.
54. Please change the pipe material specifications in notes 5 and 6. According to Section 7E.020 of the
City Development Guidelines, all pipe 2 inches and above shall be PVC 1PS 1120 SDR 21 Class 200
pipe and shall rubber ring gasket joints and shall comply with ASTM D 1784.
55. A hose bib is required within 50 feet of all STEP tanks for maintenance. Please note the hose bib
locations on this sheet.
56. Please identify the top and bottom elevations for all tanks (currently only pipe invert information is
provided). 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.
Mrs. Karen Bennett
February 7, 2011
Page 7 of 9
Sheets 11 and 12 of 25
60. The force main needs to have a depth of 5 feet. Please revise this sheet to show the appropriate
depth. Eighteen inches is only appropriate for service lines.
61. Please identify locations of any utility crossings. In addition, all required separations from water and
sewer shall be maintained at all crossings.
62. Please label all existing and proposed water lines and indicate the horizontal separation from these
water lines. Currently, the line types are all similar and it is difficult to determine the exact location
and extent of the water lines.
63. Because the stationing is on the sewer line, the stationing needs to be tied to something such as the
centerline of Vancil Road.
64. Identify the vertical scale used for the proposed profile.
Sheets 13 and 14 of 25
65. Details of the STEP tanks should be provided. These should demonstrate the available detention,
storage, and working volumes.
66. It appears that the pump control panels are proposed to be located at the buildings. Therefore,
detail 7-4 is not required. Please remove.
67. Pump control panels must be located on anon-living-space wall to avoid noise issues.
68. Please include COY Standard Details 7-5 and 7-9.
Sheet 15 of 25:
69. Please show the required utility easement on the water main line.
70. Please delineate the required sawcuts and pavement removal and subsequent patching of the
existing roadway for water main line installation.
71. Please indicate the connection type for all fittings (including bends) on the 8-inch water main line -
FL, FLXMJ, etc.
Mrs. Karen Bennett
February 7, 2011
Page 8 of 9
75. Please indicate the location of the double detector check valve for the fire lines. If located inside of
the building, please note.
76. Each of the domestic service lines required backflow prevention. Please show on the plans and
provide appropriate details. The backflow for this site will most likely be a reduced pressure
backflow assembly (RPBA), which is above ground within a fiberglass enclosure. This should be
taken into account when determining the appropriate location.
77. The domestic water service line for Building E is within the dumpster enclosure. This needs to be
moved.
78. There appears to be less than a 10-foot separation from the proposed water main and one of the
STEP tanks just east of Building F.
79. It is recommended to install one additional valve on the water main. With an additional valve, a
portion of the line could be shut off while maintaining flow to the other part of the line. Currently
the entire complex would be without water during maintenance and/or repairs.
80. The current proposed fire hydrant configuration does not provide adequate coverage. Please
provide additional hydrants or approval from the building official for the current layout.
81. The landscape plans show proposed trees on top of water lines. Please coordinate with the
landscape designer to move the trees or the water lines.
Sheet 16 of 25:
82. Please identify locations of any utility crossings. In addition, all required separations from water and
sewer shall be maintained at all crossings.
83. Because the stationing is on the water line, the stationing needs to be tied to something such as the
centerline of the adjacent road.
84. Identify the vertical scale used for the proposed profile.
Sheet 17 of 25:
85. Please provide the City of Yelm Standard Details 6-4.4 and 6-17.
Mrs. Karen Bennett
February 7, 2011
Page 9 of 9
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