Loading...
HomeMy WebLinkAboutV(F) Approval and Authorization of $10,000 from Contingency for Retrofit of the Existing Stormwater Pond in Twin Lake Woods on Marlene Drive (Pond H3) for the Purpose of Improving Maintenance of the Pond City Manager Jim Gleason center of GOOd Lifo' at. Agenda 02-17 -2004 Item V F Commissioners Danny Howell, District 1 Scott Anderson, District 2 Rusty Johnson, District 3 Nancy J. Parker, District 4 Mayor S. Scott Vandergrift 5T AFF REPORT TO: FROM: The Honorable Mayor and City Commissioners Robert B. Zaitooni, P.E., Deputy Director Public Works/City Engineer DATE: February 17, 2004 RE: Pond H3 Retrofit, Twin Lake Woods ISSUE: Should the Honorable Mayor and the Board of City Commissioners approve $10,000.00 from the Stormwater Contingency Funds for the purchase of material to retrofit Pond H3 in Twin Lake Woods to improve the maintenance of the Pond; and authorize Public Works staff to perform the work using City equipment? BACKGROUND AND DISCUSSION: Pond H3 is located on Marlene Drive in Twin Lake Woods, east of Adair Street and south of Nicole Boulevard. It should be noted that the construction drawings for this 37-lot sub-division was approved as "Twin Lake Forest Addition" in the early 1990's and the subject pond was identified as Pond # 100. This stormwater pond is under the ownership of the local HOA, which is responsible for maintenance of the Pond. Pond H3 as designed and constructed is a "V" shape pond with steep side slopes and depths exceeding 10' from top of the bank. There is more than a foot of standing water in the pond at all times. These characteristics make normal maintenance of the pond extremely difficult with conventional equipment resulting in poor maintenance. Additionally, the standing water is indicative of the failed underdrain system, which was incorporated, in the original design of the pond. A review of original SJWMD (S1. Johns River Water Management District) drainage permit and calculations revealed that the pond was oversized in volume requirements. This finding provided an opportunity to raise the bottom of the pond substantially and reduce the slopes of the bank to 5:1 or better for ease of maintenance. This retrofit will not affect the existing incoming drainage structures into the pond, will result in a "dry-bottom" condition, and will allow abandonment of the existing underdrain system. Pond H3, Twin Lake Woods, Page 2 City of Ocoee, on be-half of the homeowners applied and has received a permit from SJRWMD to retrofit the pond. The retrofitted pond will satisfy the volume criteria while substantially improve the maintenance requirements. The cost of this retrofit is estimated at $10,000 for material with City Public Works staff performing the work using City equipment. The homeowners have agreed to provide the required maintenance after completion of the retrofit subject to regular inspections by the City. RECOMMENDATION: Staff respectfully requests the Honorable Mayor and City Commission approve $10,000.00 from the Stormwater Contingency Funds for purchase of material; and authorize Public Works staff to perform the required work using City equipment. Cc: Alex Nasser, P.E., Staff Engineer St..~Johns River Water Management District Kirby B. Green III, Executive Director' David W Fisk, Assistant Executive Director David Dewey, Altamonte Springs Service Center Director 975 Keller Road · Altamonte Springs, FL 32714-1618 · (407) 659-4800 December 8, 2003 Mr. Alex Z. Nasser, P.E. City of Ocoee 150 N. Lakeshore Drive Ocoee, FL 34761 Re: Permit Modification Request, Twin Lakes Forest Permit Number 42-095-45521-1 Dear Mr. Nasser: The District received your request for permit modification by letter on December 1,2003. I understand the modification to be a modification of pond 100. Pond 100 was designed to exceed District rules for retention volume. This additional capacity was obtained by excavating the pond deeper than required to meet District rules. Since construction the HOA has encountered difficulty maintaining the pond due to steep side slopes and occasional wet pond bottom conditions. To correct this problem the City proposes to regrade the pond to make the sidebanks shallower and bring the pond bottom up above the seasonal high ground water elevation. Plans and calculations provided indicate that the pond will continue to meet District criteria upon completion of the proposed reconfiguration. To retlect the proposed modification, the terms and conditions of the permit :Ire modified as follows: The Pond 100 shall be constructed in accordance with the plans received by the District on December 1, 2003. All other terms and conditions of permit number 42-095-45521-1 will remain in effect, except as modified by the above condition. Please be advised the District has not published a notice in the newspaper to advise the public that it is issuing this letter modification. If you do not publish a notice in the newspaper, a party's right to challenge the issuance of this letter modification extends for an indefinite period of time. If you wish to have certainty that the period for filing such a challenge is closed, then you may publish, at your own expense, such a notice in a newspaper of general circulation within the area that includes the project to which the modificarion applies. A copy of the form of the notice is attached for yuur use. cc: PDS - Leller Modificati( 11 William Carlie GOVERNING BOARD Duane OUenstroer, CHAIRMAN JACKSONVILLE Ometrias D Long. VICE CHAIRMAN AmPKA R Clay Albright, SECRETARY OCALA David G. Graham, TREASURER . JACKSONVILLE W Michael Branch FERNANDINA BEACH John G. Sowinski ORLANDO William Kerr MELBOURNE BEACH Ann T. Moore BUNNELL City Manager ,Jim G lea~on Commi~sionprs Danny Howell, District 1 Scott Anderson, District 2 Husty <Johnson, District 3 Nancy ,1. Parker, District 4 Mayor S. Scott Vandergrift November 24, 2003 Mr. William E. Carlie, Jr., Compliance Manager St. Johns River Water Management District 975 Keller Road Altamonte Springs FL 32714 Subject: Twin Lakes Forest Retrofit Dear Mr. Carlie: As we discussed in our meeting with you on Monday, October 20, 2003, we are submitting our design modification for Pond 100 for the above referenced project. The purpose of this submittal is to modify the side slopes of Pond 100, which are presently (2: 1) horizontal:vertical, which is making it very difficult to perform the routine maintenance such as mowing the grass within the side slopes. Also, due to the fact that the pond has been oversized in design (11 feet deep) and that the underdrain system is not functioning properly, we are proposing to fill 6 feet into its bottom and keeping 5 feet of depth with side slopes of (5: 1) horizontal: vertical. The overt1ow weir will be installed one foot below the pond top elevation providing water quality treatment and keeping one foot of free board. (see attached calculations) Storm water recovery will occur in less than one day and we used the previously submitted soils report for this purpose. Due to the fact that less than 50% of the project area is impervious, we were not required to analyze and submit the calculations of the mean annual storm event. We hope that this design will resolve the maintenance issue of this project with satisfying the requirements of the District. If you have any questions or comments about this project, please contact our office. Sincerely yours, olu. ~ Alex Z. Nasser, P.E. Staff Engineer Util iti es/Engineering City ofOco~~' ISO N Lak~shor~ Drive' Oco~e, Florida 34761 Phon~: (407) ,)OS-3100' Fax: (407) 6S6-8S04' www.ci.oco~~.tI.us Twin Lakes Forest Basin 100 Location: The site is located on the east side of Adair Street, about 500 feet south of Nicole Boulevard. Narrative: This single family subdivision was built in the early 1990's. Pond 100 was designed as a dry retention pond with underdrains for storm water recovery. This pond was constructed with steep side slopes which are steeper than 3: 1 (horizontal:vertical) making it very difficult to maintain the pond with normal conventional equipment. In addition, by reviewing the permitted file with and the calculations, we found that the pond was oversized in volume. The existing pond is in excess of 100 feet deep, with more than a foot of standing water at it's narrow bottom, which may be interpreted that the existing underdrain system is not functioning properly. Therefore, with all these facts in hand, we are proposing to modify this pond by filling six feet into its bottom, and that will keep it five feet deep and maintaining the required water quality treatment volume. By raising the pond bottom six feet, there will be no need for the underdrains. Additionally, the underdrain system will be out of use with the fact that the pond bottom will be raise 6 feet. Design criteria: As agreed with Mr. William Carlie, Jr., Compliance Manager with the SJRWMD, this project is a stormwater short form. Since the impervious area is less than 50%, the mean annual storm analysis is not required. The previous calculations required one-half inch of runoff over the basin area, but with this modification we will provide one full inch of runoff over the basin area meeting the new criteria of the SJRWMD and the City of Ocoee criteria. We will install a Type 'c' Inlet at the 8" outfall pipe location. The top of the inlet will act as an overflow weir on top of the water quality volume elevation. One of the inflow pipes, from 1-10 to EW-ll (Sheet 4 of 9) will be abandoned because of its very low depth. A shallower inflow pipe will replace the existing. See the pond plan sheet for details and elevations. The other inflow pipe, from DM-6 to EW-12 will remain undisturbed. However, a manhole will be installed at terminus of the pipe, and runoff will bubble up into the manhole then into a pipe out of the manhole into the pond. 1161.31 5' DRAINAGE EASEMENT NOTE SOD OUTFALL F - GATE Z. -{J' SW/Wt(TYPJ I~V 14-4-0 8" OUTFALL CONTROL PIPE (SEE DETAIL SHEET 6) UNDERDRAIN OUTFALL PIPE \. '. \ \ 1_ ~. \ \ \ . , '. \ \ ,.\\ '.\\ \ '\ \\\ \ \ '< " ,\ \ \ . . ,\ \ \ \ ~ ,\ ". '\ \'- . \ " \ \ \ \ \ \ \ \ \ \ , , ~ . \, \\ \\,\ \ \\ \' 256 UD 6 @ INV 144.50 :'<, 'ir' It' t 29 EW-19 / U- TYPE ENDWALL / INV 144-0 I '- ~"--~ --- / ./>. ....--'- v-,- ......4."'"' @)' 162.5 t 10 1164.6.1 ~ , ~180 """"'- I I I I :/ 165.3 I f I I 1.-, I I I 1166. t 27 Calculations: Basin 100 area = 8.12 acres Pollution abatement volume = 1" X Basin area Xl' /12" = 1 X 8.12/12 = 0.68 ac-ft = 29476 ft^3 req'd Staee (ft) Area (ft^2) Storaee (ft^3) 153.5 3,565 0 156.0 9,920 16,856 157.5 13,900 34,721 provided 158.5 16,553 49,947 Set the overflow weir @ 157.5', using type 'c' inlet with the top of inlet as the overflow. The existing 8" overflow DIP will be inserted into a hole that will be drilled into the 'c' inlet to be the overflow pipe. According to the soils report submitted to the SJRWMD on September 13, 1991, Page 2 states that "for purposes of this seepage analysis, the coefficient of horizontal permeability was conservatively assumed to be equal to the coefficient of vertical permeability at 10 feet per day. Therefore, with a maximum stormwater depth of 4 feet in the new designed pond, the recovery will occur in less than 24 hours. I 5: B . S ' '-.......---..... 157.5' J /55.5 14'7.51 r- L---- ...A.) .I J;\ {U U () . I D".c" fo.. ; f s '-O'U.~ - PovuJ top c:-/~u.>. t;ov-. w ...r "- r 'l';;;"7f t '( v". 14 /A.1 ~ _.__ _.u_~,_.____. .._... ~- ..._.~. ~-,_..., .. ,... --_._.._-~,.._._~.~. F O"".J ho tt",,,,,-\ &:~t;~ZJ SHWT C2:) ~ / / // //(1 r-- /. 5 / ./ ;0. T, S. o Ji",- (( <; tr '^ <.IU/UL- ! To P = /57.5_______ I I Ty fe. C r ~/et -r I' , , , Of CI { 111. ~ 3 X 2.. 1/ ~ . · t'Vt.@.8 PVL- /0 hi""'llllll'" eXI; I 0 N.T,S I ',-- IL1v. 150. 53 ._--~- 1 J t\ II( (t t~\ I I (l ;, I i 4- ' j", I}/ t" 1 1/ \ 1 / , 'II "" ".) .-'. ..., \..... ,-" "",,,'/ (G'xist/..':) fif~ tu be:. '" b~CJ'l1,,-j) o Fe-Y\ ct.-JCq,J i ..tsTcJ.1 ~ "",^~...Jo~ ~Qt{( fift'.. A bOoo4Jdlf ti'-L. ~X i di") _.___n . 1/ 'I , 1\'"' {53.5,-,' i / / Co Vlst. I s->),.j~// f;fe WI 1"1 A1c:s I, "'. '\ f,i , ,I / . t l." /S6.01 I 5'"/; (' , ,/ I 1120 1]/100 16/ S'., '( 0.:'.0 ~O;S ,,( >f,;... / . '[I' .... l ~, ../ , r ~ l+ v <..\ I.' I ~.~. l.'. P"'" , L . P A \) .- t I{ ~.' f) : I " .,1:, ; I , , "] (j. Go, ('" . If:= "- 0; ) -4 7 6 (?r..f s",J) . ?l~~fo ;eJ) ,\ v\ (\;[,l( . '?J vL-- , 11 .-'1 f .; .; , i..l~ I .; ~)J~l/~ ..../ ....~i [)~ j .... ;.- \ \ ".~". ' .' -/-.;; "._-1' ./"1 .- .~..~" ",..' "," J ,.' -< /' -......\..... .; ,. {) ~\. ~. -\. t---- 0~, \. . .J' ~ ~ . I . '1 \ ' '\\, \ \ , \ \ \ \ " 0." " _j r C.; ,.... l I \ I I l l f V\ /~ i.l '. ::- I Vt S 1~ If 0.. M""", ko Ie. (b LA..bble - (Y) w /tl--. 01. I 5 I' ./;tl'.... / [' F;P <. ( ") ,-. Ct.,) If, II I I-f h, t.l (( l~ Fe c.}\, ~ \ '< '. '\ \\ " '. 'j \, \ \ . \ \ . \ ., ..... ..~~~>~~.<> \::l ......,.,~_.~~1i3-. /'SIV' '. ~ -Ya. " /. . '" 'I "~ ~ 10,"-__..... "'--., ., "~ ; .' ~/' ... I LA I --4.;( J', -- ~;:;, I ~ '- I" ^- ::: \J I :,..' ,/ ,/ _f?l , \ " '\ (tf ) o /b, 8', L ]4,72/ q q / 'l ~i / ,; I ('-4 ! f ~-J ( '0. (,/ 1;1/1 ~l~: i 1\.\ '. (" I Ji ,( l,L c:, 1 j l ( I I ! . I,...