DDW-2024-012313

20 NORTH MAIN, SUITE 107 • ST. GEORGE, UTAH 84770
TEL: [phone] • FAX: [phone]

September 23, 2024

Paul Wright, P.E.
Regional Engineer
Utah Division of Drinking Water
620 South 400 East, Suite No. 400
St. George, Utah 84770

Subject: WCWCD Sand Hollow 2 MG Tank B Comment Responses

Dear Paul:

Thank you for your review of the Washington County Water Conservancy District’s
(WCWCD/District) Sand Hollow 2 MG Tank B Project drawings and specifications. We received your
comments via email on September 4, 2024. The purpose of this letter is to provide a written response
to your comments.

Utah Division of Drinking Water Comments and BC&A Response:

Comment 1: Sheet S-02 Detail A – The air vent detail should meet the following rule with regards to
curbing. Please verify that is the case.

Vent pipes, in addition to seepage rings, shall have raised concrete curbs that direct water away from
the vent pipe and are formed as a single pour with the roof deck.

Response: The new tank will be completely buried with fill material. The purpose of this detail is to
show that the vent will be raised above the fill with concrete walls supporting the vent at least 1’-10”
above the grade. A concrete pad is poured around the vent and support wall and sloped at 1% to direct
water away from the vent pipe. The roof deck is approximately 2’-2” below the concrete pad.

Comment 2: Sheet S-05, Detail C and Sheet S-06 Detail A – I can’t tell if the height requirement is met
for an earthen covered tank (18 inches above the cover). It appears that detail S-4446 on Sheet GS-
07, might be this but I wanted to verify that is the correct detail. Also, I want to verify that all pours
are continuous with roof and curbing according to the rule below.

(1) Height. There shall be at least one opening above the level of the overflow, which shall be framed at
least 4 inches above the surface of the roof at the opening; or if on a buried tank, shall be elevated at
least 18 inches above any earthen cover over the tank. The frame shall be securely fastened and sealed
to the tank roof to prevent any liquid contaminant entering the tank. Concrete drinking water storage
tanks shall have raised curbs around access openings, formed and poured continuously with the pouring
of the roof, and sloped to direct water away from the frame.

Response: Yes, both details meet the State height requirements. Sheet S-05, Detail C references standard
detail S/4446. The dimension from the concrete pad to the top of curb is 6-inch. Detail S-4446 Note 4
Paul Wright, P.E.
September 23, 2024
Page 2

2

says that “Access Hatch Integral Curb Height Shall be 12” Minimum”. This Detail S/4446 also notes that
the height from grade or top of roof shall be 1’-6” minimum to top of hatch, meeting the State
requirements.

For Sheet S-06, Detail A the top of the tank roof in this location is at elevation 3160.73. The design
specifies to put 2’-2” of fill on top of the tank so the concrete pad elevation is 3162.90. The top of the
Equipment Hatch is at elevation 3165.38, which is 2.48’ higher than the concrete pad., closely matching
the fill elevations. Also, consistent with Detail S-4446, the hatch will be a minimum of 12”. This brings
the hatch above the 18-inch minimum per State standards.

Comment 3: Is Hatch Detail S-4447, Sheet GS-07 also meant for a storage tank, if so, it needs to meet
the same requirements detailed in S-4446 with regards to being a close-fitting shoebox lid, with a
minimum 2-inch overlap, gasketed, and lockable.

Response: Detail S-4446, Sheet GS-07 refer to the two hatches on the top of the tank. Detail S-4447,
Sheet GS-07 refer to the hatches on top of the Valve Vault and does not need to meet the same Division
of Drinking Water standards that the two hatches on top of the tank need to meet.

Comment 4: Sheet S-11, 12 – What repair is being done? I assume it is for the existing 2 MG tank,
once the new tank is in operation. Sheet S-12 seems to show earthen fill on the tank that has not been
there in the hatch detail. Has the roof been analyzed to see if it can handle the structural load? Also, I
just want to verify that all materials that are used for repair on the inside of the tank are ANSI-NSF61
certified.

Response: Correct repairs shown on Sheets S-11 and S-12 show structural and crack repairs to the
existing 2 MG tank during a short shutdown period in the project. We are planning to bury the existing
tank to help protect it from thermal damages. To do this we had to raise the existing access hatch and
roof vent. We have analyzed the existing tank roof and connections to the wall and found them adequate
to support the additional load from the fill. We are fencing the existing tank to prevent anyone from
driving on it. We are also planning to complete some crack repair inside the tank during the tank
downtime. The specifications also require that all materials inside the tank meet ANSI-NSF61 standards.

Please feel free to call me at [phone] if you have any questions.

Sincerely,
Bowen Collins & Associates, Inc.
Todd Olsen, P.E.
Project Manager

cc. Tony Jones – WCWCD
Cody Nielson – BC&A

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