Containment Dikes

Containment Dike Inspection References
ENSAT SP-001 Inspector: William Graves

1) EPA SPCC Guidance for Regional Inspectors - Chapter 7: Inspection, Evaluation, and Testing Page 7-41 Table 7-5.  "Checklist Summary of Industry Standards for Inspection, Evaluation, and Testing" lists the STI SP-001 as the sole applicable industry standard for inspecting containment dikes. 

(e)(1) Facility Drainage (onshore); (excluding production facilities)
(i) Drainage from diked storage areas have valves or other positive means to
prevent an oil spill.
(ii) Valves should be manual, open-and-closed design.
Retained stormwater from diked areas should be inspected before drainage [(e)(2)(iii)(B,C & D)].

(e) (2) Bulk Storage Tanks (onshore); (excluding production facilities)
(ii) Secondary containment is provided for the largest single tank plus an allowance for precipitation.
Dike walls and floor are "sufficiently impervious."
(iii) Drainage of rainwater from diked areas, by-passing treatment, is
accomplished according to the following:
(A) Normally the by-pass valve is sealed closed;
(B) The rainwater is inspected;
(C) The by-pass valve is opened/closed under supervision; and
(D) Records are kept of bypassing and drainage events

"Drainage, dikes, and walls for aboveground tanks" -
1910.106(b)(2)(vii)(a)
"Drainage and diked areas." The area surrounding a tank or a group of tanks shall be provided with drainage as in subdivision (b) of this subdivision, or shall be diked as provided in subdivision (c) of this subdivision, to prevent accidental discharge of liquid from endangering adjoining property or reaching waterways.
1910.106(b)(2)(vii)(b)
"Drainage." Where protection of adjoining property or waterways is by means of a natural or manmade drainage system, such systems shall comply with the following:
1910.106(b)(2)(vii)(b)(1)
[Reserved]
1910.106(b)(2)(vii)(b)(2)
The drainage system shall terminate in vacant land or other area or in an impounding basin having a capacity not smaller than that of the largest tank served. This termination area and the route of the drainage system shall be so located that, if the flammable liquids in the drainage system are ignited, the fire will not seriously expose tanks or adjoining property.
1910.106(b)(2)(vii)(c)
"Diked areas." Where protection of adjoining property or waterways is accomplished by retaining the liquid around the tank by means of a dike, the volume of the diked area shall comply with the following requirements:
1910.106(b)(2)(vii)(c)(1)
Except as provided in subdivision (2) of this subdivision, the volumetric capacity of the diked area shall not be less than the greatest amount of liquid that can be released from the largest tank within the diked area, assuming a full tank. The capacity of the diked area enclosing more than one tank shall be calculated by deducting the volume of the tanks other than the largest tank below the height of the dike.
1910.106(b)(2)(vii)(c)(2)
For a tank or group of tanks with fixed roofs containing crude petroleum with boilover characteristics, the volumetric capacity of the diked area shall be not less than the capacity of the largest tank served by the enclosure, assuming a full tank. The capacity of the diked enclosure shall be calculated by deducting the volume below the height of the dike of all tanks within the enclosure.
1910.106(b)(2)(vii)(c)(3)
Walls of the diked area shall be of earth, steel, concrete or solid masonry designed to be liquid tight and to withstand a full hydrostatic head. Earthen walls 3 feet or more in height shall have a flat section at the top not less than 2 feet wide. The slope of an earthen wall shall be consistent with the angle of repose of the material of which the wall is constructed.
1910.106(b)(2)(vii)(c)(4)
The walls of the diked area shall be restricted to an average height of 6 feet above interior grade.
1910.106(b)(2)(vii)(c)(5)
[Reserved]
1910.106(b)(2)(vii)(c)(6)
No loose combustible material, empty or full drum or barrel, shall be permitted within the diked area.

4) American Concrete Institute; 201.1R-08 Guide for Conducting a Visual Inspection of Concrete in Service.  This is not a free guide and requires purchase.

5) Steel Tank Institute: SP001 Standard for The Inspection of Aboveground Storage Tanks, 5th Edition PDF.  This is not a free guide and requires purchase.

6) VDEQ Petroleum Page / VDEQ Regulation  (See Page 17 for Secondary Containment Requirements)VDEQ Petroleum Storage Tank Compliance Manual 

ODCP Plans Worst Case Discharge: Please note that “125% of the volume” refers only to calculating the baseline volume equivalent
to the largest tank at the facility when the largest tank is one of several within a single diked area.
The reasoning is that in the worst case scenario when the largest tank fails, the force of the
product release has the potential to damage transfer piping and other tanks within the dike. This
would therefore increase the size of the spill significantly. So, in determining the worst case spill
for a multi-tank containment area the following should be used:
(Vol. of the largest tank x 1.25) x .22 (the “slosh factor”) = worst case discharge
For onshore facilities, adverse weather conditions mean ten-year, 24-hour rain event which
translates into approximately six inches of rainfall.


8) State of Ohio:  Inspection of Concrete StructuresThis is for dams but provides guidance on the structural integrity of concrete in straight forward langauge.

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