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NELSON ENGINEERS �{ 9' 27
19911 4CT I C
822 7TH STREET GREELEY, COLORADO 80631 (303) 356-6362 CLERK
Tp THE B°t-'1-5"5
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October 3, 1994
Mr. Jeff Stoll
Weld County Health Department
1517 16th Avenue Court
Greeley, CO 80631
Dear Jeff,
Mr. and Mrs. Pittock, the owners of Pine Lake Village, have asked me to assist them in
obtaining the necessary permits to allow them to enlarge their mobile home park. I made an
inspection of the site and found there is ample land area available to accommodate several
additional living units and that the existing evapotranspiration (e.t.) beds are underused. In
fact, only about one half of the existing beds are currently being used and the owners cannot
keep sufficient vegetative growth on the beds with current waste flows. Thus the system
cannot function optimally because of the low discharge rate.
You may recall that the original e.t. beds were designed using estimates and published criteria,
all of which has substantial safety factors built in. It is obvious that such criteria has resulted
in excessive e.t. bed capacity. That original design rate was as follows:
1. 3.5 persons per mobile home (per unit)
2. A waste flow of 75 gallons per capita per day(gpcd)
3. A 1.5 factor for added safety
4. A lake evaporation factor of 40 inches per year
The existing facility has been in operation for more than three years. The park has been
operated and maintained very well such that its operation and population has stabilized.
Measuring of the waste flow can now be accomplished and relied upon for dependable results
and design criteria. The owners installed a 90° v-notch weir in the effluent pipe from the
septic tank and recorded flows at various times. I inspected the flow metering installation and
confirmed flow readings on two occasions. We found that the flow rates averaged 3.1 gallons
per minute (gpm) from readings taken during the period of June 15, 1994 to June 26, 1994
and at different times during the day. The 3.1 gpm converts to 4,464 gallons per day (gpd).
All of the 34 units are occupied with a total population of 89. That population then
contributes 4,464/89 or 50.1 gpcd to the waste stream on an average measured basis.
Published criteria require that the design flow rate (Q) shall be equal to 150% of the average
measured flow. As a result, Q is equal to 4464 x 1.5 or 6,696 gpd. The e.t. bed area required
r ,� for the existing units is:
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Jeff Stoll -2- October 03, 1994
Q x 237/40(1)
6696 x 237/40 = 39,674 s.f
As a result, the e.t. bed area required for each living unit in the park is 39,674/34 = 1,167
s.f./unit. The existing e.t. bed area is 42,000 s.f with space and piping arrangements in place
to expand the facility by an additional area of 21,000 s.f for a total area at ultimate
development of 63,000 s.f As stated earlier, the physical evidence shows that only about one
half of the existing bed area is being used effectively.
Based on current and measured waste flows and the required 50% increase in design rates, the
existing e.t. bed area can effectively accommodate 36 living units of comparable dwellings:
(42,000 s.f / 1167 s.f./unit= 36 units)
Thus the existing e.t. beds have a capacity for 36-34 (existing units) or 2 additional units on
the site.
If the allotted area for 2 more beds is constructed, then 21,000 s.f. can be added thus
providing space for 18 more units (21,000 s.f. / 1,167 = 18 units) for a total of 36 + 18 or 54
units. The daily flow rate for design purpose is 10,635 gpd for 54 units.
The existing septic tank has a capacity of 2,240 cubic feet. The design flow rate for 54 units
of 10,635 gpd requires a volume of(10,635 x 30) /(24 x 7.48) or 1,777 cubic feet for the
required 30 hour retention. The volume of the existing septic tank exceeds the design
capacity (2240 > 1777).
In this case, the request is to add 20 units to the park so that the e.t. bed area can be more
nearly utilized. Please provide an outline of the procedure for obtaining the necessary permits
and approvals to permit development of 20 additional units at the Pine Lake site. Mr. and
Mrs. Pittock are aware that sewage disposal is an essential part of any expansion of the park
and they believe, as I do, that necessity can be satisfied. We believe that space requirements
and the need for access, public water, and other utilities can readily be satisfied. The Pittocks
also know that there is a very strong need for affordable housing in their vicinity. With this
requested expansion, some of that need can be satisfied.
(1)Annual Free Water Surface Evaporation according to Weld County "Individual Sewage
Disposal System Regulations"
941298
Jeff Stoll -3- October 03, 1994
We will be pleased to meet with you, or others as designated, at the earliest possible time to
define a plan for expansion of Pine Lake Village. Please contact me at your earliest
convenience.
Respectfully,
NELSON ENGINEERS
poxiitgeau__
LaVern C. Nelson, P.E.
LCN/jd
pc: Chuck Cunliffe, Director of Planning Services, Weld County, Colorado
William Webster, Chairman, Board of County Commissioners, Weld County, Colorado
Charles and Esther Pittock
941218
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