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FW PUrvis Subdivision CommentsIPM.Note FW: PUrvis Subdivision Comments FW: Roberta Allen EX /O=CITYOFYELM/OU=FIRST ADMINISTRATIVE GROUP/CN=RECIPIENTS/CN=R_ALLEN PUrvis Subdivision Comments Roberta Allen EX /O=CITYOFYELM/OU=FIRST ADMINISTRATIVE GROUP/CN=RECIPIENTS/CN=R_ALLEN Tami Merriman PUrvis Subdivision Comments 00000002SERVER1/o=CITYOFYELM/ou=first administrative group/cn=Recipients/cn=r_allenMicrosoft Exchange Server 00000002SERVER1/o=CITYOFYELM/ou=first administrative group/cn=Recipients/cn=r_allenMicrosoft Exchange Server T, FYI R -----Original Message----- From: Edward A. Wiltsie [mailto:eawiltsie@wildblue.net] Sent: Wednesday, December 19, 2007 12:45 PM To: Roberta Allen; ed@eawiltsie.com; ed@jwmaeng.com Subject: PUrvis Subdivision Comments Please forward to Tammy Merriman. Thank you, E A Wiltsie <DC90029353CCCD468AA2A2858FFCD8F501EAE0@server1.ci.yelm.wa.us> FW%3A PUrvis Subdivision Comments.EML Roberta Allen Roberta Allen 00000002SERVER1/o=CITYOFYELM/ou=first administrative group/cn=Recipients/cn=r_allen Microsoft Exchange Server PurvisSubComments19Dec07a PurvisSubComments19Dec07a 11.0 Tami Merriman EX /O=CITYOFYELM/OU=FIRST ADMINISTRATIVE GROUP/CN=RECIPIENTS/CN=Tami tamim@ci.yelm.wa.us tamim 458-8496 Community Development Tami Merriman Tami Merriman tami PurvisSubComments19Dec07a.doc Edward A. Wiltsie PO Box 6102 Olympia, Washington 98507 19 December 2007 City of Yelm PO Box Yelm, Washington 98597 ATTENTION: Ms. Tammy Merriman, Community Development Department SUBJECT: Purvis Residential Development – 50 Acres/160 Residential Lots Dear Ms. Merriman: Pursuant to the City’s Public Notice for the above referenced project, I submit the following comments: OVERVIEW The Public Notice indicates that the application is for a 50 acre parcel to be developed to include 160 residential lots. The design information provided with the application addresses only 24 residential lots. The application and public record should be amended to reflect that the application is for Phase 1 of the Purvis Development and only for 24 lots on 5.36 acres. TRAFFIC Recent Public Hearings and Hearings Examiner’s finding for the Tahoma Terra Subdivision – Divisions 5 & 6, Berry Valley Development and Wyndstone developments were required to provide a combined regional traffic analysis for Yelm Avenue,Tahoma Boulevard, Berry Valley Road, Longmire Street and Cullen Road. The combined analyses showed a number of these public rights of way to be operating in excess of their design capacity. The addition of this development will add traffic to this condition increasing the overload condition. Hence, new regional traffic mitigation will be required along numerous of the routes. Please provide me with copies of the traffic studies that address these issues on a regional basis. WATER SUPPLY WSDOE records indicate that the City of Yelm does not own the required Water Rights to justify entertaining additional residential development at this time. Application for this development should be placed on hold until the Water Rights required by Washington State Law have been procured and perfected in the name of the City of Yelm. STORMWATER There are numerous disconnects between the Stormwater Report and its incorporated Soil Investigation Report, and ongoing Thurston County Stormwater/Thompson Studies. The report and analyses performed do not mention or coordinate with the ongoing Thurston County/City of Yelm Flood /Study being performed along Thompson Creek from its headwaters south of the Tahoma Terra Subdivision and 93rd Avenue and on to SR-510 to the north. The site drainage report by KPFF lists three different site acreages for the Phase 1 development, 5.56 acres, 6.0 acres, 6.43 acres, and 8.49 acres in the same drainage report without explanations for the differences. At one point reference is made to 1.07 acres of wetland area, which fits the difference between the 5.56 and 6.43 acres. The Public Notice does not reference any of these Phase 1 acreages, only the 50 acre total parcel size. The Application, Notice of Application and Storm Reports should be revised and reissued to facilitate Public Review of documents that are internally consistent and facilitate the review of accurate and representative design documents. Section 3 of the stormwater report states that “Groundwater was not discovered in any test pits on the Phase 1 site.” The incorporated Soil Investigation Report states on page 2 that groundwater and evidence of seasonal groundwater was encountered in test holes A, B, C, F & I. It is difficult to determine precisely from the mapping provided, but test hole F is definitely within the Phase 1 area and test holes A, B and C may be within the Phase 1 area. The report and designs represented need to be corrected to reflect these conditions and site conditions consistently and accurately. The revised documents should be reissued for public review of accurate and representative design documents. Stormwater analyses presented in the Drainage Report use the smallest of the site acreages listed for the site 5.36 acres. This value may not represent all of the land area impacted by the development. The report should be modified to clarify this issue and provide a clear technical audit trail for all land areas involved. The Drainage Report discusses both storm pond release by sidewall infiltration and controlled release to surface flow. 1992 WSDOE Stormwater Manual requirements for infiltration in areas restricted by shallow groundwater or impervious surfaces (Darcy’s Equation Analysis) are not presented to support this approach and infiltration values are not presented either in the Soil Report or Drainage Report. The controlled release analyses use an 8.49 acre tributary are to calculate the undisturbed release rates, while the post-development tributary area flow contributions are calculated using a 5.36 acre area. If a portion of the predevelopment site is to remain undisturbed, it can not be used in calculating the post-development release rates. In short, if 5.36 acres are being developed, facilities release rates must be calculated using 5.36 acres. Hence, the release rates listed in the Drainage Report are overly optimistic and are not in accordance with the procedures established in the 1992 WSDOE Manual. Finally, the 1992 WSDOE Manual requires that the downstream flow path and environment be analyzed for facilities that release flow to the surface. This project area is tributary to Thompson Creek, which has experienced severe flooding during the 2005/06 and 2006/07 wet season during storms that were far below the City of Yelm design events rainfall levels (see Figure below). As a result of this recent flooding, Thurston County in conjunction with the City of Yelm is in the process of monitoring and studying Thompson Creek from its headwaters (south of Tahoma Terra) to SR-510. This study and the potential downstream impacts of this development in a proven sensitive watershed and creek reach has not been addressed in this report. The proposed design will alter the transit time for surface and shallow groundwater to Thompson Creek, changing the local hydrology in a basin where jurisdictional efforts are being expended to define and preserve the existing and natural hydrology. It is further noted that there is a potential for the storm pond to release to the west into an existing wetland. If this is the case, the 1992 WSDOE Manual requires that the hydroperiod of the wetland be studied and defined prior to stormwater release into the wetland and designs, calculations and additional mitigation be provided to insure that the natural hydroperiod of the wetland is not disturbed or modified. Based on the foregoing, the documents submitted do not appear to be accurate, complete, internally consistent or inaccordance with the 1992 WSDOE Stormwater Manual. As such, the subject documents should be returned to the developer for revision so that a review of accurate, consistent, representative and compliant (with City of Yelm Code and the 1992 WSDOE Manual) can be reviewed as part of the Public Comment process. To this end I request that revised application and Public Notice documents be prepared along with the support document revisions be developed and reissued. Should you have any questions of required additional information, please contact me at ed@eawiltsie.com. Yours truly, E A Wiltsie .doc PurvisSubComments19Dec07a.doc PurvisSubComments19Dec07a.doc application/msword attachment PurvisSubComments19Dec07a.doc Edward A. Wiltsie PO Box 6102 Olympia, Washington 98507 19 December 2007 City of Yelm PO Box Yelm, Washington 98597 ATTENTION: Ms. Tammy Merriman, Community Development Department SUBJECT: Purvis Residential Development – 50 Acres/160 Residential Lots Dear Ms. Merriman: Pursuant to the City’s Public Notice for the above referenced project, I submit the following comments: OVERVIEW The Public Notice indicates that the application is for a 50 acre parcel to be developed to include 160 residential lots. The design information provided with the application addresses only 24 residential lots. The application and public record should be amended to reflect that the application is for Phase 1 of the Purvis Development and only for 24 lots on 5.36 acres. TRAFFIC Recent Public Hearings and Hearings Examiner’s finding for the Tahoma Terra Subdivision – Divisions 5 & 6, Berry Valley Development and Wyndstone developments were required to provide a combined regional traffic analysis for Yelm Avenue,Tahoma Boulevard, Berry Valley Road, Longmire Street and Cullen Road. The combined analyses showed a number of these public rights of way to be operating in excess of their design capacity. The addition of this development will add traffic to this condition increasing the overload condition. Hence, new regional traffic mitigation will be required along numerous of the routes. Please provide me with copies of the traffic studies that address these issues on a regional basis. WATER SUPPLY WSDOE records indicate that the City of Yelm does not own the required Water Rights to justify entertaining additional residential development at this time. Application for this development should be placed on hold until the Water Rights required by Washington State Law have been procured and perfected in the name of the City of Yelm. STORMWATER There are numerous disconnects between the Stormwater Report and its incorporated Soil Investigation Report, and ongoing Thurston County Stormwater/Thompson Studies. The report and analyses performed do not mention or coordinate with the ongoing Thurston County/City of Yelm Flood /Study being performed along Thompson Creek from its headwaters south of the Tahoma Terra Subdivision and 93rd Avenue and on to SR-510 to the north. The site drainage report by KPFF lists three different site acreages for the Phase 1 development, 5.56 acres, 6.0 acres, 6.43 acres, and 8.49 acres in the same drainage report without explanations for the differences. At one point reference is made to 1.07 acres of wetland area, which fits the difference between the 5.56 and 6.43 acres. The Public Notice does not reference any of these Phase 1 acreages, only the 50 acre total parcel size. The Application, Notice of Application and Storm Reports should be revised and reissued to facilitate Public Review of documents that are internally consistent and facilitate the review of accurate and representative design documents. Section 3 of the stormwater report states that “Groundwater was not discovered in any test pits on the Phase 1 site.” The incorporated Soil Investigation Report states on page 2 that groundwater and evidence of seasonal groundwater was encountered in test holes A, B, C, F & I. It is difficult to determine precisely from the mapping provided, but test hole F is definitely within the Phase 1 area and test holes A, B and C may be within the Phase 1 area. The report and designs represented need to be corrected to reflect these conditions and site conditions consistently and accurately. The revised documents should be reissued for public review of accurate and representative design documents. Stormwater analyses presented in the Drainage Report use the smallest of the site acreages listed for the site 5.36 acres. This value may not represent all of the land area impacted by the development. The report should be modified to clarify this issue and provide a clear technical audit trail for all land areas involved. The Drainage Report discusses both storm pond release by sidewall infiltration and controlled release to surface flow. 1992 WSDOE Stormwater Manual requirements for infiltration in areas restricted by shallow groundwater or impervious surfaces (Darcy’s Equation Analysis) are not presented to support this approach and infiltration values are not presented either in the Soil Report or Drainage Report. The controlled release analyses use an 8.49 acre tributary are to calculate the undisturbed release rates, while the post-development tributary area flow contributions are calculated using a 5.36 acre area. If a portion of the predevelopment site is to remain undisturbed, it can not be used in calculating the post-development release rates. In short, if 5.36 acres are being developed, facilities release rates must be calculated using 5.36 acres. Hence, the release rates listed in the Drainage Report are overly optimistic and are not in accordance with the procedures established in the 1992 WSDOE Manual. Finally, the 1992 WSDOE Manual requires that the downstream flow path and environment be analyzed for facilities that release flow to the surface. This project area is tributary to Thompson Creek, which has experienced severe flooding during the 2005/06 and 2006/07 wet season during storms that were far below the City of Yelm design events rainfall levels (see Figure below). As a result of this recent flooding, Thurston County in conjunction with the City of Yelm is in the process of monitoring and studying Thompson Creek from its headwaters (south of Tahoma Terra) to SR-510. This study and the potential downstream impacts of this development in a proven sensitive watershed and creek reach has not been addressed in this report. The proposed design will alter the transit time for surface and shallow groundwater to Thompson Creek, changing the local hydrology in a basin where jurisdictional efforts are being expended to define and preserve the existing and natural hydrology. It is further noted that there is a potential for the storm pond to release to the west into an existing wetland. If this is the case, the 1992 WSDOE Manual requires that the hydroperiod of the wetland be studied and defined prior to stormwater release into the wetland and designs, calculations and additional mitigation be provided to insure that the natural hydroperiod of the wetland is not disturbed or modified. Based on the foregoing, the documents submitted do not appear to be accurate, complete, internally consistent or inaccordance with the 1992 WSDOE Stormwater Manual. As such, the subject documents should be returned to the developer for revision so that a review of accurate, consistent, representative and compliant (with City of Yelm Code and the 1992 WSDOE Manual) can be reviewed as part of the Public Comment process. To this end I request that revised application and Public Notice documents be prepared along with the support document revisions be developed and reissued. Should you have any questions of required additional information, please contact me at ed@eawiltsie.com. Yours truly, E A Wiltsie .doc PurvisSubComments19Dec07a.doc PurvisSubComments19Dec07a.doc application/msword attachment