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HomeMy WebLinkAboutStormwater Site Plan Review for COM2004-00120 - COM Engineering / Geo-Tech Reports - 6/30/2004 �,3 c/ y° .STA�F° MASON COUNTY o s u = PUBLIC WORKS DIRECTOR/COUNTY ROAD ENGINEER Y ON Y Shelton,Washington 98584 r2 y O 1864 DATE: July 13t', 2004 INTER-DEPARTMENTAL COMMUNICATIONS TO: Rick Mraz, DCD - Planner FROM: Alan A. Tahja, P/W - Co. Hydr. Engr. WO#PLG-04 SUBJ: Stormwater Site Plan Review NAME: Eger Commercial Site—Belfair COM2004-00120 A plan sheet (site plan) developed to accompany the "Storm Drainage Analysis Report"prepared by Michael Wnek, P.E., for the proposed Richard Eger commercial site in Belfair has been received and reviewed by Public Works. The plan provides adequate details to show how stormwater runoff will be either routed around/through the site, or how runoff generated from the site will be collected, treated, and disposed of/infiltrated. Though Ecology guidance recommends pond side slopes should not exceed a 3:1 (H:V) configuration, the 2:1 slopes promoted in the current design can be accepted,mainly because of the shallow depth of impounded water(less than 2' deep). An Operation and Maintenance (O&M) Covenant needs to be created, recorded, and a copy delivered to Public Works for monitoring and administration. The project engineer has provided a vicinity map of the Belfair area showing the approximate location of the project. As shown on the submitted map, the project is shown located in section 29. The property's parcel number informs me that this property is in section 28. The engineer has indicated on his plan sheet that the project is located in Section 23, Township 28. In summary, the drainage report submitted for the proposed property development may be considered acceptable. Public Works requests we be notified when the stormwater features have been completed so that they may be inspected for conformity with the plans. Please feel free to contact me at County extension 461 if you have any questions regarding these comments, or if you feel any features need further discussion or attention. Si cerely, � Z A tan A. Tahj File: H:\WP\GEO\Reviews\Eger-2.doc WORK ORDER - PUBLIC WORKS DEPT. (a) Date: 7_ 13 _p 2-1 (p Work Order PERMIT#: �p�? Z�p� _�1z© Number. —p Requested by: r'i� L2 Authorized by: Date: TYPe of Work: tz�✓w�cJ �Pt1r� CHARGE TO: NAME AGENCY/COMPANY BILLING ADDRESS PHONE �B) Pub Works Pelson In Charge: (c) Project Time Line. (from -to dates) TO Prcjen,4 Stut date: ? EsBmated FhM Date: Appro*rate hours: ESTIMATED TOTAL$'S: 7C:7��4 -{- COST ESTIMATE (D) 2AIS ��Y* Lags Hours subtotal Frinae% TOTAL$ r EQUIPMENT USED: TOTAL$1 MATERIAL USED: :eee�ae?:e%....:.v./.�7:eG.w.e,,,.w>?%ia....... ...::...:..... ....n:;:-,.,....:...�........., . ,..h..:•Ytc'✓.F(v�S. +.fi•�t-,r..�cwr .'.�.a�`rY. vY,..�,+, .,:.o:.�,�,.a,a:�.'G ..CS.. �: A::;r.;:�)��f (F) Actual Cost $ BARS: PROD#-. DATE EnV4oyee NNM t Rate Hours $ubtow Erlp�n% TOTAL$ EQUIPMENT USED: Date Unit at OT MATERIAL USED: TOTAL ALL (G) BILLED DATE INV f PAID DATE REC.M CKO E ev- PEON STA TF O� M C '�L u A U �N s N NT MASON COUNTY 2' r27 Y PUBLIC WORKS DIRECTOR/COUNTY ROAD ENGINEER JJ ?864 Shelton,Washington 985" DATE: June 301h, 2004 INTER-DEPARTMENTAL COMMUNICATIONS TO: Rick Mraz, DCD -Planner FROM: Alan A. Tahja, P/W - Co. Hydr. Engr. WO# PLG-04 SUBJ: Stormwater Site Plan Review NAME: Eager Commercial Site-Belfair F-PA2964-986+0 400f ayel—Gb 1 Z O Rick, The"Storm Drainage Report"prepared by Michael Wnek, P.E., for the proposed Richard Eager commercial site in Belfair has been received and reviewed by Public Works. Conceptually,the engineer proposes to infiltrate the stormwater runoff generated from a proposed building area(6000 S.F.) and outside parking/drive area with a combined area of approximately 0.329 acres. The entire parcel size is reported as 3.7 acres. The concept of infiltrating stormwater runoff at this site has been discussed with Bill Tabor,the County Engineer. Other properties in the Belfair area have been required to detain and release stormwater runoff at prescribed rates. Detention has been required because of reports of high groundwater levels being realized at the properties bordering the Roy Boad Road near its intersection with Clifton Lane. The Eager site is located approximately a quarter mile north and east of the problem area, and is at an elevation roughly equal to the problem area, so it appears highly unlikely that infiltration of surface water at the Eager site will impact any of the properties at the southwesterly Y end of the Roy Boad Road. Except for accepting the concept of infiltrating stormwater runoff at this site,the drainage plan, as presented is lacking information and details necessary for it to be considered complete and acceptable. The engineer has calculated flow rates for storm events, and sized a retention pond based on assumed infiltration rates, and what I assume to be an assumed vertical separation of 10 ft between the bottom of the infiltration bed and the water table/bedrock. Ecology's Technical Manual prescribes methods for establishing infiltration rates which include soil exploration and reporting. No information supporting the claimed soil infiltration ability,other then a general soil description,has been provided. My personal observations in past years have witnessed this property to be submerged with stormwater runoff during heavy rain events. A soil investigation and report should be prepared to confirm or dismiss groundwater tables during the wet season, and to confirm the soils' ability to infiltrate stormwater runoff as claimed in the drainage report. File: H: \WP\GEO\Reviews\Eager.doc Stormwater Site Plans prepared to Ecology standards are expected to include upstream and down stream analysis. The site plan submitted for the project does not show the full extent of the subject property, discharges to the subject property from State Route 3, conveyance routes for bypassed waters,proposed pond locations or swale locations, and other details. The site plan indicates an impervious area of 0.33 acres,but does not explain how this surface(8351 SF parking area) is different from the surrounding"unlabeled"areas. It may be proposed to be a paved surface surrounded by a fence, or it may be a gravel area within a gravel area, in which case,the claimed impervious area may be understated. Once an acceptable plan is developed for the proposed property development, an Operation and Maintenance (O&M)Covenant for the property will be required to be created,recorded, and a copy delivered to Public Works for monitoring and administration. The project engineer has provided a vicinity map of the Belfair area showing the approximate location of the project. As shown on the submitted map,the project is shown located in section 29. The property's parcel number informs me that this property is in section 28. The engineer has indicated the project property at the approximate location of the Safeway Store in Belfair,when the actual location is an eighth to a quarter mile northeast of the location indicated on the vicinity map. In summary, the drainage report submitted for the proposed property development should be returned to the applicant and additional information requested. Please feel free to contact me at County extension 461 if you have any questions regarding these comments, or if you feel any features need further discussion or attention. Si erely, Afl- 1A A. Tahja File: H: \WP\GEO\Reviews\Eager.doc w w vKUtK - PUBLIC WORKS DEPT. (N Date: d a y � ' PERMIT M - `y-�a�� (E) Work Order ~� rVku�thorized by-.P4lz�3�S(o �'1aZ Number: f by.- _ 'y f rYPe of Work: e,M,e Date: LU j CHARGE TO: Ns LU 00 a ,.` NAME LLI AGENCY/COMPANY 9 BILUNG ADDRESS z PHONE Pub. Works Person 1n Cha e: Project Time Line: (from—.—to dates) : ,.YXX Project sari date: —Q� Estee TO Date: Apavftate hours: ESTIMATED TOTAL VS: 7,6 M) pill s COST ESTIMATE �D TOTAL$ EQUIPMErT USED: BAM MAUMAL USEQ: (F) actual Cost � GATE ERV40yee eARS: PROD N; 14"Mfloun TOTAL= ------------ EQUIPMENT'USED: l�14 Scat( gam T Y i sx MATERIAL USED: (a) BILLED,DATE TOTAL ALL --- '—"--------I�t` PAID DATE ------- REC.Q,,,_``CK# G �